[llvm] [InstCombine] Missed optimization for select a%2==0, (a/2*2)*(a/2*2), 0 (PR #92658)
Jorge Botto via llvm-commits
llvm-commits at lists.llvm.org
Sat Jun 15 02:09:07 PDT 2024
https://github.com/jf-botto updated https://github.com/llvm/llvm-project/pull/92658
>From 195e0fa744b57474b9220c79deee0fb2eb79159f Mon Sep 17 00:00:00 2001
From: Jorge Botto <jorge.botto.16 at ucl.ac.uk>
Date: Fri, 14 Jun 2024 23:20:18 +0100
Subject: [PATCH 1/2] precommit test
---
llvm/test/Transforms/InstCombine/select.ll | 125 +++++++++++++++++++++
1 file changed, 125 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index b37e9175b26a5..5addea127ee51 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -1456,6 +1456,131 @@ define <2 x i32> @select_icmp_slt0_xor_vec(<2 x i32> %x) {
ret <2 x i32> %x.xor
}
+define i8 @select_icmp_eq_mul_and(i8 noundef %a, i8 %b) {
+; CHECK-LABEL: @select_icmp_eq_mul_and(
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
+; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
+; CHECK-NEXT: [[MUL:%.*]] = mul i8 [[DIV7]], [[DIV7]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[B:%.*]]
+; CHECK-NEXT: ret i8 [[RETVAL_0]]
+;
+ %1 = and i8 %a, 1
+ %cmp = icmp eq i8 %1, 0
+ %div7 = and i8 %a, -2
+ %mul = mul i8 %div7, %div7
+ %retval.0 = select i1 %cmp, i8 %mul, i8 %b
+ ret i8 %retval.0
+}
+
+define i8 @select_icmp_eq_shl_and(i8 noundef %a, i8 %b) {
+; CHECK-LABEL: @select_icmp_eq_shl_and(
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
+; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
+; CHECK-NEXT: [[SHL:%.*]] = shl i8 [[DIV7]], [[DIV7]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[SHL]], i8 [[B:%.*]]
+; CHECK-NEXT: ret i8 [[RETVAL_0]]
+;
+ %1 = and i8 %a, 1
+ %cmp = icmp eq i8 %1, 0
+ %div7 = and i8 %a, -2
+ %shl = shl i8 %div7, %div7
+ %retval.0 = select i1 %cmp, i8 %shl, i8 %b
+ ret i8 %retval.0
+}
+
+define i8 @select_icmp_eq_and(i8 noundef %a, i8 %b) {
+; CHECK-LABEL: @select_icmp_eq_and(
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
+; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[DIV7]], i8 [[B:%.*]]
+; CHECK-NEXT: ret i8 [[RETVAL_0]]
+;
+ %1 = and i8 %a, 1
+ %cmp = icmp eq i8 %1, 0
+ %div7 = and i8 %a, -2
+ %retval.0 = select i1 %cmp, i8 %div7, i8 %b
+ ret i8 %retval.0
+}
+
+;negative test
+define i8 @select_icmp_eq_mul_and_undef(i8 %a, i8 %b) {
+; CHECK-LABEL: @select_icmp_eq_mul_and_undef(
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
+; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
+; CHECK-NEXT: [[MUL:%.*]] = mul i8 [[DIV7]], [[DIV7]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[B:%.*]]
+; CHECK-NEXT: ret i8 [[RETVAL_0]]
+;
+ %1 = and i8 %a, 1
+ %cmp = icmp eq i8 %1, 0
+ %div7 = and i8 %a, -2
+ %mul = mul i8 %div7, %div7
+ %retval.0 = select i1 %cmp, i8 %mul, i8 %b
+ ret i8 %retval.0
+}
+
+;negative test
+define i8 @select_icmp_eq_and_undef(i8 %a, i8 %b) {
+; CHECK-LABEL: @select_icmp_eq_and_undef(
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
+; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[DIV7]], i8 [[B:%.*]]
+; CHECK-NEXT: ret i8 [[RETVAL_0]]
+;
+ %1 = and i8 %a, 1
+ %cmp = icmp eq i8 %1, 0
+ %div7 = and i8 %a, -2
+ %retval.0 = select i1 %cmp, i8 %div7, i8 %b
+ ret i8 %retval.0
+}
+
+;negative test
+define i8 @select_and(i8 noundef %a, i8 %b, i1 %cmp) {
+; CHECK-LABEL: @select_and(
+; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A:%.*]], -2
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP:%.*]], i8 [[DIV7]], i8 [[B:%.*]]
+; CHECK-NEXT: ret i8 [[RETVAL_0]]
+;
+ %div7 = and i8 %a, -2
+ %retval.0 = select i1 %cmp, i8 %div7, i8 %b
+ ret i8 %retval.0
+}
+
+;negative test
+define i8 @select_mul_and(i8 noundef %a, i8 %b, i1 %cmp) {
+; CHECK-LABEL: @select_mul_and(
+; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A:%.*]], -2
+; CHECK-NEXT: [[MUL:%.*]] = mul i8 [[DIV7]], [[DIV7]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP:%.*]], i8 [[MUL]], i8 [[B:%.*]]
+; CHECK-NEXT: ret i8 [[RETVAL_0]]
+;
+ %div7 = and i8 %a, -2
+ %mul = mul i8 %div7, %div7
+ %retval.0 = select i1 %cmp, i8 %mul, i8 %b
+ ret i8 %retval.0
+}
+
+;negative test
+define i8 @select_icmp_eq_and_diff(i8 noundef %a, i8 %b, i8 %c) {
+; CHECK-LABEL: @select_icmp_eq_and_diff(
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
+; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[C:%.*]], -2
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[DIV7]], i8 [[B:%.*]]
+; CHECK-NEXT: ret i8 [[RETVAL_0]]
+;
+ %1 = and i8 %a, 1
+ %cmp = icmp eq i8 %1, 0
+ %div7 = and i8 %c, -2
+ %retval.0 = select i1 %cmp, i8 %div7, i8 %b
+ ret i8 %retval.0
+}
+
define <4 x i32> @canonicalize_to_shuffle(<4 x i32> %a, <4 x i32> %b) {
; CHECK-LABEL: @canonicalize_to_shuffle(
; CHECK-NEXT: [[SEL:%.*]] = shufflevector <4 x i32> [[A:%.*]], <4 x i32> [[B:%.*]], <4 x i32> <i32 0, i32 5, i32 6, i32 3>
>From e210641aebfc14f738bc0a56493b9db2e5d728d7 Mon Sep 17 00:00:00 2001
From: Jorge Botto <jorge.botto.16 at ucl.ac.uk>
Date: Fri, 14 Jun 2024 23:54:32 +0100
Subject: [PATCH 2/2] Adding the missed optimisation
---
llvm/include/llvm/Analysis/ValueTracking.h | 4 ++
.../Transforms/InstCombine/InstCombiner.h | 7 ++
llvm/lib/Analysis/ValueTracking.cpp | 6 +-
.../InstCombine/InstCombineSelect.cpp | 71 ++++++++++++++++---
llvm/test/Transforms/InstCombine/select.ll | 21 +++---
5 files changed, 82 insertions(+), 27 deletions(-)
diff --git a/llvm/include/llvm/Analysis/ValueTracking.h b/llvm/include/llvm/Analysis/ValueTracking.h
index e577d0cc7ad41..57fa4f29d5eff 100644
--- a/llvm/include/llvm/Analysis/ValueTracking.h
+++ b/llvm/include/llvm/Analysis/ValueTracking.h
@@ -94,6 +94,10 @@ void computeKnownBitsFromRangeMetadata(const MDNode &Ranges, KnownBits &Known);
void computeKnownBitsFromContext(const Value *V, KnownBits &Known,
unsigned Depth, const SimplifyQuery &Q);
+void computeKnownBitsFromCond(const Value *V, Value *Cond, KnownBits &Known,
+ unsigned Depth, const SimplifyQuery &SQ,
+ bool Invert);
+
/// Using KnownBits LHS/RHS produce the known bits for logic op (and/xor/or).
KnownBits analyzeKnownBitsFromAndXorOr(const Operator *I,
const KnownBits &KnownLHS,
diff --git a/llvm/include/llvm/Transforms/InstCombine/InstCombiner.h b/llvm/include/llvm/Transforms/InstCombine/InstCombiner.h
index 855d1aeddfaee..f81150b7b31f6 100644
--- a/llvm/include/llvm/Transforms/InstCombine/InstCombiner.h
+++ b/llvm/include/llvm/Transforms/InstCombine/InstCombiner.h
@@ -438,6 +438,13 @@ class LLVM_LIBRARY_VISIBILITY InstCombiner {
return llvm::computeKnownBits(V, Depth, SQ.getWithInstruction(CxtI));
}
+ void computeKnownBitsFromCond(const Value *V, ICmpInst *Cmp, KnownBits &Known,
+ unsigned Depth, const Instruction *CxtI,
+ bool Invert) const {
+ llvm::computeKnownBitsFromCond(V, Cmp, Known, Depth,
+ SQ.getWithInstruction(CxtI), Invert);
+ }
+
bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero = false,
unsigned Depth = 0,
const Instruction *CxtI = nullptr) {
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 8126d2a1acc27..085e4a81d17ee 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -747,9 +747,9 @@ static void computeKnownBitsFromICmpCond(const Value *V, ICmpInst *Cmp,
computeKnownBitsFromCmp(V, Pred, LHS, RHS, Known, SQ);
}
-static void computeKnownBitsFromCond(const Value *V, Value *Cond,
- KnownBits &Known, unsigned Depth,
- const SimplifyQuery &SQ, bool Invert) {
+void llvm::computeKnownBitsFromCond(const Value *V, Value *Cond,
+ KnownBits &Known, unsigned Depth,
+ const SimplifyQuery &SQ, bool Invert) {
Value *A, *B;
if (Depth < MaxAnalysisRecursionDepth &&
match(Cond, m_LogicalOp(m_Value(A), m_Value(B)))) {
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 7d26807544d7e..d6f6cebec50ae 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -1073,6 +1073,50 @@ static Value *foldAbsDiff(ICmpInst *Cmp, Value *TVal, Value *FVal,
return nullptr;
}
+// When the lsb of cond is 0:
+// cond ? A & -2 : B --> cond ? A : B
+// cond ? BinOp (A & -2), (A & -2) : B --> cond ? BinOp A, A : B
+static Value *foldSelectWithIcmpEqAndPattern(ICmpInst *Cmp, Value *TVal,
+ Value *FVal,
+ InstCombiner::BuilderTy &Builder,
+ SelectInst &SI,
+ InstCombinerImpl &IC) {
+
+ Value *A;
+ ConstantInt *MaskedConstant;
+
+ // Checks if true branche matches the pattern 'A % 2'.
+ if (match(TVal,
+ m_OneUse(m_c_And(m_Value(A), m_ConstantInt(MaskedConstant)))) &&
+ MaskedConstant->getValue().getSExtValue() == -2) {
+ KnownBits Known;
+ Known = IC.computeKnownBits(A, 0, &SI);
+ IC.computeKnownBitsFromCond(A, Cmp, Known, 0, &SI, false);
+ if (Known.Zero[0])
+ return Builder.CreateSelect(Cmp, A, FVal);
+ else
+ return nullptr;
+ }
+
+ // Checks if true branch matches nested 'A % 2' within a binary operation.
+ Value *MulVal;
+ if (match(TVal, m_OneUse(m_BinOp(m_Value(MulVal), m_Deferred(MulVal)))))
+ if (match(MulVal, m_c_And(m_Value(A), m_ConstantInt(MaskedConstant))) &&
+ MaskedConstant->getValue().getSExtValue() == -2) {
+ KnownBits Known;
+ Known = IC.computeKnownBits(A, 0, &SI);
+ IC.computeKnownBitsFromCond(A, Cmp, Known, 0, &SI, false);
+ if (Known.Zero[0]) {
+ Instruction::BinaryOps OpCode = cast<BinaryOperator>(TVal)->getOpcode();
+ Value *NewTValue = Builder.CreateBinOp(OpCode, A, A);
+ return Builder.CreateSelect(Cmp, NewTValue, FVal);
+ } else
+ return nullptr;
+ }
+
+ return nullptr;
+}
+
/// Fold the following code sequence:
/// \code
/// int a = ctlz(x & -x);
@@ -1812,6 +1856,7 @@ static Instruction *foldSelectICmpEq(SelectInst &SI, ICmpInst *ICI,
/// Visit a SelectInst that has an ICmpInst as its first operand.
Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI,
ICmpInst *ICI) {
+
if (Instruction *NewSel = foldSelectValueEquivalence(SI, *ICI))
return NewSel;
@@ -1951,6 +1996,10 @@ Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI,
if (Value *V = foldAbsDiff(ICI, TrueVal, FalseVal, Builder))
return replaceInstUsesWith(SI, V);
+ if (Value *V = foldSelectWithIcmpEqAndPattern(ICI, TrueVal, FalseVal, Builder,
+ SI, *this))
+ return replaceInstUsesWith(SI, V);
+
return Changed ? &SI : nullptr;
}
@@ -2359,20 +2408,20 @@ static Instruction *foldSelectCmpBitcasts(SelectInst &Sel,
/// operand, the result of the select will always be equal to its false value.
/// For example:
///
-/// %cmpxchg = cmpxchg ptr %ptr, i64 %compare, i64 %new_value seq_cst seq_cst
-/// %val = extractvalue { i64, i1 } %cmpxchg, 0
-/// %success = extractvalue { i64, i1 } %cmpxchg, 1
-/// %sel = select i1 %success, i64 %compare, i64 %val
-/// ret i64 %sel
+/// %0 = cmpxchg i64* %ptr, i64 %compare, i64 %new_value seq_cst seq_cst
+/// %1 = extractvalue { i64, i1 } %0, 1
+/// %2 = extractvalue { i64, i1 } %0, 0
+/// %3 = select i1 %1, i64 %compare, i64 %2
+/// ret i64 %3
///
-/// The returned value of the cmpxchg instruction (%val) is the original value
-/// located at %ptr prior to any update. If the cmpxchg operation succeeds, %val
+/// The returned value of the cmpxchg instruction (%2) is the original value
+/// located at %ptr prior to any update. If the cmpxchg operation succeeds, %2
/// must have been equal to %compare. Thus, the result of the select is always
-/// equal to %val, and the code can be simplified to:
+/// equal to %2, and the code can be simplified to:
///
-/// %cmpxchg = cmpxchg ptr %ptr, i64 %compare, i64 %new_value seq_cst seq_cst
-/// %val = extractvalue { i64, i1 } %cmpxchg, 0
-/// ret i64 %val
+/// %0 = cmpxchg i64* %ptr, i64 %compare, i64 %new_value seq_cst seq_cst
+/// %1 = extractvalue { i64, i1 } %0, 0
+/// ret i64 %1
///
static Value *foldSelectCmpXchg(SelectInst &SI) {
// A helper that determines if V is an extractvalue instruction whose
diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index 5addea127ee51..637e9d25a3d41 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -1460,9 +1460,8 @@ define i8 @select_icmp_eq_mul_and(i8 noundef %a, i8 %b) {
; CHECK-LABEL: @select_icmp_eq_mul_and(
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
-; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
-; CHECK-NEXT: [[MUL:%.*]] = mul i8 [[DIV7]], [[DIV7]]
-; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[B:%.*]]
+; CHECK-NEXT: [[TMP2:%.*]] = mul i8 [[A]], [[A]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[TMP2]], i8 [[B:%.*]]
; CHECK-NEXT: ret i8 [[RETVAL_0]]
;
%1 = and i8 %a, 1
@@ -1477,9 +1476,8 @@ define i8 @select_icmp_eq_shl_and(i8 noundef %a, i8 %b) {
; CHECK-LABEL: @select_icmp_eq_shl_and(
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
-; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
-; CHECK-NEXT: [[SHL:%.*]] = shl i8 [[DIV7]], [[DIV7]]
-; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[SHL]], i8 [[B:%.*]]
+; CHECK-NEXT: [[TMP2:%.*]] = shl i8 [[A]], [[A]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[TMP2]], i8 [[B:%.*]]
; CHECK-NEXT: ret i8 [[RETVAL_0]]
;
%1 = and i8 %a, 1
@@ -1494,8 +1492,7 @@ define i8 @select_icmp_eq_and(i8 noundef %a, i8 %b) {
; CHECK-LABEL: @select_icmp_eq_and(
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
-; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
-; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[DIV7]], i8 [[B:%.*]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[A]], i8 [[B:%.*]]
; CHECK-NEXT: ret i8 [[RETVAL_0]]
;
%1 = and i8 %a, 1
@@ -1510,9 +1507,8 @@ define i8 @select_icmp_eq_mul_and_undef(i8 %a, i8 %b) {
; CHECK-LABEL: @select_icmp_eq_mul_and_undef(
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
-; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
-; CHECK-NEXT: [[MUL:%.*]] = mul i8 [[DIV7]], [[DIV7]]
-; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[MUL]], i8 [[B:%.*]]
+; CHECK-NEXT: [[TMP2:%.*]] = mul i8 [[A]], [[A]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[TMP2]], i8 [[B:%.*]]
; CHECK-NEXT: ret i8 [[RETVAL_0]]
;
%1 = and i8 %a, 1
@@ -1528,8 +1524,7 @@ define i8 @select_icmp_eq_and_undef(i8 %a, i8 %b) {
; CHECK-LABEL: @select_icmp_eq_and_undef(
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[A:%.*]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[TMP1]], 0
-; CHECK-NEXT: [[DIV7:%.*]] = and i8 [[A]], -2
-; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[DIV7]], i8 [[B:%.*]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i8 [[A]], i8 [[B:%.*]]
; CHECK-NEXT: ret i8 [[RETVAL_0]]
;
%1 = and i8 %a, 1
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