[Interpreter] Avoid allocating pairs array in VisitDeclarations.

src/interpreter/bytecode-generator.cc

 // Copyright 2015 the V8 project 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 "src/interpreter/bytecode-generator.h"
 
 #include "src/ast/scopes.h"
 #include "src/code-stubs.h"
 #include "src/compiler.h"
 #include "src/interpreter/bytecode-flags.h"
@@ skipping 514 matching lines @@
     if (generator()->HasStackOverflow() && !result_identified()) {
       SetResultInAccumulator();
     }
     return result_register_;
   }
 
  private:
   Register result_register_;
 };
 
+// Used to build a list of global declaration initial value pairs.
+class BytecodeGenerator::GlobalDeclarationsBuilder final : public ZoneObject {
+ public:
+  GlobalDeclarationsBuilder(Isolate* isolate, Zone* zone)
+      : isolate_(isolate),
+        declaration_pairs_(0, zone),
+        constant_pool_entry_(0),
+        has_constant_pool_entry_(false) {}
+
+  void AddDeclaration(FeedbackVectorSlot slot, Handle<Object> initial_value) {
+    DCHECK(!slot.IsInvalid());
+    declaration_pairs_.push_back(handle(Smi::FromInt(slot.ToInt()), isolate_));
+    declaration_pairs_.push_back(initial_value);
+  }
+
+  Handle<FixedArray> AllocateDeclarationPairs() {
+    DCHECK(has_constant_pool_entry_);
+    int array_index = 0;
+    Handle<FixedArray> data = isolate_->factory()->NewFixedArray(
+        static_cast<int>(declaration_pairs_.size()), TENURED);
+    for (Handle<Object> obj : declaration_pairs_) {
+      data->set(array_index++, *obj);
+    }
+    return data;
+  }
+
+  size_t constant_pool_entry() {
+    DCHECK(has_constant_pool_entry_);
+    return constant_pool_entry_;
+  }
+
+  void set_constant_pool_entry(size_t constant_pool_entry) {
+    DCHECK(!empty());
+    DCHECK(!has_constant_pool_entry_);
+    constant_pool_entry_ = constant_pool_entry;
+    has_constant_pool_entry_ = true;
+  }
+
+  bool empty() { return declaration_pairs_.empty(); }
+
+ private:
+  Isolate* isolate_;
+  ZoneVector<Handle<Object>> declaration_pairs_;
+  size_t constant_pool_entry_;
+  bool has_constant_pool_entry_;
+};
+
 BytecodeGenerator::BytecodeGenerator(CompilationInfo* info)
     : isolate_(info->isolate()),
       zone_(info->zone()),
       builder_(new (zone()) BytecodeArrayBuilder(
           info->isolate(), info->zone(), info->num_parameters_including_this(),
           info->scope()->MaxNestedContextChainLength(),
           info->scope()->num_stack_slots(), info->literal(),
           info->SourcePositionRecordingMode())),
       info_(info),
       scope_(info->scope()),
-      globals_(0, info->zone()),
+      globals_builder_(new (zone()) GlobalDeclarationsBuilder(info->isolate(),
+                                                              info->zone())),
+      global_declarations_(0, info->zone()),
       execution_control_(nullptr),
       execution_context_(nullptr),
       execution_result_(nullptr),
       register_allocator_(nullptr),
       generator_resume_points_(info->literal()->yield_count(), info->zone()),
       generator_state_() {
   InitializeAstVisitor(isolate()->stack_guard()->real_climit());
 }
 
 Handle<BytecodeArray> BytecodeGenerator::MakeBytecode() {
+  GenerateBytecode();
+
+  // Build global declaration pair arrays.
+  for (GlobalDeclarationsBuilder* globals_builder : global_declarations_) {
+    Handle<FixedArray> declarations =
+        globals_builder->AllocateDeclarationPairs();
+    builder()->InsertReservedConstantPoolEntry(
+        globals_builder->constant_pool_entry(), declarations);
+  }
+
+  return builder()->ToBytecodeArray();
+}
+
+void BytecodeGenerator::GenerateBytecode() {
   // Initialize the incoming context.
   ContextScope incoming_context(this, scope(), false);
 
   // Initialize control scope.
   ControlScopeForTopLevel control(this);
 
   RegisterAllocationScope register_scope(this);
 
   if (IsResumableFunction(info()->literal()->kind())) {
     generator_state_ = register_allocator()->NewRegister();
     VisitGeneratorPrologue();
   }
 
   // Build function context only if there are context allocated variables.
   if (scope()->NeedsContext()) {
     // Push a new inner context scope for the function.
     VisitNewLocalFunctionContext();
     ContextScope local_function_context(this, scope(), false);
     VisitBuildLocalActivationContext();
-    MakeBytecodeBody();
+    GenerateBytecodeBody();
   } else {
-    MakeBytecodeBody();
+    GenerateBytecodeBody();
   }
 
   // In generator functions, we may not have visited every yield in the AST
   // since we skip some obviously dead code. Hence the generated bytecode may
   // contain jumps to unbound labels (resume points that will never be used).
   // We bind these now.
   for (auto& label : generator_resume_points_) {
     if (!label.is_bound()) builder()->Bind(&label);
   }
 
   builder()->EnsureReturn();
-  return builder()->ToBytecodeArray();
 }
 
-void BytecodeGenerator::MakeBytecodeBody() {
+void BytecodeGenerator::GenerateBytecodeBody() {
   // Build the arguments object if it is used.
   VisitArgumentsObject(scope()->arguments());
 
   // Build rest arguments array if it is used.
   int rest_index;
   Variable* rest_parameter = scope()->rest_parameter(&rest_index);
   VisitRestArgumentsArray(rest_parameter);
 
   // Build assignment to {.this_function} variable if it is used.
   VisitThisFunctionVariable(scope()->this_function_var());
@@ skipping 113 matching lines @@
   Variable* variable = decl->proxy()->var();
   VariableMode mode = decl->mode();
   // Const and let variables are initialized with the hole so that we can
   // check that they are only assigned once.
   bool hole_init = mode == CONST || mode == LET;
   switch (variable->location()) {
     case VariableLocation::GLOBAL:
     case VariableLocation::UNALLOCATED: {
       DCHECK(!variable->binding_needs_init());
       FeedbackVectorSlot slot = decl->proxy()->VariableFeedbackSlot();
-      DCHECK(!slot.IsInvalid());
-      globals()->push_back(handle(Smi::FromInt(slot.ToInt()), isolate()));
-      globals()->push_back(isolate()->factory()->undefined_value());
+      globals_builder()->AddDeclaration(
+          slot, isolate()->factory()->undefined_value());
       break;
     }
     case VariableLocation::LOCAL:
       if (hole_init) {
         Register destination(variable->index());
         builder()->LoadTheHole().StoreAccumulatorInRegister(destination);
       }
       break;
     case VariableLocation::PARAMETER:
       if (hole_init) {
@@ skipping 27 matching lines @@
 void BytecodeGenerator::VisitFunctionDeclaration(FunctionDeclaration* decl) {
   Variable* variable = decl->proxy()->var();
   switch (variable->location()) {
     case VariableLocation::GLOBAL:
     case VariableLocation::UNALLOCATED: {
       Handle<SharedFunctionInfo> function = Compiler::GetSharedFunctionInfo(
           decl->fun(), info()->script(), info());
       // Check for stack-overflow exception.
       if (function.is_null()) return SetStackOverflow();
       FeedbackVectorSlot slot = decl->proxy()->VariableFeedbackSlot();
-      DCHECK(!slot.IsInvalid());
-      globals()->push_back(handle(Smi::FromInt(slot.ToInt()), isolate()));
-      globals()->push_back(function);
+      globals_builder()->AddDeclaration(slot, function);
       break;
     }
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL: {
       VisitForAccumulatorValue(decl->fun());
       DCHECK(variable->mode() == LET || variable->mode() == VAR ||
              variable->mode() == CONST);
       VisitVariableAssignment(variable, Token::INIT,
                               FeedbackVectorSlot::Invalid());
       break;
@@ skipping 14 matching lines @@
       VisitForAccumulatorValue(decl->fun());
       builder()->StoreAccumulatorInRegister(literal).CallRuntime(
           Runtime::kDeclareEvalFunction, name, 2);
     }
   }
 }
 
 void BytecodeGenerator::VisitDeclarations(
     ZoneList<Declaration*>* declarations) {
   RegisterAllocationScope register_scope(this);
-  DCHECK(globals()->empty());
+  DCHECK(globals_builder()->empty());
   for (int i = 0; i < declarations->length(); i++) {
     RegisterAllocationScope register_scope(this);
     Visit(declarations->at(i));
   }
-  if (globals()->empty()) return;
-  int array_index = 0;
-  Handle<FixedArray> data = isolate()->factory()->NewFixedArray(
-      static_cast<int>(globals()->size()), TENURED);
-  for (Handle<Object> obj : *globals()) data->set(array_index++, *obj);
+  if (globals_builder()->empty()) return;
+
+  globals_builder()->set_constant_pool_entry(
+      builder()->ReserveConstantPoolEntry());
   int encoded_flags = info()->GetDeclareGlobalsFlags();
 
   register_allocator()->PrepareForConsecutiveAllocations(3);
 
   Register pairs = register_allocator()->NextConsecutiveRegister();
-  builder()->LoadLiteral(data);
-  builder()->StoreAccumulatorInRegister(pairs);
+  Register flags = register_allocator()->NextConsecutiveRegister();
+  Register function = register_allocator()->NextConsecutiveRegister();
 
-  Register flags = register_allocator()->NextConsecutiveRegister();
-  builder()->LoadLiteral(Smi::FromInt(encoded_flags));
-  builder()->StoreAccumulatorInRegister(flags);
-  DCHECK(flags.index() == pairs.index() + 1);
+  // Emit code to declare globals.
+  builder()
+      ->LoadConstantPoolEntry(globals_builder()->constant_pool_entry())
+      .StoreAccumulatorInRegister(pairs)
+      .LoadLiteral(Smi::FromInt(encoded_flags))
+      .StoreAccumulatorInRegister(flags)
+      .MoveRegister(Register::function_closure(), function)
+      .CallRuntime(Runtime::kDeclareGlobalsForInterpreter, pairs, 3);
 
-  Register function = register_allocator()->NextConsecutiveRegister();
-  builder()->MoveRegister(Register::function_closure(), function);
-
-  builder()->CallRuntime(Runtime::kDeclareGlobalsForInterpreter, pairs, 3);
-  globals()->clear();
+  // Push and reset globals builder.
+  global_declarations_.push_back(globals_builder());
+  globals_builder_ = new (zone()) GlobalDeclarationsBuilder(isolate(), zone());
 }
 
 void BytecodeGenerator::VisitStatements(ZoneList<Statement*>* statements) {
   for (int i = 0; i < statements->length(); i++) {
     // Allocate an outer register allocations scope for the statement.
     RegisterAllocationScope allocation_scope(this);
     Statement* stmt = statements->at(i);
     Visit(stmt);
     if (stmt->IsJump()) break;
   }
@@ skipping 2329 matching lines @@
   return execution_context()->scope()->language_mode();
 }
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return TypeFeedbackVector::GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8