[Interpreter] Enable tracing of bytecode handler dispatches.

src/d8.cc

Index: src/d8.cc
diff --git a/src/d8.cc b/src/d8.cc
index c23c1a4a9c722f0839fd4ca4976c41e90b10cda0..14c75f1ac12bf157b20ca9b407f961c011b404a6 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -12,6 +12,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
+#include <fstream>
 
 #ifdef V8_SHARED
 #include <assert.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"
@@ -1275,6 +1277,40 @@ struct CounterAndKey {
 inline bool operator<(const CounterAndKey& lhs, const CounterAndKey& rhs) {
   return strcmp(lhs.key, rhs.key) < 0;
 }
+
+void Shell::WriteInterpreterDispatchCounters(Isolate* isolate) {
+  std::ofstream stream(i::FLAG_trace_ignition_dispatches_output_file);
+
+  uintptr_t* handler_to_handler_dispatch_counters =
+      reinterpret_cast<i::Isolate*>(isolate)
+          ->interpreter()
+          ->handler_to_handler_dispatch_counters();
+
+  int kCountersTableRowSize =

[rmcilroy, 2016/04/08 11:24:43]

static const

[Stefano Sanfilippo, 2016/04/08 14:42:44]

Done.

+      static_cast<int>(i::interpreter::Bytecode::kLast) + 1;
+
+  stream << '[';
+
+  for (int from_index = 0; from_index < kCountersTableRowSize; ++from_index) {
+    if (from_index > 0) stream << ",\n ";
+
+    // Do not use an object, we need the order of entries to be preserved

[rmcilroy, 2016/04/08 11:24:43]

Not sure what this comment means? Also, could we have the output be a dictionary
of named target bytecode (only for those target bytecodes with a dispatch count
> 0) rather than an ordered list. Relying on the ordering of the source
bytecodes to show the order of the unnamed target bytecode list seems brittle.

[Stefano Sanfilippo, 2016/04/08 14:42:44]

Replaced with dictionary of dictionaries.

+    i::interpreter::Bytecode from_bytecode =
+        i::interpreter::Bytecodes::FromByte(from_index);
+    stream << "[\"" << i::interpreter::Bytecodes::ToString(from_bytecode)
+           << "\", [";
+
+    for (int to_index = 0; to_index < kCountersTableRowSize; ++to_index) {
+      if (to_index > 0) stream << ", ";
+      stream << handler_to_handler_dispatch_counters[from_index *
+                                                         kCountersTableRowSize +
+                                                     to_index];
+    }
+    stream << "]]";
+  }
+  stream << ']';
+}
+
 #endif  // !V8_SHARED
 
 
@@ -1312,6 +1348,11 @@ void Shell::OnExit(v8::Isolate* isolate) {
            "-------------+\n");
     delete [] counters;
   }
+
+  if (i::FLAG_trace_ignition_dispatches) {
+    WriteInterpreterDispatchCounters(isolate);
+  }
+
   delete counters_file_;
   delete counter_map_;
 #endif  // !V8_SHARED