[llvm] [Reassociate] Distribute multiply over add to enable factorization (PR #178201)
via llvm-commits
llvm-commits at lists.llvm.org
Wed May 6 08:31:15 PDT 2026
https://github.com/hazarathayya updated https://github.com/llvm/llvm-project/pull/178201
>From dd763a23f606eb8c760a88bd013b704da68415e8 Mon Sep 17 00:00:00 2001
From: hazarathayya <hazarathayyayallanki at gmail.com>
Date: Tue, 28 Apr 2026 10:25:24 -0700
Subject: [PATCH 1/5] [Reassociate] Refine (X+Y)*C distribution with
PatternMatch and profitability checks
This patch adds distribution of (A+B)*C -> A*C + B*C to enable further factorization.
Key changes:
- Adopted PatternMatch for cleaner matching of (A +/- B) * C.
- Added hasOneUse() and Add/Sub parent checks for profitability.
- Modified FactorOccurrences tie-breaker to prefer Variables over Constants, preventing factorization from undoing the distribution and causing an infinite loop.
- Queues the parent instruction in RedoInsts to ensure proper linearization order.
---
llvm/lib/Transforms/Scalar/Reassociate.cpp | 86 +++++++++-
.../Reassociate/reassociate-distribute.ll | 154 ++++++++++++++++++
2 files changed, 237 insertions(+), 3 deletions(-)
create mode 100644 llvm/test/Transforms/Reassociate/reassociate-distribute.ll
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index ea6c394740f22..989387d704923 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -963,6 +963,68 @@ static BinaryOperator *convertOrWithNoCommonBitsToAdd(Instruction *Or) {
return New;
}
+/// Return true if Mul is of the form (X+Y)*C or (X-Y)*C where C is a
+/// constant, and there exists a sibling instruction of the form X*C' or Y*C'
+/// in the same expression — indicating that distribution followed by
+/// factoring will reduce the instruction count.
+static bool ShouldBreakUpDistribution(Instruction *Mul) {
+ Value *A, *B;
+ if (!match(Mul, m_c_Mul(m_OneUse(m_CombineOr(m_Add(m_Value(A), m_Value(B)),
+ m_Sub(m_Value(A), m_Value(B)))),
+ m_ImmConstant())))
+ return false;
+
+ if (!Mul->hasOneUse())
+ return false;
+
+ auto *MulUser = dyn_cast<Instruction>(Mul->user_back());
+ // The parent MUST be an Add or Sub to ensure the tree is flattened
+ if (!MulUser || (MulUser->getOpcode() != Instruction::Add &&
+ MulUser->getOpcode() != Instruction::Sub))
+ return false;
+
+ if (!MulUser)
+ return false;
+
+ for (Value *Sibling : MulUser->operands()) {
+ if (Sibling == Mul)
+ continue;
+
+ // Sibling must be NonConst * C'.
+ Value *SibNC;
+ if (match(Sibling, m_Mul(m_Value(SibNC), m_Constant()))) {
+ if ((SibNC == A || SibNC == B) && !isa<Constant>(SibNC))
+ return true;
+ }
+ }
+ return false;
+}
+
+/// Distribute Mul of the form (X+Y)*C into X*C + Y*C.
+/// For the sub case (X-Y)*C, the second term uses -C to avoid
+/// introducing a negation instruction.
+static BinaryOperator *BreakUpDistribute(Instruction *Mul,
+ ReassociatePass::OrderedSet &ToRedo) {
+
+ Instruction *AddSub = cast<Instruction>(Mul->getOperand(0));
+ Constant *C = cast<Constant>(Mul->getOperand(1));
+ Constant *C2 = (AddSub->getOpcode() == Instruction::Sub)
+ ? cast<Constant>(ConstantExpr::getNeg(C))
+ : C;
+
+ BinaryOperator *M1 =
+ CreateMul(AddSub->getOperand(0), C, "Mul1", Mul->getIterator(), Mul);
+ BinaryOperator *M2 =
+ CreateMul(AddSub->getOperand(1), C2, "Mul2", Mul->getIterator(), Mul);
+ BinaryOperator *Result;
+ Result = CreateAdd(M1, M2, "DistAdd", Mul->getIterator(), Mul);
+
+ Mul->replaceAllUsesWith(Result);
+ Result->setDebugLoc(Mul->getDebugLoc());
+
+ return Result;
+}
+
/// Return true if we should break up this subtract of X-Y into (X + -Y).
static bool ShouldBreakUpSubtract(Instruction *Sub) {
// If this is a negation, we can't split it up!
@@ -1603,7 +1665,10 @@ Value *ReassociatePass::OptimizeAdd(Instruction *I,
continue;
unsigned Occ = ++FactorOccurrences[Factor];
- if (Occ > MaxOcc) {
+ if (Occ > MaxOcc ||
+ (Occ == MaxOcc &&
+ (isa<Instruction>(Factor) || isa<Argument>(Factor)) &&
+ isa<Constant>(MaxOccVal) && !isa<UndefValue>(MaxOccVal))) {
MaxOcc = Occ;
MaxOccVal = Factor;
}
@@ -1617,7 +1682,10 @@ Value *ReassociatePass::OptimizeAdd(Instruction *I,
if (!Duplicates.insert(Factor).second)
continue;
unsigned Occ = ++FactorOccurrences[Factor];
- if (Occ > MaxOcc) {
+ if (Occ > MaxOcc ||
+ (Occ == MaxOcc &&
+ (isa<Instruction>(Factor) || isa<Argument>(Factor)) &&
+ isa<Constant>(MaxOccVal) && !isa<UndefValue>(MaxOccVal))) {
MaxOcc = Occ;
MaxOccVal = Factor;
}
@@ -1630,7 +1698,10 @@ Value *ReassociatePass::OptimizeAdd(Instruction *I,
if (!Duplicates.insert(Factor).second)
continue;
unsigned Occ = ++FactorOccurrences[Factor];
- if (Occ > MaxOcc) {
+ if (Occ > MaxOcc ||
+ (Occ == MaxOcc &&
+ (isa<Instruction>(Factor) || isa<Argument>(Factor)) &&
+ isa<Constant>(MaxOccVal) && !isa<UndefValue>(MaxOccVal))) {
MaxOcc = Occ;
MaxOccVal = Factor;
}
@@ -2197,6 +2268,15 @@ void ReassociatePass::OptimizeInst(Instruction *I) {
I = NI;
}
+ if (I->getOpcode() == Instruction::Mul && ShouldBreakUpDistribution(I)) {
+ Instruction *MulUser = cast<Instruction>(I->user_back());
+ BreakUpDistribute(I, RedoInsts);
+ RedoInsts.insert(I);
+ RedoInsts.insert(MulUser);
+ MadeChange = true;
+ return;
+ }
+
// If this is a subtract instruction which is not already in negate form,
// see if we can convert it to X+-Y.
if (I->getOpcode() == Instruction::Sub) {
diff --git a/llvm/test/Transforms/Reassociate/reassociate-distribute.ll b/llvm/test/Transforms/Reassociate/reassociate-distribute.ll
new file mode 100644
index 0000000000000..3ad8bc13e8364
--- /dev/null
+++ b/llvm/test/Transforms/Reassociate/reassociate-distribute.ll
@@ -0,0 +1,154 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=reassociate -S %s | FileCheck %s
+
+; ---- SHOULD transform ----
+
+; Basic case: a*8697 - (a+b)*6436 → a*2261 + b*(-6436)
+define i32 @test_basic(i32 %a, i32 %b) {
+; CHECK-LABEL: @test_basic(
+; CHECK-NEXT: [[MUL1_NEG:%.*]] = mul i32 [[B:%.*]], -6436
+; CHECK-NEXT: [[REASS_MUL:%.*]] = mul i32 [[A:%.*]], 2261
+; CHECK-NEXT: [[SUB:%.*]] = add i32 [[REASS_MUL]], [[MUL1_NEG]]
+; CHECK-NEXT: ret i32 [[SUB]]
+;
+ %mul = mul nsw i32 %a, 8697
+ %add = add nsw i32 %a, %b
+ %mul1 = mul nsw i32 %add, 6436
+ %sub = sub nsw i32 %mul, %mul1
+ ret i32 %sub
+}
+
+; Constant on left side of mul: a*100 + 3*(a+b)
+define i32 @test_const_on_left(i32 %a, i32 %b) {
+; CHECK-LABEL: @test_const_on_left(
+; CHECK-NEXT: [[MUL1:%.*]] = mul i32 [[B:%.*]], 7
+; CHECK-NEXT: [[REASS_MUL:%.*]] = mul i32 [[A:%.*]], 107
+; CHECK-NEXT: [[ADD2:%.*]] = add i32 [[MUL1]], [[REASS_MUL]]
+; CHECK-NEXT: ret i32 [[ADD2]]
+;
+ %mul = mul nsw i32 %a, 100
+ %add = add nsw i32 %a, %b
+ %mul1 = mul nsw i32 7, %add
+ %add2 = add nsw i32 %mul, %mul1
+ ret i32 %add2
+}
+
+; Sub instead of add inside: a*500 - (a-b)*300
+define i32 @test_with_sub(i32 %a, i32 %b) {
+; CHECK-LABEL: @test_with_sub(
+; CHECK-NEXT: [[MUL2_NEG_NEG:%.*]] = mul i32 [[B:%.*]], 300
+; CHECK-NEXT: [[REASS_MUL:%.*]] = mul i32 [[A:%.*]], 200
+; CHECK-NEXT: [[SUB:%.*]] = add i32 [[REASS_MUL]], [[MUL2_NEG_NEG]]
+; CHECK-NEXT: ret i32 [[SUB]]
+;
+ %mul = mul nsw i32 %a, 500
+ %sub1 = sub nsw i32 %a, %b
+ %mul1 = mul nsw i32 %sub1, 300
+ %sub = sub nsw i32 %mul, %mul1
+ ret i32 %sub
+}
+
+; b operand matches: b*11 + (a+b)*4
+define i32 @test_b_matches(i32 %a, i32 %b) {
+; CHECK-LABEL: @test_b_matches(
+; CHECK-NEXT: [[MUL2:%.*]] = mul i32 [[A:%.*]], 4
+; CHECK-NEXT: [[REASS_MUL:%.*]] = mul i32 [[B:%.*]], 15
+; CHECK-NEXT: [[ADD2:%.*]] = add i32 [[REASS_MUL]], [[MUL2]]
+; CHECK-NEXT: ret i32 [[ADD2]]
+;
+ %mul = mul nsw i32 %b, 11
+ %add = add nsw i32 %a, %b
+ %mul1 = mul nsw i32 %add, 4
+ %add2 = add nsw i32 %mul, %mul1
+ ret i32 %add2
+}
+
+; i16 type: x*10 + (x+y)*20
+define i16 @test_i16(i16 %x, i16 %y) {
+; CHECK-LABEL: @test_i16(
+; CHECK-NEXT: [[MUL1:%.*]] = mul i16 [[Y:%.*]], 20
+; CHECK-NEXT: [[REASS_MUL:%.*]] = mul i16 [[X:%.*]], 30
+; CHECK-NEXT: [[ADD2:%.*]] = add i16 [[MUL1]], [[REASS_MUL]]
+; CHECK-NEXT: ret i16 [[ADD2]]
+;
+ %mul1 = mul nsw i16 %x, 10
+ %add = add nsw i16 %x, %y
+ %mul2 = mul nsw i16 %add, 20
+ %add2 = add i16 %mul1, %mul2
+ ret i16 %add2
+}
+
+; NSW/NUW must be dropped on new instructions after distribution
+; (x+y) *nsw 20 does NOT imply (x *nsw 20) + (y *nsw 20)
+define i16 @test_nsw_dropped(i16 %x, i16 %y) {
+; CHECK-LABEL: @test_nsw_dropped(
+; CHECK-NEXT: [[MUL1:%.*]] = mul i16 [[Y:%.*]], 25
+; CHECK-NEXT: [[REASS_MUL:%.*]] = mul i16 [[X:%.*]], 40
+; CHECK-NEXT: [[ADD2:%.*]] = add i16 [[MUL1]], [[REASS_MUL]]
+; CHECK-NEXT: ret i16 [[ADD2]]
+;
+ %mul1 = mul nsw i16 %x, 15
+ %add = add nsw i16 %x, %y
+ %mul2 = mul nsw i16 %add, 25
+ %add2 = add i16 %mul1, %mul2
+ ret i16 %add2
+}
+
+; ---- Should NOT transform ----
+
+; No sibling constant mul — nothing to combine with
+define i32 @test_no_match(i32 %a, i32 %b) {
+; CHECK-LABEL: @test_no_match(
+; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 [[B:%.*]], [[A:%.*]]
+; CHECK-NEXT: [[MUL:%.*]] = mul nsw i32 [[ADD]], 999
+; CHECK-NEXT: ret i32 [[MUL]]
+; CHECK-NOT: Mul1
+; CHECK-NOT: Mul2
+; CHECK-NOT: DistAdd
+; CHECK-NOT: DistSub
+;
+ %add = add nsw i32 %a, %b
+ %mul = mul nsw i32 %add, 999
+ ret i32 %mul
+}
+
+; AddSub has multiple uses — oneUse required for distribution
+define i32 @test_multi_use_add(i32 %a, i32 %b) {
+; CHECK-LABEL: @test_multi_use_add(
+; CHECK-NEXT: [[MUL1:%.*]] = mul i32 [[B:%.*]], -442
+; CHECK-NEXT: [[REASS_MUL:%.*]] = mul i32 [[A:%.*]], 335
+; CHECK-NEXT: [[RET:%.*]] = add i32 [[REASS_MUL]], [[MUL1]]
+; CHECK-NEXT: ret i32 [[RET]]
+; CHECK-NOT: Mul1
+; CHECK-NOT: Mul2
+; CHECK-NOT: DistAdd
+; CHECK-NOT: DistSub
+;
+ %mul = mul nsw i32 %a, 777
+ %add = add nsw i32 %a, %b
+ %mul1 = mul nsw i32 %add, 444
+ %mul2 = mul nsw i32 %add, 2
+ %sub = sub nsw i32 %mul, %mul1
+ %ret = add nsw i32 %sub, %mul2
+ ret i32 %ret
+}
+
+; Sibling mul has no constant operand — should not trigger
+define i32 @test_no_const_on_other_mul(i32 %a, i32 %b, i32 %c) {
+; CHECK-LABEL: @test_no_const_on_other_mul(
+; CHECK-NEXT: [[MUL:%.*]] = mul nsw i32 [[C:%.*]], [[A:%.*]]
+; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 [[B:%.*]], [[A]]
+; CHECK-NEXT: [[MUL1:%.*]] = mul nsw i32 [[ADD]], 555
+; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[MUL]], [[MUL1]]
+; CHECK-NEXT: ret i32 [[SUB]]
+; CHECK-NOT: Mul1
+; CHECK-NOT: Mul2
+; CHECK-NOT: DistAdd
+; CHECK-NOT: DistSub
+;
+ %mul = mul nsw i32 %a, %c
+ %add = add nsw i32 %a, %b
+ %mul1 = mul nsw i32 %add, 555
+ %sub = sub nsw i32 %mul, %mul1
+ ret i32 %sub
+}
>From 4ef404f710946e613b93bca2ebe241a78f51e113 Mon Sep 17 00:00:00 2001
From: hazarathayya <hazarathayyayallanki at gmail.com>
Date: Wed, 29 Apr 2026 02:22:02 -0700
Subject: [PATCH 2/5] added sibling oneuse check, updated createmul, createadd
to remove check there itself, added to redo the new instructions
---
llvm/lib/Transforms/Scalar/Reassociate.cpp | 15 ++++++-----
.../Reassociate/reassociate-distribute.ll | 27 ++++++++++---------
2 files changed, 23 insertions(+), 19 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 989387d704923..9f13bd41082fa 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -983,11 +983,8 @@ static bool ShouldBreakUpDistribution(Instruction *Mul) {
MulUser->getOpcode() != Instruction::Sub))
return false;
- if (!MulUser)
- return false;
-
for (Value *Sibling : MulUser->operands()) {
- if (Sibling == Mul)
+ if (Sibling == Mul || !Sibling->hasOneUse())
continue;
// Sibling must be NonConst * C'.
@@ -1013,15 +1010,19 @@ static BinaryOperator *BreakUpDistribute(Instruction *Mul,
: C;
BinaryOperator *M1 =
- CreateMul(AddSub->getOperand(0), C, "Mul1", Mul->getIterator(), Mul);
+ CreateMul(AddSub->getOperand(0), C, "Mul1", Mul->getIterator(), nullptr);
BinaryOperator *M2 =
- CreateMul(AddSub->getOperand(1), C2, "Mul2", Mul->getIterator(), Mul);
+ CreateMul(AddSub->getOperand(1), C2, "Mul2", Mul->getIterator(), nullptr);
BinaryOperator *Result;
- Result = CreateAdd(M1, M2, "DistAdd", Mul->getIterator(), Mul);
+ Result = CreateAdd(M1, M2, "DistAdd", Mul->getIterator(), nullptr);
Mul->replaceAllUsesWith(Result);
Result->setDebugLoc(Mul->getDebugLoc());
+ ToRedo.insert(M1);
+ ToRedo.insert(M2);
+ ToRedo.insert(Result);
+
return Result;
}
diff --git a/llvm/test/Transforms/Reassociate/reassociate-distribute.ll b/llvm/test/Transforms/Reassociate/reassociate-distribute.ll
index 3ad8bc13e8364..b2057d168796c 100644
--- a/llvm/test/Transforms/Reassociate/reassociate-distribute.ll
+++ b/llvm/test/Transforms/Reassociate/reassociate-distribute.ll
@@ -94,6 +94,21 @@ define i16 @test_nsw_dropped(i16 %x, i16 %y) {
ret i16 %add2
}
+define i16 @test_surviving_poison(i16 %x, i16 %y) {
+; CHECK-LABEL: @test_surviving_poison(
+; CHECK-NEXT: [[MUL1:%.*]] = mul i16 [[Y:%.*]], 20
+; CHECK-NEXT: [[REASS_MUL:%.*]] = mul i16 [[X:%.*]], 30
+; CHECK-NEXT: [[ADD2:%.*]] = add i16 [[MUL1]], [[REASS_MUL]]
+; CHECK-NEXT: ret i16 [[ADD2]]
+;
+ %add = add nsw i16 %x, %y
+ %mul1 = mul nsw i16 %x, 10
+ ; This mul has 'nsw'. We distribute it to x*20 and y*20.
+ %mul2 = mul nsw i16 %add, 20
+ %add2 = add i16 %mul1, %mul2
+ ret i16 %add2
+}
+
; ---- Should NOT transform ----
; No sibling constant mul — nothing to combine with
@@ -102,10 +117,6 @@ define i32 @test_no_match(i32 %a, i32 %b) {
; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = mul nsw i32 [[ADD]], 999
; CHECK-NEXT: ret i32 [[MUL]]
-; CHECK-NOT: Mul1
-; CHECK-NOT: Mul2
-; CHECK-NOT: DistAdd
-; CHECK-NOT: DistSub
;
%add = add nsw i32 %a, %b
%mul = mul nsw i32 %add, 999
@@ -119,10 +130,6 @@ define i32 @test_multi_use_add(i32 %a, i32 %b) {
; CHECK-NEXT: [[REASS_MUL:%.*]] = mul i32 [[A:%.*]], 335
; CHECK-NEXT: [[RET:%.*]] = add i32 [[REASS_MUL]], [[MUL1]]
; CHECK-NEXT: ret i32 [[RET]]
-; CHECK-NOT: Mul1
-; CHECK-NOT: Mul2
-; CHECK-NOT: DistAdd
-; CHECK-NOT: DistSub
;
%mul = mul nsw i32 %a, 777
%add = add nsw i32 %a, %b
@@ -141,10 +148,6 @@ define i32 @test_no_const_on_other_mul(i32 %a, i32 %b, i32 %c) {
; CHECK-NEXT: [[MUL1:%.*]] = mul nsw i32 [[ADD]], 555
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[MUL]], [[MUL1]]
; CHECK-NEXT: ret i32 [[SUB]]
-; CHECK-NOT: Mul1
-; CHECK-NOT: Mul2
-; CHECK-NOT: DistAdd
-; CHECK-NOT: DistSub
;
%mul = mul nsw i32 %a, %c
%add = add nsw i32 %a, %b
>From 5ce52320966b94485ca38d3d533ed851b74489f9 Mon Sep 17 00:00:00 2001
From: hazarathayya <hazarathayyayallanki at gmail.com>
Date: Wed, 6 May 2026 07:44:52 -0700
Subject: [PATCH 3/5] added lambda helpers, used binary operator's creatmul and
createadd
---
llvm/lib/Transforms/Scalar/Reassociate.cpp | 35 +++++++++++-----------
1 file changed, 17 insertions(+), 18 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 9f13bd41082fa..c881811922519 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -974,9 +974,6 @@ static bool ShouldBreakUpDistribution(Instruction *Mul) {
m_ImmConstant())))
return false;
- if (!Mul->hasOneUse())
- return false;
-
auto *MulUser = dyn_cast<Instruction>(Mul->user_back());
// The parent MUST be an Add or Sub to ensure the tree is flattened
if (!MulUser || (MulUser->getOpcode() != Instruction::Add &&
@@ -1010,11 +1007,11 @@ static BinaryOperator *BreakUpDistribute(Instruction *Mul,
: C;
BinaryOperator *M1 =
- CreateMul(AddSub->getOperand(0), C, "Mul1", Mul->getIterator(), nullptr);
+ BinaryOperator::CreateMul(AddSub->getOperand(0), C, "Mul1", Mul->getIterator());
BinaryOperator *M2 =
- CreateMul(AddSub->getOperand(1), C2, "Mul2", Mul->getIterator(), nullptr);
+ BinaryOperator::CreateMul(AddSub->getOperand(1), C2, "Mul2", Mul->getIterator());
BinaryOperator *Result;
- Result = CreateAdd(M1, M2, "DistAdd", Mul->getIterator(), nullptr);
+ Result = BinaryOperator::CreateAdd(M1, M2, "DistAdd", Mul->getIterator());
Mul->replaceAllUsesWith(Result);
Result->setDebugLoc(Mul->getDebugLoc());
@@ -1648,6 +1645,17 @@ Value *ReassociatePass::OptimizeAdd(Instruction *I,
// where they are actually the same multiply.
unsigned MaxOcc = 0;
Value *MaxOccVal = nullptr;
+
+ // Prefer a non-constant factor over a constant when occurrence counts
+ // tie. Factoring out a variable (e.g., X from X*C1 + X*C2) exposes
+ // downstream constant folding; factoring out a constant does not.
+ auto IsBetterFactor = [](Value *Factor, Value *MaxOccVal, unsigned Occ,
+ unsigned MaxOcc) {
+ return Occ > MaxOcc ||
+ (Occ == MaxOcc &&
+ (isa<Instruction>(Factor) || isa<Argument>(Factor)) &&
+ isa<Constant>(MaxOccVal) && !isa<UndefValue>(MaxOccVal));
+ };
for (const ValueEntry &Op : Ops) {
BinaryOperator *BOp =
isReassociableOp(Op.Op, Instruction::Mul, Instruction::FMul);
@@ -1666,10 +1674,7 @@ Value *ReassociatePass::OptimizeAdd(Instruction *I,
continue;
unsigned Occ = ++FactorOccurrences[Factor];
- if (Occ > MaxOcc ||
- (Occ == MaxOcc &&
- (isa<Instruction>(Factor) || isa<Argument>(Factor)) &&
- isa<Constant>(MaxOccVal) && !isa<UndefValue>(MaxOccVal))) {
+ if (IsBetterFactor(Factor, MaxOccVal, Occ, MaxOcc)) {
MaxOcc = Occ;
MaxOccVal = Factor;
}
@@ -1683,10 +1688,7 @@ Value *ReassociatePass::OptimizeAdd(Instruction *I,
if (!Duplicates.insert(Factor).second)
continue;
unsigned Occ = ++FactorOccurrences[Factor];
- if (Occ > MaxOcc ||
- (Occ == MaxOcc &&
- (isa<Instruction>(Factor) || isa<Argument>(Factor)) &&
- isa<Constant>(MaxOccVal) && !isa<UndefValue>(MaxOccVal))) {
+ if (IsBetterFactor(Factor, MaxOccVal, Occ, MaxOcc)) {
MaxOcc = Occ;
MaxOccVal = Factor;
}
@@ -1699,10 +1701,7 @@ Value *ReassociatePass::OptimizeAdd(Instruction *I,
if (!Duplicates.insert(Factor).second)
continue;
unsigned Occ = ++FactorOccurrences[Factor];
- if (Occ > MaxOcc ||
- (Occ == MaxOcc &&
- (isa<Instruction>(Factor) || isa<Argument>(Factor)) &&
- isa<Constant>(MaxOccVal) && !isa<UndefValue>(MaxOccVal))) {
+ if (IsBetterFactor(Factor, MaxOccVal, Occ, MaxOcc)) {
MaxOcc = Occ;
MaxOccVal = Factor;
}
>From 9be43d151a805ab8383fb310d9a9b8bdc8837395 Mon Sep 17 00:00:00 2001
From: Hazarath <92698778+hazarathayya at users.noreply.github.com>
Date: Wed, 6 May 2026 20:41:28 +0530
Subject: [PATCH 4/5] Apply suggestions from code review
Co-authored-by: Yingwei Zheng <dtcxzyw at qq.com>
---
llvm/lib/Transforms/Scalar/Reassociate.cpp | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index c881811922519..e23d1f73c06b5 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -986,10 +986,9 @@ static bool ShouldBreakUpDistribution(Instruction *Mul) {
// Sibling must be NonConst * C'.
Value *SibNC;
- if (match(Sibling, m_Mul(m_Value(SibNC), m_Constant()))) {
- if ((SibNC == A || SibNC == B) && !isa<Constant>(SibNC))
- return true;
- }
+ if (match(Sibling, m_Mul(m_Value(SibNC), m_Constant())) && (SibNC == A || SibNC == B) && !isa<Constant>(SibNC))
+ return true;
+
}
return false;
}
@@ -1002,7 +1001,7 @@ static BinaryOperator *BreakUpDistribute(Instruction *Mul,
Instruction *AddSub = cast<Instruction>(Mul->getOperand(0));
Constant *C = cast<Constant>(Mul->getOperand(1));
- Constant *C2 = (AddSub->getOpcode() == Instruction::Sub)
+ Constant *C2 = AddSub->getOpcode() == Instruction::Sub
? cast<Constant>(ConstantExpr::getNeg(C))
: C;
>From c882cc9ce6a024e81b08f8c9a1ec4c52f4739946 Mon Sep 17 00:00:00 2001
From: Hazarath <92698778+hazarathayya at users.noreply.github.com>
Date: Wed, 6 May 2026 21:01:02 +0530
Subject: [PATCH 5/5] Fix formatting and alignment in Reassociate.cpp
---
llvm/lib/Transforms/Scalar/Reassociate.cpp | 5480 ++++++++++----------
1 file changed, 2740 insertions(+), 2740 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index e23d1f73c06b5..47d4f85ed5fbc 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -1,2742 +1,2742 @@
-//===- Reassociate.cpp - Reassociate binary expressions -------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// This pass reassociates commutative expressions in an order that is designed
-// to promote better constant propagation, GCSE, LICM, PRE, etc.
-//
-// For example: 4 + (x + 5) -> x + (4 + 5)
-//
-// In the implementation of this algorithm, constants are assigned rank = 0,
-// function arguments are rank = 1, and other values are assigned ranks
-// corresponding to the reverse post order traversal of current function
-// (starting at 2), which effectively gives values in deep loops higher rank
-// than values not in loops.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/Scalar/Reassociate.h"
-#include "llvm/ADT/APFloat.h"
-#include "llvm/ADT/APInt.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/PostOrderIterator.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Analysis/BasicAliasAnalysis.h"
-#include "llvm/Analysis/ConstantFolding.h"
-#include "llvm/Analysis/GlobalsModRef.h"
-#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/IR/Argument.h"
-#include "llvm/IR/BasicBlock.h"
-#include "llvm/IR/CFG.h"
-#include "llvm/IR/Constant.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/Function.h"
-#include "llvm/IR/IRBuilder.h"
-#include "llvm/IR/InstrTypes.h"
-#include "llvm/IR/Instruction.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/Operator.h"
-#include "llvm/IR/PassManager.h"
-#include "llvm/IR/PatternMatch.h"
-#include "llvm/IR/Type.h"
-#include "llvm/IR/User.h"
-#include "llvm/IR/Value.h"
-#include "llvm/IR/ValueHandle.h"
-#include "llvm/InitializePasses.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/Casting.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include <algorithm>
-#include <cassert>
-#include <utility>
-
-using namespace llvm;
-using namespace reassociate;
-using namespace PatternMatch;
-
-#define DEBUG_TYPE "reassociate"
-
-STATISTIC(NumChanged, "Number of insts reassociated");
-STATISTIC(NumAnnihil, "Number of expr tree annihilated");
-STATISTIC(NumFactor , "Number of multiplies factored");
-
-static cl::opt<bool>
- UseCSELocalOpt(DEBUG_TYPE "-use-cse-local",
- cl::desc("Only reorder expressions within a basic block "
- "when exposing CSE opportunities"),
- cl::init(true), cl::Hidden);
-
-#ifndef NDEBUG
-/// Print out the expression identified in the Ops list.
-static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
- Module *M = I->getModule();
- dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
- << *Ops[0].Op->getType() << '\t';
- for (const ValueEntry &Op : Ops) {
- dbgs() << "[ ";
- Op.Op->printAsOperand(dbgs(), false, M);
- dbgs() << ", #" << Op.Rank << "] ";
- }
-}
-#endif
-
-/// Utility class representing a non-constant Xor-operand. We classify
-/// non-constant Xor-Operands into two categories:
-/// C1) The operand is in the form "X & C", where C is a constant and C != ~0
-/// C2)
-/// C2.1) The operand is in the form of "X | C", where C is a non-zero
-/// constant.
-/// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
-/// operand as "E | 0"
-class llvm::reassociate::XorOpnd {
-public:
- XorOpnd(Value *V);
-
- bool isInvalid() const { return SymbolicPart == nullptr; }
- bool isOrExpr() const { return isOr; }
- Value *getValue() const { return OrigVal; }
- Value *getSymbolicPart() const { return SymbolicPart; }
- unsigned getSymbolicRank() const { return SymbolicRank; }
- const APInt &getConstPart() const { return ConstPart; }
-
- void Invalidate() { SymbolicPart = OrigVal = nullptr; }
- void setSymbolicRank(unsigned R) { SymbolicRank = R; }
-
-private:
- Value *OrigVal;
- Value *SymbolicPart;
- APInt ConstPart;
- unsigned SymbolicRank;
- bool isOr;
-};
-
-XorOpnd::XorOpnd(Value *V) {
- assert(!isa<ConstantInt>(V) && "No ConstantInt");
- OrigVal = V;
- Instruction *I = dyn_cast<Instruction>(V);
- SymbolicRank = 0;
-
- if (I && (I->getOpcode() == Instruction::Or ||
- I->getOpcode() == Instruction::And)) {
- Value *V0 = I->getOperand(0);
- Value *V1 = I->getOperand(1);
- const APInt *C;
- if (match(V0, m_APInt(C)))
- std::swap(V0, V1);
-
- if (match(V1, m_APInt(C))) {
- ConstPart = *C;
- SymbolicPart = V0;
- isOr = (I->getOpcode() == Instruction::Or);
- return;
- }
- }
-
- // view the operand as "V | 0"
- SymbolicPart = V;
- ConstPart = APInt::getZero(V->getType()->getScalarSizeInBits());
- isOr = true;
-}
-
-/// Return true if I is an instruction with the FastMathFlags that are needed
-/// for general reassociation set. This is not the same as testing
-/// Instruction::isAssociative() because it includes operations like fsub.
-/// (This routine is only intended to be called for floating-point operations.)
-static bool hasFPAssociativeFlags(Instruction *I) {
- assert(I && isa<FPMathOperator>(I) && "Should only check FP ops");
- return I->hasAllowReassoc() && I->hasNoSignedZeros();
-}
-
-/// Return true if V is an instruction of the specified opcode and if it
-/// only has one use.
-static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
- auto *BO = dyn_cast<BinaryOperator>(V);
- if (BO && BO->hasOneUse() && BO->getOpcode() == Opcode)
- if (!isa<FPMathOperator>(BO) || hasFPAssociativeFlags(BO))
- return BO;
- return nullptr;
-}
-
-static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1,
- unsigned Opcode2) {
- auto *BO = dyn_cast<BinaryOperator>(V);
- if (BO && BO->hasOneUse() &&
- (BO->getOpcode() == Opcode1 || BO->getOpcode() == Opcode2))
- if (!isa<FPMathOperator>(BO) || hasFPAssociativeFlags(BO))
- return BO;
- return nullptr;
-}
-
-void ReassociatePass::BuildRankMap(Function &F,
- ReversePostOrderTraversal<Function*> &RPOT) {
- unsigned Rank = 2;
-
- // Assign distinct ranks to function arguments.
- for (auto &Arg : F.args()) {
- ValueRankMap[&Arg] = ++Rank;
- LLVM_DEBUG(dbgs() << "Calculated Rank[" << Arg.getName() << "] = " << Rank
- << "\n");
- }
-
- // Traverse basic blocks in ReversePostOrder.
- for (BasicBlock *BB : RPOT) {
- unsigned BBRank = RankMap[BB] = ++Rank << 16;
-
- // Walk the basic block, adding precomputed ranks for any instructions that
- // we cannot move. This ensures that the ranks for these instructions are
- // all different in the block.
- for (Instruction &I : *BB)
- if (mayHaveNonDefUseDependency(I))
- ValueRankMap[&I] = ++BBRank;
- }
-}
-
-unsigned ReassociatePass::getRank(Value *V) {
- Instruction *I = dyn_cast<Instruction>(V);
- if (!I) {
- if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
- return 0; // Otherwise it's a global or constant, rank 0.
- }
-
- if (unsigned Rank = ValueRankMap[I])
- return Rank; // Rank already known?
-
- // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
- // we can reassociate expressions for code motion! Since we do not recurse
- // for PHI nodes, we cannot have infinite recursion here, because there
- // cannot be loops in the value graph that do not go through PHI nodes.
- unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
- for (unsigned i = 0, e = I->getNumOperands(); i != e && Rank != MaxRank; ++i)
- Rank = std::max(Rank, getRank(I->getOperand(i)));
-
- // If this is a 'not' or 'neg' instruction, do not count it for rank. This
- // assures us that X and ~X will have the same rank.
- if (!match(I, m_Not(m_Value())) && !match(I, m_Neg(m_Value())) &&
- !match(I, m_FNeg(m_Value())))
- ++Rank;
-
- LLVM_DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " << Rank
- << "\n");
-
- return ValueRankMap[I] = Rank;
-}
-
-// Canonicalize constants to RHS. Otherwise, sort the operands by rank.
-void ReassociatePass::canonicalizeOperands(Instruction *I) {
- assert(isa<BinaryOperator>(I) && "Expected binary operator.");
- assert(I->isCommutative() && "Expected commutative operator.");
-
- Value *LHS = I->getOperand(0);
- Value *RHS = I->getOperand(1);
- if (LHS == RHS || isa<Constant>(RHS))
- return;
- if (isa<Constant>(LHS) || getRank(RHS) < getRank(LHS)) {
- cast<BinaryOperator>(I)->swapOperands();
- MadeChange = true;
- }
-}
-
-static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name,
- BasicBlock::iterator InsertBefore,
- Value *FlagsOp) {
- if (S1->getType()->isIntOrIntVectorTy())
- return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore);
- else {
- BinaryOperator *Res =
- BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore);
- Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
- return Res;
- }
-}
-
-static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name,
- BasicBlock::iterator InsertBefore,
- Value *FlagsOp) {
- if (S1->getType()->isIntOrIntVectorTy())
- return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore);
- else {
- BinaryOperator *Res =
- BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore);
- Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
- return Res;
- }
-}
-
-static Instruction *CreateNeg(Value *S1, const Twine &Name,
- BasicBlock::iterator InsertBefore,
- Value *FlagsOp) {
- if (S1->getType()->isIntOrIntVectorTy())
- return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
-
- if (auto *FMFSource = dyn_cast<Instruction>(FlagsOp))
- return UnaryOperator::CreateFNegFMF(S1, FMFSource, Name, InsertBefore);
-
- return UnaryOperator::CreateFNeg(S1, Name, InsertBefore);
-}
-
-/// Replace 0-X with X*-1.
-static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) {
- assert((isa<UnaryOperator>(Neg) || isa<BinaryOperator>(Neg)) &&
- "Expected a Negate!");
- // FIXME: It's not safe to lower a unary FNeg into a FMul by -1.0.
- unsigned OpNo = isa<BinaryOperator>(Neg) ? 1 : 0;
- Type *Ty = Neg->getType();
- Constant *NegOne = Ty->isIntOrIntVectorTy() ?
- ConstantInt::getAllOnesValue(Ty) : ConstantFP::get(Ty, -1.0);
-
- BinaryOperator *Res =
- CreateMul(Neg->getOperand(OpNo), NegOne, "", Neg->getIterator(), Neg);
- Neg->setOperand(OpNo, Constant::getNullValue(Ty)); // Drop use of op.
- Res->takeName(Neg);
- Neg->replaceAllUsesWith(Res);
- Res->setDebugLoc(Neg->getDebugLoc());
- return Res;
-}
-
-using RepeatedValue = std::pair<Value *, uint64_t>;
-
-/// Given an associative binary expression, return the leaf
-/// nodes in Ops along with their weights (how many times the leaf occurs). The
-/// original expression is the same as
-/// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
-/// op
-/// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
-/// op
-/// ...
-/// op
-/// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
-///
-/// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
-///
-/// This routine may modify the function, in which case it returns 'true'. The
-/// changes it makes may well be destructive, changing the value computed by 'I'
-/// to something completely different. Thus if the routine returns 'true' then
-/// you MUST either replace I with a new expression computed from the Ops array,
-/// or use RewriteExprTree to put the values back in.
-///
-/// A leaf node is either not a binary operation of the same kind as the root
-/// node 'I' (i.e. is not a binary operator at all, or is, but with a different
-/// opcode), or is the same kind of binary operator but has a use which either
-/// does not belong to the expression, or does belong to the expression but is
-/// a leaf node. Every leaf node has at least one use that is a non-leaf node
-/// of the expression, while for non-leaf nodes (except for the root 'I') every
-/// use is a non-leaf node of the expression.
-///
-/// For example:
-/// expression graph node names
-///
-/// + | I
-/// / \ |
-/// + + | A, B
-/// / \ / \ |
-/// * + * | C, D, E
-/// / \ / \ / \ |
-/// + * | F, G
-///
-/// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
-/// that order) (C, 1), (E, 1), (F, 2), (G, 2).
-///
-/// The expression is maximal: if some instruction is a binary operator of the
-/// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
-/// then the instruction also belongs to the expression, is not a leaf node of
-/// it, and its operands also belong to the expression (but may be leaf nodes).
-///
-/// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
-/// order to ensure that every non-root node in the expression has *exactly one*
-/// use by a non-leaf node of the expression. This destruction means that the
-/// caller MUST either replace 'I' with a new expression or use something like
-/// RewriteExprTree to put the values back in if the routine indicates that it
-/// made a change by returning 'true'.
-///
-/// In the above example either the right operand of A or the left operand of B
-/// will be replaced by undef. If it is B's operand then this gives:
-///
-/// + | I
-/// / \ |
-/// + + | A, B - operand of B replaced with undef
-/// / \ \ |
-/// * + * | C, D, E
-/// / \ / \ / \ |
-/// + * | F, G
-///
-/// Note that such undef operands can only be reached by passing through 'I'.
-/// For example, if you visit operands recursively starting from a leaf node
-/// then you will never see such an undef operand unless you get back to 'I',
-/// which requires passing through a phi node.
-///
-/// Note that this routine may also mutate binary operators of the wrong type
-/// that have all uses inside the expression (i.e. only used by non-leaf nodes
-/// of the expression) if it can turn them into binary operators of the right
-/// type and thus make the expression bigger.
-static bool LinearizeExprTree(Instruction *I,
- SmallVectorImpl<RepeatedValue> &Ops,
- ReassociatePass::OrderedSet &ToRedo,
- OverflowTracking &Flags) {
- assert((isa<UnaryOperator>(I) || isa<BinaryOperator>(I)) &&
- "Expected a UnaryOperator or BinaryOperator!");
- LLVM_DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
- unsigned Opcode = I->getOpcode();
- assert(I->isAssociative() && I->isCommutative() &&
- "Expected an associative and commutative operation!");
-
- // Visit all operands of the expression, keeping track of their weight (the
- // number of paths from the expression root to the operand, or if you like
- // the number of times that operand occurs in the linearized expression).
- // For example, if I = X + A, where X = A + B, then I, X and B have weight 1
- // while A has weight two.
-
- // Worklist of non-leaf nodes (their operands are in the expression too) along
- // with their weights, representing a certain number of paths to the operator.
- // If an operator occurs in the worklist multiple times then we found multiple
- // ways to get to it.
- SmallVector<std::pair<Instruction *, uint64_t>, 8> Worklist; // (Op, Weight)
- Worklist.push_back(std::make_pair(I, 1));
- bool Changed = false;
-
- // Leaves of the expression are values that either aren't the right kind of
- // operation (eg: a constant, or a multiply in an add tree), or are, but have
- // some uses that are not inside the expression. For example, in I = X + X,
- // X = A + B, the value X has two uses (by I) that are in the expression. If
- // X has any other uses, for example in a return instruction, then we consider
- // X to be a leaf, and won't analyze it further. When we first visit a value,
- // if it has more than one use then at first we conservatively consider it to
- // be a leaf. Later, as the expression is explored, we may discover some more
- // uses of the value from inside the expression. If all uses turn out to be
- // from within the expression (and the value is a binary operator of the right
- // kind) then the value is no longer considered to be a leaf, and its operands
- // are explored.
-
- // Leaves - Keeps track of the set of putative leaves as well as the number of
- // paths to each leaf seen so far.
- using LeafMap = DenseMap<Value *, uint64_t>;
- LeafMap Leaves; // Leaf -> Total weight so far.
- SmallVector<Value *, 8> LeafOrder; // Ensure deterministic leaf output order.
- const DataLayout &DL = I->getDataLayout();
-
-#ifndef NDEBUG
- SmallPtrSet<Value *, 8> Visited; // For checking the iteration scheme.
-#endif
- while (!Worklist.empty()) {
- // We examine the operands of this binary operator.
- auto [I, Weight] = Worklist.pop_back_val();
-
- Flags.mergeFlags(*I);
-
- for (unsigned OpIdx = 0; OpIdx < I->getNumOperands(); ++OpIdx) { // Visit operands.
- Value *Op = I->getOperand(OpIdx);
- LLVM_DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n");
- assert((!Op->hasUseList() || !Op->use_empty()) &&
- "No uses, so how did we get to it?!");
-
- // If this is a binary operation of the right kind with only one use then
- // add its operands to the expression.
- if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
- assert(Visited.insert(Op).second && "Not first visit!");
- LLVM_DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n");
- Worklist.push_back(std::make_pair(BO, Weight));
- continue;
- }
-
- // Appears to be a leaf. Is the operand already in the set of leaves?
- LeafMap::iterator It = Leaves.find(Op);
- if (It == Leaves.end()) {
- // Not in the leaf map. Must be the first time we saw this operand.
- assert(Visited.insert(Op).second && "Not first visit!");
- if (!Op->hasOneUse()) {
- // This value has uses not accounted for by the expression, so it is
- // not safe to modify. Mark it as being a leaf.
- LLVM_DEBUG(dbgs()
- << "ADD USES LEAF: " << *Op << " (" << Weight << ")\n");
- LeafOrder.push_back(Op);
- Leaves[Op] = Weight;
- continue;
- }
- // No uses outside the expression, try morphing it.
- } else {
- // Already in the leaf map.
- assert(It != Leaves.end() && Visited.count(Op) &&
- "In leaf map but not visited!");
-
- // Update the number of paths to the leaf.
- It->second += Weight;
- assert(It->second >= Weight && "Weight overflows");
-
- // If we still have uses that are not accounted for by the expression
- // then it is not safe to modify the value.
- if (!Op->hasOneUse())
- continue;
-
- // No uses outside the expression, try morphing it.
- Weight = It->second;
- Leaves.erase(It); // Since the value may be morphed below.
- }
-
- // At this point we have a value which, first of all, is not a binary
- // expression of the right kind, and secondly, is only used inside the
- // expression. This means that it can safely be modified. See if we
- // can usefully morph it into an expression of the right kind.
- assert((!isa<Instruction>(Op) ||
- cast<Instruction>(Op)->getOpcode() != Opcode
- || (isa<FPMathOperator>(Op) &&
- !hasFPAssociativeFlags(cast<Instruction>(Op)))) &&
- "Should have been handled above!");
- assert(Op->hasOneUse() && "Has uses outside the expression tree!");
-
- // If this is a multiply expression, turn any internal negations into
- // multiplies by -1 so they can be reassociated. Add any users of the
- // newly created multiplication by -1 to the redo list, so any
- // reassociation opportunities that are exposed will be reassociated
- // further.
- Instruction *Neg;
- if (((Opcode == Instruction::Mul && match(Op, m_Neg(m_Value()))) ||
- (Opcode == Instruction::FMul && match(Op, m_FNeg(m_Value())))) &&
- match(Op, m_Instruction(Neg))) {
- LLVM_DEBUG(dbgs()
- << "MORPH LEAF: " << *Op << " (" << Weight << ") TO ");
- Instruction *Mul = LowerNegateToMultiply(Neg);
- LLVM_DEBUG(dbgs() << *Mul << '\n');
- Worklist.push_back(std::make_pair(Mul, Weight));
- for (User *U : Mul->users()) {
- if (BinaryOperator *UserBO = dyn_cast<BinaryOperator>(U))
- ToRedo.insert(UserBO);
- }
- ToRedo.insert(Neg);
- Changed = true;
- continue;
- }
-
- // Failed to morph into an expression of the right type. This really is
- // a leaf.
- LLVM_DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n");
- assert(!isReassociableOp(Op, Opcode) && "Value was morphed?");
- LeafOrder.push_back(Op);
- Leaves[Op] = Weight;
- }
- }
-
- // The leaves, repeated according to their weights, represent the linearized
- // form of the expression.
- for (Value *V : LeafOrder) {
- LeafMap::iterator It = Leaves.find(V);
- if (It == Leaves.end())
- // Node initially thought to be a leaf wasn't.
- continue;
- assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!");
- uint64_t Weight = It->second;
- // Ensure the leaf is only output once.
- It->second = 0;
- Ops.push_back(std::make_pair(V, Weight));
- if (Opcode == Instruction::Add && Flags.AllKnownNonNegative && Flags.HasNSW)
- Flags.AllKnownNonNegative &= isKnownNonNegative(V, SimplifyQuery(DL));
- else if (Opcode == Instruction::Mul) {
- // To preserve NUW we need all inputs non-zero.
- // To preserve NSW we need all inputs strictly positive.
- if (Flags.AllKnownNonZero &&
- (Flags.HasNUW || (Flags.HasNSW && Flags.AllKnownNonNegative))) {
- Flags.AllKnownNonZero &= isKnownNonZero(V, SimplifyQuery(DL));
- if (Flags.HasNSW && Flags.AllKnownNonNegative)
- Flags.AllKnownNonNegative &= isKnownNonNegative(V, SimplifyQuery(DL));
- }
- }
- }
-
- // For nilpotent operations or addition there may be no operands, for example
- // because the expression was "X xor X" or consisted of 2^Bitwidth additions:
- // in both cases the weight reduces to 0 causing the value to be skipped.
- if (Ops.empty()) {
- Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
- assert(Identity && "Associative operation without identity!");
- Ops.emplace_back(Identity, 1);
- }
-
- return Changed;
-}
-
-/// Now that the operands for this expression tree are
-/// linearized and optimized, emit them in-order.
-void ReassociatePass::RewriteExprTree(BinaryOperator *I,
- SmallVectorImpl<ValueEntry> &Ops,
- OverflowTracking Flags) {
- assert(Ops.size() > 1 && "Single values should be used directly!");
-
- // Since our optimizations should never increase the number of operations, the
- // new expression can usually be written reusing the existing binary operators
- // from the original expression tree, without creating any new instructions,
- // though the rewritten expression may have a completely different topology.
- // We take care to not change anything if the new expression will be the same
- // as the original. If more than trivial changes (like commuting operands)
- // were made then we are obliged to clear out any optional subclass data like
- // nsw flags.
-
- /// NodesToRewrite - Nodes from the original expression available for writing
- /// the new expression into.
- SmallVector<BinaryOperator*, 8> NodesToRewrite;
- unsigned Opcode = I->getOpcode();
- BinaryOperator *Op = I;
-
- /// NotRewritable - The operands being written will be the leaves of the new
- /// expression and must not be used as inner nodes (via NodesToRewrite) by
- /// mistake. Inner nodes are always reassociable, and usually leaves are not
- /// (if they were they would have been incorporated into the expression and so
- /// would not be leaves), so most of the time there is no danger of this. But
- /// in rare cases a leaf may become reassociable if an optimization kills uses
- /// of it, or it may momentarily become reassociable during rewriting (below)
- /// due it being removed as an operand of one of its uses. Ensure that misuse
- /// of leaf nodes as inner nodes cannot occur by remembering all of the future
- /// leaves and refusing to reuse any of them as inner nodes.
- SmallPtrSet<Value*, 8> NotRewritable;
- for (const ValueEntry &Op : Ops)
- NotRewritable.insert(Op.Op);
-
- // ExpressionChangedStart - Non-null if the rewritten expression differs from
- // the original in some non-trivial way, requiring the clearing of optional
- // flags. Flags are cleared from the operator in ExpressionChangedStart up to
- // ExpressionChangedEnd inclusive.
- BinaryOperator *ExpressionChangedStart = nullptr,
- *ExpressionChangedEnd = nullptr;
- for (unsigned i = 0; ; ++i) {
- // The last operation (which comes earliest in the IR) is special as both
- // operands will come from Ops, rather than just one with the other being
- // a subexpression.
- if (i+2 == Ops.size()) {
- Value *NewLHS = Ops[i].Op;
- Value *NewRHS = Ops[i+1].Op;
- Value *OldLHS = Op->getOperand(0);
- Value *OldRHS = Op->getOperand(1);
-
- if (NewLHS == OldLHS && NewRHS == OldRHS)
- // Nothing changed, leave it alone.
- break;
-
- if (NewLHS == OldRHS && NewRHS == OldLHS) {
- // The order of the operands was reversed. Swap them.
- LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
- Op->swapOperands();
- LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
- MadeChange = true;
- ++NumChanged;
- break;
- }
-
- // The new operation differs non-trivially from the original. Overwrite
- // the old operands with the new ones.
- LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
- if (NewLHS != OldLHS) {
- BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
- if (BO && !NotRewritable.count(BO))
- NodesToRewrite.push_back(BO);
- salvageDebugInfo(*Op);
- Op->setOperand(0, NewLHS);
- }
- if (NewRHS != OldRHS) {
- BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
- if (BO && !NotRewritable.count(BO))
- NodesToRewrite.push_back(BO);
- salvageDebugInfo(*Op);
- Op->setOperand(1, NewRHS);
- }
- LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
-
- ExpressionChangedStart = Op;
- if (!ExpressionChangedEnd)
- ExpressionChangedEnd = Op;
- MadeChange = true;
- ++NumChanged;
-
- break;
- }
-
- // Not the last operation. The left-hand side will be a sub-expression
- // while the right-hand side will be the current element of Ops.
- Value *NewRHS = Ops[i].Op;
- if (NewRHS != Op->getOperand(1)) {
- LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
- if (NewRHS == Op->getOperand(0)) {
- // The new right-hand side was already present as the left operand. If
- // we are lucky then swapping the operands will sort out both of them.
- Op->swapOperands();
- } else {
- // Overwrite with the new right-hand side.
- BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
- if (BO && !NotRewritable.count(BO))
- NodesToRewrite.push_back(BO);
- salvageDebugInfo(*Op);
- Op->setOperand(1, NewRHS);
- ExpressionChangedStart = Op;
- if (!ExpressionChangedEnd)
- ExpressionChangedEnd = Op;
- }
- LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
- MadeChange = true;
- ++NumChanged;
- }
-
- // Now deal with the left-hand side. If this is already an operation node
- // from the original expression then just rewrite the rest of the expression
- // into it.
- BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode);
- if (BO && !NotRewritable.count(BO)) {
- Op = BO;
- continue;
- }
-
- // Otherwise, grab a spare node from the original expression and use that as
- // the left-hand side. If there are no nodes left then the optimizers made
- // an expression with more nodes than the original! This usually means that
- // they did something stupid but it might mean that the problem was just too
- // hard (finding the mimimal number of multiplications needed to realize a
- // multiplication expression is NP-complete). Whatever the reason, smart or
- // stupid, create a new node if there are none left.
- BinaryOperator *NewOp;
- if (NodesToRewrite.empty()) {
- Constant *Poison = PoisonValue::get(I->getType());
- NewOp = BinaryOperator::Create(Instruction::BinaryOps(Opcode), Poison,
- Poison, "", I->getIterator());
- if (isa<FPMathOperator>(NewOp))
- NewOp->setFastMathFlags(I->getFastMathFlags());
- } else {
- NewOp = NodesToRewrite.pop_back_val();
- }
-
- LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
- salvageDebugInfo(*Op);
- Op->setOperand(0, NewOp);
- LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
- ExpressionChangedStart = Op;
- if (!ExpressionChangedEnd)
- ExpressionChangedEnd = Op;
- MadeChange = true;
- ++NumChanged;
- Op = NewOp;
- }
-
- // If the expression changed non-trivially then clear out all subclass data
- // starting from the operator specified in ExpressionChanged, and compactify
- // the operators to just before the expression root to guarantee that the
- // expression tree is dominated by all of Ops.
- if (ExpressionChangedStart) {
- bool ClearFlags = true;
- do {
- // Preserve flags.
- if (ClearFlags) {
- if (isa<FPMathOperator>(I)) {
- FastMathFlags Flags = I->getFastMathFlags();
- ExpressionChangedStart->clearSubclassOptionalData();
- ExpressionChangedStart->setFastMathFlags(Flags);
- } else {
- Flags.applyFlags(*ExpressionChangedStart);
- }
- }
-
- if (ExpressionChangedStart == ExpressionChangedEnd)
- ClearFlags = false;
- if (ExpressionChangedStart == I)
- break;
-
- ExpressionChangedStart->moveBefore(I->getIterator());
- ExpressionChangedStart =
- cast<BinaryOperator>(*ExpressionChangedStart->user_begin());
- } while (true);
- }
-
- // Throw away any left over nodes from the original expression.
- RedoInsts.insert_range(NodesToRewrite);
-}
-
-/// Insert instructions before the instruction pointed to by BI,
-/// that computes the negative version of the value specified. The negative
-/// version of the value is returned, and BI is left pointing at the instruction
-/// that should be processed next by the reassociation pass.
-/// Also add intermediate instructions to the redo list that are modified while
-/// pushing the negates through adds. These will be revisited to see if
-/// additional opportunities have been exposed.
-static Value *NegateValue(Value *V, Instruction *BI,
- ReassociatePass::OrderedSet &ToRedo) {
- if (auto *C = dyn_cast<Constant>(V)) {
- const DataLayout &DL = BI->getDataLayout();
- Constant *Res = C->getType()->isFPOrFPVectorTy()
- ? ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)
- : ConstantExpr::getNeg(C);
- if (Res)
- return Res;
- }
-
- // We are trying to expose opportunity for reassociation. One of the things
- // that we want to do to achieve this is to push a negation as deep into an
- // expression chain as possible, to expose the add instructions. In practice,
- // this means that we turn this:
- // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
- // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
- // the constants. We assume that instcombine will clean up the mess later if
- // we introduce tons of unnecessary negation instructions.
- //
- if (BinaryOperator *I =
- isReassociableOp(V, Instruction::Add, Instruction::FAdd)) {
- // Push the negates through the add.
- I->setOperand(0, NegateValue(I->getOperand(0), BI, ToRedo));
- I->setOperand(1, NegateValue(I->getOperand(1), BI, ToRedo));
- if (I->getOpcode() == Instruction::Add) {
- I->setHasNoUnsignedWrap(false);
- I->setHasNoSignedWrap(false);
- }
-
- // We must move the add instruction here, because the neg instructions do
- // not dominate the old add instruction in general. By moving it, we are
- // assured that the neg instructions we just inserted dominate the
- // instruction we are about to insert after them.
- //
- I->moveBefore(BI->getIterator());
- I->setName(I->getName()+".neg");
-
- // Add the intermediate negates to the redo list as processing them later
- // could expose more reassociating opportunities.
- ToRedo.insert(I);
- return I;
- }
-
- // Okay, we need to materialize a negated version of V with an instruction.
- // Scan the use lists of V to see if we have one already.
- for (User *U : V->users()) {
- if (!match(U, m_Neg(m_Value())) && !match(U, m_FNeg(m_Value())))
- continue;
-
- // We found one! Now we have to make sure that the definition dominates
- // this use. We do this by moving it to the entry block (if it is a
- // non-instruction value) or right after the definition. These negates will
- // be zapped by reassociate later, so we don't need much finesse here.
- Instruction *TheNeg = dyn_cast<Instruction>(U);
-
- // We can't safely propagate a vector zero constant with poison/undef lanes.
- Constant *C;
- if (match(TheNeg, m_BinOp(m_Constant(C), m_Value())) &&
- C->containsUndefOrPoisonElement())
- continue;
-
- // Verify that the negate is in this function, V might be a constant expr.
- if (!TheNeg ||
- TheNeg->getParent()->getParent() != BI->getParent()->getParent())
- continue;
-
- BasicBlock::iterator InsertPt;
- if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
- auto InsertPtOpt = InstInput->getInsertionPointAfterDef();
- if (!InsertPtOpt)
- continue;
- InsertPt = *InsertPtOpt;
- } else {
- InsertPt = TheNeg->getFunction()
- ->getEntryBlock()
- .getFirstNonPHIOrDbg()
- ->getIterator();
- }
-
- // Check that if TheNeg is moved out of its parent block, we drop its
- // debug location to avoid extra coverage.
- // See test dropping_debugloc_the_neg.ll for a detailed example.
- if (TheNeg->getParent() != InsertPt->getParent())
- TheNeg->dropLocation();
- TheNeg->moveBefore(*InsertPt->getParent(), InsertPt);
-
- if (TheNeg->getOpcode() == Instruction::Sub) {
- TheNeg->setHasNoUnsignedWrap(false);
- TheNeg->setHasNoSignedWrap(false);
- } else {
- TheNeg->andIRFlags(BI);
- }
- ToRedo.insert(TheNeg);
- return TheNeg;
- }
-
- // Insert a 'neg' instruction that subtracts the value from zero to get the
- // negation.
- Instruction *NewNeg =
- CreateNeg(V, V->getName() + ".neg", BI->getIterator(), BI);
- // NewNeg is generated to potentially replace BI, so use its DebugLoc.
- NewNeg->setDebugLoc(BI->getDebugLoc());
- ToRedo.insert(NewNeg);
- return NewNeg;
-}
-
-// See if this `or` looks like an load widening reduction, i.e. that it
-// consists of an `or`/`shl`/`zext`/`load` nodes only. Note that we don't
-// ensure that the pattern is *really* a load widening reduction,
-// we do not ensure that it can really be replaced with a widened load,
-// only that it mostly looks like one.
-static bool isLoadCombineCandidate(Instruction *Or) {
- SmallVector<Instruction *, 8> Worklist;
- SmallPtrSet<Instruction *, 8> Visited;
-
- auto Enqueue = [&](Value *V) {
- auto *I = dyn_cast<Instruction>(V);
- // Each node of an `or` reduction must be an instruction,
- if (!I)
- return false; // Node is certainly not part of an `or` load reduction.
- // Only process instructions we have never processed before.
- if (Visited.insert(I).second)
- Worklist.emplace_back(I);
- return true; // Will need to look at parent nodes.
- };
-
- if (!Enqueue(Or))
- return false; // Not an `or` reduction pattern.
-
- while (!Worklist.empty()) {
- auto *I = Worklist.pop_back_val();
-
- // Okay, which instruction is this node?
- switch (I->getOpcode()) {
- case Instruction::Or:
- // Got an `or` node. That's fine, just recurse into it's operands.
- for (Value *Op : I->operands())
- if (!Enqueue(Op))
- return false; // Not an `or` reduction pattern.
- continue;
-
- case Instruction::Shl:
- case Instruction::ZExt:
- // `shl`/`zext` nodes are fine, just recurse into their base operand.
- if (!Enqueue(I->getOperand(0)))
- return false; // Not an `or` reduction pattern.
- continue;
-
- case Instruction::Load:
- // Perfect, `load` node means we've reached an edge of the graph.
- continue;
-
- default: // Unknown node.
- return false; // Not an `or` reduction pattern.
- }
- }
-
- return true;
-}
-
-/// Return true if it may be profitable to convert this (X|Y) into (X+Y).
-static bool shouldConvertOrWithNoCommonBitsToAdd(Instruction *Or) {
- // Don't bother to convert this up unless either the LHS is an associable add
- // or subtract or mul or if this is only used by one of the above.
- // This is only a compile-time improvement, it is not needed for correctness!
- auto isInteresting = [](Value *V) {
- for (auto Op : {Instruction::Add, Instruction::Sub, Instruction::Mul,
- Instruction::Shl})
- if (isReassociableOp(V, Op))
- return true;
- return false;
- };
-
- if (any_of(Or->operands(), isInteresting))
- return true;
-
- Value *VB = Or->user_back();
- if (Or->hasOneUse() && isInteresting(VB))
- return true;
-
- return false;
-}
-
-/// If we have (X|Y), and iff X and Y have no common bits set,
-/// transform this into (X+Y) to allow arithmetics reassociation.
-static BinaryOperator *convertOrWithNoCommonBitsToAdd(Instruction *Or) {
- // Convert an or into an add.
- BinaryOperator *New = CreateAdd(Or->getOperand(0), Or->getOperand(1), "",
- Or->getIterator(), Or);
- New->setHasNoSignedWrap();
- New->setHasNoUnsignedWrap();
- New->takeName(Or);
-
- // Everyone now refers to the add instruction.
- Or->replaceAllUsesWith(New);
- New->setDebugLoc(Or->getDebugLoc());
-
- LLVM_DEBUG(dbgs() << "Converted or into an add: " << *New << '\n');
- return New;
-}
-
-/// Return true if Mul is of the form (X+Y)*C or (X-Y)*C where C is a
-/// constant, and there exists a sibling instruction of the form X*C' or Y*C'
-/// in the same expression — indicating that distribution followed by
-/// factoring will reduce the instruction count.
-static bool ShouldBreakUpDistribution(Instruction *Mul) {
- Value *A, *B;
- if (!match(Mul, m_c_Mul(m_OneUse(m_CombineOr(m_Add(m_Value(A), m_Value(B)),
- m_Sub(m_Value(A), m_Value(B)))),
- m_ImmConstant())))
- return false;
-
- auto *MulUser = dyn_cast<Instruction>(Mul->user_back());
- // The parent MUST be an Add or Sub to ensure the tree is flattened
- if (!MulUser || (MulUser->getOpcode() != Instruction::Add &&
- MulUser->getOpcode() != Instruction::Sub))
- return false;
-
- for (Value *Sibling : MulUser->operands()) {
- if (Sibling == Mul || !Sibling->hasOneUse())
- continue;
-
- // Sibling must be NonConst * C'.
- Value *SibNC;
- if (match(Sibling, m_Mul(m_Value(SibNC), m_Constant())) && (SibNC == A || SibNC == B) && !isa<Constant>(SibNC))
+//===- Reassociate.cpp - Reassociate binary expressions -------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass reassociates commutative expressions in an order that is designed
+// to promote better constant propagation, GCSE, LICM, PRE, etc.
+//
+// For example: 4 + (x + 5) -> x + (4 + 5)
+//
+// In the implementation of this algorithm, constants are assigned rank = 0,
+// function arguments are rank = 1, and other values are assigned ranks
+// corresponding to the reverse post order traversal of current function
+// (starting at 2), which effectively gives values in deep loops higher rank
+// than values not in loops.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar/Reassociate.h"
+#include "llvm/ADT/APFloat.h"
+#include "llvm/ADT/APInt.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/GlobalsModRef.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/Argument.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Constant.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InstrTypes.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/IR/PatternMatch.h"
+#include "llvm/IR/Type.h"
+#include "llvm/IR/User.h"
+#include "llvm/IR/Value.h"
+#include "llvm/IR/ValueHandle.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include <algorithm>
+#include <cassert>
+#include <utility>
+
+using namespace llvm;
+using namespace reassociate;
+using namespace PatternMatch;
+
+#define DEBUG_TYPE "reassociate"
+
+STATISTIC(NumChanged, "Number of insts reassociated");
+STATISTIC(NumAnnihil, "Number of expr tree annihilated");
+STATISTIC(NumFactor , "Number of multiplies factored");
+
+static cl::opt<bool>
+ UseCSELocalOpt(DEBUG_TYPE "-use-cse-local",
+ cl::desc("Only reorder expressions within a basic block "
+ "when exposing CSE opportunities"),
+ cl::init(true), cl::Hidden);
+
+#ifndef NDEBUG
+/// Print out the expression identified in the Ops list.
+static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
+ Module *M = I->getModule();
+ dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
+ << *Ops[0].Op->getType() << '\t';
+ for (const ValueEntry &Op : Ops) {
+ dbgs() << "[ ";
+ Op.Op->printAsOperand(dbgs(), false, M);
+ dbgs() << ", #" << Op.Rank << "] ";
+ }
+}
+#endif
+
+/// Utility class representing a non-constant Xor-operand. We classify
+/// non-constant Xor-Operands into two categories:
+/// C1) The operand is in the form "X & C", where C is a constant and C != ~0
+/// C2)
+/// C2.1) The operand is in the form of "X | C", where C is a non-zero
+/// constant.
+/// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
+/// operand as "E | 0"
+class llvm::reassociate::XorOpnd {
+public:
+ XorOpnd(Value *V);
+
+ bool isInvalid() const { return SymbolicPart == nullptr; }
+ bool isOrExpr() const { return isOr; }
+ Value *getValue() const { return OrigVal; }
+ Value *getSymbolicPart() const { return SymbolicPart; }
+ unsigned getSymbolicRank() const { return SymbolicRank; }
+ const APInt &getConstPart() const { return ConstPart; }
+
+ void Invalidate() { SymbolicPart = OrigVal = nullptr; }
+ void setSymbolicRank(unsigned R) { SymbolicRank = R; }
+
+private:
+ Value *OrigVal;
+ Value *SymbolicPart;
+ APInt ConstPart;
+ unsigned SymbolicRank;
+ bool isOr;
+};
+
+XorOpnd::XorOpnd(Value *V) {
+ assert(!isa<ConstantInt>(V) && "No ConstantInt");
+ OrigVal = V;
+ Instruction *I = dyn_cast<Instruction>(V);
+ SymbolicRank = 0;
+
+ if (I && (I->getOpcode() == Instruction::Or ||
+ I->getOpcode() == Instruction::And)) {
+ Value *V0 = I->getOperand(0);
+ Value *V1 = I->getOperand(1);
+ const APInt *C;
+ if (match(V0, m_APInt(C)))
+ std::swap(V0, V1);
+
+ if (match(V1, m_APInt(C))) {
+ ConstPart = *C;
+ SymbolicPart = V0;
+ isOr = (I->getOpcode() == Instruction::Or);
+ return;
+ }
+ }
+
+ // view the operand as "V | 0"
+ SymbolicPart = V;
+ ConstPart = APInt::getZero(V->getType()->getScalarSizeInBits());
+ isOr = true;
+}
+
+/// Return true if I is an instruction with the FastMathFlags that are needed
+/// for general reassociation set. This is not the same as testing
+/// Instruction::isAssociative() because it includes operations like fsub.
+/// (This routine is only intended to be called for floating-point operations.)
+static bool hasFPAssociativeFlags(Instruction *I) {
+ assert(I && isa<FPMathOperator>(I) && "Should only check FP ops");
+ return I->hasAllowReassoc() && I->hasNoSignedZeros();
+}
+
+/// Return true if V is an instruction of the specified opcode and if it
+/// only has one use.
+static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
+ auto *BO = dyn_cast<BinaryOperator>(V);
+ if (BO && BO->hasOneUse() && BO->getOpcode() == Opcode)
+ if (!isa<FPMathOperator>(BO) || hasFPAssociativeFlags(BO))
+ return BO;
+ return nullptr;
+}
+
+static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1,
+ unsigned Opcode2) {
+ auto *BO = dyn_cast<BinaryOperator>(V);
+ if (BO && BO->hasOneUse() &&
+ (BO->getOpcode() == Opcode1 || BO->getOpcode() == Opcode2))
+ if (!isa<FPMathOperator>(BO) || hasFPAssociativeFlags(BO))
+ return BO;
+ return nullptr;
+}
+
+void ReassociatePass::BuildRankMap(Function &F,
+ ReversePostOrderTraversal<Function*> &RPOT) {
+ unsigned Rank = 2;
+
+ // Assign distinct ranks to function arguments.
+ for (auto &Arg : F.args()) {
+ ValueRankMap[&Arg] = ++Rank;
+ LLVM_DEBUG(dbgs() << "Calculated Rank[" << Arg.getName() << "] = " << Rank
+ << "\n");
+ }
+
+ // Traverse basic blocks in ReversePostOrder.
+ for (BasicBlock *BB : RPOT) {
+ unsigned BBRank = RankMap[BB] = ++Rank << 16;
+
+ // Walk the basic block, adding precomputed ranks for any instructions that
+ // we cannot move. This ensures that the ranks for these instructions are
+ // all different in the block.
+ for (Instruction &I : *BB)
+ if (mayHaveNonDefUseDependency(I))
+ ValueRankMap[&I] = ++BBRank;
+ }
+}
+
+unsigned ReassociatePass::getRank(Value *V) {
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (!I) {
+ if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
+ return 0; // Otherwise it's a global or constant, rank 0.
+ }
+
+ if (unsigned Rank = ValueRankMap[I])
+ return Rank; // Rank already known?
+
+ // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
+ // we can reassociate expressions for code motion! Since we do not recurse
+ // for PHI nodes, we cannot have infinite recursion here, because there
+ // cannot be loops in the value graph that do not go through PHI nodes.
+ unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
+ for (unsigned i = 0, e = I->getNumOperands(); i != e && Rank != MaxRank; ++i)
+ Rank = std::max(Rank, getRank(I->getOperand(i)));
+
+ // If this is a 'not' or 'neg' instruction, do not count it for rank. This
+ // assures us that X and ~X will have the same rank.
+ if (!match(I, m_Not(m_Value())) && !match(I, m_Neg(m_Value())) &&
+ !match(I, m_FNeg(m_Value())))
+ ++Rank;
+
+ LLVM_DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " << Rank
+ << "\n");
+
+ return ValueRankMap[I] = Rank;
+}
+
+// Canonicalize constants to RHS. Otherwise, sort the operands by rank.
+void ReassociatePass::canonicalizeOperands(Instruction *I) {
+ assert(isa<BinaryOperator>(I) && "Expected binary operator.");
+ assert(I->isCommutative() && "Expected commutative operator.");
+
+ Value *LHS = I->getOperand(0);
+ Value *RHS = I->getOperand(1);
+ if (LHS == RHS || isa<Constant>(RHS))
+ return;
+ if (isa<Constant>(LHS) || getRank(RHS) < getRank(LHS)) {
+ cast<BinaryOperator>(I)->swapOperands();
+ MadeChange = true;
+ }
+}
+
+static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name,
+ BasicBlock::iterator InsertBefore,
+ Value *FlagsOp) {
+ if (S1->getType()->isIntOrIntVectorTy())
+ return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore);
+ else {
+ BinaryOperator *Res =
+ BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore);
+ Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
+ return Res;
+ }
+}
+
+static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name,
+ BasicBlock::iterator InsertBefore,
+ Value *FlagsOp) {
+ if (S1->getType()->isIntOrIntVectorTy())
+ return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore);
+ else {
+ BinaryOperator *Res =
+ BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore);
+ Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
+ return Res;
+ }
+}
+
+static Instruction *CreateNeg(Value *S1, const Twine &Name,
+ BasicBlock::iterator InsertBefore,
+ Value *FlagsOp) {
+ if (S1->getType()->isIntOrIntVectorTy())
+ return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
+
+ if (auto *FMFSource = dyn_cast<Instruction>(FlagsOp))
+ return UnaryOperator::CreateFNegFMF(S1, FMFSource, Name, InsertBefore);
+
+ return UnaryOperator::CreateFNeg(S1, Name, InsertBefore);
+}
+
+/// Replace 0-X with X*-1.
+static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) {
+ assert((isa<UnaryOperator>(Neg) || isa<BinaryOperator>(Neg)) &&
+ "Expected a Negate!");
+ // FIXME: It's not safe to lower a unary FNeg into a FMul by -1.0.
+ unsigned OpNo = isa<BinaryOperator>(Neg) ? 1 : 0;
+ Type *Ty = Neg->getType();
+ Constant *NegOne = Ty->isIntOrIntVectorTy() ?
+ ConstantInt::getAllOnesValue(Ty) : ConstantFP::get(Ty, -1.0);
+
+ BinaryOperator *Res =
+ CreateMul(Neg->getOperand(OpNo), NegOne, "", Neg->getIterator(), Neg);
+ Neg->setOperand(OpNo, Constant::getNullValue(Ty)); // Drop use of op.
+ Res->takeName(Neg);
+ Neg->replaceAllUsesWith(Res);
+ Res->setDebugLoc(Neg->getDebugLoc());
+ return Res;
+}
+
+using RepeatedValue = std::pair<Value *, uint64_t>;
+
+/// Given an associative binary expression, return the leaf
+/// nodes in Ops along with their weights (how many times the leaf occurs). The
+/// original expression is the same as
+/// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
+/// op
+/// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
+/// op
+/// ...
+/// op
+/// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
+///
+/// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
+///
+/// This routine may modify the function, in which case it returns 'true'. The
+/// changes it makes may well be destructive, changing the value computed by 'I'
+/// to something completely different. Thus if the routine returns 'true' then
+/// you MUST either replace I with a new expression computed from the Ops array,
+/// or use RewriteExprTree to put the values back in.
+///
+/// A leaf node is either not a binary operation of the same kind as the root
+/// node 'I' (i.e. is not a binary operator at all, or is, but with a different
+/// opcode), or is the same kind of binary operator but has a use which either
+/// does not belong to the expression, or does belong to the expression but is
+/// a leaf node. Every leaf node has at least one use that is a non-leaf node
+/// of the expression, while for non-leaf nodes (except for the root 'I') every
+/// use is a non-leaf node of the expression.
+///
+/// For example:
+/// expression graph node names
+///
+/// + | I
+/// / \ |
+/// + + | A, B
+/// / \ / \ |
+/// * + * | C, D, E
+/// / \ / \ / \ |
+/// + * | F, G
+///
+/// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
+/// that order) (C, 1), (E, 1), (F, 2), (G, 2).
+///
+/// The expression is maximal: if some instruction is a binary operator of the
+/// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
+/// then the instruction also belongs to the expression, is not a leaf node of
+/// it, and its operands also belong to the expression (but may be leaf nodes).
+///
+/// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
+/// order to ensure that every non-root node in the expression has *exactly one*
+/// use by a non-leaf node of the expression. This destruction means that the
+/// caller MUST either replace 'I' with a new expression or use something like
+/// RewriteExprTree to put the values back in if the routine indicates that it
+/// made a change by returning 'true'.
+///
+/// In the above example either the right operand of A or the left operand of B
+/// will be replaced by undef. If it is B's operand then this gives:
+///
+/// + | I
+/// / \ |
+/// + + | A, B - operand of B replaced with undef
+/// / \ \ |
+/// * + * | C, D, E
+/// / \ / \ / \ |
+/// + * | F, G
+///
+/// Note that such undef operands can only be reached by passing through 'I'.
+/// For example, if you visit operands recursively starting from a leaf node
+/// then you will never see such an undef operand unless you get back to 'I',
+/// which requires passing through a phi node.
+///
+/// Note that this routine may also mutate binary operators of the wrong type
+/// that have all uses inside the expression (i.e. only used by non-leaf nodes
+/// of the expression) if it can turn them into binary operators of the right
+/// type and thus make the expression bigger.
+static bool LinearizeExprTree(Instruction *I,
+ SmallVectorImpl<RepeatedValue> &Ops,
+ ReassociatePass::OrderedSet &ToRedo,
+ OverflowTracking &Flags) {
+ assert((isa<UnaryOperator>(I) || isa<BinaryOperator>(I)) &&
+ "Expected a UnaryOperator or BinaryOperator!");
+ LLVM_DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
+ unsigned Opcode = I->getOpcode();
+ assert(I->isAssociative() && I->isCommutative() &&
+ "Expected an associative and commutative operation!");
+
+ // Visit all operands of the expression, keeping track of their weight (the
+ // number of paths from the expression root to the operand, or if you like
+ // the number of times that operand occurs in the linearized expression).
+ // For example, if I = X + A, where X = A + B, then I, X and B have weight 1
+ // while A has weight two.
+
+ // Worklist of non-leaf nodes (their operands are in the expression too) along
+ // with their weights, representing a certain number of paths to the operator.
+ // If an operator occurs in the worklist multiple times then we found multiple
+ // ways to get to it.
+ SmallVector<std::pair<Instruction *, uint64_t>, 8> Worklist; // (Op, Weight)
+ Worklist.push_back(std::make_pair(I, 1));
+ bool Changed = false;
+
+ // Leaves of the expression are values that either aren't the right kind of
+ // operation (eg: a constant, or a multiply in an add tree), or are, but have
+ // some uses that are not inside the expression. For example, in I = X + X,
+ // X = A + B, the value X has two uses (by I) that are in the expression. If
+ // X has any other uses, for example in a return instruction, then we consider
+ // X to be a leaf, and won't analyze it further. When we first visit a value,
+ // if it has more than one use then at first we conservatively consider it to
+ // be a leaf. Later, as the expression is explored, we may discover some more
+ // uses of the value from inside the expression. If all uses turn out to be
+ // from within the expression (and the value is a binary operator of the right
+ // kind) then the value is no longer considered to be a leaf, and its operands
+ // are explored.
+
+ // Leaves - Keeps track of the set of putative leaves as well as the number of
+ // paths to each leaf seen so far.
+ using LeafMap = DenseMap<Value *, uint64_t>;
+ LeafMap Leaves; // Leaf -> Total weight so far.
+ SmallVector<Value *, 8> LeafOrder; // Ensure deterministic leaf output order.
+ const DataLayout &DL = I->getDataLayout();
+
+#ifndef NDEBUG
+ SmallPtrSet<Value *, 8> Visited; // For checking the iteration scheme.
+#endif
+ while (!Worklist.empty()) {
+ // We examine the operands of this binary operator.
+ auto [I, Weight] = Worklist.pop_back_val();
+
+ Flags.mergeFlags(*I);
+
+ for (unsigned OpIdx = 0; OpIdx < I->getNumOperands(); ++OpIdx) { // Visit operands.
+ Value *Op = I->getOperand(OpIdx);
+ LLVM_DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n");
+ assert((!Op->hasUseList() || !Op->use_empty()) &&
+ "No uses, so how did we get to it?!");
+
+ // If this is a binary operation of the right kind with only one use then
+ // add its operands to the expression.
+ if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
+ assert(Visited.insert(Op).second && "Not first visit!");
+ LLVM_DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n");
+ Worklist.push_back(std::make_pair(BO, Weight));
+ continue;
+ }
+
+ // Appears to be a leaf. Is the operand already in the set of leaves?
+ LeafMap::iterator It = Leaves.find(Op);
+ if (It == Leaves.end()) {
+ // Not in the leaf map. Must be the first time we saw this operand.
+ assert(Visited.insert(Op).second && "Not first visit!");
+ if (!Op->hasOneUse()) {
+ // This value has uses not accounted for by the expression, so it is
+ // not safe to modify. Mark it as being a leaf.
+ LLVM_DEBUG(dbgs()
+ << "ADD USES LEAF: " << *Op << " (" << Weight << ")\n");
+ LeafOrder.push_back(Op);
+ Leaves[Op] = Weight;
+ continue;
+ }
+ // No uses outside the expression, try morphing it.
+ } else {
+ // Already in the leaf map.
+ assert(It != Leaves.end() && Visited.count(Op) &&
+ "In leaf map but not visited!");
+
+ // Update the number of paths to the leaf.
+ It->second += Weight;
+ assert(It->second >= Weight && "Weight overflows");
+
+ // If we still have uses that are not accounted for by the expression
+ // then it is not safe to modify the value.
+ if (!Op->hasOneUse())
+ continue;
+
+ // No uses outside the expression, try morphing it.
+ Weight = It->second;
+ Leaves.erase(It); // Since the value may be morphed below.
+ }
+
+ // At this point we have a value which, first of all, is not a binary
+ // expression of the right kind, and secondly, is only used inside the
+ // expression. This means that it can safely be modified. See if we
+ // can usefully morph it into an expression of the right kind.
+ assert((!isa<Instruction>(Op) ||
+ cast<Instruction>(Op)->getOpcode() != Opcode
+ || (isa<FPMathOperator>(Op) &&
+ !hasFPAssociativeFlags(cast<Instruction>(Op)))) &&
+ "Should have been handled above!");
+ assert(Op->hasOneUse() && "Has uses outside the expression tree!");
+
+ // If this is a multiply expression, turn any internal negations into
+ // multiplies by -1 so they can be reassociated. Add any users of the
+ // newly created multiplication by -1 to the redo list, so any
+ // reassociation opportunities that are exposed will be reassociated
+ // further.
+ Instruction *Neg;
+ if (((Opcode == Instruction::Mul && match(Op, m_Neg(m_Value()))) ||
+ (Opcode == Instruction::FMul && match(Op, m_FNeg(m_Value())))) &&
+ match(Op, m_Instruction(Neg))) {
+ LLVM_DEBUG(dbgs()
+ << "MORPH LEAF: " << *Op << " (" << Weight << ") TO ");
+ Instruction *Mul = LowerNegateToMultiply(Neg);
+ LLVM_DEBUG(dbgs() << *Mul << '\n');
+ Worklist.push_back(std::make_pair(Mul, Weight));
+ for (User *U : Mul->users()) {
+ if (BinaryOperator *UserBO = dyn_cast<BinaryOperator>(U))
+ ToRedo.insert(UserBO);
+ }
+ ToRedo.insert(Neg);
+ Changed = true;
+ continue;
+ }
+
+ // Failed to morph into an expression of the right type. This really is
+ // a leaf.
+ LLVM_DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n");
+ assert(!isReassociableOp(Op, Opcode) && "Value was morphed?");
+ LeafOrder.push_back(Op);
+ Leaves[Op] = Weight;
+ }
+ }
+
+ // The leaves, repeated according to their weights, represent the linearized
+ // form of the expression.
+ for (Value *V : LeafOrder) {
+ LeafMap::iterator It = Leaves.find(V);
+ if (It == Leaves.end())
+ // Node initially thought to be a leaf wasn't.
+ continue;
+ assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!");
+ uint64_t Weight = It->second;
+ // Ensure the leaf is only output once.
+ It->second = 0;
+ Ops.push_back(std::make_pair(V, Weight));
+ if (Opcode == Instruction::Add && Flags.AllKnownNonNegative && Flags.HasNSW)
+ Flags.AllKnownNonNegative &= isKnownNonNegative(V, SimplifyQuery(DL));
+ else if (Opcode == Instruction::Mul) {
+ // To preserve NUW we need all inputs non-zero.
+ // To preserve NSW we need all inputs strictly positive.
+ if (Flags.AllKnownNonZero &&
+ (Flags.HasNUW || (Flags.HasNSW && Flags.AllKnownNonNegative))) {
+ Flags.AllKnownNonZero &= isKnownNonZero(V, SimplifyQuery(DL));
+ if (Flags.HasNSW && Flags.AllKnownNonNegative)
+ Flags.AllKnownNonNegative &= isKnownNonNegative(V, SimplifyQuery(DL));
+ }
+ }
+ }
+
+ // For nilpotent operations or addition there may be no operands, for example
+ // because the expression was "X xor X" or consisted of 2^Bitwidth additions:
+ // in both cases the weight reduces to 0 causing the value to be skipped.
+ if (Ops.empty()) {
+ Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
+ assert(Identity && "Associative operation without identity!");
+ Ops.emplace_back(Identity, 1);
+ }
+
+ return Changed;
+}
+
+/// Now that the operands for this expression tree are
+/// linearized and optimized, emit them in-order.
+void ReassociatePass::RewriteExprTree(BinaryOperator *I,
+ SmallVectorImpl<ValueEntry> &Ops,
+ OverflowTracking Flags) {
+ assert(Ops.size() > 1 && "Single values should be used directly!");
+
+ // Since our optimizations should never increase the number of operations, the
+ // new expression can usually be written reusing the existing binary operators
+ // from the original expression tree, without creating any new instructions,
+ // though the rewritten expression may have a completely different topology.
+ // We take care to not change anything if the new expression will be the same
+ // as the original. If more than trivial changes (like commuting operands)
+ // were made then we are obliged to clear out any optional subclass data like
+ // nsw flags.
+
+ /// NodesToRewrite - Nodes from the original expression available for writing
+ /// the new expression into.
+ SmallVector<BinaryOperator*, 8> NodesToRewrite;
+ unsigned Opcode = I->getOpcode();
+ BinaryOperator *Op = I;
+
+ /// NotRewritable - The operands being written will be the leaves of the new
+ /// expression and must not be used as inner nodes (via NodesToRewrite) by
+ /// mistake. Inner nodes are always reassociable, and usually leaves are not
+ /// (if they were they would have been incorporated into the expression and so
+ /// would not be leaves), so most of the time there is no danger of this. But
+ /// in rare cases a leaf may become reassociable if an optimization kills uses
+ /// of it, or it may momentarily become reassociable during rewriting (below)
+ /// due it being removed as an operand of one of its uses. Ensure that misuse
+ /// of leaf nodes as inner nodes cannot occur by remembering all of the future
+ /// leaves and refusing to reuse any of them as inner nodes.
+ SmallPtrSet<Value*, 8> NotRewritable;
+ for (const ValueEntry &Op : Ops)
+ NotRewritable.insert(Op.Op);
+
+ // ExpressionChangedStart - Non-null if the rewritten expression differs from
+ // the original in some non-trivial way, requiring the clearing of optional
+ // flags. Flags are cleared from the operator in ExpressionChangedStart up to
+ // ExpressionChangedEnd inclusive.
+ BinaryOperator *ExpressionChangedStart = nullptr,
+ *ExpressionChangedEnd = nullptr;
+ for (unsigned i = 0; ; ++i) {
+ // The last operation (which comes earliest in the IR) is special as both
+ // operands will come from Ops, rather than just one with the other being
+ // a subexpression.
+ if (i+2 == Ops.size()) {
+ Value *NewLHS = Ops[i].Op;
+ Value *NewRHS = Ops[i+1].Op;
+ Value *OldLHS = Op->getOperand(0);
+ Value *OldRHS = Op->getOperand(1);
+
+ if (NewLHS == OldLHS && NewRHS == OldRHS)
+ // Nothing changed, leave it alone.
+ break;
+
+ if (NewLHS == OldRHS && NewRHS == OldLHS) {
+ // The order of the operands was reversed. Swap them.
+ LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
+ Op->swapOperands();
+ LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
+ MadeChange = true;
+ ++NumChanged;
+ break;
+ }
+
+ // The new operation differs non-trivially from the original. Overwrite
+ // the old operands with the new ones.
+ LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
+ if (NewLHS != OldLHS) {
+ BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
+ if (BO && !NotRewritable.count(BO))
+ NodesToRewrite.push_back(BO);
+ salvageDebugInfo(*Op);
+ Op->setOperand(0, NewLHS);
+ }
+ if (NewRHS != OldRHS) {
+ BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
+ if (BO && !NotRewritable.count(BO))
+ NodesToRewrite.push_back(BO);
+ salvageDebugInfo(*Op);
+ Op->setOperand(1, NewRHS);
+ }
+ LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
+
+ ExpressionChangedStart = Op;
+ if (!ExpressionChangedEnd)
+ ExpressionChangedEnd = Op;
+ MadeChange = true;
+ ++NumChanged;
+
+ break;
+ }
+
+ // Not the last operation. The left-hand side will be a sub-expression
+ // while the right-hand side will be the current element of Ops.
+ Value *NewRHS = Ops[i].Op;
+ if (NewRHS != Op->getOperand(1)) {
+ LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
+ if (NewRHS == Op->getOperand(0)) {
+ // The new right-hand side was already present as the left operand. If
+ // we are lucky then swapping the operands will sort out both of them.
+ Op->swapOperands();
+ } else {
+ // Overwrite with the new right-hand side.
+ BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
+ if (BO && !NotRewritable.count(BO))
+ NodesToRewrite.push_back(BO);
+ salvageDebugInfo(*Op);
+ Op->setOperand(1, NewRHS);
+ ExpressionChangedStart = Op;
+ if (!ExpressionChangedEnd)
+ ExpressionChangedEnd = Op;
+ }
+ LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
+ MadeChange = true;
+ ++NumChanged;
+ }
+
+ // Now deal with the left-hand side. If this is already an operation node
+ // from the original expression then just rewrite the rest of the expression
+ // into it.
+ BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode);
+ if (BO && !NotRewritable.count(BO)) {
+ Op = BO;
+ continue;
+ }
+
+ // Otherwise, grab a spare node from the original expression and use that as
+ // the left-hand side. If there are no nodes left then the optimizers made
+ // an expression with more nodes than the original! This usually means that
+ // they did something stupid but it might mean that the problem was just too
+ // hard (finding the mimimal number of multiplications needed to realize a
+ // multiplication expression is NP-complete). Whatever the reason, smart or
+ // stupid, create a new node if there are none left.
+ BinaryOperator *NewOp;
+ if (NodesToRewrite.empty()) {
+ Constant *Poison = PoisonValue::get(I->getType());
+ NewOp = BinaryOperator::Create(Instruction::BinaryOps(Opcode), Poison,
+ Poison, "", I->getIterator());
+ if (isa<FPMathOperator>(NewOp))
+ NewOp->setFastMathFlags(I->getFastMathFlags());
+ } else {
+ NewOp = NodesToRewrite.pop_back_val();
+ }
+
+ LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n');
+ salvageDebugInfo(*Op);
+ Op->setOperand(0, NewOp);
+ LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n');
+ ExpressionChangedStart = Op;
+ if (!ExpressionChangedEnd)
+ ExpressionChangedEnd = Op;
+ MadeChange = true;
+ ++NumChanged;
+ Op = NewOp;
+ }
+
+ // If the expression changed non-trivially then clear out all subclass data
+ // starting from the operator specified in ExpressionChanged, and compactify
+ // the operators to just before the expression root to guarantee that the
+ // expression tree is dominated by all of Ops.
+ if (ExpressionChangedStart) {
+ bool ClearFlags = true;
+ do {
+ // Preserve flags.
+ if (ClearFlags) {
+ if (isa<FPMathOperator>(I)) {
+ FastMathFlags Flags = I->getFastMathFlags();
+ ExpressionChangedStart->clearSubclassOptionalData();
+ ExpressionChangedStart->setFastMathFlags(Flags);
+ } else {
+ Flags.applyFlags(*ExpressionChangedStart);
+ }
+ }
+
+ if (ExpressionChangedStart == ExpressionChangedEnd)
+ ClearFlags = false;
+ if (ExpressionChangedStart == I)
+ break;
+
+ ExpressionChangedStart->moveBefore(I->getIterator());
+ ExpressionChangedStart =
+ cast<BinaryOperator>(*ExpressionChangedStart->user_begin());
+ } while (true);
+ }
+
+ // Throw away any left over nodes from the original expression.
+ RedoInsts.insert_range(NodesToRewrite);
+}
+
+/// Insert instructions before the instruction pointed to by BI,
+/// that computes the negative version of the value specified. The negative
+/// version of the value is returned, and BI is left pointing at the instruction
+/// that should be processed next by the reassociation pass.
+/// Also add intermediate instructions to the redo list that are modified while
+/// pushing the negates through adds. These will be revisited to see if
+/// additional opportunities have been exposed.
+static Value *NegateValue(Value *V, Instruction *BI,
+ ReassociatePass::OrderedSet &ToRedo) {
+ if (auto *C = dyn_cast<Constant>(V)) {
+ const DataLayout &DL = BI->getDataLayout();
+ Constant *Res = C->getType()->isFPOrFPVectorTy()
+ ? ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)
+ : ConstantExpr::getNeg(C);
+ if (Res)
+ return Res;
+ }
+
+ // We are trying to expose opportunity for reassociation. One of the things
+ // that we want to do to achieve this is to push a negation as deep into an
+ // expression chain as possible, to expose the add instructions. In practice,
+ // this means that we turn this:
+ // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
+ // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
+ // the constants. We assume that instcombine will clean up the mess later if
+ // we introduce tons of unnecessary negation instructions.
+ //
+ if (BinaryOperator *I =
+ isReassociableOp(V, Instruction::Add, Instruction::FAdd)) {
+ // Push the negates through the add.
+ I->setOperand(0, NegateValue(I->getOperand(0), BI, ToRedo));
+ I->setOperand(1, NegateValue(I->getOperand(1), BI, ToRedo));
+ if (I->getOpcode() == Instruction::Add) {
+ I->setHasNoUnsignedWrap(false);
+ I->setHasNoSignedWrap(false);
+ }
+
+ // We must move the add instruction here, because the neg instructions do
+ // not dominate the old add instruction in general. By moving it, we are
+ // assured that the neg instructions we just inserted dominate the
+ // instruction we are about to insert after them.
+ //
+ I->moveBefore(BI->getIterator());
+ I->setName(I->getName()+".neg");
+
+ // Add the intermediate negates to the redo list as processing them later
+ // could expose more reassociating opportunities.
+ ToRedo.insert(I);
+ return I;
+ }
+
+ // Okay, we need to materialize a negated version of V with an instruction.
+ // Scan the use lists of V to see if we have one already.
+ for (User *U : V->users()) {
+ if (!match(U, m_Neg(m_Value())) && !match(U, m_FNeg(m_Value())))
+ continue;
+
+ // We found one! Now we have to make sure that the definition dominates
+ // this use. We do this by moving it to the entry block (if it is a
+ // non-instruction value) or right after the definition. These negates will
+ // be zapped by reassociate later, so we don't need much finesse here.
+ Instruction *TheNeg = dyn_cast<Instruction>(U);
+
+ // We can't safely propagate a vector zero constant with poison/undef lanes.
+ Constant *C;
+ if (match(TheNeg, m_BinOp(m_Constant(C), m_Value())) &&
+ C->containsUndefOrPoisonElement())
+ continue;
+
+ // Verify that the negate is in this function, V might be a constant expr.
+ if (!TheNeg ||
+ TheNeg->getParent()->getParent() != BI->getParent()->getParent())
+ continue;
+
+ BasicBlock::iterator InsertPt;
+ if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
+ auto InsertPtOpt = InstInput->getInsertionPointAfterDef();
+ if (!InsertPtOpt)
+ continue;
+ InsertPt = *InsertPtOpt;
+ } else {
+ InsertPt = TheNeg->getFunction()
+ ->getEntryBlock()
+ .getFirstNonPHIOrDbg()
+ ->getIterator();
+ }
+
+ // Check that if TheNeg is moved out of its parent block, we drop its
+ // debug location to avoid extra coverage.
+ // See test dropping_debugloc_the_neg.ll for a detailed example.
+ if (TheNeg->getParent() != InsertPt->getParent())
+ TheNeg->dropLocation();
+ TheNeg->moveBefore(*InsertPt->getParent(), InsertPt);
+
+ if (TheNeg->getOpcode() == Instruction::Sub) {
+ TheNeg->setHasNoUnsignedWrap(false);
+ TheNeg->setHasNoSignedWrap(false);
+ } else {
+ TheNeg->andIRFlags(BI);
+ }
+ ToRedo.insert(TheNeg);
+ return TheNeg;
+ }
+
+ // Insert a 'neg' instruction that subtracts the value from zero to get the
+ // negation.
+ Instruction *NewNeg =
+ CreateNeg(V, V->getName() + ".neg", BI->getIterator(), BI);
+ // NewNeg is generated to potentially replace BI, so use its DebugLoc.
+ NewNeg->setDebugLoc(BI->getDebugLoc());
+ ToRedo.insert(NewNeg);
+ return NewNeg;
+}
+
+// See if this `or` looks like an load widening reduction, i.e. that it
+// consists of an `or`/`shl`/`zext`/`load` nodes only. Note that we don't
+// ensure that the pattern is *really* a load widening reduction,
+// we do not ensure that it can really be replaced with a widened load,
+// only that it mostly looks like one.
+static bool isLoadCombineCandidate(Instruction *Or) {
+ SmallVector<Instruction *, 8> Worklist;
+ SmallPtrSet<Instruction *, 8> Visited;
+
+ auto Enqueue = [&](Value *V) {
+ auto *I = dyn_cast<Instruction>(V);
+ // Each node of an `or` reduction must be an instruction,
+ if (!I)
+ return false; // Node is certainly not part of an `or` load reduction.
+ // Only process instructions we have never processed before.
+ if (Visited.insert(I).second)
+ Worklist.emplace_back(I);
+ return true; // Will need to look at parent nodes.
+ };
+
+ if (!Enqueue(Or))
+ return false; // Not an `or` reduction pattern.
+
+ while (!Worklist.empty()) {
+ auto *I = Worklist.pop_back_val();
+
+ // Okay, which instruction is this node?
+ switch (I->getOpcode()) {
+ case Instruction::Or:
+ // Got an `or` node. That's fine, just recurse into it's operands.
+ for (Value *Op : I->operands())
+ if (!Enqueue(Op))
+ return false; // Not an `or` reduction pattern.
+ continue;
+
+ case Instruction::Shl:
+ case Instruction::ZExt:
+ // `shl`/`zext` nodes are fine, just recurse into their base operand.
+ if (!Enqueue(I->getOperand(0)))
+ return false; // Not an `or` reduction pattern.
+ continue;
+
+ case Instruction::Load:
+ // Perfect, `load` node means we've reached an edge of the graph.
+ continue;
+
+ default: // Unknown node.
+ return false; // Not an `or` reduction pattern.
+ }
+ }
+
+ return true;
+}
+
+/// Return true if it may be profitable to convert this (X|Y) into (X+Y).
+static bool shouldConvertOrWithNoCommonBitsToAdd(Instruction *Or) {
+ // Don't bother to convert this up unless either the LHS is an associable add
+ // or subtract or mul or if this is only used by one of the above.
+ // This is only a compile-time improvement, it is not needed for correctness!
+ auto isInteresting = [](Value *V) {
+ for (auto Op : {Instruction::Add, Instruction::Sub, Instruction::Mul,
+ Instruction::Shl})
+ if (isReassociableOp(V, Op))
return true;
-
- }
- return false;
-}
-
-/// Distribute Mul of the form (X+Y)*C into X*C + Y*C.
-/// For the sub case (X-Y)*C, the second term uses -C to avoid
-/// introducing a negation instruction.
-static BinaryOperator *BreakUpDistribute(Instruction *Mul,
- ReassociatePass::OrderedSet &ToRedo) {
-
- Instruction *AddSub = cast<Instruction>(Mul->getOperand(0));
- Constant *C = cast<Constant>(Mul->getOperand(1));
+ return false;
+ };
+
+ if (any_of(Or->operands(), isInteresting))
+ return true;
+
+ Value *VB = Or->user_back();
+ if (Or->hasOneUse() && isInteresting(VB))
+ return true;
+
+ return false;
+}
+
+/// If we have (X|Y), and iff X and Y have no common bits set,
+/// transform this into (X+Y) to allow arithmetics reassociation.
+static BinaryOperator *convertOrWithNoCommonBitsToAdd(Instruction *Or) {
+ // Convert an or into an add.
+ BinaryOperator *New = CreateAdd(Or->getOperand(0), Or->getOperand(1), "",
+ Or->getIterator(), Or);
+ New->setHasNoSignedWrap();
+ New->setHasNoUnsignedWrap();
+ New->takeName(Or);
+
+ // Everyone now refers to the add instruction.
+ Or->replaceAllUsesWith(New);
+ New->setDebugLoc(Or->getDebugLoc());
+
+ LLVM_DEBUG(dbgs() << "Converted or into an add: " << *New << '\n');
+ return New;
+}
+
+/// Return true if Mul is of the form (X+Y)*C or (X-Y)*C where C is a
+/// constant, and there exists a sibling instruction of the form X*C' or Y*C'
+/// in the same expression — indicating that distribution followed by
+/// factoring will reduce the instruction count.
+static bool ShouldBreakUpDistribution(Instruction *Mul) {
+ Value *A, *B;
+ if (!match(Mul, m_c_Mul(m_OneUse(m_CombineOr(m_Add(m_Value(A), m_Value(B)),
+ m_Sub(m_Value(A), m_Value(B)))),
+ m_ImmConstant())))
+ return false;
+
+ auto *MulUser = dyn_cast<Instruction>(Mul->user_back());
+ // The parent MUST be an Add or Sub to ensure the tree is flattened
+ if (!MulUser || (MulUser->getOpcode() != Instruction::Add &&
+ MulUser->getOpcode() != Instruction::Sub))
+ return false;
+
+ for (Value *Sibling : MulUser->operands()) {
+ if (Sibling == Mul || !Sibling->hasOneUse())
+ continue;
+
+ // Sibling must be NonConst * C'.
+ Value *SibNC;
+ if (match(Sibling, m_Mul(m_Value(SibNC), m_Constant())) &&
+ (SibNC == A || SibNC == B) && !isa<Constant>(SibNC))
+ return true;
+ }
+ return false;
+}
+
+/// Distribute Mul of the form (X+Y)*C into X*C + Y*C.
+/// For the sub case (X-Y)*C, the second term uses -C to avoid
+/// introducing a negation instruction.
+static BinaryOperator *BreakUpDistribute(Instruction *Mul,
+ ReassociatePass::OrderedSet &ToRedo) {
+
+ Instruction *AddSub = cast<Instruction>(Mul->getOperand(0));
+ Constant *C = cast<Constant>(Mul->getOperand(1));
Constant *C2 = AddSub->getOpcode() == Instruction::Sub
- ? cast<Constant>(ConstantExpr::getNeg(C))
- : C;
-
- BinaryOperator *M1 =
- BinaryOperator::CreateMul(AddSub->getOperand(0), C, "Mul1", Mul->getIterator());
- BinaryOperator *M2 =
- BinaryOperator::CreateMul(AddSub->getOperand(1), C2, "Mul2", Mul->getIterator());
- BinaryOperator *Result;
- Result = BinaryOperator::CreateAdd(M1, M2, "DistAdd", Mul->getIterator());
-
- Mul->replaceAllUsesWith(Result);
- Result->setDebugLoc(Mul->getDebugLoc());
-
- ToRedo.insert(M1);
- ToRedo.insert(M2);
- ToRedo.insert(Result);
-
- return Result;
-}
-
-/// Return true if we should break up this subtract of X-Y into (X + -Y).
-static bool ShouldBreakUpSubtract(Instruction *Sub) {
- // If this is a negation, we can't split it up!
- if (match(Sub, m_Neg(m_Value())) || match(Sub, m_FNeg(m_Value())))
- return false;
-
- // Don't breakup X - undef.
- if (isa<UndefValue>(Sub->getOperand(1)))
- return false;
-
- // Don't bother to break this up unless either the LHS is an associable add or
- // subtract or if this is only used by one.
- Value *V0 = Sub->getOperand(0);
- if (isReassociableOp(V0, Instruction::Add, Instruction::FAdd) ||
- isReassociableOp(V0, Instruction::Sub, Instruction::FSub))
- return true;
- Value *V1 = Sub->getOperand(1);
- if (isReassociableOp(V1, Instruction::Add, Instruction::FAdd) ||
- isReassociableOp(V1, Instruction::Sub, Instruction::FSub))
- return true;
- Value *VB = Sub->user_back();
- if (Sub->hasOneUse() &&
- (isReassociableOp(VB, Instruction::Add, Instruction::FAdd) ||
- isReassociableOp(VB, Instruction::Sub, Instruction::FSub)))
- return true;
-
- return false;
-}
-
-/// If we have (X-Y), and if either X is an add, or if this is only used by an
-/// add, transform this into (X+(0-Y)) to promote better reassociation.
-static BinaryOperator *BreakUpSubtract(Instruction *Sub,
- ReassociatePass::OrderedSet &ToRedo) {
- // Convert a subtract into an add and a neg instruction. This allows sub
- // instructions to be commuted with other add instructions.
- //
- // Calculate the negative value of Operand 1 of the sub instruction,
- // and set it as the RHS of the add instruction we just made.
- Value *NegVal = NegateValue(Sub->getOperand(1), Sub, ToRedo);
- BinaryOperator *New =
- CreateAdd(Sub->getOperand(0), NegVal, "", Sub->getIterator(), Sub);
- Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op.
- Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op.
- New->takeName(Sub);
-
- // Everyone now refers to the add instruction.
- Sub->replaceAllUsesWith(New);
- New->setDebugLoc(Sub->getDebugLoc());
-
- LLVM_DEBUG(dbgs() << "Negated: " << *New << '\n');
- return New;
-}
-
-/// If this is a shift of a reassociable multiply or is used by one, change
-/// this into a multiply by a constant to assist with further reassociation.
-static BinaryOperator *ConvertShiftToMul(Instruction *Shl) {
- Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
- auto *SA = cast<ConstantInt>(Shl->getOperand(1));
- MulCst = ConstantFoldBinaryInstruction(Instruction::Shl, MulCst, SA);
- assert(MulCst && "Constant folding of immediate constants failed");
-
- BinaryOperator *Mul = BinaryOperator::CreateMul(Shl->getOperand(0), MulCst,
- "", Shl->getIterator());
- Shl->setOperand(0, PoisonValue::get(Shl->getType())); // Drop use of op.
- Mul->takeName(Shl);
-
- // Everyone now refers to the mul instruction.
- Shl->replaceAllUsesWith(Mul);
- Mul->setDebugLoc(Shl->getDebugLoc());
-
- // We can safely preserve the nuw flag in all cases. It's also safe to turn a
- // nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special
- // handling. It can be preserved as long as we're not left shifting by
- // bitwidth - 1.
- bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap();
- bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap();
- unsigned BitWidth = Shl->getType()->getScalarSizeInBits();
- if (NSW && (NUW || SA->getValue().ult(BitWidth - 1)))
- Mul->setHasNoSignedWrap(true);
- Mul->setHasNoUnsignedWrap(NUW);
- return Mul;
-}
-
-/// Scan backwards and forwards among values with the same rank as element i
-/// to see if X exists. If X does not exist, return i. This is useful when
-/// scanning for 'x' when we see '-x' because they both get the same rank.
-static unsigned FindInOperandList(const SmallVectorImpl<ValueEntry> &Ops,
- unsigned i, Value *X) {
- unsigned XRank = Ops[i].Rank;
- unsigned e = Ops.size();
- for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
- if (Ops[j].Op == X)
- return j;
- if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
- if (Instruction *I2 = dyn_cast<Instruction>(X))
- if (I1->isIdenticalTo(I2))
- return j;
- }
- // Scan backwards.
- for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
- if (Ops[j].Op == X)
- return j;
- if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
- if (Instruction *I2 = dyn_cast<Instruction>(X))
- if (I1->isIdenticalTo(I2))
- return j;
- }
- return i;
-}
-
-/// Emit a tree of add instructions, summing Ops together
-/// and returning the result. Insert the tree before I.
-static Value *EmitAddTreeOfValues(Instruction *I,
- SmallVectorImpl<WeakTrackingVH> &Ops) {
- if (Ops.size() == 1) return Ops.back();
-
- Value *V1 = Ops.pop_back_val();
- Value *V2 = EmitAddTreeOfValues(I, Ops);
- auto *NewAdd = CreateAdd(V2, V1, "reass.add", I->getIterator(), I);
- NewAdd->setDebugLoc(I->getDebugLoc());
- return NewAdd;
-}
-
-/// If V is an expression tree that is a multiplication sequence,
-/// and if this sequence contains a multiply by Factor,
-/// remove Factor from the tree and return the new tree.
-/// If new instructions are inserted to generate this tree, DL should be used
-/// as the DebugLoc for these instructions.
-Value *ReassociatePass::RemoveFactorFromExpression(Value *V, Value *Factor,
- DebugLoc DL) {
- BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
- if (!BO)
- return nullptr;
-
- SmallVector<RepeatedValue, 8> Tree;
- OverflowTracking Flags;
- MadeChange |= LinearizeExprTree(BO, Tree, RedoInsts, Flags);
- SmallVector<ValueEntry, 8> Factors;
- Factors.reserve(Tree.size());
- for (const RepeatedValue &E : Tree)
- Factors.append(E.second, ValueEntry(getRank(E.first), E.first));
-
- bool FoundFactor = false;
- bool NeedsNegate = false;
- for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
- if (Factors[i].Op == Factor) {
- FoundFactor = true;
- Factors.erase(Factors.begin()+i);
- break;
- }
-
- // If this is a negative version of this factor, remove it.
- if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor)) {
- if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
- if (FC1->getValue() == -FC2->getValue()) {
- FoundFactor = NeedsNegate = true;
- Factors.erase(Factors.begin()+i);
- break;
- }
- } else if (ConstantFP *FC1 = dyn_cast<ConstantFP>(Factor)) {
- if (ConstantFP *FC2 = dyn_cast<ConstantFP>(Factors[i].Op)) {
- const APFloat &F1 = FC1->getValueAPF();
- APFloat F2(FC2->getValueAPF());
- F2.changeSign();
- if (F1 == F2) {
- FoundFactor = NeedsNegate = true;
- Factors.erase(Factors.begin() + i);
- break;
- }
- }
- }
- }
-
- if (!FoundFactor) {
- // Make sure to restore the operands to the expression tree.
- RewriteExprTree(BO, Factors, Flags);
- return nullptr;
- }
-
- BasicBlock::iterator InsertPt = ++BO->getIterator();
-
- // If this was just a single multiply, remove the multiply and return the only
- // remaining operand.
- if (Factors.size() == 1) {
- RedoInsts.insert(BO);
- V = Factors[0].Op;
- } else {
- RewriteExprTree(BO, Factors, Flags);
- V = BO;
- }
-
- if (NeedsNegate) {
- V = CreateNeg(V, "neg", InsertPt, BO);
- cast<Instruction>(V)->setDebugLoc(DL);
- }
-
- return V;
-}
-
-/// If V is a single-use multiply, recursively add its operands as factors,
-/// otherwise add V to the list of factors.
-///
-/// Ops is the top-level list of add operands we're trying to factor.
-static void FindSingleUseMultiplyFactors(Value *V,
- SmallVectorImpl<Value*> &Factors) {
- BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
- if (!BO) {
- Factors.push_back(V);
- return;
- }
-
- // Otherwise, add the LHS and RHS to the list of factors.
- FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
- FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
-}
-
-/// Optimize a series of operands to an 'and', 'or', or 'xor' instruction.
-/// This optimizes based on identities. If it can be reduced to a single Value,
-/// it is returned, otherwise the Ops list is mutated as necessary.
-static Value *OptimizeAndOrXor(unsigned Opcode,
- SmallVectorImpl<ValueEntry> &Ops) {
- // Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
- // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
- for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
- // First, check for X and ~X in the operand list.
- assert(i < Ops.size());
- Value *X;
- if (match(Ops[i].Op, m_Not(m_Value(X)))) { // Cannot occur for ^.
- unsigned FoundX = FindInOperandList(Ops, i, X);
- if (FoundX != i) {
- if (Opcode == Instruction::And) // ...&X&~X = 0
- return Constant::getNullValue(X->getType());
-
- if (Opcode == Instruction::Or) // ...|X|~X = -1
- return Constant::getAllOnesValue(X->getType());
- }
- }
-
- // Next, check for duplicate pairs of values, which we assume are next to
- // each other, due to our sorting criteria.
- assert(i < Ops.size());
- if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
- if (Opcode == Instruction::And || Opcode == Instruction::Or) {
- // Drop duplicate values for And and Or.
- Ops.erase(Ops.begin()+i);
- --i; --e;
- ++NumAnnihil;
- continue;
- }
-
- // Drop pairs of values for Xor.
- assert(Opcode == Instruction::Xor);
- if (e == 2)
- return Constant::getNullValue(Ops[0].Op->getType());
-
- // Y ^ X^X -> Y
- Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
- i -= 1; e -= 2;
- ++NumAnnihil;
- }
- }
- return nullptr;
-}
-
-/// Helper function of CombineXorOpnd(). It creates a bitwise-and
-/// instruction with the given two operands, and return the resulting
-/// instruction. There are two special cases: 1) if the constant operand is 0,
-/// it will return NULL. 2) if the constant is ~0, the symbolic operand will
-/// be returned.
-static Value *createAndInstr(BasicBlock::iterator InsertBefore, Value *Opnd,
- const APInt &ConstOpnd) {
- if (ConstOpnd.isZero())
- return nullptr;
-
- if (ConstOpnd.isAllOnes())
- return Opnd;
-
- Instruction *I = BinaryOperator::CreateAnd(
- Opnd, ConstantInt::get(Opnd->getType(), ConstOpnd), "and.ra",
- InsertBefore);
- I->setDebugLoc(InsertBefore->getDebugLoc());
- return I;
-}
-
-// Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
-// into "R ^ C", where C would be 0, and R is a symbolic value.
-//
-// If it was successful, true is returned, and the "R" and "C" is returned
-// via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
-// and both "Res" and "ConstOpnd" remain unchanged.
-bool ReassociatePass::CombineXorOpnd(BasicBlock::iterator It, XorOpnd *Opnd1,
- APInt &ConstOpnd, Value *&Res) {
- // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
- // = ((x | c1) ^ c1) ^ (c1 ^ c2)
- // = (x & ~c1) ^ (c1 ^ c2)
- // It is useful only when c1 == c2.
- if (!Opnd1->isOrExpr() || Opnd1->getConstPart().isZero())
- return false;
-
- if (!Opnd1->getValue()->hasOneUse())
- return false;
-
- const APInt &C1 = Opnd1->getConstPart();
- if (C1 != ConstOpnd)
- return false;
-
- Value *X = Opnd1->getSymbolicPart();
- Res = createAndInstr(It, X, ~C1);
- // ConstOpnd was C2, now C1 ^ C2.
- ConstOpnd ^= C1;
-
- if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
- RedoInsts.insert(T);
- return true;
-}
-
-// Helper function of OptimizeXor(). It tries to simplify
-// "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
-// symbolic value.
-//
-// If it was successful, true is returned, and the "R" and "C" is returned
-// via "Res" and "ConstOpnd", respectively (If the entire expression is
-// evaluated to a constant, the Res is set to NULL); otherwise, false is
-// returned, and both "Res" and "ConstOpnd" remain unchanged.
-bool ReassociatePass::CombineXorOpnd(BasicBlock::iterator It, XorOpnd *Opnd1,
- XorOpnd *Opnd2, APInt &ConstOpnd,
- Value *&Res) {
- Value *X = Opnd1->getSymbolicPart();
- if (X != Opnd2->getSymbolicPart())
- return false;
-
- // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
- int DeadInstNum = 1;
- if (Opnd1->getValue()->hasOneUse())
- DeadInstNum++;
- if (Opnd2->getValue()->hasOneUse())
- DeadInstNum++;
-
- // Xor-Rule 2:
- // (x | c1) ^ (x & c2)
- // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
- // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
- // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
- //
- if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
- if (Opnd2->isOrExpr())
- std::swap(Opnd1, Opnd2);
-
- const APInt &C1 = Opnd1->getConstPart();
- const APInt &C2 = Opnd2->getConstPart();
- APInt C3((~C1) ^ C2);
-
- // Do not increase code size!
- if (!C3.isZero() && !C3.isAllOnes()) {
- int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
- if (NewInstNum > DeadInstNum)
- return false;
- }
-
- Res = createAndInstr(It, X, C3);
- ConstOpnd ^= C1;
- } else if (Opnd1->isOrExpr()) {
- // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
- //
- const APInt &C1 = Opnd1->getConstPart();
- const APInt &C2 = Opnd2->getConstPart();
- APInt C3 = C1 ^ C2;
-
- // Do not increase code size
- if (!C3.isZero() && !C3.isAllOnes()) {
- int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
- if (NewInstNum > DeadInstNum)
- return false;
- }
-
- Res = createAndInstr(It, X, C3);
- ConstOpnd ^= C3;
- } else {
- // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
- //
- const APInt &C1 = Opnd1->getConstPart();
- const APInt &C2 = Opnd2->getConstPart();
- APInt C3 = C1 ^ C2;
- Res = createAndInstr(It, X, C3);
- }
-
- // Put the original operands in the Redo list; hope they will be deleted
- // as dead code.
- if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
- RedoInsts.insert(T);
- if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
- RedoInsts.insert(T);
-
- return true;
-}
-
-/// Optimize a series of operands to an 'xor' instruction. If it can be reduced
-/// to a single Value, it is returned, otherwise the Ops list is mutated as
-/// necessary.
-Value *ReassociatePass::OptimizeXor(Instruction *I,
- SmallVectorImpl<ValueEntry> &Ops) {
- if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
- return V;
-
- if (Ops.size() == 1)
- return nullptr;
-
- SmallVector<XorOpnd, 8> Opnds;
- SmallVector<XorOpnd*, 8> OpndPtrs;
- Type *Ty = Ops[0].Op->getType();
- APInt ConstOpnd(Ty->getScalarSizeInBits(), 0);
-
- // Step 1: Convert ValueEntry to XorOpnd
- for (const ValueEntry &Op : Ops) {
- Value *V = Op.Op;
- const APInt *C;
- // TODO: Support non-splat vectors.
- if (match(V, m_APInt(C))) {
- ConstOpnd ^= *C;
- } else {
- XorOpnd O(V);
- O.setSymbolicRank(getRank(O.getSymbolicPart()));
- Opnds.push_back(O);
- }
- }
-
- // NOTE: From this point on, do *NOT* add/delete element to/from "Opnds".
- // It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate
- // the "OpndPtrs" as well. For the similar reason, do not fuse this loop
- // with the previous loop --- the iterator of the "Opnds" may be invalidated
- // when new elements are added to the vector.
- for (XorOpnd &Op : Opnds)
- OpndPtrs.push_back(&Op);
-
- // Step 2: Sort the Xor-Operands in a way such that the operands containing
- // the same symbolic value cluster together. For instance, the input operand
- // sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
- // ("x | 123", "x & 789", "y & 456").
- //
- // The purpose is twofold:
- // 1) Cluster together the operands sharing the same symbolic-value.
- // 2) Operand having smaller symbolic-value-rank is permuted earlier, which
- // could potentially shorten crital path, and expose more loop-invariants.
- // Note that values' rank are basically defined in RPO order (FIXME).
- // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
- // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
- // "z" in the order of X-Y-Z is better than any other orders.
- llvm::stable_sort(OpndPtrs, [](XorOpnd *LHS, XorOpnd *RHS) {
- return LHS->getSymbolicRank() < RHS->getSymbolicRank();
- });
-
- // Step 3: Combine adjacent operands
- XorOpnd *PrevOpnd = nullptr;
- bool Changed = false;
- for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
- XorOpnd *CurrOpnd = OpndPtrs[i];
- // The combined value
- Value *CV;
-
- // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
- if (!ConstOpnd.isZero() &&
- CombineXorOpnd(I->getIterator(), CurrOpnd, ConstOpnd, CV)) {
- Changed = true;
- if (CV)
- *CurrOpnd = XorOpnd(CV);
- else {
- CurrOpnd->Invalidate();
- continue;
- }
- }
-
- if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
- PrevOpnd = CurrOpnd;
- continue;
- }
-
- // step 3.2: When previous and current operands share the same symbolic
- // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
- if (CombineXorOpnd(I->getIterator(), CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
- // Remove previous operand
- PrevOpnd->Invalidate();
- if (CV) {
- *CurrOpnd = XorOpnd(CV);
- PrevOpnd = CurrOpnd;
- } else {
- CurrOpnd->Invalidate();
- PrevOpnd = nullptr;
- }
- Changed = true;
- }
- }
-
- // Step 4: Reassemble the Ops
- if (Changed) {
- Ops.clear();
- for (const XorOpnd &O : Opnds) {
- if (O.isInvalid())
- continue;
- ValueEntry VE(getRank(O.getValue()), O.getValue());
- Ops.push_back(VE);
- }
- if (!ConstOpnd.isZero()) {
- Value *C = ConstantInt::get(Ty, ConstOpnd);
- ValueEntry VE(getRank(C), C);
- Ops.push_back(VE);
- }
- unsigned Sz = Ops.size();
- if (Sz == 1)
- return Ops.back().Op;
- if (Sz == 0) {
- assert(ConstOpnd.isZero());
- return ConstantInt::get(Ty, ConstOpnd);
- }
- }
-
- return nullptr;
-}
-
-/// Optimize a series of operands to an 'add' instruction. This
-/// optimizes based on identities. If it can be reduced to a single Value, it
-/// is returned, otherwise the Ops list is mutated as necessary.
-Value *ReassociatePass::OptimizeAdd(Instruction *I,
- SmallVectorImpl<ValueEntry> &Ops) {
- // Scan the operand lists looking for X and -X pairs. If we find any, we
- // can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it,
- // scan for any
- // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
-
- for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
- Value *TheOp = Ops[i].Op;
- // Check to see if we've seen this operand before. If so, we factor all
- // instances of the operand together. Due to our sorting criteria, we know
- // that these need to be next to each other in the vector.
- if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
- // Rescan the list, remove all instances of this operand from the expr.
- unsigned NumFound = 0;
- do {
- Ops.erase(Ops.begin()+i);
- ++NumFound;
- } while (i != Ops.size() && Ops[i].Op == TheOp);
-
- LLVM_DEBUG(dbgs() << "\nFACTORING [" << NumFound << "]: " << *TheOp
- << '\n');
- ++NumFactor;
-
- // Insert a new multiply.
- Type *Ty = TheOp->getType();
- // Truncate if NumFound overflows the type.
- Constant *C = Ty->isIntOrIntVectorTy()
- ? ConstantInt::get(Ty, NumFound, /*IsSigned=*/false,
- /*ImplicitTrunc=*/true)
- : ConstantFP::get(Ty, NumFound);
- Instruction *Mul = CreateMul(TheOp, C, "factor", I->getIterator(), I);
- Mul->setDebugLoc(I->getDebugLoc());
-
- // Now that we have inserted a multiply, optimize it. This allows us to
- // handle cases that require multiple factoring steps, such as this:
- // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
- RedoInsts.insert(Mul);
-
- // If every add operand was a duplicate, return the multiply.
- if (Ops.empty())
- return Mul;
-
- // Otherwise, we had some input that didn't have the dupe, such as
- // "A + A + B" -> "A*2 + B". Add the new multiply to the list of
- // things being added by this operation.
- Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
-
- --i;
- e = Ops.size();
- continue;
- }
-
- // Check for X and -X or X and ~X in the operand list.
- Value *X;
- if (!match(TheOp, m_Neg(m_Value(X))) && !match(TheOp, m_Not(m_Value(X))) &&
- !match(TheOp, m_FNeg(m_Value(X))))
- continue;
-
- unsigned FoundX = FindInOperandList(Ops, i, X);
- if (FoundX == i)
- continue;
-
- // Remove X and -X from the operand list.
- if (Ops.size() == 2 &&
- (match(TheOp, m_Neg(m_Value())) || match(TheOp, m_FNeg(m_Value()))))
- return Constant::getNullValue(X->getType());
-
- // Remove X and ~X from the operand list.
- if (Ops.size() == 2 && match(TheOp, m_Not(m_Value())))
- return Constant::getAllOnesValue(X->getType());
-
- Ops.erase(Ops.begin()+i);
- if (i < FoundX)
- --FoundX;
- else
- --i; // Need to back up an extra one.
- Ops.erase(Ops.begin()+FoundX);
- ++NumAnnihil;
- --i; // Revisit element.
- e -= 2; // Removed two elements.
-
- // if X and ~X we append -1 to the operand list.
- if (match(TheOp, m_Not(m_Value()))) {
- Value *V = Constant::getAllOnesValue(X->getType());
- Ops.insert(Ops.end(), ValueEntry(getRank(V), V));
- e += 1;
- }
- }
-
- // Scan the operand list, checking to see if there are any common factors
- // between operands. Consider something like A*A+A*B*C+D. We would like to
- // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
- // To efficiently find this, we count the number of times a factor occurs
- // for any ADD operands that are MULs.
- DenseMap<Value*, unsigned> FactorOccurrences;
-
- // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
- // where they are actually the same multiply.
- unsigned MaxOcc = 0;
- Value *MaxOccVal = nullptr;
-
- // Prefer a non-constant factor over a constant when occurrence counts
- // tie. Factoring out a variable (e.g., X from X*C1 + X*C2) exposes
- // downstream constant folding; factoring out a constant does not.
- auto IsBetterFactor = [](Value *Factor, Value *MaxOccVal, unsigned Occ,
- unsigned MaxOcc) {
- return Occ > MaxOcc ||
- (Occ == MaxOcc &&
- (isa<Instruction>(Factor) || isa<Argument>(Factor)) &&
- isa<Constant>(MaxOccVal) && !isa<UndefValue>(MaxOccVal));
- };
- for (const ValueEntry &Op : Ops) {
- BinaryOperator *BOp =
- isReassociableOp(Op.Op, Instruction::Mul, Instruction::FMul);
- if (!BOp)
- continue;
-
- // Compute all of the factors of this added value.
- SmallVector<Value*, 8> Factors;
- FindSingleUseMultiplyFactors(BOp, Factors);
- assert(Factors.size() > 1 && "Bad linearize!");
-
- // Add one to FactorOccurrences for each unique factor in this op.
- SmallPtrSet<Value*, 8> Duplicates;
- for (Value *Factor : Factors) {
- if (!Duplicates.insert(Factor).second)
- continue;
-
- unsigned Occ = ++FactorOccurrences[Factor];
- if (IsBetterFactor(Factor, MaxOccVal, Occ, MaxOcc)) {
- MaxOcc = Occ;
- MaxOccVal = Factor;
- }
-
- // If Factor is a negative constant, add the negated value as a factor
- // because we can percolate the negate out. Watch for minint, which
- // cannot be positivified.
- if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor)) {
- if (CI->isNegative() && !CI->isMinValue(true)) {
- Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
- if (!Duplicates.insert(Factor).second)
- continue;
- unsigned Occ = ++FactorOccurrences[Factor];
- if (IsBetterFactor(Factor, MaxOccVal, Occ, MaxOcc)) {
- MaxOcc = Occ;
- MaxOccVal = Factor;
- }
- }
- } else if (ConstantFP *CF = dyn_cast<ConstantFP>(Factor)) {
- if (CF->isNegative()) {
- APFloat F(CF->getValueAPF());
- F.changeSign();
- Factor = ConstantFP::get(CF->getType(), F);
- if (!Duplicates.insert(Factor).second)
- continue;
- unsigned Occ = ++FactorOccurrences[Factor];
- if (IsBetterFactor(Factor, MaxOccVal, Occ, MaxOcc)) {
- MaxOcc = Occ;
- MaxOccVal = Factor;
- }
- }
- }
- }
- }
-
- // If any factor occurred more than one time, we can pull it out.
- if (MaxOcc > 1) {
- LLVM_DEBUG(dbgs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal
- << '\n');
- ++NumFactor;
-
- // Create a new instruction that uses the MaxOccVal twice. If we don't do
- // this, we could otherwise run into situations where removing a factor
- // from an expression will drop a use of maxocc, and this can cause
- // RemoveFactorFromExpression on successive values to behave differently.
- Instruction *DummyInst =
- I->getType()->isIntOrIntVectorTy()
- ? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal)
- : BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal);
-
- SmallVector<WeakTrackingVH, 4> NewMulOps;
- for (unsigned i = 0; i != Ops.size(); ++i) {
- // Only try to remove factors from expressions we're allowed to.
- BinaryOperator *BOp =
- isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
- if (!BOp)
- continue;
-
- if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal,
- I->getDebugLoc())) {
- // The factorized operand may occur several times. Convert them all in
- // one fell swoop.
- for (unsigned j = Ops.size(); j != i;) {
- --j;
- if (Ops[j].Op == Ops[i].Op) {
- NewMulOps.push_back(V);
- Ops.erase(Ops.begin()+j);
- }
- }
- --i;
- }
- }
-
- // No need for extra uses anymore.
- DummyInst->deleteValue();
-
- unsigned NumAddedValues = NewMulOps.size();
- Value *V = EmitAddTreeOfValues(I, NewMulOps);
-
- // Now that we have inserted the add tree, optimize it. This allows us to
- // handle cases that require multiple factoring steps, such as this:
- // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
- assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
- (void)NumAddedValues;
- if (Instruction *VI = dyn_cast<Instruction>(V))
- RedoInsts.insert(VI);
-
- // Create the multiply.
- Instruction *V2 = CreateMul(V, MaxOccVal, "reass.mul", I->getIterator(), I);
- V2->setDebugLoc(I->getDebugLoc());
-
- // Rerun associate on the multiply in case the inner expression turned into
- // a multiply. We want to make sure that we keep things in canonical form.
- RedoInsts.insert(V2);
-
- // If every add operand included the factor (e.g. "A*B + A*C"), then the
- // entire result expression is just the multiply "A*(B+C)".
- if (Ops.empty())
- return V2;
-
- // Otherwise, we had some input that didn't have the factor, such as
- // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
- // things being added by this operation.
- Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
- }
-
- return nullptr;
-}
-
-/// Build up a vector of value/power pairs factoring a product.
-///
-/// Given a series of multiplication operands, build a vector of factors and
-/// the powers each is raised to when forming the final product. Sort them in
-/// the order of descending power.
-///
-/// (x*x) -> [(x, 2)]
-/// ((x*x)*x) -> [(x, 3)]
-/// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
-///
-/// \returns Whether any factors have a power greater than one.
-static bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
- SmallVectorImpl<Factor> &Factors) {
- // FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this.
- // Compute the sum of powers of simplifiable factors.
- unsigned FactorPowerSum = 0;
- for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) {
- Value *Op = Ops[Idx-1].Op;
-
- // Count the number of occurrences of this value.
- unsigned Count = 1;
- for (; Idx < Size && Ops[Idx].Op == Op; ++Idx)
- ++Count;
- // Track for simplification all factors which occur 2 or more times.
- if (Count > 1)
- FactorPowerSum += Count;
- }
-
- // We can only simplify factors if the sum of the powers of our simplifiable
- // factors is 4 or higher. When that is the case, we will *always* have
- // a simplification. This is an important invariant to prevent cyclicly
- // trying to simplify already minimal formations.
- if (FactorPowerSum < 4)
- return false;
-
- // Now gather the simplifiable factors, removing them from Ops.
- FactorPowerSum = 0;
- for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) {
- Value *Op = Ops[Idx-1].Op;
-
- // Count the number of occurrences of this value.
- unsigned Count = 1;
- for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx)
- ++Count;
- if (Count == 1)
- continue;
- // Move an even number of occurrences to Factors.
- Count &= ~1U;
- Idx -= Count;
- FactorPowerSum += Count;
- Factors.push_back(Factor(Op, Count));
- Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count);
- }
-
- // None of the adjustments above should have reduced the sum of factor powers
- // below our mininum of '4'.
- assert(FactorPowerSum >= 4);
-
- llvm::stable_sort(Factors, [](const Factor &LHS, const Factor &RHS) {
- return LHS.Power > RHS.Power;
- });
- return true;
-}
-
-/// Build a tree of multiplies, computing the product of Ops.
-static Value *buildMultiplyTree(IRBuilderBase &Builder,
- SmallVectorImpl<Value*> &Ops) {
- if (Ops.size() == 1)
- return Ops.back();
-
- Value *LHS = Ops.pop_back_val();
- do {
- if (LHS->getType()->isIntOrIntVectorTy())
- LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
- else
- LHS = Builder.CreateFMul(LHS, Ops.pop_back_val());
- } while (!Ops.empty());
-
- return LHS;
-}
-
-/// Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
-///
-/// Given a vector of values raised to various powers, where no two values are
-/// equal and the powers are sorted in decreasing order, compute the minimal
-/// DAG of multiplies to compute the final product, and return that product
-/// value.
-Value *
-ReassociatePass::buildMinimalMultiplyDAG(IRBuilderBase &Builder,
- SmallVectorImpl<Factor> &Factors) {
- assert(Factors[0].Power);
- SmallVector<Value *, 4> OuterProduct;
- for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
- Idx < Size && Factors[Idx].Power > 0; ++Idx) {
- if (Factors[Idx].Power != Factors[LastIdx].Power) {
- LastIdx = Idx;
- continue;
- }
-
- // We want to multiply across all the factors with the same power so that
- // we can raise them to that power as a single entity. Build a mini tree
- // for that.
- SmallVector<Value *, 4> InnerProduct;
- InnerProduct.push_back(Factors[LastIdx].Base);
- do {
- InnerProduct.push_back(Factors[Idx].Base);
- ++Idx;
- } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
-
- // Reset the base value of the first factor to the new expression tree.
- // We'll remove all the factors with the same power in a second pass.
- Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
- if (Instruction *MI = dyn_cast<Instruction>(M))
- RedoInsts.insert(MI);
-
- LastIdx = Idx;
- }
- // Unique factors with equal powers -- we've folded them into the first one's
- // base.
- Factors.erase(llvm::unique(Factors,
- [](const Factor &LHS, const Factor &RHS) {
- return LHS.Power == RHS.Power;
- }),
- Factors.end());
-
- // Iteratively collect the base of each factor with an add power into the
- // outer product, and halve each power in preparation for squaring the
- // expression.
- for (Factor &F : Factors) {
- if (F.Power & 1)
- OuterProduct.push_back(F.Base);
- F.Power >>= 1;
- }
- if (Factors[0].Power) {
- Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
- OuterProduct.push_back(SquareRoot);
- OuterProduct.push_back(SquareRoot);
- }
- if (OuterProduct.size() == 1)
- return OuterProduct.front();
-
- Value *V = buildMultiplyTree(Builder, OuterProduct);
- return V;
-}
-
-Value *ReassociatePass::OptimizeMul(BinaryOperator *I,
- SmallVectorImpl<ValueEntry> &Ops) {
- // We can only optimize the multiplies when there is a chain of more than
- // three, such that a balanced tree might require fewer total multiplies.
- if (Ops.size() < 4)
- return nullptr;
-
- // Try to turn linear trees of multiplies without other uses of the
- // intermediate stages into minimal multiply DAGs with perfect sub-expression
- // re-use.
- SmallVector<Factor, 4> Factors;
- if (!collectMultiplyFactors(Ops, Factors))
- return nullptr; // All distinct factors, so nothing left for us to do.
-
- IRBuilder<> Builder(I);
- // The reassociate transformation for FP operations is performed only
- // if unsafe algebra is permitted by FastMathFlags. Propagate those flags
- // to the newly generated operations.
- if (auto FPI = dyn_cast<FPMathOperator>(I))
- Builder.setFastMathFlags(FPI->getFastMathFlags());
-
- Value *V = buildMinimalMultiplyDAG(Builder, Factors);
- if (Ops.empty())
- return V;
-
- ValueEntry NewEntry = ValueEntry(getRank(V), V);
- Ops.insert(llvm::lower_bound(Ops, NewEntry), NewEntry);
- return nullptr;
-}
-
-Value *ReassociatePass::OptimizeExpression(BinaryOperator *I,
- SmallVectorImpl<ValueEntry> &Ops) {
- // Now that we have the linearized expression tree, try to optimize it.
- // Start by folding any constants that we found.
- const DataLayout &DL = I->getDataLayout();
- Constant *Cst = nullptr;
- unsigned Opcode = I->getOpcode();
- while (!Ops.empty()) {
- if (auto *C = dyn_cast<Constant>(Ops.back().Op)) {
- if (!Cst) {
- Ops.pop_back();
- Cst = C;
- continue;
- }
- if (Constant *Res = ConstantFoldBinaryOpOperands(Opcode, C, Cst, DL)) {
- Ops.pop_back();
- Cst = Res;
- continue;
- }
- }
- break;
- }
- // If there was nothing but constants then we are done.
- if (Ops.empty())
- return Cst;
-
- // Put the combined constant back at the end of the operand list, except if
- // there is no point. For example, an add of 0 gets dropped here, while a
- // multiplication by zero turns the whole expression into zero.
- if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) {
- if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType()))
- return Cst;
- Ops.push_back(ValueEntry(0, Cst));
- }
-
- if (Ops.size() == 1) return Ops[0].Op;
-
- // Handle destructive annihilation due to identities between elements in the
- // argument list here.
- unsigned NumOps = Ops.size();
- switch (Opcode) {
- default: break;
- case Instruction::And:
- case Instruction::Or:
- if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
- return Result;
- break;
-
- case Instruction::Xor:
- if (Value *Result = OptimizeXor(I, Ops))
- return Result;
- break;
-
- case Instruction::Add:
- case Instruction::FAdd:
- if (Value *Result = OptimizeAdd(I, Ops))
- return Result;
- break;
-
- case Instruction::Mul:
- case Instruction::FMul:
- if (Value *Result = OptimizeMul(I, Ops))
- return Result;
- break;
- }
-
- if (Ops.size() != NumOps)
- return OptimizeExpression(I, Ops);
- return nullptr;
-}
-
-// Remove dead instructions and if any operands are trivially dead add them to
-// Insts so they will be removed as well.
-void ReassociatePass::RecursivelyEraseDeadInsts(Instruction *I,
- OrderedSet &Insts) {
- assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
- SmallVector<Value *, 4> Ops(I->operands());
- ValueRankMap.erase(I);
- Insts.remove(I);
- RedoInsts.remove(I);
- llvm::salvageDebugInfo(*I);
- I->eraseFromParent();
- for (auto *Op : Ops)
- if (Instruction *OpInst = dyn_cast<Instruction>(Op))
- if (OpInst->use_empty())
- Insts.insert(OpInst);
-}
-
-/// Zap the given instruction, adding interesting operands to the work list.
-void ReassociatePass::EraseInst(Instruction *I) {
- assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
- LLVM_DEBUG(dbgs() << "Erasing dead inst: "; I->dump());
-
- SmallVector<Value *, 8> Ops(I->operands());
- // Erase the dead instruction.
- ValueRankMap.erase(I);
- RedoInsts.remove(I);
- llvm::salvageDebugInfo(*I);
- I->eraseFromParent();
- // Optimize its operands.
- SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
- for (Value *V : Ops)
- if (Instruction *Op = dyn_cast<Instruction>(V)) {
- // If this is a node in an expression tree, climb to the expression root
- // and add that since that's where optimization actually happens.
- unsigned Opcode = Op->getOpcode();
- while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode &&
- Visited.insert(Op).second)
- Op = Op->user_back();
-
- // The instruction we're going to push may be coming from a
- // dead block, and Reassociate skips the processing of unreachable
- // blocks because it's a waste of time and also because it can
- // lead to infinite loop due to LLVM's non-standard definition
- // of dominance.
- if (ValueRankMap.contains(Op))
- RedoInsts.insert(Op);
- }
-
- MadeChange = true;
-}
-
-/// Recursively analyze an expression to build a list of instructions that have
-/// negative floating-point constant operands. The caller can then transform
-/// the list to create positive constants for better reassociation and CSE.
-static void getNegatibleInsts(Value *V,
- SmallVectorImpl<Instruction *> &Candidates) {
- // Handle only one-use instructions. Combining negations does not justify
- // replicating instructions.
- Instruction *I;
- if (!match(V, m_OneUse(m_Instruction(I))))
- return;
-
- // Handle expressions of multiplications and divisions.
- // TODO: This could look through floating-point casts.
- const APFloat *C;
- switch (I->getOpcode()) {
- case Instruction::FMul:
- // Not expecting non-canonical code here. Bail out and wait.
- if (match(I->getOperand(0), m_Constant()))
- break;
-
- if (match(I->getOperand(1), m_APFloat(C)) && C->isNegative()) {
- Candidates.push_back(I);
- LLVM_DEBUG(dbgs() << "FMul with negative constant: " << *I << '\n');
- }
- getNegatibleInsts(I->getOperand(0), Candidates);
- getNegatibleInsts(I->getOperand(1), Candidates);
- break;
- case Instruction::FDiv:
- // Not expecting non-canonical code here. Bail out and wait.
- if (match(I->getOperand(0), m_Constant()) &&
- match(I->getOperand(1), m_Constant()))
- break;
-
- if ((match(I->getOperand(0), m_APFloat(C)) && C->isNegative()) ||
- (match(I->getOperand(1), m_APFloat(C)) && C->isNegative())) {
- Candidates.push_back(I);
- LLVM_DEBUG(dbgs() << "FDiv with negative constant: " << *I << '\n');
- }
- getNegatibleInsts(I->getOperand(0), Candidates);
- getNegatibleInsts(I->getOperand(1), Candidates);
- break;
- default:
- break;
- }
-}
-
-/// Given an fadd/fsub with an operand that is a one-use instruction
-/// (the fadd/fsub), try to change negative floating-point constants into
-/// positive constants to increase potential for reassociation and CSE.
-Instruction *ReassociatePass::canonicalizeNegFPConstantsForOp(Instruction *I,
- Instruction *Op,
- Value *OtherOp) {
- assert((I->getOpcode() == Instruction::FAdd ||
- I->getOpcode() == Instruction::FSub) && "Expected fadd/fsub");
-
- // Collect instructions with negative FP constants from the subtree that ends
- // in Op.
- SmallVector<Instruction *, 4> Candidates;
- getNegatibleInsts(Op, Candidates);
- if (Candidates.empty())
- return nullptr;
-
- // Don't canonicalize x + (-Constant * y) -> x - (Constant * y), if the
- // resulting subtract will be broken up later. This can get us into an
- // infinite loop during reassociation.
- bool IsFSub = I->getOpcode() == Instruction::FSub;
- bool NeedsSubtract = !IsFSub && Candidates.size() % 2 == 1;
- if (NeedsSubtract && ShouldBreakUpSubtract(I))
- return nullptr;
-
- for (Instruction *Negatible : Candidates) {
- const APFloat *C;
- if (match(Negatible->getOperand(0), m_APFloat(C))) {
- assert(!match(Negatible->getOperand(1), m_Constant()) &&
- "Expecting only 1 constant operand");
- assert(C->isNegative() && "Expected negative FP constant");
- Negatible->setOperand(0, ConstantFP::get(Negatible->getType(), abs(*C)));
- MadeChange = true;
- }
- if (match(Negatible->getOperand(1), m_APFloat(C))) {
- assert(!match(Negatible->getOperand(0), m_Constant()) &&
- "Expecting only 1 constant operand");
- assert(C->isNegative() && "Expected negative FP constant");
- Negatible->setOperand(1, ConstantFP::get(Negatible->getType(), abs(*C)));
- MadeChange = true;
- }
- }
- assert(MadeChange == true && "Negative constant candidate was not changed");
-
- // Negations cancelled out.
- if (Candidates.size() % 2 == 0)
- return I;
-
- // Negate the final operand in the expression by flipping the opcode of this
- // fadd/fsub.
- assert(Candidates.size() % 2 == 1 && "Expected odd number");
- IRBuilder<> Builder(I);
- Value *NewInst = IsFSub ? Builder.CreateFAddFMF(OtherOp, Op, I)
- : Builder.CreateFSubFMF(OtherOp, Op, I);
- I->replaceAllUsesWith(NewInst);
- RedoInsts.insert(I);
- return dyn_cast<Instruction>(NewInst);
-}
-
-/// Canonicalize expressions that contain a negative floating-point constant
-/// of the following form:
-/// OtherOp + (subtree) -> OtherOp {+/-} (canonical subtree)
-/// (subtree) + OtherOp -> OtherOp {+/-} (canonical subtree)
-/// OtherOp - (subtree) -> OtherOp {+/-} (canonical subtree)
-///
-/// The fadd/fsub opcode may be switched to allow folding a negation into the
-/// input instruction.
-Instruction *ReassociatePass::canonicalizeNegFPConstants(Instruction *I) {
- LLVM_DEBUG(dbgs() << "Combine negations for: " << *I << '\n');
- Value *X;
- Instruction *Op;
- if (match(I, m_FAdd(m_Value(X), m_OneUse(m_Instruction(Op)))))
- if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X))
- I = R;
- if (match(I, m_FAdd(m_OneUse(m_Instruction(Op)), m_Value(X))))
- if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X))
- I = R;
- if (match(I, m_FSub(m_Value(X), m_OneUse(m_Instruction(Op)))))
- if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X))
- I = R;
- return I;
-}
-
-/// Inspect and optimize the given instruction. Note that erasing
-/// instructions is not allowed.
-void ReassociatePass::OptimizeInst(Instruction *I) {
- // Only consider operations that we understand.
- if (!isa<UnaryOperator>(I) && !isa<BinaryOperator>(I))
- return;
-
- if (I->getOpcode() == Instruction::Shl && isa<ConstantInt>(I->getOperand(1)))
- // If an operand of this shift is a reassociable multiply, or if the shift
- // is used by a reassociable multiply or add, turn into a multiply.
- if (isReassociableOp(I->getOperand(0), Instruction::Mul) ||
- (I->hasOneUse() &&
- (isReassociableOp(I->user_back(), Instruction::Mul) ||
- isReassociableOp(I->user_back(), Instruction::Add)))) {
- Instruction *NI = ConvertShiftToMul(I);
- RedoInsts.insert(I);
- MadeChange = true;
- I = NI;
- }
-
- // Commute binary operators, to canonicalize the order of their operands.
- // This can potentially expose more CSE opportunities, and makes writing other
- // transformations simpler.
- if (I->isCommutative())
- canonicalizeOperands(I);
-
- // Canonicalize negative constants out of expressions.
- if (Instruction *Res = canonicalizeNegFPConstants(I))
- I = Res;
-
- // Don't optimize floating-point instructions unless they have the
- // appropriate FastMathFlags for reassociation enabled.
- if (isa<FPMathOperator>(I) && !hasFPAssociativeFlags(I))
- return;
-
- // Do not reassociate boolean (i1/vXi1) expressions. We want to preserve the
- // original order of evaluation for short-circuited comparisons that
- // SimplifyCFG has folded to AND/OR expressions. If the expression
- // is not further optimized, it is likely to be transformed back to a
- // short-circuited form for code gen, and the source order may have been
- // optimized for the most likely conditions. For vector boolean expressions,
- // we should be optimizing for ILP and not serializing the logical operations.
- if (I->getType()->isIntOrIntVectorTy(1))
- return;
-
- // If this is a bitwise or instruction of operands
- // with no common bits set, convert it to X+Y.
- if (I->getOpcode() == Instruction::Or &&
- shouldConvertOrWithNoCommonBitsToAdd(I) && !isLoadCombineCandidate(I) &&
- (cast<PossiblyDisjointInst>(I)->isDisjoint() ||
- haveNoCommonBitsSet(I->getOperand(0), I->getOperand(1),
- SimplifyQuery(I->getDataLayout(),
- /*DT=*/nullptr, /*AC=*/nullptr, I)))) {
- Instruction *NI = convertOrWithNoCommonBitsToAdd(I);
- RedoInsts.insert(I);
- MadeChange = true;
- I = NI;
- }
-
- if (I->getOpcode() == Instruction::Mul && ShouldBreakUpDistribution(I)) {
- Instruction *MulUser = cast<Instruction>(I->user_back());
- BreakUpDistribute(I, RedoInsts);
- RedoInsts.insert(I);
- RedoInsts.insert(MulUser);
- MadeChange = true;
- return;
- }
-
- // If this is a subtract instruction which is not already in negate form,
- // see if we can convert it to X+-Y.
- if (I->getOpcode() == Instruction::Sub) {
- if (ShouldBreakUpSubtract(I)) {
- Instruction *NI = BreakUpSubtract(I, RedoInsts);
- RedoInsts.insert(I);
- MadeChange = true;
- I = NI;
- } else if (match(I, m_Neg(m_Value()))) {
- // Otherwise, this is a negation. See if the operand is a multiply tree
- // and if this is not an inner node of a multiply tree.
- if (isReassociableOp(I->getOperand(1), Instruction::Mul) &&
- (!I->hasOneUse() ||
- !isReassociableOp(I->user_back(), Instruction::Mul))) {
- Instruction *NI = LowerNegateToMultiply(I);
- // If the negate was simplified, revisit the users to see if we can
- // reassociate further.
- for (User *U : NI->users()) {
- if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
- RedoInsts.insert(Tmp);
- }
- RedoInsts.insert(I);
- MadeChange = true;
- I = NI;
- }
- }
- } else if (I->getOpcode() == Instruction::FNeg ||
- I->getOpcode() == Instruction::FSub) {
- if (ShouldBreakUpSubtract(I)) {
- Instruction *NI = BreakUpSubtract(I, RedoInsts);
- RedoInsts.insert(I);
- MadeChange = true;
- I = NI;
- } else if (match(I, m_FNeg(m_Value()))) {
- // Otherwise, this is a negation. See if the operand is a multiply tree
- // and if this is not an inner node of a multiply tree.
- Value *Op = isa<BinaryOperator>(I) ? I->getOperand(1) :
- I->getOperand(0);
- if (isReassociableOp(Op, Instruction::FMul) &&
- (!I->hasOneUse() ||
- !isReassociableOp(I->user_back(), Instruction::FMul))) {
- // If the negate was simplified, revisit the users to see if we can
- // reassociate further.
- Instruction *NI = LowerNegateToMultiply(I);
- for (User *U : NI->users()) {
- if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
- RedoInsts.insert(Tmp);
- }
- RedoInsts.insert(I);
- MadeChange = true;
- I = NI;
- }
- }
- }
-
- // If this instruction is an associative binary operator, process it.
- if (!I->isAssociative()) return;
- BinaryOperator *BO = cast<BinaryOperator>(I);
-
- // If this is an interior node of a reassociable tree, ignore it until we
- // get to the root of the tree, to avoid N^2 analysis.
- unsigned Opcode = BO->getOpcode();
- if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode) {
- // During the initial run we will get to the root of the tree.
- // But if we get here while we are redoing instructions, there is no
- // guarantee that the root will be visited. So Redo later
- if (BO->user_back() != BO &&
- BO->getParent() == BO->user_back()->getParent())
- RedoInsts.insert(BO->user_back());
- return;
- }
-
- // If this is an add tree that is used by a sub instruction, ignore it
- // until we process the subtract.
- if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
- cast<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub)
- return;
- if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd &&
- cast<Instruction>(BO->user_back())->getOpcode() == Instruction::FSub)
- return;
-
- ReassociateExpression(BO);
-}
-
-void ReassociatePass::ReassociateExpression(BinaryOperator *I) {
- // First, walk the expression tree, linearizing the tree, collecting the
- // operand information.
- SmallVector<RepeatedValue, 8> Tree;
- OverflowTracking Flags;
- MadeChange |= LinearizeExprTree(I, Tree, RedoInsts, Flags);
- SmallVector<ValueEntry, 8> Ops;
- Ops.reserve(Tree.size());
- for (const RepeatedValue &E : Tree)
- Ops.append(E.second, ValueEntry(getRank(E.first), E.first));
-
- LLVM_DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
-
- // Now that we have linearized the tree to a list and have gathered all of
- // the operands and their ranks, sort the operands by their rank. Use a
- // stable_sort so that values with equal ranks will have their relative
- // positions maintained (and so the compiler is deterministic). Note that
- // this sorts so that the highest ranking values end up at the beginning of
- // the vector.
- llvm::stable_sort(Ops);
-
- // Now that we have the expression tree in a convenient
- // sorted form, optimize it globally if possible.
- if (Value *V = OptimizeExpression(I, Ops)) {
- if (V == I)
- // Self-referential expression in unreachable code.
- return;
- // This expression tree simplified to something that isn't a tree,
- // eliminate it.
- LLVM_DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
- I->replaceAllUsesWith(V);
- if (Instruction *VI = dyn_cast<Instruction>(V))
- if (I->getDebugLoc())
- VI->setDebugLoc(I->getDebugLoc());
- RedoInsts.insert(I);
- ++NumAnnihil;
- return;
- }
-
- // We want to sink immediates as deeply as possible except in the case where
- // this is a multiply tree used only by an add, and the immediate is a -1.
- // In this case we reassociate to put the negation on the outside so that we
- // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
- if (I->hasOneUse()) {
- if (I->getOpcode() == Instruction::Mul &&
- cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
- isa<ConstantInt>(Ops.back().Op) &&
- cast<ConstantInt>(Ops.back().Op)->isMinusOne()) {
- ValueEntry Tmp = Ops.pop_back_val();
- Ops.insert(Ops.begin(), Tmp);
- } else if (I->getOpcode() == Instruction::FMul &&
- cast<Instruction>(I->user_back())->getOpcode() ==
- Instruction::FAdd &&
- isa<ConstantFP>(Ops.back().Op) &&
- cast<ConstantFP>(Ops.back().Op)->isExactlyValue(-1.0)) {
- ValueEntry Tmp = Ops.pop_back_val();
- Ops.insert(Ops.begin(), Tmp);
- }
- }
-
- LLVM_DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
-
- if (Ops.size() == 1) {
- if (Ops[0].Op == I)
- // Self-referential expression in unreachable code.
- return;
-
- // This expression tree simplified to something that isn't a tree,
- // eliminate it.
- I->replaceAllUsesWith(Ops[0].Op);
- if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
- OI->setDebugLoc(I->getDebugLoc());
- RedoInsts.insert(I);
- return;
- }
-
- if (Ops.size() > 2 && Ops.size() <= GlobalReassociateLimit) {
- // Find the pair with the highest count in the pairmap and move it to the
- // back of the list so that it can later be CSE'd.
- // example:
- // a*b*c*d*e
- // if c*e is the most "popular" pair, we can express this as
- // (((c*e)*d)*b)*a
- unsigned Max = 1;
- unsigned BestRank = 0;
- std::pair<unsigned, unsigned> BestPair;
- unsigned Idx = I->getOpcode() - Instruction::BinaryOpsBegin;
- unsigned LimitIdx = 0;
- // With the CSE-driven heuristic, we are about to slap two values at the
- // beginning of the expression whereas they could live very late in the CFG.
- // When using the CSE-local heuristic we avoid creating dependences from
- // completely unrelated part of the CFG by limiting the expression
- // reordering on the values that live in the first seen basic block.
- // The main idea is that we want to avoid forming expressions that would
- // become loop dependent.
- if (UseCSELocalOpt) {
- const BasicBlock *FirstSeenBB = nullptr;
- int StartIdx = Ops.size() - 1;
- // Skip the first value of the expression since we need at least two
- // values to materialize an expression. I.e., even if this value is
- // anchored in a different basic block, the actual first sub expression
- // will be anchored on the second value.
- for (int i = StartIdx - 1; i != -1; --i) {
- const Value *Val = Ops[i].Op;
- const auto *CurrLeafInstr = dyn_cast<Instruction>(Val);
- const BasicBlock *SeenBB = nullptr;
- if (!CurrLeafInstr) {
- // The value is free of any CFG dependencies.
- // Do as if it lives in the entry block.
- //
- // We do this to make sure all the values falling on this path are
- // seen through the same anchor point. The rationale is these values
- // can be combined together to from a sub expression free of any CFG
- // dependencies so we want them to stay together.
- // We could be cleverer and postpone the anchor down to the first
- // anchored value, but that's likely complicated to get right.
- // E.g., we wouldn't want to do that if that means being stuck in a
- // loop.
- //
- // For instance, we wouldn't want to change:
- // res = arg1 op arg2 op arg3 op ... op loop_val1 op loop_val2 ...
- // into
- // res = loop_val1 op arg1 op arg2 op arg3 op ... op loop_val2 ...
- // Because all the sub expressions with arg2..N would be stuck between
- // two loop dependent values.
- SeenBB = &I->getParent()->getParent()->getEntryBlock();
- } else {
- SeenBB = CurrLeafInstr->getParent();
- }
-
- if (!FirstSeenBB) {
- FirstSeenBB = SeenBB;
- continue;
- }
- if (FirstSeenBB != SeenBB) {
- // ith value is in a different basic block.
- // Rewind the index once to point to the last value on the same basic
- // block.
- LimitIdx = i + 1;
- LLVM_DEBUG(dbgs() << "CSE reordering: Consider values between ["
- << LimitIdx << ", " << StartIdx << "]\n");
- break;
- }
- }
- }
- for (unsigned i = Ops.size() - 1; i > LimitIdx; --i) {
- // We must use int type to go below zero when LimitIdx is 0.
- for (int j = i - 1; j >= (int)LimitIdx; --j) {
- unsigned Score = 0;
- Value *Op0 = Ops[i].Op;
- Value *Op1 = Ops[j].Op;
- if (std::less<Value *>()(Op1, Op0))
- std::swap(Op0, Op1);
- auto it = PairMap[Idx].find({Op0, Op1});
- if (it != PairMap[Idx].end()) {
- // Functions like BreakUpSubtract() can erase the Values we're using
- // as keys and create new Values after we built the PairMap. There's a
- // small chance that the new nodes can have the same address as
- // something already in the table. We shouldn't accumulate the stored
- // score in that case as it refers to the wrong Value.
- if (it->second.isValid())
- Score += it->second.Score;
- }
-
- unsigned MaxRank = std::max(Ops[i].Rank, Ops[j].Rank);
-
- // By construction, the operands are sorted in reverse order of their
- // topological order.
- // So we tend to form (sub) expressions with values that are close to
- // each other.
- //
- // Now to expose more CSE opportunities we want to expose the pair of
- // operands that occur the most (as statically computed in
- // BuildPairMap.) as the first sub-expression.
- //
- // If two pairs occur as many times, we pick the one with the
- // lowest rank, meaning the one with both operands appearing first in
- // the topological order.
- if (Score > Max || (Score == Max && MaxRank < BestRank)) {
- BestPair = {j, i};
- Max = Score;
- BestRank = MaxRank;
- }
- }
- }
- if (Max > 1) {
- auto Op0 = Ops[BestPair.first];
- auto Op1 = Ops[BestPair.second];
- Ops.erase(&Ops[BestPair.second]);
- Ops.erase(&Ops[BestPair.first]);
- Ops.push_back(Op0);
- Ops.push_back(Op1);
- }
- }
- LLVM_DEBUG(dbgs() << "RAOut after CSE reorder:\t"; PrintOps(I, Ops);
- dbgs() << '\n');
- // Now that we ordered and optimized the expressions, splat them back into
- // the expression tree, removing any unneeded nodes.
- RewriteExprTree(I, Ops, Flags);
-}
-
-void
-ReassociatePass::BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT) {
- // Make a "pairmap" of how often each operand pair occurs.
- for (BasicBlock *BI : RPOT) {
- for (Instruction &I : *BI) {
- if (!I.isAssociative() || !I.isBinaryOp())
- continue;
-
- // Ignore nodes that aren't at the root of trees.
- if (I.hasOneUse() && I.user_back()->getOpcode() == I.getOpcode())
- continue;
-
- // Collect all operands in a single reassociable expression.
- // Since Reassociate has already been run once, we can assume things
- // are already canonical according to Reassociation's regime.
- SmallVector<Value *, 8> Worklist = { I.getOperand(0), I.getOperand(1) };
- SmallVector<Value *, 8> Ops;
- while (!Worklist.empty() && Ops.size() <= GlobalReassociateLimit) {
- Value *Op = Worklist.pop_back_val();
- Instruction *OpI = dyn_cast<Instruction>(Op);
- if (!OpI || OpI->getOpcode() != I.getOpcode() || !OpI->hasOneUse()) {
- Ops.push_back(Op);
- continue;
- }
- // Be paranoid about self-referencing expressions in unreachable code.
- if (OpI->getOperand(0) != OpI)
- Worklist.push_back(OpI->getOperand(0));
- if (OpI->getOperand(1) != OpI)
- Worklist.push_back(OpI->getOperand(1));
- }
- // Skip extremely long expressions.
- if (Ops.size() > GlobalReassociateLimit)
- continue;
-
- // Add all pairwise combinations of operands to the pair map.
- unsigned BinaryIdx = I.getOpcode() - Instruction::BinaryOpsBegin;
- SmallSet<std::pair<Value *, Value*>, 32> Visited;
- for (unsigned i = 0; i < Ops.size() - 1; ++i) {
- for (unsigned j = i + 1; j < Ops.size(); ++j) {
- // Canonicalize operand orderings.
- Value *Op0 = Ops[i];
- Value *Op1 = Ops[j];
- if (std::less<Value *>()(Op1, Op0))
- std::swap(Op0, Op1);
- if (!Visited.insert({Op0, Op1}).second)
- continue;
- auto res = PairMap[BinaryIdx].insert({{Op0, Op1}, {Op0, Op1, 1}});
- if (!res.second) {
- // If either key value has been erased then we've got the same
- // address by coincidence. That can't happen here because nothing is
- // erasing values but it can happen by the time we're querying the
- // map.
- assert(res.first->second.isValid() && "WeakVH invalidated");
- ++res.first->second.Score;
- }
- }
- }
- }
- }
-}
-
-PreservedAnalyses ReassociatePass::run(Function &F, FunctionAnalysisManager &) {
- // Get the functions basic blocks in Reverse Post Order. This order is used by
- // BuildRankMap to pre calculate ranks correctly. It also excludes dead basic
- // blocks (it has been seen that the analysis in this pass could hang when
- // analysing dead basic blocks).
- ReversePostOrderTraversal<Function *> RPOT(&F);
-
- // Calculate the rank map for F.
- BuildRankMap(F, RPOT);
-
- // Build the pair map before running reassociate.
- // Technically this would be more accurate if we did it after one round
- // of reassociation, but in practice it doesn't seem to help much on
- // real-world code, so don't waste the compile time running reassociate
- // twice.
- // If a user wants, they could expicitly run reassociate twice in their
- // pass pipeline for further potential gains.
- // It might also be possible to update the pair map during runtime, but the
- // overhead of that may be large if there's many reassociable chains.
- BuildPairMap(RPOT);
-
- MadeChange = false;
-
- // Traverse the same blocks that were analysed by BuildRankMap.
- for (BasicBlock *BI : RPOT) {
- assert(RankMap.count(&*BI) && "BB should be ranked.");
- // Optimize every instruction in the basic block.
- for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;)
- if (isInstructionTriviallyDead(&*II)) {
- EraseInst(&*II++);
- } else {
- OptimizeInst(&*II);
- assert(II->getParent() == &*BI && "Moved to a different block!");
- ++II;
- }
-
- // Make a copy of all the instructions to be redone so we can remove dead
- // instructions.
- OrderedSet ToRedo(RedoInsts);
- // Iterate over all instructions to be reevaluated and remove trivially dead
- // instructions. If any operand of the trivially dead instruction becomes
- // dead mark it for deletion as well. Continue this process until all
- // trivially dead instructions have been removed.
- while (!ToRedo.empty()) {
- Instruction *I = ToRedo.pop_back_val();
- if (isInstructionTriviallyDead(I)) {
- RecursivelyEraseDeadInsts(I, ToRedo);
- MadeChange = true;
- }
- }
-
- // Now that we have removed dead instructions, we can reoptimize the
- // remaining instructions.
- while (!RedoInsts.empty()) {
- Instruction *I = RedoInsts.front();
- RedoInsts.erase(RedoInsts.begin());
- if (isInstructionTriviallyDead(I))
- EraseInst(I);
- else
- OptimizeInst(I);
- }
- }
-
- // We are done with the rank map and pair map.
- RankMap.clear();
- ValueRankMap.clear();
- for (auto &Entry : PairMap)
- Entry.clear();
-
- if (MadeChange) {
- PreservedAnalyses PA;
- PA.preserveSet<CFGAnalyses>();
- return PA;
- }
-
- return PreservedAnalyses::all();
-}
-
-namespace {
-
-class ReassociateLegacyPass : public FunctionPass {
- ReassociatePass Impl;
-
-public:
- static char ID; // Pass identification, replacement for typeid
-
- ReassociateLegacyPass() : FunctionPass(ID) {
- initializeReassociateLegacyPassPass(*PassRegistry::getPassRegistry());
- }
-
- bool runOnFunction(Function &F) override {
- if (skipFunction(F))
- return false;
-
- FunctionAnalysisManager DummyFAM;
- auto PA = Impl.run(F, DummyFAM);
- return !PA.areAllPreserved();
- }
-
- void getAnalysisUsage(AnalysisUsage &AU) const override {
- AU.setPreservesCFG();
- AU.addPreserved<AAResultsWrapperPass>();
- AU.addPreserved<BasicAAWrapperPass>();
- AU.addPreserved<GlobalsAAWrapperPass>();
- }
-};
-
-} // end anonymous namespace
-
-char ReassociateLegacyPass::ID = 0;
-
-INITIALIZE_PASS(ReassociateLegacyPass, "reassociate",
- "Reassociate expressions", false, false)
-
-// Public interface to the Reassociate pass
-FunctionPass *llvm::createReassociatePass() {
- return new ReassociateLegacyPass();
-}
+ ? cast<Constant>(ConstantExpr::getNeg(C))
+ : C;
+
+ BinaryOperator *M1 =
+ BinaryOperator::CreateMul(AddSub->getOperand(0), C, "Mul1", Mul->getIterator());
+ BinaryOperator *M2 =
+ BinaryOperator::CreateMul(AddSub->getOperand(1), C2, "Mul2", Mul->getIterator());
+ BinaryOperator *Result;
+ Result = BinaryOperator::CreateAdd(M1, M2, "DistAdd", Mul->getIterator());
+
+ Mul->replaceAllUsesWith(Result);
+ Result->setDebugLoc(Mul->getDebugLoc());
+
+ ToRedo.insert(M1);
+ ToRedo.insert(M2);
+ ToRedo.insert(Result);
+
+ return Result;
+}
+
+/// Return true if we should break up this subtract of X-Y into (X + -Y).
+static bool ShouldBreakUpSubtract(Instruction *Sub) {
+ // If this is a negation, we can't split it up!
+ if (match(Sub, m_Neg(m_Value())) || match(Sub, m_FNeg(m_Value())))
+ return false;
+
+ // Don't breakup X - undef.
+ if (isa<UndefValue>(Sub->getOperand(1)))
+ return false;
+
+ // Don't bother to break this up unless either the LHS is an associable add or
+ // subtract or if this is only used by one.
+ Value *V0 = Sub->getOperand(0);
+ if (isReassociableOp(V0, Instruction::Add, Instruction::FAdd) ||
+ isReassociableOp(V0, Instruction::Sub, Instruction::FSub))
+ return true;
+ Value *V1 = Sub->getOperand(1);
+ if (isReassociableOp(V1, Instruction::Add, Instruction::FAdd) ||
+ isReassociableOp(V1, Instruction::Sub, Instruction::FSub))
+ return true;
+ Value *VB = Sub->user_back();
+ if (Sub->hasOneUse() &&
+ (isReassociableOp(VB, Instruction::Add, Instruction::FAdd) ||
+ isReassociableOp(VB, Instruction::Sub, Instruction::FSub)))
+ return true;
+
+ return false;
+}
+
+/// If we have (X-Y), and if either X is an add, or if this is only used by an
+/// add, transform this into (X+(0-Y)) to promote better reassociation.
+static BinaryOperator *BreakUpSubtract(Instruction *Sub,
+ ReassociatePass::OrderedSet &ToRedo) {
+ // Convert a subtract into an add and a neg instruction. This allows sub
+ // instructions to be commuted with other add instructions.
+ //
+ // Calculate the negative value of Operand 1 of the sub instruction,
+ // and set it as the RHS of the add instruction we just made.
+ Value *NegVal = NegateValue(Sub->getOperand(1), Sub, ToRedo);
+ BinaryOperator *New =
+ CreateAdd(Sub->getOperand(0), NegVal, "", Sub->getIterator(), Sub);
+ Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op.
+ Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op.
+ New->takeName(Sub);
+
+ // Everyone now refers to the add instruction.
+ Sub->replaceAllUsesWith(New);
+ New->setDebugLoc(Sub->getDebugLoc());
+
+ LLVM_DEBUG(dbgs() << "Negated: " << *New << '\n');
+ return New;
+}
+
+/// If this is a shift of a reassociable multiply or is used by one, change
+/// this into a multiply by a constant to assist with further reassociation.
+static BinaryOperator *ConvertShiftToMul(Instruction *Shl) {
+ Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
+ auto *SA = cast<ConstantInt>(Shl->getOperand(1));
+ MulCst = ConstantFoldBinaryInstruction(Instruction::Shl, MulCst, SA);
+ assert(MulCst && "Constant folding of immediate constants failed");
+
+ BinaryOperator *Mul = BinaryOperator::CreateMul(Shl->getOperand(0), MulCst,
+ "", Shl->getIterator());
+ Shl->setOperand(0, PoisonValue::get(Shl->getType())); // Drop use of op.
+ Mul->takeName(Shl);
+
+ // Everyone now refers to the mul instruction.
+ Shl->replaceAllUsesWith(Mul);
+ Mul->setDebugLoc(Shl->getDebugLoc());
+
+ // We can safely preserve the nuw flag in all cases. It's also safe to turn a
+ // nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special
+ // handling. It can be preserved as long as we're not left shifting by
+ // bitwidth - 1.
+ bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap();
+ bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap();
+ unsigned BitWidth = Shl->getType()->getScalarSizeInBits();
+ if (NSW && (NUW || SA->getValue().ult(BitWidth - 1)))
+ Mul->setHasNoSignedWrap(true);
+ Mul->setHasNoUnsignedWrap(NUW);
+ return Mul;
+}
+
+/// Scan backwards and forwards among values with the same rank as element i
+/// to see if X exists. If X does not exist, return i. This is useful when
+/// scanning for 'x' when we see '-x' because they both get the same rank.
+static unsigned FindInOperandList(const SmallVectorImpl<ValueEntry> &Ops,
+ unsigned i, Value *X) {
+ unsigned XRank = Ops[i].Rank;
+ unsigned e = Ops.size();
+ for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
+ if (Ops[j].Op == X)
+ return j;
+ if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
+ if (Instruction *I2 = dyn_cast<Instruction>(X))
+ if (I1->isIdenticalTo(I2))
+ return j;
+ }
+ // Scan backwards.
+ for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
+ if (Ops[j].Op == X)
+ return j;
+ if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
+ if (Instruction *I2 = dyn_cast<Instruction>(X))
+ if (I1->isIdenticalTo(I2))
+ return j;
+ }
+ return i;
+}
+
+/// Emit a tree of add instructions, summing Ops together
+/// and returning the result. Insert the tree before I.
+static Value *EmitAddTreeOfValues(Instruction *I,
+ SmallVectorImpl<WeakTrackingVH> &Ops) {
+ if (Ops.size() == 1) return Ops.back();
+
+ Value *V1 = Ops.pop_back_val();
+ Value *V2 = EmitAddTreeOfValues(I, Ops);
+ auto *NewAdd = CreateAdd(V2, V1, "reass.add", I->getIterator(), I);
+ NewAdd->setDebugLoc(I->getDebugLoc());
+ return NewAdd;
+}
+
+/// If V is an expression tree that is a multiplication sequence,
+/// and if this sequence contains a multiply by Factor,
+/// remove Factor from the tree and return the new tree.
+/// If new instructions are inserted to generate this tree, DL should be used
+/// as the DebugLoc for these instructions.
+Value *ReassociatePass::RemoveFactorFromExpression(Value *V, Value *Factor,
+ DebugLoc DL) {
+ BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
+ if (!BO)
+ return nullptr;
+
+ SmallVector<RepeatedValue, 8> Tree;
+ OverflowTracking Flags;
+ MadeChange |= LinearizeExprTree(BO, Tree, RedoInsts, Flags);
+ SmallVector<ValueEntry, 8> Factors;
+ Factors.reserve(Tree.size());
+ for (const RepeatedValue &E : Tree)
+ Factors.append(E.second, ValueEntry(getRank(E.first), E.first));
+
+ bool FoundFactor = false;
+ bool NeedsNegate = false;
+ for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
+ if (Factors[i].Op == Factor) {
+ FoundFactor = true;
+ Factors.erase(Factors.begin()+i);
+ break;
+ }
+
+ // If this is a negative version of this factor, remove it.
+ if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor)) {
+ if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
+ if (FC1->getValue() == -FC2->getValue()) {
+ FoundFactor = NeedsNegate = true;
+ Factors.erase(Factors.begin()+i);
+ break;
+ }
+ } else if (ConstantFP *FC1 = dyn_cast<ConstantFP>(Factor)) {
+ if (ConstantFP *FC2 = dyn_cast<ConstantFP>(Factors[i].Op)) {
+ const APFloat &F1 = FC1->getValueAPF();
+ APFloat F2(FC2->getValueAPF());
+ F2.changeSign();
+ if (F1 == F2) {
+ FoundFactor = NeedsNegate = true;
+ Factors.erase(Factors.begin() + i);
+ break;
+ }
+ }
+ }
+ }
+
+ if (!FoundFactor) {
+ // Make sure to restore the operands to the expression tree.
+ RewriteExprTree(BO, Factors, Flags);
+ return nullptr;
+ }
+
+ BasicBlock::iterator InsertPt = ++BO->getIterator();
+
+ // If this was just a single multiply, remove the multiply and return the only
+ // remaining operand.
+ if (Factors.size() == 1) {
+ RedoInsts.insert(BO);
+ V = Factors[0].Op;
+ } else {
+ RewriteExprTree(BO, Factors, Flags);
+ V = BO;
+ }
+
+ if (NeedsNegate) {
+ V = CreateNeg(V, "neg", InsertPt, BO);
+ cast<Instruction>(V)->setDebugLoc(DL);
+ }
+
+ return V;
+}
+
+/// If V is a single-use multiply, recursively add its operands as factors,
+/// otherwise add V to the list of factors.
+///
+/// Ops is the top-level list of add operands we're trying to factor.
+static void FindSingleUseMultiplyFactors(Value *V,
+ SmallVectorImpl<Value*> &Factors) {
+ BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
+ if (!BO) {
+ Factors.push_back(V);
+ return;
+ }
+
+ // Otherwise, add the LHS and RHS to the list of factors.
+ FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
+ FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
+}
+
+/// Optimize a series of operands to an 'and', 'or', or 'xor' instruction.
+/// This optimizes based on identities. If it can be reduced to a single Value,
+/// it is returned, otherwise the Ops list is mutated as necessary.
+static Value *OptimizeAndOrXor(unsigned Opcode,
+ SmallVectorImpl<ValueEntry> &Ops) {
+ // Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
+ // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
+ for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+ // First, check for X and ~X in the operand list.
+ assert(i < Ops.size());
+ Value *X;
+ if (match(Ops[i].Op, m_Not(m_Value(X)))) { // Cannot occur for ^.
+ unsigned FoundX = FindInOperandList(Ops, i, X);
+ if (FoundX != i) {
+ if (Opcode == Instruction::And) // ...&X&~X = 0
+ return Constant::getNullValue(X->getType());
+
+ if (Opcode == Instruction::Or) // ...|X|~X = -1
+ return Constant::getAllOnesValue(X->getType());
+ }
+ }
+
+ // Next, check for duplicate pairs of values, which we assume are next to
+ // each other, due to our sorting criteria.
+ assert(i < Ops.size());
+ if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
+ if (Opcode == Instruction::And || Opcode == Instruction::Or) {
+ // Drop duplicate values for And and Or.
+ Ops.erase(Ops.begin()+i);
+ --i; --e;
+ ++NumAnnihil;
+ continue;
+ }
+
+ // Drop pairs of values for Xor.
+ assert(Opcode == Instruction::Xor);
+ if (e == 2)
+ return Constant::getNullValue(Ops[0].Op->getType());
+
+ // Y ^ X^X -> Y
+ Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
+ i -= 1; e -= 2;
+ ++NumAnnihil;
+ }
+ }
+ return nullptr;
+}
+
+/// Helper function of CombineXorOpnd(). It creates a bitwise-and
+/// instruction with the given two operands, and return the resulting
+/// instruction. There are two special cases: 1) if the constant operand is 0,
+/// it will return NULL. 2) if the constant is ~0, the symbolic operand will
+/// be returned.
+static Value *createAndInstr(BasicBlock::iterator InsertBefore, Value *Opnd,
+ const APInt &ConstOpnd) {
+ if (ConstOpnd.isZero())
+ return nullptr;
+
+ if (ConstOpnd.isAllOnes())
+ return Opnd;
+
+ Instruction *I = BinaryOperator::CreateAnd(
+ Opnd, ConstantInt::get(Opnd->getType(), ConstOpnd), "and.ra",
+ InsertBefore);
+ I->setDebugLoc(InsertBefore->getDebugLoc());
+ return I;
+}
+
+// Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
+// into "R ^ C", where C would be 0, and R is a symbolic value.
+//
+// If it was successful, true is returned, and the "R" and "C" is returned
+// via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
+// and both "Res" and "ConstOpnd" remain unchanged.
+bool ReassociatePass::CombineXorOpnd(BasicBlock::iterator It, XorOpnd *Opnd1,
+ APInt &ConstOpnd, Value *&Res) {
+ // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
+ // = ((x | c1) ^ c1) ^ (c1 ^ c2)
+ // = (x & ~c1) ^ (c1 ^ c2)
+ // It is useful only when c1 == c2.
+ if (!Opnd1->isOrExpr() || Opnd1->getConstPart().isZero())
+ return false;
+
+ if (!Opnd1->getValue()->hasOneUse())
+ return false;
+
+ const APInt &C1 = Opnd1->getConstPart();
+ if (C1 != ConstOpnd)
+ return false;
+
+ Value *X = Opnd1->getSymbolicPart();
+ Res = createAndInstr(It, X, ~C1);
+ // ConstOpnd was C2, now C1 ^ C2.
+ ConstOpnd ^= C1;
+
+ if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
+ RedoInsts.insert(T);
+ return true;
+}
+
+// Helper function of OptimizeXor(). It tries to simplify
+// "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
+// symbolic value.
+//
+// If it was successful, true is returned, and the "R" and "C" is returned
+// via "Res" and "ConstOpnd", respectively (If the entire expression is
+// evaluated to a constant, the Res is set to NULL); otherwise, false is
+// returned, and both "Res" and "ConstOpnd" remain unchanged.
+bool ReassociatePass::CombineXorOpnd(BasicBlock::iterator It, XorOpnd *Opnd1,
+ XorOpnd *Opnd2, APInt &ConstOpnd,
+ Value *&Res) {
+ Value *X = Opnd1->getSymbolicPart();
+ if (X != Opnd2->getSymbolicPart())
+ return false;
+
+ // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
+ int DeadInstNum = 1;
+ if (Opnd1->getValue()->hasOneUse())
+ DeadInstNum++;
+ if (Opnd2->getValue()->hasOneUse())
+ DeadInstNum++;
+
+ // Xor-Rule 2:
+ // (x | c1) ^ (x & c2)
+ // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
+ // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
+ // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
+ //
+ if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
+ if (Opnd2->isOrExpr())
+ std::swap(Opnd1, Opnd2);
+
+ const APInt &C1 = Opnd1->getConstPart();
+ const APInt &C2 = Opnd2->getConstPart();
+ APInt C3((~C1) ^ C2);
+
+ // Do not increase code size!
+ if (!C3.isZero() && !C3.isAllOnes()) {
+ int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
+ if (NewInstNum > DeadInstNum)
+ return false;
+ }
+
+ Res = createAndInstr(It, X, C3);
+ ConstOpnd ^= C1;
+ } else if (Opnd1->isOrExpr()) {
+ // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
+ //
+ const APInt &C1 = Opnd1->getConstPart();
+ const APInt &C2 = Opnd2->getConstPart();
+ APInt C3 = C1 ^ C2;
+
+ // Do not increase code size
+ if (!C3.isZero() && !C3.isAllOnes()) {
+ int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
+ if (NewInstNum > DeadInstNum)
+ return false;
+ }
+
+ Res = createAndInstr(It, X, C3);
+ ConstOpnd ^= C3;
+ } else {
+ // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
+ //
+ const APInt &C1 = Opnd1->getConstPart();
+ const APInt &C2 = Opnd2->getConstPart();
+ APInt C3 = C1 ^ C2;
+ Res = createAndInstr(It, X, C3);
+ }
+
+ // Put the original operands in the Redo list; hope they will be deleted
+ // as dead code.
+ if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
+ RedoInsts.insert(T);
+ if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
+ RedoInsts.insert(T);
+
+ return true;
+}
+
+/// Optimize a series of operands to an 'xor' instruction. If it can be reduced
+/// to a single Value, it is returned, otherwise the Ops list is mutated as
+/// necessary.
+Value *ReassociatePass::OptimizeXor(Instruction *I,
+ SmallVectorImpl<ValueEntry> &Ops) {
+ if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
+ return V;
+
+ if (Ops.size() == 1)
+ return nullptr;
+
+ SmallVector<XorOpnd, 8> Opnds;
+ SmallVector<XorOpnd*, 8> OpndPtrs;
+ Type *Ty = Ops[0].Op->getType();
+ APInt ConstOpnd(Ty->getScalarSizeInBits(), 0);
+
+ // Step 1: Convert ValueEntry to XorOpnd
+ for (const ValueEntry &Op : Ops) {
+ Value *V = Op.Op;
+ const APInt *C;
+ // TODO: Support non-splat vectors.
+ if (match(V, m_APInt(C))) {
+ ConstOpnd ^= *C;
+ } else {
+ XorOpnd O(V);
+ O.setSymbolicRank(getRank(O.getSymbolicPart()));
+ Opnds.push_back(O);
+ }
+ }
+
+ // NOTE: From this point on, do *NOT* add/delete element to/from "Opnds".
+ // It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate
+ // the "OpndPtrs" as well. For the similar reason, do not fuse this loop
+ // with the previous loop --- the iterator of the "Opnds" may be invalidated
+ // when new elements are added to the vector.
+ for (XorOpnd &Op : Opnds)
+ OpndPtrs.push_back(&Op);
+
+ // Step 2: Sort the Xor-Operands in a way such that the operands containing
+ // the same symbolic value cluster together. For instance, the input operand
+ // sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
+ // ("x | 123", "x & 789", "y & 456").
+ //
+ // The purpose is twofold:
+ // 1) Cluster together the operands sharing the same symbolic-value.
+ // 2) Operand having smaller symbolic-value-rank is permuted earlier, which
+ // could potentially shorten crital path, and expose more loop-invariants.
+ // Note that values' rank are basically defined in RPO order (FIXME).
+ // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
+ // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
+ // "z" in the order of X-Y-Z is better than any other orders.
+ llvm::stable_sort(OpndPtrs, [](XorOpnd *LHS, XorOpnd *RHS) {
+ return LHS->getSymbolicRank() < RHS->getSymbolicRank();
+ });
+
+ // Step 3: Combine adjacent operands
+ XorOpnd *PrevOpnd = nullptr;
+ bool Changed = false;
+ for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
+ XorOpnd *CurrOpnd = OpndPtrs[i];
+ // The combined value
+ Value *CV;
+
+ // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
+ if (!ConstOpnd.isZero() &&
+ CombineXorOpnd(I->getIterator(), CurrOpnd, ConstOpnd, CV)) {
+ Changed = true;
+ if (CV)
+ *CurrOpnd = XorOpnd(CV);
+ else {
+ CurrOpnd->Invalidate();
+ continue;
+ }
+ }
+
+ if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
+ PrevOpnd = CurrOpnd;
+ continue;
+ }
+
+ // step 3.2: When previous and current operands share the same symbolic
+ // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
+ if (CombineXorOpnd(I->getIterator(), CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
+ // Remove previous operand
+ PrevOpnd->Invalidate();
+ if (CV) {
+ *CurrOpnd = XorOpnd(CV);
+ PrevOpnd = CurrOpnd;
+ } else {
+ CurrOpnd->Invalidate();
+ PrevOpnd = nullptr;
+ }
+ Changed = true;
+ }
+ }
+
+ // Step 4: Reassemble the Ops
+ if (Changed) {
+ Ops.clear();
+ for (const XorOpnd &O : Opnds) {
+ if (O.isInvalid())
+ continue;
+ ValueEntry VE(getRank(O.getValue()), O.getValue());
+ Ops.push_back(VE);
+ }
+ if (!ConstOpnd.isZero()) {
+ Value *C = ConstantInt::get(Ty, ConstOpnd);
+ ValueEntry VE(getRank(C), C);
+ Ops.push_back(VE);
+ }
+ unsigned Sz = Ops.size();
+ if (Sz == 1)
+ return Ops.back().Op;
+ if (Sz == 0) {
+ assert(ConstOpnd.isZero());
+ return ConstantInt::get(Ty, ConstOpnd);
+ }
+ }
+
+ return nullptr;
+}
+
+/// Optimize a series of operands to an 'add' instruction. This
+/// optimizes based on identities. If it can be reduced to a single Value, it
+/// is returned, otherwise the Ops list is mutated as necessary.
+Value *ReassociatePass::OptimizeAdd(Instruction *I,
+ SmallVectorImpl<ValueEntry> &Ops) {
+ // Scan the operand lists looking for X and -X pairs. If we find any, we
+ // can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it,
+ // scan for any
+ // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
+
+ for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+ Value *TheOp = Ops[i].Op;
+ // Check to see if we've seen this operand before. If so, we factor all
+ // instances of the operand together. Due to our sorting criteria, we know
+ // that these need to be next to each other in the vector.
+ if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
+ // Rescan the list, remove all instances of this operand from the expr.
+ unsigned NumFound = 0;
+ do {
+ Ops.erase(Ops.begin()+i);
+ ++NumFound;
+ } while (i != Ops.size() && Ops[i].Op == TheOp);
+
+ LLVM_DEBUG(dbgs() << "\nFACTORING [" << NumFound << "]: " << *TheOp
+ << '\n');
+ ++NumFactor;
+
+ // Insert a new multiply.
+ Type *Ty = TheOp->getType();
+ // Truncate if NumFound overflows the type.
+ Constant *C = Ty->isIntOrIntVectorTy()
+ ? ConstantInt::get(Ty, NumFound, /*IsSigned=*/false,
+ /*ImplicitTrunc=*/true)
+ : ConstantFP::get(Ty, NumFound);
+ Instruction *Mul = CreateMul(TheOp, C, "factor", I->getIterator(), I);
+ Mul->setDebugLoc(I->getDebugLoc());
+
+ // Now that we have inserted a multiply, optimize it. This allows us to
+ // handle cases that require multiple factoring steps, such as this:
+ // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
+ RedoInsts.insert(Mul);
+
+ // If every add operand was a duplicate, return the multiply.
+ if (Ops.empty())
+ return Mul;
+
+ // Otherwise, we had some input that didn't have the dupe, such as
+ // "A + A + B" -> "A*2 + B". Add the new multiply to the list of
+ // things being added by this operation.
+ Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
+
+ --i;
+ e = Ops.size();
+ continue;
+ }
+
+ // Check for X and -X or X and ~X in the operand list.
+ Value *X;
+ if (!match(TheOp, m_Neg(m_Value(X))) && !match(TheOp, m_Not(m_Value(X))) &&
+ !match(TheOp, m_FNeg(m_Value(X))))
+ continue;
+
+ unsigned FoundX = FindInOperandList(Ops, i, X);
+ if (FoundX == i)
+ continue;
+
+ // Remove X and -X from the operand list.
+ if (Ops.size() == 2 &&
+ (match(TheOp, m_Neg(m_Value())) || match(TheOp, m_FNeg(m_Value()))))
+ return Constant::getNullValue(X->getType());
+
+ // Remove X and ~X from the operand list.
+ if (Ops.size() == 2 && match(TheOp, m_Not(m_Value())))
+ return Constant::getAllOnesValue(X->getType());
+
+ Ops.erase(Ops.begin()+i);
+ if (i < FoundX)
+ --FoundX;
+ else
+ --i; // Need to back up an extra one.
+ Ops.erase(Ops.begin()+FoundX);
+ ++NumAnnihil;
+ --i; // Revisit element.
+ e -= 2; // Removed two elements.
+
+ // if X and ~X we append -1 to the operand list.
+ if (match(TheOp, m_Not(m_Value()))) {
+ Value *V = Constant::getAllOnesValue(X->getType());
+ Ops.insert(Ops.end(), ValueEntry(getRank(V), V));
+ e += 1;
+ }
+ }
+
+ // Scan the operand list, checking to see if there are any common factors
+ // between operands. Consider something like A*A+A*B*C+D. We would like to
+ // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
+ // To efficiently find this, we count the number of times a factor occurs
+ // for any ADD operands that are MULs.
+ DenseMap<Value*, unsigned> FactorOccurrences;
+
+ // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
+ // where they are actually the same multiply.
+ unsigned MaxOcc = 0;
+ Value *MaxOccVal = nullptr;
+
+ // Prefer a non-constant factor over a constant when occurrence counts
+ // tie. Factoring out a variable (e.g., X from X*C1 + X*C2) exposes
+ // downstream constant folding; factoring out a constant does not.
+ auto IsBetterFactor = [](Value *Factor, Value *MaxOccVal, unsigned Occ,
+ unsigned MaxOcc) {
+ return Occ > MaxOcc ||
+ (Occ == MaxOcc &&
+ (isa<Instruction>(Factor) || isa<Argument>(Factor)) &&
+ isa<Constant>(MaxOccVal) && !isa<UndefValue>(MaxOccVal));
+ };
+ for (const ValueEntry &Op : Ops) {
+ BinaryOperator *BOp =
+ isReassociableOp(Op.Op, Instruction::Mul, Instruction::FMul);
+ if (!BOp)
+ continue;
+
+ // Compute all of the factors of this added value.
+ SmallVector<Value*, 8> Factors;
+ FindSingleUseMultiplyFactors(BOp, Factors);
+ assert(Factors.size() > 1 && "Bad linearize!");
+
+ // Add one to FactorOccurrences for each unique factor in this op.
+ SmallPtrSet<Value*, 8> Duplicates;
+ for (Value *Factor : Factors) {
+ if (!Duplicates.insert(Factor).second)
+ continue;
+
+ unsigned Occ = ++FactorOccurrences[Factor];
+ if (IsBetterFactor(Factor, MaxOccVal, Occ, MaxOcc)) {
+ MaxOcc = Occ;
+ MaxOccVal = Factor;
+ }
+
+ // If Factor is a negative constant, add the negated value as a factor
+ // because we can percolate the negate out. Watch for minint, which
+ // cannot be positivified.
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor)) {
+ if (CI->isNegative() && !CI->isMinValue(true)) {
+ Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
+ if (!Duplicates.insert(Factor).second)
+ continue;
+ unsigned Occ = ++FactorOccurrences[Factor];
+ if (IsBetterFactor(Factor, MaxOccVal, Occ, MaxOcc)) {
+ MaxOcc = Occ;
+ MaxOccVal = Factor;
+ }
+ }
+ } else if (ConstantFP *CF = dyn_cast<ConstantFP>(Factor)) {
+ if (CF->isNegative()) {
+ APFloat F(CF->getValueAPF());
+ F.changeSign();
+ Factor = ConstantFP::get(CF->getType(), F);
+ if (!Duplicates.insert(Factor).second)
+ continue;
+ unsigned Occ = ++FactorOccurrences[Factor];
+ if (IsBetterFactor(Factor, MaxOccVal, Occ, MaxOcc)) {
+ MaxOcc = Occ;
+ MaxOccVal = Factor;
+ }
+ }
+ }
+ }
+ }
+
+ // If any factor occurred more than one time, we can pull it out.
+ if (MaxOcc > 1) {
+ LLVM_DEBUG(dbgs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal
+ << '\n');
+ ++NumFactor;
+
+ // Create a new instruction that uses the MaxOccVal twice. If we don't do
+ // this, we could otherwise run into situations where removing a factor
+ // from an expression will drop a use of maxocc, and this can cause
+ // RemoveFactorFromExpression on successive values to behave differently.
+ Instruction *DummyInst =
+ I->getType()->isIntOrIntVectorTy()
+ ? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal)
+ : BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal);
+
+ SmallVector<WeakTrackingVH, 4> NewMulOps;
+ for (unsigned i = 0; i != Ops.size(); ++i) {
+ // Only try to remove factors from expressions we're allowed to.
+ BinaryOperator *BOp =
+ isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
+ if (!BOp)
+ continue;
+
+ if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal,
+ I->getDebugLoc())) {
+ // The factorized operand may occur several times. Convert them all in
+ // one fell swoop.
+ for (unsigned j = Ops.size(); j != i;) {
+ --j;
+ if (Ops[j].Op == Ops[i].Op) {
+ NewMulOps.push_back(V);
+ Ops.erase(Ops.begin()+j);
+ }
+ }
+ --i;
+ }
+ }
+
+ // No need for extra uses anymore.
+ DummyInst->deleteValue();
+
+ unsigned NumAddedValues = NewMulOps.size();
+ Value *V = EmitAddTreeOfValues(I, NewMulOps);
+
+ // Now that we have inserted the add tree, optimize it. This allows us to
+ // handle cases that require multiple factoring steps, such as this:
+ // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
+ assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
+ (void)NumAddedValues;
+ if (Instruction *VI = dyn_cast<Instruction>(V))
+ RedoInsts.insert(VI);
+
+ // Create the multiply.
+ Instruction *V2 = CreateMul(V, MaxOccVal, "reass.mul", I->getIterator(), I);
+ V2->setDebugLoc(I->getDebugLoc());
+
+ // Rerun associate on the multiply in case the inner expression turned into
+ // a multiply. We want to make sure that we keep things in canonical form.
+ RedoInsts.insert(V2);
+
+ // If every add operand included the factor (e.g. "A*B + A*C"), then the
+ // entire result expression is just the multiply "A*(B+C)".
+ if (Ops.empty())
+ return V2;
+
+ // Otherwise, we had some input that didn't have the factor, such as
+ // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
+ // things being added by this operation.
+ Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
+ }
+
+ return nullptr;
+}
+
+/// Build up a vector of value/power pairs factoring a product.
+///
+/// Given a series of multiplication operands, build a vector of factors and
+/// the powers each is raised to when forming the final product. Sort them in
+/// the order of descending power.
+///
+/// (x*x) -> [(x, 2)]
+/// ((x*x)*x) -> [(x, 3)]
+/// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
+///
+/// \returns Whether any factors have a power greater than one.
+static bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
+ SmallVectorImpl<Factor> &Factors) {
+ // FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this.
+ // Compute the sum of powers of simplifiable factors.
+ unsigned FactorPowerSum = 0;
+ for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) {
+ Value *Op = Ops[Idx-1].Op;
+
+ // Count the number of occurrences of this value.
+ unsigned Count = 1;
+ for (; Idx < Size && Ops[Idx].Op == Op; ++Idx)
+ ++Count;
+ // Track for simplification all factors which occur 2 or more times.
+ if (Count > 1)
+ FactorPowerSum += Count;
+ }
+
+ // We can only simplify factors if the sum of the powers of our simplifiable
+ // factors is 4 or higher. When that is the case, we will *always* have
+ // a simplification. This is an important invariant to prevent cyclicly
+ // trying to simplify already minimal formations.
+ if (FactorPowerSum < 4)
+ return false;
+
+ // Now gather the simplifiable factors, removing them from Ops.
+ FactorPowerSum = 0;
+ for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) {
+ Value *Op = Ops[Idx-1].Op;
+
+ // Count the number of occurrences of this value.
+ unsigned Count = 1;
+ for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx)
+ ++Count;
+ if (Count == 1)
+ continue;
+ // Move an even number of occurrences to Factors.
+ Count &= ~1U;
+ Idx -= Count;
+ FactorPowerSum += Count;
+ Factors.push_back(Factor(Op, Count));
+ Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count);
+ }
+
+ // None of the adjustments above should have reduced the sum of factor powers
+ // below our mininum of '4'.
+ assert(FactorPowerSum >= 4);
+
+ llvm::stable_sort(Factors, [](const Factor &LHS, const Factor &RHS) {
+ return LHS.Power > RHS.Power;
+ });
+ return true;
+}
+
+/// Build a tree of multiplies, computing the product of Ops.
+static Value *buildMultiplyTree(IRBuilderBase &Builder,
+ SmallVectorImpl<Value*> &Ops) {
+ if (Ops.size() == 1)
+ return Ops.back();
+
+ Value *LHS = Ops.pop_back_val();
+ do {
+ if (LHS->getType()->isIntOrIntVectorTy())
+ LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
+ else
+ LHS = Builder.CreateFMul(LHS, Ops.pop_back_val());
+ } while (!Ops.empty());
+
+ return LHS;
+}
+
+/// Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
+///
+/// Given a vector of values raised to various powers, where no two values are
+/// equal and the powers are sorted in decreasing order, compute the minimal
+/// DAG of multiplies to compute the final product, and return that product
+/// value.
+Value *
+ReassociatePass::buildMinimalMultiplyDAG(IRBuilderBase &Builder,
+ SmallVectorImpl<Factor> &Factors) {
+ assert(Factors[0].Power);
+ SmallVector<Value *, 4> OuterProduct;
+ for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
+ Idx < Size && Factors[Idx].Power > 0; ++Idx) {
+ if (Factors[Idx].Power != Factors[LastIdx].Power) {
+ LastIdx = Idx;
+ continue;
+ }
+
+ // We want to multiply across all the factors with the same power so that
+ // we can raise them to that power as a single entity. Build a mini tree
+ // for that.
+ SmallVector<Value *, 4> InnerProduct;
+ InnerProduct.push_back(Factors[LastIdx].Base);
+ do {
+ InnerProduct.push_back(Factors[Idx].Base);
+ ++Idx;
+ } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
+
+ // Reset the base value of the first factor to the new expression tree.
+ // We'll remove all the factors with the same power in a second pass.
+ Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
+ if (Instruction *MI = dyn_cast<Instruction>(M))
+ RedoInsts.insert(MI);
+
+ LastIdx = Idx;
+ }
+ // Unique factors with equal powers -- we've folded them into the first one's
+ // base.
+ Factors.erase(llvm::unique(Factors,
+ [](const Factor &LHS, const Factor &RHS) {
+ return LHS.Power == RHS.Power;
+ }),
+ Factors.end());
+
+ // Iteratively collect the base of each factor with an add power into the
+ // outer product, and halve each power in preparation for squaring the
+ // expression.
+ for (Factor &F : Factors) {
+ if (F.Power & 1)
+ OuterProduct.push_back(F.Base);
+ F.Power >>= 1;
+ }
+ if (Factors[0].Power) {
+ Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
+ OuterProduct.push_back(SquareRoot);
+ OuterProduct.push_back(SquareRoot);
+ }
+ if (OuterProduct.size() == 1)
+ return OuterProduct.front();
+
+ Value *V = buildMultiplyTree(Builder, OuterProduct);
+ return V;
+}
+
+Value *ReassociatePass::OptimizeMul(BinaryOperator *I,
+ SmallVectorImpl<ValueEntry> &Ops) {
+ // We can only optimize the multiplies when there is a chain of more than
+ // three, such that a balanced tree might require fewer total multiplies.
+ if (Ops.size() < 4)
+ return nullptr;
+
+ // Try to turn linear trees of multiplies without other uses of the
+ // intermediate stages into minimal multiply DAGs with perfect sub-expression
+ // re-use.
+ SmallVector<Factor, 4> Factors;
+ if (!collectMultiplyFactors(Ops, Factors))
+ return nullptr; // All distinct factors, so nothing left for us to do.
+
+ IRBuilder<> Builder(I);
+ // The reassociate transformation for FP operations is performed only
+ // if unsafe algebra is permitted by FastMathFlags. Propagate those flags
+ // to the newly generated operations.
+ if (auto FPI = dyn_cast<FPMathOperator>(I))
+ Builder.setFastMathFlags(FPI->getFastMathFlags());
+
+ Value *V = buildMinimalMultiplyDAG(Builder, Factors);
+ if (Ops.empty())
+ return V;
+
+ ValueEntry NewEntry = ValueEntry(getRank(V), V);
+ Ops.insert(llvm::lower_bound(Ops, NewEntry), NewEntry);
+ return nullptr;
+}
+
+Value *ReassociatePass::OptimizeExpression(BinaryOperator *I,
+ SmallVectorImpl<ValueEntry> &Ops) {
+ // Now that we have the linearized expression tree, try to optimize it.
+ // Start by folding any constants that we found.
+ const DataLayout &DL = I->getDataLayout();
+ Constant *Cst = nullptr;
+ unsigned Opcode = I->getOpcode();
+ while (!Ops.empty()) {
+ if (auto *C = dyn_cast<Constant>(Ops.back().Op)) {
+ if (!Cst) {
+ Ops.pop_back();
+ Cst = C;
+ continue;
+ }
+ if (Constant *Res = ConstantFoldBinaryOpOperands(Opcode, C, Cst, DL)) {
+ Ops.pop_back();
+ Cst = Res;
+ continue;
+ }
+ }
+ break;
+ }
+ // If there was nothing but constants then we are done.
+ if (Ops.empty())
+ return Cst;
+
+ // Put the combined constant back at the end of the operand list, except if
+ // there is no point. For example, an add of 0 gets dropped here, while a
+ // multiplication by zero turns the whole expression into zero.
+ if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) {
+ if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType()))
+ return Cst;
+ Ops.push_back(ValueEntry(0, Cst));
+ }
+
+ if (Ops.size() == 1) return Ops[0].Op;
+
+ // Handle destructive annihilation due to identities between elements in the
+ // argument list here.
+ unsigned NumOps = Ops.size();
+ switch (Opcode) {
+ default: break;
+ case Instruction::And:
+ case Instruction::Or:
+ if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
+ return Result;
+ break;
+
+ case Instruction::Xor:
+ if (Value *Result = OptimizeXor(I, Ops))
+ return Result;
+ break;
+
+ case Instruction::Add:
+ case Instruction::FAdd:
+ if (Value *Result = OptimizeAdd(I, Ops))
+ return Result;
+ break;
+
+ case Instruction::Mul:
+ case Instruction::FMul:
+ if (Value *Result = OptimizeMul(I, Ops))
+ return Result;
+ break;
+ }
+
+ if (Ops.size() != NumOps)
+ return OptimizeExpression(I, Ops);
+ return nullptr;
+}
+
+// Remove dead instructions and if any operands are trivially dead add them to
+// Insts so they will be removed as well.
+void ReassociatePass::RecursivelyEraseDeadInsts(Instruction *I,
+ OrderedSet &Insts) {
+ assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
+ SmallVector<Value *, 4> Ops(I->operands());
+ ValueRankMap.erase(I);
+ Insts.remove(I);
+ RedoInsts.remove(I);
+ llvm::salvageDebugInfo(*I);
+ I->eraseFromParent();
+ for (auto *Op : Ops)
+ if (Instruction *OpInst = dyn_cast<Instruction>(Op))
+ if (OpInst->use_empty())
+ Insts.insert(OpInst);
+}
+
+/// Zap the given instruction, adding interesting operands to the work list.
+void ReassociatePass::EraseInst(Instruction *I) {
+ assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
+ LLVM_DEBUG(dbgs() << "Erasing dead inst: "; I->dump());
+
+ SmallVector<Value *, 8> Ops(I->operands());
+ // Erase the dead instruction.
+ ValueRankMap.erase(I);
+ RedoInsts.remove(I);
+ llvm::salvageDebugInfo(*I);
+ I->eraseFromParent();
+ // Optimize its operands.
+ SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
+ for (Value *V : Ops)
+ if (Instruction *Op = dyn_cast<Instruction>(V)) {
+ // If this is a node in an expression tree, climb to the expression root
+ // and add that since that's where optimization actually happens.
+ unsigned Opcode = Op->getOpcode();
+ while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode &&
+ Visited.insert(Op).second)
+ Op = Op->user_back();
+
+ // The instruction we're going to push may be coming from a
+ // dead block, and Reassociate skips the processing of unreachable
+ // blocks because it's a waste of time and also because it can
+ // lead to infinite loop due to LLVM's non-standard definition
+ // of dominance.
+ if (ValueRankMap.contains(Op))
+ RedoInsts.insert(Op);
+ }
+
+ MadeChange = true;
+}
+
+/// Recursively analyze an expression to build a list of instructions that have
+/// negative floating-point constant operands. The caller can then transform
+/// the list to create positive constants for better reassociation and CSE.
+static void getNegatibleInsts(Value *V,
+ SmallVectorImpl<Instruction *> &Candidates) {
+ // Handle only one-use instructions. Combining negations does not justify
+ // replicating instructions.
+ Instruction *I;
+ if (!match(V, m_OneUse(m_Instruction(I))))
+ return;
+
+ // Handle expressions of multiplications and divisions.
+ // TODO: This could look through floating-point casts.
+ const APFloat *C;
+ switch (I->getOpcode()) {
+ case Instruction::FMul:
+ // Not expecting non-canonical code here. Bail out and wait.
+ if (match(I->getOperand(0), m_Constant()))
+ break;
+
+ if (match(I->getOperand(1), m_APFloat(C)) && C->isNegative()) {
+ Candidates.push_back(I);
+ LLVM_DEBUG(dbgs() << "FMul with negative constant: " << *I << '\n');
+ }
+ getNegatibleInsts(I->getOperand(0), Candidates);
+ getNegatibleInsts(I->getOperand(1), Candidates);
+ break;
+ case Instruction::FDiv:
+ // Not expecting non-canonical code here. Bail out and wait.
+ if (match(I->getOperand(0), m_Constant()) &&
+ match(I->getOperand(1), m_Constant()))
+ break;
+
+ if ((match(I->getOperand(0), m_APFloat(C)) && C->isNegative()) ||
+ (match(I->getOperand(1), m_APFloat(C)) && C->isNegative())) {
+ Candidates.push_back(I);
+ LLVM_DEBUG(dbgs() << "FDiv with negative constant: " << *I << '\n');
+ }
+ getNegatibleInsts(I->getOperand(0), Candidates);
+ getNegatibleInsts(I->getOperand(1), Candidates);
+ break;
+ default:
+ break;
+ }
+}
+
+/// Given an fadd/fsub with an operand that is a one-use instruction
+/// (the fadd/fsub), try to change negative floating-point constants into
+/// positive constants to increase potential for reassociation and CSE.
+Instruction *ReassociatePass::canonicalizeNegFPConstantsForOp(Instruction *I,
+ Instruction *Op,
+ Value *OtherOp) {
+ assert((I->getOpcode() == Instruction::FAdd ||
+ I->getOpcode() == Instruction::FSub) && "Expected fadd/fsub");
+
+ // Collect instructions with negative FP constants from the subtree that ends
+ // in Op.
+ SmallVector<Instruction *, 4> Candidates;
+ getNegatibleInsts(Op, Candidates);
+ if (Candidates.empty())
+ return nullptr;
+
+ // Don't canonicalize x + (-Constant * y) -> x - (Constant * y), if the
+ // resulting subtract will be broken up later. This can get us into an
+ // infinite loop during reassociation.
+ bool IsFSub = I->getOpcode() == Instruction::FSub;
+ bool NeedsSubtract = !IsFSub && Candidates.size() % 2 == 1;
+ if (NeedsSubtract && ShouldBreakUpSubtract(I))
+ return nullptr;
+
+ for (Instruction *Negatible : Candidates) {
+ const APFloat *C;
+ if (match(Negatible->getOperand(0), m_APFloat(C))) {
+ assert(!match(Negatible->getOperand(1), m_Constant()) &&
+ "Expecting only 1 constant operand");
+ assert(C->isNegative() && "Expected negative FP constant");
+ Negatible->setOperand(0, ConstantFP::get(Negatible->getType(), abs(*C)));
+ MadeChange = true;
+ }
+ if (match(Negatible->getOperand(1), m_APFloat(C))) {
+ assert(!match(Negatible->getOperand(0), m_Constant()) &&
+ "Expecting only 1 constant operand");
+ assert(C->isNegative() && "Expected negative FP constant");
+ Negatible->setOperand(1, ConstantFP::get(Negatible->getType(), abs(*C)));
+ MadeChange = true;
+ }
+ }
+ assert(MadeChange == true && "Negative constant candidate was not changed");
+
+ // Negations cancelled out.
+ if (Candidates.size() % 2 == 0)
+ return I;
+
+ // Negate the final operand in the expression by flipping the opcode of this
+ // fadd/fsub.
+ assert(Candidates.size() % 2 == 1 && "Expected odd number");
+ IRBuilder<> Builder(I);
+ Value *NewInst = IsFSub ? Builder.CreateFAddFMF(OtherOp, Op, I)
+ : Builder.CreateFSubFMF(OtherOp, Op, I);
+ I->replaceAllUsesWith(NewInst);
+ RedoInsts.insert(I);
+ return dyn_cast<Instruction>(NewInst);
+}
+
+/// Canonicalize expressions that contain a negative floating-point constant
+/// of the following form:
+/// OtherOp + (subtree) -> OtherOp {+/-} (canonical subtree)
+/// (subtree) + OtherOp -> OtherOp {+/-} (canonical subtree)
+/// OtherOp - (subtree) -> OtherOp {+/-} (canonical subtree)
+///
+/// The fadd/fsub opcode may be switched to allow folding a negation into the
+/// input instruction.
+Instruction *ReassociatePass::canonicalizeNegFPConstants(Instruction *I) {
+ LLVM_DEBUG(dbgs() << "Combine negations for: " << *I << '\n');
+ Value *X;
+ Instruction *Op;
+ if (match(I, m_FAdd(m_Value(X), m_OneUse(m_Instruction(Op)))))
+ if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X))
+ I = R;
+ if (match(I, m_FAdd(m_OneUse(m_Instruction(Op)), m_Value(X))))
+ if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X))
+ I = R;
+ if (match(I, m_FSub(m_Value(X), m_OneUse(m_Instruction(Op)))))
+ if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X))
+ I = R;
+ return I;
+}
+
+/// Inspect and optimize the given instruction. Note that erasing
+/// instructions is not allowed.
+void ReassociatePass::OptimizeInst(Instruction *I) {
+ // Only consider operations that we understand.
+ if (!isa<UnaryOperator>(I) && !isa<BinaryOperator>(I))
+ return;
+
+ if (I->getOpcode() == Instruction::Shl && isa<ConstantInt>(I->getOperand(1)))
+ // If an operand of this shift is a reassociable multiply, or if the shift
+ // is used by a reassociable multiply or add, turn into a multiply.
+ if (isReassociableOp(I->getOperand(0), Instruction::Mul) ||
+ (I->hasOneUse() &&
+ (isReassociableOp(I->user_back(), Instruction::Mul) ||
+ isReassociableOp(I->user_back(), Instruction::Add)))) {
+ Instruction *NI = ConvertShiftToMul(I);
+ RedoInsts.insert(I);
+ MadeChange = true;
+ I = NI;
+ }
+
+ // Commute binary operators, to canonicalize the order of their operands.
+ // This can potentially expose more CSE opportunities, and makes writing other
+ // transformations simpler.
+ if (I->isCommutative())
+ canonicalizeOperands(I);
+
+ // Canonicalize negative constants out of expressions.
+ if (Instruction *Res = canonicalizeNegFPConstants(I))
+ I = Res;
+
+ // Don't optimize floating-point instructions unless they have the
+ // appropriate FastMathFlags for reassociation enabled.
+ if (isa<FPMathOperator>(I) && !hasFPAssociativeFlags(I))
+ return;
+
+ // Do not reassociate boolean (i1/vXi1) expressions. We want to preserve the
+ // original order of evaluation for short-circuited comparisons that
+ // SimplifyCFG has folded to AND/OR expressions. If the expression
+ // is not further optimized, it is likely to be transformed back to a
+ // short-circuited form for code gen, and the source order may have been
+ // optimized for the most likely conditions. For vector boolean expressions,
+ // we should be optimizing for ILP and not serializing the logical operations.
+ if (I->getType()->isIntOrIntVectorTy(1))
+ return;
+
+ // If this is a bitwise or instruction of operands
+ // with no common bits set, convert it to X+Y.
+ if (I->getOpcode() == Instruction::Or &&
+ shouldConvertOrWithNoCommonBitsToAdd(I) && !isLoadCombineCandidate(I) &&
+ (cast<PossiblyDisjointInst>(I)->isDisjoint() ||
+ haveNoCommonBitsSet(I->getOperand(0), I->getOperand(1),
+ SimplifyQuery(I->getDataLayout(),
+ /*DT=*/nullptr, /*AC=*/nullptr, I)))) {
+ Instruction *NI = convertOrWithNoCommonBitsToAdd(I);
+ RedoInsts.insert(I);
+ MadeChange = true;
+ I = NI;
+ }
+
+ if (I->getOpcode() == Instruction::Mul && ShouldBreakUpDistribution(I)) {
+ Instruction *MulUser = cast<Instruction>(I->user_back());
+ BreakUpDistribute(I, RedoInsts);
+ RedoInsts.insert(I);
+ RedoInsts.insert(MulUser);
+ MadeChange = true;
+ return;
+ }
+
+ // If this is a subtract instruction which is not already in negate form,
+ // see if we can convert it to X+-Y.
+ if (I->getOpcode() == Instruction::Sub) {
+ if (ShouldBreakUpSubtract(I)) {
+ Instruction *NI = BreakUpSubtract(I, RedoInsts);
+ RedoInsts.insert(I);
+ MadeChange = true;
+ I = NI;
+ } else if (match(I, m_Neg(m_Value()))) {
+ // Otherwise, this is a negation. See if the operand is a multiply tree
+ // and if this is not an inner node of a multiply tree.
+ if (isReassociableOp(I->getOperand(1), Instruction::Mul) &&
+ (!I->hasOneUse() ||
+ !isReassociableOp(I->user_back(), Instruction::Mul))) {
+ Instruction *NI = LowerNegateToMultiply(I);
+ // If the negate was simplified, revisit the users to see if we can
+ // reassociate further.
+ for (User *U : NI->users()) {
+ if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
+ RedoInsts.insert(Tmp);
+ }
+ RedoInsts.insert(I);
+ MadeChange = true;
+ I = NI;
+ }
+ }
+ } else if (I->getOpcode() == Instruction::FNeg ||
+ I->getOpcode() == Instruction::FSub) {
+ if (ShouldBreakUpSubtract(I)) {
+ Instruction *NI = BreakUpSubtract(I, RedoInsts);
+ RedoInsts.insert(I);
+ MadeChange = true;
+ I = NI;
+ } else if (match(I, m_FNeg(m_Value()))) {
+ // Otherwise, this is a negation. See if the operand is a multiply tree
+ // and if this is not an inner node of a multiply tree.
+ Value *Op = isa<BinaryOperator>(I) ? I->getOperand(1) :
+ I->getOperand(0);
+ if (isReassociableOp(Op, Instruction::FMul) &&
+ (!I->hasOneUse() ||
+ !isReassociableOp(I->user_back(), Instruction::FMul))) {
+ // If the negate was simplified, revisit the users to see if we can
+ // reassociate further.
+ Instruction *NI = LowerNegateToMultiply(I);
+ for (User *U : NI->users()) {
+ if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
+ RedoInsts.insert(Tmp);
+ }
+ RedoInsts.insert(I);
+ MadeChange = true;
+ I = NI;
+ }
+ }
+ }
+
+ // If this instruction is an associative binary operator, process it.
+ if (!I->isAssociative()) return;
+ BinaryOperator *BO = cast<BinaryOperator>(I);
+
+ // If this is an interior node of a reassociable tree, ignore it until we
+ // get to the root of the tree, to avoid N^2 analysis.
+ unsigned Opcode = BO->getOpcode();
+ if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode) {
+ // During the initial run we will get to the root of the tree.
+ // But if we get here while we are redoing instructions, there is no
+ // guarantee that the root will be visited. So Redo later
+ if (BO->user_back() != BO &&
+ BO->getParent() == BO->user_back()->getParent())
+ RedoInsts.insert(BO->user_back());
+ return;
+ }
+
+ // If this is an add tree that is used by a sub instruction, ignore it
+ // until we process the subtract.
+ if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
+ cast<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub)
+ return;
+ if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd &&
+ cast<Instruction>(BO->user_back())->getOpcode() == Instruction::FSub)
+ return;
+
+ ReassociateExpression(BO);
+}
+
+void ReassociatePass::ReassociateExpression(BinaryOperator *I) {
+ // First, walk the expression tree, linearizing the tree, collecting the
+ // operand information.
+ SmallVector<RepeatedValue, 8> Tree;
+ OverflowTracking Flags;
+ MadeChange |= LinearizeExprTree(I, Tree, RedoInsts, Flags);
+ SmallVector<ValueEntry, 8> Ops;
+ Ops.reserve(Tree.size());
+ for (const RepeatedValue &E : Tree)
+ Ops.append(E.second, ValueEntry(getRank(E.first), E.first));
+
+ LLVM_DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
+
+ // Now that we have linearized the tree to a list and have gathered all of
+ // the operands and their ranks, sort the operands by their rank. Use a
+ // stable_sort so that values with equal ranks will have their relative
+ // positions maintained (and so the compiler is deterministic). Note that
+ // this sorts so that the highest ranking values end up at the beginning of
+ // the vector.
+ llvm::stable_sort(Ops);
+
+ // Now that we have the expression tree in a convenient
+ // sorted form, optimize it globally if possible.
+ if (Value *V = OptimizeExpression(I, Ops)) {
+ if (V == I)
+ // Self-referential expression in unreachable code.
+ return;
+ // This expression tree simplified to something that isn't a tree,
+ // eliminate it.
+ LLVM_DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
+ I->replaceAllUsesWith(V);
+ if (Instruction *VI = dyn_cast<Instruction>(V))
+ if (I->getDebugLoc())
+ VI->setDebugLoc(I->getDebugLoc());
+ RedoInsts.insert(I);
+ ++NumAnnihil;
+ return;
+ }
+
+ // We want to sink immediates as deeply as possible except in the case where
+ // this is a multiply tree used only by an add, and the immediate is a -1.
+ // In this case we reassociate to put the negation on the outside so that we
+ // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
+ if (I->hasOneUse()) {
+ if (I->getOpcode() == Instruction::Mul &&
+ cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
+ isa<ConstantInt>(Ops.back().Op) &&
+ cast<ConstantInt>(Ops.back().Op)->isMinusOne()) {
+ ValueEntry Tmp = Ops.pop_back_val();
+ Ops.insert(Ops.begin(), Tmp);
+ } else if (I->getOpcode() == Instruction::FMul &&
+ cast<Instruction>(I->user_back())->getOpcode() ==
+ Instruction::FAdd &&
+ isa<ConstantFP>(Ops.back().Op) &&
+ cast<ConstantFP>(Ops.back().Op)->isExactlyValue(-1.0)) {
+ ValueEntry Tmp = Ops.pop_back_val();
+ Ops.insert(Ops.begin(), Tmp);
+ }
+ }
+
+ LLVM_DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
+
+ if (Ops.size() == 1) {
+ if (Ops[0].Op == I)
+ // Self-referential expression in unreachable code.
+ return;
+
+ // This expression tree simplified to something that isn't a tree,
+ // eliminate it.
+ I->replaceAllUsesWith(Ops[0].Op);
+ if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
+ OI->setDebugLoc(I->getDebugLoc());
+ RedoInsts.insert(I);
+ return;
+ }
+
+ if (Ops.size() > 2 && Ops.size() <= GlobalReassociateLimit) {
+ // Find the pair with the highest count in the pairmap and move it to the
+ // back of the list so that it can later be CSE'd.
+ // example:
+ // a*b*c*d*e
+ // if c*e is the most "popular" pair, we can express this as
+ // (((c*e)*d)*b)*a
+ unsigned Max = 1;
+ unsigned BestRank = 0;
+ std::pair<unsigned, unsigned> BestPair;
+ unsigned Idx = I->getOpcode() - Instruction::BinaryOpsBegin;
+ unsigned LimitIdx = 0;
+ // With the CSE-driven heuristic, we are about to slap two values at the
+ // beginning of the expression whereas they could live very late in the CFG.
+ // When using the CSE-local heuristic we avoid creating dependences from
+ // completely unrelated part of the CFG by limiting the expression
+ // reordering on the values that live in the first seen basic block.
+ // The main idea is that we want to avoid forming expressions that would
+ // become loop dependent.
+ if (UseCSELocalOpt) {
+ const BasicBlock *FirstSeenBB = nullptr;
+ int StartIdx = Ops.size() - 1;
+ // Skip the first value of the expression since we need at least two
+ // values to materialize an expression. I.e., even if this value is
+ // anchored in a different basic block, the actual first sub expression
+ // will be anchored on the second value.
+ for (int i = StartIdx - 1; i != -1; --i) {
+ const Value *Val = Ops[i].Op;
+ const auto *CurrLeafInstr = dyn_cast<Instruction>(Val);
+ const BasicBlock *SeenBB = nullptr;
+ if (!CurrLeafInstr) {
+ // The value is free of any CFG dependencies.
+ // Do as if it lives in the entry block.
+ //
+ // We do this to make sure all the values falling on this path are
+ // seen through the same anchor point. The rationale is these values
+ // can be combined together to from a sub expression free of any CFG
+ // dependencies so we want them to stay together.
+ // We could be cleverer and postpone the anchor down to the first
+ // anchored value, but that's likely complicated to get right.
+ // E.g., we wouldn't want to do that if that means being stuck in a
+ // loop.
+ //
+ // For instance, we wouldn't want to change:
+ // res = arg1 op arg2 op arg3 op ... op loop_val1 op loop_val2 ...
+ // into
+ // res = loop_val1 op arg1 op arg2 op arg3 op ... op loop_val2 ...
+ // Because all the sub expressions with arg2..N would be stuck between
+ // two loop dependent values.
+ SeenBB = &I->getParent()->getParent()->getEntryBlock();
+ } else {
+ SeenBB = CurrLeafInstr->getParent();
+ }
+
+ if (!FirstSeenBB) {
+ FirstSeenBB = SeenBB;
+ continue;
+ }
+ if (FirstSeenBB != SeenBB) {
+ // ith value is in a different basic block.
+ // Rewind the index once to point to the last value on the same basic
+ // block.
+ LimitIdx = i + 1;
+ LLVM_DEBUG(dbgs() << "CSE reordering: Consider values between ["
+ << LimitIdx << ", " << StartIdx << "]\n");
+ break;
+ }
+ }
+ }
+ for (unsigned i = Ops.size() - 1; i > LimitIdx; --i) {
+ // We must use int type to go below zero when LimitIdx is 0.
+ for (int j = i - 1; j >= (int)LimitIdx; --j) {
+ unsigned Score = 0;
+ Value *Op0 = Ops[i].Op;
+ Value *Op1 = Ops[j].Op;
+ if (std::less<Value *>()(Op1, Op0))
+ std::swap(Op0, Op1);
+ auto it = PairMap[Idx].find({Op0, Op1});
+ if (it != PairMap[Idx].end()) {
+ // Functions like BreakUpSubtract() can erase the Values we're using
+ // as keys and create new Values after we built the PairMap. There's a
+ // small chance that the new nodes can have the same address as
+ // something already in the table. We shouldn't accumulate the stored
+ // score in that case as it refers to the wrong Value.
+ if (it->second.isValid())
+ Score += it->second.Score;
+ }
+
+ unsigned MaxRank = std::max(Ops[i].Rank, Ops[j].Rank);
+
+ // By construction, the operands are sorted in reverse order of their
+ // topological order.
+ // So we tend to form (sub) expressions with values that are close to
+ // each other.
+ //
+ // Now to expose more CSE opportunities we want to expose the pair of
+ // operands that occur the most (as statically computed in
+ // BuildPairMap.) as the first sub-expression.
+ //
+ // If two pairs occur as many times, we pick the one with the
+ // lowest rank, meaning the one with both operands appearing first in
+ // the topological order.
+ if (Score > Max || (Score == Max && MaxRank < BestRank)) {
+ BestPair = {j, i};
+ Max = Score;
+ BestRank = MaxRank;
+ }
+ }
+ }
+ if (Max > 1) {
+ auto Op0 = Ops[BestPair.first];
+ auto Op1 = Ops[BestPair.second];
+ Ops.erase(&Ops[BestPair.second]);
+ Ops.erase(&Ops[BestPair.first]);
+ Ops.push_back(Op0);
+ Ops.push_back(Op1);
+ }
+ }
+ LLVM_DEBUG(dbgs() << "RAOut after CSE reorder:\t"; PrintOps(I, Ops);
+ dbgs() << '\n');
+ // Now that we ordered and optimized the expressions, splat them back into
+ // the expression tree, removing any unneeded nodes.
+ RewriteExprTree(I, Ops, Flags);
+}
+
+void
+ReassociatePass::BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT) {
+ // Make a "pairmap" of how often each operand pair occurs.
+ for (BasicBlock *BI : RPOT) {
+ for (Instruction &I : *BI) {
+ if (!I.isAssociative() || !I.isBinaryOp())
+ continue;
+
+ // Ignore nodes that aren't at the root of trees.
+ if (I.hasOneUse() && I.user_back()->getOpcode() == I.getOpcode())
+ continue;
+
+ // Collect all operands in a single reassociable expression.
+ // Since Reassociate has already been run once, we can assume things
+ // are already canonical according to Reassociation's regime.
+ SmallVector<Value *, 8> Worklist = { I.getOperand(0), I.getOperand(1) };
+ SmallVector<Value *, 8> Ops;
+ while (!Worklist.empty() && Ops.size() <= GlobalReassociateLimit) {
+ Value *Op = Worklist.pop_back_val();
+ Instruction *OpI = dyn_cast<Instruction>(Op);
+ if (!OpI || OpI->getOpcode() != I.getOpcode() || !OpI->hasOneUse()) {
+ Ops.push_back(Op);
+ continue;
+ }
+ // Be paranoid about self-referencing expressions in unreachable code.
+ if (OpI->getOperand(0) != OpI)
+ Worklist.push_back(OpI->getOperand(0));
+ if (OpI->getOperand(1) != OpI)
+ Worklist.push_back(OpI->getOperand(1));
+ }
+ // Skip extremely long expressions.
+ if (Ops.size() > GlobalReassociateLimit)
+ continue;
+
+ // Add all pairwise combinations of operands to the pair map.
+ unsigned BinaryIdx = I.getOpcode() - Instruction::BinaryOpsBegin;
+ SmallSet<std::pair<Value *, Value*>, 32> Visited;
+ for (unsigned i = 0; i < Ops.size() - 1; ++i) {
+ for (unsigned j = i + 1; j < Ops.size(); ++j) {
+ // Canonicalize operand orderings.
+ Value *Op0 = Ops[i];
+ Value *Op1 = Ops[j];
+ if (std::less<Value *>()(Op1, Op0))
+ std::swap(Op0, Op1);
+ if (!Visited.insert({Op0, Op1}).second)
+ continue;
+ auto res = PairMap[BinaryIdx].insert({{Op0, Op1}, {Op0, Op1, 1}});
+ if (!res.second) {
+ // If either key value has been erased then we've got the same
+ // address by coincidence. That can't happen here because nothing is
+ // erasing values but it can happen by the time we're querying the
+ // map.
+ assert(res.first->second.isValid() && "WeakVH invalidated");
+ ++res.first->second.Score;
+ }
+ }
+ }
+ }
+ }
+}
+
+PreservedAnalyses ReassociatePass::run(Function &F, FunctionAnalysisManager &) {
+ // Get the functions basic blocks in Reverse Post Order. This order is used by
+ // BuildRankMap to pre calculate ranks correctly. It also excludes dead basic
+ // blocks (it has been seen that the analysis in this pass could hang when
+ // analysing dead basic blocks).
+ ReversePostOrderTraversal<Function *> RPOT(&F);
+
+ // Calculate the rank map for F.
+ BuildRankMap(F, RPOT);
+
+ // Build the pair map before running reassociate.
+ // Technically this would be more accurate if we did it after one round
+ // of reassociation, but in practice it doesn't seem to help much on
+ // real-world code, so don't waste the compile time running reassociate
+ // twice.
+ // If a user wants, they could expicitly run reassociate twice in their
+ // pass pipeline for further potential gains.
+ // It might also be possible to update the pair map during runtime, but the
+ // overhead of that may be large if there's many reassociable chains.
+ BuildPairMap(RPOT);
+
+ MadeChange = false;
+
+ // Traverse the same blocks that were analysed by BuildRankMap.
+ for (BasicBlock *BI : RPOT) {
+ assert(RankMap.count(&*BI) && "BB should be ranked.");
+ // Optimize every instruction in the basic block.
+ for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;)
+ if (isInstructionTriviallyDead(&*II)) {
+ EraseInst(&*II++);
+ } else {
+ OptimizeInst(&*II);
+ assert(II->getParent() == &*BI && "Moved to a different block!");
+ ++II;
+ }
+
+ // Make a copy of all the instructions to be redone so we can remove dead
+ // instructions.
+ OrderedSet ToRedo(RedoInsts);
+ // Iterate over all instructions to be reevaluated and remove trivially dead
+ // instructions. If any operand of the trivially dead instruction becomes
+ // dead mark it for deletion as well. Continue this process until all
+ // trivially dead instructions have been removed.
+ while (!ToRedo.empty()) {
+ Instruction *I = ToRedo.pop_back_val();
+ if (isInstructionTriviallyDead(I)) {
+ RecursivelyEraseDeadInsts(I, ToRedo);
+ MadeChange = true;
+ }
+ }
+
+ // Now that we have removed dead instructions, we can reoptimize the
+ // remaining instructions.
+ while (!RedoInsts.empty()) {
+ Instruction *I = RedoInsts.front();
+ RedoInsts.erase(RedoInsts.begin());
+ if (isInstructionTriviallyDead(I))
+ EraseInst(I);
+ else
+ OptimizeInst(I);
+ }
+ }
+
+ // We are done with the rank map and pair map.
+ RankMap.clear();
+ ValueRankMap.clear();
+ for (auto &Entry : PairMap)
+ Entry.clear();
+
+ if (MadeChange) {
+ PreservedAnalyses PA;
+ PA.preserveSet<CFGAnalyses>();
+ return PA;
+ }
+
+ return PreservedAnalyses::all();
+}
+
+namespace {
+
+class ReassociateLegacyPass : public FunctionPass {
+ ReassociatePass Impl;
+
+public:
+ static char ID; // Pass identification, replacement for typeid
+
+ ReassociateLegacyPass() : FunctionPass(ID) {
+ initializeReassociateLegacyPassPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool runOnFunction(Function &F) override {
+ if (skipFunction(F))
+ return false;
+
+ FunctionAnalysisManager DummyFAM;
+ auto PA = Impl.run(F, DummyFAM);
+ return !PA.areAllPreserved();
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.setPreservesCFG();
+ AU.addPreserved<AAResultsWrapperPass>();
+ AU.addPreserved<BasicAAWrapperPass>();
+ AU.addPreserved<GlobalsAAWrapperPass>();
+ }
+};
+
+} // end anonymous namespace
+
+char ReassociateLegacyPass::ID = 0;
+
+INITIALIZE_PASS(ReassociateLegacyPass, "reassociate",
+ "Reassociate expressions", false, false)
+
+// Public interface to the Reassociate pass
+FunctionPass *llvm::createReassociatePass() {
+ return new ReassociateLegacyPass();
+}
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