[MathExtras] Fix UB in minIntN

We negated a value with a signed type which invited problems when that
value was the most negative signed number.  Use an unsigned type
for the value instead.  It will compute the same twos complement
result without the UB.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275815 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Support/MathExtras.h b/include/llvm/Support/MathExtras.h
index cf033e30aac37af81af05a0bfc1559ffcf6fbfdb..5c816ac9df922c887b0e28dd7025a8bdc9c09ef4 100644 (file)
--- a/include/llvm/Support/MathExtras.h
+++ b/include/llvm/Support/MathExtras.h
@@ -337,7 +337,7 @@ inline uint64_t maxUIntN(uint64_t N) {
 inline int64_t minIntN(int64_t N) {
   assert(N > 0 && N <= 64 && "integer width out of range");
 
-  return -(INT64_C(1)<<(N-1));
+  return -(UINT64_C(1)<<(N-1));
 }
 
 /// Gets the maximum value for a N-bit signed integer.