all: Use github.com/minio/sha256-simd

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3581

vendor/github.com/minio/sha256-simd/cpuid.go

@@ -0,0 +1,55 @@
+// Minio Cloud Storage, (C) 2016 Minio, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package sha256
+
+// True when SIMD instructions are available.
+var avx2 = haveAVX2()
+var avx = haveAVX()
+var ssse3 = haveSSSE3()
+var armSha = haveArmSha()
+
+// haveAVX returns true when there is AVX support
+func haveAVX() bool {
+	_, _, c, _ := cpuid(1)
+
+	// Check XGETBV, OXSAVE and AVX bits
+	if c&(1<<26) != 0 && c&(1<<27) != 0 && c&(1<<28) != 0 {
+		// Check for OS support
+		eax, _ := xgetbv(0)
+		return (eax & 0x6) == 0x6
+	}
+	return false
+}
+
+// haveAVX2 returns true when there is AVX2 support
+func haveAVX2() bool {
+	mfi, _, _, _ := cpuid(0)
+
+	// Check AVX2, AVX2 requires OS support, but BMI1/2 don't.
+	if mfi >= 7 && haveAVX() {
+		_, ebx, _, _ := cpuidex(7, 0)
+		return (ebx & 0x00000020) != 0
+	}
+	return false
+}
+
+// haveSSSE3 returns true when there is SSSE3 support
+func haveSSSE3() bool {
+
+	_, _, c, _ := cpuid(1)
+
+	return (c & 0x00000200) != 0
+}