[APInt] Add a isOneValue method that can determine if a number is 1 by only using getActiveBits/countLeadingZeros

Previously you would have to use operator==(uint64_t) which does the getActiveBits call and a uint64_t comparison. But we can get all we need to know from the getActiveBits call.

This method will be used in another commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304854 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed