1 files changed, 59 insertions, 1 deletions

diff --git a/libgo/go/internal/cpu/cpu_x86.go b/libgo/go/internal/cpu/cpu_x86.go
index eceeb44..62853a1 100644
--- a/libgo/go/internal/cpu/cpu_x86.go
+++ b/libgo/go/internal/cpu/cpu_x86.go
@@ -36,6 +36,8 @@ const (
 	cpuid_ADX  = 1 << 19
 )
 
+var maxExtendedFunctionInformation uint32
+
 func doinit() {
 	options = []option{
 		{Name: "adx", Feature: &X86.HasADX},
@@ -63,19 +65,30 @@ func doinit() {
 		return
 	}
 
+	maxExtendedFunctionInformation, _, _, _ = cpuid(0x80000000, 0)
+
 	_, _, ecx1, edx1 := cpuid(1, 0)
 	X86.HasSSE2 = isSet(edx1, cpuid_SSE2)
 
 	X86.HasSSE3 = isSet(ecx1, cpuid_SSE3)
 	X86.HasPCLMULQDQ = isSet(ecx1, cpuid_PCLMULQDQ)
 	X86.HasSSSE3 = isSet(ecx1, cpuid_SSSE3)
-	X86.HasFMA = isSet(ecx1, cpuid_FMA)
 	X86.HasSSE41 = isSet(ecx1, cpuid_SSE41)
 	X86.HasSSE42 = isSet(ecx1, cpuid_SSE42)
 	X86.HasPOPCNT = isSet(ecx1, cpuid_POPCNT)
 	X86.HasAES = isSet(ecx1, cpuid_AES)
+
+	// OSXSAVE can be false when using older Operating Systems
+	// or when explicitly disabled on newer Operating Systems by
+	// e.g. setting the xsavedisable boot option on Windows 10.
 	X86.HasOSXSAVE = isSet(ecx1, cpuid_OSXSAVE)
 
+	// The FMA instruction set extension only has VEX prefixed instructions.
+	// VEX prefixed instructions require OSXSAVE to be enabled.
+	// See Intel 64 and IA-32 Architecture Software Developer’s Manual Volume 2
+	// Section 2.4 "AVX and SSE Instruction Exception Specification"
+	X86.HasFMA = isSet(ecx1, cpuid_FMA) && X86.HasOSXSAVE
+
 	osSupportsAVX := false
 	// For XGETBV, OSXSAVE bit is required and sufficient.
 	if X86.HasOSXSAVE {
@@ -101,3 +114,48 @@ func doinit() {
 func isSet(hwc uint32, value uint32) bool {
 	return hwc&value != 0
 }
+
+// Name returns the CPU name given by the vendor.
+// If the CPU name can not be determined an
+// empty string is returned.
+func Name() string {
+	if maxExtendedFunctionInformation < 0x80000004 {
+		return ""
+	}
+
+	data := make([]byte, 0, 3*4*4)
+
+	var eax, ebx, ecx, edx uint32
+	eax, ebx, ecx, edx = cpuid(0x80000002, 0)
+	data = appendBytes(data, eax, ebx, ecx, edx)
+	eax, ebx, ecx, edx = cpuid(0x80000003, 0)
+	data = appendBytes(data, eax, ebx, ecx, edx)
+	eax, ebx, ecx, edx = cpuid(0x80000004, 0)
+	data = appendBytes(data, eax, ebx, ecx, edx)
+
+	// Trim leading spaces.
+	for len(data) > 0 && data[0] == ' ' {
+		data = data[1:]
+	}
+
+	// Trim tail after and including the first null byte.
+	for i, c := range data {
+		if c == '\x00' {
+			data = data[:i]
+			break
+		}
+	}
+
+	return string(data)
+}
+
+func appendBytes(b []byte, args ...uint32) []byte {
+	for _, arg := range args {
+		b = append(b,
+			byte((arg >> 0)),
+			byte((arg >> 8)),
+			byte((arg >> 16)),
+			byte((arg >> 24)))
+	}
+	return b
+}