Incomplete, but I want to make sure the ideas I have here don't get wiped. Sadly this commit won't compile.

src/opcodes.c

@@ -18,7 +18,7 @@ Instruction instructions[OPCODECOUNT] = {
     { "call", CALL, Address, None}
 };
 
-unsigned char GetInstructionMask(TokenType type) {
+unsigned char GetInstructionMask(Mnemonic type) {
     switch (type) {
         case COPY:
             return 0x20; //0b00100000; ORing 0x80 marks the first parameter as an address
@@ -93,7 +93,7 @@ Register registers[REGISTERCOUNT] = {
     { "r8", R8 }
 };
 
-const Instruction* GetOpcodeDetails(TokenType type) {
+const Instruction* GetOpcodeDetails(Mnemonic type) {
     for(int i = 0; i < OPCODECOUNT; i++) {
         if (instructions[i].op == type) return &instructions[i];
     }
@@ -101,12 +101,12 @@ const Instruction* GetOpcodeDetails(TokenType type) {
     return NULL;
 }
 
-int IsOpcode(const char* text, TokenType* opcode) {
+int IsOpcode(const char* text, Mnemonic* opcode) {
     if (!text) return 0;
 
     for(int i = 0; i < OPCODECOUNT; i++) {
-        if (strcmp(instructions[i].lexeme, text) == 0) {
-            if (opcode) *opcode = instructions[i].op;
+        if (strcmp(instructions[i], text) == 0) {
+            if (opcode) *opcode = instructions[i].Mnemonic;
             return 1;
         }
     }
@@ -114,15 +114,13 @@ int IsOpcode(const char* text, TokenType* opcode) {
     return 0;
 }
 
-int IsRegister(const char* text, TokenType* reg) {
+int IsRegister(const char* text, Registers* reg) {
     if (!text) return 0;
 
-    for(int i = 0; i < REGISTERCOUNT; i++) {
-        if (strcmp(registers[i].lexeme, text) == 0)  {
-            *reg = registers[i].type;
-            return 1;
-        }
-    }
+    int length = strlen(text);
 
-    return 0;
+    if (length != 2) return 0;
+    if (text[0] != 'r') return 0;
+
+    return text[1] >= '1' && text[1] <= '8';
 }