}

		// While not recommended, it is valid to append to a shifted buffer.
		// This forces Write to copy the input.
		if rn.Intn(8) == 0 && cap(b) > 0 {
			b = b[1:1:cap(b)]
		}

		// Append a random integer of varying width.
		n := int64(rn.Intn(1 << rn.Intn(30)))
		want = append(strconv.AppendInt(want, n, 10), ' ')
		b = append(strconv.AppendInt(b, n, 10), ' ')
		w.Write(b)
	}
	w.Flush()

		{1, 9, "123456789", nil},
		{11, 10, "", io.EOF},
		{0, 0, "", nil},
		{-1, 0, "", "bytes.Reader.ReadAt: negative offset"},
	}
	for i, tt := range tests {
		b := make([]byte, tt.n)
		rn, err := r.ReadAt(b, tt.off)
		got := string(b[:rn])
		if got != tt.want {
			t.Errorf("%d. got %q; want %q", i, got, tt.want)
		}
		if fmt.Sprintf("%v", err) != fmt.Sprintf("%v", tt.wanterr) {

	VADDPD.RZ_SAE X3, X2, K1, X1     // ERROR "unsupported rounding"
	VADDPD.RN_SAE X3, X2, K1, X1     // ERROR "unsupported rounding"
	VADDPD.RU_SAE Y3, Y2, K1, Y1     // ERROR "unsupported rounding"
	VADDPD.RD_SAE Y3, Y2, K1, Y1     // ERROR "unsupported rounding"
	VADDPD.RZ_SAE Y3, Y2, K1, Y1     // ERROR "unsupported rounding"
	VADDPD.RN_SAE Y3, Y2, K1, Y1     // ERROR "unsupported rounding"
	// Unsupported SAE.

	VADDPD.RD_SAE Z3, Z2, K1, Z1   // 62f1ed3958cb
	VADDPD.RZ_SAE Z3, Z2, K1, Z1   // 62f1ed7958cb
	VADDPD.RN_SAE Z3, Z2, K1, Z1   // 62f1ed1958cb
	VADDPD.RU_SAE.Z Z3, Z2, K1, Z1 // 62f1edd958cb
	VADDPD.RD_SAE.Z Z3, Z2, K1, Z1 // 62f1edb958cb
	VADDPD.RZ_SAE.Z Z3, Z2, K1, Z1 // 62f1edf958cb
	VADDPD.RN_SAE.Z Z3, Z2, K1, Z1 // 62f1ed9958cb
	// EVEX: embedded broadcasting.
	VADDPD.BCST (AX), X2, K1, X1   // 62f1ed195808

		return
	}

	isIndex := false
	num := int16(0)
	isAmount := true // Amount is zero by default
	ext := ""
	if p.peek() == lex.LSH {
		// (Rn)(Rm<<2), the shifted offset register.
		ext = "LSL"
	} else {
		// (Rn)(Rm.UXTW<1), the extended offset register.
		// Rm.UXTW<<3, the extended register.
		p.get('.')
		tok := p.next()
		ext = tok.String()
	}
	if p.peek() == lex.LSH {

	CMP	$0x22220000, RSP                 // CMP $572653568, RSP   // 5b44a4d2ff633beb
	CMPW	$0x22220000, RSP                 // CMPW $572653568, RSP  // 5b44a452ff433b6b
	CCMN	MI, ZR, R1, $4	                 // e44341ba
	// MADD Rn,Rm,Ra,Rd
	MADD	R1, R2, R3, R4                   // 6408019b
	// CLS
	CLSW	R1, R2
	CLS	R1, R2
	SBC	$0, R1                           // 21001fda
	SBCW	$0, R1                           // 21001f5a