//	*ptr = new;
//	return old;
TEXT ·Xchg(SB), NOSPLIT, $0-20
	MOVD	ptr+0(FP), R0
	MOVW	new+8(FP), R1
#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

		default:
			args = append(args, "-D", "GOARM_5")
		}
	}

	if cfg.Goarch == "arm64" {
		g, err := buildcfg.ParseGoarm64(cfg.GOARM64)
		if err == nil && g.LSE {
			args = append(args, "-D", "GOARM64_LSE")
		}
	}

	return args
}

func (gcToolchain) asm(b *Builder, a *Action, sfiles []string) ([]string, error) {
	p := a.Package
	args := asmArgs(a, p)

	var ofiles []string