fma3_available.c

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MIT License
-----------

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#ifdef TEST_STANDALONE
#include <stdio.h>
#pragma section (".CRT$XIC",long,read)
typedef void (__cdecl *_PIFV)(void);
#else
#include <sect_attribs.h>
#include <windows.h>
#include <cruntime.h>
#include <internal.h>
#endif

#define _CRTALLOC(x) __declspec(allocate(x))

int __fma3_is_available = 0;
int __use_fma3_lib = 0;


int __cdecl _set_FMA3_enable(int flag)
{
    if (__fma3_is_available) __use_fma3_lib = flag;
    return __use_fma3_lib;
}

int __fma3_lib_init(void);

_CRTALLOC(".CRT$XIC") static _PIFV init_fma3 = __fma3_lib_init;

int __fma3_lib_init(void)
{
    int CPUID[4]; // CPUID[2] is ECX;

    __fma3_is_available = 0;
    __cpuid(CPUID, 1);
    if (CPUID[2] & (1 << 12)) {
        __fma3_is_available = 1;
    }

    __use_fma3_lib = __fma3_is_available;
    return 0;
}