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[GVN] Handle provenance when propagating assume equality #151953

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Merged
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Aug 5, 2025
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[GVN] Handle provenance when propagating assume equality #151953

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f39f423
[GVN] Add tests for ptr replacement for assumes
nikic Aug 4, 2025
8679ee2
[GVN] Check provenance when propagating assume equality
nikic Aug 4, 2025
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8 changes: 4 additions & 4 deletions llvm/lib/Transforms/Scalar/GVN.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2499,11 +2499,11 @@ void GVNPass::assignBlockRPONumber(Function &F) {
bool GVNPass::replaceOperandsForInBlockEquality(Instruction *Instr) const {
bool Changed = false;
for (unsigned OpNum = 0; OpNum < Instr->getNumOperands(); ++OpNum) {
Value *Operand = Instr->getOperand(OpNum);
auto It = ReplaceOperandsWithMap.find(Operand);
Use &Operand = Instr->getOperandUse(OpNum);
auto It = ReplaceOperandsWithMap.find(Operand.get());
if (It != ReplaceOperandsWithMap.end()) {
// Do not replace lifetime alloca argument with something else.
if (Instr->isLifetimeStartOrEnd())
const DataLayout &DL = Instr->getDataLayout();
if (!canReplacePointersInUseIfEqual(Operand, It->second, DL))
continue;

LLVM_DEBUG(dbgs() << "GVN replacing: " << *Operand << " with "
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44 changes: 44 additions & 0 deletions llvm/test/Transforms/GVN/assume-equal.ll
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Expand Up @@ -343,6 +343,50 @@ meh:
ret i1 %k
}

define i8 @assume_ptr_eq_different_prov_matters(ptr %p, ptr %p2) {
; CHECK-LABEL: define i8 @assume_ptr_eq_different_prov_matters(
; CHECK-SAME: ptr [[P:%.*]], ptr [[P2:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[P]], [[P2]]
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: [[V:%.*]] = load i8, ptr [[P2]], align 1
; CHECK-NEXT: ret i8 [[V]]
;
%cmp = icmp eq ptr %p, %p2
call void @llvm.assume(i1 %cmp)
%v = load i8, ptr %p2
ret i8 %v
}

define i1 @assume_ptr_eq_different_prov_does_not_matter(ptr %p, ptr %p2) {
; CHECK-LABEL: define i1 @assume_ptr_eq_different_prov_does_not_matter(
; CHECK-SAME: ptr [[P:%.*]], ptr [[P2:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[P]], [[P2]]
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: [[C:%.*]] = icmp eq ptr [[P]], null
; CHECK-NEXT: ret i1 [[C]]
;
%cmp = icmp eq ptr %p, %p2
call void @llvm.assume(i1 %cmp)
%c = icmp eq ptr %p2, null
ret i1 %c
}

define i8 @assume_ptr_eq_same_prov(ptr %p, i64 %x) {
; CHECK-LABEL: define i8 @assume_ptr_eq_same_prov(
; CHECK-SAME: ptr [[P:%.*]], i64 [[X:%.*]]) {
; CHECK-NEXT: [[P2:%.*]] = getelementptr i8, ptr [[P]], i64 [[X]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[P]], [[P2]]
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: [[V:%.*]] = load i8, ptr [[P]], align 1
; CHECK-NEXT: ret i8 [[V]]
;
%p2 = getelementptr i8, ptr %p, i64 %x
%cmp = icmp eq ptr %p, %p2
call void @llvm.assume(i1 %cmp)
%v = load i8, ptr %p2
ret i8 %v
}

declare noalias ptr @_Znwm(i64)
declare void @_ZN1AC1Ev(ptr)
declare void @llvm.assume(i1)
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2 changes: 1 addition & 1 deletion llvm/test/Transforms/GVN/lifetime-simple.ll
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Expand Up @@ -29,7 +29,7 @@ define void @assume_eq_arg(ptr %arg) {
; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[ALLOCA]], [[ARG]]
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr [[ALLOCA]])
; CHECK-NEXT: store volatile i32 0, ptr [[ARG]], align 4
; CHECK-NEXT: store volatile i32 0, ptr [[ALLOCA]], align 4
; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr [[ALLOCA]])
; CHECK-NEXT: ret void
;
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