SelectionDAG: create correct BooleanContent constants

Occasionally DAGCombiner can spot that a SETCC operation is completely
redundant and reduce it to "all true" or "all false". If this happens to a
vector, the value produced has to take account of what a normal comparison
would have produced, which may be an all-1s bitmask.

The fix in SelectionDAG.cpp is tested, however, as far as I can see the code in
TargetLowering.cpp is possibly unreachable and almost certainly irrelevant when
triggered so there are no tests. However, I believe it's still clearly the
right change and may save someone else some hassle if it suddenly becomes
reachable. So I'm doing it anyway.

llvm-svn: 190147

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index df672214365..f2199d7730d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1080,7 +1080,11 @@ TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
   case ISD::SETFALSE:
   case ISD::SETFALSE2: return DAG.getConstant(0, VT);
   case ISD::SETTRUE:
-  case ISD::SETTRUE2:  return DAG.getConstant(1, VT);
+  case ISD::SETTRUE2: {
+    TargetLowering::BooleanContent Cnt = getBooleanContents(VT.isVector());
+    return DAG.getConstant(
+        Cnt == TargetLowering::ZeroOrNegativeOneBooleanContent ? -1ULL : 1, VT);
+  }
   }
 
   // Ensure that the constant occurs on the RHS, and fold constant