commit 713e953118175d693a3fddbf6a61dc73aa69ad87
author Owen Anderson <resistor@mac.com> Mon May 07 20:51:25 2012 +0000
committer Owen Anderson <resistor@mac.com> Mon May 07 20:51:25 2012 +0000
tree ef945f02d87468cf3a09338e3fda0a36da75128f
parent 423f19f2dadee9325766008b63c1faf3c644043b

Teach DAG combine to fold x-x to 0.0 when unsafe FP math is enabled.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156324 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c2b7f6c..753ba93 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5670,9 +5670,13 @@
                        GetNegatedExpression(N1, DAG, LegalOperations));
 
   // If 'unsafe math' is enabled, fold
+  //    (fsub x, x) -> 0.0 &
   //    (fsub x, (fadd x, y)) -> (fneg y) &
   //    (fsub x, (fadd y, x)) -> (fneg y)
   if (DAG.getTarget().Options.UnsafeFPMath) {
+    if (N0 == N1)
+      return DAG.getConstantFP(0.0f, VT);
+
     if (N1.getOpcode() == ISD::FADD) {
       SDValue N10 = N1->getOperand(0);
       SDValue N11 = N1->getOperand(1);