[APInt] Remove unnecessary min with BitWidth from countTrailingOnesSlowCase.

The unused upper bits are guaranteed to be 0 so we don't need to worry about accidentally counting them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301091 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/APInt.cpp

@@ -688,7 +688,8 @@ unsigned APInt::countTrailingOnesSlowCase() const {
     Count += APINT_BITS_PER_WORD;
   if (i < getNumWords())
     Count += llvm::countTrailingOnes(pVal[i]);
-  return std::min(Count, BitWidth);
+  assert(Count <= BitWidth);
+  return Count;
 }
 
 unsigned APInt::countPopulationSlowCase() const {