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[InstSimplify] Refine abs(min/undef, true) to poison #118669

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Merged
merged 1 commit into from
Dec 4, 2024
Merged

[InstSimplify] Refine abs(min/undef, true) to poison #118669

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4 changes: 2 additions & 2 deletions llvm/lib/Analysis/ConstantFolding.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3018,9 +3018,9 @@ static Constant *ConstantFoldIntrinsicCall2(Intrinsic::ID IntrinsicID, Type *Ty,
assert(C1 && "Must be constant int");
assert((C1->isOne() || C1->isZero()) && "Must be 0 or 1");

// Undef or minimum val operand with poison min --> undef
// Undef or minimum val operand with poison min --> poison
if (C1->isOne() && (!C0 || C0->isMinSignedValue()))
return UndefValue::get(Ty);
return PoisonValue::get(Ty);

// Undef operand with no poison min --> 0 (sign bit must be clear)
if (!C0)
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4 changes: 2 additions & 2 deletions llvm/test/Transforms/InstSimplify/ConstProp/abs.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ declare <8 x i8> @llvm.abs.v8i8(<8 x i8>, i1)

define i8 @undef_val_min_poison() {
; CHECK-LABEL: @undef_val_min_poison(
; CHECK-NEXT: ret i8 undef
; CHECK-NEXT: ret i8 poison
;
%r = call i8 @llvm.abs.i8(i8 undef, i1 true)
ret i8 %r
Expand All @@ -22,7 +22,7 @@ define i8 @undef_val_min_not_poison() {

define i8 @min_val_min_poison() {
; CHECK-LABEL: @min_val_min_poison(
; CHECK-NEXT: ret i8 undef
; CHECK-NEXT: ret i8 poison
;
%r = call i8 @llvm.abs.i8(i8 -128, i1 true)
ret i8 %r
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