Sun, I think my choice of words contradict with the keywords used in the flags.
The main change here is enabling -OPT:roundoff=2 at -O3 instead of -OPT:roundoff=1. This change enables fast-math functions, aggressive loop nest optimizations, reassociation on floating point expressions and more aggressive round-off settings. These aggressive floating point optimizations improve performance when using the -O3 flag but may affect floating point accuracy. The use of -fp-accuracy=relaxed in addition to -O3 is recommended for cases which need more floating point accuracy. -fp-accuracy=relaxed automatically sets -OPT:roundoff=1. User may also use -OPT:roundoff=1. Please let me know if you have questions. Ram -----Original Message----- From: Sun Chan [mailto:sun.c...@gmail.com] Sent: Wednesday, April 27, 2011 5:02 PM To: Ramanarayanan, Ramshankar Cc: open64-devel@lists.sourceforge.net Subject: Re: [Open64-devel] code review request for update to O3 flag you are really saying that to get back previous behavior, one needs to -fp_accuracy=not_relaxed or something to that effect? I don't follow your message. Sun On Wed, Apr 27, 2011 at 6:37 PM, Ramanarayanan, Ramshankar <ramshankar.ramanaraya...@amd.com> wrote: > Could a gate keeper approve this patch? > > > > This update enhances performance of the compiled code on X8664 when using > the O3 flag. Improvements come mainly from relaxing the floating point > accuracy setting at O3. This enables a wide range of optimizations including > loop nest optimizations and associative redundancy elimination > optimizations. Given this change, users will need to use > -fp-accuracy=relaxed flag in addition to -O3 if they require the earlier > floating point precision. During subsequent tuning we found that the bad > reference bias heuristic affects the computed cache costs and leads to > incorrect choice of inner loops and is thus ignored. > > > > Following tests have been conducted with this change. > > > > 1: No compiler time failure for x86 build > > 2: SPEC CPU 2006 validated with AMD flags and with O3 flag > > 3: The gcc regression suite has no new failures on x86/Linux > > > > Best regards, > > Ram > > > > Ramshankar Ramanarayanan > > Member of Technical Staff > > Open Source Compiler Engineering > > Advanced Micro Devices, Bangalore > > > > > > ------------------------------------------------------------------------------ > WhatsUp Gold - Download Free Network Management Software > The most intuitive, comprehensive, and cost-effective network > management toolset available today. Delivers lowest initial > acquisition cost and overall TCO of any competing solution. > http://p.sf.net/sfu/whatsupgold-sd > _______________________________________________ > Open64-devel mailing list > Open64-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/open64-devel > > ------------------------------------------------------------------------------ WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd _______________________________________________ Open64-devel mailing list Open64-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/open64-devel
