From 55c426631bab8e356d0246bb140deeb0b6fcfb89 Mon Sep 17 00:00:00 2001
From: andromeda <andromeda@lenovo>
Date: Sat, 21 Mar 2026 21:42:50 +0100
Subject: [PATCH] correctly handle [register]s as operands

---
 twasm/README.md    | 17 +++++++++--------
 twasm/asm/main.asm | 32 ++++++++++++++++++++++----------
 2 files changed, 31 insertions(+), 18 deletions(-)

diff --git a/twasm/README.md b/twasm/README.md
index c2cc263..3f63fe7 100644
--- a/twasm/README.md
+++ b/twasm/README.md
@@ -306,8 +306,8 @@ supported tokens are listed below
 | cr8   | 0x004E | |
 | hlt   | 0x004F | |
 | int3  | 0x0050 | |
-| [     | 0x0051 | open bracket placeholder; 0x10XX should be used in contexts where the surrounding tokens can be known |
-| ]     | 0x0052 | |
+|       | 0x0051 | deprecated; formerly `[`. Now `0x10XX` is used. |
+|       | 0x0052 | deprecated; formerly `]`. |
 | xor   | 0x0053 | |
 | inc   | 0x0054 | |
 | dec   | 0x0055 | |
@@ -323,14 +323,15 @@ supported tokens are listed below
 | jg    | 0x005F | |
 | jle   | 0x0060 | |
 | jl    | 0x0061 | |
-| +     | 0x0062 | |
-| -     | 0x0063 | |
-| *     | 0x0064 | |
-| /     | 0x0065 | |
-| [     | 0x10XX | open bracket with `XX` bytes until the closing bracket |
-|       | 0xFEXX | token terminator byte as token, where `XX` is the byte |
+|       | 0x10XX | some memory address; `XX` is as specified below |
 |       | 0xFFFF | unrecognised token |
 
+values of `XX` in `0x10XX`:
+
+|  XX  | description |
+|------|-------------|
+| 0x00 | following byte is the token ID of some register |
+
 ### example program
 
 #### program in assembly
diff --git a/twasm/asm/main.asm b/twasm/asm/main.asm
index b0e7cad..a6885be 100644
--- a/twasm/asm/main.asm
+++ b/twasm/asm/main.asm
@@ -470,7 +470,7 @@ tokenise:
 
   .loop:
     cmp rdi, rsi ; if current byte greater than last byte
-    jg .break    ; then break
+    jge .break    ; then break
 
     mov dl, [rdi] ; dl = current byte
 
@@ -488,8 +488,8 @@ tokenise:
     push rax
     push rdx
     ; TODO probably should not ignore null bytes
-    mov rsi, whitespace_3 ; rsi -> list of whitespace (ignored) bytes
-    mov rdi,            3 ; rdi = size of list in bytes
+    mov rsi, whitespace_2 ; rsi -> list of whitespace (ignored) bytes
+    mov rdi,            2 ; rdi = size of list in bytes
                           ; dl = current byte
     call elemb
     ; al = 0 if not whitespace, 1 if whitespace
@@ -671,18 +671,32 @@ tokenise:
     mov rcx, rax ; rcx = evaluate_operand's return value
     pop rax      ; rax = number of tokens processed
 
-    ; operand is a register
+    ; operand is some reg
     ; cx = token ID
     cmp dl, 0x00
     je .operand_register
 
+    ; operand is some [reg]
+    ; cx = token ID
+    cmp dl, 0x10
+    je .operand_addr_register
+
     jmp .unexpected_operand
 
+  ; cx = token ID
   .operand_register:
     mov [TOKEN_TABLE_ADDR + rax * TOKEN_TABLE_ENTRY_SIZE], cx
     inc rax ; another token processed
     jmp .operand_break_continue
 
+  ; cx = token ID
+  .operand_addr_register
+    mov word [TOKEN_TABLE_ADDR + rax * TOKEN_TABLE_ENTRY_SIZE], 0x1000
+    inc rax ; 0x1000: addr reg token, next token is the register
+    mov [TOKEN_TABLE_ADDR + rax * TOKEN_TABLE_ENTRY_SIZE], cx
+    inc rax ; the register as returned by evaluate_operand
+    jmp .operand_break_continue
+
   .operand_break_continue:
     mov byte [.expecting], E_COMMENT | E_NEWLINE | E_WHITESPACE | E_COMMA
     jmp .loop
@@ -833,8 +847,6 @@ evaluate_operand:
     mov dl, 0xFF
     ret
 
-  .msg db "evaluate_operand", 0x0A, 0x00
-
 ; ------------------------------------------------------------------------------
 ; evaluate_constant
 ;
@@ -1232,8 +1244,8 @@ trim_trailing_whitespace:
   push rsi
 
   mov dl, [rsi + rdi - 1] ; last element of given list
-  mov rsi, whitespace_3   ; pointer of whitespace list
-  mov rdi, 3              ; length of whitespace list
+  mov rsi, whitespace_2   ; pointer of whitespace list
+  mov rdi,            2   ; length of whitespace list
   call elemb
 
   pop rsi ; rsi -> start of list
@@ -1553,7 +1565,7 @@ msg_halt db "halted.", 0x0A, 0x00
 
 token_terminator_8 db 0x00, " ", 0x0A, 0x0D, ",", 0x00, 0x00, 0x00
 
-whitespace_3 db " ", 0x0D, 0x00
+whitespace_2 db " ", 0x0D
 
 ; test program
 program:
@@ -1561,5 +1573,5 @@ program:
   db "inc rax ; inline comment", 0x0A
   db "; one line comment", 0x0A
   db "mov [rax], rdx", 0x0A
-  db "hlt", 0x00 ; for the sake of being able to print it, I made it a string
+  db "hlt"
   .size db $ - program