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[X86][TargetLowering] Avoid deleting temporary nodes in getNegatedExpression #139029

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Merged
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May 10, 2025
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[X86][TargetLowering] Avoid deleting temporary nodes in getNegatedExpression #139029

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9 changes: 8 additions & 1 deletion llvm/lib/Target/X86/X86ISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -54678,12 +54678,19 @@ SDValue X86TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
if (!Flags.hasNoSignedZeros())
break;

// Because getCheaperNegatedExpression can delete nodes we need a handle to
// keep temporary nodes alive.
std::list<HandleSDNode> Handles;
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std::optional<HandleSDNode> Handles[3] may be better.


// This is always negatible for free but we might be able to remove some
// extra operand negations as well.
SmallVector<SDValue, 4> NewOps(Op.getNumOperands(), SDValue());
for (int i = 0; i != 3; ++i)
for (int i = 0; i != 3; ++i) {
NewOps[i] = getCheaperNegatedExpression(
Op.getOperand(i), DAG, LegalOperations, ForCodeSize, Depth + 1);
if (!!NewOps[i])
Handles.emplace_back(NewOps[i]);
}

bool NegA = !!NewOps[0];
bool NegB = !!NewOps[1];
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23 changes: 23 additions & 0 deletions llvm/test/CodeGen/X86/pr138982.ll
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@@ -0,0 +1,23 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
; RUN: llc < %s -mtriple=x86_64 -mattr=+fma | FileCheck %s

define <4 x float> @pr138982(<4 x float> %in_vec) {
; CHECK-LABEL: pr138982:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: vxorps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %xmm1
; CHECK-NEXT: vrcpps %xmm0, %xmm2
; CHECK-NEXT: vrcpps %xmm1, %xmm1
; CHECK-NEXT: vxorps %xmm3, %xmm3, %xmm3
; CHECK-NEXT: vcmpneqps %xmm0, %xmm3, %xmm0
; CHECK-NEXT: vbroadcastss {{.*#+}} xmm4 = [1.0E+0,1.0E+0,1.0E+0,1.0E+0]
; CHECK-NEXT: vblendvps %xmm0, %xmm1, %xmm4, %xmm0
; CHECK-NEXT: vfnmadd231ps {{.*#+}} xmm0 = -(xmm3 * xmm2) + xmm0
; CHECK-NEXT: retq
entry:
%fneg = fneg <4 x float> %in_vec
%rcp = tail call <4 x float> @llvm.x86.sse.rcp.ps(<4 x float> %fneg)
%cmp = fcmp une <4 x float> zeroinitializer, %in_vec
%sel = select <4 x i1> %cmp, <4 x float> %rcp, <4 x float> splat (float 1.000000e+00)
%fma = call nsz <4 x float> @llvm.fma.v4f32(<4 x float> %rcp, <4 x float> zeroinitializer, <4 x float> %sel)
ret <4 x float> %fma
}
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