Avoiding gcc function prologue overhead?

Question

I\'ve lately encountered a lot of functions where gcc generates really bad code on x86. They all fit a pattern of:

if (some_condition) {
    /* do something real         


        

Answer 1

Perhaps upgrade your version of gcc? 4.6 has just been released. As far as I understand, it has the possibility of "partial inline". That is, an easily integratable outer part of a function is inlined and the expensive part is transformed into a call. But I have to admit that I didn't try it myself, yet.

Edit: The statement I was referring to from the ChangeLog:

Partial inlining is now supported and enabled by default at -O2 and greater. The feature can be controlled via -fpartial-inlining.

Partial inlining splits functions with short hot path to return. This allows more aggressive inlining of the hot path leading to better performance and often to code size reductions (because cold parts of functions are not duplicated).

...

Inlining when optimizing for size (either in cold regions of a program or when compiling with -Os) was improved to better handle C++ programs with larger abstraction penalty, leading to smaller and faster code.