[llvm-commits] [llvm] r152777 - /llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

[Bill Wendling]

Author: void
Date: Thu Mar 15 00:12:00 2012
New Revision: 152777

URL: http://llvm.org/viewvc/llvm-project?rev=152777&view=rev
Log:
Add a xform to the DAG combiner.

Transform:

        (fsub x, (fadd x, y)) -> (fneg y) and
        (fsub x, (fadd y, x)) -> (fneg y)

if 'unsafe math' is specified.
<rdar://problem/7540295>

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=152777&r1=152776&r2=152777&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Mar 15 00:12:00 2012
@@ -5568,6 +5568,23 @@
     return DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N0,
                        GetNegatedExpression(N1, DAG, LegalOperations));
 
+  // If 'unsafe math' is enabled, fold
+  //    (fsub x, (fadd x, y)) -> (fneg y) &
+  //    (fsub x, (fadd y, x)) -> (fneg y)
+  if (DAG.getTarget().Options.UnsafeFPMath) {
+    if (N1.getOpcode() == ISD::FADD) {
+      SDValue N10 = N1->getOperand(0);
+      SDValue N11 = N1->getOperand(1);
+
+      if (N10 == N0 && isNegatibleForFree(N11, LegalOperations, TLI,
+                                          &DAG.getTarget().Options))
+        return GetNegatedExpression(N11, DAG, LegalOperations);
+      else if (N11 == N0 && isNegatibleForFree(N10, LegalOperations, TLI,
+                                               &DAG.getTarget().Options))
+        return GetNegatedExpression(N10, DAG, LegalOperations);
+    }
+  }
+
   return SDValue();
 }