(AtomicCompareAndSwap(32|64)Variant ...) => (LoweredAtomicCas(32|64)Variant      ...)

// Return old contents.
(AtomicAnd(64|32|8)            ...) => (LoweredAtomicAnd(64|32|8)            ...)
(AtomicOr(64|32|8)             ...) => (LoweredAtomicOr(64|32|8)             ...)
(AtomicAnd(64|32|8)Variant     ...) => (LoweredAtomicAnd(64|32|8)Variant     ...)
(AtomicOr(64|32|8)Variant      ...) => (LoweredAtomicOr(64|32|8)Variant      ...)

// Write barrier.

	v_2 := v.Args[2]
	v_1 := v.Args[1]
	v_0 := v.Args[0]
	b := v.Block
	config := b.Func.Config
	typ := &b.Func.Config.Types
	// match: (AtomicAnd8 ptr val mem)
	// cond: !config.BigEndian