[Tracing] Implement IC statistics in tracing.

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index f0f38ebe9376962df326dab42cc1abff0f67958a..52ca32f6a6bd83fc2f29abdc60ce5d3753487224 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -14,8 +14,10 @@
 #include "src/gdb-jit.h"
 #include "src/ic/accessor-assembler.h"
 #include "src/ic/handler-compiler.h"
+#include "src/ic/ic-stats.h"
 #include "src/ic/ic.h"
 #include "src/macro-assembler.h"
+#include "src/tracing/tracing-category-observer.h"
 
 namespace v8 {
 namespace internal {
@@ -2290,11 +2292,23 @@ void HydrogenCodeStub::TraceTransition(StateType from, StateType to) {
   // Note: Although a no-op transition is semantically OK, it is hinting at a
   // bug somewhere in our state transition machinery.
   DCHECK(from != to);
-  if (!FLAG_trace_ic) return;
-  OFStream os(stdout);
-  os << "[";
-  PrintBaseName(os);
-  os << ": " << from << "=>" << to << "]" << std::endl;
+  if (V8_LIKELY(!FLAG_ic_stats)) return;
+  if (FLAG_ic_stats &
+      v8::tracing::TracingCategoryObserver::ENABLED_BY_TRACING) {
+    auto ic_stats = ICStats::instance();
+    ic_stats->Begin();
+    ICInfo& ic_info = ic_stats->Current();
+    ic_info.type = MajorName(MajorKey());
+    ic_info.state = ToString(from);
+    ic_info.state += "=>";
+    ic_info.state += ToString(to);
+    ic_stats->End();
+  } else if (FLAG_ic_stats) {

[Camillo Bruni, 2016/12/05 20:13:50]

nit: drop this check as you the early return above will ensure FLAG_ic_stats !=
0.

[lpy, 2016/12/05 22:38:11]

Done.

+    OFStream os(stdout);
+    os << "[";
+    PrintBaseName(os);
+    os << ": " << from << "=>" << to << "]" << std::endl;
+  }
 }
 
 void CallICStub::PrintState(std::ostream& os) const {  // NOLINT