[llvm] r273722 - [APInt] Don't shift into the sign bit

[David Majnemer via llvm-commits]

Author: majnemer
Date: Fri Jun 24 15:51:47 2016
New Revision: 273722

URL: http://llvm.org/viewvc/llvm-project?rev=273722&view=rev
Log:
[APInt] Don't shift into the sign bit

This fixes PR28294.

Modified:
    llvm/trunk/lib/Support/APInt.cpp

Modified: llvm/trunk/lib/Support/APInt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APInt.cpp?rev=273722&r1=273721&r2=273722&view=diff
==============================================================================
--- llvm/trunk/lib/Support/APInt.cpp (original)
+++ llvm/trunk/lib/Support/APInt.cpp Fri Jun 24 15:51:47 2016
@@ -555,8 +555,8 @@ bool APInt::ult(const APInt& RHS) const
 bool APInt::slt(const APInt& RHS) const {
   assert(BitWidth == RHS.BitWidth && "Bit widths must be same for comparison");
   if (isSingleWord()) {
-    int64_t lhsSext = (int64_t(VAL) << (64-BitWidth)) >> (64-BitWidth);
-    int64_t rhsSext = (int64_t(RHS.VAL) << (64-BitWidth)) >> (64-BitWidth);
+    int64_t lhsSext = SignExtend64(VAL, BitWidth);
+    int64_t rhsSext = SignExtend64(RHS.VAL, BitWidth);
     return lhsSext < rhsSext;
   }