[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 075fe741e943f064f22184c727cc04c823ea3fb3..1a44d225c882160741ef7359ccc0066471db8f1f 100644
--- a/src/interpreter/interpreter.h
+++ b/src/interpreter/interpreter.h
@@ -53,6 +53,10 @@ class Interpreter {
     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);
@@ -145,6 +149,7 @@ class Interpreter {
 
   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);
 };