commit 7c55c8d8c347c718dbe359cda064392de5fbf3e7
author Tim Renouf <tpr.llvm@botech.co.uk> Thu Apr 18 05:27:01 2019 +0000
committer Tim Renouf <tpr.llvm@botech.co.uk> Thu Apr 18 05:27:01 2019 +0000
tree 77d5592e66e789f95fe7c83ba594824d02d8ef13
parent 6263365b082d7e03988a45c113aa3099cabac5de

[AMDGPU] Avoid DAG combining assert with fneg(fadd(A,0))

fneg combining attempts to turn it into fadd(fneg(A), fneg(0)), but
creating the new fadd folds to just fneg(A). When A has multiple uses,
this confuses it and you get an assert. Fixed.

Differential Revision: https://reviews.llvm.org/D60633

Change-Id: I0ddc9b7286abe78edc0cd8d734fdeb05ff09821c
llvm-svn: 358640

llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
index 623d981..08affa8 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -3692,6 +3692,8 @@
       RHS = RHS.getOperand(0);
 
     SDValue Res = DAG.getNode(ISD::FADD, SL, VT, LHS, RHS, N0->getFlags());
+    if (Res.getOpcode() != ISD::FADD)
+      return SDValue(); // Op got folded away.
     if (!N0.hasOneUse())
       DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
     return Res;
@@ -3711,6 +3713,8 @@
       RHS = DAG.getNode(ISD::FNEG, SL, VT, RHS);
 
     SDValue Res = DAG.getNode(Opc, SL, VT, LHS, RHS, N0->getFlags());
+    if (Res.getOpcode() != Opc)
+      return SDValue(); // Op got folded away.
     if (!N0.hasOneUse())
       DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
     return Res;
@@ -3738,6 +3742,8 @@
       RHS = RHS.getOperand(0);
 
     SDValue Res = DAG.getNode(Opc, SL, VT, LHS, MHS, RHS);
+    if (Res.getOpcode() != Opc)
+      return SDValue(); // Op got folded away.
     if (!N0.hasOneUse())
       DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
     return Res;
@@ -3766,6 +3772,8 @@
     unsigned Opposite = inverseMinMax(Opc);
 
     SDValue Res = DAG.getNode(Opposite, SL, VT, NegLHS, NegRHS, N0->getFlags());
+    if (Res.getOpcode() != Opposite)
+      return SDValue(); // Op got folded away.
     if (!N0.hasOneUse())
       DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
     return Res;
@@ -3776,6 +3784,8 @@
       Ops[I] = DAG.getNode(ISD::FNEG, SL, VT, N0->getOperand(I), N0->getFlags());
 
     SDValue Res = DAG.getNode(AMDGPUISD::FMED3, SL, VT, Ops, N0->getFlags());
+    if (Res.getOpcode() != AMDGPUISD::FMED3)
+      return SDValue(); // Op got folded away.
     if (!N0.hasOneUse())
       DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
     return Res;