[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);
 
+  static const int kNumberOfWideVariants = 3;
+  static const int kDispatchTableSize = kNumberOfWideVariants * (kMaxUInt8 + 1);
+  static const int kCountersTableRowSize =
+      static_cast<int>(Bytecode::kLast) + 1;

[rmcilroy, 2016/04/05 10:00:46]

Please keep these private. I don't think you need kCountersTableRowSize either
(just use Bytecode::kLast + 1 where needed).

[Stefano Sanfilippo, 2016/04/05 14:01:46]

Moved to private.

I'd be in favour of keeping the kCountersTableRowSize constant, it will be
useful for the follow-up CL (handler to handler counters).

+
  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
 
   // Generates code to perform the binary operations via |callable|.
   void DoBinaryOp(Callable callable, InterpreterAssembler* assembler);
 
@@ skipping 63 matching lines @@
   // Generates code to perform a lookup slot store depending on |language_mode|.
   void DoStoreLookupSlot(LanguageMode language_mode,
                          InterpreterAssembler* assembler);
 
   // Get dispatch table index of bytecode.
   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_[kCountersTableRowSize];

[rmcilroy, 2016/04/05 10:00:46]

Could we make this a smart pointer which is only allocated if the flag is set
(avoid wasting memory). Also, how about we just make this uintptr_t size, (with
appropriate updates in the interpreter-assembler generated code) that way we get
64bit counters on 64bit platforms.

[Stefano Sanfilippo, 2016/04/05 14:01:46]

I replaced the array with a std::vector which gets resize()'d only if the flag
is enabled. Done.

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