[Interpreter] Add dispatch counters for each bytecode.

src/interpreter/interpreter-assembler.cc

Index: src/interpreter/interpreter-assembler.cc
diff --git a/src/interpreter/interpreter-assembler.cc b/src/interpreter/interpreter-assembler.cc
index 8e983e24d2a3735aac941fe387791a67107e699c..2ff16ffdbf0c6fdec76665f8cd7aec17b1edc68e 100644
--- a/src/interpreter/interpreter-assembler.cc
+++ b/src/interpreter/interpreter-assembler.cc
@@ -4,6 +4,7 @@
 
 #include "src/interpreter/interpreter-assembler.h"
 
+#include <limits>
 #include <ostream>
 
 #include "src/code-factory.h"
@@ -43,6 +44,9 @@ InterpreterAssembler::InterpreterAssembler(Isolate* isolate, Zone* zone,
   if (FLAG_trace_ignition) {
     TraceBytecode(Runtime::kInterpreterTraceBytecodeEntry);
   }
+  if (FLAG_ignition_count_handler_dispatches) {
+    IncrementDispatchCounter();
+  }
 }
 
 InterpreterAssembler::~InterpreterAssembler() {}
@@ -610,6 +614,30 @@ void InterpreterAssembler::InterpreterReturn() {
   DispatchToBytecodeHandler(exit_trampoline_code_object);
 }
 
+void InterpreterAssembler::IncrementDispatchCounter() {

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

nit - could you move this to be near TraceBytecode

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

Done.

+  Node* counters = ExternalConstant(
+      ExternalReference::interpreter_handlers_dispatch_counters(isolate()));
+  Node* counter_offset =
+      IntPtrConstant(static_cast<int>(bytecode_) * sizeof(uint32_t));
+  Node* old_counter = Load(MachineType::Uint32(), counters, counter_offset);
+
+  CodeStubAssembler::Label counter_ok(this);
+  CodeStubAssembler::Label counter_saturated(this);
+  CodeStubAssembler::Label end(this);
+
+  Node* counter_reached_max = Word32Equal(
+      old_counter, Int32Constant(std::numeric_limits<uint32_t>::max()));
+  Branch(counter_reached_max, &counter_saturated, &counter_ok);
+  Bind(&counter_ok);
+  Node* new_counter = Int32Add(old_counter, Int32Constant(1));
+  StoreNoWriteBarrier(MachineRepresentation::kWord32, counters, counter_offset,
+                      new_counter);
+  Goto(&end);
+  Bind(&counter_saturated);
+  Goto(&end);
+  Bind(&end);
+}
+
 void InterpreterAssembler::StackCheck() {
   CodeStubAssembler::Label end(this);
   CodeStubAssembler::Label ok(this);