90 lines
2.6 KiB
Plaintext
90 lines
2.6 KiB
Plaintext
SIMD predefs depend on compiler options. For example, you will have to add the
|
|
option `-msse3` to clang or gcc to enable SSE3. SIMD predefs are also inclusive.
|
|
This means that if SSE3 is enabled, then every other extensions with a lower
|
|
version number will implicitly be enabled and detected. However, some extensions
|
|
are CPU specific, they may not be detected nor enabled when an upper version is
|
|
enabled.
|
|
|
|
[note SSE(1) and SSE2 are automatically enabled by default when using x86-64
|
|
architecture.]
|
|
|
|
To check if any SIMD extension has been enabled, you can use:
|
|
|
|
``
|
|
#include <boost/predef/hardware/simd.h>
|
|
#include <iostream>
|
|
|
|
int main()
|
|
{
|
|
#if defined(BOOST_HW_SIMD_AVAILABLE)
|
|
std::cout << "SIMD detected!" << std::endl;
|
|
#endif
|
|
return 0;
|
|
}
|
|
``
|
|
|
|
When writing SIMD specific code, you may want to check if a particular extension
|
|
has been detected. To do so you have to use the right architecture predef and
|
|
compare it. Those predef are of the form `BOOST_HW_SIMD_"ARCH"` (where `"ARCH"`
|
|
is either `ARM`, `PPC`, or `X86`). For example, if you compile code for x86
|
|
architecture, you will have to use `BOOST_HW_SIMD_X86`. Its value will be the
|
|
version number of the most recent SIMD extension detected for the architecture.
|
|
|
|
To check if an extension has been enabled:
|
|
|
|
``
|
|
#include <boost/predef/hardware/simd.h>
|
|
#include <iostream>
|
|
|
|
int main()
|
|
{
|
|
#if BOOST_HW_SIMD_X86 >= BOOST_HW_SIMD_X86_SSE3_VERSION
|
|
std::cout << "This is SSE3!" << std::endl;
|
|
#endif
|
|
return 0;
|
|
}
|
|
``
|
|
|
|
[note The *_VERSION* defines that map version number to actual real
|
|
identifiers. This way it is easier to write comparisons without messing up with
|
|
version numbers.]
|
|
|
|
To *"stricly"* check the most recent detected extension:
|
|
|
|
``
|
|
#include <boost/predef/hardware/simd.h>
|
|
#include <iostream>
|
|
|
|
int main()
|
|
{
|
|
#if BOOST_HW_SIMD_X86 == BOOST_HW_SIMD_X86_SSE3_VERSION
|
|
std::cout << "This is SSE3 and this is the most recent enabled extension!"
|
|
<< std::endl;
|
|
#endif
|
|
return 0;
|
|
}
|
|
``
|
|
|
|
Because of the version systems of predefs and of the inclusive property of SIMD
|
|
extensions macros, you can easily check for ranges of supported extensions:
|
|
|
|
``
|
|
#include <boost/predef/hardware/simd.h>
|
|
#include <iostream>
|
|
|
|
int main()
|
|
{
|
|
#if BOOST_HW_SIMD_X86 >= BOOST_HW_SIMD_X86_SSE2_VERSION &&\
|
|
BOOST_HW_SIMD_X86 <= BOOST_HW_SIMD_X86_SSSE3_VERSION
|
|
std::cout << "This is SSE2, SSE3 and SSSE3!" << std::endl;
|
|
#endif
|
|
return 0;
|
|
}
|
|
``
|
|
|
|
[note Unlike gcc and clang, Visual Studio does not allow you to specify precisely
|
|
the SSE variants you want to use, the only detections that will take place are
|
|
SSE, SSE2, AVX and AVX2. For more informations,
|
|
see [@https://msdn.microsoft.com/en-us/library/b0084kay.aspx here].]
|
|
|