[ros-users] Question about cmake and SSE optimizations

[Jose Gonzalez]

Thanks for the feedback again!

I'll try it. My only fear with check_cxx_compiler_flag was that I
guess having the flag available in the compiler doesn't necessarily
means your processor supports it.


On Tue, Mar 23, 2010 at 12:56 PM, Rosen Diankov <rosen.diankov at gmail.com> wrote:
> i'm pasting cmake code i use for sse checks. it checks for both sse1
> and sse2, although similar checks can be used for sse3-5, there's also
> a check for msvc
>
> # check for SSE extensions
> include(CheckCXXSourceRuns)
> if( CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX )
>  set(SSE_FLAGS)
>
>  set(CMAKE_REQUIRED_FLAGS "-msse2")
>  check_cxx_source_runs("
>    #include <emmintrin.h>
>
>    int main()
>    {
>        __m128d a, b;
>        double vals[2] = {0};
>        a = _mm_loadu_pd(vals);
>        b = _mm_add_pd(a,a);
>        _mm_storeu_pd(vals,b);
>        return 0;
>     }"
>     HAS_SSE2_EXTENSIONS)
>
>  set(CMAKE_REQUIRED_FLAGS "-msse")
>  check_cxx_source_runs("
>    #include <xmmintrin.h>
>    int main()
>    {
>        __m128 a, b;
>        float vals[4] = {0};
>        a = _mm_loadu_ps(vals);
>        b = a;
>        b = _mm_add_ps(a,b);
>        _mm_storeu_ps(vals,b);
>        return 0;
>    }"
>    HAS_SSE_EXTENSIONS)
>
>  set(CMAKE_REQUIRED_FLAGS)
>
>  if(HAS_SSE2_EXTENSIONS)
>    message(STATUS "Using SSE2 extensions")
>    set(SSE_FLAGS "-msse2 -mfpmath=sse")
>  elseif(HAS_SSE_EXTENSIONS)
>    message(STATUS "Using SSE extensions")
>    set(SSE_FLAGS "-msse -mfpmath=sse")
>  endif()
>
>  add_definitions(${SSE_FLAGS})
> elseif(MSVC)
>  check_cxx_source_runs("
>    #include <emmintrin.h>
>
>    int main()
>    {
>        __m128d a, b;
>        double vals[2] = {0};
>        a = _mm_loadu_pd(vals);
>        b = _mm_add_pd(a,a);
>        _mm_storeu_pd(vals,b);
>        return 0;
>     }"
>     HAS_SSE2_EXTENSIONS)
>  if( HAS_SSE2_EXTENSIONS )
>    message(STATUS "Using SSE2 extensions")
>    add_definitions( "/arch:SSE2 /fp:fast -D__SSE__ -D__SSE2__" )
>  endif()
> endif()
>
>
>
>
>
> 2010/3/24 Jose Gonzalez <de0a100 at gmail.com>:
>> Thanks for the comments?
>>
>> What about  check_cxx_compiler_flag("-msse2" COMPILER_SUPPORT_SSE2)?
>> Have you ever tried it?
>>
>> On Tue, Mar 23, 2010 at 12:16 PM, Radu Bogdan Rusu
>> <rusu at willowgarage.com> wrote:
>>> Depending on what compiler and cpu you use, some of these flags might be already turned on by default. You can check
>>> that using:
>>>
>>> $ gcc -Q -O3 --help=target
>>>
>>> for example.
>>>
>>> Other than that, we don't have a proper way to enable/disable different SSE optimizations for now. Most ROS packages
>>> cram a add_definitions ("-msse... etc") in their CMakeLists.txt.
>>>
>>> Patches to make this more standard across multiple platforms and enable/disable SSE1-5 automatically would be great!
>>>
>>> Cheers,
>>> Radu.
>>>
>>> Jose Gonzalez wrote:
>>>> Hi,
>>>>
>>>> Doing some experiments in the past with OpenCV (linux/g++) I realized
>>>> that there is a significant performance difference between the
>>>> versions compiled with autoconf and cmake. Digging in the compilation
>>>> scripts I came to the conclusion that the only extra flags that were
>>>> added by the autoconf scripts were the SSE optimizations (and openMP).
>>>>
>>>> Talking about the SSE optimizations, I can see how ROS sets the flags
>>>> in a similar way. When the detected platform is i686, all the SSE
>>>> optimizations are disabled by default (there is a comment "SSE/SSE2
>>>> might probably be not available for some old AMD or VIA processors").
>>>> Before finding out a solution by myself I'd like to ask the list if
>>>> somebody knows a standard way of testing for SSE optimizations in
>>>> cmake.
>>>>
>>>> Thanks,
>>>> Jose
>>>>
>>>> ------------------------------------------------------------------------------
>>>> Download Intel® Parallel Studio Eval
>>>> Try the new software tools for yourself. Speed compiling, find bugs
>>>> proactively, and fine-tune applications for parallel performance.
>>>> See why Intel Parallel Studio got high marks during beta.
>>>> http://p.sf.net/sfu/intel-sw-dev
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>>>
>>> --
>>> | Radu Bogdan Rusu | http://rbrusu.com/
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