X-Git-Url: https://git.rrq.au/?a=blobdiff_plain;f=main.asm;h=d0c43917ae4971d8961f3d6b02d9030b95c90753;hb=1013709c277143b58deafcf9a1faccd3e9b799a2;hp=8d9c51b77573f2da465b50914b6574acb1f29679;hpb=6345a1a92698a72f5865e8e04dbc4bd14858e747;p=rrq%2Fjonasforth.git diff --git a/main.asm b/main.asm index 8d9c51b..d0c4391 100644 --- a/main.asm +++ b/main.asm @@ -56,11 +56,9 @@ macro forth_asm label, name { ;; 'dq' statements.) macro forth label, name { header label, name - dq docol + dq DOCOL } - - segment readable executable entry main @@ -79,13 +77,13 @@ program: dq MAIN ;; The codeword is the code that will be executed at the beginning of a forth ;; word. It needs to save the old RSI and update it to point to the next word to ;; execute. -docol: +header DOCOL, 'DOCOL' pushr rsi ; Save old value of RSI on return stack; we will continue execution there after we are done executing this word lea rsi, [rax + 8] ; RAX currently points to the address of the codeword, so we want to continue at RAX+8 next ; Execute word pointed to by RSI ;; This word is called at the end of a Forth definition. It just needs to -;; restore the old value of RSI (saved by 'docol') and resume execution. +;; restore the old value of RSI (saved by 'DOCOL') and resume execution. forth_asm EXIT, 'EXIT' popr rsi next @@ -242,15 +240,55 @@ forth HELLO, 'HELLO' dq NEWLINE dq EXIT +;; Duplicate a pair of elements. +forth_asm PAIRDUP, '2DUP' + pop rbx + pop rax + push rax + push rbx + push rax + push rbx + next + +;; Swap the top two elements on the stack. +forth_asm SWAP, 'SWAP' + pop rax + pop rbx + push rax + push rbx + next + +;; Remove the top element from the stack. +forth_asm DROP, 'DROP' + add rsp, 8 + next + ;; The INTERPRET word reads and interprets user input. It's behavior depends on ;; the current STATE. It provides special handling for integers. (TODO) forth INTERPRET, 'INTERPRET' + ;; Read word dq READ_WORD - dq FIND + dq PAIRDUP + ;; Stack is (word length word length). + dq FIND ; Try to find word + dq DUP_ + dq ZBRANCH, 8 * 8 ; Check if word is found + + ;; Word is found, execute it dq TCFA + ;; Stack is (word length addr) + dq SWAP, DROP + dq SWAP, DROP + ;; Stack is (addr) dq EXEC dq EXIT + ;; No word is found, assume it is an integer literal + ;; Stack is (word length addr) + dq DROP + dq PARSE_NUMBER + dq EXIT + ;; .U prints the value on the stack as an unsigned integer in hexadecimal. forth_asm DOTU, '.U' mov [.length], 0 @@ -312,6 +350,125 @@ forth_asm DOTU, '.U' pop rsi next +;; Takes a value and an address, and stores the value at the given address. +forth_asm PUT, '!' + pop rbx ; Address + pop rax ; Value + mov [rbx], rax + next + +;; Takes an address and returns the value at the given address. +forth_asm GET, '@' + pop rax + mov rax, [rax] + push rax + next + +;; Add two integers on the stack. +forth_asm PLUS, '+' + pop rax + pop rbx + add rax, rbx + push rax + next + +;; Calculate difference between two integers on the stack. The second number is +;; subtracted from the first. +forth_asm MINUS, '-' + pop rax + pop rbx + sub rbx, rax + push rbx + next + +;; Get the location of the STATE variable. It can be set with '!' and read with +;; '@'. +forth STATE, 'STATE' + dq LIT, var_STATE + dq EXIT + +;; Get the location of the LATEST variable. It can be set with '!' and read with +;; '@'. +forth LATEST, 'LATEST' + dq LIT, latest_entry + dq EXIT + +;; Get the location at which compiled words are expected to be added. This +;; pointer is usually modified automatically when calling ',', but we can also +;; read it manually with 'HERE'. +forth HERE, 'HERE' + dq LIT, here + dq EXIT + +forth COMMA, ',' + dq HERE, GET, PUT ; Set the memory at the address pointed to by HERE + dq HERE, GET, LIT, 8, PLUS ; Calculate new address for HERE to point to + dq HERE, PUT ; Update HERE to point to the new address + dq EXIT + +;; Read user input until next " character is found. Push a string containing the +;; input on the stack as (buffer length). Note that the buffer is only valid +;; until the next call to S" and that no more than 255 character can be read. +forth_asm READ_STRING, 'S"' + push rsi + + mov [.length], 0 + +.read_char: + mov rax, 0 + mov rdi, 0 + mov rsi, .char_buffer + mov rdx, 1 + syscall + + mov al, [.char_buffer] + cmp al, '"' + je .done + + mov rdx, .buffer + add rdx, [.length] + mov [rdx], al + inc [.length] + jmp .read_char + +.done: + pop rsi + + push .buffer + push [.length] + + next + +;; CREATE inserts a new header in the dictionary, and updates LATEST so that it +;; points to the header. To compile a word, the user can then call ',' to +;; continue to append data after the header. +;; +;; It takes the name of the word as a string (address length) on the stack. +forth_asm CREATE, 'CREATE' + pop rcx ; Word string length + pop rdx ; Word string pointer + + mov rdi, [here] ; rdi = Address at which to insert this entry + mov rax, [latest_entry] ; rax = Address of the previous entry + mov [rdi], rax ; Insert link to previous entry + mov [latest_entry], rdi ; Update LATEST to point to this word + + add rdi, 8 + mov [rdi], rcx ; Insert length + + ;; Insert word string + add rdi, 1 + + push rsi + mov rsi, rdx ; rsi = Word string pointer + rep movsb + pop rsi + + ;; Update HERE + mov [here], rdi + + next + forth MAIN, 'MAIN' dq HELLO dq INTERPRET @@ -320,19 +477,34 @@ forth MAIN, 'MAIN' segment readable writable +;; The LATEST variable holds a pointer to the word that was last added to the +;; dictionary. This pointer is updated as new words are added, and its value is +;; used by FIND to look up words. latest_entry dq initial_latest_entry +;; The STATE variable is 0 when the interpreter is executing, and non-zero when +;; it is compiling. +var_STATE dq 0 + FIND.rsi dq ? READ_WORD.rsi dq ? READ_WORD.rbp dq ? +READ_STRING.char_buffer db ? +READ_STRING.buffer rb $FF +READ_STRING.length dq ? + DOTU.chars db '0123456789ABCDEF' DOTU.buffer rq 16 ; 64-bit number has no more than 16 digits in hex DOTU.rbuffer rq 16 DOTU.length dq ? DOTU.printed_length dq ? +;; Reserve space for compiled words, accessed through HERE. +here dq here_top +here_top rq $2000 + ;; Return stack rq $2000 return_stack_top: