[heap] Refactor and simplify pretenuring infrastructure

Bug: 
Change-Id: I81132af45d8fb649d4239fa0e0ef75b95e148208
Reviewed-on: https://chromium-review.googlesource.com/633604
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47606}

src/heap/heap-inl.h

@@ -518,9 +518,9 @@ AllocationMemento* Heap::FindAllocationMemento(Map* map, HeapObject* object) {
   UNREACHABLE();
 }
 
-template <Heap::UpdateAllocationSiteMode mode>
 void Heap::UpdateAllocationSite(Map* map, HeapObject* object,
-                                base::HashMap* pretenuring_feedback) {
+                                PretenuringFeedbackMap* pretenuring_feedback) {
+  DCHECK_NE(pretenuring_feedback, &global_pretenuring_feedback_);
   DCHECK(InFromSpace(object) ||
          (InToSpace(object) &&
           Page::FromAddress(object->address())
@@ -535,37 +535,16 @@ void Heap::UpdateAllocationSite(Map* map, HeapObject* object,
       FindAllocationMemento<kForGC>(map, object);
   if (memento_candidate == nullptr) return;
 
-  if (mode == kGlobal) {
-    DCHECK_EQ(pretenuring_feedback, global_pretenuring_feedback_);
-    // Entering global pretenuring feedback is only used in the scavenger, where
-    // we are allowed to actually touch the allocation site.
-    if (!memento_candidate->IsValid()) return;
-    AllocationSite* site = memento_candidate->GetAllocationSite();
-    DCHECK(!site->IsZombie());
-    // For inserting in the global pretenuring storage we need to first
-    // increment the memento found count on the allocation site.
-    if (site->IncrementMementoFoundCount()) {
-      global_pretenuring_feedback_->LookupOrInsert(site,
-                                                   ObjectHash(site->address()));
-    }
-  } else {
-    DCHECK_EQ(mode, kCached);
-    DCHECK_NE(pretenuring_feedback, global_pretenuring_feedback_);
   // Entering cached feedback is used in the parallel case. We are not allowed
   // to dereference the allocation site and rather have to postpone all checks
   // till actually merging the data.
   Address key = memento_candidate->GetAllocationSiteUnchecked();
-    base::HashMap::Entry* e =
-        pretenuring_feedback->LookupOrInsert(key, ObjectHash(key));
-    DCHECK(e != nullptr);
-    (*bit_cast<intptr_t*>(&e->value))++;
-  }
+  (*pretenuring_feedback)[reinterpret_cast<AllocationSite*>(key)]++;
 }
 
 
 void Heap::RemoveAllocationSitePretenuringFeedback(AllocationSite* site) {
-  global_pretenuring_feedback_->Remove(
-      site, static_cast<uint32_t>(bit_cast<uintptr_t>(site)));
+  global_pretenuring_feedback_.erase(site);
 }
 
 Isolate* Heap::isolate() {

src/heap/heap.cc

@@ -164,7 +164,7 @@ Heap::Heap()
       new_space_allocation_counter_(0),
       old_generation_allocation_counter_at_last_gc_(0),
       old_generation_size_at_last_gc_(0),
-      global_pretenuring_feedback_(nullptr),
+      global_pretenuring_feedback_(kInitialFeedbackCapacity),
       is_marking_flag_(false),
       ring_buffer_full_(false),
       ring_buffer_end_(0),
@@ -603,13 +603,11 @@ void Heap::RepairFreeListsAfterDeserialization() {
 }
 
 void Heap::MergeAllocationSitePretenuringFeedback(
-    const base::HashMap& local_pretenuring_feedback) {
+    const PretenuringFeedbackMap& local_pretenuring_feedback) {
   AllocationSite* site = nullptr;
-  for (base::HashMap::Entry* local_entry = local_pretenuring_feedback.Start();
-       local_entry != nullptr;
-       local_entry = local_pretenuring_feedback.Next(local_entry)) {
-    site = reinterpret_cast<AllocationSite*>(local_entry->key);
-    MapWord map_word = site->map_word();
+  for (auto& site_and_count : local_pretenuring_feedback) {
+    site = site_and_count.first;
+    MapWord map_word = site_and_count.first->map_word();
     if (map_word.IsForwardingAddress()) {
       site = AllocationSite::cast(map_word.ToForwardingAddress());
     }
@@ -619,13 +617,11 @@ void Heap::MergeAllocationSitePretenuringFeedback(
     // This is an inlined check of AllocationMemento::IsValid.
     if (!site->IsAllocationSite() || site->IsZombie()) continue;
 
-    int value =
-        static_cast<int>(reinterpret_cast<intptr_t>(local_entry->value));
-    DCHECK_GT(value, 0);
-
+    const int value = static_cast<int>(site_and_count.second);
+    DCHECK_LT(0, value);
     if (site->IncrementMementoFoundCount(value)) {
-      global_pretenuring_feedback_->LookupOrInsert(site,
-                                                   ObjectHash(site->address()));
+      // For sites in the global map the count is accessed through the site.
+      global_pretenuring_feedback_.insert(std::make_pair(site, 0));
     }
   }
 }
@@ -647,22 +643,6 @@ class Heap::SkipStoreBufferScope {
   StoreBuffer* store_buffer_;
 };
 
-class Heap::PretenuringScope {
- public:
-  explicit PretenuringScope(Heap* heap) : heap_(heap) {
-    heap_->global_pretenuring_feedback_ =
-        new base::HashMap(kInitialFeedbackCapacity);
-  }
-
-  ~PretenuringScope() {
-    delete heap_->global_pretenuring_feedback_;
-    heap_->global_pretenuring_feedback_ = nullptr;
-  }
-
- private:
-  Heap* heap_;
-};
-
 namespace {
 inline bool MakePretenureDecision(
     AllocationSite* site, AllocationSite::PretenureDecision current_decision,
@@ -736,10 +716,11 @@ void Heap::ProcessPretenuringFeedback() {
 
     // Step 1: Digest feedback for recorded allocation sites.
     bool maximum_size_scavenge = MaximumSizeScavenge();
-    for (base::HashMap::Entry* e = global_pretenuring_feedback_->Start();
-         e != nullptr; e = global_pretenuring_feedback_->Next(e)) {
+    for (auto& site_and_count : global_pretenuring_feedback_) {
       allocation_sites++;
-      site = reinterpret_cast<AllocationSite*>(e->key);
+      site = site_and_count.first;
+      // Count is always access through the site.
+      DCHECK_EQ(0, site_and_count.second);
       int found_count = site->memento_found_count();
       // An entry in the storage does not imply that the count is > 0 because
       // allocation sites might have been reset due to too many objects dying
@@ -790,6 +771,9 @@ void Heap::ProcessPretenuringFeedback() {
                    active_allocation_sites, allocation_mementos_found,
                    tenure_decisions, dont_tenure_decisions);
     }
+
+    global_pretenuring_feedback_.clear();
+    global_pretenuring_feedback_.reserve(kInitialFeedbackCapacity);
   }
 }
 
@@ -1516,7 +1500,6 @@ bool Heap::PerformGarbageCollection(
   int start_new_space_size = static_cast<int>(Heap::new_space()->Size());
 
   {
-    Heap::PretenuringScope pretenuring_scope(this);
     Heap::SkipStoreBufferScope skip_store_buffer_scope(store_buffer_);
 
     switch (collector) {

src/heap/heap.h

@@ -6,6 +6,7 @@
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
+#include <unordered_map>
 #include <vector>
 
 // Clients of this interface shouldn't depend on lots of heap internals.
@@ -554,7 +555,7 @@ class Heap {
 
   enum HeapState { NOT_IN_GC, SCAVENGE, MARK_COMPACT, MINOR_MARK_COMPACT };
 
-  enum UpdateAllocationSiteMode { kGlobal, kCached };
+  using PretenuringFeedbackMap = std::unordered_map<AllocationSite*, size_t>;
 
   // Taking this mutex prevents the GC from entering a phase that relocates
   // object references.
@@ -1473,14 +1474,11 @@ class Heap {
   // Allocation site tracking. =================================================
   // ===========================================================================
 
-  // Updates the AllocationSite of a given {object}. If the global prenuring
-  // storage is passed as {pretenuring_feedback} the memento found count on
-  // the corresponding allocation site is immediately updated and an entry
-  // in the hash map is created. Otherwise the entry (including a the count
-  // value) is cached on the local pretenuring feedback.
-  template <UpdateAllocationSiteMode mode>
-  inline void UpdateAllocationSite(Map* map, HeapObject* object,
-                                   base::HashMap* pretenuring_feedback);
+  // Updates the AllocationSite of a given {object}. The entry (including the
+  // count) is cached on the local pretenuring feedback.
+  inline void UpdateAllocationSite(
+      Map* map, HeapObject* object,
+      PretenuringFeedbackMap* pretenuring_feedback);
 
   // Removes an entry from the global pretenuring storage.
   inline void RemoveAllocationSitePretenuringFeedback(AllocationSite* site);
@@ -1489,7 +1487,7 @@ class Heap {
   // method needs to be called after evacuation, as allocation sites may be
   // evacuated and this method resolves forward pointers accordingly.
   void MergeAllocationSitePretenuringFeedback(
-      const base::HashMap& local_pretenuring_feedback);
+      const PretenuringFeedbackMap& local_pretenuring_feedback);
 
   // ===========================================================================
   // Retaining path tracking. ==================================================
@@ -2375,7 +2373,7 @@ class Heap {
   // storage is only alive temporary during a GC. The invariant is that all
   // pointers in this map are already fixed, i.e., they do not point to
   // forwarding pointers.
-  base::HashMap* global_pretenuring_feedback_;
+  PretenuringFeedbackMap global_pretenuring_feedback_;
 
   char trace_ring_buffer_[kTraceRingBufferSize];
 

src/heap/mark-compact.cc

@@ -1680,9 +1680,10 @@ class EvacuateVisitorBase : public HeapObjectVisitor {
 
 class EvacuateNewSpaceVisitor final : public EvacuateVisitorBase {
  public:
-  explicit EvacuateNewSpaceVisitor(Heap* heap, LocalAllocator* local_allocator,
+  explicit EvacuateNewSpaceVisitor(
+      Heap* heap, LocalAllocator* local_allocator,
       RecordMigratedSlotVisitor* record_visitor,
-                                   base::HashMap* local_pretenuring_feedback)
+      Heap::PretenuringFeedbackMap* local_pretenuring_feedback)
       : EvacuateVisitorBase(heap, local_allocator, record_visitor),
         buffer_(LocalAllocationBuffer::InvalidBuffer()),
         promoted_size_(0),
@@ -1696,7 +1697,7 @@ class EvacuateNewSpaceVisitor final : public EvacuateVisitorBase {
       promoted_size_ += size;
       return true;
     }
-    heap_->UpdateAllocationSite<Heap::kCached>(object->map(), object,
+    heap_->UpdateAllocationSite(object->map(), object,
                                 local_pretenuring_feedback_);
     HeapObject* target = nullptr;
     AllocationSpace space = AllocateTargetObject(object, size, &target);
@@ -1739,7 +1740,7 @@ class EvacuateNewSpaceVisitor final : public EvacuateVisitorBase {
   LocalAllocationBuffer buffer_;
   intptr_t promoted_size_;
   intptr_t semispace_copied_size_;
-  base::HashMap* local_pretenuring_feedback_;
+  Heap::PretenuringFeedbackMap* local_pretenuring_feedback_;
 };
 
 template <PageEvacuationMode mode>
@@ -1747,7 +1748,7 @@ class EvacuateNewSpacePageVisitor final : public HeapObjectVisitor {
  public:
   explicit EvacuateNewSpacePageVisitor(
       Heap* heap, RecordMigratedSlotVisitor* record_visitor,
-      base::HashMap* local_pretenuring_feedback)
+      Heap::PretenuringFeedbackMap* local_pretenuring_feedback)
       : heap_(heap),
         record_visitor_(record_visitor),
         moved_bytes_(0),
@@ -1771,7 +1772,7 @@ class EvacuateNewSpacePageVisitor final : public HeapObjectVisitor {
 
   inline bool Visit(HeapObject* object, int size) {
     if (mode == NEW_TO_NEW) {
-      heap_->UpdateAllocationSite<Heap::kCached>(object->map(), object,
+      heap_->UpdateAllocationSite(object->map(), object,
                                   local_pretenuring_feedback_);
     } else if (mode == NEW_TO_OLD) {
       object->IterateBodyFast(record_visitor_);
@@ -1786,7 +1787,7 @@ class EvacuateNewSpacePageVisitor final : public HeapObjectVisitor {
   Heap* heap_;
   RecordMigratedSlotVisitor* record_visitor_;
   intptr_t moved_bytes_;
-  base::HashMap* local_pretenuring_feedback_;
+  Heap::PretenuringFeedbackMap* local_pretenuring_feedback_;
 };
 
 class EvacuateOldSpaceVisitor final : public EvacuateVisitorBase {
@@ -3290,7 +3291,7 @@ class Evacuator : public Malloced {
   // Locally cached collector data.
   LocalAllocator local_allocator_;
   CompactionSpaceCollection compaction_spaces_;
-  base::HashMap local_pretenuring_feedback_;
+  Heap::PretenuringFeedbackMap local_pretenuring_feedback_;
 
   // Visitors for the corresponding spaces.
   EvacuateNewSpaceVisitor new_space_visitor_;

src/heap/scavenger-inl.h

@@ -70,8 +70,7 @@ bool Scavenger::MigrateObject(Map* map, HeapObject* source, HeapObject* target,
   if (is_incremental_marking_) {
     heap()->incremental_marking()->TransferColor(source, target);
   }
-  heap()->UpdateAllocationSite<Heap::kCached>(map, source,
-                                              &local_pretenuring_feedback_);
+  heap()->UpdateAllocationSite(map, source, &local_pretenuring_feedback_);
   return true;
 }
 

src/heap/scavenger.h

@@ -129,7 +129,7 @@ class Scavenger {
   Heap* const heap_;
   PromotionList::View promotion_list_;
   CopiedList::View copied_list_;
-  base::HashMap local_pretenuring_feedback_;
+  Heap::PretenuringFeedbackMap local_pretenuring_feedback_;
   size_t copied_size_;
   size_t promoted_size_;
   LocalAllocator allocator_;