These kinds of tricks actually are being done: by the compiler (as long as you give it enough information and don't try to outsmart it) - they're exactly what g

These kinds of tricks actually are being done: by the compiler (as long as you give it enough information and don't try to outsmart it) - they're exactly what gets put into optimization passes. Trying to do these optimizations by hand generally turns into a time sink that results in buggy, unmaintainable code, which is, pretty much by definition, too low level to take advantage of current or future compiler optimizations.