Fix for bug reported by Evzen Muller on llvm-commits: make sure to correctly

check the range of the constant when optimizing a comparison between a
constant and a sign_extend_inreg node.

llvm-svn: 109854

1 files changed, 3 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 12185a3d4c3..908a9d8919d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1968,12 +1968,9 @@ TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
       EVT ExtDstTy = N0.getValueType();
       unsigned ExtDstTyBits = ExtDstTy.getSizeInBits();
 
-      // If the extended part has any inconsistent bits, it cannot ever
-      // compare equal.  In other words, they have to be all ones or all
-      // zeros.
-      APInt ExtBits =
-        APInt::getHighBitsSet(ExtDstTyBits, ExtDstTyBits - ExtSrcTyBits);
-      if ((C1 & ExtBits) != 0 && (C1 & ExtBits) != ExtBits)
+      // If the constant doesn't fit into the number of bits for the source of
+      // the sign extension, it is impossible for both sides to be equal.
+      if (C1.getMinSignedBits() > ExtSrcTyBits)
         return DAG.getConstant(Cond == ISD::SETNE, VT);
       
       SDValue ZextOp;