[Interpreter] Add dispatch counters for each bytecode.

src/interpreter/interpreter.h

 // 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.
 
 #ifndef V8_INTERPRETER_INTERPRETER_H_
 #define V8_INTERPRETER_INTERPRETER_H_
 
 // Clients of this interface shouldn't depend on lots of interpreter internals.
 // Do not include anything from src/interpreter other than
 // src/interpreter/bytecodes.h here!
@@ skipping 35 matching lines @@
   void IterateDispatchTable(ObjectVisitor* v);
 
   // Disassembler support (only useful with ENABLE_DISASSEMBLER defined).
   void TraceCodegen(Handle<Code> code);
   const char* LookupNameOfBytecodeHandler(Code* code);
 
   Address dispatch_table_address() {
     return reinterpret_cast<Address>(&dispatch_table_[0]);
   }
 
+  uint32_t* handlers_dispatch_counters() {
+    return &handlers_dispatch_counters_[0];
+  }
+
   // 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, ...) \
   void Do##Name(InterpreterAssembler* assembler);
   BYTECODE_LIST(DECLARE_BYTECODE_HANDLER_GENERATOR)
 #undef DECLARE_BYTECODE_HANDLER_GENERATOR
@@ skipping 72 matching lines @@
   static size_t GetDispatchTableIndex(Bytecode bytecode,
                                       OperandScale operand_scale);
 
   bool IsDispatchTableInitialized();
 
   static const int kNumberOfWideVariants = 3;
   static const int kDispatchTableSize = kNumberOfWideVariants * (kMaxUInt8 + 1);
 
   Isolate* isolate_;
   Code* dispatch_table_[kDispatchTableSize];
+  uint32_t handlers_dispatch_counters_[kDispatchTableSize];

[rmcilroy, 2016/03/23 11:04:26]

Do we need the 3x size of the dispatch table, or do we only need counters for
each non-scaled bytecode variant (I think the code in IncrementDispatchCounter
only updates the initial 256 entries of this table (which is probably what we
want, rather than having a few sparse counts of wide bytecode variants).

[Stefano Sanfilippo, 2016/03/23 16:26:27]

I have created a new kCountersTableRowSize constant and moved it to the public
part, so that it can be used externally (e.g. in for loops).

 
   DISALLOW_COPY_AND_ASSIGN(Interpreter);
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_INTERPRETER_H_