[llvm] 6c25c58 - [ConstraintElim] Track and simplify conditions at use.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 27 09:28:05 PDT 2023
Author: Florian Hahn
Date: 2023-06-27T17:27:49+01:00
New Revision: 6c25c58a4d7caa0337d36bb8c41546f2002130d1
URL: https://github.com/llvm/llvm-project/commit/6c25c58a4d7caa0337d36bb8c41546f2002130d1
DIFF: https://github.com/llvm/llvm-project/commit/6c25c58a4d7caa0337d36bb8c41546f2002130d1.diff
LOG: [ConstraintElim] Track and simplify conditions at use.
This patch updates ConstraintElimination to track uses of conditions in
the worklist. This allows simplifying conditions using the context that
holds directly at the condition, instead of where the condition is
defined.
This allows us to catch more cases in practice: there are multiple
code-size changes for CTMark while compile-time remains unchanged:
https://llvm-compile-time-tracker.com/compare.php?from=4b020cca9363bebab4643f89cfa92ab2fcc7976c&to=7a6e84b8f029713c137814cd46eec775d24a54a1&stat=instructions:u
This should help to simplify D151799.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D153660
Added:
Modified:
llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
llvm/test/Transforms/ConstraintElimination/assumes.ll
llvm/test/Transforms/ConstraintElimination/cond-used-in-phi.ll
llvm/test/Transforms/ConstraintElimination/monotonic-pointer-phis-crashes.ll
llvm/test/Transforms/ConstraintElimination/uses-in-different-blocks.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index 1b2e6aa7639dc..8ccfae4757e8f 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -660,41 +660,68 @@ void ConstraintInfo::transferToOtherSystem(
}
}
+static Instruction *getContextInstForUse(Use &U) {
+ Instruction *UserI = cast<Instruction>(U.getUser());
+ if (auto *Phi = dyn_cast<PHINode>(UserI))
+ UserI = Phi->getIncomingBlock(U)->getTerminator();
+ return UserI;
+}
+
namespace {
/// Represents either
/// * a condition that holds on entry to a block (=conditional fact)
/// * an assume (=assume fact)
-/// * an instruction to simplify.
+/// * a use of a compare instruction to simplify.
/// It also tracks the Dominator DFS in and out numbers for each entry.
struct FactOrCheck {
- Instruction *Inst;
+ union {
+ Instruction *Inst;
+ Use *U;
+ };
unsigned NumIn;
unsigned NumOut;
- bool IsCheck;
+ bool HasInst;
bool Not;
- FactOrCheck(DomTreeNode *DTN, Instruction *Inst, bool IsCheck, bool Not)
+ FactOrCheck(DomTreeNode *DTN, Instruction *Inst, bool Not)
: Inst(Inst), NumIn(DTN->getDFSNumIn()), NumOut(DTN->getDFSNumOut()),
- IsCheck(IsCheck), Not(Not) {}
+ HasInst(true), Not(Not) {}
+
+ FactOrCheck(DomTreeNode *DTN, Use *U)
+ : U(U), NumIn(DTN->getDFSNumIn()), NumOut(DTN->getDFSNumOut()),
+ HasInst(false), Not(false) {}
static FactOrCheck getFact(DomTreeNode *DTN, Instruction *Inst,
bool Not = false) {
- return FactOrCheck(DTN, Inst, false, Not);
+ return FactOrCheck(DTN, Inst, Not);
}
- static FactOrCheck getCheck(DomTreeNode *DTN, Instruction *Inst) {
- return FactOrCheck(DTN, Inst, true, false);
+ static FactOrCheck getCheck(DomTreeNode *DTN, Use *U) {
+ return FactOrCheck(DTN, U);
}
- bool isAssumeFact() const {
- if (!IsCheck && isa<IntrinsicInst>(Inst)) {
- assert(match(Inst, m_Intrinsic<Intrinsic::assume>()));
- return true;
- }
- return false;
+ static FactOrCheck getCheck(DomTreeNode *DTN, CallInst *CI) {
+ return FactOrCheck(DTN, CI, false);
}
- bool isConditionFact() const { return !IsCheck && isa<CmpInst>(Inst); }
+ bool isCheck() const {
+ return !HasInst ||
+ match(Inst, m_Intrinsic<Intrinsic::ssub_with_overflow>());
+ }
+
+ Instruction *getContextInst() const {
+ if (HasInst)
+ return Inst;
+ return getContextInstForUse(*U);
+ }
+ Instruction *getInstructionToSimplify() const {
+ assert(isCheck());
+ if (HasInst)
+ return Inst;
+ // The use may have been simplified to a constant already.
+ return dyn_cast<Instruction>(*U);
+ }
+ bool isConditionFact() const { return !isCheck() && isa<CmpInst>(Inst); }
};
/// Keep state required to build worklist.
@@ -732,12 +759,19 @@ void State::addInfoFor(BasicBlock &BB) {
// Queue conditions and assumes.
for (Instruction &I : BB) {
if (auto Cmp = dyn_cast<ICmpInst>(&I)) {
- WorkList.push_back(FactOrCheck::getCheck(DT.getNode(&BB), Cmp));
+ for (Use &U : Cmp->uses()) {
+ auto *UserI = getContextInstForUse(U);
+ auto *DTN = DT.getNode(UserI->getParent());
+ if (!DTN)
+ continue;
+ WorkList.push_back(FactOrCheck::getCheck(DTN, &U));
+ }
continue;
}
if (match(&I, m_Intrinsic<Intrinsic::ssub_with_overflow>())) {
- WorkList.push_back(FactOrCheck::getCheck(DT.getNode(&BB), &I));
+ WorkList.push_back(
+ FactOrCheck::getCheck(DT.getNode(&BB), cast<CallInst>(&I)));
continue;
}
@@ -973,7 +1007,8 @@ static void generateReproducer(CmpInst *Cond, Module *M,
}
static bool checkAndReplaceCondition(
- CmpInst *Cmp, ConstraintInfo &Info, Module *ReproducerModule,
+ CmpInst *Cmp, ConstraintInfo &Info, unsigned NumIn, unsigned NumOut,
+ Instruction *ContextInst, Module *ReproducerModule,
ArrayRef<ReproducerEntry> ReproducerCondStack, DominatorTree &DT) {
LLVM_DEBUG(dbgs() << "Checking " << *Cmp << "\n");
@@ -1018,7 +1053,16 @@ static bool checkAndReplaceCondition(
generateReproducer(Cmp, ReproducerModule, ReproducerCondStack, Info, DT);
Constant *ConstantC = ConstantInt::getBool(
CmpInst::makeCmpResultType(Cmp->getType()), IsTrue);
- Cmp->replaceUsesWithIf(ConstantC, [](Use &U) {
+ Cmp->replaceUsesWithIf(ConstantC, [&DT, NumIn, NumOut,
+ ContextInst](Use &U) {
+ auto *UserI = getContextInstForUse(U);
+ auto *DTN = DT.getNode(UserI->getParent());
+ if (!DTN || DTN->getDFSNumIn() < NumIn || DTN->getDFSNumOut() > NumOut)
+ return false;
+ if (UserI->getParent() == ContextInst->getParent() &&
+ UserI->comesBefore(ContextInst))
+ return false;
+
// Conditions in an assume trivially simplify to true. Skip uses
// in assume calls to not destroy the available information.
auto *II = dyn_cast<IntrinsicInst>(U.getUser());
@@ -1206,7 +1250,9 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT,
return true;
if (B.isConditionFact())
return false;
- return A.Inst->comesBefore(B.Inst);
+ auto *InstA = A.getContextInst();
+ auto *InstB = B.getContextInst();
+ return InstA->comesBefore(InstB);
}
return A.NumIn < B.NumIn;
});
@@ -1237,27 +1283,26 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT,
DFSInStack);
}
- LLVM_DEBUG({
- dbgs() << "Processing ";
- if (CB.IsCheck)
- dbgs() << "condition to simplify: " << *CB.Inst;
- else
- dbgs() << "fact to add to the system: " << *CB.Inst;
- dbgs() << "\n";
- });
+ LLVM_DEBUG(dbgs() << "Processing ");
// For a block, check if any CmpInsts become known based on the current set
// of constraints.
- if (CB.IsCheck) {
- if (auto *II = dyn_cast<WithOverflowInst>(CB.Inst)) {
+ if (CB.isCheck()) {
+ Instruction *Inst = CB.getInstructionToSimplify();
+ if (!Inst)
+ continue;
+ LLVM_DEBUG(dbgs() << "condition to simplify: " << *Inst << "\n");
+ if (auto *II = dyn_cast<WithOverflowInst>(Inst)) {
Changed |= tryToSimplifyOverflowMath(II, Info, ToRemove);
- } else if (auto *Cmp = dyn_cast<ICmpInst>(CB.Inst)) {
- Changed |= checkAndReplaceCondition(Cmp, Info, ReproducerModule.get(),
- ReproducerCondStack, S.DT);
+ } else if (auto *Cmp = dyn_cast<ICmpInst>(Inst)) {
+ Changed |= checkAndReplaceCondition(
+ Cmp, Info, CB.NumIn, CB.NumOut, CB.getContextInst(),
+ ReproducerModule.get(), ReproducerCondStack, S.DT);
}
continue;
}
+ LLVM_DEBUG(dbgs() << "fact to add to the system: " << *CB.Inst << "\n");
ICmpInst::Predicate Pred;
Value *A, *B;
Value *Cmp = CB.Inst;
diff --git a/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll b/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
index 2f0152015e235..ab1ce772d88be 100644
--- a/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
+++ b/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
@@ -203,7 +203,7 @@ define i1 @and_select_not_used_for_branch(i32 %x, i32 %y,i32 %z) {
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[EXIT:%.*]]
; CHECK: then:
; CHECK-NEXT: [[C_4:%.*]] = icmp eq i32 [[Z:%.*]], 0
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C_4]], i1 [[C_1]], i1 false
+; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C_4]], i1 true, i1 false
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[RES:%.*]] = phi i1 [ [[C_1]], [[ENTRY:%.*]] ], [ [[SEL]], [[THEN]] ]
@@ -236,10 +236,10 @@ define i1 @and_select_scope_limited(i32 %x, i32 %y, i32 %z) {
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[EXIT:%.*]]
; CHECK: then:
; CHECK-NEXT: [[C_4:%.*]] = icmp eq i32 [[Z:%.*]], 0
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C_4]], i1 [[C_1]], i1 false
+; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C_4]], i1 true, i1 false
; CHECK-NEXT: br i1 [[SEL]], label [[T_1:%.*]], label [[EXIT]]
; CHECK: t.1:
-; CHECK-NEXT: ret i1 [[C_1]]
+; CHECK-NEXT: ret i1 true
; CHECK: exit:
; CHECK-NEXT: [[RES:%.*]] = phi i1 [ [[C_1]], [[ENTRY:%.*]] ], [ [[SEL]], [[THEN]] ]
; CHECK-NEXT: ret i1 [[RES]]
@@ -328,7 +328,7 @@ define i1 @test_and_used_in_false_branch(i8 %x) {
; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_1]], [[T_1]]
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
-; CHECK-NEXT: ret i1 [[T_1]]
+; CHECK-NEXT: ret i1 true
; CHECK: else:
; CHECK-NEXT: ret i1 [[T_1]]
;
@@ -356,7 +356,7 @@ define i1 @test_or_used_in_false_branch(i8 %x) {
; CHECK: then:
; CHECK-NEXT: ret i1 [[T_1]]
; CHECK: else:
-; CHECK-NEXT: ret i1 [[T_1]]
+; CHECK-NEXT: ret i1 false
;
entry:
@@ -382,7 +382,7 @@ define i1 @test_or_used_in_false_branch2(i8 %x) {
; CHECK: then:
; CHECK-NEXT: ret i1 [[T_1]]
; CHECK: else:
-; CHECK-NEXT: ret i1 [[T_1]]
+; CHECK-NEXT: ret i1 false
;
entry:
diff --git a/llvm/test/Transforms/ConstraintElimination/assumes.ll b/llvm/test/Transforms/ConstraintElimination/assumes.ll
index 199c9660117db..fd1f2cb293538 100644
--- a/llvm/test/Transforms/ConstraintElimination/assumes.ll
+++ b/llvm/test/Transforms/ConstraintElimination/assumes.ll
@@ -500,7 +500,6 @@ exit:
}
; The information of from the assume can be used to simplify %t.2.
-; TODO
define i1 @assume_single_bb_conditions_after_assume(i8 %a, i8 %b, i1 %c) {
; CHECK-LABEL: @assume_single_bb_conditions_after_assume(
; CHECK-NEXT: [[ADD_1:%.*]] = add nuw nsw i8 [[A:%.*]], 1
@@ -510,7 +509,7 @@ define i1 @assume_single_bb_conditions_after_assume(i8 %a, i8 %b, i1 %c) {
; CHECK-NEXT: call void @may_unwind()
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP_1]])
; CHECK-NEXT: [[T_2:%.*]] = icmp ule i8 [[A]], [[B]]
-; CHECK-NEXT: [[RES_1:%.*]] = xor i1 [[C_1]], true
+; CHECK-NEXT: [[RES_1:%.*]] = xor i1 true, true
; CHECK-NEXT: [[ADD_2:%.*]] = add nuw nsw i8 [[A]], 2
; CHECK-NEXT: [[C_2:%.*]] = icmp ule i8 [[ADD_2]], [[B]]
; CHECK-NEXT: [[RES_2:%.*]] = xor i1 [[RES_1]], [[C_2]]
@@ -575,7 +574,7 @@ define i1 @all_uses_after_assume(i8 %a, i8 %b, i1 %c) {
; CHECK-NEXT: call void @use(i1 [[C_1]])
; CHECK-NEXT: call void @may_unwind()
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP_1]])
-; CHECK-NEXT: [[RES_1:%.*]] = xor i1 [[C_1]], [[T_2]]
+; CHECK-NEXT: [[RES_1:%.*]] = xor i1 true, true
; CHECK-NEXT: [[ADD_2:%.*]] = add nuw nsw i8 [[A]], 2
; CHECK-NEXT: [[C_2:%.*]] = icmp ule i8 [[ADD_2]], [[B]]
; CHECK-NEXT: [[RES_2:%.*]] = xor i1 [[RES_1]], [[C_2]]
@@ -607,7 +606,7 @@ define i1 @test_order_assume_and_conds_in_
diff erent_bb(i16 %a, ptr %dst) {
; CHECK-NEXT: store volatile float 0.000000e+00, ptr [[DST:%.*]], align 4
; CHECK-NEXT: [[C_2:%.*]] = icmp eq i16 [[A]], 20
; CHECK-NEXT: tail call void @llvm.assume(i1 [[C_2]])
-; CHECK-NEXT: ret i1 [[C_2]]
+; CHECK-NEXT: ret i1 true
;
entry:
%c.1 = icmp ult i16 %a, 10
diff --git a/llvm/test/Transforms/ConstraintElimination/cond-used-in-phi.ll b/llvm/test/Transforms/ConstraintElimination/cond-used-in-phi.ll
index bdd5dadd4645d..b14c4437c1b59 100644
--- a/llvm/test/Transforms/ConstraintElimination/cond-used-in-phi.ll
+++ b/llvm/test/Transforms/ConstraintElimination/cond-used-in-phi.ll
@@ -175,7 +175,7 @@ define i1 @test_if_then_2(i1 %c, i8 %x) {
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP1]])
; CHECK-NEXT: br label [[JOIN]]
; CHECK: join:
-; CHECK-NEXT: [[PHI:%.*]] = phi i1 [ [[CMP2]], [[IF]] ], [ false, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[PHI:%.*]] = phi i1 [ true, [[IF]] ], [ false, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i1 [[PHI]]
;
entry:
@@ -203,7 +203,7 @@ define i1 @test_if_then_3(i1 %c.0, i8 %x) {
; CHECK: then.1:
; CHECK-NEXT: br label [[JOIN]]
; CHECK: join:
-; CHECK-NEXT: [[PHI:%.*]] = phi i1 [ [[CMP2]], [[IF]] ], [ [[CMP2]], [[THEN_1]] ], [ false, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[PHI:%.*]] = phi i1 [ [[CMP2]], [[IF]] ], [ true, [[THEN_1]] ], [ false, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i1 [[PHI]]
;
entry:
@@ -235,7 +235,7 @@ define i1 @test_if_then_4(i1 %c.0, i8 %x) {
; CHECK: else.1:
; CHECK-NEXT: br label [[JOIN]]
; CHECK: join:
-; CHECK-NEXT: [[PHI:%.*]] = phi i1 [ [[CMP2]], [[ELSE_1]] ], [ [[CMP2]], [[THEN_1]] ], [ false, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[PHI:%.*]] = phi i1 [ false, [[ELSE_1]] ], [ true, [[THEN_1]] ], [ false, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i1 [[PHI]]
;
entry:
diff --git a/llvm/test/Transforms/ConstraintElimination/monotonic-pointer-phis-crashes.ll b/llvm/test/Transforms/ConstraintElimination/monotonic-pointer-phis-crashes.ll
index 37e0bace7fddf..db241cefd59f5 100644
--- a/llvm/test/Transforms/ConstraintElimination/monotonic-pointer-phis-crashes.ll
+++ b/llvm/test/Transforms/ConstraintElimination/monotonic-pointer-phis-crashes.ll
@@ -66,7 +66,7 @@ define void @test_cond_multi_use_with_one_use_simplified_before_adding_ne_fact(p
; CHECK-NEXT: br i1 [[C_1]], label [[IF:%.*]], label [[LOOP_HEADER]]
; CHECK: if:
; CHECK-NEXT: [[C_2:%.*]] = icmp ne ptr [[B]], null
-; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_2]], [[C_0]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_2]], true
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[EXIT]]
; CHECK: then:
; CHECK-NEXT: call void @clobber()
diff --git a/llvm/test/Transforms/ConstraintElimination/uses-in-
diff erent-blocks.ll b/llvm/test/Transforms/ConstraintElimination/uses-in-
diff erent-blocks.ll
index e77fe44d380d8..021f338a735ed 100644
--- a/llvm/test/Transforms/ConstraintElimination/uses-in-
diff erent-blocks.ll
+++ b/llvm/test/Transforms/ConstraintElimination/uses-in-
diff erent-blocks.ll
@@ -9,7 +9,7 @@ define i1 @test_conds_single_use_in_
diff erent_blocks(i8 %x) {
; CHECK-NEXT: [[C_2:%.*]] = icmp ugt i8 [[X]], 5
; CHECK-NEXT: br i1 [[C_1]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
-; CHECK-NEXT: ret i1 [[T_1]]
+; CHECK-NEXT: ret i1 true
; CHECK: else:
; CHECK-NEXT: ret i1 [[C_2]]
;
@@ -38,7 +38,7 @@ define i1 @test_conds_single_use_in_
diff erent_blocks_2(i8 %x, i8 %y) {
; CHECK: then.1:
; CHECK-NEXT: br i1 [[C_2]], label [[THEN_2:%.*]], label [[ELSE]]
; CHECK: then.2:
-; CHECK-NEXT: ret i1 [[T_1]]
+; CHECK-NEXT: ret i1 true
; CHECK: else:
; CHECK-NEXT: ret i1 [[C_3]]
;
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