Revert "runtime: improve memmove for amd64"

This reverts commit 3607c5f4f18ad4d423e40996ebf7f46b2f79ce02.

This was causing failures on amd64 machines without AVX.

Fixes #16939

Change-Id: I70080fbb4e7ae791857334f2bffd847d08cb25fa
Reviewed-on: https://go-review.googlesource.com/28274
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 0 insertions, 75 deletions

diff --git a/src/runtime/cpuflags_amd64.go b/src/runtime/cpuflags_amd64.go
deleted file mode 100644
index 277b42c4a0..0000000000
--- a/src/runtime/cpuflags_amd64.go
+++ /dev/null
@@ -1,75 +0,0 @@
-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package runtime
-
-var vendorStringBytes [12]byte
-var maxInputValue uint32
-var featureFlags uint32
-var processorVersionInfo uint32
-
-var useRepMovs bool
-
-func hasFeature(feature uint32) bool {
-	return (featureFlags & feature) != 0
-}
-
-func cpuid_low(arg1, arg2 uint32) (eax, ebx, ecx, edx uint32) // implemented in cpuidlow_amd64.s
-func xgetbv_low(arg1 uint32) (eax, edx uint32)                // implemented in cpuidlow_amd64.s
-
-func init() {
-	const cfOSXSAVE uint32 = 1 << 27
-	const cfAVX uint32 = 1 << 28
-
-	leaf0()
-	leaf1()
-
-	enabledAVX := false
-	// Let's check if OS has set CR4.OSXSAVE[bit 18]
-	// to enable XGETBV instruction.
-	if hasFeature(cfOSXSAVE) {
-		eax, _ := xgetbv_low(0)
-		// Let's check that XCR0[2:1] = ‘11b’
-		// i.e. XMM state and YMM state are enabled by OS.
-		enabledAVX = (eax & 0x6) == 0x6
-	}
-
-	isIntelBridgeFamily := (processorVersionInfo == 0x206A0 ||
-		processorVersionInfo == 0x206D0 ||
-		processorVersionInfo == 0x306A0 ||
-		processorVersionInfo == 0x306E0) &&
-		isIntel()
-
-	useRepMovs = !(hasFeature(cfAVX) && enabledAVX) || isIntelBridgeFamily
-}
-
-func leaf0() {
-	eax, ebx, ecx, edx := cpuid_low(0, 0)
-	maxInputValue = eax
-	int32ToBytes(ebx, vendorStringBytes[0:4])
-	int32ToBytes(edx, vendorStringBytes[4:8])
-	int32ToBytes(ecx, vendorStringBytes[8:12])
-}
-
-func leaf1() {
-	if maxInputValue < 1 {
-		return
-	}
-	eax, _, ecx, _ := cpuid_low(1, 0)
-	// Let's remove stepping and reserved fields
-	processorVersionInfo = eax & 0x0FFF3FF0
-	featureFlags = ecx
-}
-
-func int32ToBytes(arg uint32, buffer []byte) {
-	buffer[3] = byte(arg >> 24)
-	buffer[2] = byte(arg >> 16)
-	buffer[1] = byte(arg >> 8)
-	buffer[0] = byte(arg)
-}
-
-func isIntel() bool {
-	intelSignature := [12]byte{'G', 'e', 'n', 'u', 'i', 'n', 'e', 'I', 'n', 't', 'e', 'l'}
-	return vendorStringBytes == intelSignature
-}