How to check if a CPU supports the SSE3 instruction set?

Question

Is the following code valid to check if a CPU supports the SSE3 instruction set?

Using the IsProcessorFeaturePresent() function apparently does not work on Windows XP.

bool CheckSSE3() {     int CPUInfo[4] = {-1};      //-- Get number of valid info ids     __cpuid(CPUInfo, 0);     int nIds = CPUInfo[0];      //-- Get info for id "1"     if (nIds >= 1)     {         __cpuid(CPUInfo, 1);         bool bSSE3NewInstructions = (CPUInfo[2] & 0x1) || false;         return bSSE3NewInstructions;          }      return false;       } 

Answer 1

I've created a GitHub repro that will detect CPU and OS support for all the major x86 ISA extensions: https://github.com/Mysticial/FeatureDetector

Here's a shorter version:

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First you need to access the CPUID instruction:

#ifdef _WIN32  //  Windows #define cpuid(info, x)    __cpuidex(info, x, 0)  #else  //  GCC Intrinsics #include <cpuid.h> void cpuid(int info[4], int InfoType){     __cpuid_count(InfoType, 0, info[0], info[1], info[2], info[3]); }  #endif 

Then you can run the following code:

//  Misc. bool HW_MMX; bool HW_x64; bool HW_ABM;      // Advanced Bit Manipulation bool HW_RDRAND; bool HW_BMI1; bool HW_BMI2; bool HW_ADX; bool HW_PREFETCHWT1;  //  SIMD: 128-bit bool HW_SSE; bool HW_SSE2; bool HW_SSE3; bool HW_SSSE3; bool HW_SSE41; bool HW_SSE42; bool HW_SSE4a; bool HW_AES; bool HW_SHA;  //  SIMD: 256-bit bool HW_AVX; bool HW_XOP; bool HW_FMA3; bool HW_FMA4; bool HW_AVX2;  //  SIMD: 512-bit bool HW_AVX512F;    //  AVX512 Foundation bool HW_AVX512CD;   //  AVX512 Conflict Detection bool HW_AVX512PF;   //  AVX512 Prefetch bool HW_AVX512ER;   //  AVX512 Exponential + Reciprocal bool HW_AVX512VL;   //  AVX512 Vector Length Extensions bool HW_AVX512BW;   //  AVX512 Byte + Word bool HW_AVX512DQ;   //  AVX512 Doubleword + Quadword bool HW_AVX512IFMA; //  AVX512 Integer 52-bit Fused Multiply-Add bool HW_AVX512VBMI; //  AVX512 Vector Byte Manipulation Instructions  int info[4]; cpuid(info, 0); int nIds = info[0];  cpuid(info, 0x80000000); unsigned nExIds = info[0];  //  Detect Features if (nIds >= 0x00000001){     cpuid(info,0x00000001);     HW_MMX    = (info[3] & ((int)1 << 23)) != 0;     HW_SSE    = (info[3] & ((int)1 << 25)) != 0;     HW_SSE2   = (info[3] & ((int)1 << 26)) != 0;     HW_SSE3   = (info[2] & ((int)1 <<  0)) != 0;      HW_SSSE3  = (info[2] & ((int)1 <<  9)) != 0;     HW_SSE41  = (info[2] & ((int)1 << 19)) != 0;     HW_SSE42  = (info[2] & ((int)1 << 20)) != 0;     HW_AES    = (info[2] & ((int)1 << 25)) != 0;      HW_AVX    = (info[2] & ((int)1 << 28)) != 0;     HW_FMA3   = (info[2] & ((int)1 << 12)) != 0;      HW_RDRAND = (info[2] & ((int)1 << 30)) != 0; } if (nIds >= 0x00000007){     cpuid(info,0x00000007);     HW_AVX2   = (info[1] & ((int)1 <<  5)) != 0;      HW_BMI1        = (info[1] & ((int)1 <<  3)) != 0;     HW_BMI2        = (info[1] & ((int)1 <<  8)) != 0;     HW_ADX         = (info[1] & ((int)1 << 19)) != 0;     HW_SHA         = (info[1] & ((int)1 << 29)) != 0;     HW_PREFETCHWT1 = (info[2] & ((int)1 <<  0)) != 0;      HW_AVX512F     = (info[1] & ((int)1 << 16)) != 0;     HW_AVX512CD    = (info[1] & ((int)1 << 28)) != 0;     HW_AVX512PF    = (info[1] & ((int)1 << 26)) != 0;     HW_AVX512ER    = (info[1] & ((int)1 << 27)) != 0;     HW_AVX512VL    = (info[1] & ((int)1 << 31)) != 0;     HW_AVX512BW    = (info[1] & ((int)1 << 30)) != 0;     HW_AVX512DQ    = (info[1] & ((int)1 << 17)) != 0;     HW_AVX512IFMA  = (info[1] & ((int)1 << 21)) != 0;     HW_AVX512VBMI  = (info[2] & ((int)1 <<  1)) != 0; } if (nExIds >= 0x80000001){     cpuid(info,0x80000001);     HW_x64   = (info[3] & ((int)1 << 29)) != 0;     HW_ABM   = (info[2] & ((int)1 <<  5)) != 0;     HW_SSE4a = (info[2] & ((int)1 <<  6)) != 0;     HW_FMA4  = (info[2] & ((int)1 << 16)) != 0;     HW_XOP   = (info[2] & ((int)1 << 11)) != 0; } 

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Note that this only detects whether the CPU supports the instructions. To actually run them, you also need to have operating system support.

Specifically, operating system support is required for:

• x64 instructions. (You need a 64-bit OS.)
• Instructions that use the (AVX) 256-bit ymm registers. See Andy Lutomirski's answer for how to detect this.
• Instructions that use the (AVX512) 512-bit zmm and mask registers. Detecting OS support for AVX512 is the same as with AVX, but using the flag 0xe6 instead of 0x6.

Answer 2

Mysticial's answer is a bit dangerous -- it explains how to detect CPU support but not OS support. You need to use _xgetbv to check whether the OS has enabled the required CPU extended state. See here for another source. Even gcc has made the same mistake. The meat of the code is:

bool avxSupported = false;  int cpuInfo[4]; __cpuid(cpuInfo, 1);  bool osUsesXSAVE_XRSTORE = cpuInfo[2] & (1 << 27) || false; bool cpuAVXSuport = cpuInfo[2] & (1 << 28) || false;  if (osUsesXSAVE_XRSTORE && cpuAVXSuport) {     unsigned long long xcrFeatureMask = _xgetbv(_XCR_XFEATURE_ENABLED_MASK);     avxSupported = (xcrFeatureMask & 0x6) == 0x6; }