Detect the availability of SSE/SSE2 instruction set in Visual Studio

Question

How can I check in code whether SSE/SSE2 is enabled or not by the Visual Studio compiler?

I have tried #ifdef __SSE__ but it didn't work.

Answer 1

From the documentation:

_M_IX86_FP

Expands to a value indicating which /arch compiler option was used:

• 0 if /arch:IA32 was used.
• 1 if /arch:SSE was used.
• 2 if /arch:SSE2 was used. This value is the default if /arch was not specified.

I don't see any mention of _SSE_.

Answer 2

Some additional information on _M_IX86_FP.

_M_IX86_FP is only defined for 32-bit code. 64-bit x86 code has at least SSE2. You can use _M_AMD64 or _M_X64 to determine if the code is 64-bit.

#ifdef __AVX2__
//AVX2
#elif defined ( __AVX__ )
//AVX
#elif (defined(_M_AMD64) || defined(_M_X64))
//SSE2 x64
#elif _M_IX86_FP == 2
//SSE2 x32
#elif _M_IX86_FP == 1
//SSE x32
#else
//nothing
#endif

Answer 3

The relevant preprocessor macros have two underscores at each end:

#ifdef __SSE__

#ifdef __SSE2__

#ifdef __SSE3__

#ifdef __SSE4_1__

#ifdef __AVX__

...etc...

UPDATE: apparently the above macros are not automatically pre-defined for you when using Visual Studio (even though they are in every other x86 compiler that I have ever used), so you may need to define them yourself if you want portability with gcc, clang, ICC, et al...

Answer 4

This is a late answer, but on MSDN you can find an article about __cpuid and __cpuidex. I redid the class into a function and it checks the support of MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1. https://docs.microsoft.com/en-us/cpp/intrinsics/cpuid-cpuidex?view=vs-2019

[[nodiscard]] bool CheckSimdSupport() noexcept
{
    std::array<int, 4> cpui;
    int nIds_{};
    std::bitset<32> f_1_ECX_{};
    std::bitset<32> f_1_EDX_{};
    std::vector<std::array<int, 4>> data_;

    __cpuid(cpui.data(), 0);
    nIds_ = cpui[0];

    for (int i = 0; i <= 1; ++i)
    {
        __cpuid(cpui.data(), i);
        data_.push_back(cpui);
    }

    if (nIds_ >= 1)
    {
        f_1_ECX_ = data_[1][2];
        f_1_EDX_ = data_[1][3];
    }
    // f_1_ECX_[0] - SSE3
    // f_1_ECX_[9] - SSSE3
    // f_1_ECX_[19] - SSE4.1
    // f_1_EDX_[23] - MMX
    // f_1_EDX_[25] - SSE
    // f_1_EDX_[26] - SSE2
    return f_1_ECX_[0] && f_1_ECX_[9] && f_1_ECX_[19] && f_1_EDX_[23] && f_1_EDX_[25] && f_1_EDX_[26];
}