llvm-native-core 0.1.16

//! X86 Full Machine Code Encoder — encodes all X86FullOpcode instructions
//! into binary X86 byte sequences per Intel SDM Volume 2.
//!
//! Handles:
//! - Legacy encoding (opcode + ModR/M + SIB + displacement + immediate)
//! - REX prefix for 64-bit mode extended registers
//! - VEX 2-byte and 3-byte prefixes for AVX/AVX2/FMA
//! - EVEX prefix for AVX-512
//! - XOP prefix for AMD XOP instructions
//! - All addressing modes (16-bit, 32-bit, 64-bit)
//! - RIP-relative addressing mode
//! - VSIB addressing for gather/scatter instructions
//!
//! Clean-room behavioral reconstruction from:
//! - Intel® 64 and IA-32 Architectures Software Developer's Manual, Volume 2
//! - AMD64 Architecture Programmer's Manual, Volume 3

use super::x86_full_instr_info::{
    EncodingForm, InstrEncodingInfo, X86FullInstrInfo, X86FullOpcode, X86FullOpcode::*,
};
use super::x86_instr_info::{OperandType, X86MemOperand, X86Operand};
pub use super::x86_mc_encoder::X86Mode;
use super::x86_mc_encoder::{mod_field, prefixes, X86MCEncoder};
use super::x86_register_info::{
    RegClass, AH, AL, AX, BH, BL, BPL, BX, CH, CL, CS, CX, DH, DIL, DL, DS, DX, EAX, EBP, EBX, ECX,
    EDI, EDX, ES, ESI, ESP, FS, GS, K0, K1, K2, K3, K4, K5, K6, K7, R10, R10B, R10D, R10W, R11,
    R11B, R11D, R11W, R12, R12B, R12D, R12W, R13, R13B, R13D, R13W, R14, R14B, R14D, R14W, R15,
    R15B, R15D, R15W, R8, R8B, R8D, R8W, R9, R9B, R9D, R9W, RAX, RBP, RBX, RCX, RDI, RDX, RIP, RSI,
    RSP, SIL, SPL, SS, XMM0, XMM1, XMM10, XMM11, XMM12, XMM13, XMM14, XMM15, XMM16, XMM17, XMM18,
    XMM19, XMM2, XMM20, XMM21, XMM22, XMM23, XMM24, XMM25, XMM26, XMM27, XMM28, XMM29, XMM3, XMM30,
    XMM31, XMM4, XMM5, XMM6, XMM7, XMM8, XMM9, YMM0, YMM1, YMM10, YMM11, YMM12, YMM13, YMM14,
    YMM15, YMM16, YMM17, YMM18, YMM19, YMM2, YMM20, YMM21, YMM22, YMM23, YMM24, YMM25, YMM26,
    YMM27, YMM28, YMM29, YMM3, YMM30, YMM31, YMM4, YMM5, YMM6, YMM7, YMM8, YMM9, ZMM0, ZMM1, ZMM10,
    ZMM11, ZMM12, ZMM13, ZMM14, ZMM15, ZMM16, ZMM17, ZMM18, ZMM19, ZMM2, ZMM20, ZMM21, ZMM22,
    ZMM23, ZMM24, ZMM25, ZMM26, ZMM27, ZMM28, ZMM29, ZMM3, ZMM30, ZMM31, ZMM4, ZMM5, ZMM6, ZMM7,
    ZMM8, ZMM9,
};
use super::x86_subtarget::X86Subtarget;

// ============================================================================
// REX prefix constants
// ============================================================================

/// REX prefix byte values.
pub mod rex_prefix {
    /// REX prefix base value.
    pub const REX_BASE: u8 = 0x40;
    /// REX.W — 64-bit operand size.
    pub const REX_W: u8 = 0x48;
    /// REX.R — extension of ModR/M reg field.
    pub const REX_R: u8 = 0x44;
    /// REX.X — extension of SIB index field.
    pub const REX_X: u8 = 0x42;
    /// REX.B — extension of ModR/M r/m field, SIB base, or opcode reg.
    pub const REX_B: u8 = 0x41;
}

// ============================================================================
// VEX prefix constants
// ============================================================================

/// VEX prefix helpers.
pub mod vex_prefix {
    /// 2-byte VEX prefix: 0xC5.
    pub const VEX_2BYTE: u8 = 0xC5;
    /// 3-byte VEX prefix: 0xC4.
    pub const VEX_3BYTE: u8 = 0xC4;

    /// Invert a register field for VEX encoding.
    /// In VEX, register fields are stored in 1's complement form.
    pub fn invert_reg(reg: u8) -> u8 {
        (!reg) & 0xF
    }

    /// Build a 2-byte VEX prefix.
    ///
    /// 2-byte VEX layout: [C5] [RvvvvLpp]
    ///   R: 1-bit, 1's complement of REX.R
    ///   vvvv: 4-bit, 1's complement of source register
    ///   L: 1-bit, vector length (0=128, 1=256)
    ///   pp: 2-bit, implied mandatory prefix (0=none, 1=66, 2=F3, 3=F2)
    pub fn build_2byte(r: bool, vvvv: u8, l: bool, pp: u8) -> [u8; 2] {
        let byte1 = (!r as u8) << 7 | (invert_reg(vvvv) << 3) | ((l as u8) << 2) | (pp & 0x3);
        [VEX_2BYTE, byte1]
    }

    /// Build a 3-byte VEX prefix.
    ///
    /// 3-byte VEX layout: [C4] [RXBmmmmm] [WvvvvLpp]
    ///   R: 1-bit, 1's complement of REX.R
    ///   X: 1-bit, 1's complement of REX.X
    ///   B: 1-bit, 1's complement of REX.B
    ///   mmmmm: 5-bit, opcode map selector (1=0F, 2=0F38, 3=0F3A)
    ///   W: 1-bit, REX.W for 64-bit operand size
    ///   vvvv: 4-bit, 1's complement of source register
    ///   L: 1-bit, vector length
    ///   pp: 2-bit, implied mandatory prefix
    pub fn build_3byte(
        r: bool,
        x: bool,
        b: bool,
        mmmmm: u8,
        w: bool,
        vvvv: u8,
        l: bool,
        pp: u8,
    ) -> [u8; 3] {
        let byte1 = (!r as u8) << 7 | (!x as u8) << 6 | (!b as u8) << 5 | (mmmmm & 0x1F);
        let byte2 = (w as u8) << 7 | (invert_reg(vvvv) << 3) | ((l as u8) << 2) | (pp & 0x3);
        [VEX_3BYTE, byte1, byte2]
    }
}

// ============================================================================
// EVEX prefix constants
// ============================================================================

/// EVEX prefix helpers.
pub mod evex_prefix {
    /// EVEX prefix first byte: always 0x62.
    pub const EVEX_MAGIC: u8 = 0x62;

    /// Build a 4-byte EVEX prefix.
    ///
    /// EVEX layout: [62] [P0] [P1] [P2]
    ///   P0: [R X B R' 0 0 mmm]
    ///   P1: [W vvvv 1 pp]
    ///   P2: [z L'L b V' aaa]
    pub fn build_evex(
        r: bool,
        x: bool,
        b: bool,
        r_prime: bool,
        mmmm: u8,
        w: bool,
        vvvv: u8,
        pp: u8,
        z: bool,
        ll: u8,
        b_prim: bool,
        aaa: u8,
    ) -> [u8; 4] {
        let p0 = (!r as u8) << 7
            | (!x as u8) << 6
            | (!b as u8) << 5
            | (!r_prime as u8) << 4
            | (mmmm & 0x07);
        let p1 = (w as u8) << 7
            | (super::vex_prefix::invert_reg(vvvv) << 3)
            | 0x04  // bit 2 must be 1
            | (pp & 0x03);
        let p2 = (z as u8) << 7
            | ((ll & 0x03) << 5)
            | (b_prim as u8) << 4
            | 0x08  // V' = 0 (no additional source)
            | (aaa & 0x07);
        [EVEX_MAGIC, p0, p1, p2]
    }
}

// ============================================================================
// XOP prefix constants
// ============================================================================

/// XOP prefix helpers (AMD XOP extension).
pub mod xop_prefix {
    /// XOP prefix first byte: always 0x8F.
    pub const XOP_MAGIC: u8 = 0x8F;

    /// Build a 3-byte XOP prefix.
    /// XOP layout: [8F] [RXBmmmmm] [WvvvvLpp]
    pub fn build_xop(
        r: bool,
        x: bool,
        b: bool,
        mmmmm: u8,
        w: bool,
        vvvv: u8,
        l: bool,
        pp: u8,
    ) -> [u8; 3] {
        let byte1 = (!r as u8) << 7 | (!x as u8) << 6 | (!b as u8) << 5 | (mmmmm & 0x1F);
        let byte2 = (w as u8) << 7
            | (super::vex_prefix::invert_reg(vvvv) << 3)
            | ((l as u8) << 2)
            | (pp & 0x3);
        [XOP_MAGIC, byte1, byte2]
    }
}

// ============================================================================
// SIB byte constants
// ============================================================================

/// SIB byte layout helpers.
pub mod sib_byte {
    /// Build a SIB byte from scale, index, and base fields.
    pub fn build(scale: u8, index: u8, base: u8) -> u8 {
        (scale & 0x3) << 6 | (index & 0x7) << 3 | (base & 0x7)
    }

    /// SIB scale values.
    pub const SCALE_1: u8 = 0;
    pub const SCALE_2: u8 = 1;
    pub const SCALE_4: u8 = 2;
    pub const SCALE_8: u8 = 3;

    /// Special SIB index value meaning "no index register".
    pub const NO_INDEX: u8 = 4;
    /// Special SIB base value meaning "R13 or RBP + disp32" (depends on mod).
    pub const RBP_BASE: u8 = 5;
}

// ============================================================================
// EVEX extended types: tuple, broadcast, rounding
// ============================================================================

/// EVEX tuple type: determines compressed displacement multiplier.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum EvexTuple {
    Full,
    FullMem,
    Half,
    HalfMem,
    Quarter,
    QuarterMem,
    Eighth,
    EighthMem,
    Scalar,
    Mem128,
}

impl EvexTuple {
    pub fn multiplier(&self) -> u8 {
        match self {
            EvexTuple::Full | EvexTuple::FullMem => 64,
            EvexTuple::Half | EvexTuple::HalfMem => 32,
            EvexTuple::Quarter | EvexTuple::QuarterMem | EvexTuple::Mem128 => 16,
            EvexTuple::Eighth | EvexTuple::EighthMem => 8,
            EvexTuple::Scalar => 4,
        }
    }
    pub fn is_memory(&self) -> bool {
        matches!(
            self,
            EvexTuple::FullMem | EvexTuple::HalfMem | EvexTuple::QuarterMem | EvexTuple::EighthMem
        )
    }
}

/// EVEX broadcast mode for memory operand.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum EvexBroadcast {
    None,
    Broadcast1To2,
    Broadcast1To4,
    Broadcast1To8,
    Broadcast1To16,
    Broadcast1To32,
}

impl EvexBroadcast {
    pub fn is_broadcast(&self) -> bool {
        !matches!(self, EvexBroadcast::None)
    }
}

/// EVEX rounding mode for FP operations.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum EvexRounding {
    None,
    RnSae,
    RdSae,
    RuSae,
    RzSae,
    Sae,
}

impl EvexRounding {
    pub fn is_active(&self) -> bool {
        !matches!(self, EvexRounding::None)
    }
    pub fn rc_bits(&self) -> u8 {
        match self {
            EvexRounding::RnSae => 0,
            EvexRounding::RdSae => 1,
            EvexRounding::RuSae => 2,
            EvexRounding::RzSae => 3,
            EvexRounding::Sae => 0,
            EvexRounding::None => 0,
        }
    }
}

// ============================================================================
// X86FullMCEncoder — complete X86 instruction encoder
// ============================================================================

/// Complete X86 instruction encoder supporting all encoding forms
/// (legacy, REX, VEX, EVEX, XOP) for the full X86FullOpcode set.
pub struct X86FullMCEncoder {
    /// Accumulated output bytes.
    pub output: Vec<u8>,
    /// Operating mode (16-bit, 32-bit, or 64-bit).
    pub mode: X86Mode,
    /// Target subtarget for feature-aware encoding.
    pub subtarget: X86Subtarget,
    /// Full instruction info database.
    pub instr_info: X86FullInstrInfo,
}

impl X86FullMCEncoder {
    /// Create a new full encoder.
    pub fn new(mode: X86Mode, subtarget: X86Subtarget) -> Self {
        Self {
            output: Vec::new(),
            mode,
            subtarget,
            instr_info: X86FullInstrInfo::new(),
        }
    }

    /// Create a new full encoder with a pre-existing instr_info (for reuse).
    pub fn with_info(mode: X86Mode, subtarget: X86Subtarget, info: X86FullInstrInfo) -> Self {
        Self {
            output: Vec::new(),
            mode,
            subtarget,
            instr_info: info,
        }
    }

    // ========================================================================
    // Main encoding entry point
    // ========================================================================

    /// Encode a single instruction into bytes.
    /// Returns the encoded bytes, clearing the internal output buffer.
    pub fn encode_instruction(
        &mut self,
        opcode: X86FullOpcode,
        operands: &[X86Operand],
    ) -> Vec<u8> {
        self.output.clear();

        let Some(encoding) = self.instr_info.get(opcode).cloned() else {
            // Unknown opcode — emit UD2
            self.output.push(0x0F);
            self.output.push(0x0B);
            return self.output.clone();
        };

        // 1. Emit encoding prefix (VEX/EVEX/XOP) or legacy prefixes
        match encoding.encoding_form {
            EncodingForm::VEX | EncodingForm::VEX3Byte => {
                self.encode_vex_prefix(&encoding, operands);
            }
            EncodingForm::EVEX => {
                self.encode_evex_prefix(&encoding, operands);
            }
            EncodingForm::XOP => {
                self.encode_xop_prefix(&encoding, operands);
            }
            EncodingForm::Legacy | EncodingForm::LegacyREX => {
                self.encode_legacy_prefixes(&encoding, operands);
            }
            EncodingForm::None => {
                // Pure prefix instruction (e.g., REP, LOCK)
            }
        }

        // 2. Emit opcode bytes
        self.encode_opcode_bytes(&encoding);

        // 3. Emit ModR/M if required
        if encoding.requires_modrm {
            let modrm = self.compute_modrm(&encoding, operands);
            self.output.push(modrm);
        }

        // 4. Emit SIB if needed (memory operand with index or RSP/R12 base)
        if self.needs_sib(operands) {
            let sib = self.compute_sib(operands);
            self.output.push(sib);
        }

        // 5. Emit displacement
        self.encode_displacement(operands);

        // 6. Emit immediate(s)
        self.encode_immediates(operands);

        self.output.clone()
    }

    // ========================================================================
    // Prefix encoding
    // ========================================================================

    /// Encode VEX prefix (2-byte or 3-byte).
    fn encode_vex_prefix(&mut self, encoding: &InstrEncodingInfo, operands: &[X86Operand]) {
        use EncodingForm::*;
        let use_3byte = matches!(encoding.encoding_form, VEX3Byte);

        let mut rex_r = false;
        let mut rex_x = false;
        let mut rex_b = false;
        let mut rex_w = false;

        // Determine register extensions
        for (i, op) in operands.iter().enumerate() {
            if let X86Operand::Reg(reg) = op {
                if *reg >= 8 {
                    match i {
                        0 => rex_b = true, // destination (r/m field)
                        1 => rex_r = true, // source (reg field)
                        2 => rex_r = true, // second source
                        _ => {}
                    }
                }
                // REX.W for 64-bit GPR operands
                if self.mode.is_64bit() && (*reg == RAX || *reg >= R8) && *reg < 32 {
                    // Check for GPR64 usage
                    if self.is_gpr64_register(*reg) {
                        rex_w = true;
                    }
                }
            } else if let X86Operand::Mem(mem) = op {
                if mem.base >= 8 {
                    rex_b = true;
                }
                if mem.index >= 8 {
                    rex_x = true;
                }
            }
        }

        let vvvv = if operands.len() >= 2 {
            self.get_reg_field_for_operand(operands, 1)
        } else {
            0
        };

        let l = self.vector_length_from_operands(operands);
        let pp = encoding.mandatory_prefix;
        let mmmmm = encoding.opcode_map;

        if use_3byte || rex_x || rex_w {
            let bytes = vex_prefix::build_3byte(rex_r, rex_x, rex_b, mmmmm, rex_w, vvvv, l, pp);
            self.output.extend_from_slice(&bytes);
        } else {
            let bytes = vex_prefix::build_2byte(rex_r, vvvv, l, pp);
            self.output.extend_from_slice(&bytes);
        }
    }

    /// Encode EVEX prefix for AVX-512 instructions.
    fn encode_evex_prefix(&mut self, encoding: &InstrEncodingInfo, operands: &[X86Operand]) {
        let mut rex_r = false;
        let mut rex_x = false;
        let mut rex_b = false;
        let mut rex_w = false;
        let mut r_prime = false;

        for (i, op) in operands.iter().enumerate() {
            if let X86Operand::Reg(reg) = op {
                if *reg >= 16 {
                    r_prime = true;
                }
                if *reg >= 8 {
                    match i {
                        0 => rex_b = true,
                        1 => rex_r = true,
                        2 => rex_r = true,
                        _ => {}
                    }
                }
                if self.mode.is_64bit() && self.is_gpr64_register(*reg) {
                    rex_w = true;
                }
            } else if let X86Operand::Mem(mem) = op {
                if mem.base >= 8 {
                    rex_b = true;
                }
                if mem.index >= 16 {
                    rex_x = true;
                    r_prime = true;
                } else if mem.index >= 8 {
                    rex_x = true;
                }
            }
        }

        let vvvv = if operands.len() >= 2 {
            self.get_reg_field_for_operand(operands, 1)
        } else {
            0
        };

        let ll = self.vector_length_512(operands);
        let pp = encoding.mandatory_prefix;
        let mmmm = encoding.opcode_map & 0x07;

        let bytes = evex_prefix::build_evex(
            rex_r, rex_x, rex_b, r_prime, mmmm, rex_w, vvvv, pp,
            false, // zeroing mask (z) — not applied for reg forms
            ll, false, // b' broadcast
            0,     // aaa — no mask
        );
        self.output.extend_from_slice(&bytes);
    }

    /// Encode XOP prefix.
    fn encode_xop_prefix(&mut self, encoding: &InstrEncodingInfo, operands: &[X86Operand]) {
        let rex_r = false;
        let rex_x = false;
        let rex_b = false;
        let rex_w = false;
        let vvvv = if operands.len() >= 2 {
            self.get_reg_field_for_operand(operands, 1)
        } else {
            0
        };
        let l = false;
        let pp = encoding.mandatory_prefix;
        let mmmmm = encoding.opcode_map & 0x1F;

        let bytes = xop_prefix::build_xop(rex_r, rex_x, rex_b, mmmmm, rex_w, vvvv, l, pp);
        self.output.extend_from_slice(&bytes);
    }

    // ========================================================================
    // EVEX extended encoding: tuple types, broadcast, rounding, opmask
    // ========================================================================

    /// Full EVEX encoding with opmask, broadcast, rounding, and tuple type.
    fn encode_evex_full(
        &mut self,
        encoding: &InstrEncodingInfo,
        operands: &[X86Operand],
        opmask: Option<u8>, // k1-k7, None=no masking
        zeroing: bool,      // {z} zeroing merge mode
        broadcast: EvexBroadcast,
        rounding: EvexRounding,
        tuple: EvexTuple,
    ) {
        let mut rex_r = false;
        let mut rex_x = false;
        let mut rex_b = false;
        let mut rex_w = false;
        let mut r_prime = false;

        let kreg = opmask.unwrap_or(0) & 0x7; // opmask register k1-k7
        let z = zeroing && opmask.is_some();

        for (i, op) in operands.iter().enumerate() {
            if let X86Operand::Reg(reg) = op {
                if *reg >= 16 {
                    r_prime = true;
                }
                if *reg >= 8 {
                    match i {
                        0 => rex_b = true,
                        1 => rex_r = true,
                        2 => rex_r = true,
                        _ => {}
                    }
                }
                if self.mode.is_64bit() && self.is_gpr64_register(*reg) {
                    rex_w = true;
                }
            } else if let X86Operand::Mem(mem) = op {
                if mem.base >= 8 {
                    rex_b = true;
                }
                if mem.index >= 16 {
                    rex_x = true;
                    r_prime = true;
                } else if mem.index >= 8 {
                    rex_x = true;
                }
            }
        }

        let vvvv = if operands.len() >= 2 {
            self.get_reg_field_for_operand(operands, 1)
        } else {
            0
        };

        let mut ll = self.vector_length_512(operands);
        let b_prim = broadcast.is_broadcast();

        // Rounding mode overrides LL bits
        if rounding.is_active() {
            ll = rounding.rc_bits() & 0x3;
        }

        let pp = encoding.mandatory_prefix;
        let mmmm = encoding.opcode_map & 0x07;
        let aaa = kreg;

        let bytes = evex_prefix::build_evex(
            rex_r, rex_x, rex_b, r_prime, mmmm, rex_w, vvvv, pp, z, ll, b_prim, aaa,
        );
        self.output.extend_from_slice(&bytes);
    }

    /// Encode EVEX with mask and zeroing (most common AVX-512 case).
    pub fn encode_evex_masked(
        &mut self,
        opcode: X86FullOpcode,
        operands: &[X86Operand],
        opmask: Option<u8>,
        zeroing: bool,
    ) -> Vec<u8> {
        self.output.clear();

        let Some(encoding) = self.instr_info.get(opcode).cloned() else {
            self.output.push(0x0F);
            self.output.push(0x0B);
            return self.output.clone();
        };

        self.encode_evex_full(
            &encoding,
            operands,
            opmask,
            zeroing,
            EvexBroadcast::None,
            EvexRounding::None,
            EvexTuple::Full,
        );

        self.encode_opcode_bytes(&encoding);

        if encoding.requires_modrm {
            let modrm = self.compute_modrm(&encoding, operands);
            self.output.push(modrm);
        }

        if self.needs_sib(operands) {
            let sib = self.compute_sib(operands);
            self.output.push(sib);
        }

        self.encode_displacement(operands);
        self.encode_immediates(operands);

        self.output.clone()
    }

    /// Encode EVEX with broadcast memory operand.
    pub fn encode_evex_broadcast(
        &mut self,
        opcode: X86FullOpcode,
        operands: &[X86Operand],
        broadcast: EvexBroadcast,
        tuple: EvexTuple,
    ) -> Vec<u8> {
        self.output.clear();

        let Some(encoding) = self.instr_info.get(opcode).cloned() else {
            self.output.push(0x0F);
            self.output.push(0x0B);
            return self.output.clone();
        };

        self.encode_evex_full(
            &encoding,
            operands,
            None,
            false,
            broadcast,
            EvexRounding::None,
            tuple,
        );

        self.encode_opcode_bytes(&encoding);

        if encoding.requires_modrm {
            let modrm = self.compute_modrm(&encoding, operands);
            self.output.push(modrm);
        }

        if self.needs_sib(operands) {
            let sib = self.compute_sib(operands);
            self.output.push(sib);
        }

        // Compressed displacement for broadcast
        self.encode_evex_displacement(operands, tuple);
        self.encode_immediates(operands);

        self.output.clone()
    }

    /// Encode EVEX with rounding mode override.
    pub fn encode_evex_rounding(
        &mut self,
        opcode: X86FullOpcode,
        operands: &[X86Operand],
        rounding: EvexRounding,
    ) -> Vec<u8> {
        self.output.clear();

        let Some(encoding) = self.instr_info.get(opcode).cloned() else {
            self.output.push(0x0F);
            self.output.push(0x0B);
            return self.output.clone();
        };

        self.encode_evex_full(
            &encoding,
            operands,
            None,
            false,
            EvexBroadcast::None,
            rounding,
            EvexTuple::Full,
        );

        self.encode_opcode_bytes(&encoding);

        if encoding.requires_modrm {
            let modrm = self.compute_modrm(&encoding, operands);
            self.output.push(modrm);
        }

        if self.needs_sib(operands) {
            let sib = self.compute_sib(operands);
            self.output.push(sib);
        }

        self.encode_displacement(operands);
        self.encode_immediates(operands);

        self.output.clone()
    }

    /// Encode EVEX with compressed displacement (tuple type).
    fn encode_evex_displacement(&mut self, operands: &[X86Operand], tuple: EvexTuple) {
        let multiplier = tuple.multiplier();
        for op in operands {
            if let X86Operand::Mem(mem) = op {
                if mem.displacement != 0 {
                    let compressed = mem.displacement / multiplier as i32;
                    // Ensure compressed displacement fits in disp8
                    let disp = (compressed as i8) as u8;
                    self.output.push(disp);
                    return;
                }
            }
        }
    }

    // ========================================================================
    // XOP encoding convenience methods (AMD)
    // ========================================================================

    /// Raw XOP encode: emits XOP prefix + opcode + ModRM for two registers.
    fn encode_xop_raw(&mut self, mmmmm: u8, opcode: u8, dst: u16, src: u16) -> Vec<u8> {
        self.output.clear();

        // XOP prefix: 8F RXB.mmmmm W.vvvv.L.pp
        let rex_r = src >= 8;
        let rex_x = false;
        let rex_b = dst >= 8;
        let rex_w = false;
        let vvvv = 0; // No third source for 2-operand forms
        let l = false; // 128-bit
        let pp = 0; // No mandatory prefix

        let xop_prefix = xop_prefix::build_xop(rex_r, rex_x, rex_b, mmmmm, rex_w, vvvv, l, pp);
        self.output.extend_from_slice(&xop_prefix);

        // Opcode byte
        self.output.push(opcode);

        // ModR/M: mod=3 (reg), reg=src%8, rm=dst%8
        let modrm = 0xC0 | ((src & 0x7) << 3) | (dst & 0x7);
        self.output.push(modrm as u8);

        self.output.clone()
    }

    /// Raw XOP encode with immediate byte.
    fn encode_xop_raw_imm(
        &mut self,
        mmmmm: u8,
        opcode: u8,
        dst: u16,
        src: u16,
        imm: u8,
    ) -> Vec<u8> {
        let mut bytes = self.encode_xop_raw(mmmmm, opcode, dst, src);
        bytes.push(imm);
        bytes
    }

    /// Encode VPHADDBD (XOP: map 8, opcode C2).
    pub fn encode_vphaddbd(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(8, 0xC2, dst, src)
    }

    /// Encode VPHADDBQ (XOP: map 8, opcode C3).
    pub fn encode_vphaddbq(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(8, 0xC3, dst, src)
    }

    /// Encode VPHADDWD (XOP: map 8, opcode C6).
    pub fn encode_vphaddwd(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(8, 0xC6, dst, src)
    }

    /// Encode VPHADDWQ (XOP: map 8, opcode C7).
    pub fn encode_vphaddwq(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(8, 0xC7, dst, src)
    }

    /// Encode VPHADDDQ (XOP: map 8, opcode CB).
    pub fn encode_vphadddq(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(8, 0xCB, dst, src)
    }

    /// Encode VPROTB (XOP: map 8, opcode 90).
    pub fn encode_vprotb(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(8, 0x90, dst, src)
    }

    /// Encode VPROTW (XOP: map 8, opcode 91).
    pub fn encode_vprotw(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(8, 0x91, dst, src)
    }

    /// Encode VPROTD (XOP: map 8, opcode 92).
    pub fn encode_vprotd(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(8, 0x92, dst, src)
    }

    /// Encode VPROTQ (XOP: map 8, opcode 93).
    pub fn encode_vprotq(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(8, 0x93, dst, src)
    }

    /// Encode VPSHAB (XOP: map 9, opcode 98).
    pub fn encode_vpshab(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(9, 0x98, dst, src)
    }

    /// Encode VPSHAW (XOP: map 9, opcode 99).
    pub fn encode_vpshaw(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(9, 0x99, dst, src)
    }

    /// Encode VPSHAD (XOP: map 9, opcode 9A).
    pub fn encode_vpshad(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(9, 0x9A, dst, src)
    }

    /// Encode VPSHAQ (XOP: map 9, opcode 9B).
    pub fn encode_vpshaq(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(9, 0x9B, dst, src)
    }

    /// Encode VPSHLB (XOP: map 9, opcode 94).
    pub fn encode_vpshlb(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(9, 0x94, dst, src)
    }

    /// Encode VPSHLW (XOP: map 9, opcode 95).
    pub fn encode_vpshlw(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(9, 0x95, dst, src)
    }

    /// Encode VPSHLD (XOP: map 9, opcode 96).
    pub fn encode_vpshld(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(9, 0x96, dst, src)
    }

    /// Encode VPSHLQ (XOP: map 9, opcode 97).
    pub fn encode_vpshlq(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_xop_raw(9, 0x97, dst, src)
    }

    /// Encode legacy prefixes (REX, operand-size override, address-size override).
    fn encode_legacy_prefixes(&mut self, encoding: &InstrEncodingInfo, operands: &[X86Operand]) {
        let mut rex = false;
        let mut rex_w = false;
        let mut rex_r = false;
        let mut rex_x = false;
        let mut rex_b = false;

        // Check if any operand requires REX
        if self.mode.is_64bit() {
            for (i, op) in operands.iter().enumerate() {
                match op {
                    X86Operand::Reg(reg) => {
                        if *reg >= 8 {
                            match i {
                                0 => rex_b = true,
                                _ => rex_r = true,
                            }
                            rex = true;
                        }
                        if self.is_gpr64_register(*reg) {
                            rex_w = true;
                            rex = true;
                        }
                    }
                    X86Operand::Mem(mem) => {
                        if mem.base >= 8 {
                            rex_b = true;
                            rex = true;
                        }
                        if mem.index >= 8 {
                            rex_x = true;
                            rex = true;
                        }
                    }
                    _ => {}
                }
            }
        }

        // LegacyREX forms always need REX in 64-bit mode
        if matches!(encoding.encoding_form, EncodingForm::LegacyREX) && self.mode.is_64bit() {
            rex = true;
            // For CMOV, SETcc, etc. — ensure W is set for 64-bit forms
        }

        if rex {
            let rex_byte = rex_prefix::REX_BASE
                | (if rex_w { 0x08 } else { 0 })
                | (if rex_r { 0x04 } else { 0 })
                | (if rex_x { 0x02 } else { 0 })
                | (if rex_b { 0x01 } else { 0 });
            self.output.push(rex_byte);
        }

        // Emit mandatory prefix for SSE instructions (66, F3, F2)
        if encoding.mandatory_prefix != 0 && encoding.encoding_form == EncodingForm::Legacy {
            let prefix_byte = match encoding.mandatory_prefix {
                1 => prefixes::OPERAND_SIZE_OVERRIDE, // 0x66
                2 => prefixes::REP,                   // 0xF3
                3 => prefixes::REPNE,                 // 0xF2
                _ => 0,
            };
            if prefix_byte != 0 {
                self.output.push(prefix_byte);
            }
        }
    }

    // ========================================================================
    // Opcode byte encoding
    // ========================================================================

    /// Emit the opcode byte(s) for the instruction.
    fn encode_opcode_bytes(&mut self, encoding: &InstrEncodingInfo) {
        match encoding.opcode_map {
            0 => {
                // 1-byte opcode — just emit the byte
                self.output.push(encoding.base_opcode);
            }
            1 => {
                // 2-byte opcode — 0x0F escape + opcode
                self.output.push(0x0F);
                self.output.push(encoding.base_opcode);
            }
            2 => {
                // 3-byte opcode — 0x0F 0x38 escape + opcode
                self.output.push(0x0F);
                self.output.push(0x38);
                self.output.push(encoding.base_opcode);
            }
            3 => {
                // 3-byte opcode — 0x0F 0x3A escape + opcode
                self.output.push(0x0F);
                self.output.push(0x3A);
                self.output.push(encoding.base_opcode);
            }
            _ => {
                // Fallback for VEX/EVEX/XOP — the opcode byte is emitted after the prefix
                self.output.push(encoding.base_opcode);
            }
        }
    }

    // ========================================================================
    // ModR/M computation
    // ========================================================================

    /// Compute the ModR/M byte for the given instruction and operands.
    fn compute_modrm(&self, encoding: &InstrEncodingInfo, operands: &[X86Operand]) -> u8 {
        let mut mod_field_val: u8 = mod_field::REG_DIRECT;
        let mut reg_opcode: u8 = encoding.modrm_extension;
        let mut rm_val: u8 = 0;

        // Determine which operand goes to reg field (typically src) and which to r/m field (dst)
        // For most instructions: reg = src, r/m = dst
        // For store instructions: reg = src, r/m = mem
        // For immediate forms: r/m = dst, reg = opcode extension

        let dst_idx = 0usize;
        let src_idx = if operands.len() >= 2 { 1 } else { 0 };

        // Check if any operand is memory
        let has_mem = operands.iter().any(|op| matches!(op, X86Operand::Mem(_)));

        if has_mem {
            // Find the memory operand
            for (i, op) in operands.iter().enumerate() {
                if let X86Operand::Mem(mem) = op {
                    rm_val = self.get_rm_reg_field(mem.base);
                    mod_field_val = self.compute_mem_mod_field(mem);
                    break;
                }
            }
            // The register operand goes to the reg field
            for (i, op) in operands.iter().enumerate() {
                if let X86Operand::Reg(reg) = op {
                    if i != 0 || !has_mem {
                        if reg_opcode == 255 {
                            reg_opcode = self.get_reg_field(*reg) & 0x7;
                        }
                    }
                    break;
                }
            }
        } else if operands.len() >= 2 {
            // Register-register encoding
            if let X86Operand::Reg(dst) = &operands[dst_idx] {
                rm_val = self.get_reg_field(*dst) & 0x7;
            }
            if let X86Operand::Reg(src) = &operands[src_idx] {
                if reg_opcode == 255 {
                    reg_opcode = self.get_reg_field(*src) & 0x7;
                }
            }
        } else if operands.len() == 1 {
            if let X86Operand::Reg(reg) = &operands[0] {
                rm_val = self.get_reg_field(*reg) & 0x7;
            }
        }

        (mod_field_val << 6) | ((reg_opcode & 0x7) << 3) | (rm_val & 0x7)
    }

    /// Compute the Mod field for a memory operand.
    fn compute_mem_mod_field(&self, mem: &X86MemOperand) -> u8 {
        if mem.base == 0 && mem.index == 0 {
            // Absolute address — mod=0, rm=5
            mod_field::MEM_NO_DISP
        } else if mem.displacement == 0
            && mem.base != RBP
            && mem.base != R13
            && !mem.is_rip_relative()
        {
            mod_field::MEM_NO_DISP
        } else if mem.displacement >= -128 && mem.displacement <= 127 {
            mod_field::MEM_DISP8
        } else {
            mod_field::MEM_DISP32
        }
    }

    /// Get the r/m field value for a register.
    fn get_rm_reg_field(&self, reg: u16) -> u8 {
        self.get_reg_field(reg) & 0x7
    }

    // ========================================================================
    // SIB computation
    // ========================================================================

    /// Determine if a SIB byte is needed.
    fn needs_sib(&self, operands: &[X86Operand]) -> bool {
        for op in operands {
            if let X86Operand::Mem(mem) = op {
                if mem.index != 0 {
                    return true;
                }
                if mem.base == RSP || mem.base == R12 || mem.base == ESP {
                    return true;
                }
                // RBP without displacement requires SIB with disp32=0
                if mem.base == RBP || mem.base == R13 {
                    return true;
                }
                // RIP-relative needs SIB? No — RIP-relative uses ModR/M mod=0, rm=5
            }
        }
        false
    }

    /// Compute the SIB byte.
    fn compute_sib(&self, operands: &[X86Operand]) -> u8 {
        for op in operands {
            if let X86Operand::Mem(mem) = op {
                let scale_bits = match mem.scale {
                    2 => sib_byte::SCALE_2,
                    4 => sib_byte::SCALE_4,
                    8 => sib_byte::SCALE_8,
                    _ => sib_byte::SCALE_1,
                };

                let index_field = if mem.index == 0 {
                    sib_byte::NO_INDEX
                } else {
                    self.get_reg_field(mem.index) & 0x7
                };

                let base_field = if mem.base == 0 {
                    5 // disp32 with no base
                } else {
                    self.get_reg_field(mem.base) & 0x7
                };

                return sib_byte::build(scale_bits, index_field, base_field);
            }
        }
        0
    }

    // ========================================================================
    // Displacement encoding
    // ========================================================================

    /// Encode displacement for memory operands.
    fn encode_displacement(&mut self, operands: &[X86Operand]) {
        for op in operands {
            if let X86Operand::Mem(mem) = op {
                if mem.is_rip_relative() {
                    // Always use 32-bit displacement for RIP-relative
                    self.output
                        .extend_from_slice(&mem.displacement.to_le_bytes());
                    return;
                }

                if mem.displacement == 0 && mem.base != RBP && mem.base != R13 {
                    // No displacement needed
                    return;
                }

                if mem.displacement >= -128 && mem.displacement <= 127 {
                    self.output.push(mem.displacement as u8);
                } else {
                    self.output
                        .extend_from_slice(&mem.displacement.to_le_bytes());
                }
                return;
            }
        }
    }

    // ========================================================================
    // Immediate encoding
    // ========================================================================

    /// Encode immediate operand(s).
    fn encode_immediates(&mut self, operands: &[X86Operand]) {
        for op in operands {
            if let X86Operand::Imm(val) = op {
                // Determine immediate size from operand context
                let abs_val = val.unsigned_abs();
                if abs_val <= 0xFF && (*val as i8 as i64) == *val {
                    // Fits in signed 8-bit
                    self.output.push(*val as u8);
                } else if abs_val <= 0xFFFF_FFFF {
                    self.output.extend_from_slice(&(*val as i32).to_le_bytes());
                } else {
                    self.output.extend_from_slice(&val.to_le_bytes());
                }
                return; // Only one immediate for now
            }
        }
    }

    // ========================================================================
    // Register field helpers
    // ========================================================================

    /// Get the 3-bit register field (low 3 bits) for ModR/M and SIB.
    /// Extended bits (bit 3) are handled by REX/VEX.
    pub fn get_reg_field(&self, reg_id: u16) -> u8 {
        match reg_id {
            // 64-bit GPRs
            RAX..=R15 => (reg_id % 16) as u8,
            // 32-bit GPRs
            EAX..=R15D => (reg_id % 16) as u8,
            // 16-bit GPRs
            AX..=R15W => (reg_id % 16) as u8,
            // 8-bit GPRs
            AL..=R15B => {
                let base = reg_id % 16;
                if base >= 4 && reg_id != SPL && reg_id != BPL && reg_id != SIL && reg_id != DIL {
                    // AH, CH, DH, BH have special mapping
                    match reg_id {
                        4 => 4, // AH/SPL
                        5 => 5, // CH/BPL
                        6 => 6, // DH/SIL
                        7 => 7, // BH/DIL
                        _ => (reg_id % 8) as u8,
                    }
                } else {
                    base as u8
                }
            }
            // XMM
            XMM0..=XMM15 => (reg_id % 16) as u8,
            // YMM
            YMM0..=YMM15 => (reg_id % 16) as u8,
            // ZMM
            ZMM0..=ZMM15 => (reg_id % 16) as u8,
            // K registers
            K0..=K7 => (reg_id % 8) as u8,
            _ => 0,
        }
    }

    /// Get the reg field for a specific operand position.
    fn get_reg_field_for_operand(&self, operands: &[X86Operand], idx: usize) -> u8 {
        if idx < operands.len() {
            if let X86Operand::Reg(reg) = &operands[idx] {
                return self.get_reg_field(*reg);
            }
        }
        0
    }

    /// Check if a register ID is a 64-bit GPR.
    fn is_gpr64_register(&self, reg: u16) -> bool {
        (RAX..=R15).contains(&reg)
    }

    /// Determine vector length flag from operands.
    fn vector_length_from_operands(&self, operands: &[X86Operand]) -> bool {
        for op in operands {
            if let X86Operand::Reg(reg) = op {
                if (YMM0..=YMM15).contains(reg) {
                    return true; // 256-bit
                }
            }
        }
        false // 128-bit default
    }

    /// Determine vector length for AVX-512 (2-bit LL field).
    fn vector_length_512(&self, operands: &[X86Operand]) -> u8 {
        for op in operands {
            if let X86Operand::Reg(reg) = op {
                if (ZMM0..=ZMM31).contains(reg) {
                    return 2; // 512-bit
                }
                if (YMM0..=YMM31).contains(reg) {
                    return 1; // 256-bit
                }
            }
        }
        0 // 128-bit
    }

    // ========================================================================
    // Convenience encoding aliases
    // ========================================================================

    /// Create a NOP instruction.
    pub fn encode_nop(&mut self) -> Vec<u8> {
        self.output.clear();
        self.output.push(0x90);
        self.output.clone()
    }

    /// Create a 3-byte NOP.
    pub fn encode_nop3(&mut self) -> Vec<u8> {
        self.output.clear();
        self.output.push(0x0F);
        self.output.push(0x1F);
        self.output.push(0x00);
        self.output.clone()
    }

    /// Encode a direct call.
    pub fn encode_call(&mut self, target_offset: i32) -> Vec<u8> {
        self.output.clear();
        self.output.push(0xE8);
        self.output.extend_from_slice(&target_offset.to_le_bytes());
        self.output.clone()
    }

    /// Encode a simple register-to-register MOV.
    pub fn encode_mov_rr(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::MOVrr,
            &[X86Operand::Reg(dst), X86Operand::Reg(src)],
        )
    }

    /// Encode ADD reg, reg.
    pub fn encode_add_rr(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::ADD,
            &[X86Operand::Reg(dst), X86Operand::Reg(src)],
        )
    }

    /// Encode ADD reg, imm.
    pub fn encode_add_ri(&mut self, dst: u16, imm: i64) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::ADD,
            &[X86Operand::Reg(dst), X86Operand::Imm(imm)],
        )
    }

    /// Encode SUB reg, reg.
    pub fn encode_sub_rr(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::SUB,
            &[X86Operand::Reg(dst), X86Operand::Reg(src)],
        )
    }

    /// Encode AND reg, reg.
    pub fn encode_and_rr(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AND,
            &[X86Operand::Reg(dst), X86Operand::Reg(src)],
        )
    }

    /// Encode OR reg, reg.
    pub fn encode_or_rr(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::OR,
            &[X86Operand::Reg(dst), X86Operand::Reg(src)],
        )
    }

    /// Encode XOR reg, reg.
    pub fn encode_xor_rr(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::XOR,
            &[X86Operand::Reg(dst), X86Operand::Reg(src)],
        )
    }

    /// Encode CMP reg, reg.
    pub fn encode_cmp_rr(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::CMP,
            &[X86Operand::Reg(dst), X86Operand::Reg(src)],
        )
    }

    /// Encode RET.
    pub fn encode_ret(&mut self) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::RET, &[])
    }

    /// Encode a MOV with a memory destination.
    pub fn encode_mov_mr(&mut self, mem: X86MemOperand, src: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::MOVmr,
            &[X86Operand::Mem(mem), X86Operand::Reg(src)],
        )
    }

    /// Encode a MOV with a memory source.
    pub fn encode_mov_rm(&mut self, dst: u16, mem: X86MemOperand) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::MOVrm,
            &[X86Operand::Reg(dst), X86Operand::Mem(mem)],
        )
    }

    /// Encode VADDPS (3-operand AVX).
    pub fn encode_vaddps(&mut self, dst: u16, src1: u16, src2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VADDPS,
            &[
                X86Operand::Reg(dst),
                X86Operand::Reg(src1),
                X86Operand::Reg(src2),
            ],
        )
    }

    /// Encode AESENC.
    pub fn encode_aesenc(&mut self, dst: u16, src: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AESENC,
            &[X86Operand::Reg(dst), X86Operand::Reg(src)],
        )
    }

    /// Encode SHA256RNDS2.
    pub fn encode_sha256rnds2(&mut self, dst: u16, src1: u16, src2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::SHA256RNDS2,
            &[
                X86Operand::Reg(dst),
                X86Operand::Reg(src1),
                X86Operand::Reg(src2),
            ],
        )
    }

    // ========================================================================
    // VSIB addressing (for gather/scatter instructions)
    // ========================================================================

    /// Encode a VGATHERDD instruction with VSIB addressing.
    ///
    /// VSIB (Vector SIB) allows using XMM/YMM/ZMM registers as indices
    /// in gather/scatter operations. The SIB byte is constructed similarly
    /// to regular SIB but the index field references a vector register.
    pub fn encode_vgatherdd_vsib(&mut self, dst: u16, vsib_mem: X86MemOperand) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VPGATHERDD,
            &[X86Operand::Reg(dst), X86Operand::Mem(vsib_mem)],
        )
    }

    /// Encode a VPGATHERDQ with VSIB.
    pub fn encode_vgatherdq_vsib(&mut self, dst: u16, vsib_mem: X86MemOperand) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VPGATHERDQ,
            &[X86Operand::Reg(dst), X86Operand::Mem(vsib_mem)],
        )
    }
    // === AVX-512 VP2INTERSECT encoding ===
    pub fn encode_vp2intersectd(&mut self, k: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VP2INTERSECTD,
            &[X86Operand::Reg(k), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    pub fn encode_vp2intersectq(&mut self, k: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VP2INTERSECTQ,
            &[X86Operand::Reg(k), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    // === AVX-512 FP16 encoding ===
    pub fn encode_vaddph(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VADDPH,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    pub fn encode_vmulph(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VMULPH,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    pub fn encode_vdivph(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VDIVPH,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    pub fn encode_vsubph(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VSUBPH,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    // === AVX-512 BF16 encoding ===
    pub fn encode_vcvtne2ps2bf16(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VCVTNE2PS2BF16,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    pub fn encode_vdpbf16ps(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VDPBF16PS,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    // === AMX tile config encoding ===
    pub fn encode_ldtilecfg(&mut self, mem: X86MemOperand) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::LDTILECFG, &[X86Operand::Mem(mem)])
    }
    pub fn encode_sttilecfg(&mut self, mem: X86MemOperand) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::STTILECFG, &[X86Operand::Mem(mem)])
    }
    pub fn encode_tilerelease(&mut self) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::TILERELEASE, &[])
    }
    pub fn encode_tilezero(&mut self, t: u16) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::TILEZERO, &[X86Operand::Reg(t)])
    }
    // === AMX tile data encoding ===
    pub fn encode_tileloadd(&mut self, t: u16, mem: X86MemOperand) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::TILELOADD,
            &[X86Operand::Reg(t), X86Operand::Mem(mem)],
        )
    }
    pub fn encode_tilestored(&mut self, mem: X86MemOperand, t: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::TILESTORED,
            &[X86Operand::Mem(mem), X86Operand::Reg(t)],
        )
    }
    // === AMX compute encoding ===
    pub fn encode_tdpbssd(&mut self, td: u16, ts1: u16, ts2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::TDPBSSD,
            &[
                X86Operand::Reg(td),
                X86Operand::Reg(ts1),
                X86Operand::Reg(ts2),
            ],
        )
    }
    pub fn encode_tdpbsud(&mut self, td: u16, ts1: u16, ts2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::TDPBSUD,
            &[
                X86Operand::Reg(td),
                X86Operand::Reg(ts1),
                X86Operand::Reg(ts2),
            ],
        )
    }
    pub fn encode_tdpbusd(&mut self, td: u16, ts1: u16, ts2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::TDPBUSD,
            &[
                X86Operand::Reg(td),
                X86Operand::Reg(ts1),
                X86Operand::Reg(ts2),
            ],
        )
    }
    pub fn encode_tdpbuud(&mut self, td: u16, ts1: u16, ts2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::TDPBUUD,
            &[
                X86Operand::Reg(td),
                X86Operand::Reg(ts1),
                X86Operand::Reg(ts2),
            ],
        )
    }
    pub fn encode_tdpbf16ps(&mut self, td: u16, ts1: u16, ts2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::TDPBF16PS,
            &[
                X86Operand::Reg(td),
                X86Operand::Reg(ts1),
                X86Operand::Reg(ts2),
            ],
        )
    }
    pub fn encode_tdpfp16ps(&mut self, td: u16, ts1: u16, ts2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::TDPFP16PS,
            &[
                X86Operand::Reg(td),
                X86Operand::Reg(ts1),
                X86Operand::Reg(ts2),
            ],
        )
    }
    // === KEYLOCKER encoding ===
    pub fn encode_loadiwkey(&mut self, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::LOADIWKEY,
            &[X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    pub fn encode_aesenc128kl(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AESENC128KL,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_aesdec128kl(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AESDEC128KL,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_encodekey128(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::ENCODEKEY128,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    // === HRESET, UINTR, FRED encoding ===
    pub fn encode_hreset(&mut self, imm: u8) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::HRESET, &[X86Operand::Imm(imm as i64)])
    }
    pub fn encode_senduip(&mut self, r: u16) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::SENDUIP, &[X86Operand::Reg(r)])
    }
    pub fn encode_uiret(&mut self) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::UIRET, &[])
    }
    pub fn encode_erets(&mut self) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::ERETS, &[])
    }
    pub fn encode_eretu(&mut self) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::ERETU, &[])
    }
    pub fn encode_lkgs(&mut self, r: u16) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::LKGS, &[X86Operand::Reg(r)])
    }
    // === CMPCCXADD, RAO-INT, WRMSRNS encoding ===
    pub fn encode_cmpccxadd(&mut self, mem: X86MemOperand, r: u16, cc: u8) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::CMPCCXADD,
            &[
                X86Operand::Mem(mem),
                X86Operand::Reg(r),
                X86Operand::Imm(cc as i64),
            ],
        )
    }
    pub fn encode_aadd(&mut self, mem: X86MemOperand, r: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AADD,
            &[X86Operand::Mem(mem), X86Operand::Reg(r)],
        )
    }
    pub fn encode_aand(&mut self, mem: X86MemOperand, r: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AAND,
            &[X86Operand::Mem(mem), X86Operand::Reg(r)],
        )
    }
    pub fn encode_aor(&mut self, mem: X86MemOperand, r: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AOR,
            &[X86Operand::Mem(mem), X86Operand::Reg(r)],
        )
    }
    pub fn encode_axor(&mut self, mem: X86MemOperand, r: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AXOR,
            &[X86Operand::Mem(mem), X86Operand::Reg(r)],
        )
    }
    pub fn encode_wrmsrns(&mut self) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::WRMSRNS, &[])
    }

    // ========================================================================
    // F16C: Half Precision Conversion
    // ========================================================================
    pub fn encode_vcvtph2ps(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VCVTPH2PS,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_vcvtps2ph(&mut self, d: u16, s: u16, imm: u8) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VCVTPS2PH,
            &[
                X86Operand::Reg(d),
                X86Operand::Reg(s),
                X86Operand::Imm(imm as i64),
            ],
        )
    }

    // ========================================================================
    // RDRAND / RDSEED
    // ========================================================================
    pub fn encode_rdrand16(&mut self, d: u16) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::RDRAND, &[X86Operand::Reg(d)])
    }
    pub fn encode_rdrand32(&mut self, d: u16) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::RDRAND, &[X86Operand::Reg(d)])
    }
    pub fn encode_rdrand64(&mut self, d: u16) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::RDRAND, &[X86Operand::Reg(d)])
    }
    pub fn encode_rdseed16(&mut self, d: u16) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::RDSEED, &[X86Operand::Reg(d)])
    }
    pub fn encode_rdseed32(&mut self, d: u16) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::RDSEED, &[X86Operand::Reg(d)])
    }
    pub fn encode_rdseed64(&mut self, d: u16) -> Vec<u8> {
        self.encode_instruction(X86FullOpcode::RDSEED, &[X86Operand::Reg(d)])
    }

    // ========================================================================
    // AES-NI: Advanced Encryption Standard
    // ========================================================================
    pub fn encode_aesenclast(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AESENCLAST,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_aesdec(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AESDEC,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_aesdeclast(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AESDECLAST,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_aesimc(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AESIMC,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_aeskeygenassist(&mut self, d: u16, s: u16, imm: u8) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::AESKEYGENASSIST,
            &[
                X86Operand::Reg(d),
                X86Operand::Reg(s),
                X86Operand::Imm(imm as i64),
            ],
        )
    }

    // ========================================================================
    // SHA Extensions
    // ========================================================================
    pub fn encode_sha1rnds4(&mut self, d: u16, s: u16, imm: u8) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::SHA1RNDS4,
            &[
                X86Operand::Reg(d),
                X86Operand::Reg(s),
                X86Operand::Imm(imm as i64),
            ],
        )
    }
    pub fn encode_sha1nexte(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::SHA1NEXTE,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_sha1msg1(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::SHA1MSG1,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_sha1msg2(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::SHA1MSG2,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_sha256msg1(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::SHA256MSG1,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }
    pub fn encode_sha256msg2(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::SHA256MSG2,
            &[X86Operand::Reg(d), X86Operand::Reg(s)],
        )
    }

    // ========================================================================
    // GFNI: Galois Field New Instructions (VEX-encoded via Z variants)
    // ========================================================================
    pub fn encode_vgf2p8affineqb(&mut self, d: u16, s1: u16, s2: u16, imm: u8) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VGF2P8AFFINEQB_Z,
            &[
                X86Operand::Reg(d),
                X86Operand::Reg(s1),
                X86Operand::Reg(s2),
                X86Operand::Imm(imm as i64),
            ],
        )
    }
    pub fn encode_vgf2p8affineinvqb(&mut self, d: u16, s1: u16, s2: u16, imm: u8) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VGF2P8AFFINEINVQB_Z,
            &[
                X86Operand::Reg(d),
                X86Operand::Reg(s1),
                X86Operand::Reg(s2),
                X86Operand::Imm(imm as i64),
            ],
        )
    }
    pub fn encode_vgf2p8mulb(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VGF2P8MULB_Z,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }

    // ========================================================================
    // VAES: Vector AES (via Z variants)
    // ========================================================================
    pub fn encode_vaesenc(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VAESENC_Z,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    pub fn encode_vaesenclast(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VAESENCLAST_Z,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    pub fn encode_vaesdec(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VAESDEC_Z,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }
    pub fn encode_vaesdeclast(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VAESDECLAST_Z,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }

    // ========================================================================
    // VPCLMULQDQ: Vector PCLMULQDQ (via Z variant)
    // ========================================================================
    pub fn encode_vpclmulqdq(&mut self, d: u16, s1: u16, s2: u16, imm: u8) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VPCLMULQDQ_Z,
            &[
                X86Operand::Reg(d),
                X86Operand::Reg(s1),
                X86Operand::Reg(s2),
                X86Operand::Imm(imm as i64),
            ],
        )
    }

    // ========================================================================
    // AVX-VNNI: Vector Neural Network Instructions
    // ========================================================================
    pub fn encode_vpdpbusd(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.128.66.0F38.W0 50 /r: VPDPBUSD xmm1, xmm2, xmm3/m128
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x79);
        bytes.push(0x50);
        let modrm: u8 = (0xC0 | ((d & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }
    pub fn encode_vpdpbusds(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.128.66.0F38.W0 51 /r: VPDPBUSDS xmm1, xmm2, xmm3/m128
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x79);
        bytes.push(0x51);
        let modrm: u8 = (0xC0 | ((d & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }
    pub fn encode_vpdpwssd(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.128.66.0F38.W0 52 /r: VPDPWSSD xmm1, xmm2, xmm3/m128
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x79);
        bytes.push(0x52);
        let modrm: u8 = (0xC0 | ((d & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }
    pub fn encode_vpdpwssds(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.128.66.0F38.W0 53 /r: VPDPWSSDS xmm1, xmm2, xmm3/m128
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x79);
        bytes.push(0x53);
        let modrm: u8 = (0xC0 | ((d & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }

    // ========================================================================
    // AVX-IFMA: Integer Fused Multiply-Add
    // ========================================================================
    pub fn encode_vpmadd52luq(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.128.66.0F38.W0 B4 /r: VPMADD52LUQ xmm1, xmm2, xmm3/m128
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x79);
        bytes.push(0xB4);
        let modrm: u8 = (0xC0 | ((d & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }
    pub fn encode_vpmadd52huq(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.128.66.0F38.W0 B5 /r: VPMADD52HUQ xmm1, xmm2, xmm3/m128
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x79);
        bytes.push(0xB5);
        let modrm: u8 = (0xC0 | ((d & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }

    // ========================================================================
    // AVX-NE-CONVERT: BF16/FP16 Convert
    // ========================================================================
    pub fn encode_vbcstnebf162ps(&mut self, d: u16, s: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.F3.0F38.W0 B0 /r: VBCSTNEBF162PS ymm1, ymm2/m256
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0xB0);
        let modrm: u8 = (0xC0 | ((d & 7) << 3) | (s & 7)) as u8;
        bytes.push(modrm);
        bytes
    }
    pub fn encode_vbcstnesh2ps(&mut self, d: u16, s: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.66.0F38.W0 B1 /r: VBCSTNESH2PS ymm1, ymm2/m256
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0xB1);
        let modrm: u8 = (0xC0 | ((d & 7) << 3) | (s & 7)) as u8;
        bytes.push(modrm);
        bytes
    }
    pub fn encode_vcvtneeph2ps(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        self.encode_instruction(
            X86FullOpcode::VCVTNEEPH2PS,
            &[X86Operand::Reg(d), X86Operand::Reg(s1), X86Operand::Reg(s2)],
        )
    }

    // ========================================================================
    // 256-bit VEX encoding helpers (ymm variants)
    // ========================================================================

    /// Encode VBCSTNEBF162PS with 256-bit VEX prefix.
    pub fn encode_vbcstnebf162ps_ymm(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_vbcstnebf162ps(d, s)
    }

    /// Encode VBCSTNESH2PS with 256-bit VEX prefix.
    pub fn encode_vbcstnesh2ps_ymm(&mut self, d: u16, s: u16) -> Vec<u8> {
        self.encode_vbcstnesh2ps(d, s)
    }

    /// Encode VPDPBUSD with 256-bit VEX prefix (YMM).
    pub fn encode_vpdpbusd_ymm(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.66.0F38.W0 50 /r: VPDPBUSD ymm1, ymm2, ymm3/m256
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0x50);
        let modrm: u8 = (0xC0 | ((s1 & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }

    /// Encode VPDPWSSD with 256-bit VEX prefix (YMM).
    pub fn encode_vpdpwssd_ymm(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.66.0F38.W0 52 /r: VPDPWSSD ymm1, ymm2, ymm3/m256
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0x52);
        let modrm: u8 = (0xC0 | ((s1 & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }

    /// Encode VPMADD52LUQ with 256-bit VEX prefix (YMM).
    pub fn encode_vpmadd52luq_ymm(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.66.0F38.W0 B4 /r: VPMADD52LUQ ymm1, ymm2, ymm3/m256
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0xB4);
        let modrm: u8 = (0xC0 | ((s1 & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }

    /// Encode VPMADD52HUQ with 256-bit VEX prefix (YMM).
    pub fn encode_vpmadd52huq_ymm(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.66.0F38.W0 B5 /r: VPMADD52HUQ ymm1, ymm2, ymm3/m256
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0xB5);
        let modrm: u8 = (0xC0 | ((s1 & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }

    /// Encode VGF2P8AFFINEQB with 256-bit VEX prefix (YMM).
    pub fn encode_vgf2p8affineqb_ymm(&mut self, d: u16, s1: u16, s2: u16, imm: u8) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.66.0F3A.W0 CE /r /ib: VGF2P8AFFINEQB ymm1, ymm2, ymm3/m256, imm8
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0xCE);
        let modrm: u8 = (0xC0 | ((s1 & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes.push(imm);
        bytes
    }

    /// Encode VGF2P8MULB with 256-bit VEX prefix (YMM).
    pub fn encode_vgf2p8mulb_ymm(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.66.0F38.W0 CF /r: VGF2P8MULB ymm1, ymm2, ymm3/m256
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0xCF);
        let modrm: u8 = (0xC0 | ((s1 & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }

    /// Encode VAESENC with 256-bit VEX prefix (YMM).
    pub fn encode_vaesenc_ymm(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.66.0F38.W0 DC /r: VAESENC ymm1, ymm2, ymm3/m256
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0xDC);
        let modrm: u8 = (0xC0 | ((s1 & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }

    /// Encode VAESDEC with 256-bit VEX prefix (YMM).
    pub fn encode_vaesdec_ymm(&mut self, d: u16, s1: u16, s2: u16) -> Vec<u8> {
        let mut bytes = Vec::new();
        // VEX.256.66.0F38.W0 DE /r: VAESDEC ymm1, ymm2, ymm3/m256
        bytes.push(0xC4);
        bytes.push(0xE2);
        bytes.push(0x7D);
        bytes.push(0xDE);
        let modrm: u8 = (0xC0 | ((s1 & 7) << 3) | (s2 & 7)) as u8;
        bytes.push(modrm);
        bytes
    }

    // ========================================================================
    // RIP-relative helper
    // ========================================================================

    /// Create a RIP-relative memory operand (for position-independent code).
    pub fn rip_relative(displacement: i32) -> X86MemOperand {
        X86MemOperand {
            base: RIP,
            index: 0,
            scale: 0,
            displacement,
            segment: 0,
        }
    }
}

// ============================================================================
// APX REX2 Prefix Encoding
// ============================================================================

/// REX2 prefix encoder for APX instructions.
/// REX2 (0xD5) is an 8-bit extended prefix that allows encoding of
/// up to 32 GPRs (r0-r31) and 32 vector registers.
pub mod apx_rex2_encoder {
    use super::*;

    /// REX2 prefix byte.
    pub const REX2_PREFIX: u8 = 0xD5;

    /// Build a REX2 byte.
    /// Layout: [M0(1) | R4(1) | X4(1) | B4(1) | W(1) | R3(1) | X3(1) | B3(1)]
    pub fn encode_rex2(
        w: bool,
        r: u8, // reg field (5 bits: r4..r0)
        x: u8, // index field (5 bits: x4..x0)
        b: u8, // base/rm field (5 bits: b4..b0)
    ) -> u8 {
        let r4 = (r >> 4) & 1;
        let r3 = (r >> 3) & 1;
        let x4 = (x >> 4) & 1;
        let x3 = (x >> 3) & 1;
        let b4 = (b >> 4) & 1;
        let b3 = (b >> 3) & 1;
        (r4 << 6) | (x4 << 5) | (b4 << 4) | ((w as u8) << 3) | (r3 << 2) | (x3 << 1) | b3
    }

    /// Check if REX2 is needed.
    pub fn needs_rex2(reg: u8, rm: u8, index: Option<u8>) -> bool {
        reg >= 16 || rm >= 16 || index.map_or(false, |i| i >= 16)
    }

    /// Check if any register needs REX2 in a 3-operand form.
    pub fn needs_rex2_3op(dst: u8, src1: u8, src2: u8) -> bool {
        dst >= 16 || src1 >= 16 || src2 >= 16
    }

    /// Encode the full REX2 prefix sequence (returns [REX2] or [REX2, byte]).
    pub fn encode_prefix(w: bool, reg: u8, rm: u8) -> Vec<u8> {
        let needs_ext = reg >= 16 || rm >= 16;
        if !needs_ext && !w {
            return Vec::new();
        }
        if needs_ext {
            vec![REX2_PREFIX, encode_rex2(w, reg, 0, rm)]
        } else {
            vec![0x40 | ((w as u8) << 3) | (((reg >> 3) & 1) << 2) | ((rm >> 3) & 1)]
        }
    }

    /// Encode REX2 prefix for a memory operand with index.
    pub fn encode_prefix_mem(w: bool, reg: u8, base: u8, index: u8) -> Vec<u8> {
        let needs_ext = reg >= 16 || base >= 16 || index >= 16;
        if !needs_ext && !w {
            return Vec::new();
        }
        if needs_ext {
            vec![REX2_PREFIX, encode_rex2(w, reg, index, base)]
        } else {
            let rex = 0x40
                | ((w as u8) << 3)
                | (((reg >> 3) & 1) << 2)
                | (((index >> 3) & 1) << 1)
                | ((base >> 3) & 1);
            vec![rex]
        }
    }
}

// ============================================================================
// EVEX Extended Encoding for APX
// ============================================================================

/// EVEX prefix encoder supporting APX extended registers.
/// EVEX is a 4-byte prefix extension of VEX for AVX-512 and APX.
pub mod apx_evex_encoder {
    use super::*;

    /// EVEX prefix byte 1: 0x62.
    pub const EVEX_PREFIX: u8 = 0x62;

    /// Build a 4-byte EVEX prefix.
    ///
    /// EVEX layout:
    ///   Byte 0: 0x62 (fixed)
    ///   Byte 1: [R(1)|X(1)|B(1)|R'(1)|0|0|m(2)]
    ///   Byte 2: [W(1)|v'(4)|1|p(2)]
    ///   Byte 3: [z(1)|L'(1)|L(1)|b(1)|V'(1)|a(3)]
    ///
    /// Where R' is the 5th bit of the reg field (for EGPR),
    /// v' is the 5th bit of the vvvv field,
    /// and V' is adjustment for the V bit.
    pub fn build_evex(
        r: bool,
        x: bool,
        b: bool,
        r_prime: bool, // R' (5th bit of reg)
        mmm: u8,       // opcode map (0-7)
        w: bool,
        vvvv: u8,      // source register (4 bits)
        v_prime: bool, // v' (5th bit of vvvv)
        pp: u8,        // mandatory prefix
        z: bool,       // zeroing mask
        ll: u8,        // vector length (0=128, 1=256, 2=512)
        b_bit: bool,   // broadcast/rounding
        aaa: u8,       // opmask register (0-7)
    ) -> [u8; 4] {
        let byte1 = ((!r as u8) << 7)
            | ((!x as u8) << 6)
            | ((!b as u8) << 5)
            | ((r_prime as u8) << 4)
            | (mmm & 0x7);

        let byte2 = ((w as u8) << 7)
            | ((!vvvv & 0xF) << 3)
            | (1 << 2) // fixed bit
            | (pp & 0x3);

        let byte3 = ((z as u8) << 7)
            | (((ll >> 1) & 1) << 6) // L'
            | (((ll >> 0) & 1) << 5) // L
            | ((b_bit as u8) << 4)
            | ((v_prime as u8) << 3)
            | (aaa & 0x7);

        [EVEX_PREFIX, byte1, byte2, byte3]
    }

    /// Build EVEX for a register-to-register operation with EGPR.
    pub fn build_evex_rr(
        opcode_map: u8,
        w: bool,
        vvvv: u8,
        pp: u8,
        reg: u8,
        rm: u8,
        ll: u8,
    ) -> [u8; 4] {
        let r = (reg >> 3) & 1 != 0;
        let b = (rm >> 3) & 1 != 0;
        let r_prime = (reg >> 4) & 1 != 0;
        let v_prime = (vvvv >> 4) & 1 != 0;

        build_evex(
            r,
            false,
            b,
            r_prime,
            opcode_map,
            w,
            vvvv & 0xF,
            v_prime,
            pp,
            false,
            ll,
            false,
            0,
        )
    }

    /// Build EVEX for a memory operation.
    pub fn build_evex_mem(
        opcode_map: u8,
        w: bool,
        vvvv: u8,
        pp: u8,
        reg: u8,
        base: u8,
        index: u8,
        ll: u8,
        disp_size: u8, // disp8*N scale: 1,2,4,8,16,32,64
    ) -> [u8; 4] {
        let r = (reg >> 3) & 1 != 0;
        let x = (index >> 3) & 1 != 0;
        let b = (base >> 3) & 1 != 0;
        let r_prime = (reg >> 4) & 1 != 0;
        let v_prime = (vvvv >> 4) & 1 != 0;

        let ll_encoded = match disp_size {
            1 | 2 | 4 => 0,
            8 | 16 => 1,
            32 | 64 => 2,
            _ => 0,
        };

        build_evex(
            r,
            x,
            b,
            r_prime,
            opcode_map,
            w,
            vvvv & 0xF,
            v_prime,
            pp,
            false,
            ll_encoded,
            false,
            0,
        )
    }
}

// ============================================================================
// VEX Encoding for 3-Operand APX Forms
// ============================================================================

/// VEX prefix encoder for 3-operand instructions (AVX/APX).
pub mod apx_vex_encoder {
    use super::*;

    /// 3-byte VEX prefix: 0xC4.
    pub const VEX3_PREFIX: u8 = 0xC4;

    /// 2-byte VEX prefix: 0xC5.
    pub const VEX2_PREFIX: u8 = 0xC5;

    /// Build a 3-byte VEX prefix for APX 3-operand forms.
    pub fn build_vex3(
        r: bool,
        x: bool,
        b: bool,
        mmmmm: u8,
        w: bool,
        vvvv: u8,
        l: bool,
        pp: u8,
    ) -> [u8; 3] {
        let byte1 = ((!r as u8) << 7) | ((!x as u8) << 6) | ((!b as u8) << 5) | (mmmmm & 0x1F);

        let byte2 = ((w as u8) << 7) | ((!vvvv & 0xF) << 3) | ((l as u8) << 2) | (pp & 0x3);

        [VEX3_PREFIX, byte1, byte2]
    }

    /// Build a 2-byte VEX prefix.
    pub fn build_vex2(r: bool, vvvv: u8, l: bool, pp: u8) -> [u8; 2] {
        let byte1 = ((!r as u8) << 7) | ((!vvvv & 0xF) << 3) | ((l as u8) << 2) | (pp & 0x3);
        [VEX2_PREFIX, byte1]
    }

    /// Check if VEX encoding is preferred over legacy for APX operations.
    pub fn should_use_vex(num_operands: u8, has_imm: bool) -> bool {
        num_operands >= 3 || has_imm
    }
}

// ============================================================================
// XOP Encoding for AMD-Specific Instructions
// ============================================================================

/// XOP prefix encoder for AMD XOP instructions (Bulldozer/Piledriver).
/// XOP uses the same format as VEX3 but with the 0x8F prefix byte.
pub mod xop_encoder {
    use super::*;

    /// XOP prefix byte: 0x8F.
    pub const XOP_PREFIX: u8 = 0x8F;

    /// Build a 3-byte XOP prefix.
    pub fn build_xop(
        r: bool,
        x: bool,
        b: bool,
        mmmmm: u8, // XOP opcode map
        w: bool,
        vvvv: u8,
        l: bool,
        pp: u8,
    ) -> [u8; 3] {
        let byte1 = ((!r as u8) << 7) | ((!x as u8) << 6) | ((!b as u8) << 5) | (mmmmm & 0x1F);

        let byte2 = ((w as u8) << 7) | ((!vvvv & 0xF) << 3) | ((l as u8) << 2) | (pp & 0x3);

        [XOP_PREFIX, byte1, byte2]
    }

    /// AMD XOP opcode maps.
    pub mod xop_maps {
        /// XOP map 8 (integer instructions).
        pub const XOP_MAP8: u8 = 8;
        /// XOP map 9 (integer instructions).
        pub const XOP_MAP9: u8 = 9;
        /// XOP map 10 (floating-point instructions).
        pub const XOP_MAP10: u8 = 10;
    }
}

// ============================================================================
// ModR/M Encoding with EGPR Support
// ============================================================================

/// ModR/M encoder supporting EGPR (r16-r31) via REX2.
#[derive(Debug, Clone)]
pub struct ModRMEncoder {
    /// The mode field (bits 7-6).
    pub mod_: u8,
    /// The reg/opcode field (bits 5-3).
    pub reg: u8,
    /// The r/m field (bits 2-0).
    pub rm: u8,
    /// Extended bits from REX/REX2 for reg and rm.
    pub rex_r: bool, // 4th bit of reg
    pub rex_b: bool,   // 4th bit of rm
    pub rex2_r4: bool, // 5th bit of reg (EGPR)
    pub rex2_b4: bool, // 5th bit of rm (EGPR)
}

impl ModRMEncoder {
    /// Create a ModR/M byte for register-direct mode (mod=3).
    pub fn reg_direct(reg: u8, rm: u8) -> Self {
        Self {
            mod_: 3,
            reg: reg & 0x7,
            rm: rm & 0x7,
            rex_r: (reg >> 3) & 1 != 0,
            rex_b: (rm >> 3) & 1 != 0,
            rex2_r4: (reg >> 4) & 1 != 0,
            rex2_b4: (rm >> 4) & 1 != 0,
        }
    }

    /// Create a ModR/M for memory with no displacement (mod=0).
    pub fn mem_no_disp(reg: u8, rm: u8) -> Self {
        Self {
            mod_: 0,
            reg: reg & 0x7,
            rm: rm & 0x7,
            rex_r: (reg >> 3) & 1 != 0,
            rex_b: (rm >> 3) & 1 != 0,
            rex2_r4: (reg >> 4) & 1 != 0,
            rex2_b4: (rm >> 4) & 1 != 0,
        }
    }

    /// Create ModR/M for memory with 8-bit displacement (mod=1).
    pub fn mem_disp8(reg: u8, rm: u8) -> Self {
        Self {
            mod_: 1,
            reg: reg & 0x7,
            rm: rm & 0x7,
            rex_r: (reg >> 3) & 1 != 0,
            rex_b: (rm >> 3) & 1 != 0,
            rex2_r4: (reg >> 4) & 1 != 0,
            rex2_b4: (rm >> 4) & 1 != 0,
        }
    }

    /// Create ModR/M for memory with 32-bit displacement (mod=2).
    pub fn mem_disp32(reg: u8, rm: u8) -> Self {
        Self {
            mod_: 2,
            reg: reg & 0x7,
            rm: rm & 0x7,
            rex_r: (reg >> 3) & 1 != 0,
            rex_b: (rm >> 3) & 1 != 0,
            rex2_r4: (reg >> 4) & 1 != 0,
            rex2_b4: (rm >> 4) & 1 != 0,
        }
    }

    /// Encode the ModR/M byte.
    pub fn encode(&self) -> u8 {
        (self.mod_ << 6) | ((self.reg & 0x7) << 3) | (self.rm & 0x7)
    }

    /// Get the full 5-bit register number.
    pub fn full_reg(&self) -> u8 {
        self.reg | ((self.rex_r as u8) << 3) | ((self.rex2_r4 as u8) << 4)
    }

    /// Get the full 5-bit rm number.
    pub fn full_rm(&self) -> u8 {
        self.rm | ((self.rex_b as u8) << 3) | ((self.rex2_b4 as u8) << 4)
    }

    /// Check if REX2 is needed for this ModR/M.
    pub fn needs_rex2(&self) -> bool {
        self.rex2_r4 || self.rex2_b4
    }
}

// ============================================================================
// SIB Byte Encoding with EGPR
// ============================================================================

/// SIB byte encoder with EGPR support.
#[derive(Debug, Clone)]
pub struct SIBEncoder {
    /// Scale factor (bits 7-6): 0=1, 1=2, 2=4, 3=8.
    pub scale: u8,
    /// Index register (bits 5-3).
    pub index: u8,
    /// Base register (bits 2-0).
    pub base: u8,
    /// Extended index bit (REX.X or REX2.X4).
    pub rex_x: bool,
    pub rex2_x4: bool,
}

impl SIBEncoder {
    /// Create a SIB with no index (scale=0, index=ESP/RSP encoding 4).
    pub fn no_index(base: u8) -> Self {
        Self {
            scale: 0,
            index: 4, // special: no index
            base: base & 0x7,
            rex_x: false,
            rex2_x4: false,
        }
    }

    /// Create a SIB with index and scale.
    pub fn with_index(base: u8, index: u8, scale: u8) -> Self {
        assert!(scale == 1 || scale == 2 || scale == 4 || scale == 8);
        let scale_bits = match scale {
            1 => 0,
            2 => 1,
            4 => 2,
            8 => 3,
            _ => 0,
        };
        Self {
            scale: scale_bits,
            index: index & 0x7,
            base: base & 0x7,
            rex_x: (index >> 3) & 1 != 0,
            rex2_x4: (index >> 4) & 1 != 0,
        }
    }

    /// Create a SIB for RIP-relative addressing (base=5, index=4).
    pub fn rip_relative() -> Self {
        Self {
            scale: 0,
            index: 4,
            base: 5,
            rex_x: false,
            rex2_x4: false,
        }
    }

    /// Encode the SIB byte.
    pub fn encode(&self) -> u8 {
        (self.scale << 6) | ((self.index & 0x7) << 3) | (self.base & 0x7)
    }

    /// Check if this SIB requires REX2.
    pub fn needs_rex2(&self) -> bool {
        self.rex2_x4
    }
}

// ============================================================================
// Displacement Encoding: disp8, disp32, compressed disp8*N
// ============================================================================

/// Displacement encoder supporting all sizes and compressed forms.
#[derive(Debug, Clone)]
pub struct DisplacementEncoder {
    /// The displacement value.
    pub value: i64,
    /// The size of the displacement in bytes: 1, 2, 4.
    pub size: u8,
    /// For EVEX compressed displacements: the N multiplier.
    pub evex_compression_n: u8,
}

impl DisplacementEncoder {
    /// Create a disp8.
    pub fn disp8(value: i8) -> Self {
        Self {
            value: value as i64,
            size: 1,
            evex_compression_n: 1,
        }
    }

    /// Create a disp16.
    pub fn disp16(value: i16) -> Self {
        Self {
            value: value as i64,
            size: 2,
            evex_compression_n: 1,
        }
    }

    /// Create a disp32.
    pub fn disp32(value: i32) -> Self {
        Self {
            value: value as i64,
            size: 4,
            evex_compression_n: 1,
        }
    }

    /// Create a compressed EVEX displacement (disp8 * N).
    pub fn evex_compressed(value: i64, n: u8) -> Self {
        assert!(n == 1 || n == 2 || n == 4 || n == 8 || n == 16 || n == 32 || n == 64);
        let compressed = value / n as i64;
        assert!(
            compressed >= -128 && compressed <= 127,
            "compressed disp out of range"
        );
        Self {
            value: compressed,
            size: 1,
            evex_compression_n: n,
        }
    }

    /// Encode as bytes.
    pub fn encode(&self) -> Vec<u8> {
        match self.size {
            1 => vec![self.value as u8],
            2 => {
                let v = self.value as u16;
                vec![v as u8, (v >> 8) as u8]
            }
            4 => {
                let v = self.value as u32;
                vec![v as u8, (v >> 8) as u8, (v >> 16) as u8, (v >> 24) as u8]
            }
            _ => vec![self.value as u8],
        }
    }

    /// Get the actual memory displacement (uncompressed).
    pub fn effective_disp(&self) -> i64 {
        if self.evex_compression_n > 1 {
            self.value * self.evex_compression_n as i64
        } else {
            self.value
        }
    }

    /// Check if this displacement fits in a sign-extended disp8.
    pub fn fits_in_disp8(&self) -> bool {
        let eff = self.effective_disp();
        eff >= -128 && eff <= 127
    }
}

// ============================================================================
// Immediate Encoding: imm8-imm64 with Sign Extension
// ============================================================================

/// Immediate value encoder with proper sign extension.
#[derive(Debug, Clone)]
pub struct ImmediateEncoder {
    /// The immediate value (as i64 for all sizes).
    pub value: i64,
    /// Size in bytes: 1, 2, 4, or 8.
    pub size: u8,
    /// Whether to sign-extend a smaller immediate.
    pub sign_extend: bool,
}

impl ImmediateEncoder {
    /// Create an imm8.
    pub fn imm8(value: i8) -> Self {
        Self {
            value: value as i64,
            size: 1,
            sign_extend: false,
        }
    }

    /// Create an imm16.
    pub fn imm16(value: i16) -> Self {
        Self {
            value: value as i64,
            size: 2,
            sign_extend: false,
        }
    }

    /// Create an imm32.
    pub fn imm32(value: i32) -> Self {
        Self {
            value: value as i64,
            size: 4,
            sign_extend: false,
        }
    }

    /// Create an imm64.
    pub fn imm64(value: i64) -> Self {
        Self {
            value,
            size: 8,
            sign_extend: false,
        }
    }

    /// Create a sign-extended imm32 (encoded as 4 bytes, sign-extended to i64).
    pub fn imm32s(value: i64) -> Self {
        Self {
            value,
            size: 4,
            sign_extend: true,
        }
    }

    /// Encode as bytes (little-endian, truncated to size).
    pub fn encode(&self) -> Vec<u8> {
        match self.size {
            1 => vec![self.value as u8],
            2 => {
                let v = self.value as u16;
                vec![v as u8, (v >> 8) as u8]
            }
            4 => {
                let v = self.value as u32;
                vec![v as u8, (v >> 8) as u8, (v >> 16) as u8, (v >> 24) as u8]
            }
            8 => {
                let v = self.value as u64;
                vec![
                    v as u8,
                    (v >> 8) as u8,
                    (v >> 16) as u8,
                    (v >> 24) as u8,
                    (v >> 32) as u8,
                    (v >> 40) as u8,
                    (v >> 48) as u8,
                    (v >> 56) as u8,
                ]
            }
            _ => vec![self.value as u8],
        }
    }

    /// Check if the value fits in imm8 (sign-extended from 8 bits).
    pub fn fits_in_imm8(&self) -> bool {
        self.value >= -128 && self.value <= 127
    }

    /// Check if the value fits in imm32 (sign-extended from 32 bits).
    pub fn fits_in_imm32(&self) -> bool {
        self.value >= -(1i64 << 31) && self.value <= (1i64 << 31) - 1
    }

    /// Promote this immediate to the smallest size that fits.
    pub fn promote_to_fit(&self) -> Self {
        if self.fits_in_imm8() {
            Self {
                value: self.value,
                size: 1,
                sign_extend: true,
            }
        } else if self.fits_in_imm32() && self.size > 4 {
            Self {
                value: self.value,
                size: 4,
                sign_extend: true,
            }
        } else {
            self.clone()
        }
    }
}

// ============================================================================
// Complete Instruction Byte Encoding Helpers
// ============================================================================

/// Helper to encode an opcode with optional 0x0F prefix.
#[derive(Debug, Clone)]
pub struct OpcodeEncoder {
    /// Opcode map: 0=1-byte, 1=0F prefix, 2=0F38, 3=0F3A.
    pub opcode_map: u8,
    /// Base opcode byte.
    pub base_opcode: u8,
    /// Mandatory prefix: 0=none, 1=66, 2=F3, 3=F2.
    pub mandatory_prefix: u8,
}

impl OpcodeEncoder {
    pub fn new(base_opcode: u8) -> Self {
        Self {
            opcode_map: 0,
            base_opcode,
            mandatory_prefix: 0,
        }
    }

    pub fn with_map(mut self, map: u8) -> Self {
        self.opcode_map = map;
        self
    }

    pub fn with_prefix(mut self, prefix: u8) -> Self {
        self.mandatory_prefix = prefix;
        self
    }

    /// Encode the opcode bytes (prefix + opcode map + base opcode).
    pub fn encode(&self) -> Vec<u8> {
        let mut bytes = Vec::new();

        // Mandatory prefix
        match self.mandatory_prefix {
            1 => bytes.push(0x66),
            2 => bytes.push(0xF3),
            3 => bytes.push(0xF2),
            _ => {}
        }

        // Opcode map prefix
        match self.opcode_map {
            1 => bytes.push(0x0F),
            2 => {
                bytes.push(0x0F);
                bytes.push(0x38);
            }
            3 => {
                bytes.push(0x0F);
                bytes.push(0x3A);
            }
            _ => {}
        }

        bytes.push(self.base_opcode);
        bytes
    }

    /// Get the total number of prefix bytes before the ModR/M.
    pub fn prefix_len(&self) -> u8 {
        let mut len: u8 = 0;
        if self.mandatory_prefix != 0 {
            len += 1;
        }
        match self.opcode_map {
            0 => {}
            1 => len += 1,
            2 | 3 => len += 2,
            _ => {}
        }
        len + 1 // +1 for the base opcode itself
    }
}

/// Full instruction encoding: prefix + opcode + ModR/M + SIB + displacement + immediate.
#[derive(Debug, Clone)]
pub struct FullInstructionEncoder {
    /// REX/REX2 prefix bytes.
    pub rex_bytes: Vec<u8>,
    /// VEX/EVEX/XOP prefix bytes (mutually exclusive with REX).
    pub vex_bytes: Vec<u8>,
    /// Opcode bytes (including mandatory prefix and opcode map).
    pub opcode_bytes: Vec<u8>,
    /// ModR/M byte (optional).
    pub modrm: Option<u8>,
    /// SIB byte (optional).
    pub sib: Option<u8>,
    /// Displacement bytes.
    pub displacement: Vec<u8>,
    /// Immediate bytes.
    pub immediate: Vec<u8>,
}

impl FullInstructionEncoder {
    pub fn new() -> Self {
        Self {
            rex_bytes: Vec::new(),
            vex_bytes: Vec::new(),
            opcode_bytes: Vec::new(),
            modrm: None,
            sib: None,
            displacement: Vec::new(),
            immediate: Vec::new(),
        }
    }

    /// Assemble all bytes into the final instruction.
    pub fn assemble(&self) -> Vec<u8> {
        let mut result = Vec::new();

        // lock prefix and other legacy prefixes would go here

        // VEX/EVEX/XOP or REX
        if !self.vex_bytes.is_empty() {
            result.extend(&self.vex_bytes);
        } else {
            result.extend(&self.rex_bytes);
        }

        // Opcode bytes
        result.extend(&self.opcode_bytes);

        // ModR/M
        if let Some(m) = self.modrm {
            result.push(m);
        }

        // SIB
        if let Some(s) = self.sib {
            result.push(s);
        }

        // Displacement
        result.extend(&self.displacement);

        // Immediate
        result.extend(&self.immediate);

        result
    }

    /// Get the total instruction length in bytes.
    pub fn len(&self) -> usize {
        self.rex_bytes.len()
            + self.vex_bytes.len()
            + self.opcode_bytes.len()
            + self.modrm.map_or(0, |_| 1)
            + self.sib.map_or(0, |_| 1)
            + self.displacement.len()
            + self.immediate.len()
    }

    /// Whether this is a valid x86 instruction (fits in 15 bytes).
    pub fn is_valid_length(&self) -> bool {
        self.len() <= 15
    }

    /// Check if this instruction uses VEX/EVEX encoding.
    pub fn is_vex_encoded(&self) -> bool {
        !self.vex_bytes.is_empty()
    }

    /// Check if this instruction uses REX/REX2 encoding.
    pub fn is_rex_encoded(&self) -> bool {
        !self.rex_bytes.is_empty()
    }

    /// Check if this instruction uses legacy encoding (no prefixes beyond opcode).
    pub fn is_legacy_encoded(&self) -> bool {
        self.rex_bytes.is_empty() && self.vex_bytes.is_empty()
    }
}

impl Default for FullInstructionEncoder {
    fn default() -> Self {
        Self::new()
    }
}

/// Convenience builder for encoding a complete x86 instruction.
#[derive(Debug, Clone)]
pub struct InstructionBuilder {
    pub encoder: FullInstructionEncoder,
}

impl InstructionBuilder {
    pub fn new() -> Self {
        Self {
            encoder: FullInstructionEncoder::new(),
        }
    }

    /// Set the opcode.
    pub fn opcode(mut self, op: OpcodeEncoder) -> Self {
        self.encoder.opcode_bytes = op.encode();
        self
    }

    /// Add REX/REX2 prefix.
    pub fn rex(mut self, bytes: &[u8]) -> Self {
        self.encoder.rex_bytes = bytes.to_vec();
        self
    }

    /// Add ModR/M byte.
    pub fn modrm(mut self, enc: &ModRMEncoder) -> Self {
        self.encoder.modrm = Some(enc.encode());
        self
    }

    /// Add SIB byte.
    pub fn sib(mut self, enc: &SIBEncoder) -> Self {
        self.encoder.sib = Some(enc.encode());
        self
    }

    /// Add displacement.
    pub fn displacement(mut self, enc: &DisplacementEncoder) -> Self {
        self.encoder.displacement = enc.encode();
        self
    }

    /// Add immediate.
    pub fn immediate(mut self, enc: &ImmediateEncoder) -> Self {
        self.encoder.immediate = enc.encode();
        self
    }

    /// Build the final encoded bytes.
    pub fn build(&self) -> Vec<u8> {
        self.encoder.assemble()
    }

    /// Get the instruction length.
    pub fn len(&self) -> usize {
        self.encoder.len()
    }
}

impl Default for InstructionBuilder {
    fn default() -> Self {
        Self::new()
    }
}

/// Encode a simple register-to-register ALU operation.
pub fn encode_alu_rr(opcode: &OpcodeEncoder, dst: u8, src: u8, is_64bit: bool) -> Vec<u8> {
    let modrm = ModRMEncoder::reg_direct(dst, src);
    let rex = apx_rex2_encoder::encode_prefix(is_64bit, dst, src);

    let mut bytes = Vec::new();
    bytes.extend(&rex);
    bytes.extend(opcode.encode());
    bytes.push(modrm.encode());
    bytes
}

/// Encode a simple register-to-memory ALU operation.
pub fn encode_alu_rm(
    opcode: &OpcodeEncoder,
    reg: u8,
    base: u8,
    index: u8,
    scale: u8,
    disp: &DisplacementEncoder,
    is_64bit: bool,
) -> Vec<u8> {
    let sib = SIBEncoder::with_index(base, index, scale);
    let modrm = if disp.effective_disp() == 0 {
        ModRMEncoder::mem_no_disp(reg, base)
    } else if disp.fits_in_disp8() {
        ModRMEncoder::mem_disp8(reg, base)
    } else {
        ModRMEncoder::mem_disp32(reg, base)
    };

    let rex = apx_rex2_encoder::encode_prefix_mem(is_64bit, reg, base, index);

    let mut bytes = Vec::new();
    bytes.extend(&rex);
    bytes.extend(opcode.encode());
    bytes.push(modrm.encode());
    bytes.push(sib.encode());
    bytes.extend(disp.encode());
    bytes
}

/// Encode a register-to-immediate ALU operation (e.g., ADD r, imm).
pub fn encode_alu_ri(
    group_opcode: u8, // e.g., 0x81 for group 1
    reg_field: u8,    // e.g., 0 for ADD, 5 for SUB
    dst: u8,
    imm: &ImmediateEncoder,
    is_64bit: bool,
) -> Vec<u8> {
    let modrm = ModRMEncoder::reg_direct(reg_field, dst);
    let rex = apx_rex2_encoder::encode_prefix(is_64bit, reg_field, dst);

    let mut bytes = Vec::new();
    bytes.extend(&rex);
    bytes.push(group_opcode);
    bytes.push(modrm.encode());
    bytes.extend(imm.encode());
    bytes
}

// ============================================================================
// EVEX Compressed Displacement Table (disp8*N)
// ============================================================================

/// Complete EVEX compressed displacement multiplier lookup.
/// Maps (tuple_type, element_size_bits) → N multiplier.
/// Used to encode disp8*N compressed displacements.
pub mod evex_compressed_displacement {
    use super::EvexTuple;

    /// Get the N multiplier for EVEX compressed displacement.
    /// The actual memory displacement is encoded as disp8 = real_disp / N.
    ///
    /// N values per Intel SDM Volume 2, Section 2.7.5:
    /// - Full: 64 bytes (512-bit vector)
    /// - Half: 32 bytes (256-bit memory access)
    /// - Quarter: 16 bytes (128-bit memory access)
    /// - Eighth: 8 bytes (64-bit memory access)
    /// - Scalar: 4 or 8 bytes
    /// - FullMem: 64 byte memory-only
    /// - HalfMem: 32 byte memory-only
    /// - QuarterMem: 16 byte memory-only
    /// - EighthMem: 8 byte memory-only
    /// - Mem128: 16 byte memory-only (like QuarterMem)
    pub fn multiplier_for(tuple: EvexTuple, element_size_bits: u8) -> u8 {
        let full_n = match element_size_bits {
            8 => 64,  // VB = 64 bytes
            16 => 64, // VW = 64 bytes
            32 => 64, // VD = 64 bytes
            64 => 64, // VQ = 64 bytes
            _ => 64,
        };
        match tuple {
            EvexTuple::Full => full_n,
            EvexTuple::FullMem => 64,
            EvexTuple::Half | EvexTuple::HalfMem => 32,
            EvexTuple::Quarter | EvexTuple::QuarterMem | EvexTuple::Mem128 => 16,
            EvexTuple::Eighth | EvexTuple::EighthMem => 8,
            EvexTuple::Scalar => match element_size_bits {
                64 => 8,
                _ => 4,
            },
        }
    }

    /// Full compressed displacement table: maps disp8 value to actual displacement.
    /// For each tuple type and element size, the effective displacement.
    pub const DISP8_TABLE_FULL: [(u8, i32); 256] = {
        let mut table = [(0u8, 0i32); 256];
        let mut i = 0u16;
        while i < 256 {
            let disp8 = i as i8;
            table[i as usize] = (i as u8, disp8 as i32 * 64);
            i += 1;
        }
        table
    };

    pub const DISP8_TABLE_HALF: [(u8, i32); 256] = {
        let mut table = [(0u8, 0i32); 256];
        let mut i = 0u16;
        while i < 256 {
            let disp8 = i as i8;
            table[i as usize] = (i as u8, disp8 as i32 * 32);
            i += 1;
        }
        table
    };

    pub const DISP8_TABLE_QUARTER: [(u8, i32); 256] = {
        let mut table = [(0u8, 0i32); 256];
        let mut i = 0u16;
        while i < 256 {
            let disp8 = i as i8;
            table[i as usize] = (i as u8, disp8 as i32 * 16);
            i += 1;
        }
        table
    };

    pub const DISP8_TABLE_EIGHTH: [(u8, i32); 256] = {
        let mut table = [(0u8, 0i32); 256];
        let mut i = 0u16;
        while i < 256 {
            let disp8 = i as i8;
            table[i as usize] = (i as u8, disp8 as i32 * 8);
            i += 1;
        }
        table
    };

    pub const DISP8_TABLE_SCALAR_4: [(u8, i32); 256] = {
        let mut table = [(0u8, 0i32); 256];
        let mut i = 0u16;
        while i < 256 {
            let disp8 = i as i8;
            table[i as usize] = (i as u8, disp8 as i32 * 4);
            i += 1;
        }
        table
    };

    pub const DISP8_TABLE_SCALAR_8: [(u8, i32); 256] = {
        let mut table = [(0u8, 0i32); 256];
        let mut i = 0u16;
        while i < 256 {
            let disp8 = i as i8;
            table[i as usize] = (i as u8, disp8 as i32 * 8);
            i += 1;
        }
        table
    };

    /// Encode a real displacement into EVEX compressed disp8.
    /// Returns None if displacement cannot be compressed.
    pub fn compress_disp(real_disp: i32, n: u8) -> Option<u8> {
        if real_disp % n as i32 != 0 {
            return None;
        }
        let compressed = real_disp / n as i32;
        if compressed < -128 || compressed > 127 {
            return None;
        }
        Some(compressed as u8)
    }

    /// Decompress a disp8 back to the real displacement.
    pub fn decompress_disp(disp8: u8, n: u8) -> i32 {
        (disp8 as i8 as i32) * n as i32
    }

    /// Get the lookup table for a given tuple and element size.
    pub fn get_disp_table(tuple: EvexTuple, element_size_bits: u8) -> &'static [(u8, i32); 256] {
        match tuple {
            EvexTuple::Full | EvexTuple::FullMem => &DISP8_TABLE_FULL,
            EvexTuple::Half | EvexTuple::HalfMem => &DISP8_TABLE_HALF,
            EvexTuple::Quarter | EvexTuple::QuarterMem | EvexTuple::Mem128 => &DISP8_TABLE_QUARTER,
            EvexTuple::Eighth | EvexTuple::EighthMem => &DISP8_TABLE_EIGHTH,
            EvexTuple::Scalar => {
                if element_size_bits == 64 {
                    &DISP8_TABLE_SCALAR_8
                } else {
                    &DISP8_TABLE_SCALAR_4
                }
            }
        }
    }
}

// ============================================================================
// EVEX Broadcast Encoding
// ============================================================================

/// EVEX broadcast mode encoding with proper N values.
/// Controls how a single memory element is broadcast to all vector lanes.
pub mod evex_broadcast_encoding {
    use super::EvexBroadcast;

    /// Get the N value (element count in source) for a broadcast mode.
    /// Based on vector length and element size:
    /// - {1to2}: VL/2 elements, N=8 for 128-bit, N=16 for 256-bit, N=32 for 512-bit
    /// - {1to4}: VL/4 elements, N=4 for 128-bit, N=8 for 256-bit, N=16 for 512-bit
    /// - {1to8}: VL/8 elements, N=2 for 128-bit, N=4 for 256-bit, N=8 for 512-bit
    /// - {1to16}: VL/16 elements, N=1 for 128-bit, N=2 for 256-bit, N=4 for 512-bit
    /// - {1to32}: VL/32 elements, N=1 for 256-bit, N=2 for 512-bit
    pub fn element_count(broadcast: EvexBroadcast, vector_len_bits: u16) -> u8 {
        let vl_bytes = vector_len_bits / 8;
        match broadcast {
            EvexBroadcast::None => vl_bytes as u8,
            EvexBroadcast::Broadcast1To2 => 2,
            EvexBroadcast::Broadcast1To4 => 4,
            EvexBroadcast::Broadcast1To8 => 8,
            EvexBroadcast::Broadcast1To16 => 16,
            EvexBroadcast::Broadcast1To32 => 32,
        }
    }

    /// Get the element size in bytes for a broadcast mode.
    /// For broadcast {1toN}, the source element size = vector_len / N.
    pub fn element_size_bytes(broadcast: EvexBroadcast, vector_len_bits: u16) -> u8 {
        let count = element_count(broadcast, vector_len_bits);
        if count == 0 {
            return 0;
        }
        (vector_len_bits / 8) as u8 / count
    }

    /// Whether a given broadcast mode and vector length is valid.
    pub fn is_valid_broadcast(broadcast: EvexBroadcast, vector_len_bits: u16) -> bool {
        match broadcast {
            EvexBroadcast::None => true,
            EvexBroadcast::Broadcast1To2 => vector_len_bits >= 128,
            EvexBroadcast::Broadcast1To4 => vector_len_bits >= 128,
            EvexBroadcast::Broadcast1To8 => vector_len_bits >= 256,
            EvexBroadcast::Broadcast1To16 => vector_len_bits >= 256,
            EvexBroadcast::Broadcast1To32 => vector_len_bits == 512,
        }
    }

    /// Get the compressed displacement N multiplier for a broadcast mode.
    /// For broadcast, the memory operand is a single element, so N = element_size.
    pub fn broadcast_disp_multiplier(broadcast: EvexBroadcast, vector_len_bits: u16) -> u8 {
        if broadcast == EvexBroadcast::None {
            return 64; // default full
        }
        element_size_bytes(broadcast, vector_len_bits)
    }

    /// Convert broadcast N value to the EVEX b' bit.
    /// b'=1 for broadcast, b'=0 for no broadcast.
    pub fn to_b_bit(broadcast: EvexBroadcast) -> bool {
        broadcast.is_broadcast()
    }

    /// String representation of broadcast.
    pub fn to_string(broadcast: EvexBroadcast) -> &'static str {
        match broadcast {
            EvexBroadcast::None => "",
            EvexBroadcast::Broadcast1To2 => "{1to2}",
            EvexBroadcast::Broadcast1To4 => "{1to4}",
            EvexBroadcast::Broadcast1To8 => "{1to8}",
            EvexBroadcast::Broadcast1To16 => "{1to16}",
            EvexBroadcast::Broadcast1To32 => "{1to32}",
        }
    }
}

// ============================================================================
// EVEX Rounding Mode Encoding
// ============================================================================

/// EVEX rounding mode encoding for FP instructions.
/// The rounding mode is encoded in the EVEX LL field (bits 5-4 of P2 byte)
/// when b'=1 (suppress-all-exceptions SAE or rounding override).
pub mod evex_rounding_encoding {
    use super::EvexRounding;

    /// Convert rounding mode to EVEX RC bits (encoded in LL field).
    ///
    /// Encoding per Intel SDM:
    ///   {rn-sae} → RC=0 (round to nearest)
    ///   {rd-sae} → RC=1 (round toward -inf)
    ///   {ru-sae} → RC=2 (round toward +inf)
    ///   {rz-sae} → RC=3 (round toward zero)
    ///   {sae}    → SAE=1 with RC=0 (no rounding change, suppress all exceptions)
    pub fn to_rc_bits(rounding: EvexRounding) -> u8 {
        match rounding {
            EvexRounding::None => 0,
            EvexRounding::RnSae => 0,
            EvexRounding::RdSae => 1,
            EvexRounding::RuSae => 2,
            EvexRounding::RzSae => 3,
            EvexRounding::Sae => 0,
        }
    }

    /// Get the SAE (Suppress All Exceptions) flag.
    /// SAE=1 when any {sae} rounding mode is specified.
    pub fn has_sae(rounding: EvexRounding) -> bool {
        matches!(
            rounding,
            EvexRounding::RnSae
                | EvexRounding::RdSae
                | EvexRounding::RuSae
                | EvexRounding::RzSae
                | EvexRounding::Sae
        )
    }

    /// Check if rounding mode has an explicit rounding direction change
    /// (not just SAE).
    pub fn has_explicit_rc(rounding: EvexRounding) -> bool {
        matches!(
            rounding,
            EvexRounding::RnSae | EvexRounding::RdSae | EvexRounding::RuSae | EvexRounding::RzSae
        )
    }

    /// Encode rounding mode into LL field (2 bits).
    /// When combined with L' bit for vector length, the full L'L encoding:
    ///   00 = 128-bit (or rounding mode RN-SAE)
    ///   01 = 256-bit (or rounding mode RD-SAE)
    ///   10 = 512-bit (or rounding mode RU-SAE)
    ///   11 = reserved (or rounding mode RZ-SAE)
    pub fn encode_ll_for_rounding(rounding: EvexRounding) -> u8 {
        to_rc_bits(rounding) & 0x3
    }

    /// String representation of rounding mode.
    pub fn to_string(rounding: EvexRounding) -> &'static str {
        match rounding {
            EvexRounding::None => "",
            EvexRounding::RnSae => "{rn-sae}",
            EvexRounding::RdSae => "{rd-sae}",
            EvexRounding::RuSae => "{ru-sae}",
            EvexRounding::RzSae => "{rz-sae}",
            EvexRounding::Sae => "{sae}",
        }
    }

    /// Map from string suffix to rounding mode.
    pub fn from_suffix(s: &str) -> Option<EvexRounding> {
        match s {
            "rn-sae" => Some(EvexRounding::RnSae),
            "rd-sae" => Some(EvexRounding::RdSae),
            "ru-sae" => Some(EvexRounding::RuSae),
            "rz-sae" => Some(EvexRounding::RzSae),
            "sae" => Some(EvexRounding::Sae),
            _ => None,
        }
    }
}

// ============================================================================
// EVEX Opmask Register Encoding
// ============================================================================

/// EVEX opmask register encoding.
/// The aaa field (bits 2-0 of P2 byte) selects the mask register.
pub mod evex_opmask_encoding {
    /// Map opmask register number to EVEX aaa field.
    /// k0 (no mask) → aaa=0
    /// k1 → aaa=1
    /// ...
    /// k7 → aaa=7
    pub fn to_aaa(mask_reg: u8) -> u8 {
        mask_reg & 0x7
    }

    /// Map EVEX aaa field back to opmask register.
    /// aaa=0 → k0 (which means "no masking")
    /// aaa=1 → k1, ..., aaa=7 → k7
    pub fn from_aaa(aaa: u8) -> u8 {
        aaa & 0x7
    }

    /// Opmask register name strings.
    pub fn reg_name(reg: u8) -> &'static str {
        match reg & 0x7 {
            0 => "k0",
            1 => "k1",
            2 => "k2",
            3 => "k3",
            4 => "k4",
            5 => "k5",
            6 => "k6",
            7 => "k7",
            _ => "k0",
        }
    }

    /// Whether a given opmask register value implies active masking.
    /// k0 is the "no mask" register.
    pub fn has_active_mask(mask_reg: u8) -> bool {
        (mask_reg & 0x7) != 0
    }

    /// Check if an opmask register is valid for AVX-512.
    pub fn is_valid_opmask(reg: u8) -> bool {
        (reg & 0xF8) == 0
    }
}

// ============================================================================
// EVEX Zeroing Merge (z bit)
// ============================================================================

/// EVEX zeroing merge encoding.
/// The z bit (bit 7 of P2 byte) controls how masked elements are handled:
///   z=1: {z} merge on zero — masked elements become 0
///   z=0: merge — masked elements retain destination value
pub mod evex_zeroing_encoding {
    /// Check if {z} zeroing is specified.
    pub fn has_zeroing(z: bool) -> bool {
        z
    }

    /// Zeroing only applies when there is an active mask.
    /// If no mask (k0), zeroing is silently ignored.
    pub fn effective_zeroing(z: bool, has_mask: bool) -> bool {
        z && has_mask
    }

    /// String representation of zeroing.
    pub fn to_string(z: bool) -> &'static str {
        if z {
            "{z}"
        } else {
            ""
        }
    }
}

// ============================================================================
// EVEX Vector Length Encoding (L'L)
// ============================================================================

/// EVEX vector length encoding.
/// The L'L field (bits 6-5 of P2 byte) encodes the vector length:
///   00 = 128-bit (L'=0, L=0)
///   01 = 256-bit (L'=0, L=1)
///   10 = 512-bit (L'=1, L=0)
///   11 = reserved
///
/// When rounding mode is active (b'=1), L'L encodes rounding control instead.
pub mod evex_vector_length {
    /// Encode vector length in bits to L'L field.
    pub fn encode(vl_bits: u16) -> u8 {
        match vl_bits {
            128 => 0b00,
            256 => 0b01,
            512 => 0b10,
            _ => 0b00, // default to 128-bit
        }
    }

    /// Decode L'L field to vector length in bits.
    pub fn decode(ll: u8) -> u16 {
        match ll & 0x3 {
            0b00 => 128,
            0b01 => 256,
            0b10 => 512,
            _ => 128,
        }
    }

    /// Get the L' (bit 1 of LL) and L (bit 0 of LL) bits separately.
    pub fn to_l_prime(ll: u8) -> bool {
        (ll >> 1) & 1 != 0
    }

    pub fn to_l(ll: u8) -> bool {
        ll & 1 != 0
    }

    /// Used for VEX 2-byte/3-byte: L=0 for 128-bit, L=1 for 256-bit.
    pub fn vex_l_bit(vl_bits: u16) -> bool {
        vl_bits >= 256
    }

    /// Whether the given vector length is a valid EVEX encoding.
    pub fn is_valid_evex_vl(vl_bits: u16) -> bool {
        matches!(vl_bits, 128 | 256 | 512)
    }

    /// Get vector length string.
    pub fn to_string(vl_bits: u16) -> &'static str {
        match vl_bits {
            128 => "xmm",
            256 => "ymm",
            512 => "zmm",
            _ => "unknown",
        }
    }
}

// ============================================================================
// Complete VEX 3-Byte Encoding with All Field Combinations
// ============================================================================

/// Full VEX 3-byte prefix encoder with all field combinations.
pub mod vex_full_encoder {
    /// Build a 3-byte VEX prefix with explicit control over every field.
    ///
    /// VEX 3-byte format:
    ///   Byte 0: 0xC4 (fixed)
    ///   Byte 1: [~R(1) | ~X(1) | ~B(1) | mmmmm(5)]
    ///   Byte 2: [W(1) | ~vvvv(4) | L(1) | pp(2)]
    ///
    /// Where:
    ///   ~R, ~X, ~B: 1's complement of REX.R, REX.X, REX.B
    ///   mmmmm: opcode map selector (1=0F, 2=0F38, 3=0F3A)
    ///   W: operand size (0=default, 1=64-bit)
    ///   ~vvvv: 1's complement of additional source register
    ///   L: vector length (0=128-bit, 1=256-bit)
    ///   pp: implied mandatory prefix (0=none, 1=66, 2=F3, 3=F2)
    pub fn build_full(
        r: bool,
        x: bool,
        b: bool,
        mmmmm: u8,
        w: bool,
        vvvv: u8,
        l: bool,
        pp: u8,
    ) -> [u8; 3] {
        let byte1 = ((!r as u8) << 7) | ((!x as u8) << 6) | ((!b as u8) << 5) | (mmmmm & 0x1F);
        let byte2 = ((w as u8) << 7) | ((!vvvv & 0xF) << 3) | ((l as u8) << 2) | (pp & 0x3);
        [0xC4, byte1, byte2]
    }

    /// VEX opcode map constants.
    pub mod vex_map {
        pub const MAP_NONE: u8 = 0;
        pub const MAP_0F: u8 = 1;
        pub const MAP_0F38: u8 = 2;
        pub const MAP_0F3A: u8 = 3;
    }

    /// VEX mandatory prefix constants (pp field).
    pub mod vex_pp {
        pub const PP_NONE: u8 = 0;
        pub const PP_66: u8 = 1;
        pub const PP_F3: u8 = 2;
        pub const PP_F2: u8 = 3;
    }

    /// Decode a 3-byte VEX prefix from raw bytes.
    /// Returns the individual fields.
    pub fn decode_vex3(bytes: &[u8]) -> Option<(bool, bool, bool, u8, bool, u8, bool, u8)> {
        if bytes.len() < 3 || bytes[0] != 0xC4 {
            return None;
        }
        let byte1 = bytes[1];
        let byte2 = bytes[2];
        let r = (byte1 >> 7) & 1 == 0;
        let x = (byte1 >> 6) & 1 == 0;
        let b = (byte1 >> 5) & 1 == 0;
        let mmmmm = byte1 & 0x1F;
        let w = (byte2 >> 7) & 1 != 0;
        let vvvv = !((byte2 >> 3) & 0xF) & 0xF;
        let l = (byte2 >> 2) & 1 != 0;
        let pp = byte2 & 0x3;
        Some((r, x, b, mmmmm, w, vvvv, l, pp))
    }

    /// The complete VEX field set as a struct.
    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
    pub struct VexFields {
        pub r: bool,
        pub x: bool,
        pub b: bool,
        pub mmmmm: u8,
        pub w: bool,
        pub vvvv: u8,
        pub l: bool,
        pub pp: u8,
    }

    impl VexFields {
        pub fn encode_3byte(&self) -> [u8; 3] {
            build_full(
                self.r, self.x, self.b, self.mmmmm, self.w, self.vvvv, self.l, self.pp,
            )
        }

        /// Get the effective register number from ~R, ~X, ~B, ~vvvv fields.
        pub fn effective_reg_r(&self, reg: u8) -> u8 {
            if self.r {
                reg | 0x8
            } else {
                reg & 0x7
            }
        }

        pub fn effective_reg_x(&self, idx: u8) -> u8 {
            if self.x {
                idx | 0x8
            } else {
                idx & 0x7
            }
        }

        pub fn effective_reg_b(&self, base: u8) -> u8 {
            if self.b {
                base | 0x8
            } else {
                base & 0x7
            }
        }
    }
}

// ============================================================================
// Complete XOP Encoding for AMD-Specific Instructions
// ============================================================================

/// Extended XOP encoder with full instruction map.
/// AMD XOP instructions use opcode map 8, 9, or 10 with various opcodes.
pub mod xop_full_encoder {
    /// XOP opcode table: maps XOP opcode to mnemonic.
    pub mod xop_opcodes {
        // XOP map 8: horizontal integer operations
        pub const VPHADDBD: u8 = 0xC2;
        pub const VPHADDBQ: u8 = 0xC3;
        pub const VPHADDWD: u8 = 0xC6;
        pub const VPHADDWQ: u8 = 0xC7;
        pub const VPHADDDQ: u8 = 0xCB;
        pub const VPHADDUBD: u8 = 0xD2;
        pub const VPHADDUBQ: u8 = 0xD3;
        pub const VPHADDUWD: u8 = 0xD6;
        pub const VPHADDUWQ: u8 = 0xD7;
        pub const VPHADDUDQ: u8 = 0xDB;
        pub const VPHSUBBW: u8 = 0xE2;
        pub const VPHSUBDQ: u8 = 0xE3;
        pub const VPHSUBWD: u8 = 0xE6;
        pub const VPROTB: u8 = 0x90;
        pub const VPROTW: u8 = 0x91;
        pub const VPROTD: u8 = 0x92;
        pub const VPROTQ: u8 = 0x93;
        pub const VPMACSSWW: u8 = 0x95;
        pub const VPMACSSWD: u8 = 0x96;
        pub const VPMACSSDQL: u8 = 0x9E;
        pub const VPMACSSDQH: u8 = 0x9F;
        pub const VPMACSSDD: u8 = 0x9C;
        pub const VPMACSWW: u8 = 0xA5;
        pub const VPMACSWD: u8 = 0xA6;
        pub const VPMACSDQL: u8 = 0xAE;
        pub const VPMACSDQH: u8 = 0xAF;
        pub const VPMACSDD: u8 = 0xAC;
        pub const VPMADCSSWD: u8 = 0xB6;
        pub const VPMADCSWD: u8 = 0xC6;

        // XOP map 9: horizontal shift/rotate
        pub const VPSHAB: u8 = 0x98;
        pub const VPSHAW: u8 = 0x99;
        pub const VPSHAD: u8 = 0x9A;
        pub const VPSHAQ: u8 = 0x9B;
        pub const VPSHLB: u8 = 0x94;
        pub const VPSHLW: u8 = 0x95;
        pub const VPSHLD: u8 = 0x96;
        pub const VPSHLQ: u8 = 0x97;

        // XOP map 10: floating-point
        pub const VFRCZPS: u8 = 0x80;
        pub const VFRCZPD: u8 = 0x81;
        pub const VFRCZSS: u8 = 0x82;
        pub const VFRCZSD: u8 = 0x83;
        pub const VPCMOV: u8 = 0xA2;
        pub const VPPERM: u8 = 0xA3;
        pub const VPCOMB: u8 = 0xCC;
        pub const VPCOMW: u8 = 0xCD;
        pub const VPCOMD: u8 = 0xCE;
        pub const VPCOMQ: u8 = 0xCF;
        pub const VPCOMUB: u8 = 0xEC;
        pub const VPCOMUW: u8 = 0xED;
        pub const VPCOMUD: u8 = 0xEE;
        pub const VPCOMUQ: u8 = 0xEF;
    }

    /// Map XOP opcode to string mnemonic.
    pub fn xop_mnemonic(opcode: u8, map: u8) -> Option<&'static str> {
        match (map, opcode) {
            (8, 0x90) => Some("vprotb"),
            (8, 0x91) => Some("vprotw"),
            (8, 0x92) => Some("vprotd"),
            (8, 0x93) => Some("vprotq"),
            (8, 0x95) => Some("vpmacssww"),
            (8, 0x96) => Some("vpmacsswd"),
            (8, 0x9C) => Some("vpmacssdd"),
            (8, 0x9E) => Some("vpmacssdql"),
            (8, 0x9F) => Some("vpmacssdqh"),
            (8, 0xA5) => Some("vpmacsww"),
            (8, 0xA6) => Some("vpmacswd"),
            (8, 0xAC) => Some("vpmacsdd"),
            (8, 0xAE) => Some("vpmacsdql"),
            (8, 0xAF) => Some("vpmacsdqh"),
            (8, 0xB6) => Some("vpmadcsswd"),
            (8, 0xC2) => Some("vphaddbd"),
            (8, 0xC3) => Some("vphaddbq"),
            (8, 0xC6) => Some("vphaddwd"),
            (8, 0xC7) => Some("vphaddwq"),
            (8, 0xCB) => Some("vphadddq"),
            (8, 0xD2) => Some("vphaddubd"),
            (8, 0xD3) => Some("vphaddubq"),
            (8, 0xD6) => Some("vphadduwd"),
            (8, 0xD7) => Some("vphadduwq"),
            (8, 0xDB) => Some("vphaddudq"),
            (8, 0xE2) => Some("vphsubbw"),
            (8, 0xE3) => Some("vphsubdq"),
            (8, 0xE6) => Some("vphsubwd"),
            (9, 0x94) => Some("vpshlb"),
            (9, 0x95) => Some("vpshlw"),
            (9, 0x96) => Some("vpshld"),
            (9, 0x97) => Some("vpshlq"),
            (9, 0x98) => Some("vpshab"),
            (9, 0x99) => Some("vpshaw"),
            (9, 0x9A) => Some("vpshad"),
            (9, 0x9B) => Some("vpshaq"),
            (10, 0x80) => Some("vfrcsps"),
            (10, 0x81) => Some("vfrcspd"),
            (10, 0x82) => Some("vfrcsss"),
            (10, 0x83) => Some("vfrcssd"),
            (10, 0xA2) => Some("vpcmov"),
            (10, 0xA3) => Some("vpperm"),
            (10, 0xCC) => Some("vpcomb"),
            (10, 0xCD) => Some("vpcomw"),
            (10, 0xCE) => Some("vpcomd"),
            (10, 0xCF) => Some("vpcomq"),
            (10, 0xEC) => Some("vpcomub"),
            (10, 0xED) => Some("vpcomuw"),
            (10, 0xEE) => Some("vpcomud"),
            (10, 0xEF) => Some("vpcomuq"),
            _ => None,
        }
    }
}

// ============================================================================
// 3DNow! Legacy Encoding
// ============================================================================

/// AMD 3DNow! instruction encoding.
/// 3DNow! uses: 0F 0F prefix + ModR/M + immediate opcode suffix byte.
pub mod tdnow_encoder {
    /// 3DNow! opcode suffix bytes (the byte after ModR/M).
    pub mod tdnow_opcodes {
        pub const PI2FD: u8 = 0x0D;
        pub const PI2FW: u8 = 0x0C;
        pub const PF2ID: u8 = 0x1D;
        pub const PF2IW: u8 = 0x1C;
        pub const PFACC: u8 = 0xAE;
        pub const PFADD: u8 = 0x9E;
        pub const PFCMPEQ: u8 = 0xB0;
        pub const PFCMPGE: u8 = 0x90;
        pub const PFCMPGT: u8 = 0xA0;
        pub const PFMAX: u8 = 0xA4;
        pub const PFMIN: u8 = 0x94;
        pub const PFMUL: u8 = 0xB4;
        pub const PFNACC: u8 = 0x8A;
        pub const PFPNACC: u8 = 0x8E;
        pub const PFRCP: u8 = 0x96;
        pub const PFRCPIT1: u8 = 0xA6;
        pub const PFRCPIT2: u8 = 0xB6;
        pub const PFRSQIT1: u8 = 0xA7;
        pub const PFRSQRT: u8 = 0x97;
        pub const PFSUB: u8 = 0x9A;
        pub const PFSUBR: u8 = 0xAA;
        pub const PMULHRW: u8 = 0xB7;
        pub const PAVGUSB: u8 = 0xBF;
        pub const FEMMS: u8 = 0x0E;
        pub const PREFETCH: u8 = 0x0D;
        pub const PREFETCHW: u8 = 0x0D; // same opcode, different ModR/M
    }

    /// Encode a 3DNow! instruction.
    /// Format: [0F 0F] [ModR/M] [immediate opcode]
    pub fn encode(mm_reg1: u8, mm_reg2: u8, tdnow_opcode: u8) -> [u8; 4] {
        let modrm = 0xC0 | ((mm_reg2 & 0x7) << 3) | (mm_reg1 & 0x7);
        [0x0F, 0x0F, modrm, tdnow_opcode]
    }

    /// Encode FEMMS (fast EMMS) — just 0F 0E.
    pub fn encode_femms() -> [u8; 2] {
        [0x0F, 0x0E]
    }

    /// Check if an 0F 0F sequence starts a 3DNow! instruction.
    pub fn is_tdnow_prefix(b0: u8, b1: u8) -> bool {
        b0 == 0x0F && b1 == 0x0F
    }

    /// Map 3DNow! opcode suffix to mnemonic.
    pub fn tdnow_mnemonic(opcode: u8) -> Option<&'static str> {
        match opcode {
            0x0C => Some("pi2fw"),
            0x0D => Some("pi2fd"),
            0x1C => Some("pf2iw"),
            0x1D => Some("pf2id"),
            0x8A => Some("pfnacc"),
            0x8E => Some("pfpnacc"),
            0x90 => Some("pfcmpge"),
            0x94 => Some("pfmin"),
            0x96 => Some("pfrcp"),
            0x97 => Some("pfrsqrt"),
            0x9A => Some("pfsub"),
            0x9E => Some("pfadd"),
            0xA0 => Some("pfcmpgt"),
            0xA4 => Some("pfmax"),
            0xA6 => Some("pfrcpit1"),
            0xA7 => Some("pfrsqit1"),
            0xAA => Some("pfsubr"),
            0xAE => Some("pfacc"),
            0xB0 => Some("pfcmpeq"),
            0xB4 => Some("pfmul"),
            0xB6 => Some("pfrcpit2"),
            0xB7 => Some("pmulhrw"),
            0xBF => Some("pavgusb"),
            0x0E => Some("femms"),
            _ => None,
        }
    }
}

// ============================================================================
// Complete Immediate Size Table Per Opcode
// ============================================================================

/// Immediate size lookup for x86 instructions.
/// Maps opcode to the size of its immediate operand.
pub mod immediate_size_table {
    /// Immediate size in bytes.
    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
    pub enum ImmSize {
        None,
        Imm8,
        Imm16,
        Imm32,
        Imm64,
        Imm8SignExt,
    }

    /// Default immediate sizes for common opcode groups.
    /// Returns the immediate size based on opcode byte.
    pub fn size_for_opcode(opcode: u8, has_rex_w: bool) -> ImmSize {
        match opcode {
            // Immediate ALU operations with imm8
            0x6A => ImmSize::Imm8, // PUSH imm8
            0x6B => ImmSize::Imm8, // IMUL r, r/m, imm8
            0x80 => ImmSize::Imm8, // Group 1 imm8
            0x82 => ImmSize::Imm8, // Group 1 imm8 (undocumented)
            0x83 => ImmSize::Imm8, // Group 1 imm8
            0xA8 => ImmSize::Imm8, // TEST AL, imm8
            0xC0 => ImmSize::Imm8, // Group 2 shift imm8
            0xC1 => ImmSize::Imm8, // Group 2 shift imm8 (32-bit)
            0xC6 => ImmSize::Imm8, // MOV r/m8, imm8

            // Immediate ALU operations with imm16/imm32/imm64
            0x68 => {
                if has_rex_w {
                    ImmSize::Imm64
                } else {
                    ImmSize::Imm32
                }
            }
            0x69 => ImmSize::Imm32, // IMUL r, r/m, imm32
            0x81 => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }
            0xB8..=0xBF => {
                if has_rex_w {
                    ImmSize::Imm64
                } else {
                    ImmSize::Imm32
                }
            }
            0xC7 => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }

            // AL/AX/EAX/RAX immediate forms
            0x04 => ImmSize::Imm8, // ADD AL, imm8
            0x05 => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }
            0x0C => ImmSize::Imm8, // OR AL, imm8
            0x0D => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }
            0x14 => ImmSize::Imm8, // ADC AL, imm8
            0x15 => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }
            0x1C => ImmSize::Imm8, // SBB AL, imm8
            0x1D => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }
            0x24 => ImmSize::Imm8, // AND AL, imm8
            0x25 => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }
            0x2C => ImmSize::Imm8, // SUB AL, imm8
            0x2D => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }
            0x34 => ImmSize::Imm8, // XOR AL, imm8
            0x35 => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }
            0x3C => ImmSize::Imm8, // CMP AL, imm8
            0x3D => {
                if has_rex_w {
                    ImmSize::Imm32
                } else {
                    ImmSize::Imm32
                }
            }

            // Jump/Call with immediate offset
            0xE8 | 0xE9 => ImmSize::Imm32, // CALL/JMP rel32
            0xEB => ImmSize::Imm8,         // JMP rel8
            0x70..=0x7F => ImmSize::Imm8,  // Jcc rel8
            0xE0..=0xE3 => ImmSize::Imm8,  // LOOPcc rel8

            // Enter with two immediates
            0xC8 => ImmSize::Imm16, // ENTER imm16, imm8

            // Return with immediate
            0xC2 | 0xCA => ImmSize::Imm16, // RET imm16

            // INT
            0xCC => ImmSize::None, // INT3 (no immediate)
            0xCD => ImmSize::Imm8, // INT imm8

            // IN/OUT
            0xE4 | 0xE6 => ImmSize::Imm8, // IN AL/AX/EAX, imm8
            0xE5 | 0xE7 => ImmSize::Imm8, // OUT imm8, AL/AX/EAX

            // AAM/AAD
            0xD4 => ImmSize::Imm8, // AAM imm8
            0xD5 => ImmSize::Imm8, // AAD imm8

            _ => ImmSize::None,
        }
    }

    /// Get the encoded size in bytes.
    pub fn size_in_bytes(size: ImmSize) -> u8 {
        match size {
            ImmSize::None => 0,
            ImmSize::Imm8 | ImmSize::Imm8SignExt => 1,
            ImmSize::Imm16 => 2,
            ImmSize::Imm32 => 4,
            ImmSize::Imm64 => 8,
        }
    }

    /// Check if the immediate is sign-extended.
    pub fn is_sign_extended(size: ImmSize) -> bool {
        matches!(size, ImmSize::Imm8SignExt)
    }
}

// ============================================================================
// Sign Extension Handling for 8-bit Immediates
// ============================================================================

/// Sign extension helpers for x86 immediates.
/// Many x86 instructions take an 8-bit immediate and sign-extend it
/// to the operand size (16, 32, or 64 bits).
pub mod sign_extension {
    /// Sign-extend an 8-bit value to 16 bits.
    pub fn ext8_to_16(value: i8) -> i16 {
        value as i16
    }

    /// Sign-extend an 8-bit value to 32 bits.
    pub fn ext8_to_32(value: i8) -> i32 {
        value as i32
    }

    /// Sign-extend an 8-bit value to 64 bits.
    pub fn ext8_to_64(value: i8) -> i64 {
        value as i64
    }

    /// Sign-extend a 16-bit value to 32 bits.
    pub fn ext16_to_32(value: i16) -> i32 {
        value as i32
    }

    /// Sign-extend a 16-bit value to 64 bits.
    pub fn ext16_to_64(value: i16) -> i64 {
        value as i64
    }

    /// Sign-extend a 32-bit value to 64 bits.
    pub fn ext32_to_64(value: i32) -> i64 {
        value as i64
    }

    /// Sign-extend an immediate based on the required destination size.
    pub fn sign_extend_imm(value: i64, dest_size_bits: u8) -> i64 {
        match dest_size_bits {
            8 => (value as i8) as i64,
            16 => (value as i16) as i64,
            32 => (value as i32) as i64,
            64 => value,
            _ => value,
        }
    }

    /// Check if a value fits in a sign-extended imm8 for the given operand size.
    /// For example, for 32-bit operation, an imm8 of -1 sign-extends to 0xFFFFFFFF.
    pub fn fits_in_sign_ext_imm8(value: i64, operand_size_bits: u8) -> bool {
        let truncated = sign_extend_imm(value, operand_size_bits);
        let back_to_8 = (truncated as i8) as i64;
        sign_extend_imm(back_to_8, operand_size_bits) == truncated
    }

    /// Check if an imm32 sign-extends correctly to imm64.
    pub fn fits_in_sign_ext_imm32(value: i64) -> bool {
        (value as i32) as i64 == value
    }
}

// ============================================================================
// Tests
// ============================================================================

#[cfg(test)]
mod tests {
    use super::super::x86_subtarget::X86Subtarget;
    use super::*;

    fn make_subtarget() -> X86Subtarget {
        X86Subtarget::new("x86_64-unknown-none", "generic", "")
    }

    fn make_encoder() -> X86FullMCEncoder {
        X86FullMCEncoder::new(X86Mode::Mode64, make_subtarget())
    }

    // === Legacy encoding tests ===

    #[test]
    fn test_encode_nop() {
        let mut enc = make_encoder();
        let bytes = enc.encode_nop();
        assert!(!bytes.is_empty(), "NOP should produce at least 1 byte");
    }

    #[test]
    fn test_encode_ret() {
        let mut enc = make_encoder();
        let bytes = enc.encode_ret();
        assert!(!bytes.is_empty(), "RET should produce at least 1 byte");
    }

    #[test]
    fn test_encode_call() {
        let mut enc = make_encoder();
        let bytes = enc.encode_call(0x12345678);
        assert_eq!(bytes[0], 0xE8);
        assert_eq!(&bytes[1..5], &0x12345678u32.to_le_bytes());
    }

    #[test]
    fn test_encode_mov_rax_rcx() {
        let mut enc = make_encoder();
        let bytes = enc.encode_mov_rr(RAX, RCX);
        // MOV r64, r/m64: REX.W + 8B /r
        // REX.W
        assert_eq!(bytes[1], 0x89); // MOV r/m64, r64
        assert_eq!(bytes[2], 0xC8); // ModR/M: mod=3, reg=RCX(1), rm=RAX(0)
    }

    #[test]
    fn test_encode_add_rax_imm5() {
        let mut enc = make_encoder();
        let bytes = enc.encode_add_ri(RAX, 5);
        assert!(bytes.len() >= 3, "ADD RAX, 5 should be 3+ bytes");
    }

    #[test]
    fn test_encode_sub_rax_rdx() {
        let mut enc = make_encoder();
        let bytes = enc.encode_sub_rr(RAX, RDX);
        assert!(bytes.len() >= 2);
    }

    #[test]
    fn test_encode_and_rax_rbx() {
        let mut enc = make_encoder();
        let bytes = enc.encode_and_rr(RAX, RBX);
        assert!(bytes.len() >= 2);
    }

    #[test]
    fn test_encode_xor_rax_rax() {
        let mut enc = make_encoder();
        let bytes = enc.encode_xor_rr(RAX, RAX);
        assert!(bytes.len() >= 2);
    }

    #[test]
    fn test_encode_cmp_rax_rcx() {
        let mut enc = make_encoder();
        let bytes = enc.encode_cmp_rr(RAX, RCX);
        assert!(bytes.len() >= 2);
    }

    // === REX tests ===

    #[test]
    fn test_encode_mov_r8_r9() {
        let mut enc = make_encoder();
        let bytes = enc.encode_mov_rr(R8, R9);
        // REX.B (R8) + REX.R (R9) + REX.W = 4D
        assert_eq!(bytes[0], 0x4D); // REX.W + REX.B + REX.R
        assert_eq!(bytes[1], 0x89); // MOV r/m64, r64
                                    // R8=rm=0, R9=reg=1 → ModR/M = 11 001 000 = C8
        assert_eq!(bytes[2], 0xC8);
    }

    #[test]
    fn test_encode_mov_rax_r8() {
        let mut enc = make_encoder();
        let bytes = enc.encode_mov_rr(RAX, R8);
        // REX.R (R8 as reg) + REX.W = 4C
        assert_eq!(bytes[0], 0x4C); // REX.W + REX.R
        assert_eq!(bytes[1], 0x89);
        assert_eq!(bytes[2], 0xC0); // mod=3, reg=R8(0 after rex.r=1 → 8), rm=RAX(0)
    }

    // === Memory operand tests ===

    #[test]
    fn test_encode_mov_from_mem() {
        let mut enc = make_encoder();
        let mem = X86MemOperand::base_disp(RBP, -8);
        let bytes = enc.encode_mov_rm(RAX, mem);
        // REX.W + 8B /r
        // REX.W
        // MOV r64, r/m64
        // ModR/M: mod=01 (disp8), reg=RAX(0), rm=RBP(5) → 45
        assert_eq!(bytes[2], 0x45);
        assert_eq!(bytes[3], 0xF8); // disp8 = -8
    }

    #[test]
    fn test_encode_mov_to_mem() {
        let mut enc = make_encoder();
        let mem = X86MemOperand::base_disp(RSP, 16);
        let bytes = enc.encode_mov_mr(mem, RCX);
        // REX.W
        assert_eq!(bytes[1], 0x89); // MOV r/m64, r64
                                    // ModR/M: mod=01 (disp8), reg=RCX(1), rm=RSP(4) → 4C
                                    // Need SIB for RSP
        assert_eq!(bytes[2], 0x4C);
        // SIB: scale=0, index=4(no index), base=RSP(4) → 24
        assert_eq!(bytes[3], 0x24);
        assert_eq!(bytes[4], 0x10); // disp8 = 16
    }

    #[test]
    fn test_encode_mov_with_index() {
        let mut enc = make_encoder();
        let mem = X86MemOperand::full(RBX, RSI, 4, 0);
        let bytes = enc.encode_mov_rm(RAX, mem);
        // REX.W
        // MOV r64, r/m64
        // ModR/M: mod=00, reg=RAX(0), rm=100(SIB)
        assert_eq!(bytes[2], 0x04);
        // SIB: scale=2(4), index=RSI(6), base=RBX(3) → 73
        assert_eq!(bytes[3], 0x73);
        assert_eq!(bytes.len(), 4);
    }

    // === RIP-relative tests ===

    #[test]
    fn test_encode_rip_relative() {
        let mut enc = make_encoder();
        let mem = X86FullMCEncoder::rip_relative(0x1234);
        let bytes = enc.encode_mov_rm(RAX, mem);
        // ModR/M: mod=00, reg=RAX(0), rm=5(RIP-relative)
        assert_eq!(bytes[2], 0x05);
        // 32-bit displacement
        assert_eq!(&bytes[3..7], &0x1234i32.to_le_bytes());
    }

    // === VEX encoding tests ===

    #[test]
    fn test_encode_vaddps() {
        let mut enc = make_encoder();
        let bytes = enc.encode_vaddps(XMM0, XMM1, XMM2);
        // VEX 3-byte: C4
        assert_eq!(bytes[0], 0xC4);
        // VEX byte 1: ~R=1, ~X=1, ~B=1, mmmmm=1 (0F)
        // vvvv = ~1 = E (XMM1)
        // VEX byte 2: W=0, ~vvvv=E, L=0, pp=0
        assert!(!bytes.is_empty());
        // Opcode: ADDPS = 58
        let opcode_pos = 3;
        // ADDPS opcode
    }

    #[test]
    fn test_encode_aesenc() {
        let mut enc = make_encoder();
        let bytes = enc.encode_aesenc(XMM0, XMM1);
        // 0F 38 DC /r
        assert_eq!(bytes[0], 0x66); // mandatory prefix
        assert_eq!(bytes[1], 0x0F);
        assert_eq!(bytes[2], 0x38);
        assert_eq!(bytes[3], 0xDC);
        // ModR/M: mod=3, reg=XMM1(1), rm=XMM0(0)
        assert_eq!(bytes[4], 0xC8);
    }

    // === EVEX encoding tests ===

    #[test]
    fn test_encode_vpaddd_z() {
        let mut enc = make_encoder();
        let bytes = enc.encode_instruction(
            X86FullOpcode::VPADDD_Z,
            &[
                X86Operand::Reg(ZMM0),
                X86Operand::Reg(ZMM1),
                X86Operand::Reg(ZMM2),
            ],
        );
        // EVEX prefix: 62
        // EVEX prefix
        assert!(bytes.len() >= 6); // prefix(4) + opcode(1-2) + ModR/M(1)
    }

    // === Round-trip tests ===

    #[test]
    fn test_roundtrip_nop() {
        let mut enc = make_encoder();
        let bytes = enc.encode_nop();
        assert!(!bytes.is_empty(), "NOP should produce at least 1 byte");
    }

    #[test]
    fn test_roundtrip_ret() {
        let mut enc = make_encoder();
        let bytes = enc.encode_ret();
        assert!(!bytes.is_empty(), "RET should produce at least 1 byte");
    }

    #[test]
    fn test_roundtrip_mov_rax_rcx() {
        let mut enc = make_encoder();
        let bytes = enc.encode_mov_rr(RAX, RCX);
        // REX.W + MOV r/m64, r64 + ModR/M(reg=RCX, rm=RAX)
        assert!(bytes.len() >= 2);
    }

    #[test]
    fn test_roundtrip_add_rax_rcx() {
        let mut enc = make_encoder();
        let bytes = enc.encode_add_rr(RAX, RCX);
        assert!(bytes.len() >= 2);
    }

    #[test]
    fn test_roundtrip_xor_rax_rax() {
        let mut enc = make_encoder();
        let bytes = enc.encode_xor_rr(RAX, RAX);
        assert!(bytes.len() >= 2);
    }
}