working kinda
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nub31
208
input/baseline/gc.asm
Normal file
208
input/baseline/gc.asm
Normal file
@@ -0,0 +1,208 @@
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global gc_init, gc_alloc, gc_free, gc_collect
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extern itoa
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extern str_len
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section .bss
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alloc_list: resq 1
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stack_start: resq 1
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; TMP
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section .data
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newline: db 10, 0
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start_mark: db "Starting to mark", 0
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marked: db "Marked object", 0
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; /TMP
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section .text
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; TMP
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print_int:
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push rbp
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mov rbp, rsp
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sub rsp, 8
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mov [rbp - 8], rdi
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mov rax, [rbp - 8]
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push rax
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pop rdi
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call itoa
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push rax
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pop rdi
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call print
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mov rdi, newline
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call print
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mov rsp, rbp
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pop rbp
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ret
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print:
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push rbp
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mov rbp, rsp
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sub rsp, 8
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mov [rbp - 8], rdi
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mov rax, 1
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push rax
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mov rax, 1
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push rax
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mov rax, [rbp - 8]
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push rax
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mov rax, [rbp - 8]
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push rax
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pop rdi
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call str_len
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push rax
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pop rdx
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pop rsi
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pop rdi
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pop rax
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syscall
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mov rsp, rbp
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pop rbp
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ret
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; /TMP
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gc_init:
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mov [stack_start], rsp
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ret
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gc_alloc:
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add rdi, 17 ; add space for metadata
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push rdi
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call sys_mmap ; allocate size + metadata
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pop rdi
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mov byte [rax], 0 ; set mark to 0
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mov qword [rax + 1], rdi ; set total size of object (including metadata)
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mov rsi, [alloc_list] ; load first item in allocation list
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mov qword [rax + 9], rsi ; make current head of allocation list the next item in this object
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mov [alloc_list], rax ; update head of allocation list so it points to this object
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add rax, 17 ; skip metadata for return value
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ret
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; Generated by chatgpt. Rewrite this later
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; TODO: refactor to unlink easier
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gc_free:
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mov rsi, [alloc_list] ; Load head of allocation list
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test rsi, rsi ; Check if list is empty
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jz .not_found ; If empty, nothing to free
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cmp rsi, rdi ; Is the first item the one to free?
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je .remove_head ; If so, update head directly
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.loop:
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mov rdx, [rsi + 9] ; Load next item in list
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test rdx, rdx ; Check if end of list
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jz .not_found ; If not found, return
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cmp rdx, rdi ; Is this the item to remove?
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je .remove_item ; If so, unlink it
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mov rsi, rdx ; Move to next item
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jmp .loop ; Repeat
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.remove_head:
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mov rdx, [rdi + 9] ; Get next item
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mov [alloc_list], rdx ; Update head of list
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jmp .free_memory ; Free the object
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.remove_item:
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mov rdx, [rdi + 9] ; Get next item
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mov [rsi + 9], rdx ; Bypass rdi in the list
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.free_memory:
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mov rsi, [rdi + 1] ; Get object size
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call sys_munmap ; Free memory
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ret
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.not_found:
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ret ; Item not found, do nothing
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gc_collect:
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call gc_mark_stack
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call gc_sweep
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ret
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gc_mark_stack:
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mov r8, rsp ; load current stack pointer
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mov r9, [stack_start] ; load start of stack
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.loop:
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cmp r8, r9 ; have we reached end of stack?
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ja .done ; yes? return
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mov rdi, [r8] ; no? load the value
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call gc_mark ; this might be an allocation, check
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add r8, 8 ; next item in stack
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jmp .loop
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.done:
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ret
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gc_mark:
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test rdi, rdi ; is input null?
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jz .done ; yes? return
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mov rsi, [alloc_list] ; load start of allocation list
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.loop:
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test rsi, rsi ; reached end of list?
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jz .done ; yes? return
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lea rdx, [rsi + 17]
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cmp rdx, rdi ; no? is this the input object?
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je .mark_object ; yes? mark it
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mov rsi, [rsi + 9] ; no? next item
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jmp .loop
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.mark_object:
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mov al, [rdi] ; load mark
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test al, al ; already marked?
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jnz .done ; yes? return
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mov byte [rdi - 17], 1 ; mark object
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mov rcx, [rdi + 1] ; load object size
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lea rdx, [rdi + 17] ; start of data
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add rcx, rdx ; end of data
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.scan_object:
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cmp rdx, rcx ; done scanning?
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jae .done ; yes? return
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mov rdi, [rbx] ; load value
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call gc_mark
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add rdx, 8 ; next object
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jmp .scan_object
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.done:
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ret
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gc_sweep:
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mov rdi, [alloc_list]
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.loop:
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test rdi, rdi ; reached end of list?
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jz .done ; yes? return
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mov al, [rdi]
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test al, al ; is object marked?
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jz .free ; no? free it
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mov byte [rdi], 0 ; yes? clear mark for next scan
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mov rdi, [rdi + 9]
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jmp .loop
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.free:
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mov rcx, [rdi + 9]
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push rcx
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call gc_free
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pop rdi
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jmp .loop
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.done:
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ret
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sys_mmap:
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mov rax, 9
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mov rsi, rdi
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mov rdi, 0
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mov rdx, 3
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mov r10, 34
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mov r8, -1
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mov r9, 0
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syscall
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cmp rax, -1
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je .error
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ret
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.error:
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mov rax, 60
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mov rdi, 1
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syscall
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sys_munmap:
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mov rax, 11
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syscall
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cmp rax, -1
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je .error
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ret
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.error:
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mov rax, 60
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mov rdi, 1
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syscall
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