SelectionDAG: Improve legalization of SELECT_CC with illegal condition codes

SelectionDAG will now attempt to inverse an illegal conditon in order to
find a legal one and if that doesn't work, it will attempt to swap the
operands using the inverted condition.

There are no new test cases for this, but a nubmer of the existing R600
tests hit this path.

llvm-svn: 191602

1 files changed, 12 insertions, 4 deletions

diff --git a/llvm/lib/Target/R600/R600ISelLowering.cpp b/llvm/lib/Target/R600/R600ISelLowering.cpp
index 1d2c5e1bda4..5e9048a7019 100644
--- a/llvm/lib/Target/R600/R600ISelLowering.cpp
+++ b/llvm/lib/Target/R600/R600ISelLowering.cpp
@@ -862,10 +862,18 @@ SDValue R600TargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const
   ISD::CondCode CCOpcode = cast<CondCodeSDNode>(CC)->get();
   ISD::CondCode InverseCC =
      ISD::getSetCCInverse(CCOpcode, CompareVT == MVT::i32);
-  if (isHWTrueValue(False) && isHWFalseValue(True) &&
-      isCondCodeLegal(InverseCC, CompareVT.getSimpleVT())) {
-    std::swap(False, True);
-    CC = DAG.getCondCode(InverseCC);
+  if (isHWTrueValue(False) && isHWFalseValue(True)) {
+    if (isCondCodeLegal(InverseCC, CompareVT.getSimpleVT())) {
+      std::swap(False, True);
+      CC = DAG.getCondCode(InverseCC);
+    } else {
+      ISD::CondCode SwapInvCC = ISD::getSetCCSwappedOperands(InverseCC);
+      if (isCondCodeLegal(SwapInvCC, CompareVT.getSimpleVT())) {
+        std::swap(False, True);
+        std::swap(LHS, RHS);
+        CC = DAG.getCondCode(SwapInvCC);
+      }
+    }
   }
 
   if (isHWTrueValue(True) && isHWFalseValue(False) &&