internal/cpu: Import back

1 files changed, 34 insertions, 0 deletions

diff --git a/internal/cpu/cpu_amd64.go b/internal/cpu/cpu_amd64.go
new file mode 100644
index 00000000..7fe59633
--- /dev/null
+++ b/internal/cpu/cpu_amd64.go
@@ -0,0 +1,34 @@
+//go:build amd64 && !purego
+
+package cpu
+
+const (
+	cpuidOSXSAVE = 1 << 27
+	cpuidAVX     = 1 << 28
+	cpuidAVX2    = 1 << 5
+)
+
+// cpuid is implemented in cpu_amd64.s.
+func cpuid(eaxArg, ecxArg uint32) (eax, ebx, ecx, edx uint32)
+
+// xgetbv with ecx = 0 is implemented in cpu_amd64.s.
+func xgetbv() (eax, edx uint32)
+
+func init() { //nolint:gochecknoinits
+	maxID, _, _, _ := cpuid(0, 0)
+	if maxID < 7 {
+		return
+	}
+
+	_, _, ecx1, _ := cpuid(1, 0)
+
+	osSupportsAVX := false
+
+	if ecx1&cpuidOSXSAVE != 0 {
+		eax, _ := xgetbv()
+		osSupportsAVX = eax&(1<<1) != 0 && eax&(1<<2) != 0
+	}
+
+	_, ebx7, _, _ := cpuid(7, 0)
+	X86.HasAVX2 = osSupportsAVX && ecx1&cpuidAVX != 0 && ebx7&cpuidAVX2 != 0
+}