[ros-users] Question about cmake and SSE optimizations
Rosen Diankov
rosen.diankov at gmail.com
Tue Mar 23 17:03:17 UTC 2010
> 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.
exactly, that's why you have to check support for SSE by running a test program
rosen,
2010/3/24 Jose Gonzalez <de0a100 at gmail.com>:
> 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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