#ifndef GOARM64_LSE
	MOVBU	internal∕cpu·ARM64+const_offsetARM64HasATOMICS(SB), R4
	CBZ 	R4, load_store_loop
#endif
	SWPALW	R1, (R0), R2
	MOVW	R2, ret+16(FP)
	RET
#ifndef GOARM64_LSE
load_store_loop:
	LDAXRW	(R0), R2
	STLXRW	R1, (R0), R3
	CBNZ	R3, load_store_loop
	MOVW	R2, ret+16(FP)
	RET
#endif

// uint64 Xchg64(ptr *uint64, new uint64)
// Atomically:
//	old := *ptr;
//	*ptr = new;