On 24 March 2011 13:07, Mathias Gaunard <mathias.gaunard@ens-lyon.org> wrote:
On 24/03/2011 01:16, Gruenke, Matt wrote:
cpuid? It seems to me that the *only* thing that should determine how the program gets compiled is the compiler flags, since the target platform might have either less or more capability than the build machine. I've experienced both cases, firsthand.
GCC will define the following preprocessor macros, depending on which code generation flags you specify:
__MMX__ __SSE__ __SSE2__ __SSE3__ __SSSE3__ __SSE4A__ __SSE4_1__ __SSE4_2__ __AES__ __PCLMUL__ __AVX__
Alright, I just looked into how other compilers do it.
On GCC, SSEx built-ins are only available if the suitable -mssex option is set, which you can detect with __SSEx__. On MSVC, SSE built-ins are always available but may result in a runtime error. There are only the /arch:SSE and /arch:AVX option used to tell the compiler that it can generate SSE or AVX instructions automatically, there are no /arch:SSEx options.
Therefore there is no way to do the kind of thing you suggest with MSVC.
That's why I think the most sensible way to do it is to let the end user specify what he wants to use, and just do everything conditionnaly with ifdef's.