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[ValueTracking] Support scalable vector splats in computeKnownFPClass #170325

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merged 2 commits into from
Dec 2, 2025
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[ValueTracking] Support scalable vector splats in computeKnownFPClass #170325

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[ValueTracking] Support scalable vector splats in computeKnownFPClass
dtcxzyw Dec 2, 2025
bd93bf7
[Attributor] Add tests. NFC.
dtcxzyw Dec 2, 2025
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6 changes: 6 additions & 0 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5877,6 +5877,12 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
break;
}
case Instruction::ShuffleVector: {
// Handle vector splat idiom
if (Value *Splat = getSplatValue(V)) {
computeKnownFPClass(Splat, Known, InterestedClasses, Q, Depth + 1);
break;
}

// For undef elements, we don't know anything about the common state of
// the shuffle result.
APInt DemandedLHS, DemandedRHS;
Expand Down
28 changes: 19 additions & 9 deletions llvm/test/Transforms/Attributor/nofpclass.ll
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Expand Up @@ -2667,15 +2667,10 @@ define [4 x float] @constant_aggregate_zero() {
}

define <vscale x 4 x float> @scalable_splat_pnorm() {
; CHECK-CV: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
; CHECK-CV-LABEL: define noundef <vscale x 4 x float> @scalable_splat_pnorm
; CHECK-CV-SAME: () #[[ATTR3]] {
; CHECK-CV-NEXT: ret <vscale x 4 x float> splat (float 1.000000e+00)
;
; CHECK-CI: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
; CHECK-CI-LABEL: define noundef nofpclass(nan inf zero sub nnorm) <vscale x 4 x float> @scalable_splat_pnorm
; CHECK-CI-SAME: () #[[ATTR3]] {
; CHECK-CI-NEXT: ret <vscale x 4 x float> splat (float 1.000000e+00)
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
; CHECK-LABEL: define noundef nofpclass(nan inf zero sub nnorm) <vscale x 4 x float> @scalable_splat_pnorm
; CHECK-SAME: () #[[ATTR3]] {
; CHECK-NEXT: ret <vscale x 4 x float> splat (float 1.000000e+00)
;
ret <vscale x 4 x float> splat (float 1.0)
}
Expand All @@ -2689,6 +2684,19 @@ define <vscale x 4 x float> @scalable_splat_zero() {
ret <vscale x 4 x float> zeroinitializer
}

define <vscale x 4 x float> @scalable_splat_nnan(float nofpclass(nan) %x) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
; CHECK-LABEL: define nofpclass(nan) <vscale x 4 x float> @scalable_splat_nnan
; CHECK-SAME: (float nofpclass(nan) [[X:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[HEAD:%.*]] = insertelement <vscale x 4 x float> poison, float [[X]], i32 0
; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <vscale x 4 x float> [[HEAD]], <vscale x 4 x float> poison, <vscale x 4 x i32> zeroinitializer
; CHECK-NEXT: ret <vscale x 4 x float> [[SPLAT]]
;
%head = insertelement <vscale x 4 x float> poison, float %x, i32 0
%splat = shufflevector <vscale x 4 x float> %head, <vscale x 4 x float> poison, <vscale x 4 x i32> zeroinitializer
ret <vscale x 4 x float> %splat
}

; Verify we do not derive 'nofpclass(inf zero sub norm)' for the argument __x.
; See https://github.com/llvm/llvm-project/issues/78507

Expand Down Expand Up @@ -2989,5 +2997,7 @@ attributes #5 = { "denormal-fp-math"="ieee,positive-zero" }
;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
; CGSCC-CI: {{.*}}
; CGSCC-CV: {{.*}}
; CHECK-CI: {{.*}}
; CHECK-CV: {{.*}}
; TUNIT-CI: {{.*}}
; TUNIT-CV: {{.*}}
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