Started implementing the 8086 simulation

8086_sim/include/sim86_instruction_table.h

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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
+
+   ======================================================================== */
+
+#include "sim86.h"
+#include "sim86_instruction.h"
+
+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;
+};