[compiler] Merge revisit loop into visit loop in SimplifiedLowering

This CL makes it so that we revisit nodes in the revisit queue as soon
as possible in RETYPE and PROPAGATE. This is done to revisit loops
related to backedges before moving onto other nodes.

Bug: v8:10424
Change-Id: I432c6551805903072b3f9fbc867adca82b263325
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2157373Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68149}

src/compiler/simplified-lowering.cc

@@ -336,30 +336,32 @@ class RepresentationSelector {
             revisit_queue_.push(user);
           }
         }
-      }
-    }
 
-    // Process the revisit queue.
-    while (!revisit_queue_.empty()) {
-      Node* node = revisit_queue_.front();
-      revisit_queue_.pop();
-      NodeInfo* info = GetInfo(node);
-      info->set_visited();
-      bool updated = UpdateFeedbackType(node);
-      TRACE(" revisit #%d: %s\n", node->id(), node->op()->mnemonic());
-      VisitNode<RETYPE>(node, info->truncation(), nullptr);
-      TRACE("  ==> output ");
-      PrintOutputInfo(info);
-      TRACE("\n");
-      if (updated) {
-        // Here we need to check all uses since we can't easily know which
-        // nodes will need to be revisited due to having an input which was
-        // a revisited node.
-        for (Node* const user : node->uses()) {
-          if (GetInfo(user)->visited()) {
-            TRACE(" QUEUEING #%d: %s\n", user->id(), user->op()->mnemonic());
-            GetInfo(user)->set_queued();
-            revisit_queue_.push(user);
+        // Process the revisit queue.
+        while (!revisit_queue_.empty()) {
+          Node* revisit_node = revisit_queue_.front();
+          revisit_queue_.pop();
+          NodeInfo* revisit_info = GetInfo(revisit_node);
+          revisit_info->set_visited();
+          bool updated = UpdateFeedbackType(revisit_node);
+          TRACE(" revisit #%d: %s\n", revisit_node->id(),
+                revisit_node->op()->mnemonic());
+          VisitNode<RETYPE>(revisit_node, revisit_info->truncation(), nullptr);
+          TRACE("  ==> output ");
+          PrintOutputInfo(revisit_info);
+          TRACE("\n");
+          if (updated) {
+            // Here we need to check all uses since we can't easily know which
+            // nodes will need to be revisited due to having an input which was
+            // a revisited node.
+            for (Node* const user : revisit_node->uses()) {
+              if (GetInfo(user)->visited()) {
+                TRACE(" QUEUEING #%d: %s\n", user->id(),
+                      user->op()->mnemonic());
+                GetInfo(user)->set_queued();
+                revisit_queue_.push(user);
+              }
+            }
           }
         }
       }
@@ -599,17 +601,18 @@ class RepresentationSelector {
       TRACE(" visit #%d: %s (trunc: %s)\n", node->id(), node->op()->mnemonic(),
             info->truncation().description());
       VisitNode<PROPAGATE>(node, info->truncation(), nullptr);
-    }
 
-    // Revisit queue
-    while (!revisit_queue_.empty()) {
-      Node* node = revisit_queue_.front();
-      NodeInfo* info = GetInfo(node);
-      revisit_queue_.pop();
-      info->set_visited();
-      TRACE(" visit #%d: %s (trunc: %s)\n", node->id(), node->op()->mnemonic(),
-            info->truncation().description());
-      VisitNode<PROPAGATE>(node, info->truncation(), nullptr);
+      // Revisit queue
+      while (!revisit_queue_.empty()) {
+        Node* revisit_node = revisit_queue_.front();
+        NodeInfo* revisit_info = GetInfo(revisit_node);
+        revisit_queue_.pop();
+        revisit_info->set_visited();
+        TRACE(" visit #%d: %s (trunc: %s)\n", revisit_node->id(),
+              revisit_node->op()->mnemonic(),
+              revisit_info->truncation().description());
+        VisitNode<PROPAGATE>(revisit_node, revisit_info->truncation(), nullptr);
+      }
     }
   }