[Interpreter] Add bytecode aging and use it enable CompilationCache for bytecode

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 9a903f1ff59ad217d25a74e53589927ea1d12ff7..1b066d89cb2e1d270d117b711ac6995bc61931a5 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -15175,6 +15175,19 @@ int BytecodeArray::LookupRangeInHandlerTable(
   return table->LookupRange(code_offset, data, prediction);
 }
 
+void BytecodeArray::MakeOlder() {
+  Age age = bytecode_age();
+  if (age < kLastBytecodeAge) {
+    set_bytecode_age(static_cast<Age>(age + 1));
+  }
+  DCHECK_GE(age, kFirstBytecodeAge);
+  DCHECK_LE(age, kLastBytecodeAge);

[Michael Starzinger, 2016/11/28 14:21:30]

nit: Shouldn't these DCHECKs be applied on the _new_ age? Or alternatively I
would vote for moving them 3 lines up to before the new value is stored (for
readability).

[rmcilroy, 2016/11/28 14:29:04]

Yes the should, updated to check bytecode_age() instead

+}
+
+bool BytecodeArray::IsOld() const {
+  return bytecode_age() >= kIsOldBytecodeAge;
+}
+
 // static
 void JSArray::Initialize(Handle<JSArray> array, int capacity, int length) {
   DCHECK(capacity >= 0);
@@ -17970,7 +17983,11 @@ void CompilationCacheTable::Age() {
       }
     } else if (get(entry_index)->IsFixedArray()) {
       SharedFunctionInfo* info = SharedFunctionInfo::cast(get(value_index));
-      if (info->code()->kind() != Code::FUNCTION || info->code()->IsOld()) {
+      bool is_old =
+          info->IsInterpreted()
+              ? info->bytecode_array()->IsOld()
+              : info->code()->kind() != Code::FUNCTION || info->code()->IsOld();
+      if (is_old) {
         NoWriteBarrierSet(this, entry_index, the_hole_value);
         NoWriteBarrierSet(this, value_index, the_hole_value);
         ElementRemoved();