[serializer] allow duplicate API external references.

Due to link-time optimizations functions with same code
can be folded into one, resulting in duplicate references.

R=jochen@chromium.org, peria@chromium.org
BUG=chromium:617892

Review-Url: https://codereview.chromium.org/2707903002
Cr-Commit-Position: refs/heads/master@{#43317}

src/external-reference-table.cc

@@ -443,6 +443,7 @@ void ExternalReferenceTable::AddDeoptEntries(Isolate* isolate) {
 void ExternalReferenceTable::AddApiReferences(Isolate* isolate) {
   // Add external references provided by the embedder (a null-terminated
   // array).
+  api_refs_start_ = size();
   intptr_t* api_external_references = isolate->api_external_references();
   if (api_external_references != nullptr) {
     while (*api_external_references != 0) {

src/external-reference-table.h

@@ -22,6 +22,7 @@ class ExternalReferenceTable {
   uint32_t size() const { return static_cast<uint32_t>(refs_.length()); }
   Address address(uint32_t i) { return refs_[i].address; }
   const char* name(uint32_t i) { return refs_[i].name; }
+  bool is_api_reference(uint32_t i) { return i >= api_refs_start_; }
 
 #ifdef DEBUG
   void increment_count(uint32_t i) { refs_[i].count++; }
@@ -64,6 +65,7 @@ class ExternalReferenceTable {
   void AddApiReferences(Isolate* isolate);
 
   List<ExternalReferenceEntry> refs_;
+  uint32_t api_refs_start_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalReferenceTable);
 };

src/snapshot/serializer-common.cc

@@ -21,6 +21,8 @@ ExternalReferenceEncoder::ExternalReferenceEncoder(Isolate* isolate) {
   ExternalReferenceTable* table = ExternalReferenceTable::instance(isolate);
   for (uint32_t i = 0; i < table->size(); ++i) {
     Address addr = table->address(i);
+    // Ignore duplicate API references.
+    if (table->is_api_reference(i) && !map_->Get(addr).IsNothing()) continue;
     DCHECK(map_->Get(addr).IsNothing());
     map_->Set(addr, i);
     DCHECK(map_->Get(addr).IsJust());

test/cctest/test-serialize.cc

@@ -1986,6 +1986,7 @@ intptr_t original_external_references[] = {
     reinterpret_cast<intptr_t>(&NamedPropertyGetterForSerialization),
     reinterpret_cast<intptr_t>(&AccessorForSerialization),
     reinterpret_cast<intptr_t>(&SerializedExtension::FunctionCallback),
+    reinterpret_cast<intptr_t>(&serialized_static_field),  // duplicate entry
     0};
 
 intptr_t replaced_external_references[] = {
@@ -1994,6 +1995,7 @@ intptr_t replaced_external_references[] = {
     reinterpret_cast<intptr_t>(&NamedPropertyGetterForSerialization),
     reinterpret_cast<intptr_t>(&AccessorForSerialization),
     reinterpret_cast<intptr_t>(&SerializedExtension::FunctionCallback),
+    reinterpret_cast<intptr_t>(&serialized_static_field),
     0};
 
 TEST(SnapshotCreatorExternalReferences) {