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/* ========================================================================
(C) Copyright 2023 by Molly Rocket, Inc., All Rights Reserved.
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Please see https://computerenhance.com for more information
======================================================================== */
enum instruction_bits_usage : u8
{
Bits_End, // NOTE(casey): The 0 value, indicating the end of the instruction encoding array
Bits_Literal, // NOTE(casey): These are opcode bits that identify instructions
// NOTE(casey): These bits correspond directly to the 8086 instruction manual
Bits_D,
Bits_S,
Bits_W,
Bits_V,
Bits_Z,
Bits_MOD,
Bits_REG,
Bits_RM,
Bits_SR,
Bits_Disp,
Bits_Data,
Bits_DispAlwaysW, // NOTE(casey): Tag for instructions where the displacement is always 16 bits
Bits_WMakesDataW, // NOTE(casey): Tag for instructions where SW=01 makes the data field become 16 bits
Bits_RMRegAlwaysW, // NOTE(casey): Tag for instructions where the register encoded in RM is always 16-bit width
Bits_RelJMPDisp, // NOTE(casey): Tag for instructions that require address adjustment to go through NASM properly
Bits_Far, // NOTE(casey): Tag for instructions that require a "far" keyword in their ASM to select the right opcode
Bits_Count,
};
struct instruction_bits
{
instruction_bits_usage Usage;
u8 BitCount;
u8 Shift;
u8 Value;
};
struct instruction_encoding
{
operation_type Op;
instruction_bits Bits[16];
};
struct instruction_table
{
instruction_encoding *Encodings;
u32 EncodingCount;
u32 MaxInstructionByteCount;
};
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