Jason Stubbs <[EMAIL PROTECTED]> writes: > On Saturday 29 November 2003 22:25, Ulrich Rhein wrote: >> Jason Stubbs <[EMAIL PROTECTED]> writes: >> > The biggest improvement in performance will come by adding >> > -fomit-frame-pointer to your flags. >> That won't actually change anything but remove three instructions from >> some function calls. The resulting performance improvement is >> practically insignificant. > WTF? Have you tried it?
Yes. > Benchmarks give a 30% improvement across the board and > I must say there definately is a very noticable improvement to system > responsiveness. Entirely unrealistic. > It may only remove three instructions from some function > calls, but it frees up a register or two allowing for better optimisation in > other ways. On x86, it's exactly one register (namely %ebp). I have tried it with gcc -S -O2 on a small project (~1.600 SLOC) of mine. In the functions in which %ebp is not used as frame pointer, it is not used at all. Could you point out some pieces of code where gcc does such an optimization? Gruß Uli -- "Or have we eaten on the insane root, that takes the reason prisoner?" -- MacBeth I, 3 -- [EMAIL PROTECTED] mailing list
