[Interpreter] Add dispatch counters for each bytecode.

src/d8.cc

Index: src/d8.cc
diff --git a/src/d8.cc b/src/d8.cc
index d7e1b6ab06e6fa67638dd74f89434b5c78f6b404..0ce0d5b1d8f1f29487c56f6884870e1efb63c500 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -9,6 +9,7 @@
 #endif
 
 #include <errno.h>
+#include <inttypes.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
@@ -41,6 +42,7 @@
 #include "src/base/platform/platform.h"
 #include "src/base/sys-info.h"
 #include "src/basic-block-profiler.h"
+#include "src/interpreter/interpreter.h"
 #include "src/snapshot/natives.h"
 #include "src/utils.h"
 #include "src/v8.h"
@@ -1335,6 +1337,20 @@ void Shell::OnExit(v8::Isolate* isolate) {
         printf("| %-62s | %11i |\n", key, counter->count());
       }
     }
+    if (i::FLAG_ignition_count_handler_dispatches) {
+      uint32_t* handler_dispatch_counters =
+          reinterpret_cast<i::Isolate*>(isolate)
+              ->interpreter()
+              ->handlers_dispatch_counters();
+      for (int i = 0; i <= static_cast<int>(i::interpreter::Bytecode::kLast);
+           ++i) {
+        i::interpreter::Bytecode bytecode =
+            i::interpreter::Bytecodes::FromByte(i);
+        printf("| c:V8.Ignition_DispatchCounter_%-32s | %11" PRIu32 " |\n",
+               i::interpreter::Bytecodes::ToString(bytecode),
+               handler_dispatch_counters[i]);
+      }
+    }

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

As discussed, maybe we could output json for this case too. Is there anywhere we
could put this where it wouldn't be d8 specific (i.e., could be used by Chrome
too?

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

Done JSON. As of where to move this, I'll start by extracting a function to do
the job, which does not depend on anything Shell specific, so we are free to
move it wherever it seems more appropriate.

     printf("+----------------------------------------------------------------+"
            "-------------+\n");
     delete [] counters;