[wasm] Remove support to serialize code stubs.

This removes the support to serialize copies of {CodeStub} codes during
native module serialization. It is still possible to serialize builtins
and all code objects copied from the GC heap are builtins by now.

R=ahaas@chromium.org

Change-Id: If009a82a9d7c7080f70f344040ebb91f20b8cc1a
Reviewed-on: https://chromium-review.googlesource.com/1012081
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52628}

src/wasm/wasm-code-manager.cc

@@ -318,15 +318,13 @@ class NativeModule::CloneCodeHelper {
 
   void SelectForCloning(int32_t code_index);
 
-  void CloneAndPatchCode(bool patch_stub_to_stub_calls);
+  void CloneAndPatchCode();
 
   void PatchTrampolineAndStubCalls(const WasmCode* original_code,
                                    const WasmCode* new_code,
                                    WasmCode::FlushICache flush_icache);
 
  private:
-  void PatchStubToStubCalls();
-
   NativeModule* source_native_module_;
   NativeModule* cloning_native_module_;
   std::vector<uint32_t> selection_;
@@ -344,26 +342,13 @@ NativeModule::CloneCodeHelper::CloneCodeHelper(
     Address new_dest = local->second;
     reverse_lookup_.emplace(old_dest, new_dest);
   }
-
-  for (auto& pair : source_native_module_->stubs_) {
-    Address old_dest = pair.second->instruction_start();
-    auto local = cloning_native_module_->stubs_.find(pair.first);
-    DCHECK(local != cloning_native_module_->stubs_.end());
-    Address new_dest = local->second->instruction_start();
-    reverse_lookup_.emplace(old_dest, new_dest);
-  }
 }
 
 void NativeModule::CloneCodeHelper::SelectForCloning(int32_t code_index) {
   selection_.emplace_back(code_index);
 }
 
-void NativeModule::CloneCodeHelper::CloneAndPatchCode(
-    bool patch_stub_to_stub_calls) {
-  if (patch_stub_to_stub_calls) {
-    PatchStubToStubCalls();
-  }
-
+void NativeModule::CloneCodeHelper::CloneAndPatchCode() {
   WasmCode* anonymous_lazy_builtin = nullptr;
   for (uint32_t index : selection_) {
     const WasmCode* original_code = source_native_module_->GetCode(index);
@@ -400,14 +385,6 @@ void NativeModule::CloneCodeHelper::CloneAndPatchCode(
   }
 }
 
-void NativeModule::CloneCodeHelper::PatchStubToStubCalls() {
-  for (auto& pair : cloning_native_module_->stubs_) {
-    WasmCode* new_stub = pair.second;
-    WasmCode* old_stub = source_native_module_->stubs_.find(pair.first)->second;
-    PatchTrampolineAndStubCalls(old_stub, new_stub, WasmCode::kFlushICache);
-  }
-}
-
 void NativeModule::CloneCodeHelper::PatchTrampolineAndStubCalls(
     const WasmCode* original_code, const WasmCode* new_code,
     WasmCode::FlushICache flush_icache) {
@@ -872,11 +849,6 @@ void NativeModule::CloneTrampolinesAndStubs(
     DCHECK_NE(local, kNullAddress);
     trampolines_.emplace(std::make_pair(key, local));
   }
-  for (auto& pair : other->stubs_) {
-    uint32_t key = pair.first;
-    WasmCode* clone = CloneCode(pair.second, flush_icache);
-    stubs_.emplace(std::make_pair(key, clone));
-  }
 }
 
 WasmCode* NativeModule::CloneCode(const WasmCode* original_code,
@@ -1137,7 +1109,7 @@ std::unique_ptr<NativeModule> NativeModule::Clone() {
   for (uint32_t i = num_imported_functions(), e = FunctionCount(); i < e; ++i) {
     helper.SelectForCloning(i);
   }
-  helper.CloneAndPatchCode(true);
+  helper.CloneAndPatchCode();
 
   return ret;
 }

src/wasm/wasm-code-manager.h

@@ -330,9 +330,6 @@ class V8_EXPORT_PRIVATE NativeModule final {
   // start of the trampoline.
   std::unordered_map<Address, Address, AddressHasher> trampolines_;
 
-  // Maps from stub key to wasm code (containing a copy of that stub).
-  std::unordered_map<uint32_t, WasmCode*> stubs_;
-
   std::unique_ptr<CompilationState, CompilationStateDeleter> compilation_state_;
 
   // A phantom reference to the {WasmCompiledModule}. It is intentionally not

src/wasm/wasm-serialization.cc

@@ -292,8 +292,7 @@ size_t NativeModuleSerializer::DrainBuffer(Vector<byte> dest) {
 }
 
 size_t NativeModuleSerializer::MeasureCopiedStubs() const {
-  size_t ret = sizeof(uint32_t) +  // number of stubs
-               native_module_->stubs_.size() * sizeof(uint32_t);  // stub keys
+  size_t ret = sizeof(uint32_t);  // number of stubs
   for (auto pair : native_module_->trampolines_) {
     v8::internal::Code* code = Code::GetCodeFromTargetAddress(pair.first);
     int builtin_index = code->builtin_index();
@@ -315,14 +314,6 @@ void NativeModuleSerializer::BufferCopiedStubs() {
       static_cast<uint32_t>((buff_size - sizeof(uint32_t)) / sizeof(uint32_t)));
   uint32_t stub_id = kFirstStubId;
 
-  for (auto pair : native_module_->stubs_) {
-    uint32_t key = pair.first;
-    writer.Write(key);
-    stub_lookup_.insert(
-        std::make_pair(pair.second->instruction_start(), stub_id));
-    ++stub_id;
-  }
-
   for (auto pair : native_module_->trampolines_) {
     v8::internal::Code* code = Code::GetCodeFromTargetAddress(pair.first);
     int builtin_index = code->builtin_index();