// Copyright 2015 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.

// This file encapsulates some of the odd characteristics of the ARM64
// instruction set, to minimize its interaction with the core of the
// assembler.

package arch

import (
	"cmd/internal/obj"
	"cmd/internal/obj/arm64"
	"errors"
)

var arm64LS = map[string]uint8{
	"P": arm64.C_XPOST,
	"W": arm64.C_XPRE,
}

var arm64Jump = map[string]bool{
	"B":     true,
	"BL":    true,
	"BEQ":   true,
	"BNE":   true,
	"BCS":   true,
	"BHS":   true,
	"BCC":   true,
	"BLO":   true,
	"BMI":   true,
	"BPL":   true,
	"BVS":   true,
	"BVC":   true,
	"BHI":   true,
	"BLS":   true,
	"BGE":   true,
	"BLT":   true,
	"BGT":   true,
	"BLE":   true,
	"CALL":  true,
	"CBZ":   true,
	"CBZW":  true,
	"CBNZ":  true,
	"CBNZW": true,
	"JMP":   true,
	"TBNZ":  true,
	"TBZ":   true,
}

func jumpArm64(word string) bool {
	return arm64Jump[word]
}

// IsARM64CMP reports whether the op (as defined by an arm.A* constant) is
// one of the comparison instructions that require special handling.
func IsARM64CMP(op obj.As) bool {
	switch op {
	case arm64.ACMN, arm64.ACMP, arm64.ATST,
		arm64.ACMNW, arm64.ACMPW, arm64.ATSTW,
		arm64.AFCMPS, arm64.AFCMPD,
		arm64.AFCMPES, arm64.AFCMPED:
		return true
	}
	return false
}

// IsARM64STLXR reports whether the op (as defined by an arm64.A*
// constant) is one of the STLXR-like instructions that require special
// handling.
func IsARM64STLXR(op obj.As) bool {
	switch op {
	case arm64.ASTLXRB, arm64.ASTLXRH, arm64.ASTLXRW, arm64.ASTLXR,
		arm64.ASTXRB, arm64.ASTXRH, arm64.ASTXRW, arm64.ASTXR,
		arm64.ASTXP, arm64.ASTXPW, arm64.ASTLXP, arm64.ASTLXPW,
		arm64.ASWPB, arm64.ASWPH, arm64.ASWPW, arm64.ASWPD,
		arm64.ALDADDB, arm64.ALDADDH, arm64.ALDADDW, arm64.ALDADDD,
		arm64.ALDANDB, arm64.ALDANDH, arm64.ALDANDW, arm64.ALDANDD,
		arm64.ALDEORB, arm64.ALDEORH, arm64.ALDEORW, arm64.ALDEORD,
		arm64.ALDORB, arm64.ALDORH, arm64.ALDORW, arm64.ALDORD,
		arm64.ALDADDALD, arm64.ALDADDALW:
		return true
	}
	return false
}

// ARM64Suffix handles the special suffix for the ARM64.
// It returns a boolean to indicate success; failure means
// cond was unrecognized.
func ARM64Suffix(prog *obj.Prog, cond string) bool {
	if cond == "" {
		return true
	}
	bits, ok := parseARM64Suffix(cond)
	if !ok {
		return false
	}
	prog.Scond = bits
	return true
}

// parseARM64Suffix parses the suffix attached to an ARM64 instruction.
// The input is a single string consisting of period-separated condition
// codes, such as ".P.W". An initial period is ignored.
func parseARM64Suffix(cond string) (uint8, bool) {
	if cond == "" {
		return 0, true
	}
	return parseARMCondition(cond, arm64LS, nil)
}

func arm64RegisterNumber(name string, n int16) (int16, bool) {
	switch name {
	case "F":
		if 0 <= n && n <= 31 {
			return arm64.REG_F0 + n, true
		}
	case "R":
		if 0 <= n && n <= 30 { // not 31
			return arm64.REG_R0 + n, true
		}
	case "V":
		if 0 <= n && n <= 31 {
			return arm64.REG_V0 + n, true
		}
	}
	return 0, false
}

// IsARM64TBL reports whether the op (as defined by an arm64.A*
// constant) is one of the table lookup instructions that require special
// handling.
func IsARM64TBL(op obj.As) bool {
	return op == arm64.AVTBL
}

// ARM64RegisterExtension parses an ARM64 register with extension or arrangement.
func ARM64RegisterExtension(a *obj.Addr, ext string, reg, num int16, isAmount, isIndex bool) error {
	Rnum := (reg & 31) + int16(num<<5)
	if isAmount {
		if num < 0 || num > 7 {
			return errors.New("index shift amount is out of range")
		}
	}
	switch ext {
	case "UXTB":
		if !isAmount {
			return errors.New("invalid register extension")
		}
		if a.Type == obj.TYPE_MEM {
			return errors.New("invalid shift for the register offset addressing mode")
		}
		a.Reg = arm64.REG_UXTB + Rnum
	case "UXTH":
		if !isAmount {
			return errors.New("invalid register extension")
		}
		if a.Type == obj.TYPE_MEM {
			return errors.New("invalid shift for the register offset addressing mode")
		}
		a.Reg = arm64.REG_UXTH + Rnum
	case "UXTW":
		if !isAmount {
			return errors.New("invalid register extension")
		}
		// effective address of memory is a base register value and an offset register value.
		if a.Type == obj.TYPE_MEM {
			a.Index = arm64.REG_UXTW + Rnum
		} else {
			a.Reg = arm64.REG_UXTW + Rnum
		}
	case "UXTX":
		if !isAmount {
			return errors.New("invalid register extension")
		}
		if a.Type == obj.TYPE_MEM {
			return errors.New("invalid shift for the register offset addressing mode")
		}
		a.Reg = arm64.REG_UXTX + Rnum
	case "SXTB":
		if !isAmount {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_SXTB + Rnum
	case "SXTH":
		if !isAmount {
			return errors.New("invalid register extension")
		}
		if a.Type == obj.TYPE_MEM {
			return errors.New("invalid shift for the register offset addressing mode")
		}
		a.Reg = arm64.REG_SXTH + Rnum
	case "SXTW":
		if !isAmount {
			return errors.New("invalid register extension")
		}
		if a.Type == obj.TYPE_MEM {
			a.Index = arm64.REG_SXTW + Rnum
		} else {
			a.Reg = arm64.REG_SXTW + Rnum
		}
	case "SXTX":
		if !isAmount {
			return errors.New("invalid register extension")
		}
		if a.Type == obj.TYPE_MEM {
			a.Index = arm64.REG_SXTX + Rnum
		} else {
			a.Reg = arm64.REG_SXTX + Rnum
		}
	case "LSL":
		if !isAmount {
			return errors.New("invalid register extension")
		}
		a.Index = arm64.REG_LSL + Rnum
	case "B8":
		if isIndex {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_8B & 15) << 5)
	case "B16":
		if isIndex {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_16B & 15) << 5)
	case "H4":
		if isIndex {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_4H & 15) << 5)
	case "H8":
		if isIndex {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_8H & 15) << 5)
	case "S2":
		if isIndex {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_2S & 15) << 5)
	case "S4":
		if isIndex {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_4S & 15) << 5)
	case "D1":
		if isIndex {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_1D & 15) << 5)
	case "D2":
		if isIndex {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_2D & 15) << 5)
	case "Q1":
		if isIndex {
			return errors.New("invalid register extension")
		}
		a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_1Q & 15) << 5)
	case "B":
		if !isIndex {
			return nil
		}
		a.Reg = arm64.REG_ELEM + (reg & 31) + ((arm64.ARNG_B & 15) << 5)
		a.Index = num
	case "H":
		if !isIndex {
			return nil
		}
		a.Reg = arm64.REG_ELEM + (reg & 31) + ((arm64.ARNG_H & 15) << 5)
		a.Index = num
	case "S":
		if !isIndex {
			return nil
		}
		a.Reg = arm64.REG_ELEM + (reg & 31) + ((arm64.ARNG_S & 15) << 5)
		a.Index = num
	case "D":
		if !isIndex {
			return nil
		}
		a.Reg = arm64.REG_ELEM + (reg & 31) + ((arm64.ARNG_D & 15) << 5)
		a.Index = num
	default:
		return errors.New("unsupported register extension type: " + ext)
	}

	return nil
}

// ARM64RegisterArrangement parses an ARM64 vector register arrangement.
func ARM64RegisterArrangement(reg int16, name, arng string) (int64, error) {
	var curQ, curSize uint16
	if name[0] != 'V' {
		return 0, errors.New("expect V0 through V31; found: " + name)
	}
	if reg < 0 {
		return 0, errors.New("invalid register number: " + name)
	}
	switch arng {
	case "B8":
		curSize = 0
		curQ = 0
	case "B16":
		curSize = 0
		curQ = 1
	case "H4":
		curSize = 1
		curQ = 0
	case "H8":
		curSize = 1
		curQ = 1
	case "S2":
		curSize = 2
		curQ = 0
	case "S4":
		curSize = 2
		curQ = 1
	case "D1":
		curSize = 3
		curQ = 0
	case "D2":
		curSize = 3
		curQ = 1
	default:
		return 0, errors.New("invalid arrangement in ARM64 register list")
	}
	return (int64(curQ) & 1 << 30) | (int64(curSize&3) << 10), nil
}

// ARM64RegisterListOffset generates offset encoding according to AArch64 specification.
func ARM64RegisterListOffset(firstReg, regCnt int, arrangement int64) (int64, error) {
	offset := int64(firstReg)
	switch regCnt {
	case 1:
		offset |= 0x7 << 12
	case 2:
		offset |= 0xa << 12
	case 3:
		offset |= 0x6 << 12
	case 4:
		offset |= 0x2 << 12
	default:
		return 0, errors.New("invalid register numbers in ARM64 register list")
	}
	offset |= arrangement
	// arm64 uses the 60th bit to differentiate from other archs
	// For more details, refer to: obj/arm64/list7.go
	offset |= 1 << 60
	return offset, nil
}