On Sunday 30 November 2003 00:31, Ulrich Rhein wrote: > 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?
Nope and I don't plan to, but the performance gain is there nonetheless. Jason -- [EMAIL PROTECTED] mailing list
