From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,b4c0f0f8a3cf7068 X-Google-Attributes: gid103376,public From: Lieven Marchand Subject: Re: Hotspot. Dynamic compilers "better" than static one? Date: 1998/06/02 Message-ID: <6l6kke$1iu$1@xenon.inbe.net>#1/1 X-Deja-AN: 359538920 References: <6kocc1$d80@drn.newsguy.com> <6kpk0h$qmo$1@supernews.com> <35735C36.6ED7@atlas.otago.ac.nz> Organization: Only under extreme pressure! Newsgroups: comp.lang.ada Date: 1998-06-02T00:00:00+00:00 List-Id: "Dr Richard A. O'Keefe" writes: > Robert Dewar wrote: > <> > > > Actually fewer production compilers than you might imagine actually use > > this approach, though of course it has appeared in research compilers for > > a long time. > > Sun's C, Pascal, and Fortran compilers for SPARC do this. > Digital's compilers for the Alpha do this. The K&R C compiler for Ultrix already had profiling feedback about 10 years ago. > What may be of more interest is that I have seen profile-driven > feedback make a difference of 0-20%, with 0% actually being quite > common, and I've had better performance using gcc -O6 (without > feedback) on an Alpha than I've had from the Dec compiler _with_ > feedback. > I've never seen it made much difference however. > So profile-driven feedback HAS BEEN SHIPPING FOR SEVERAL YEARS > in production compilers from MIPS, Digital, and Sun, and that's > just the ones I've used. But it's only one technique, and not > always the most important. Has anybody done any studies on how to choose input for the trial runs you're going to feed back to the optimizer? There seems to be a silent assumption that "typical" input values are adequate and that the choice of input values won't make the performance worse on some other type of values. -- Lieven Marchand ------------------------------------------------------------------------------ Few people have a talent for constructive laziness. -- Lazarus Long Fascist news feed line fodder