Hi, Am Samstag, 29. November 2003 16:31 schrieb Ulrich Rhein: > 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.
Shure? Compiling and timing one small program is no test. > > Benchmarks give a 30% improvement across the board and > > I must say there definately is a very noticable improvement to system > > responsiveness. > > Entirely unrealistic. Arguments? 30% is very optimistic, but I notice speed improvements too. > > 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. So you tested it with one of your own programs and say we are telling shit? I had my whole system compiled without this flag, then the only change was adding it (and of course I recompiled my system). There was a noticable performance boost. The desktop is much more responsive, not only in my imagination. > Could you point out some pieces of code where gcc does such an > optimization? No need for this. Just use google to get the answer. > Gruß Uli Grüße vom Michael -- [EMAIL PROTECTED] mailing list
