performance-aware/decode.h

#include "lib.h"

enum Mode
{
    MODE_MEM_NO_DIS = 0b00,
    MODE_MEM_DIS_08 = 0b01,
    MODE_MEM_DIS_16 = 0b10,
    MODE_RGSTR_MODE = 0b11,
};

typedef struct Register
{
    char* fullname;
    char* bytename;
    union {
        struct {
            char low;
            char high;
        };
        u16 full;
    } value;
    u8 code;
} Register;

Register registers[8] = {
    {.code = 0b000, .fullname = "ax", .bytename = "al"},
    {.code = 0b001, .fullname = "cx", .bytename = "cl"},
    {.code = 0b010, .fullname = "dx", .bytename = "dl"},
    {.code = 0b011, .fullname = "bx", .bytename = "bl"},
    {.code = 0b100, .fullname = "sp", .bytename = "ah"},
    {.code = 0b101, .fullname = "bp", .bytename = "ch"},
    {.code = 0b110, .fullname = "si", .bytename = "dh"},
    {.code = 0b111, .fullname = "di", .bytename = "bh"},
};

enum OperandType {OPR_T_MEMORY, OPR_T_REGISTER, OPR_T_IMMEDIATE, OPR_T_DIRADDR};

typedef struct Operand
{
    enum OperandType tag;
    union {
        struct Mem {
            char *eac_name;
            i16 displacement;
            u8 mode;
        } mem;
        struct Reg {
            Register value;
            bool wide;
        } reg;
        struct Imm {
            i16 value;
            u8 direct;
        } imm;
        struct DirAddr {
            i16 value;
        } dir_addr;
    };
} Operand;

enum ParseRegType { P_REG_NONE, P_REG_MASK, P_REG_FIXED };
typedef struct ParseReg
{
    enum ParseRegType tag;
    union {
        u8 none;
        u8 mask;
        u8 fixed;
    };
} ParseReg;

typedef struct InstFormat
{
    u16 id;
    char *name;
    ParseReg parse_reg;
    u8 inst_enc;
    u8 mask_inst;
    u8 mask_w;
    bool has_operands;
    bool has_displacement;
    bool has_data;
    bool has_d;
    bool has_w;
    bool has_mod;
    bool has_rm;
    bool has_s;
    bool has_SR;
} InstFormat;

typedef struct ParsedInstruction
{
    u16 id;
    char *name;
    u16_opt data;
    u16_opt displacement;
    u8_opt w;
    u8_opt d;
    u8_opt s;
    u8_opt mod;
    u8_opt reg;
    u8_opt rm;
    u8_opt SR;
    u8 is_data_addr;
    u8 bytes_read;
} ParsedInstruction;

typedef struct Instruction
{
    Operand src_opr;
    Operand dst_opr;
    i16 data;
    char *operation;
    u16 id;
} Instruction;

InstFormat inst_formats[] =
{
    ////////
    // MOV
    ////////
    // Register/memory to/from register
    {.id=1, .name="mov", .inst_enc=0b10001000, .mask_inst=0x3, .mask_w=0x1,
     .has_operands=true, .has_displacement=true, .has_d=true, .has_w=true,
     .has_mod=true, .has_rm=true, .parse_reg={.tag = P_REG_MASK, .mask=0b00111000} },
    // Immediate to register/memory
    {.id=2, .name="mov", .inst_enc=0b11000110, .mask_inst=0x1, .mask_w=0x1, .has_operands=true,
     .has_displacement=true, .has_data=true, .has_w=true, .has_mod=true, .has_rm=true},
    // Immediate to register
    {.id=3, .name="mov", .inst_enc=0b10110000, .mask_inst=0xF, .mask_w=0x8,
     .parse_reg={.tag = P_REG_MASK, .mask=0b00000111}, .has_data=true, .has_w=true},
    // Memory to accumulator | Accumulator to memory using the `d` bit
    // even though the manual doesn't specify it
    {.id=4, .name="mov", .inst_enc=0b10100000, .mask_inst=0x3, .mask_w=0x1, .has_data=true,
     .has_w=true, .has_d=true, .parse_reg={.tag = P_REG_FIXED, .fixed=0x0}},
    // Register/memory to segment register and inverse using the `d` bit
    {.id=5, .name="mov", .inst_enc=0b10001100, .mask_inst=0x3, .has_SR=true, .has_d=true,
     .has_displacement=true, .has_mod=true, .has_rm=true},
    ////////
    // ADD
    ////////
    // Reg/memory with register or either
    {.id=6, .name="add", .inst_enc=0b00000000, .mask_inst=0x3, .has_displacement=true,
      .mask_w=0x1, .has_operands=true, .has_w=true, .has_d=true, .has_mod=true,
      .has_rm=true, .parse_reg={.tag = P_REG_MASK, .mask=0b00111000}},
    // Immediate to register/memory
    {.id=7, .name="add", .inst_enc=0b10000000, .mask_inst=0x3, .mask_w=0x1, .has_w=true,
     .has_operands=true, .has_displacement=true, .has_data=true, .has_mod=true, .has_rm=true},
    {.id=8, .name="add", .inst_enc=0b00000100, .mask_inst=0x1, .mask_w=0x1,
     .has_data=true, .has_w=true, .parse_reg={.tag = P_REG_FIXED, .fixed=0x0}},
};