Add another variant of this test which found a place where

CodeGen's ComputeMaskedBits was being over-conservative when computing
bits for an ADD.

llvm-svn: 101963

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 13f69c4e817..5031170946d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1917,7 +1917,8 @@ void SelectionDAG::ComputeMaskedBits(SDValue Op, const APInt &Mask,
     // Output known-0 bits are known if clear or set in both the low clear bits
     // common to both LHS & RHS.  For example, 8+(X<<3) is known to have the
     // low 3 bits clear.
-    APInt Mask2 = APInt::getLowBitsSet(BitWidth, Mask.countTrailingOnes());
+    APInt Mask2 = APInt::getLowBitsSet(BitWidth,
+                                       BitWidth - Mask.countLeadingZeros());
     ComputeMaskedBits(Op.getOperand(0), Mask2, KnownZero2, KnownOne2, Depth+1);
     assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
     unsigned KnownZeroOut = KnownZero2.countTrailingOnes();