fix a crash due to missing parens


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25363 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 6143e3c..2fcf919 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -748,7 +748,7 @@
             // This is a sign extend if the top bits are known zero.
             Constant *Mask = ConstantInt::getAllOnesValue(XorLHS->getType());
             Mask = ConstantExpr::getShl(Mask, 
-                           ConstantInt::get(Type::UByteTy, 64-TySizeBits-Size));
+                         ConstantInt::get(Type::UByteTy, 64-(TySizeBits-Size)));
             if (!MaskedValueIsZero(XorLHS, cast<ConstantInt>(Mask)))
               Size = 0;  // Not a sign ext, but can't be any others either.
             goto FoundSExt;