func archInit()

in cpu/cpu_x86.go [60:141]
64 lines of code
13 McCabe index (conditional complexity)

func archInit() {

	Initialized = true

	maxID, _, _, _ := cpuid(0, 0)

	if maxID < 1 {
		return
	}

	_, _, ecx1, edx1 := cpuid(1, 0)
	X86.HasSSE2 = isSet(26, edx1)

	X86.HasSSE3 = isSet(0, ecx1)
	X86.HasPCLMULQDQ = isSet(1, ecx1)
	X86.HasSSSE3 = isSet(9, ecx1)
	X86.HasFMA = isSet(12, ecx1)
	X86.HasCX16 = isSet(13, ecx1)
	X86.HasSSE41 = isSet(19, ecx1)
	X86.HasSSE42 = isSet(20, ecx1)
	X86.HasPOPCNT = isSet(23, ecx1)
	X86.HasAES = isSet(25, ecx1)
	X86.HasOSXSAVE = isSet(27, ecx1)
	X86.HasRDRAND = isSet(30, ecx1)

	var osSupportsAVX, osSupportsAVX512 bool
	// For XGETBV, OSXSAVE bit is required and sufficient.
	if X86.HasOSXSAVE {
		eax, _ := xgetbv()
		// Check if XMM and YMM registers have OS support.
		osSupportsAVX = isSet(1, eax) && isSet(2, eax)

		if runtime.GOOS == "darwin" {
			// Darwin doesn't save/restore AVX-512 mask registers correctly across signal handlers.
			// Since users can't rely on mask register contents, let's not advertise AVX-512 support.
			// See issue 49233.
			osSupportsAVX512 = false
		} else {
			// Check if OPMASK and ZMM registers have OS support.
			osSupportsAVX512 = osSupportsAVX && isSet(5, eax) && isSet(6, eax) && isSet(7, eax)
		}
	}

	X86.HasAVX = isSet(28, ecx1) && osSupportsAVX

	if maxID < 7 {
		return
	}

	_, ebx7, ecx7, edx7 := cpuid(7, 0)
	X86.HasBMI1 = isSet(3, ebx7)
	X86.HasAVX2 = isSet(5, ebx7) && osSupportsAVX
	X86.HasBMI2 = isSet(8, ebx7)
	X86.HasERMS = isSet(9, ebx7)
	X86.HasRDSEED = isSet(18, ebx7)
	X86.HasADX = isSet(19, ebx7)

	X86.HasAVX512 = isSet(16, ebx7) && osSupportsAVX512 // Because avx-512 foundation is the core required extension
	if X86.HasAVX512 {
		X86.HasAVX512F = true
		X86.HasAVX512CD = isSet(28, ebx7)
		X86.HasAVX512ER = isSet(27, ebx7)
		X86.HasAVX512PF = isSet(26, ebx7)
		X86.HasAVX512VL = isSet(31, ebx7)
		X86.HasAVX512BW = isSet(30, ebx7)
		X86.HasAVX512DQ = isSet(17, ebx7)
		X86.HasAVX512IFMA = isSet(21, ebx7)
		X86.HasAVX512VBMI = isSet(1, ecx7)
		X86.HasAVX5124VNNIW = isSet(2, edx7)
		X86.HasAVX5124FMAPS = isSet(3, edx7)
		X86.HasAVX512VPOPCNTDQ = isSet(14, ecx7)
		X86.HasAVX512VPCLMULQDQ = isSet(10, ecx7)
		X86.HasAVX512VNNI = isSet(11, ecx7)
		X86.HasAVX512GFNI = isSet(8, ecx7)
		X86.HasAVX512VAES = isSet(9, ecx7)
		X86.HasAVX512VBMI2 = isSet(6, ecx7)
		X86.HasAVX512BITALG = isSet(12, ecx7)

		eax71, _, _, _ := cpuid(7, 1)
		X86.HasAVX512BF16 = isSet(5, eax71)
	}
}