blink_gc_plugin: Handle TraceIfNeeded for resolved T

TraceIfNeeded with a template T is already handled properly,
but TraceIfNeeded with a resolved T, like TraceIfNeeded<Member<Node>>
was not treated as a traced field.

Bug: 1044898
Change-Id: I9f394290d7cc3ec8ad8d7b1c0489b7044b757513
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2032751Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Keishi Hattori <keishi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737674}

tools/clang/blink_gc_plugin/CheckTraceVisitor.cpp

@@ -43,6 +43,11 @@ bool CheckTraceVisitor::VisitCallExpr(CallExpr* call) {
     return true;
   }
 
+  if (ImplicitCastExpr* expr = dyn_cast<ImplicitCastExpr>(callee)) {
+    if (CheckImplicitCastExpr(call, expr))
+      return true;
+  }
+
   // A tracing call will have either a |visitor| or a |m_field| argument.
   // A registerWeakMembers call will have a |this| argument.
   if (call->getNumArgs() != 1)
@@ -70,7 +75,6 @@ bool CheckTraceVisitor::VisitCallExpr(CallExpr* call) {
   if (CXXMemberCallExpr* expr = dyn_cast<CXXMemberCallExpr>(call)) {
     if (CheckTraceFieldMemberCall(expr) || CheckRegisterWeakMembers(expr))
       return true;
-
   }
 
   CheckTraceBaseCall(call);
@@ -164,7 +168,8 @@ void CheckTraceVisitor::CheckCXXDependentScopeMemberExpr(
     }
   }
 
-  // Check for TraceIfNeeded<T>::trace(visitor, &field)
+  // Check for TraceIfNeeded<T>::trace(visitor, &field) where T cannot be
+  // resolved
   if (call->getNumArgs() == 2 && fn_name == kTraceName &&
       tmpl->getName() == kTraceIfNeededName) {
     FindFieldVisitor finder;
@@ -370,3 +375,28 @@ void CheckTraceVisitor::MarkAllWeakMembersTraced() {
       field.second.MarkTraced();
   }
 }
+
+bool CheckTraceVisitor::CheckImplicitCastExpr(CallExpr* call,
+                                              ImplicitCastExpr* expr) {
+  DeclRefExpr* sub_expr = dyn_cast<DeclRefExpr>(expr->getSubExpr());
+  if (!sub_expr)
+    return false;
+  NestedNameSpecifier* qualifier = sub_expr->getQualifier();
+  if (!qualifier)
+    return false;
+  CXXRecordDecl* class_decl = qualifier->getAsRecordDecl();
+  if (!class_decl)
+    return false;
+  NamedDecl* found_decl = sub_expr->getFoundDecl();
+  std::string fn_name = found_decl->getNameAsString();
+  // Check for TraceIfNeeded<T>::trace(visitor, &field) where T can be resolved
+  if (call->getNumArgs() == 2 && fn_name == kTraceName &&
+      class_decl->getName() == kTraceIfNeededName) {
+    FindFieldVisitor finder;
+    finder.TraverseStmt(call->getArg(1));
+    if (finder.field())
+      FoundField(finder.field());
+    return true;
+  }
+  return false;
+}

tools/clang/blink_gc_plugin/CheckTraceVisitor.h

@@ -41,6 +41,8 @@ class CheckTraceVisitor : public clang::RecursiveASTVisitor<CheckTraceVisitor> {
                            clang::CXXRecordDecl* callee,
                            clang::Expr* arg);
   bool CheckRegisterWeakMembers(clang::CXXMemberCallExpr* call);
+  bool CheckImplicitCastExpr(clang::CallExpr* call,
+                             clang::ImplicitCastExpr* expr);
 
   bool IsWeakCallback() const;
 

tools/clang/blink_gc_plugin/tests/heap/stubs.h

@@ -305,7 +305,7 @@ public:
 
 template<typename T>
 struct TraceIfNeeded {
-    static void Trace(Visitor*, T*);
+  static void Trace(Visitor*, T&);
 };
 
 }

tools/clang/blink_gc_plugin/tests/trace_if_needed_resolved.cpp

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "trace_if_needed_resolved.h"
+
+namespace blink {
+
+void HeapObject::Trace(Visitor* visitor) {
+  // Using TraceIfNeeded with a non-template type should count as tracing a
+  // field.
+  TraceIfNeeded<Member<HeapObject>>::Trace(visitor, m_one);
+  TraceIfNeeded<int>::Trace(visitor, m_two);
+}
+
+}  // namespace blink

tools/clang/blink_gc_plugin/tests/trace_if_needed_resolved.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TRACE_IF_NEEDED_RESOLVED_H_
+#define TRACE_IF_NEEDED_RESOLVED_H_
+
+#include "heap/stubs.h"
+
+namespace blink {
+
+class HeapObject : public GarbageCollected<HeapObject> {
+ public:
+  virtual void Trace(Visitor*);
+
+ private:
+  Member<HeapObject> m_one;
+  int m_two;
+};
+
+}  // namespace blink
+
+#endif

tools/clang/pylib/clang/plugin_testing.py

@@ -68,6 +68,7 @@ class ClangPluginTest(object):
         pass
       cmd.append(test)
 
+      print("cmd", cmd)
       failure_message = self.RunOneTest(test_name, cmd)
       if failure_message:
         print('failed: %s' % failure_message)