The problem with this kind of idiom recognition is that it must be conservative. That rules out lots of cases involving floating-point arithmetic and memory re

The problem with this kind of idiom recognition is that it must be conservative. That rules out lots of cases involving floating-point arithmetic and memory references. In the particular example of population count: this has been a hardware instruction on many processors since the early 60's. It is a crying shame that it's not part of the modern C language or standard library.