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[ValueTracking] Support scalable vector splats of ConstantInt/ConstantFP in isGuaranteedNotToBeUndefOrPoison. #142894

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Merged
merged 3 commits into from
Jun 6, 2025
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[ValueTracking] Support scalable vector splats of ConstantInt/ConstantFP in isGuaranteedNotToBeUndefOrPoison. #142894

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Pre-commit tests
topperc Jun 5, 2025
7a546df
[ValueTracking] Support scalable vector splats of ConstantInt in isGu…
topperc Jun 5, 2025
fa4e6e0
fixup! Add ConstantFP too
topperc Jun 5, 2025
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21 changes: 14 additions & 7 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7579,16 +7579,23 @@ static bool isGuaranteedNotToBeUndefOrPoison(
if (isa<UndefValue>(C))
return !includesUndef(Kind);

if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(V) ||
if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(C) ||
isa<ConstantPointerNull>(C) || isa<Function>(C))
return true;

if (C->getType()->isVectorTy() && !isa<ConstantExpr>(C)) {
if (includesUndef(Kind) && C->containsUndefElement())
return false;
if (includesPoison(Kind) && C->containsPoisonElement())
return false;
return !C->containsConstantExpression();
if (C->getType()->isVectorTy()) {
if (isa<ConstantExpr>(C)) {
// Scalable vectors can use a ConstantExpr to build a splat.
if (Constant *SplatC = C->getSplatValue())
if (isa<ConstantInt>(SplatC))
return true;
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@dtcxzyw dtcxzyw Jun 5, 2025

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Any reason not to support fp/ptr splats?

Suggested change
if (isa<ConstantInt>(SplatC))
return true;
return isGuaranteedNotToBeUndefOrPoison(SplatC, ...);

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@topperc topperc Jun 5, 2025 •
edited
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Any reason not to support fp/ptr splats?

Just lack of tests. Should we increase the depth on the recursive call to isGuaranteedNotToBeUndefOrPoison or keep the current depth.

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@dtcxzyw dtcxzyw Jun 5, 2025

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The latter one is ok.

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@topperc topperc Jun 5, 2025

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I added ConstantFP and an Attributor test was changed so that has some coverage.

Will a splat of ConstantPointerNull be folded to ConstantAggregateZero at creation?

} else {
if (includesUndef(Kind) && C->containsUndefElement())
return false;
if (includesPoison(Kind) && C->containsPoisonElement())
return false;
return !C->containsConstantExpression();
}
}
}

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28 changes: 28 additions & 0 deletions llvm/test/Transforms/InstCombine/select-and-or.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,20 @@ define i1 @logical_or_implies(i32 %x) {
ret i1 %res
}

; Safe to convert to or due to poison implication.
define <vscale x 2 x i1> @logical_or_implies_scalablevec(<vscale x 2 x i32> %x) {
; CHECK-LABEL: @logical_or_implies_scalablevec(
; CHECK-NEXT: [[C1:%.*]] = icmp eq <vscale x 2 x i32> [[X:%.*]], zeroinitializer
; CHECK-NEXT: [[C2:%.*]] = icmp eq <vscale x 2 x i32> [[X]], splat (i32 42)
; CHECK-NEXT: [[RES:%.*]] = or <vscale x 2 x i1> [[C1]], [[C2]]
; CHECK-NEXT: ret <vscale x 2 x i1> [[RES]]
;
%c1 = icmp eq <vscale x 2 x i32> %x, zeroinitializer
%c2 = icmp eq <vscale x 2 x i32> %x, splat (i32 42)
%res = select <vscale x 2 x i1> %c1, <vscale x 2 x i1> splat (i1 true), <vscale x 2 x i1> %c2
ret <vscale x 2 x i1> %res
}

; Will fold after conversion to or.
define i1 @logical_or_implies_folds(i32 %x) {
; CHECK-LABEL: @logical_or_implies_folds(
Expand All @@ -129,6 +143,20 @@ define i1 @logical_and_implies(i32 %x) {
ret i1 %res
}

; Safe to convert to and due to poison implication.
define <vscale x 2 x i1> @logical_and_implies_scalablevec(<vscale x 2 x i32> %x) {
; CHECK-LABEL: @logical_and_implies_scalablevec(
; CHECK-NEXT: [[C1:%.*]] = icmp ne <vscale x 2 x i32> [[X:%.*]], zeroinitializer
; CHECK-NEXT: [[C2:%.*]] = icmp ne <vscale x 2 x i32> [[X]], splat (i32 42)
; CHECK-NEXT: [[RES:%.*]] = and <vscale x 2 x i1> [[C1]], [[C2]]
; CHECK-NEXT: ret <vscale x 2 x i1> [[RES]]
;
%c1 = icmp ne <vscale x 2 x i32> %x, zeroinitializer
%c2 = icmp ne <vscale x 2 x i32> %x, splat (i32 42)
%res = select <vscale x 2 x i1> %c1, <vscale x 2 x i1> %c2, <vscale x 2 x i1> zeroinitializer
ret <vscale x 2 x i1> %res
}

; Will fold after conversion to and.
define i1 @logical_and_implies_folds(i32 %x) {
; CHECK-LABEL: @logical_and_implies_folds(
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