[llvm] r249951 - In isUIntN, make sure N is less than 64 before using in a shift to avoid undefined behavior. Also change it to use the same formula as the template version which I think results in less math in compiled code.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Sat Oct 10 13:54:26 2015
New Revision: 249951

URL: http://llvm.org/viewvc/llvm-project?rev=249951&view=rev
Log:
In isUIntN, make sure N is less than 64 before using in a shift to avoid undefined behavior. Also change it to use the same formula as the template version which I think results in less math in compiled code.

Modified:
    llvm/trunk/include/llvm/Support/MathExtras.h

Modified: llvm/trunk/include/llvm/Support/MathExtras.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/MathExtras.h?rev=249951&r1=249950&r2=249951&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/MathExtras.h (original)
+++ llvm/trunk/include/llvm/Support/MathExtras.h Sat Oct 10 13:54:26 2015
@@ -313,7 +313,7 @@ inline bool isShiftedUInt(uint64_t x) {
 /// isUIntN - Checks if an unsigned integer fits into the given (dynamic)
 /// bit width.
 inline bool isUIntN(unsigned N, uint64_t x) {
-  return x == (x & (~0ULL >> (64 - N)));
+  return N >= 64 || x < (UINT64_C(1)<<(N));
 }
 
 /// isIntN - Checks if an signed integer fits into the given (dynamic)