Refactor lithium classes to reduce the number of virtual functions.

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
===================================================================
--- src/x64/lithium-x64.h	(revision 7679)
+++ src/x64/lithium-x64.h	(working copy)
@@ -93,7 +93,6 @@
   V(ExternalArrayLength)                        \
   V(FixedArrayLength)                           \
   V(FunctionLiteral)                            \
-  V(Gap)                                        \
   V(GetCachedArrayIndex)                        \
   V(GlobalObject)                               \
   V(GlobalReceiver)                             \
@@ -105,6 +104,7 @@
   V(InstanceOf)                                 \
   V(InstanceOfAndBranch)                        \
   V(InstanceOfKnownGlobal)                      \
+  V(InstructionGap)                             \
   V(Integer32ToDouble)                          \
   V(InvokeFunction)                             \
   V(IsNull)                                     \
@@ -171,20 +171,16 @@
   V(ValueOf)
 
 
-#define DECLARE_INSTRUCTION(type)                \
-  virtual bool Is##type() const { return true; } \
-  static L##type* cast(LInstruction* instr) {    \
-    ASSERT(instr->Is##type());                   \
-    return reinterpret_cast<L##type*>(instr);    \
+#define DECLARE_CONCRETE_INSTRUCTION(type, mnemonic)              \
+  virtual Opcode opcode() const { return LInstruction::k##type; } \
+  virtual void CompileToNative(LCodeGen* generator);              \
+  virtual const char* Mnemonic() const { return mnemonic; }       \
+  static L##type* cast(LInstruction* instr) {                     \
+    ASSERT(instr->Is##type());                                    \
+    return reinterpret_cast<L##type*>(instr);                     \
   }
 
 
-#define DECLARE_CONCRETE_INSTRUCTION(type, mnemonic)        \
-  virtual void CompileToNative(LCodeGen* generator);        \
-  virtual const char* Mnemonic() const { return mnemonic; } \
-  DECLARE_INSTRUCTION(type)
-
-
 #define DECLARE_HYDROGEN_ACCESSOR(type)     \
   H##type* hydrogen() const {               \
     return H##type::cast(hydrogen_value()); \
@@ -207,11 +203,26 @@
   virtual void PrintDataTo(StringStream* stream) = 0;
   virtual void PrintOutputOperandTo(StringStream* stream) = 0;
 
-  // Declare virtual type testers.
-#define DECLARE_DO(type) virtual bool Is##type() const { return false; }
-  LITHIUM_ALL_INSTRUCTION_LIST(DECLARE_DO)
-#undef DECLARE_DO
+  enum Opcode {
+    // Declare a unique enum value for each instruction.
+#define DECLARE_OPCODE(type) k##type,
+    LITHIUM_CONCRETE_INSTRUCTION_LIST(DECLARE_OPCODE)
+    kNumberOfInstructions
+#undef DECLARE_OPCODE
+  };
 
+  virtual Opcode opcode() const = 0;
+
+  // Declare non-virtual type testers for all leaf IR classes.
+#define DECLARE_PREDICATE(type) \
+  bool Is##type() const { return opcode() == k##type; }
+  LITHIUM_CONCRETE_INSTRUCTION_LIST(DECLARE_PREDICATE)
+#undef DECLARE_PREDICATE
+
+  // Declare virtual predicates for instructions that don't have
+  // an opcode.
+  virtual bool IsGap() const { return false; }
+
   virtual bool IsControl() const { return false; }
   virtual void SetBranchTargets(int true_block_id, int false_block_id) { }
 
@@ -337,8 +348,13 @@
     parallel_moves_[AFTER] = NULL;
   }
 
-  DECLARE_CONCRETE_INSTRUCTION(Gap, "gap")
+  // Can't use the DECLARE-macro here because of sub-classes.
+  virtual bool IsGap() const { return true; }
   virtual void PrintDataTo(StringStream* stream);
+  static LGap* cast(LInstruction* instr) {
+    ASSERT(instr->IsGap());
+    return reinterpret_cast<LGap*>(instr);
+  }
 
   bool IsRedundant() const;
 
@@ -368,6 +384,14 @@
 };
 
 
+class LInstructionGap: public LGap {
+ public:
+  explicit LInstructionGap(HBasicBlock* block) : LGap(block) { }
+
+  DECLARE_CONCRETE_INSTRUCTION(InstructionGap, "gap")
+};
+
+
 class LGoto: public LTemplateInstruction<0, 0, 0> {
  public:
   LGoto(int block_id, bool include_stack_check = false)
@@ -456,7 +480,6 @@
 template<int I, int T>
 class LControlInstruction: public LTemplateInstruction<0, I, T> {
  public:
-  DECLARE_INSTRUCTION(ControlInstruction)
   virtual bool IsControl() const { return true; }
 
   int true_block_id() const { return true_block_id_; }
@@ -1092,6 +1115,7 @@
 
   Token::Value op() const { return op_; }
 
+  virtual Opcode opcode() const { return LInstruction::kArithmeticD; }
   virtual void CompileToNative(LCodeGen* generator);
   virtual const char* Mnemonic() const;
 
@@ -1108,6 +1132,7 @@
     inputs_[1] = right;
   }
 
+  virtual Opcode opcode() const { return LInstruction::kArithmeticT; }
   virtual void CompileToNative(LCodeGen* generator);
   virtual const char* Mnemonic() const;
 
@@ -2191,7 +2216,6 @@
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
-#undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int