Revert "chore: bring back recursive processing of effects" (#12880)

* Revert "chore: bring back recursive processing of effects (#12861)"

This reverts commit cb124315be.

* apply tweak

packages/svelte/src/internal/client/runtime.js

@@ -571,53 +571,6 @@ export function schedule_effect(signal) {
 	current_queued_root_effects.push(effect);
 }
 
-/**
- * @param {Effect} effect
- * @param {Effect[]} effects
- */
-function process_effect_children(effect, effects) {
-	var current = effect.first;
-
-	while (current !== null) {
-		var next = current.next;
-		process_effect(current, effects);
-		current = next;
-	}
-}
-
-/**
- * @param {Effect} effect
- * @param {Effect[]} effects
- */
-function process_effect(effect, effects) {
-	var flags = effect.f;
-	// TODO: we probably don't need to check for destroyed as it shouldn't be encountered?
-	var is_active = (flags & (DESTROYED | INERT)) === 0;
-	var is_branch = (flags & BRANCH_EFFECT) !== 0;
-	var is_clean = (flags & CLEAN) !== 0;
-
-	// Skip this branch if it's clean
-	if (is_active && (!is_branch || !is_clean)) {
-		if (is_branch) {
-			set_signal_status(effect, CLEAN);
-		}
-
-		if ((flags & RENDER_EFFECT) !== 0) {
-			if (!is_branch && check_dirtiness(effect)) {
-				update_effect(effect);
-			}
-
-			process_effect_children(effect, effects);
-		} else if ((flags & EFFECT) !== 0) {
-			if (is_branch || is_clean) {
-				process_effect_children(effect, effects);
-			} else {
-				effects.push(effect);
-			}
-		}
-	}
-}
-
 /**
  *
  * This function both runs render effects and collects user effects in topological order
@@ -630,13 +583,70 @@ function process_effect(effect, effects) {
  * @returns {void}
  */
 function process_effects(effect, collected_effects) {
-	/** @type {Effect[]} */
+	var current_effect = effect.first;
 	var effects = [];
-	process_effect_children(effect, effects);
+
+	main_loop: while (current_effect !== null) {
+		var flags = current_effect.f;
+		// TODO: we probably don't need to check for destroyed as it shouldn't be encountered?
+		var is_active = (flags & (DESTROYED | INERT)) === 0;
+		var is_branch = (flags & BRANCH_EFFECT) !== 0;
+		var is_clean = (flags & CLEAN) !== 0;
+		var child = current_effect.first;
+
+		// Skip this branch if it's clean
+		if (is_active && (!is_branch || !is_clean)) {
+			if (is_branch) {
+				set_signal_status(current_effect, CLEAN);
+			}
+
+			if ((flags & RENDER_EFFECT) !== 0) {
+				if (!is_branch && check_dirtiness(current_effect)) {
+					update_effect(current_effect);
+					// Child might have been mutated since running the effect
+					child = current_effect.first;
+				}
+
+				if (child !== null) {
+					current_effect = child;
+					continue;
+				}
+			} else if ((flags & EFFECT) !== 0) {
+				if (is_branch || is_clean) {
+					if (child !== null) {
+						current_effect = child;
+						continue;
+					}
+				} else {
+					effects.push(current_effect);
+				}
+			}
+		}
+		var sibling = current_effect.next;
+
+		if (sibling === null) {
+			let parent = current_effect.parent;
+
+			while (parent !== null) {
+				if (effect === parent) {
+					break main_loop;
+				}
+				var parent_sibling = parent.next;
+				if (parent_sibling !== null) {
+					current_effect = parent_sibling;
+					continue main_loop;
+				}
+				parent = parent.parent;
+			}
+		}
+
+		current_effect = sibling;
+	}
+
 	// We might be dealing with many effects here, far more than can be spread into
 	// an array push call (callstack overflow). So let's deal with each effect in a loop.
 	for (var i = 0; i < effects.length; i++) {
-		var child = effects[i];
+		child = effects[i];
 		collected_effects.push(child);
 		process_effects(child, collected_effects);
 	}