bf.c

#include <stdio.h>

static const char bf[] = ">++[<+++++++++++++>-]<[[>+>+<<-]>[<+>-]++++++++"
                         "[>++++++++<-]>.[-]<<>++++++++++[>++++++++++[>++"
                         "++++++++[>++++++++++[>++++++++++[>++++++++++[>+"
                         "+++++++++[-]<-]<-]<-]<-]<-]<-]<-]++++++++++.";

static void tputs(const char *str)
{
	putchar('\t');
	puts(str);
}

int main(void)
{
	size_t i, len = sizeof(bf) - 1;
	int stack[512];
	int labels = 0, sp = 0;

	puts("default rel");
	puts("global main");
	puts("extern printf");
	puts("section .text");
	puts("main:");
	tputs("sub rsp, 4096");
	tputs("mov rdi, rsp");
	tputs("mov rcx, 4096");
	tputs("xor rax, rax");
	tputs("rep stosb");
	tputs("mov rdi, rsp");

	for(i = 0; i < len; i++)
	{
		int n;

		switch(bf[i])
		{
			case '<':
				tputs("dec rdi");
			break;
			case '>':
				tputs("inc rdi");
			break;
			case '+':
				n = 0;
				while(bf[i++] == '+')
				{
					n++;
				}
				i -= 2;
				if(n == 1) tputs("inc byte [rdi]");
				else printf("\tadd byte [rdi], %d\n", n);
			break;
			case '-':
				tputs("dec byte [rdi]");
			break;
			case '.':
				tputs("call put");
			break;
			case ',':
				tputs("call get");
			break;
			case '[':
				if(bf[i+1] == '-' && bf[i+2] == ']')
				{
					i += 2;
					tputs("mov byte [rdi], 0");
					break;
				}
				stack[sp++] = labels;
				printf("L%d:\n", labels++);
			break;
			case ']':
				tputs("movzx rax, byte [rdi]");
				tputs("test rax, rax");
				printf("\tjnz L%d\n", stack[--sp]);
			break;
		}
	}

	tputs("mov rax, 60");
	tputs("syscall");
	puts("put:");
	tputs("push rdi");
	tputs("xor rax, rax");
	tputs("movzx rsi, byte [rdi]");
	tputs("lea rdi, [fmt]");
	tputs("call printf wrt ..plt");
	tputs("pop rdi");
	tputs("ret");

	puts("get:");
	tputs("ret");

	puts("section .rodata");
	tputs("fmt db \"%c\", 0");
}