For lshr by 0 bits, just return *this as a short cut. This also prevents
undefined behavior when the width > 64 bits.
llvm-svn: 37153
diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index 460cf55..2ed9b07 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -1149,6 +1149,12 @@
if (shiftAmt == BitWidth)
return APInt(BitWidth, 0);
+ // If none of the bits are shifted out, the result is *this. This avoids
+ // issues with shifting byt he size of the integer type, which produces
+ // undefined results in the code below. This is also an optimization.
+ if (shiftAmt == 0)
+ return *this;
+
// Create some space for the result.
uint64_t * val = new uint64_t[getNumWords()];