A BF interpreter in C with some dumb optimisations

bf.c

//Compile with: gcc bf.c -o bf -O3 && ./bf mandelbrot.bf
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int opCount(char** pt, char v) {
	int opCount = 0;
	char* p = *pt;
	while (*(*pt) == v) {
		opCount++;
		(*pt)++;
	}
	(*pt)--;
	return opCount;
}

int main(int argc, char* argv[]) {
	if (argc < 2) {
		printf("Usage: bf <filename>\n");
		return -1;
	}

	FILE* f = fopen(argv[1], "rb");
	if (!f) {
		printf("Failed to open file\n");
		return -1;
	}

	fseek(f, 0, SEEK_END);
	int len = ftell(f);
	rewind(f);
	char* program = malloc(sizeof(char)*len);
	fread(program, 1, len, f);
	fclose(f);

	char* stack[256] = {0};
	register int stackidx = 0;
	char state[100000] = {0};
	char* ptr = state;

	for (char* p = program; *p; p++) {
		//printf("%c %d %d\n", *p, (int)p - (int)program, (int)ptr - (int)state);
		//getchar();
		switch (*p) {
			case '>': 
				ptr += opCount(&p, '>'); 
				break;
			case '<': 
				ptr -= opCount(&p, '<'); 
				break;
			case '+': 
				*ptr += opCount(&p, '+');
				break;
			case '-': 
				*ptr -= opCount(&p, '-');
				break;
			case '.': 
				putchar(*ptr); 
				break;
			case ',': 
				*ptr = getchar(); 
				break;
			case '[': 
				if ((int)*ptr == 0) {
					int bal = 0;
					do {
						if (*p == '[') bal++;
						if (*p == ']') bal--;
						p++;
					} while(bal != 0);
					p--;
				} else {
					stack[stackidx] = p;
					stackidx++;
				}
				break;
			case ']':
				if ((int)*ptr != 0) {
					p = stack[stackidx-1];
				}
				else {
					stackidx--;
				}
				break;
		}
	}

	free(program);

	return 0;
}