Avoid setting bits that aren't demanded.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47098 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 3ec60cde9d7cf909039830a945c21c4bd16982c5..e5ccd321756461c3a86252ff6293feb3d731f688 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1237,7 +1237,7 @@ void SelectionDAG::ComputeMaskedBits(SDOperand Op, const APInt &Mask,
       KnownZero = KnownZero.lshr(ShAmt);
       KnownOne  = KnownOne.lshr(ShAmt);
 
-      APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt);
+      APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt) & Mask;
       KnownZero |= HighBits;  // High bits known zero.
     }
     return;
@@ -1248,8 +1248,8 @@ void SelectionDAG::ComputeMaskedBits(SDOperand Op, const APInt &Mask,
       APInt InDemandedMask = (Mask << ShAmt);
       // If any of the demanded bits are produced by the sign extension, we also
       // demand the input sign bit.
-      APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt);
-      if (!!(HighBits & Mask))
+      APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt) & Mask;
+      if (HighBits.getBoolValue())
         InDemandedMask |= APInt::getSignBit(BitWidth);
       
       ComputeMaskedBits(Op.getOperand(0), InDemandedMask, KnownZero, KnownOne,