Fix a bug in APIntified ComputeMaskedBits().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35022 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 9d327c7883d3614d958dd9309540a3fadc4fca3c..02336e59c4ccfa2e3ab3d0abeb4ee3fad00f8bb7 100644 (file)
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -675,11 +675,9 @@ static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
   case Instruction::ZExt:  {
     // Compute the bits in the result that are not present in the input.
     const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
-    APInt NotIn(~SrcTy->getMask());
-    APInt NewBits = APInt::getAllOnesValue(BitWidth) & 
-                    NotIn.zext(BitWidth);
+    APInt NewBits(APInt::getAllOnesValue(BitWidth).shl(SrcTy->getBitWidth()));
       
-    Mask &= ~NotIn;
+    Mask &= SrcTy->getMask().zext(BitWidth);
     ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
     assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 
     // The top bits are known to be zero.
@@ -689,11 +687,9 @@ static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
   case Instruction::SExt: {
     // Compute the bits in the result that are not present in the input.
     const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
-    APInt NotIn(~SrcTy->getMask());
-    APInt NewBits = APInt::getAllOnesValue(BitWidth) & 
-                    NotIn.zext(BitWidth);
+    APInt NewBits(APInt::getAllOnesValue(BitWidth).shl(SrcTy->getBitWidth()));
       
-    Mask &= ~NotIn;
+    Mask &= SrcTy->getMask().zext(BitWidth);
     ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
     assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");