[Interpreter] Reduce temporary register usage in generated bytecode.

src/interpreter/bytecode-array-builder.h

Index: src/interpreter/bytecode-array-builder.h
diff --git a/src/interpreter/bytecode-array-builder.h b/src/interpreter/bytecode-array-builder.h
index 27262e224d0ba606cf9fc26881470ab9fde2f824..3f2415e1be7a97e2f4d77c90071f9f6c847e6764 100644
--- a/src/interpreter/bytecode-array-builder.h
+++ b/src/interpreter/bytecode-array-builder.h
@@ -28,14 +28,14 @@ class BytecodeArrayBuilder {
   BytecodeArrayBuilder(Isolate* isolate, Zone* zone);
   Handle<BytecodeArray> ToBytecodeArray();
 
-  // Set number of parameters expected by function.
+  // Set the number of parameters expected by function.
   void set_parameter_count(int number_of_params);
   int parameter_count() const {
     DCHECK_GE(parameter_count_, 0);
     return parameter_count_;
   }
 
-  // Set number of locals required for bytecode array.
+  // Set the number of locals required for bytecode array.
   void set_locals_count(int number_of_locals);
   int locals_count() const {
     DCHECK_GE(local_register_count_, 0);
@@ -57,7 +57,14 @@ class BytecodeArrayBuilder {
 
   Register Parameter(int parameter_index) const;
 
-  // Constant loads to the accumulator.
+  // Return true if the register |reg| represents a parameter or a
+  // local.
+  bool RegisterIsParameterOrLocal(Register reg) const;
+
+  // Return true if the register |reg| represents a temporary register.
+  bool RegisterIsTemporary(Register reg) const;
+
+  // Constant loads to accumulator.
   BytecodeArrayBuilder& LoadLiteral(v8::internal::Smi* value);
   BytecodeArrayBuilder& LoadLiteral(Handle<Object> object);
   BytecodeArrayBuilder& LoadUndefined();
@@ -66,7 +73,7 @@ class BytecodeArrayBuilder {
   BytecodeArrayBuilder& LoadTrue();
   BytecodeArrayBuilder& LoadFalse();
 
-  // Global loads to accumulator and stores from the accumulator.
+  // Global loads to the accumulator and stores from the accumulator.
   BytecodeArrayBuilder& LoadGlobal(int slot_index);
   BytecodeArrayBuilder& StoreGlobal(int slot_index, LanguageMode language_mode);
 
@@ -140,7 +147,7 @@ class BytecodeArrayBuilder {
   BytecodeArrayBuilder& CompareOperation(Token::Value op, Register reg,
                                          Strength strength);
 
-  // Casts
+  // Casts.
   BytecodeArrayBuilder& CastAccumulatorToBoolean();
   BytecodeArrayBuilder& CastAccumulatorToName();
 
@@ -207,9 +214,14 @@ class BytecodeArrayBuilder {
 
   size_t GetConstantPoolEntry(Handle<Object> object);
 
-  // Scope helpers used by TemporaryRegisterScope
   int BorrowTemporaryRegister();
   void ReturnTemporaryRegister(int reg_index);
+  int PrepareForConsecutiveTemporaryRegisters(size_t count);
+  void BorrowConsecutiveTemporaryRegister(int reg_index);
+  bool TemporaryRegisterIsLive(Register reg) const;
+
+  Register first_temporary_register() const;
+  Register last_temporary_register() const;
 
   Isolate* isolate_;
   Zone* zone_;
@@ -226,10 +238,11 @@ class BytecodeArrayBuilder {
   int local_register_count_;
   int context_register_count_;
   int temporary_register_count_;
-  int temporary_register_next_;
+
+  ZoneSet<int> free_temporaries_;
 
   friend class TemporaryRegisterScope;
-  DISALLOW_IMPLICIT_CONSTRUCTORS(BytecodeArrayBuilder);
+  DISALLOW_COPY_AND_ASSIGN(BytecodeArrayBuilder);
 };
 
 
@@ -273,19 +286,26 @@ class BytecodeLabel final {
 
 // A stack-allocated class than allows the instantiator to allocate
 // temporary registers that are cleaned up when scope is closed.
+// TODO(oth): Deprecate TemporaryRegisterScope use. Code should be
+// using result scopes as far as possible.
 class TemporaryRegisterScope {
  public:
   explicit TemporaryRegisterScope(BytecodeArrayBuilder* builder);
   ~TemporaryRegisterScope();
   Register NewRegister();
 
+  void PrepareForConsecutiveAllocations(size_t count);
+  Register NextConsecutiveRegister();
+
  private:
   void* operator new(size_t size);
   void operator delete(void* p);
 
   BytecodeArrayBuilder* builder_;
-  int count_;
-  int last_register_index_;
+  const TemporaryRegisterScope* outer_;
+  ZoneVector<int> allocated_;
+  int next_consecutive_register_;
+  int next_consecutive_count_;
 
   DISALLOW_COPY_AND_ASSIGN(TemporaryRegisterScope);
 };