[node] OwnedBy fix for only one owner check

In the case of having:
 * NodeA(...)
 * NodeB(NodeA, NodeA), with this being the only use of NodeA.
this CL gives A's ownership to B.

Before, we used to say that B didn't have ownership of A due to A having
two uses.

This brings it in line with OwnedBy with two owners check:
https://source.chromium.org/chromium/_/chromium/v8/v8.git/+/abd1a0fc04476bbb27ef2dfda2e444cc1467f5f6:src/compiler/node.cc;l=291

Change-Id: I15fdf373136a21bf423e6dffd9588054fd720d72
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2007502Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65867}

src/compiler/node.cc

@@ -287,6 +287,17 @@ void Node::ReplaceUses(Node* that) {
   first_use_ = nullptr;
 }
 
+bool Node::OwnedBy(Node const* owner) const {
+  unsigned mask = 0;
+  for (Use* use = first_use_; use; use = use->next) {
+    if (use->from() == owner) {
+      mask |= 1;
+    } else {
+      return false;
+    }
+  }
+  return mask == 1;
+}
 
 bool Node::OwnedBy(Node const* owner1, Node const* owner2) const {
   unsigned mask = 0;

src/compiler/node.h

@@ -139,9 +139,7 @@ class V8_EXPORT_PRIVATE Node final {
   Uses uses() { return Uses(this); }
 
   // Returns true if {owner} is the only user of {this} node.
-  bool OwnedBy(Node* owner) const {
-    return first_use_ && first_use_->from() == owner && !first_use_->next;
-  }
+  bool OwnedBy(Node const* owner) const;
 
   // Returns true if {owner1} and {owner2} are the only users of {this} node.
   bool OwnedBy(Node const* owner1, Node const* owner2) const;

test/cctest/compiler/test-node.cc

@@ -42,8 +42,22 @@ void CheckUseChain(Node* node, Node** uses, int use_count) {
   // Check ownership.
   if (use_count == 1) CHECK(node->OwnedBy(uses[0]));
   if (use_count > 1) {
+    Node* first_use = uses[0];
+    bool different_uses = false;
     for (int i = 0; i < use_count; i++) {
-      CHECK(!node->OwnedBy(uses[i]));
+      if (uses[i] != first_use) {
+        different_uses = true;
+        break;
+      }
+    }
+    if (different_uses) {
+      // If there are different uses, check that node is not owned by any use.
+      for (int i = 0; i < use_count; i++) {
+        CHECK(!node->OwnedBy(uses[i]));
+      }
+    } else {
+      // If all uses are the same, check that node is owned by that use.
+      CHECK(node->OwnedBy(first_use));
     }
   }