sync/atomic: use cas64 to implement {Load,Store,Add}{Uint,Int}64 on Linux/ARM

        Now with GOARM=5 our all.bash should pass on ARMv5 systems.
        Fixes #3331.

R=golang-dev, rsc, dvyukov
CC=golang-dev
https://golang.org/cl/6210071

src/pkg/sync/atomic/64bit_linux_arm.go

+// Copyright 2012 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 atomic
+
+func loadUint64(addr *uint64) (val uint64) {
+	for {
+		val = *addr
+		if CompareAndSwapUint64(addr, val, val) {
+			break
+		}
+	}
+	return
+}
+
+func storeUint64(addr *uint64, val uint64) {
+	for {
+		old := *addr
+		if CompareAndSwapUint64(addr, old, val) {
+			break
+		}
+	}
+	return
+}
+
+func addUint64(val *uint64, delta uint64) (new uint64) {
+	for {
+		old := *val
+		new = old + delta
+		if CompareAndSwapUint64(val, old, new) {
+			break
+		}
+	}
+	return
+}

src/pkg/sync/atomic/asm_linux_arm.s

@@ -121,20 +121,20 @@ TEXT setupAndCallCAS64<>(SB),7,$-4
 	MOVW	R1, armCAS64(SB)
 	MOVW	R1, PC
 
-TEXT ·CompareAndSwapInt64(SB),7,$-4
+TEXT ·CompareAndSwapInt64(SB),7,$0
+	B   	·CompareAndSwapUint64(SB)
+
+TEXT ·CompareAndSwapUint64(SB),7,$-4
 	MOVW	armCAS64(SB), R0
 	CMP 	$0, R0
 	MOVW.NE	R0, PC
 	B		setupAndCallCAS64<>(SB)
 
-TEXT ·CompareAndSwapUint64(SB),7,$0
-	B   	·CompareAndSwapInt64(SB)
-
 TEXT ·AddInt64(SB),7,$0
-	B	·armAddUint64(SB)
+	B	·addUint64(SB)
 
 TEXT ·AddUint64(SB),7,$0
-	B	·armAddUint64(SB)
+	B	·addUint64(SB)
 
 TEXT ·LoadInt32(SB),7,$0
 	B	·LoadUint32(SB)
@@ -150,10 +150,10 @@ loadloop1:
 	RET
 
 TEXT ·LoadInt64(SB),7,$0
-	B	·armLoadUint64(SB)
+	B	·loadUint64(SB)
 
 TEXT ·LoadUint64(SB),7,$0
-	B	·armLoadUint64(SB)
+	B	·loadUint64(SB)
 
 TEXT ·LoadUintptr(SB),7,$0
 	B	·LoadUint32(SB)
@@ -174,10 +174,10 @@ storeloop1:
 	RET
 
 TEXT ·StoreInt64(SB),7,$0
-	B	·armStoreUint64(SB)
+	B	·storeUint64(SB)
 
 TEXT ·StoreUint64(SB),7,$0
-	B	·armStoreUint64(SB)
+	B	·storeUint64(SB)
 
 TEXT ·StoreUintptr(SB),7,$0
 	B	·StoreUint32(SB)