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[DAGCombiner] Don't ignore N2's undef elements in foldVSelectOfConstants #129272

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Merged
merged 2 commits into from
Mar 1, 2025
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[DAGCombiner] Don't ignore N2's undef elements in foldVSelectOfConstants #129272

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e4f4fad
[X86] Add pre-commit tests. NFC.
dtcxzyw Feb 28, 2025
1bc7458
[DAGCombiner] Don't ignore N2's undef elements in `foldVSelectOfConst…
dtcxzyw Feb 28, 2025
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5 changes: 3 additions & 2 deletions llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -12535,9 +12535,10 @@ SDValue DAGCombiner::foldVSelectOfConstants(SDNode *N) {
for (unsigned i = 0; i != Elts; ++i) {
SDValue N1Elt = N1.getOperand(i);
SDValue N2Elt = N2.getOperand(i);
if (N1Elt.isUndef() || N2Elt.isUndef())
if (N1Elt.isUndef())
continue;
if (N1Elt.getValueType() != N2Elt.getValueType()) {
// N2 should not contain undef values since it will be reused in the fold.
if (N2Elt.isUndef() || N1Elt.getValueType() != N2Elt.getValueType()) {
AllAddOne = false;
AllSubOne = false;
break;
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18 changes: 18 additions & 0 deletions llvm/test/CodeGen/X86/vselect-constants.ll
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Expand Up @@ -302,3 +302,21 @@ define i32 @wrong_min_signbits(<2 x i16> %x) {
%t1 = bitcast <2 x i16> %sel to i32
ret i32 %t1
}

define i32 @pr129181() {
; SSE-LABEL: pr129181:
; SSE: # %bb.0: # %entry
; SSE-NEXT: xorl %eax, %eax
; SSE-NEXT: retq
;
; AVX-LABEL: pr129181:
; AVX: # %bb.0: # %entry
; AVX-NEXT: xorl %eax, %eax
; AVX-NEXT: retq
entry:
%x = insertelement <4 x i32> zeroinitializer, i32 0, i32 0
%cmp = icmp ult <4 x i32> %x, splat (i32 1)
%sel = select <4 x i1> %cmp, <4 x i32> zeroinitializer, <4 x i32> <i32 0, i32 0, i32 1, i32 poison>
%reduce = tail call i32 @llvm.vector.reduce.add.v4i32(<4 x i32> %sel)
ret i32 %reduce
}
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