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[InstCombine] Avoid self-replacing in getUndefReplacement #161500

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Merged
merged 2 commits into from
Oct 1, 2025
Merged

[InstCombine] Avoid self-replacing in getUndefReplacement #161500

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b3adfaf
[InstCombine] Add pre-commit tests. NFC.
dtcxzyw Oct 1, 2025
8ba650a
[InstCombine] Avoid self-replacing in `getUndefReplacement`
dtcxzyw Oct 1, 2025
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3 changes: 2 additions & 1 deletion llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5212,7 +5212,7 @@ Instruction *InstCombinerImpl::visitFreeze(FreezeInst &I) {
else if (match(U, m_Select(m_Specific(&I), m_Constant(), m_Value())))
V = ConstantInt::getTrue(Ty);
else if (match(U, m_c_Select(m_Specific(&I), m_Value(V)))) {
if (!isGuaranteedNotToBeUndefOrPoison(V, &AC, &I, &DT))
if (V == &I || !isGuaranteedNotToBeUndefOrPoison(V, &AC, &I, &DT))
V = NullValue;
} else if (auto *PHI = dyn_cast<PHINode>(U)) {
if (Value *MaybeV = pickCommonConstantFromPHI(*PHI))
Expand All @@ -5225,6 +5225,7 @@ Instruction *InstCombinerImpl::visitFreeze(FreezeInst &I) {
BestValue = NullValue;
}
assert(BestValue && "Must have at least one use");
assert(BestValue != &I && "Cannot replace with itself");
return BestValue;
};

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21 changes: 21 additions & 0 deletions llvm/test/Transforms/InstCombine/freeze.ll
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Expand Up @@ -1464,6 +1464,27 @@ define ptr @freeze_ptrmask_nonnull(ptr %p, i64 noundef %m) {
ret ptr %fr
}

define i64 @pr161492_1(i1 %cond) {
; CHECK-LABEL: define i64 @pr161492_1(
; CHECK-SAME: i1 [[COND:%.*]]) {
; CHECK-NEXT: ret i64 0
;
%fr1 = freeze i64 poison
%fr2 = freeze i64 poison
%ret = select i1 %cond, i64 %fr1, i64 %fr2
ret i64 %ret
}

define i64 @pr161492_2(i1 %cond) {
; CHECK-LABEL: define i64 @pr161492_2(
; CHECK-SAME: i1 [[COND:%.*]]) {
; CHECK-NEXT: ret i64 0
;
%fr = freeze i64 poison
%ret = select i1 %cond, i64 %fr, i64 %fr
ret i64 %ret
}

!0 = !{}
!1 = !{i64 4}
!2 = !{i32 0, i32 100}
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