M3:  "mmx3",
	M4:  "mmx4",
	M5:  "mmx5",
	M6:  "mmx6",
	M7:  "mmx7",
	X0:  "xmm0",
	X1:  "xmm1",
	X2:  "xmm2",
	X3:  "xmm3",
	X4:  "xmm4",
	X5:  "xmm5",
	X6:  "xmm6",
	X7:  "xmm7",
	X8:  "xmm8",
	X9:  "xmm9",
	X10: "xmm10",
	X11: "xmm11",
	X12: "xmm12",
	X13: "xmm13",
	X14: "xmm14",
	X15: "xmm15",

	// TODO: Maybe the constants are named wrong.
	SPB: "spl",
	BPB: "bpl",

	M3:   "%mm3",
	M4:   "%mm4",
	M5:   "%mm5",
	M6:   "%mm6",
	M7:   "%mm7",
	X0:   "%xmm0",
	X1:   "%xmm1",
	X2:   "%xmm2",
	X3:   "%xmm3",
	X4:   "%xmm4",
	X5:   "%xmm5",
	X6:   "%xmm6",
	X7:   "%xmm7",
	X8:   "%xmm8",
	X9:   "%xmm9",
	X10:  "%xmm10",
	X11:  "%xmm11",
	X12:  "%xmm12",
	X13:  "%xmm13",
	X14:  "%xmm14",
	X15:  "%xmm15",
	CS:   "%cs",
	SS:   "%ss",

		var index uint32
		Rd := x & (1<<5 - 1)
		imm5 := (x >> 16) & (1<<5 - 1)
		if imm5&1 == 1 {
			a = ArrangementB
			index = imm5 >> 1
		} else if imm5&2 == 2 {
			a = ArrangementH
			index = imm5 >> 2
		} else if imm5&4 == 4 {
			a = ArrangementS
			index = imm5 >> 3
		} else if imm5&8 == 8 {
			a = ArrangementD
			index = imm5 >> 4
		} else {
			return nil
		}

	// "VMOVQ r/m64, xmm1"/6E vs "VMOVQ xmm2/m64, xmm1"/7E with mem operand.
	VMOVQ (AX), X20           // 62e1fd086e20 or 62e1fe087e20
	VMOVQ 7(DX), X20          // 62e1fd086ea207000000 or 62e1fe087ea207000000
	VMOVQ -15(R11)(CX*1), X20 // 62c1fd086ea40bf1ffffff or 62c1fe087ea40bf1ffffff
	VMOVQ (SP)(AX*2), X20     // 62e1fd086e2444 or 62e1fe087e2444
	// "VMOVQ xmm1, r/m64"/7E vs "VMOVQ xmm1, xmm2/m64"/D6 with mem operand.

	xArgXmm          // arg xmm
	xArgXMM0         // arg <XMM0>
	xArgXmm1         // arg xmm1
	xArgXmm2         // arg xmm2
	xArgXmm2M128     // arg xmm2/m128
	xArgYmm2M256     // arg ymm2/m256
	xArgXmm2M16      // arg xmm2/m16
	xArgXmm2M32      // arg xmm2/m32
	xArgXmm2M64      // arg xmm2/m64
	xArgXmmM128      // arg xmm/m128
	xArgXmmM32       // arg xmm/m32
	xArgXmmM64       // arg xmm/m64

			c.checkindex(p, index, 15)
			Q = 1
			imm5 = 1
			imm5 |= index << 1
		case ARNG_2D:
			c.checkindex(p, index, 1)
			Q = 1
			imm5 = 8
			imm5 |= index << 4
		case ARNG_2S:
			c.checkindex(p, index, 3)
			Q = 0
			imm5 = 4
			imm5 |= index << 3
		case ARNG_4H:
			c.checkindex(p, index, 7)
			Q = 0
			imm5 = 2
			imm5 |= index << 2
		case ARNG_4S:

	{0x0ff00030, 0x06800010, 4, PKHBT_EQ, 0x6011c04, instArgs{arg_R_12, arg_R_16, arg_R_shift_imm}},               // PKH<BT,TB><c> <Rd>,<Rn>,<Rm>{,LSL #<imm5>} cond:4|0|1|1|0|1|0|0|0|Rn:4|Rd:4|imm5:5|tb|0|1|Rm:4

		"\n.\n.MOVBLZX.(.8.*.4.).(.R12.).,.AX.\n.ADDB.AX.,.DX.\n",
	},
	{
		"nested multiline macro",
		lines(
			"#define KEYROUND(xmm, load, off, r1, r2, index) \\",
			"\tMOVBLZX	(BP)(DX*4),	R8 \\",
			"\tload((off+1), r2) \\",
			"\tMOVB	R8,		(off*4)(R12) \\",
			"\tPINSRW	$index, (BP)(R8*4), xmm",
			"#define LOAD(off, reg) \\",
			"\tMOVBLZX	(off*4)(R12),	reg \\",
			"\tADDB	reg,		DX",
			"KEYROUND(X0, LOAD, 8, AX, BX, 0)",

eq:
	MOVB    $1, ret+8(FP)
	RET

// a in SI
// b in DI
// count in BX
// address of result byte in AX
TEXT memeqbody<>(SB),NOSPLIT,$0-0
	CMPL	BX, $4
	JB	small

	// 64 bytes at a time using xmm registers
hugeloop:
	CMPL	BX, $64
	JB	bigloop
#ifdef GO386_softfloat
	JMP	bigloop
#endif
	MOVOU	(SI), X0
	MOVOU	(DI), X1
	MOVOU	16(SI), X2
	MOVOU	16(DI), X3
	MOVOU	32(SI), X4
	MOVOU	32(DI), X5

	X86.HasRDRAND = isSet(30, ecx1)

	var osSupportsAVX, osSupportsAVX512 bool
	// For XGETBV, OSXSAVE bit is required and sufficient.
	if X86.HasOSXSAVE {
		eax, _ := xgetbv()
		// Check if XMM and YMM registers have OS support.
		osSupportsAVX = isSet(1, eax) && isSet(2, eax)

		if runtime.GOOS == "darwin" {
			// Darwin doesn't save/restore AVX-512 mask registers correctly across signal handlers.