sync/atomic: add s390x implementations of atomic functions

Load and store instructions are atomic on s390x.

Change-Id: I33c641a75954f4fbd301b11a467cb57872038880
Reviewed-on: https://go-review.googlesource.com/20947Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/sync/atomic/asm_s390x.s

+// Copyright 2016 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.
+
+#include "textflag.h"
+
+TEXT ·SwapInt32(SB),NOSPLIT,$0-20
+	BR	·SwapUint32(SB)
+
+TEXT ·SwapUint32(SB),NOSPLIT,$0-20
+	MOVD	addr+0(FP), R3
+	MOVWZ	new+8(FP), R4
+	MOVWZ	(R3), R5
+repeat:
+	CS	R5, R4, (R3) // if (R3)==R5 then (R3)=R4 else R5=(R3)
+	BNE	repeat
+	MOVW	R5, old+16(FP)
+	RET
+
+TEXT ·SwapInt64(SB),NOSPLIT,$0-24
+	BR	·SwapUint64(SB)
+
+TEXT ·SwapUint64(SB),NOSPLIT,$0-24
+	MOVD	addr+0(FP), R3
+	MOVD	new+8(FP), R4
+	MOVD	(R3), R5
+repeat:
+	CSG	R5, R4, (R3) // if (R3)==R5 then (R3)=R4 else R5=(R3)
+	BNE	repeat
+	MOVD	R5, old+16(FP)
+	RET
+
+TEXT ·SwapUintptr(SB),NOSPLIT,$0-24
+	BR	·SwapUint64(SB)
+
+TEXT ·CompareAndSwapInt32(SB),NOSPLIT,$0-17
+	BR	·CompareAndSwapUint32(SB)
+
+TEXT ·CompareAndSwapUint32(SB),NOSPLIT,$0-17
+	MOVD	ptr+0(FP), R3
+	MOVWZ	old+8(FP), R4
+	MOVWZ	new+12(FP), R5
+	CS	R4, R5, 0(R3) // if R4==(R3) then (R3)=R5 else R4=(R3)
+	BNE	cas_fail
+	MOVB	$1, ret+16(FP)
+	RET
+cas_fail:
+	MOVB	$0, ret+16(FP)
+	RET
+
+TEXT ·CompareAndSwapUintptr(SB),NOSPLIT,$0-25
+	BR	·CompareAndSwapUint64(SB)
+
+TEXT ·CompareAndSwapInt64(SB),NOSPLIT,$0-25
+	BR	·CompareAndSwapUint64(SB)
+
+TEXT ·CompareAndSwapUint64(SB),NOSPLIT,$0-25
+	MOVD	ptr+0(FP), R3
+	MOVD	old+8(FP), R4
+	MOVD	new+16(FP), R5
+	CSG	R4, R5, 0(R3) // if R4==(R3) then (R3)=R5 else R4=(R3)
+	BNE	cas64_fail
+	MOVB	$1, ret+24(FP)
+	RET
+cas64_fail:
+	MOVB	$0, ret+24(FP)
+	RET
+
+TEXT ·AddInt32(SB),NOSPLIT,$0-20
+	BR	·AddUint32(SB)
+
+TEXT ·AddUint32(SB),NOSPLIT,$0-20
+	MOVD	ptr+0(FP), R4
+	MOVWZ	delta+8(FP), R5
+	MOVWZ	(R4), R3
+repeat:
+	ADD	R3, R5, R6
+	CS	R3, R6, (R4) // if R3==(R4) then (R4)=R6 else R3=(R4)
+	BNE	repeat
+	MOVW	R6, ret+16(FP)
+	RET
+
+TEXT ·AddUintptr(SB),NOSPLIT,$0-24
+	BR	·AddUint64(SB)
+
+TEXT ·AddInt64(SB),NOSPLIT,$0-24
+	BR	·AddUint64(SB)
+
+TEXT ·AddUint64(SB),NOSPLIT,$0-24
+	MOVD	ptr+0(FP), R4
+	MOVD	delta+8(FP), R5
+	MOVD	(R4), R3
+repeat:
+	ADD	R3, R5, R6
+	CSG	R3, R6, (R4) // if R3==(R4) then (R4)=R6 else R3=(R4)
+	BNE	repeat
+	MOVD	R6, ret+16(FP)
+	RET
+
+TEXT ·LoadInt32(SB),NOSPLIT,$0-12
+	BR	·LoadUint32(SB)
+
+TEXT ·LoadUint32(SB),NOSPLIT,$0-12
+	MOVD	addr+0(FP), R3
+	MOVW	0(R3), R4
+	MOVW	R4, val+8(FP)
+	RET
+
+TEXT ·LoadInt64(SB),NOSPLIT,$0-16
+	BR	·LoadUint64(SB)
+
+TEXT ·LoadUint64(SB),NOSPLIT,$0-16
+	MOVD	addr+0(FP), R3
+	MOVD	0(R3), R4
+	MOVD	R4, val+8(FP)
+	RET
+
+TEXT ·LoadUintptr(SB),NOSPLIT,$0-16
+	BR	·LoadPointer(SB)
+
+TEXT ·LoadPointer(SB),NOSPLIT,$0-16
+	BR	·LoadUint64(SB)
+
+TEXT ·StoreInt32(SB),NOSPLIT,$0-12
+	BR	·StoreUint32(SB)
+
+TEXT ·StoreUint32(SB),NOSPLIT,$0-12
+	MOVD	ptr+0(FP), R3
+	MOVW	val+8(FP), R4
+	MOVW	R4, 0(R3)
+	RET
+
+TEXT ·StoreInt64(SB),NOSPLIT,$0-16
+	BR	·StoreUint64(SB)
+
+TEXT ·StoreUint64(SB),NOSPLIT,$0-16
+	MOVD	addr+0(FP), R3
+	MOVD	val+8(FP), R4
+	MOVD	R4, 0(R3)
+	RET
+
+TEXT ·StoreUintptr(SB),NOSPLIT,$0-16
+	BR	·StoreUint64(SB)