AMANDV		R14, (R13), R12 // acb96238
	AMORW		R14, (R13), R12 // ac396338
	AMORV		R14, (R13), R12 // acb96338
	AMXORW		R14, (R13), R12 // ac396438
	AMXORV		R14, (R13), R12 // acb96438
	AMMAXW		R14, (R13), R12 // ac396538
	AMMAXV		R14, (R13), R12 // acb96538
	AMMINW		R14, (R13), R12 // ac396638
	AMMINV		R14, (R13), R12 // acb96638
	AMMAXWU		R14, (R13), R12 // ac396738
	AMMAXVU		R14, (R13), R12 // acb96738

	CSINV	HS, R1, R2, R3	// 232082da
	CSINVW	MI, R2, ZR, R2	// 42409f5a
	CINC	EQ, R4, R9	// 8914849a
	CINCW	PL, R2, ZR	// 5f44821a
	CINV	PL, R11, R22	// 76418bda
	CINVW	LS, R7, R13	// ed80875a
	CNEG	LS, R13, R7	// a7858dda
	CNEGW	EQ, R8, R13	// 0d15885a

// atomic ops
	LDARB	(R25), R2                            // 22ffdf08
	LDARH	(R5), R7                             // a7fcdf48

	VLD1	(R8)(R13), [V2.B16]                              // ERROR "illegal combination"
	VLD1	8(R9), [V2.B16]                                  // ERROR "illegal combination"
	VST1	[V1.B16], (R8)(R13)                              // ERROR "illegal combination"
	VST1	[V1.B16], 9(R2)                                  // ERROR "illegal combination"

	}
	register["LR"] = s390x.REG_LR
	// Pseudo-registers.
	register["SB"] = RSB
	register["FP"] = RFP
	register["PC"] = RPC
	// Avoid unintentionally clobbering g using R13.
	delete(register, "R13")
	register["g"] = s390x.REG_R13
	registerPrefix := map[string]bool{
		"AR": true,
		"F":  true,
		"R":  true,
	}

	instructions := make(map[string]obj.As)
	for i, s := range obj.Anames {

)

// Reads from a reader and rot13s the result.
type rot13Reader struct {
	r io.Reader
}

func newRot13Reader(r io.Reader) *rot13Reader {
	r13 := new(rot13Reader)
	r13.r = r
	return r13
}

func (r13 *rot13Reader) Read(p []byte) (int, error) {
	n, err := r13.r.Read(p)
	for i := 0; i < n; i++ {
		c := p[i] | 0x20 // lowercase byte
		if 'a' <= c && c <= 'm' {
			p[i] += 13
		} else if 'n' <= c && c <= 'z' {

The assembler uses them to hold temporary values when assembling some instructions.
</p>

<p>
<code>R13</code> points to the <code>g</code> (goroutine) structure.
This register must be referred to as <code>g</code>; the name <code>R13</code> is not recognized.
</p>

<p>
<code>R15</code> points to the stack frame and should typically only be accessed using the