Use loop bound canon to forkify demosaic

• Use loop bound canon to forkify demosaic.

hercules_opt/src/gcm.rs

@@ -486,11 +486,10 @@ fn basic_blocks(
         // Look between the LCA and the schedule early location to place the
         // node.
         let schedule_early = schedule_early[id.idx()].unwrap();
+        // If the node has no users, then it doesn't really matter where we
+        // place it - just place it at the early placement.
         let schedule_late = lca.unwrap_or(schedule_early);
-        let mut chain = dom
-            // If the node has no users, then it doesn't really matter where we
-            // place it - just place it at the early placement.
-            .chain(schedule_late, schedule_early);
+        let mut chain = dom.chain(schedule_late, schedule_early);
 
         if let Some(mut location) = chain.next() {
             while let Some(control_node) = chain.next() {