[DAGCombiner] Use HandleSDNode to keep node alive across call to getNegatedExpression.

[craig.topper]

Summary

getNegatedExpression can delete nodes. If the first call to
getNegatedExpression produced a node that the second call also
manages to create, it might get deleted. Use a HandleSDNode to
ensure it has a use to prevent it from being deleted.

Fixes PR57658.

[craig.topper]

clang-format

[RKSimon]

LGTM

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

 //===- DAGCombiner.cpp - Implement a DAG node combiner --------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
SDValue DAGCombiner::visitFMUL(SDNode *N) {
 
   // -N0 * -N1 --> N0 * N1
   TargetLowering::NegatibleCost CostN0 =
       TargetLowering::NegatibleCost::Expensive;
   TargetLowering::NegatibleCost CostN1 =
       TargetLowering::NegatibleCost::Expensive;
   SDValue NegN0 =
       TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize, CostN0);
+  if (NegN0) {
+    HandleSDNode NegN0Handle(NegN0);
     SDValue NegN1 =
         TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
-  if (NegN0 && NegN1 &&
-      (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
+    if (NegN1 && (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
                   CostN1 == TargetLowering::NegatibleCost::Cheaper))
       return DAG.getNode(ISD::FMUL, DL, VT, NegN0, NegN1);
+  }
 
   // fold (fmul X, (select (fcmp X > 0.0), -1.0, 1.0)) -> (fneg (fabs X))
   // fold (fmul X, (select (fcmp X > 0.0), 1.0, -1.0)) -> (fabs X)
   if (Flags.hasNoNaNs() && Flags.hasNoSignedZeros() &&
       (N0.getOpcode() == ISD::SELECT || N1.getOpcode() == ISD::SELECT) &&
       TLI.isOperationLegal(ISD::FABS, VT)) {
     SDValue Select = N0, X = N1;
     if (Select.getOpcode() != ISD::SELECT)
SDValue DAGCombiner::visitFMA(SDNode *N) {
 
   // (-N0 * -N1) + N2 --> (N0 * N1) + N2
   TargetLowering::NegatibleCost CostN0 =
       TargetLowering::NegatibleCost::Expensive;
   TargetLowering::NegatibleCost CostN1 =
       TargetLowering::NegatibleCost::Expensive;
   SDValue NegN0 =
       TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize, CostN0);
+  if (NegN0) {
+    HandleSDNode NegN0Handle(NegN0);
     SDValue NegN1 =
         TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
-  if (NegN0 && NegN1 &&
-      (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
+    if (NegN1 && (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
                   CostN1 == TargetLowering::NegatibleCost::Cheaper))
       return DAG.getNode(ISD::FMA, DL, VT, NegN0, NegN1, N2);
+  }
 
   // FIXME: use fast math flags instead of Options.UnsafeFPMath
   if (Options.UnsafeFPMath) {
     if (N0CFP && N0CFP->isZero())
       return N2;
     if (N1CFP && N1CFP->isZero())
       return N2;
   }
SDValue DAGCombiner::visitFDIV(SDNode *N) {
 
   // (fdiv (fneg X), (fneg Y)) -> (fdiv X, Y)
   TargetLowering::NegatibleCost CostN0 =
       TargetLowering::NegatibleCost::Expensive;
   TargetLowering::NegatibleCost CostN1 =
       TargetLowering::NegatibleCost::Expensive;
   SDValue NegN0 =
       TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize, CostN0);
+  if (NegN0) {
+    HandleSDNode NegN0Handle(NegN0);
     SDValue NegN1 =
         TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
-  if (NegN0 && NegN1 &&
-      (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
+    if (NegN1 && (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
                   CostN1 == TargetLowering::NegatibleCost::Cheaper))
       return DAG.getNode(ISD::FDIV, SDLoc(N), VT, NegN0, NegN1);
+  }
 
   return SDValue();
 }
 
 SDValue DAGCombiner::visitFREM(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
   EVT VT = N->getValueType(0);

llvm/test/CodeGen/X86/pr57658.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+
+define <2 x double> @f(<2 x double> %I) {
+; CHECK-LABEL: f:
+; CHECK:       # %bb.0: # %BB
+; CHECK-NEXT:    movapd {{.*#+}} xmm1 = [-0.0E+0,-0.0E+0]
+; CHECK-NEXT:    xorpd %xmm0, %xmm1
+; CHECK-NEXT:    mulpd %xmm0, %xmm1
+; CHECK-NEXT:    mulpd %xmm0, %xmm1
+; CHECK-NEXT:    mulpd %xmm0, %xmm0
+; CHECK-NEXT:    mulpd %xmm1, %xmm0
+; CHECK-NEXT:    retq
+BB:
+  %F = fneg <2 x double> %I
+  %B3 = fmul <2 x double> %I, %F
+  %B1 = fmul <2 x double> %F, %B3
+  %B2 = fmul <2 x double> %F, %I
+  %B = fmul <2 x double> %B2, %B1
+  ret <2 x double> %B
+}