[Interpreter] Add dispatch counters for each bytecode.

src/interpreter/interpreter.h

Index: src/interpreter/interpreter.h
diff --git a/src/interpreter/interpreter.h b/src/interpreter/interpreter.h
index ea50faa02d882c91bee2cdd2912a2cd6e7486db7..524268e8b8472d22df3adfd43b3668baf055a330 100644
--- a/src/interpreter/interpreter.h
+++ b/src/interpreter/interpreter.h
@@ -53,6 +53,12 @@ class Interpreter {
     return reinterpret_cast<Address>(&dispatch_table_[0]);
   }
 
+  uintptr_t* dispatch_counters() { return handlers_dispatch_counters_.get(); }
+
+  // Returns true if a handler is generated for a bytecode at a given
+  // operand scale.
+  static bool BytecodeHasHandler(Bytecode bytecode, OperandScale operand_scale);
+
  private:
 // Bytecode handler generator functions.
 #define DECLARE_BYTECODE_HANDLER_GENERATOR(Name, ...) \
@@ -138,9 +144,12 @@ class Interpreter {
 
   static const int kNumberOfWideVariants = 3;
   static const int kDispatchTableSize = kNumberOfWideVariants * (kMaxUInt8 + 1);
+  static const int kCountersTableRowSize =
+      static_cast<int>(Bytecode::kLast) + 1;
 
   Isolate* isolate_;
   Code* dispatch_table_[kDispatchTableSize];
+  v8::base::SmartArrayPointer<uintptr_t> handlers_dispatch_counters_;
 
   DISALLOW_COPY_AND_ASSIGN(Interpreter);
 };