[Mesa-dev] Mesa (master): mesa/x86: Support SSE 4.1 detection on x86-64.

[Matt Turner]

On Thu, May 22, 2014 at 12:30 PM, Jose Fonseca <jfonseca at vmware.com> wrote:
>
>
> ----- Original Message -----
>> Module: Mesa
>> Branch: master
>> Commit: 8b9302f2b4b0536abb91cb73682ec13640fe9eaf
>> URL:
>> https://urldefense.proofpoint.com/v1/url?u=http://cgit.freedesktop.org/mesa/mesa/commit/?id%3D8b9302f2b4b0536abb91cb73682ec13640fe9eaf&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=NMr9uy2iTjWVixC0wOcYCWEIYhfo80qKwRgdodpoDzA%3D%0A&m=AHdyjIRaIN8X%2FncnNP4l%2F2q0EVpdwrRXXlwYLuND8t0%3D%0A&s=ea1ec7f75f3ac94752601b896023c1f6f1d82af5cda565f7be3ea404c9b70866
>>
>> Author: Matt Turner <mattst88 at gmail.com>
>> Date:   Fri May  2 12:10:17 2014 -0700
>>
>> mesa/x86: Support SSE 4.1 detection on x86-64.
>>
>> Uses the cpuid.h header provided by gcc and clang. Other platforms are
>> encouraged to switch.
>>
>> ---
>>
>>  src/mesa/main/cpuinfo.c   |    2 +-
>>  src/mesa/main/cpuinfo.h   |    2 +-
>>  src/mesa/x86/common_x86.c |   11 +++++++++++
>>  3 files changed, 13 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/mesa/main/cpuinfo.c b/src/mesa/main/cpuinfo.c
>> index 8d482a6..73e295c 100644
>> --- a/src/mesa/main/cpuinfo.c
>> +++ b/src/mesa/main/cpuinfo.c
>> @@ -34,7 +34,7 @@
>>  void
>>  _mesa_get_cpu_features(void)
>>  {
>> -#ifdef USE_X86_ASM
>> +#if defined USE_X86_ASM || (defined __x86_64__ && !defined _MSC_VER)
>>     _mesa_get_x86_features();
>>  #endif
>
> This broke several build types because it assumes that assembly is always used on 64 bits except MSVC, which is not true.  Windows builds are not using assembly neither.
>
> I think that `(defined __x86_64__ && !defined _MSC_VER)` should be replaced with `defined USE_X86_64_ASM` . After all that's why we have the USE_*_ASM defines -- so that C code doesn't need to guess (and miserably) if/when assembly is being used.
>
> I'll draft a patch.
>
> Jose

Interesting. I was worried about breaking MSVC, since I don't think it
has a compatible cpuid.h header. We might consider renaming the
USE_*_ASM macros. The code I was enabling here is written using _mm_*
intrinsics, available on all x86 compilers as far as I'm aware, and
not assembly. The CPU feature detection code doesn't need any assembly
in Mesa either.