On 11/07/2014 06:09 AM, Siavash Eliasi wrote: > > On 11/07/2014 03:14 PM, Steven Newbury wrote: >> On Thu, 2014-11-06 at 21:00 -0800, Matt Turner wrote: >>> On Thu, Nov 6, 2014 at 8:56 PM, Siavash Eliasi < >>> siavashser...@gmail.com> wrote: >>>> Then I do recommend removing the "if (cpu_has_sse4_1)" from this >>>> patch and similar places, because there is no runtime CPU >>>> dispatching happening for SSE optimized code paths in action and >>>> just adds extra overhead (unnecessary branches) to the generated >>>> code. >>> No. Sorry, I realize I misread your previous question: >>> >>>>> I guess checking for "cpu_has_sse4_1" is unnecessary if it isn't >>>>> controllable by user at runtime; because "USE_SSE41" is a >>>>> compile time check and requires the target machine to be SSE 4.1 >>>>> capable already. >>> USE_SSE41 is set if the *compiler* supports SSE 4.1. This allows you >>> to build the code and then use it only on systems that actually >>> support it. >>> >>> All of this could have been pretty easily answered by a few greps >>> though... >> I wonder what difference it would make to have an option to compile >> out the run-time check code to avoid the additional overhead in cases >> where the builder *knows* at compile time what the run-time system is? >> (ie Gentoo) > I think that's possible. Since "cpu_has_sse4_1" and friends are simply > macros, one can set them to "true" or "1" during compile time if it's > going to be built for an SSE 4.1 capable target so your smart compiler > will totally get rid of the unnecessary runtime check. > > I guess "common_x86_features.h" should be modified to something like this: > > #ifdef __SSE4_1__ > #define cpu_has_sse4_1 1 > #else > #define cpu_has_sse4_1 (_mesa_x86_cpu_features & X86_FEATURE_SSE4_1) > #endif
I was thinking about doing something similar for cpu_has_xmm and cpu_has_xmm2 for x64. SSE and SSE2 are required parts of that instruction set, so they're always there. > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/mesa-dev > _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
