Determine available features through CPUID

tz/cpuid_x86.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2009 The Go Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// +build 386 amd64 amd64p32
+
+package tz
+
+const (
+	bitOSXSAVE = 1 << 27
+	bitAVX     = 1 << 28
+	bitAVX2    = 1 << 5
+)
+
+func init() {
+	maxID, _, _, _ := cpuid(0, 0)
+	if maxID < 1 {
+		return
+	}
+
+	_, _, ecx1, _ := cpuid(1, 0)
+	hasOSXSAVE = isSet(ecx1, bitOSXSAVE)
+
+	osSupportsAVX := false
+	if hasOSXSAVE {
+		eax, _ := xgetbv()
+		osSupportsAVX = isSet(eax, 1<<1) && isSet(eax, 1<<2)
+	}
+
+	hasAVX = isSet(ecx1, bitAVX) && osSupportsAVX
+
+	if maxID < 7 {
+		return
+	}
+
+	_, ebx7, _, _ := cpuid(7, 0)
+	hasAVX2 = isSet(ebx7, bitAVX2) && osSupportsAVX
+}
+
+func isSet(hwc uint32, value uint32) bool {
+	return hwc&value != 0
+}
+
+func cpuid(eaxArg, ecxArg uint32) (eax, ebx, ecx, edx uint32)
+func xgetbv() (eax, edx uint32)

tz/cpuid_x86.s

@@ -0,0 +1,48 @@
+// Copyright (c) 2009 The Go Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "textflag.h"
+
+// func cpuid(eaxArg, ecxArg uint32) (eax, ebx, ecx, edx uint32)
+TEXT ·cpuid(SB), NOSPLIT, $0-24
+    MOVL eaxArg+0(FP), AX
+    MOVL ecxArg+4(FP), CX
+    CPUID
+    MOVL AX, eax+8(FP)
+    MOVL BX, ebx+12(FP)
+    MOVL CX, ecx+16(FP)
+    MOVL DX, edx+20(FP)
+    RET
+
+// func xgetbv() (eax, edx uint32)
+TEXT ·xgetbv(SB),NOSPLIT,$0-8
+    MOVL $0, CX
+    XGETBV
+    MOVL AX, eax+0(FP)
+    MOVL DX, edx+4(FP)
+    RET

tz/hash.go

@@ -21,6 +21,12 @@ const (
 	PureGo
 )
 
+var (
+	hasAVX     bool
+	hasAVX2    bool
+	hasOSXSAVE bool
+)
+
 func (impl Implementation) String() string {
 	switch impl {
 	case AVX:
@@ -53,7 +59,13 @@ func NewWith(impl Implementation) hash.Hash {
 
 // New returns a new hash.Hash computing the Tillich-Zémor checksum.
 func New() hash.Hash {
-	return newAVX2Inline()
+	if hasAVX2 {
+		return newAVX2Inline()
+	} else if hasAVX {
+		return newAVX()
+	} else {
+		return newPure()
+	}
 }
 
 // Sum returns Tillich-Zémor checksum of data.