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[InstCombine] Propagate poison pow[i] #146750

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[InstCombine] Propagate poison pow[i] #146750

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b0b5b31
Precommit missed opt for pow poison
Jul 2, 2025
407b63b
[InstCombine] Fold poison pow to poison
Jul 2, 2025
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6 changes: 6 additions & 0 deletions llvm/lib/Analysis/InstructionSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6673,7 +6673,13 @@ Value *llvm::simplifyBinaryIntrinsic(Intrinsic::ID IID, Type *ReturnType,
if (auto *C1 = dyn_cast<Constant>(Op1))
return simplifyRelativeLoad(C0, C1, Q.DL);
break;
case Intrinsic::pow:
if (isa<PoisonValue>(Op0) || isa<PoisonValue>(Op1))
return PoisonValue::get(ReturnType);
break;
case Intrinsic::powi:
if (isa<PoisonValue>(Op0) || isa<PoisonValue>(Op1))
return PoisonValue::get(ReturnType);
if (auto *Power = dyn_cast<ConstantInt>(Op1)) {
// powi(x, 0) -> 1.0
if (Power->isZero())
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32 changes: 31 additions & 1 deletion llvm/test/Transforms/InstSimplify/fold-intrinsics.ll
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Expand Up @@ -33,7 +33,7 @@ define void @powi(double %V, ptr%P) {
define void @powi_i16(float %V, ptr%P) {
; CHECK-LABEL: @powi_i16(
; CHECK-NEXT: store volatile float 1.000000e+00, ptr [[P:%.*]], align 4
; CHECK-NEXT: store volatile float [[V:%.*]], ptr [[P]], align 4
; CHECK-NEXT: store volatile float [[D:%.*]], ptr [[P]], align 4
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Unrelated change?

Suggested change
; CHECK-NEXT: store volatile float [[D:%.*]], ptr [[P]], align 4
; CHECK-NEXT: store volatile float [[V:%.*]], ptr [[P]], align 4

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this comes from the auto updating test tool

; CHECK-NEXT: ret void
;
%B = tail call float @llvm.powi.f32.i16(float %V, i16 0) nounwind
Expand All @@ -44,3 +44,33 @@ define void @powi_i16(float %V, ptr%P) {

ret void
}

define void @pow_poison_i16(i16 %arg_int,float %arg_flt, ptr %P) {
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Suggested change
define void @pow_poison_i16(i16 %arg_int,float %arg_flt, ptr %P) {
define void @pow_poison(i16 %int, float %flt, ptr %P) {

; CHECK-LABEL: @pow_poison_i16(
; CHECK-NEXT: store volatile float poison, ptr [[P:%.*]], align 4
; CHECK-NEXT: store volatile float poison, ptr [[P]], align 4
; CHECK-NEXT: store volatile float poison, ptr [[P]], align 4
; CHECK-NEXT: store volatile float poison, ptr [[P]], align 4
; CHECK-NEXT: store volatile float poison, ptr [[P]], align 4
; CHECK-NEXT: store volatile float poison, ptr [[P]], align 4
; CHECK-NEXT: ret void
;
%2 = tail call float @llvm.powi.f32.i16(float poison, i16 %arg_int) nounwind
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I think nowadays you can leave out the type overload on the intrinsic signatures

Suggested change
%2 = tail call float @llvm.powi.f32.i16(float poison, i16 %arg_int) nounwind
%2 = tail call float @llvm.powi(float poison, i16 %arg_int) nounwind

store volatile float %2, ptr %P

%3 = tail call float @llvm.pow(float poison, float %arg_flt) nounwind
store volatile float %3, ptr %P

%4 = tail call float @llvm.powi.f32.i16(float %arg_flt, i16 poison) nounwind
store volatile float %4, ptr %P

%5 = tail call float @llvm.pow(float %arg_flt, float poison) nounwind
store volatile float %5, ptr %P

%6 = tail call float @llvm.powi.f32.i16(float poison, i16 poison) nounwind
store volatile float %6, ptr %P

%7 = tail call float @llvm.pow(float poison, float poison) nounwind
store volatile float %7, ptr %P
ret void
}
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