[turbofan] Collect invocation counts and compute relative call frequencies.

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/context-slot-cache.h"
 #include "src/base/bits.h"
@@ skipping 2802 matching lines @@
     Object* megamorphic = *TypeFeedbackVector::MegamorphicSentinel(isolate());
     dummy_vector->Set(load_ic_slot, megamorphic, SKIP_WRITE_BARRIER);
     dummy_vector->Set(keyed_load_ic_slot, megamorphic, SKIP_WRITE_BARRIER);
     dummy_vector->Set(store_ic_slot, megamorphic, SKIP_WRITE_BARRIER);
     dummy_vector->Set(keyed_store_ic_slot, megamorphic, SKIP_WRITE_BARRIER);
 
     set_dummy_vector(*dummy_vector);
   }
 
   {
+    // Create a canonical empty TypeFeedbackVector, which is shared by all
+    // functions that don't need actual type feedback slots. Note however
+    // that all these functions will share the same invocation count, but
+    // that shouldn't matter since we only use the invocation count to
+    // relativize the absolute call counts, but we can only have call counts
+    // if we have actual feedback slots.
+    Handle<FixedArray> empty_type_feedback_vector = factory->NewFixedArray(
+        TypeFeedbackVector::kReservedIndexCount, TENURED);
+    empty_type_feedback_vector->set(TypeFeedbackVector::kMetadataIndex,
+                                    empty_fixed_array());
+    empty_type_feedback_vector->set(TypeFeedbackVector::kInvocationCountIndex,
+                                    Smi::FromInt(0));
+    set_empty_type_feedback_vector(*empty_type_feedback_vector);
+
+    // We use a canonical empty LiteralsArray for all functions that neither
+    // have literals nor need a TypeFeedbackVector (besides the invocation
+    // count special slot).
     Handle<FixedArray> empty_literals_array =
         factory->NewFixedArray(1, TENURED);
-    empty_literals_array->set(0, *factory->empty_fixed_array());
+    empty_literals_array->set(0, *empty_type_feedback_vector);
     set_empty_literals_array(*empty_literals_array);
   }
 
   {
     Handle<FixedArray> empty_sloppy_arguments_elements =
         factory->NewFixedArray(2, TENURED);
     empty_sloppy_arguments_elements->set_map(sloppy_arguments_elements_map());
     set_empty_sloppy_arguments_elements(*empty_sloppy_arguments_elements);
   }
 
@@ skipping 3683 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8