From 2cd770b4f9a46cbc7ff07b26f4851bba1ea36a7d Mon Sep 17 00:00:00 2001 From: Jonas Hvid Date: Sat, 30 Nov 2019 18:35:28 +0100 Subject: [PATCH] Move some assembly functions to separate module --- Makefile | 2 +- impl.asm | 160 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ main.asm | 141 ++++++++---------------------------------------- 3 files changed, 183 insertions(+), 120 deletions(-) create mode 100644 impl.asm diff --git a/Makefile b/Makefile index 70cb7cd..5832cb6 100644 --- a/Makefile +++ b/Makefile @@ -1,4 +1,4 @@ -main: main.asm +main: main.asm impl.asm fasm $< $@ .PHONY: clean diff --git a/impl.asm b/impl.asm new file mode 100644 index 0000000..f8093d0 --- /dev/null +++ b/impl.asm @@ -0,0 +1,160 @@ +segment readable executable + +;; Find the given word in the dictionary of words. If no such word exists, +;; return 0. +;; +;; Parameters: +;; * [find.search_length] = Length of the word in bytes. +;; * [find.search_buffer] = Pointer to the string containing the word. +;; * rsi = Pointer to the last entry in the dictionary. +;; +;; Results: +;; * rsi = Pointer to the found entry in the dictionary or 0. +;; +;; Clobbers rcx, rdx, rdi, rax. +find: + ;; RSI contains the entry we are currently looking at +.loop: + movzx rcx, byte [rsi + 8] ; Length of word being looked at + cmp rcx, [.search_length] + jne .next ; If the words don't have the same length, we have the wrong word + + ;; Otherwise, we need to compare strings + lea rdx, [rsi + 8 + 1] ; Location of character being compared in entry + mov rdi, [.search_buffer] ; Location of character being compared in search buffer +.compare_char: + mov al, [rdx] + mov ah, [rdi] + cmp al, ah + jne .next ; They don't match; try again + inc rdx ; These characters match; look at the next ones + inc rdi + loop .compare_char + + jmp .found ; They match! We are done. + +.next: + mov rsi, [rsi] ; Look at the previous entry + cmp rsi, 0 + jnz .loop ; If there is no previous word, exit and return 0 + +.found: + ret + +;; Read a word from standard input. Returns pointer to string containing word as +;; well as length. +;; +;; Results: +;; * rdx = Length of string +;; * rdi = Pointer to string buffer +;; +;; Clobbers pretty much everything. +read_word: +.skip_whitespace: + ;; Read characters into .char_buffer until one of them is not whitespace. + mov rax, 0 + mov rdi, 0 + mov rsi, .char_buffer + mov rdx, 1 + syscall + + ;; We consider newlines and spaces to be whitespace. + cmp [.char_buffer], ' ' + je .skip_whitespace + cmp [.char_buffer], $A + je .skip_whitespace + +.alpha: + ;; We got a character that wasn't whitespace. Now read the actual word. + mov [.length], 0 + +.read_alpha: + mov al, [.char_buffer] + movzx rbx, [.length] + mov rsi, .buffer + add rsi, rbx + mov [rsi], al + inc [.length] + + mov rax, 0 + mov rdi, 0 + mov rsi, .char_buffer + mov rdx, 1 + syscall + + cmp [.char_buffer], ' ' + je .end + cmp [.char_buffer], $A + jne .read_alpha + +.end: + mov rdi, .buffer + movzx rdx, [.length] + + ret + +;; Parses a string. +;; +;; Parameters: +;; * [.length] = Length of string +;; * [.buffer] = Pointer to string buffer +;; +;; Results: +;; * rax = Value +;; +;; Clobbers +parse_number: + mov r8, 0 ; Result + + ;; Add (10^(rcx-1) * parse_char(rdi[length - rcx])) to the accumulated value + ;; for each rcx. + mov rcx, [.length] +.loop: + ;; First, calcuate 10^(rcx - 1) + mov rax, 1 + + mov r9, rcx + .exp_loop: + dec r9 + jz .break + mov rbx, 10 + mul rbx + jmp .exp_loop + .break: + + ;; Now, rax = 10^(rcx - 1). + + ;; We need to calulate the value of the character at rdi[length - rcx]. + mov rbx, rdi + add rbx, [.length] + sub rbx, rcx + movzx rbx, byte [rbx] + sub rbx, '0' + + ;; Multiply this value by rax to get (10^(rcx-1) * parse_char(rdi[length - rcx])), + ;; then add this to the result. + mul rbx + + ;; Add that value to r8 + add r8, rax + + dec rcx + jnz .loop + + mov rax, r8 + ret + + +segment readable writable + +find.search_length dq ? +find.search_buffer dq ? + +read_word.max_size = $FF +read_word.buffer rb read_word.max_size +read_word.length db ? +read_word.char_buffer db ? + +parse_number.buffer dq ? +parse_number.length dq ? + diff --git a/main.asm b/main.asm index 3187d04..21a911c 100644 --- a/main.asm +++ b/main.asm @@ -59,8 +59,14 @@ macro forth label, name { dq docol } + + segment readable executable +entry main + +include "impl.asm" + main: cld ; Clear direction flag so LODSQ does the right thing. mov rbp, return_stack_top ; Initialize return stack @@ -95,37 +101,15 @@ forth_asm LIT, 'LIT' ;; dictionary entry for that word. If no such word exists, return 0. forth_asm FIND, 'FIND' mov [.rsi], rsi - pop [.search_length] - pop [.search_buffer] - ;; RSI contains the entry we are currently looking at + pop [find.search_length] + pop [find.search_buffer] mov rsi, [latest_entry] ; Start with the last added word + call find + push rsi -.loop: - movzx rcx, byte [rsi + 8] ; Length of word being looked at - cmp rcx, [.search_length] - jne .next ; If the words don't have the same length, we have the wrong word - - ;; Otherwise, we need to compare strings - lea rdx, [rsi + 8 + 1] ; Location of character being compared in entry - mov rdi, [.search_buffer] ; Location of character being compared in search buffer -.compare_char: - mov al, [rdx] - mov ah, [rdi] - cmp al, ah - jne .next ; They don't match; try again - inc rdx ; These characters match; look at the next ones - inc rdi - loop .compare_char - - jmp .found ; They match! We are done. - -.next: - mov rsi, [rsi] ; Look at the previous entry - cmp rsi, 0 - jnz .loop ; If there is no previous word, exit and return 0 - -.found: + mov rsi, [.rsi] + next push rsi mov rsi, [.rsi] @@ -200,98 +184,25 @@ forth SPACE, 'SPACE' ;; size. The pointer is valid until the next call to READ_WORD. forth_asm READ_WORD, 'READ-WORD' mov [.rsi], rsi - mov [.rax], rax -.skip_whitespace: - ;; Read characters into .char_buffer until one of them is not whitespace. - mov rax, 0 - mov rdi, 0 - mov rsi, .char_buffer - mov rdx, 1 - syscall - - cmp [.char_buffer], ' ' - je .skip_whitespace - cmp [.char_buffer], $A - je .skip_whitespace - -.alpha: - ;; We got a character that wasn't whitespace. Now read the actual word. - mov [.length], 0 - -.read_alpha: - mov al, [.char_buffer] - movzx rbx, [.length] - mov rsi, .buffer - add rsi, rbx - mov [rsi], al - inc [.length] - - mov rax, 0 - mov rdi, 0 - mov rsi, .char_buffer - mov rdx, 1 - syscall - - cmp [.char_buffer], ' ' - je .end - cmp [.char_buffer], $A - jne .read_alpha - -.end: - push .buffer - movzx rax, [.length] - push rax + call read_word + push rdi ; Buffer + push rdx ; Length mov rsi, [.rsi] - mov rax, [.rax] - next ;; Takes a string on the stack and replaces it with the decimal number that the ;; string represents. forth_asm PARSE_NUMBER, 'PARSE-NUMBER' - pop [.length] ; Length - pop rdi ; String pointer - mov r8, 0 ; Result - - ;; Add (10^(rcx-1) * parse_char(rdi[length - rcx])) to the accumulated value - ;; for each rcx. - mov rcx, [.length] -.loop: - ;; First, calcuate 10^(rcx - 1) - mov rax, 1 + pop [parse_number.length] ; Length + pop [parse_number.buffer] ; String pointer - mov r9, rcx - .exp_loop: - dec r9 - jz .break - mov rbx, 10 - mul rbx - jmp .exp_loop - .break: - - ;; Now, rax = 10^(rcx - 1). - - ;; We need to calulate the value of the character at rdi[length - rcx]. - mov rbx, rdi - add rbx, [.length] - sub rbx, rcx - movzx rbx, byte [rbx] - sub rbx, '0' - - ;; Multiply this value by rax to get (10^(rcx-1) * parse_char(rdi[length - rcx])), - ;; then add this to the result. - mul rbx - - ;; Add that value to r8 - add r8, rax - - dec rcx - jnz .loop - - push r8 + push rsi + call parse_number + pop rsi + push rax ; Result next forth READ_NUMBER, 'READ-NUMBER' @@ -402,16 +313,10 @@ segment readable writable latest_entry dq initial_latest_entry -FIND.search_length dq ? -FIND.search_buffer dq ? FIND.rsi dq ? READ_WORD.rsi dq ? -READ_WORD.rax dq ? -READ_WORD.max_size = $FF -READ_WORD.buffer rb READ_WORD.max_size -READ_WORD.length db ? -READ_WORD.char_buffer db ? +READ_WORD.rbp dq ? DOTU.chars db '0123456789ABCDEF' DOTU.buffer rq 16 ; 64-bit number has no more than 16 digits in hex @@ -419,8 +324,6 @@ DOTU.rbuffer rq 16 DOTU.length dq ? DOTU.printed_length dq ? -PARSE_NUMBER.length dq ? - ;; Return stack rq $2000 return_stack_top: -- 2.39.2