runtime: use unaligned loads on ppc64

benchmark                      old ns/op     new ns/op     delta
BenchmarkAlignedLoad-160       8.67          7.42          -14.42%
BenchmarkUnalignedLoad-160     8.63          7.37          -14.60%

Change-Id: Id4609d7b4038c4d2ec332efc4fe6f1adfb61b82b
Reviewed-on: https://go-review.googlesource.com/20812
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/export_test.go

@@ -193,3 +193,6 @@ func SetTracebackEnv(level string) {
 	setTraceback(level)
 	traceback_env = traceback_cache
 }
+
+var ReadUnaligned32 = readUnaligned32
+var ReadUnaligned64 = readUnaligned64

src/runtime/hash_test.go

@@ -11,6 +11,7 @@ import (
 	. "runtime"
 	"strings"
 	"testing"
+	"unsafe"
 )
 
 // Smhasher is a torture test for hash functions.
@@ -658,3 +659,24 @@ func TestStructHash(t *testing.T) {
 		t.Errorf("too many allocs %f - hash not balanced", n)
 	}
 }
+
+var sink uint64
+
+func BenchmarkAlignedLoad(b *testing.B) {
+	var buf [16]byte
+	p := unsafe.Pointer(&buf[0])
+	var s uint64
+	for i := 0; i < b.N; i++ {
+		s += ReadUnaligned64(p)
+	}
+	sink = s
+}
+func BenchmarkUnalignedLoad(b *testing.B) {
+	var buf [16]byte
+	p := unsafe.Pointer(&buf[1])
+	var s uint64
+	for i := 0; i < b.N; i++ {
+		s += ReadUnaligned64(p)
+	}
+	sink = s
+}

src/runtime/unaligned1.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build 386 amd64 amd64p32 arm64
+// +build 386 amd64 amd64p32 arm64 ppc64 ppc64le
 
 package runtime
 

src/runtime/unaligned2.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build arm ppc64 ppc64le mips64 mips64le
+// +build arm mips64 mips64le
 
 package runtime