Quoting Sergii Romantsov (2018-10-29 01:44:28) > Hello, > > What problem are we solving? > > That we don't get fast paths in rounding.h by default on i686, I think? > > Yes, it adds optimization for rounding.h. On x86_64 msse is enabled by default > (as example by gcc). > And additionally helps to fix autotools 32b build (missed linkage with m-lib > if > no optimization). > > > This will make the code non-portable from an SSE capable system to a > non-sse > capable system. That's a pretty old system at this point (Pentium III and > Athlon > XP) > > As i found in gcc-docs (https://gcc.gnu.org/onlinedocs/gcc-4.5.3/gcc/ > i386-and-x86_002d64-Options.html) exactly mentioned systems are supports SSE. > But in the patch i'm checking if -msse supported by compiler. > If its incorrect than does it mean that compiler doesn't based on system > capabilities? And does it mean that adding option -msse4.1 is also enabled in > wrong way?
Right, the compiler can support instructions the "build" machine (computer running the compiler) can't run. Even for builds of the same architecture. No, the -msee4.1 case in src/mesa is different. We have a runtime check in libmesa that detects sse4.1 features at run time and loads the sse4.1 optimized functions if it can, or falls back to non-sse4.1 versions if it can't. > I'm cloning gcc to check how it supports 'sse' and if it based on system > capabilities. Also we may try to add some possibility to check > cpu-capabilities > (around cpuid). > But if we don't need such optimization, than it will be nice at least to fix > autotools 32b build (https://patchwork.freedesktop.org/patch/258659/) - i will > update patch just by linking -lm with mesautil. Yeah, I think we should land that if it fixes the build for 32bit x86. Dylan
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