Fix PR1499.

llvm-svn: 37472
2007-06-06 17:08:48 +00:00 · 2007-06-06 17:08:48 +00:00 · 368e8872db
parent cfb6f40424
commit 368e8872db
1 changed files with 4 additions and 0 deletions
--- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
@ -1346,6 +1346,10 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
      
      // Signed shift right.
      APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
+      // If any of the "high bits" are demanded, we should set the sign bit as
+      // demanded.
+      if (DemandedMask.countLeadingZeros() <= ShiftAmt)
+        DemandedMaskIn.set(BitWidth-1);
      if (SimplifyDemandedBits(I->getOperand(0),
                               DemandedMaskIn,
                               RHSKnownZero, RHSKnownOne, Depth+1))