func sbfx8(x int8) int64 {
	return int64(x >> 5) // arm64:"SBFX\t[$]5, R[0-9]+, [$]3"
}

// sbfx combinations.
// merge shifts with sbfiz into sbfx.
func sbfx9(x int32) int32 {
	return (x << 3) >> 4 // arm64:"SBFX\t[$]1, R[0-9]+, [$]28",-"LSL",-"ASR"
}

// merge sbfx and sign-extension into sbfx.
func sbfx10(x int32) int64 {
	c := x + 5
	return int64(c >> 20) // arm64"SBFX\t[$]20, R[0-9]+, [$]12",-"MOVW\tR[0-9]+, R[0-9]+"
}

	s0 = uint32(sbox0[t0>>24])<<24 | uint32(sbox0[t1>>16&0xff])<<16 | uint32(sbox0[t2>>8&0xff])<<8 | uint32(sbox0[t3&0xff])
	s1 = uint32(sbox0[t1>>24])<<24 | uint32(sbox0[t2>>16&0xff])<<16 | uint32(sbox0[t3>>8&0xff])<<8 | uint32(sbox0[t0&0xff])
	s2 = uint32(sbox0[t2>>24])<<24 | uint32(sbox0[t3>>16&0xff])<<16 | uint32(sbox0[t0>>8&0xff])<<8 | uint32(sbox0[t1&0xff])

	for i := 0; i < 256; i++ {
		if j := sbox0[sbox1[i]]; j != byte(i) {
			t.Errorf("sbox0[sbox1[%#x]] = %#x", i, j)
		}
		if j := sbox1[sbox0[i]]; j != byte(i) {
			t.Errorf("sbox1[sbox0[%#x]] = %#x", i, j)
		}
	}
}

// Test that encryption tables are correct.
// (Can adapt this code to generate them too.)
func TestTe(t *testing.T) {
	for i := 0; i < 256; i++ {
		s := uint32(sbox0[i])
		s2 := mul(s, 2)
		s3 := mul(s, 3)

	"REMW",
	"REV",
	"REV16",
	"REV16W",
	"REV32",
	"REVW",
	"ROR",
	"RORW",
	"SBC",
	"SBCS",
	"SBCSW",
	"SBCW",
	"SBFIZ",
	"SBFIZW",
	"SBFM",
	"SBFMW",
	"SBFX",
	"SBFXW",
	"SCVTFD",
	"SCVTFS",
	"SCVTFWD",
	"SCVTFWS",
	"SDIV",
	"SDIVW",
	"SEV",
	"SEVL",
	"SHA1C",
	"SHA1H",
	"SHA1M",
	"SHA1P",
	"SHA1SU0",
	"SHA1SU1",
	"SHA256H",

			break
		}
	}

	x = fx10()
	_ = x[9] // ERROR "nil check"
	if b {
		_ = x[9] // ERROR "nil check"
	} else {
		_ = x[9] // ERROR "nil check"
	}
	_ = x[9] // ERROR "nil check"

	x = fx10()
	if b {
		_ = x[9] // ERROR "nil check"
	} else {
		_ = &x[9] // ERROR "nil check"
	}
	_ = x[9] // ERROR "nil check"

	fx10()
	_ = x[9] // ERROR "nil check"

	x = fx10()

	0x04,
	0x08,
	0x10,
	0x20,
	0x40,
	0x80,
	0x1b,
	0x36,
	0x6c,
	0xd8,
	0xab,
	0x4d,
	0x9a,
	0x2f,
}

// FIPS-197 Figure 7. S-box substitution values in hexadecimal format.
var sbox0 = [256]byte{
	0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
	0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,

(MOVWreg (SBFX [bfc] x)) && bfc.getARM64BFwidth() <= 32 => (SBFX [bfc] x)
(MOVHreg (SBFX [bfc] x)) && bfc.getARM64BFwidth() <= 16 => (SBFX [bfc] x)
(MOVBreg (SBFX [bfc] x)) && bfc.getARM64BFwidth() <=  8 => (SBFX [bfc] x)

// sbfiz/sbfx combinations: merge shifts into bitfield ops
(SRAconst [sc] (SBFIZ [bfc] x)) && sc < bfc.getARM64BFlsb()
	=> (SBFIZ [armBFAuxInt(bfc.getARM64BFlsb()-sc, bfc.getARM64BFwidth())] x)

//
// - arg_immediate_bitmask_64_N_imms_immr:
//     a bitmask immediate for 64-bit variant and encoded in "N:imms:immr"
//
// - arg_immediate_SBFX_SBFM_64M_bitfield_width_64_imms:
//     an immediate for the <width> bitfield of SBFX 64-bit variant
//
// - arg_immediate_shift_32_implicit_inverse_imm16_hw:
//     a 32-bit immediate of the bitwise inverse of which can be encoded in "imm16:hw"
//
// - arg_cond_[Not]AllowALNV_[Invert|Normal]:

Examples:

	FMADDD F30, F20, F3, F29    <=>    fmadd d29, d3, d30, d20
	FNMSUBS F7, F25, F7, F22    <=>    fnmsub s22, s7, s7, s25

(4) BFI, BFXIL, SBFIZ, SBFX, UBFIZ, UBFX $<lsb>, <Rn>, $<width>, <Rd>

Examples:

	BFIW $16, R20, $6, R0      <=>    bfi w0, w20, #16, #6
	UBFIZ $34, R26, $5, R20    <=>    ubfiz x20, x26, #34, #5

	SADDL2:    "SADDL2",
	SADDLP:    "SADDLP",
	SADDLV:    "SADDLV",
	SADDW:     "SADDW",
	SADDW2:    "SADDW2",
	SBC:       "SBC",
	SBCS:      "SBCS",
	SBFIZ:     "SBFIZ",
	SBFM:      "SBFM",
	SBFX:      "SBFX",
	SCVTF:     "SCVTF",
	SDIV:      "SDIV",
	SEV:       "SEV",
	SEVL:      "SEVL",
	SHA1C:     "SHA1C",
	SHA1H:     "SHA1H",
	SHA1M:     "SHA1M",
	SHA1P:     "SHA1P",
	SHA1SU0:   "SHA1SU0",