zend_cfg: use uint32_t type rather than int type

[Girgias]

These are count values and thus should never be negative, more over their use site usually wants them to be uint32_t too. Aligning these types makes the intention clearer.

I have also trying to propagate those changes to use sites of these struct members.

[Girgias]

I feel that there should be a better way to solve this but when I initially did:

Suggested change

	int backtracking_block_num = block_num;
	do {
	block_num--;
	} while (block_num >= 0
	backtracking_block_num--;
	} while (backtracking_block_num >= 0
	&& !(ssa->cfg.blocks[block_num].flags & ZEND_BB_REACHABLE));
	if (block_num >= 0) {
	if (backtracking_block_num >= 0) {
	continue;
	do {
	block_num--;
	} while (block_num > 0
	&& !(ssa->cfg.blocks[block_num].flags & ZEND_BB_REACHABLE));
	if (!(ssa->cfg.blocks[block_num].flags & ZEND_BB_REACHABLE)) {
	continue;

it didn't behave as expected, so I guess I'm not fully grasping what is happening here.

[arnaud-lb]

I think that you had inverted the logic in if (!(ssa->cfg.blocks[block_num].flags & ZEND_BB_REACHABLE)) {. Before, if (block_num >= 0) implied that ssa->cfg.blocks[block_num] was reachable. So it should be if ((ssa->cfg.blocks[block_num].flags & ZEND_BB_REACHABLE)) {.

But I find the original logic easier to follow.

[Girgias]

Happy to keep the original logic, although I might add a comment explaining what is happening :)

[arnaud-lb]

Did a partial review up to dfa_pass.c

[Girgias]

Needed to force-push after a rebase due to conflicts arising after the merge of #21540, but follow-up commits address the review comments. :)