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

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.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D133602

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c215772..fcd3dcb 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -15079,12 +15079,14 @@ SDValue DAGCombiner::visitFMUL(SDNode *N) {
       TargetLowering::NegatibleCost::Expensive;
   SDValue NegN0 =
       TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize, CostN0);
-  SDValue NegN1 =
-      TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
-  if (NegN0 && NegN1 &&
-      (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
-       CostN1 == TargetLowering::NegatibleCost::Cheaper))
-    return DAG.getNode(ISD::FMUL, DL, VT, NegN0, NegN1);
+  if (NegN0) {
+    HandleSDNode NegN0Handle(NegN0);
+    SDValue NegN1 =
+        TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
+    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)
@@ -15170,12 +15172,14 @@ SDValue DAGCombiner::visitFMA(SDNode *N) {
       TargetLowering::NegatibleCost::Expensive;
   SDValue NegN0 =
       TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize, CostN0);
-  SDValue NegN1 =
-      TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
-  if (NegN0 && NegN1 &&
-      (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
-       CostN1 == TargetLowering::NegatibleCost::Cheaper))
-    return DAG.getNode(ISD::FMA, DL, VT, NegN0, NegN1, N2);
+  if (NegN0) {
+    HandleSDNode NegN0Handle(NegN0);
+    SDValue NegN1 =
+        TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
+    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) {
@@ -15473,12 +15477,14 @@ SDValue DAGCombiner::visitFDIV(SDNode *N) {
       TargetLowering::NegatibleCost::Expensive;
   SDValue NegN0 =
       TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize, CostN0);
-  SDValue NegN1 =
-      TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
-  if (NegN0 && NegN1 &&
-      (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
-       CostN1 == TargetLowering::NegatibleCost::Cheaper))
-    return DAG.getNode(ISD::FDIV, SDLoc(N), VT, NegN0, NegN1);
+  if (NegN0) {
+    HandleSDNode NegN0Handle(NegN0);
+    SDValue NegN1 =
+        TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
+    if (NegN1 && (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
+                  CostN1 == TargetLowering::NegatibleCost::Cheaper))
+      return DAG.getNode(ISD::FDIV, SDLoc(N), VT, NegN0, NegN1);
+  }
 
   return SDValue();
 }

diff --git a/llvm/test/CodeGen/X86/pr57658.ll b/llvm/test/CodeGen/X86/pr57658.ll
new file mode 100644 (file)
index 0000000..15ae12a
--- /dev/null
+++ b/llvm/test/CodeGen/X86/pr57658.ll
@@ -0,0 +1,21 @@
+; 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
+}