static void getAvailableFeatures()

in lib/LLVMSupport/Support/Host.cpp [933:1062]
113 lines of code
94 McCabe index (conditional complexity)

static void getAvailableFeatures(unsigned ECX, unsigned EDX, unsigned MaxLeaf,
                                 unsigned *FeaturesOut, unsigned *Features2Out,
                                 unsigned *Features3Out) {
  unsigned Features = 0;
  unsigned Features2 = 0;
  unsigned Features3 = 0;
  unsigned EAX, EBX;

  auto setFeature = [&](unsigned F) {
    if (F < 32)
      Features |= 1U << (F & 0x1f);
    else if (F < 64)
      Features2 |= 1U << ((F - 32) & 0x1f);
    else if (F < 96)
      Features3 |= 1U << ((F - 64) & 0x1f);
    else
      llvm_unreachable("Unexpected FeatureBit");
  };

  if ((EDX >> 15) & 1)
    setFeature(X86::FEATURE_CMOV);
  if ((EDX >> 23) & 1)
    setFeature(X86::FEATURE_MMX);
  if ((EDX >> 25) & 1)
    setFeature(X86::FEATURE_SSE);
  if ((EDX >> 26) & 1)
    setFeature(X86::FEATURE_SSE2);

  if ((ECX >> 0) & 1)
    setFeature(X86::FEATURE_SSE3);
  if ((ECX >> 1) & 1)
    setFeature(X86::FEATURE_PCLMUL);
  if ((ECX >> 9) & 1)
    setFeature(X86::FEATURE_SSSE3);
  if ((ECX >> 12) & 1)
    setFeature(X86::FEATURE_FMA);
  if ((ECX >> 19) & 1)
    setFeature(X86::FEATURE_SSE4_1);
  if ((ECX >> 20) & 1)
    setFeature(X86::FEATURE_SSE4_2);
  if ((ECX >> 23) & 1)
    setFeature(X86::FEATURE_POPCNT);
  if ((ECX >> 25) & 1)
    setFeature(X86::FEATURE_AES);

  if ((ECX >> 22) & 1)
    setFeature(X86::FEATURE_MOVBE);

  // 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) && !getX86XCR0(&EAX, &EDX) &&
                ((EAX & 0x6) == 0x6);
  bool HasAVX512Save = HasAVX && ((EAX & 0xe0) == 0xe0);

  if (HasAVX)
    setFeature(X86::FEATURE_AVX);

  bool HasLeaf7 =
      MaxLeaf >= 0x7 && !getX86CpuIDAndInfoEx(0x7, 0x0, &EAX, &EBX, &ECX, &EDX);

  if (HasLeaf7 && ((EBX >> 3) & 1))
    setFeature(X86::FEATURE_BMI);
  if (HasLeaf7 && ((EBX >> 5) & 1) && HasAVX)
    setFeature(X86::FEATURE_AVX2);
  if (HasLeaf7 && ((EBX >> 9) & 1))
    setFeature(X86::FEATURE_BMI2);
  if (HasLeaf7 && ((EBX >> 16) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512F);
  if (HasLeaf7 && ((EBX >> 17) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512DQ);
  if (HasLeaf7 && ((EBX >> 19) & 1))
    setFeature(X86::FEATURE_ADX);
  if (HasLeaf7 && ((EBX >> 21) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512IFMA);
  if (HasLeaf7 && ((EBX >> 23) & 1))
    setFeature(X86::FEATURE_CLFLUSHOPT);
  if (HasLeaf7 && ((EBX >> 26) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512PF);
  if (HasLeaf7 && ((EBX >> 27) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512ER);
  if (HasLeaf7 && ((EBX >> 28) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512CD);
  if (HasLeaf7 && ((EBX >> 29) & 1))
    setFeature(X86::FEATURE_SHA);
  if (HasLeaf7 && ((EBX >> 30) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512BW);
  if (HasLeaf7 && ((EBX >> 31) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512VL);

  if (HasLeaf7 && ((ECX >> 1) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512VBMI);
  if (HasLeaf7 && ((ECX >> 6) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512VBMI2);
  if (HasLeaf7 && ((ECX >> 8) & 1))
    setFeature(X86::FEATURE_GFNI);
  if (HasLeaf7 && ((ECX >> 10) & 1) && HasAVX)
    setFeature(X86::FEATURE_VPCLMULQDQ);
  if (HasLeaf7 && ((ECX >> 11) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512VNNI);
  if (HasLeaf7 && ((ECX >> 12) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512BITALG);
  if (HasLeaf7 && ((ECX >> 14) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX512VPOPCNTDQ);

  if (HasLeaf7 && ((EDX >> 2) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX5124VNNIW);
  if (HasLeaf7 && ((EDX >> 3) & 1) && HasAVX512Save)
    setFeature(X86::FEATURE_AVX5124FMAPS);

  unsigned MaxExtLevel;
  getX86CpuIDAndInfo(0x80000000, &MaxExtLevel, &EBX, &ECX, &EDX);

  bool HasExtLeaf1 = MaxExtLevel >= 0x80000001 &&
                     !getX86CpuIDAndInfo(0x80000001, &EAX, &EBX, &ECX, &EDX);
  if (HasExtLeaf1 && ((ECX >> 6) & 1))
    setFeature(X86::FEATURE_SSE4_A);
  if (HasExtLeaf1 && ((ECX >> 11) & 1))
    setFeature(X86::FEATURE_XOP);
  if (HasExtLeaf1 && ((ECX >> 16) & 1))
    setFeature(X86::FEATURE_FMA4);

  if (HasExtLeaf1 && ((EDX >> 29) & 1))
    setFeature(X86::FEATURE_EM64T);

  *FeaturesOut  = Features;
  *Features2Out = Features2;
  *Features3Out = Features3;
}