static bool OSHasAVXSupport() {
  #if defined(__GNUC__)
    // Check xgetbv; this uses a .byte sequence instead of the instruction
    // directly because older assemblers do not include support for xgetbv and
    // there is no easy way to conditionally compile based on the assembler used.
    int rEAX, rEDX;
    __asm__ (".byte 0x0f, 0x01, 0xd0" : "=a" (rEAX), "=d" (rEDX) : "c" (0));
  #elif defined(_MSC_FULL_VER) && defined(_XCR_XFEATURE_ENABLED_MASK)
    unsigned long long rEAX = _xgetbv(_XCR_XFEATURE_ENABLED_MASK);
  #else
    int rEAX = 0; // Ensures we return false
  #endif
    return (rEAX & 6) == 6;
  }

// If CPUID indicates support for XSAVE, XRESTORE and AVX, and XGETBV 
// indicates that the AVX registers will be saved and restored on context
// switch, then we have full AVX support.
const unsigned AVXBits = (1 << 27) | (1 << 28);
bool HasAVX = ((ECX & AVXBits) == AVXBits) && OSHasAVXSupport();