Re: [PATCH GIT 0.6] make use of register variables & size_t

Matthias-Christian Ott <matthias.christian@tiscali.de> wrote:

Register variables are outdated because they hinder the compiler from optimizing by taking away 1/7 of the usable registers on x86. Use six register variables and you're back to a accumulator-machine. Use -O2 or -Os instead, the compiler is smarter than you.

The regparm calling convention will change the load value -> store value on stack -> call sequence into load value -> call -> store if needed Obviously the second form can be better optimized than the first one. Therefore it's a gain instead of a loss.

If you really want to help the compiler, look for something like repeated pointer dereference or access to global variables and cache them in block- local variables (pointers, int and uint only, even for caching chars). Beware of volatile variables, and don't forget to look at the assembler code.