#include <stdint.h>

|.arch x64
|.actionlist actions
|
| // rbx is the pointer to the current cell
| //   (and it's preserved across calls to functions)
| .define PTR, rbx
|
| // macro for calling a function.
|.macro callp, addr
|  mov64 rax, (uintptr_t)addr
|  call  rax
|.endmacro

#define Dst &state
#define MAX_NESTING 256

void error(const char *msg) {
	fprintf(stderr, "%s\n", msg);
	exit(1);
}

int main(int argc, char *argv[]) {
	if (argc < 2) {
		error("Usage: bf <program>");
	}

	dasm_State *state;
	initjit(&state, actions);

	unsigned int maxpc = 0;
	int pcstack[MAX_NESTING];
	int *top = pcstack, *limit = pcstack + MAX_NESTING;

	// function prologue
	| push PTR
	| mov  PTR, rdi

	for (char *p = argv[1]; *p; p++) {
		switch (*p) {
			case '>':
				| inc PTR
				break;
			case '<':
				| dec PTR
				break;
			case '+':
				| inc byte [PTR]
				break;
			case '-':
				| dec byte [PTR]
				break;
			case '.':
				| movzx edi, byte [PTR]
				| callp putchar
				break;
			case ',':
				| callp getchar
				| mov   byte [PTR], al
				break;
			case '[':
				if (top == limit) {
					error("Nesting too deep.");
				}

				maxpc += 2;
				*top++ = maxpc;
				dasm_growpc(&state, maxpc);
				| cmp byte [PTR], 0
				| je  =>(maxpc-2)
				|=>(maxpc-1):
				break;
			case ']':
				if (top == pcstack) {
					error("Unmatched ']'");
				}

				top--;
				| cmp byte [PTR], 0
				| jne =>(*top-1)
				|=>(*top-2):
				break;
		}
	}

	// function epilogue
	| pop PTR
	| ret

	void (*bf_program)(char*) = jitcode(&state);
	char *mem = calloc(30000, 1);
	bf_program(mem);
	free(mem);
	free_jitcode(bf_program);
	return 0;
}