// Copyright 2014 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package x86asm implements decoding of x86 machine code.
package x86asm

import (
	"bytes"
	"fmt"
)

// An Inst is a single instruction.
type Inst struct {
	Prefix   Prefixes // Prefixes applied to the instruction.
	Op       Op       // Opcode mnemonic
	Opcode   uint32   // Encoded opcode bits, left aligned (first byte is Opcode>>24, etc)
	Args     Args     // Instruction arguments, in Intel order
	Mode     int      // processor mode in bits: 16, 32, or 64
	AddrSize int      // address size in bits: 16, 32, or 64
	DataSize int      // operand size in bits: 16, 32, or 64
	MemBytes int      // size of memory argument in bytes: 1, 2, 4, 8, 16, and so on.
	Len      int      // length of encoded instruction in bytes
	PCRel    int      // length of PC-relative address in instruction encoding
	PCRelOff int      // index of start of PC-relative address in instruction encoding
	// AVX-512 flags
	Broadcast bool // EVEX broadcast
	Zeroing   bool // EVEX zeroing
	SAE       bool // Suppress All Exceptions
	Rounding  int8 // Rounding control (0-3), valid only when SAE is true
}

// Prefixes is an array of prefixes associated with a single instruction.
// The prefixes are listed in the same order as found in the instruction:
// each prefix byte corresponds to one slot in the array. The first zero
// in the array marks the end of the prefixes.
type Prefixes [14]Prefix

// A Prefix represents an Intel instruction prefix.
// The low 8 bits are the actual prefix byte encoding,
// and the top 8 bits contain distinguishing bits and metadata.
type Prefix uint16

const (
	// Metadata about the role of a prefix in an instruction.
	PrefixImplicit Prefix = 0x8000 // prefix is implied by instruction text
	PrefixIgnored  Prefix = 0x4000 // prefix is ignored: either irrelevant or overridden by a later prefix
	PrefixInvalid  Prefix = 0x2000 // prefix makes entire instruction invalid (bad LOCK)

	// Memory segment overrides.
	PrefixES Prefix = 0x26 // ES segment override
	PrefixCS Prefix = 0x2E // CS segment override
	PrefixSS Prefix = 0x36 // SS segment override
	PrefixDS Prefix = 0x3E // DS segment override
	PrefixFS Prefix = 0x64 // FS segment override
	PrefixGS Prefix = 0x65 // GS segment override

	// Branch prediction.
	PrefixPN Prefix = 0x12E // predict not taken (conditional branch only)
	PrefixPT Prefix = 0x13E // predict taken (conditional branch only)

	// Size attributes.
	PrefixDataSize Prefix = 0x66 // operand size override
	PrefixData16   Prefix = 0x166
	PrefixData32   Prefix = 0x266
	PrefixAddrSize Prefix = 0x67 // address size override
	PrefixAddr16   Prefix = 0x167
	PrefixAddr32   Prefix = 0x267

	// One of a kind.
	PrefixLOCK     Prefix = 0xF0 // lock
	PrefixREPN     Prefix = 0xF2 // repeat not zero
	PrefixXACQUIRE Prefix = 0x1F2
	PrefixBND      Prefix = 0x2F2
	PrefixREP      Prefix = 0xF3 // repeat
	PrefixXRELEASE Prefix = 0x1F3

	// The REX prefixes must be in the range [PrefixREX, PrefixREX+0x10).
	// the other bits are set or not according to the intended use.
	PrefixREX       Prefix = 0x40 // REX 64-bit extension prefix
	PrefixREXW      Prefix = 0x08 // extension bit W (64-bit instruction width)
	PrefixREXR      Prefix = 0x04 // extension bit R (r field in modrm)
	PrefixREXX      Prefix = 0x02 // extension bit X (index field in sib)
	PrefixREXB      Prefix = 0x01 // extension bit B (r/m field in modrm or base field in sib)
	PrefixVEX2Bytes Prefix = 0xC5 // Short form of vex prefix
	PrefixVEX3Bytes Prefix = 0xC4 // Long form of vex prefix
	PrefixEVEX      Prefix = 0x62 // EVEX prefix
)

// IsREX reports whether p is a REX prefix byte.
func (p Prefix) IsREX() bool {
	return p&0xF0 == PrefixREX
}

func (p Prefix) IsVEX() bool {
	return p&0xFF == PrefixVEX2Bytes || p&0xFF == PrefixVEX3Bytes
}

func (p Prefix) IsEVEX() bool {
	return p&0xFF == PrefixEVEX
}

func (p Prefix) String() string {
	p &^= PrefixImplicit | PrefixIgnored | PrefixInvalid
	if s := prefixNames[p]; s != "" {
		return s
	}

	if p.IsREX() {
		s := "REX."
		if p&PrefixREXW != 0 {
			s += "W"
		}
		if p&PrefixREXR != 0 {
			s += "R"
		}
		if p&PrefixREXX != 0 {
			s += "X"
		}
		if p&PrefixREXB != 0 {
			s += "B"
		}
		return s
	}

	return fmt.Sprintf("Prefix(%#x)", int(p))
}

// An Op is an x86 opcode.
type Op uint32

func (op Op) String() string {
	i := int(op)
	if i < 0 || i >= len(opNames) || opNames[i] == "" {
		if i < len(avxOpNames) && avxOpNames[i] != "" {
			return avxOpNames[i]
		}
		return fmt.Sprintf("Op(%d)", i)
	}
	return opNames[i]
}

// An Args holds the instruction arguments.
// If an instruction has fewer than 4 arguments,
// the final elements in the array are nil.
type Args [6]Arg

// An Arg is a single instruction argument,
// one of these types: Reg, Mem, Imm, Rel.
type Arg interface {
	String() string
	isArg()
}

// Note that the implements of Arg that follow are all sized
// so that on a 64-bit machine the data can be inlined in
// the interface value instead of requiring an allocation.

// A Reg is a single register.
// The zero Reg value has no name but indicates “no register.”
type Reg uint8

const (
	_ Reg = iota

	// 8-bit
	AL
	CL
	DL
	BL
	AH
	CH
	DH
	BH
	SPB
	BPB
	SIB
	DIB
	R8B
	R9B
	R10B
	R11B
	R12B
	R13B
	R14B
	R15B

	// 16-bit
	AX
	CX
	DX
	BX
	SP
	BP
	SI
	DI
	R8W
	R9W
	R10W
	R11W
	R12W
	R13W
	R14W
	R15W

	// 32-bit
	EAX
	ECX
	EDX
	EBX
	ESP
	EBP
	ESI
	EDI
	R8L
	R9L
	R10L
	R11L
	R12L
	R13L
	R14L
	R15L

	// 64-bit
	RAX
	RCX
	RDX
	RBX
	RSP
	RBP
	RSI
	RDI
	R8
	R9
	R10
	R11
	R12
	R13
	R14
	R15

	// Instruction pointer.
	IP  // 16-bit
	EIP // 32-bit
	RIP // 64-bit

	// 387 floating point registers.
	F0
	F1
	F2
	F3
	F4
	F5
	F6
	F7

	// MMX registers.
	M0
	M1
	M2
	M3
	M4
	M5
	M6
	M7

	// XMM registers.
	X0
	X1
	X2
	X3
	X4
	X5
	X6
	X7
	X8
	X9
	X10
	X11
	X12
	X13
	X14
	X15
	X16
	X17
	X18
	X19
	X20
	X21
	X22
	X23
	X24
	X25
	X26
	X27
	X28
	X29
	X30
	X31

	// YMM registers.
	Y0
	Y1
	Y2
	Y3
	Y4
	Y5
	Y6
	Y7
	Y8
	Y9
	Y10
	Y11
	Y12
	Y13
	Y14
	Y15
	Y16
	Y17
	Y18
	Y19
	Y20
	Y21
	Y22
	Y23
	Y24
	Y25
	Y26
	Y27
	Y28
	Y29
	Y30
	Y31

	// ZMM registers.
	Z0
	Z1
	Z2
	Z3
	Z4
	Z5
	Z6
	Z7
	Z8
	Z9
	Z10
	Z11
	Z12
	Z13
	Z14
	Z15
	Z16
	Z17
	Z18
	Z19
	Z20
	Z21
	Z22
	Z23
	Z24
	Z25
	Z26
	Z27
	Z28
	Z29
	Z30
	Z31

	// Mask registers.
	K0
	K1
	K2
	K3
	K4
	K5
	K6
	K7

	// Segment registers.
	ES
	CS
	SS
	DS
	FS
	GS

	// System registers.
	GDTR
	IDTR
	LDTR
	MSW
	TASK

	// Control registers.
	CR0
	CR1
	CR2
	CR3
	CR4
	CR5
	CR6
	CR7
	CR8
	CR9
	CR10
	CR11
	CR12
	CR13
	CR14
	CR15

	// Debug registers.
	DR0
	DR1
	DR2
	DR3
	DR4
	DR5
	DR6
	DR7
	DR8
	DR9
	DR10
	DR11
	DR12
	DR13
	DR14
	DR15

	// Task registers.
	TR0
	TR1
	TR2
	TR3
	TR4
	TR5
	TR6
	TR7
)

const regMax = TR7

func (Reg) isArg() {}

func (r Reg) String() string {
	i := int(r)
	if i < 0 || i >= len(regNames) || regNames[i] == "" {
		return fmt.Sprintf("Reg(%d)", i)
	}
	return regNames[i]
}

// A Mem is a memory reference.
// The general form is Segment:[Base+Scale*Index+Disp].
type Mem struct {
	Segment Reg
	Base    Reg
	Scale   uint8
	Index   Reg
	Disp    int64
}

func (Mem) isArg() {}

func (m Mem) String() string {
	var base, plus, scale, index, disp string

	if m.Base != 0 {
		base = m.Base.String()
	}
	if m.Scale != 0 {
		if m.Base != 0 {
			plus = "+"
		}
		if m.Scale > 1 {
			scale = fmt.Sprintf("%d*", m.Scale)
		}
		index = m.Index.String()
	}
	if m.Disp != 0 || m.Base == 0 && m.Scale == 0 {
		disp = fmt.Sprintf("%+#x", m.Disp)
	}
	return "[" + base + plus + scale + index + disp + "]"
}

// A Rel is an offset relative to the current instruction pointer.
type Rel int32

func (Rel) isArg() {}

func (r Rel) String() string {
	return fmt.Sprintf(".%+d", r)
}

// An Imm is an integer constant.
type Imm int64

func (Imm) isArg() {}

func (i Imm) String() string {
	return fmt.Sprintf("%#x", int64(i))
}

func (i Inst) String() string {
	var buf bytes.Buffer
	for _, p := range i.Prefix {
		if p == 0 {
			break
		}
		if p&PrefixImplicit != 0 {
			continue
		}
		fmt.Fprintf(&buf, "%v ", p)
	}
	fmt.Fprintf(&buf, "%v", i.Op)
	sep := " "
	for _, v := range i.Args {
		if v == nil {
			break
		}
		fmt.Fprintf(&buf, "%s%v", sep, v)
		sep = ", "
	}
	return buf.String()
}

func isReg(a Arg) bool {
	_, ok := a.(Reg)
	return ok
}

func isSegReg(a Arg) bool {
	r, ok := a.(Reg)
	return ok && ES <= r && r <= GS
}

func isMem(a Arg) bool {
	_, ok := a.(Mem)
	return ok
}

func isImm(a Arg) bool {
	_, ok := a.(Imm)
	return ok
}

func regBytes(a Arg) int {
	r, ok := a.(Reg)
	if !ok {
		return 0
	}
	if AL <= r && r <= R15B {
		return 1
	}
	if AX <= r && r <= R15W {
		return 2
	}
	if EAX <= r && r <= R15L {
		return 4
	}
	if RAX <= r && r <= R15 {
		return 8
	}
	return 0
}

func isSegment(p Prefix) bool {
	switch p {
	case PrefixCS, PrefixDS, PrefixES, PrefixFS, PrefixGS, PrefixSS:
		return true
	}
	return false
}

// The Op definitions and string list are in tables.go.

var prefixNames = map[Prefix]string{
	PrefixCS:       "CS",
	PrefixDS:       "DS",
	PrefixES:       "ES",
	PrefixFS:       "FS",
	PrefixGS:       "GS",
	PrefixSS:       "SS",
	PrefixLOCK:     "LOCK",
	PrefixREP:      "REP",
	PrefixREPN:     "REPN",
	PrefixAddrSize: "ADDRSIZE",
	PrefixDataSize: "DATASIZE",
	PrefixAddr16:   "ADDR16",
	PrefixData16:   "DATA16",
	PrefixAddr32:   "ADDR32",
	PrefixData32:   "DATA32",
	PrefixBND:      "BND",
	PrefixXACQUIRE: "XACQUIRE",
	PrefixXRELEASE: "XRELEASE",
	PrefixREX:      "REX",
	PrefixPT:       "PT",
	PrefixPN:       "PN",
}

var regNames = [...]string{
	AL:   "AL",
	CL:   "CL",
	BL:   "BL",
	DL:   "DL",
	AH:   "AH",
	CH:   "CH",
	BH:   "BH",
	DH:   "DH",
	SPB:  "SPB",
	BPB:  "BPB",
	SIB:  "SIB",
	DIB:  "DIB",
	R8B:  "R8B",
	R9B:  "R9B",
	R10B: "R10B",
	R11B: "R11B",
	R12B: "R12B",
	R13B: "R13B",
	R14B: "R14B",
	R15B: "R15B",
	AX:   "AX",
	CX:   "CX",
	BX:   "BX",
	DX:   "DX",
	SP:   "SP",
	BP:   "BP",
	SI:   "SI",
	DI:   "DI",
	R8W:  "R8W",
	R9W:  "R9W",
	R10W: "R10W",
	R11W: "R11W",
	R12W: "R12W",
	R13W: "R13W",
	R14W: "R14W",
	R15W: "R15W",
	EAX:  "EAX",
	ECX:  "ECX",
	EDX:  "EDX",
	EBX:  "EBX",
	ESP:  "ESP",
	EBP:  "EBP",
	ESI:  "ESI",
	EDI:  "EDI",
	R8L:  "R8L",
	R9L:  "R9L",
	R10L: "R10L",
	R11L: "R11L",
	R12L: "R12L",
	R13L: "R13L",
	R14L: "R14L",
	R15L: "R15L",
	RAX:  "RAX",
	RCX:  "RCX",
	RDX:  "RDX",
	RBX:  "RBX",
	RSP:  "RSP",
	RBP:  "RBP",
	RSI:  "RSI",
	RDI:  "RDI",
	R8:   "R8",
	R9:   "R9",
	R10:  "R10",
	R11:  "R11",
	R12:  "R12",
	R13:  "R13",
	R14:  "R14",
	R15:  "R15",
	IP:   "IP",
	EIP:  "EIP",
	RIP:  "RIP",
	F0:   "F0",
	F1:   "F1",
	F2:   "F2",
	F3:   "F3",
	F4:   "F4",
	F5:   "F5",
	F6:   "F6",
	F7:   "F7",
	M0:   "M0",
	M1:   "M1",
	M2:   "M2",
	M3:   "M3",
	M4:   "M4",
	M5:   "M5",
	M6:   "M6",
	M7:   "M7",
	X0:   "X0",
	X1:   "X1",
	X2:   "X2",
	X3:   "X3",
	X4:   "X4",
	X5:   "X5",
	X6:   "X6",
	X7:   "X7",
	X8:   "X8",
	X9:   "X9",
	X10:  "X10",
	X11:  "X11",
	X12:  "X12",
	X13:  "X13",
	X14:  "X14",
	X15:  "X15",
	X16:  "X16",
	X17:  "X17",
	X18:  "X18",
	X19:  "X19",
	X20:  "X20",
	X21:  "X21",
	X22:  "X22",
	X23:  "X23",
	X24:  "X24",
	X25:  "X25",
	X26:  "X26",
	X27:  "X27",
	X28:  "X28",
	X29:  "X29",
	X30:  "X30",
	X31:  "X31",
	Y0:   "Y0",
	Y1:   "Y1",
	Y2:   "Y2",
	Y3:   "Y3",
	Y4:   "Y4",
	Y5:   "Y5",
	Y6:   "Y6",
	Y7:   "Y7",
	Y8:   "Y8",
	Y9:   "Y9",
	Y10:  "Y10",
	Y11:  "Y11",
	Y12:  "Y12",
	Y13:  "Y13",
	Y14:  "Y14",
	Y15:  "Y15",
	Y16:  "Y16",
	Y17:  "Y17",
	Y18:  "Y18",
	Y19:  "Y19",
	Y20:  "Y20",
	Y21:  "Y21",
	Y22:  "Y22",
	Y23:  "Y23",
	Y24:  "Y24",
	Y25:  "Y25",
	Y26:  "Y26",
	Y27:  "Y27",
	Y28:  "Y28",
	Y29:  "Y29",
	Y30:  "Y30",
	Y31:  "Y31",
	Z0:   "Z0",
	Z1:   "Z1",
	Z2:   "Z2",
	Z3:   "Z3",
	Z4:   "Z4",
	Z5:   "Z5",
	Z6:   "Z6",
	Z7:   "Z7",
	Z8:   "Z8",
	Z9:   "Z9",
	Z10:  "Z10",
	Z11:  "Z11",
	Z12:  "Z12",
	Z13:  "Z13",
	Z14:  "Z14",
	Z15:  "Z15",
	Z16:  "Z16",
	Z17:  "Z17",
	Z18:  "Z18",
	Z19:  "Z19",
	Z20:  "Z20",
	Z21:  "Z21",
	Z22:  "Z22",
	Z23:  "Z23",
	Z24:  "Z24",
	Z25:  "Z25",
	Z26:  "Z26",
	Z27:  "Z27",
	Z28:  "Z28",
	Z29:  "Z29",
	Z30:  "Z30",
	Z31:  "Z31",
	K0:   "K0",
	K1:   "K1",
	K2:   "K2",
	K3:   "K3",
	K4:   "K4",
	K5:   "K5",
	K6:   "K6",
	K7:   "K7",
	CS:   "CS",
	SS:   "SS",
	DS:   "DS",
	ES:   "ES",
	FS:   "FS",
	GS:   "GS",
	GDTR: "GDTR",
	IDTR: "IDTR",
	LDTR: "LDTR",
	MSW:  "MSW",
	TASK: "TASK",
	CR0:  "CR0",
	CR1:  "CR1",
	CR2:  "CR2",
	CR3:  "CR3",
	CR4:  "CR4",
	CR5:  "CR5",
	CR6:  "CR6",
	CR7:  "CR7",
	CR8:  "CR8",
	CR9:  "CR9",
	CR10: "CR10",
	CR11: "CR11",
	CR12: "CR12",
	CR13: "CR13",
	CR14: "CR14",
	CR15: "CR15",
	DR0:  "DR0",
	DR1:  "DR1",
	DR2:  "DR2",
	DR3:  "DR3",
	DR4:  "DR4",
	DR5:  "DR5",
	DR6:  "DR6",
	DR7:  "DR7",
	DR8:  "DR8",
	DR9:  "DR9",
	DR10: "DR10",
	DR11: "DR11",
	DR12: "DR12",
	DR13: "DR13",
	DR14: "DR14",
	DR15: "DR15",
	TR0:  "TR0",
	TR1:  "TR1",
	TR2:  "TR2",
	TR3:  "TR3",
	TR4:  "TR4",
	TR5:  "TR5",
	TR6:  "TR6",
	TR7:  "TR7",
}