アセンブリで brainfuck 書いてみた

README.md

たぶん Mountain Lion でしか動きません。自分の環境でしかテストしてない

compile:

$ as -o brainfuck.o brainfuck.s && ld -o brainfuck -e main brainfuck.o

run:

$ ./brainfuck -e "+++++++++[>++++++++>+++++++++++>+++++<<<-]>.>++.+++++++..+++.>-.------------.<++++++++.--------.+++.------.--------.>+."

;; -f でファイルから読み取れるようにしようと思ったけど力つきた

brainfuck.s

/*                                                                      *\ 
**     __________                  brainfuck.s                          **
**    / -. \  __/    ____          Maybe running only on                **
**   / `-'_/ /_     / __/          Mac OS X Mountain Lion               **
**  / /_) ) __/__ __\ \            http://twitter.com/pasberth          **
** /____ / /  /_//____/                                                 **
\*     /__/                                                             */

	.comm memory, 30000
	.text
	.globl main
invalidOptionMsg:	.ascii "invalid flag: "
main:
	popq	%rax		// %rax = argc
	cmp	$1,	%rax 	// if (argc == 1)
	jz	exit		//   goto exit;
	cmp	$2,	%rax	// else if (argc != 2)
	jnz	parseOption	//   goto parseOption;
	jmp	execProgram	// else goto execProgram;
parseOption:
checkHyphen:	
	movq	8(%rsp), %rax	// %rax = argv[1]
	movb	0(%rax), %al	// %al = *argv[1]
	cmp	$'-,	%al	// if (*argv[1] != '-')
	jnz	invalidOption	//   goto invalidOption;
extractOption:
	movq	8(%rsp), %rax	// %rax = argv[1]
	movb	1(%rax), %al	// %al = argv[1][1]
	cmpb	$'f,	%al	// from file
	jz	fromFile
	cmpb	$'e,	%al	// eval expr
	jz	evalExpr
	jmp	invalidOption
invalidOption:
	/* for example, if the input is "./brainfuck -x a",  *
	 * does print "invalid flag: x" and exit program.    */
	movq    $0x2000004, %rax
	movq	$1,	%rdi
	leaq	invalidOptionMsg(%rip), %rsi
	movq	$14,	%rdx
	syscall
	movq	8(%rsp), %rbx	// %rbx = argv[1]
	leaq	1(%rbx), %rax	// %rax = argv[1] + 1
	movq	%rax,	%rsi
	movq    $0x2000004, %rax
	movq	$1,	%rdi
	movq	$1,	%rdx
	syscall
	jmp	exit
fromFile:
	jmp	exit
evalExpr:
	push	%rax
	movq	24(%rsp), %rax
	call	brainfuck
	pop	%rax
	jmp	exit
execProgram:	
	jmp	exit
exit:
	movq    $0x2000001, %rax
	movq	$0, %rdi
	syscall
	ret
/*
 * %rax: brainfuck program.
 */
brainfuck:
	pushq	%rbp
	movq	%rsp,	%rbp
	pushq	%rbx
	movq	%rax,	%rbx
	pushq	%rax
	movq	%rbx,	%rax
	leaq	memory(%rip),	%rbx
	pushq	%rbx
	pushq	%rax
/*
 * 16(%rsp) : 
 * 8(%rsp)  : pointer to a memory
 * 0(%rsp)  : brainfuck program.
 */
eval:
	movq	(%rsp),	%rax
	cmp	$0,	%rax
	jz done

	movb	(%rax),	%al
	cmpb	$0,	%al
	jz done

	cmpb	$',,	%al
	jz getCh
	cmpb	$'.,	%al
	jz putCh
	cmpb	$'+,	%al
	jz incrVal
	cmpb	$'-,	%al
	jz declVal
	cmpb	$'<,	%al
	jz decrPtr
	cmpb	$'>,	%al
	jz incrPtr
	cmpb	$'[,	%al
	jz begWhile
	cmpb	$'],	%al
	jz endWhile
	jmp	next
done:
	popq	%rax
	popq	%rbx
	popq	%rax
	popq	%rbx
	leave
	ret
next:
	incb	(%rsp)
	jmp	eval
getCh:
	pushq	%rbx
	pushq	%rax	// input buffer
	movq    $0x2000003,	%rax
	movq    $0,	%rdi
	movq	%rsp,	%rsi
	movq 	$1,	%rdx
	syscall
	movq	(%rsp),	%rax
	movq	24(%rsp),	%rbx
	movq	%rax,	(%rbx)
	popq	%rax
	popq	%rbx
	jmp	next
putCh:
	pushq	%rbx
	pushq	%rax
	movq	24(%rsp),	%rbx
	movq    $0x2000004,	%rax
	movq	$1,	%rdi
	movq	%rbx,	%rsi
	movq	$1,	%rdx
	syscall
	popq	%rax
	popq	%rbx
	jmp	next
incrVal:
	movq	8(%rsp),	%rbx
	incb	(%rbx)
	jmp	next
declVal:
	movq	8(%rsp),	%rbx
	decb	(%rbx)
	jmp	next
incrPtr:
	incb	8(%rsp)
	jmp	next
decrPtr:
	decb	8(%rsp)
	jmp	next
begWhile:
	movq	8(%rsp),	%rbx
	movb	(%rbx),	%al
	cmp	$0,	%al
	jz	begWhileSkip
	jmp	begWhileDo
begWhileSkip:
	incb	(%rsp)
	movq	(%rsp),	%rax
	movb	(%rax),	%al
	cmpb	$0,	%al
	jz	done
	cmpb	$'],	%al
	jnz	begWhileSkip
	jmp	next
begWhileDo:
	jmp	next
endWhile:
	movq	8(%rsp),	%rbx
	movb	(%rbx),	%al
	cmp	$0,	%al
	jz	endWhileBreak
	jmp	endWhileContinue
endWhileBreak:
	jmp	next
endWhileContinue:
	movq	$0,	%rbx
endWhileContinue1:	
	decb	(%rsp)
	movq	(%rsp),	%rax
	movb	(%rax),	%al
	cmpb	$0,	%al
	jz	done
	cmpb	$'],	%al
	jz	endWhileContinueNestBeg
	cmpb	$'[,	%al
	jnz	endWhileContinue1
	cmpq	$0,	%rbx
	jnz	endWhileContinueNestEnd
	jmp	next
endWhileContinueNestBeg:
	inc	%rbx
	jmp	endWhileContinue1
endWhileContinueNestEnd:
	dec	%rbx
	jmp	endWhileContinue1