Briefly looked at it -- the trunk gcc also regresses a lot compared to the binary you attached. (To match your binary, also added -mfpmath=387 -m32 options)
Two problems: 1) more register spills in the trunk version -- the old compiler seems more effective in using fp stack registers; 2) the complex multiplication -- the old version emits inline sequence while the trunk version emits call to _muld3c intrinsinc. You can probably file a bug report on this. Thanks, David On Fri, Aug 27, 2010 at 8:39 AM, Corey Kasten <co...@materialintelligencellc.com> wrote: > On Fri, 2010-08-27 at 17:09 +0200, Richard Guenther wrote: >> On Fri, Aug 27, 2010 at 5:02 PM, Corey Kasten >> <co...@materialintelligencellc.com> wrote: >> > On Fri, 2010-08-27 at 06:50 -0700, Nathan Froyd wrote: >> >> On Fri, Aug 27, 2010 at 09:44:25AM -0400, Corey Kasten wrote: >> >> > I find that the executable compiled on system A runs faster (on both >> >> > systems) than the executable compiled on system B (on both system), by a >> >> > factor about approximately 4 times. I have attempted to play with the >> >> > GCC optimizer flags and have not been able to get System B (with the >> >> > later GCC version) to compile code with any better performance. Could >> >> > someone please help figure this out? >> >> >> >> It's almost impossible to tell what's going on without an actual >> >> testcase. You might not be able to provide the actual code, but you >> >> could try distilling it down to something you could release. >> >> >> >> -Nathan >> > >> > Thanks for the reply Nathan. >> > >> > I have attached an archive with the test case code. The code is built by >> > build.sh and outputs the number of microseconds to complete the >> > processing. >> > >> > Compiling with GCC version "4.1.2 20070925 (Red Hat 4.1.2-33)" produces >> > code that runs in about 66% of the time than does GCC version "4.3.0 >> > 20080428 (Red Hat 4.3.0-8)" >> >> -fcx-limited-range or -fcx-fortran-rules. 4.3 now is more conforming than >> 4.1. >> >> Richard. >> >> > Thanks >> > >> > Corey >> > > > Richard, > > -fcx-limited-range worked great on both my real benchmark and my test > achive. GCC didn't recognize -fcx-fortran-rules, but obviously I don't > need it. > > Thanks so much, > Corey > > > >
