Implemented function that returns code age.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index dc2db4b096b76ddb7c36532a51be7106c9b6838b..769a3a80de7a9772b1ed773108020c25164b0887 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -1002,6 +1002,7 @@ void CodeFlusher::ProcessJSFunctionCandidates() {
     Code* code = shared->code();
     MarkBit code_mark = Marking::MarkBitFrom(code);
     if (!code_mark.Get()) {
+      ASSERT(!FLAG_age_code || code->GetAge() >= Code::kSexagenarianCodeAge);

[Michael Starzinger, 2013/06/12 09:09:32]

I don't think this assert is entirely correct, if there are two closures
enqueued as flushing candidates then the first one will already have cleared the
SharedFunctionInfo, the second one already has cleared code. Sure, the
LazyRecompileStub should always be marked, but still, this assert seems mighty
weird and confuses more than it helps. Asserts should clarify the code an make
it safer, not make it harder to understand.

How about we move this assert outside the if, and rephrase is slightly to a more
general form ...

ASSERT(!FLAG_arg_code || !candidate->is_compiled() || code->GetAge() >= 3);

[Michael Starzinger, 2013/06/12 09:12:17]

Sorry, should have been ...

ASSERT(!FLAG_age_code || !candidate->is_compiled() ||
candidate->code()->GetAge() >= 3);

       if (FLAG_trace_code_flushing && shared->is_compiled()) {
         SmartArrayPointer<char> name = shared->DebugName()->ToCString();
         PrintF("[code-flushing clears: %s]\n", *name);
@@ -1043,6 +1044,7 @@ void CodeFlusher::ProcessSharedFunctionInfoCandidates() {
     Code* code = candidate->code();
     MarkBit code_mark = Marking::MarkBitFrom(code);
     if (!code_mark.Get()) {
+      ASSERT(!FLAG_age_code || code->GetAge() >= Code::kSexagenarianCodeAge);

[danno, 2013/06/12 09:08:13]

Perhaps add a constant for Code::kOldCodeAge that is a copy of
Code::kSexagenarianCodeAge so that all usages are consistent and named?

[Michael Starzinger, 2013/06/12 09:09:32]

Likewise.

       if (FLAG_trace_code_flushing && candidate->is_compiled()) {
         SmartArrayPointer<char> name = candidate->DebugName()->ToCString();
         PrintF("[code-flushing clears: %s]\n", *name);