Use weak cells in dependent code.

src/objects.cc

 // Copyright 2013 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 <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/allocation-site-scopes.h"
@@ skipping 11762 matching lines @@
   MemsetPointer(proto_transitions->data_start(),
                 GetHeap()->the_hole_value(),
                 proto_transitions->length());
 }
 
 
 // static
 void Map::AddDependentCompilationInfo(Handle<Map> map,
                                       DependentCode::DependencyGroup group,
                                       CompilationInfo* info) {
-  Handle<DependentCode> codes =
-      DependentCode::Insert(handle(map->dependent_code(), info->isolate()),
-                            group, info->object_wrapper());
+  Handle<DependentCode> codes = DependentCode::InsertCompilationInfo(
+      handle(map->dependent_code(), info->isolate()), group,
+      info->object_wrapper());
   if (*codes != map->dependent_code()) map->set_dependent_code(*codes);
   info->dependencies(group)->Add(map, info->zone());
 }
 
 
 // static
 void Map::AddDependentCode(Handle<Map> map,
                            DependentCode::DependencyGroup group,
                            Handle<Code> code) {
-  Handle<DependentCode> codes = DependentCode::Insert(
-      Handle<DependentCode>(map->dependent_code()), group, code);
+  Handle<WeakCell> cell = Code::WeakCellFor(code);
+  Handle<DependentCode> codes = DependentCode::InsertWeakCode(
+      Handle<DependentCode>(map->dependent_code()), group, cell);
   if (*codes != map->dependent_code()) map->set_dependent_code(*codes);
 }
 
 
 DependentCode::GroupStartIndexes::GroupStartIndexes(DependentCode* entries) {
   Recompute(entries);
 }
 
 
 void DependentCode::GroupStartIndexes::Recompute(DependentCode* entries) {
@@ skipping 11 matching lines @@
   if (group == DependentCode::kPropertyCellChangedGroup) {
     return Handle<PropertyCell>::cast(object)->dependent_code();
   } else if (group == DependentCode::kAllocationSiteTenuringChangedGroup ||
       group == DependentCode::kAllocationSiteTransitionChangedGroup) {
     return Handle<AllocationSite>::cast(object)->dependent_code();
   }
   return Handle<Map>::cast(object)->dependent_code();
 }
 
 
+Handle<DependentCode> DependentCode::InsertCompilationInfo(
+    Handle<DependentCode> entries, DependencyGroup group,
+    Handle<Foreign> info) {
+  return Insert(entries, group, info);
+}
+
+
+Handle<DependentCode> DependentCode::InsertWeakCode(
+    Handle<DependentCode> entries, DependencyGroup group,
+    Handle<WeakCell> code_cell) {
+  return Insert(entries, group, code_cell);
+}
+
+
 Handle<DependentCode> DependentCode::Insert(Handle<DependentCode> entries,
                                             DependencyGroup group,
                                             Handle<Object> object) {
   GroupStartIndexes starts(*entries);
   int start = starts.at(group);
   int end = starts.at(group + 1);
   int number_of_entries = starts.number_of_entries();
   // Check for existing entry to avoid duplicates.
   for (int i = start; i < end; i++) {
     if (entries->object_at(i) == *object) return entries;
   }
   if (entries->length() < kCodesStartIndex + number_of_entries + 1) {
-    int capacity = kCodesStartIndex + number_of_entries + 1;
-    if (capacity > 5) capacity = capacity * 5 / 4;
-    Handle<DependentCode> new_entries = Handle<DependentCode>::cast(
-        FixedArray::CopySize(entries, capacity, TENURED));
-    // The number of codes can change after GC.
+    entries = EnsureSpace(entries);
+    // The number of codes can change after Compact and GC.
     starts.Recompute(*entries);
     start = starts.at(group);
     end = starts.at(group + 1);
-    number_of_entries = starts.number_of_entries();
-    for (int i = 0; i < number_of_entries; i++) {
-      entries->clear_at(i);
-    }
-    // If the old fixed array was empty, we need to reset counters of the
-    // new array.
-    if (number_of_entries == 0) {
-      for (int g = 0; g < kGroupCount; g++) {
-        new_entries->set_number_of_entries(static_cast<DependencyGroup>(g), 0);
-      }
-    }
-    entries = new_entries;
   }
+
   entries->ExtendGroup(group);
   entries->set_object_at(end, *object);
   entries->set_number_of_entries(group, end + 1 - start);
   return entries;
 }
 
 
-void DependentCode::UpdateToFinishedCode(DependencyGroup group,
-                                         CompilationInfo* info,
-                                         Code* code) {
+Handle<DependentCode> DependentCode::EnsureSpace(
+    Handle<DependentCode> entries) {
+  if (entries->length() == 0) {
+    entries = Handle<DependentCode>::cast(
+        FixedArray::CopySize(entries, kCodesStartIndex + 1, TENURED));
+    for (int g = 0; g < kGroupCount; g++) {
+      entries->set_number_of_entries(static_cast<DependencyGroup>(g), 0);
+    }
+    return entries;
+  }
+  if (entries->Compact()) return entries;
+  GroupStartIndexes starts(*entries);
+  int capacity =
+      kCodesStartIndex + DependentCode::Grow(starts.number_of_entries());
+  return Handle<DependentCode>::cast(
+      FixedArray::CopySize(entries, capacity, TENURED));
+}
+
+
+bool DependentCode::Compact() {
+  GroupStartIndexes starts(this);
+  int n = 0;
+  for (int g = 0; g < kGroupCount; g++) {
+    int start = starts.at(g);
+    int end = starts.at(g + 1);
+    int count = 0;
+    for (int i = start; i < end; i++) {
+      Object* obj = object_at(i);
+      if (!obj->IsWeakCell() || !WeakCell::cast(obj)->cleared()) {
+        if (i != n + count) {
+          copy(i, n + count);

[Yang, 2015/01/27 14:43:24]

Can we assert here that i < n+count so that we never overwrite entries that have
not been copied yet?

+        }
+        count++;
+      }
+    }
+    if (count != end - start) {
+      set_number_of_entries(static_cast<DependencyGroup>(g), count);
+    }
+    n += count;
+  }
+  return n < starts.number_of_entries();
+}
+
+
+void DependentCode::UpdateToFinishedCode(DependencyGroup group, Foreign* info,
+                                         WeakCell* code_cell) {
   DisallowHeapAllocation no_gc;
-  AllowDeferredHandleDereference get_object_wrapper;
-  Foreign* info_wrapper = *info->object_wrapper();
   GroupStartIndexes starts(this);
   int start = starts.at(group);
   int end = starts.at(group + 1);
   for (int i = start; i < end; i++) {
-    if (object_at(i) == info_wrapper) {
-      set_object_at(i, code);
+    if (object_at(i) == info) {
+      set_object_at(i, code_cell);
       break;
     }
   }
 
 #ifdef DEBUG
   for (int i = start; i < end; i++) {
-    DCHECK(is_code_at(i) || compilation_info_at(i) != info);
+    DCHECK(object_at(i) != info);
   }
 #endif
 }
 
 
 void DependentCode::RemoveCompilationInfo(DependentCode::DependencyGroup group,
-                                          CompilationInfo* info) {
+                                          Foreign* info) {
   DisallowHeapAllocation no_allocation;
-  AllowDeferredHandleDereference get_object_wrapper;
-  Foreign* info_wrapper = *info->object_wrapper();
   GroupStartIndexes starts(this);
   int start = starts.at(group);
   int end = starts.at(group + 1);
   // Find compilation info wrapper.
   int info_pos = -1;
   for (int i = start; i < end; i++) {
-    if (object_at(i) == info_wrapper) {
+    if (object_at(i) == info) {
       info_pos = i;
       break;
     }
   }
   if (info_pos == -1) return;  // Not found.
   int gap = info_pos;
   // Use the last of each group to fill the gap in the previous group.
   for (int i = group; i < kGroupCount; i++) {
     int last_of_group = starts.at(i + 1) - 1;
     DCHECK(last_of_group >= gap);
     if (last_of_group == gap) continue;
     copy(last_of_group, gap);
     gap = last_of_group;
   }
   DCHECK(gap == starts.number_of_entries() - 1);
   clear_at(gap);  // Clear last gap.
   set_number_of_entries(group, end - start - 1);
 
 #ifdef DEBUG
   for (int i = start; i < end - 1; i++) {
-    DCHECK(is_code_at(i) || compilation_info_at(i) != info);
+    DCHECK(object_at(i) != info);
   }
 #endif
 }
 
 
-bool DependentCode::Contains(DependencyGroup group, Code* code) {
+bool DependentCode::Contains(DependencyGroup group, WeakCell* code_cell) {
   GroupStartIndexes starts(this);
   int start = starts.at(group);
   int end = starts.at(group + 1);
   for (int i = start; i < end; i++) {
-    if (object_at(i) == code) return true;
+    if (object_at(i) == code_cell) return true;
   }
   return false;
 }
 
 
 bool DependentCode::MarkCodeForDeoptimization(
     Isolate* isolate,
     DependentCode::DependencyGroup group) {
   DisallowHeapAllocation no_allocation_scope;
   DependentCode::GroupStartIndexes starts(this);
   int start = starts.at(group);
   int end = starts.at(group + 1);
   int code_entries = starts.number_of_entries();
   if (start == end) return false;
 
   // Mark all the code that needs to be deoptimized.
   bool marked = false;
+  bool invalidate_embedded_objects = group == kWeakCodeGroup;
   for (int i = start; i < end; i++) {
-    if (is_code_at(i)) {
-      Code* code = code_at(i);
+    Object* obj = object_at(i);
+    if (obj->IsWeakCell()) {
+      WeakCell* cell = WeakCell::cast(obj);
+      if (cell->cleared()) continue;
+      Code* code = Code::cast(cell->value());
       if (!code->marked_for_deoptimization()) {
         SetMarkedForDeoptimization(code, group);
+        if (invalidate_embedded_objects) {
+          code->InvalidateEmbeddedObjects();
+        }
         marked = true;
       }
     } else {
-      CompilationInfo* info = compilation_info_at(i);
+      DCHECK(obj->IsForeign());
+      CompilationInfo* info = reinterpret_cast<CompilationInfo*>(
+          Foreign::cast(obj)->foreign_address());
       info->AbortDueToDependencyChange();
     }
   }
   // Compact the array by moving all subsequent groups to fill in the new holes.
   for (int src = end, dst = start; src < code_entries; src++, dst++) {
     copy(src, dst);
   }
   // Now the holes are at the end of the array, zap them for heap-verifier.
   int removed = end - start;
   for (int i = code_entries - removed; i < code_entries; i++) {
     clear_at(i);
   }
   set_number_of_entries(group, 0);
   return marked;
 }
 
 
 void DependentCode::DeoptimizeDependentCodeGroup(
     Isolate* isolate,
     DependentCode::DependencyGroup group) {
   DCHECK(AllowCodeDependencyChange::IsAllowed());
   DisallowHeapAllocation no_allocation_scope;
   bool marked = MarkCodeForDeoptimization(isolate, group);
-
   if (marked) Deoptimizer::DeoptimizeMarkedCode(isolate);
 }
 
 
 void DependentCode::SetMarkedForDeoptimization(Code* code,
                                                DependencyGroup group) {
   code->set_marked_for_deoptimization(true);
   if (FLAG_trace_deopt &&
       (code->deoptimization_data() != code->GetHeap()->empty_fixed_array())) {
     DeoptimizationInputData* deopt_data =
@@ skipping 1069 matching lines @@
   }
 }
 
 
 // static
 void AllocationSite::AddDependentCompilationInfo(
     Handle<AllocationSite> site, DependentCode::DependencyGroup group,
     CompilationInfo* info) {
   Handle<DependentCode> dep(site->dependent_code());
   Handle<DependentCode> codes =
-      DependentCode::Insert(dep, group, info->object_wrapper());
+      DependentCode::InsertCompilationInfo(dep, group, info->object_wrapper());
   if (*codes != site->dependent_code()) site->set_dependent_code(*codes);
   info->dependencies(group)->Add(Handle<HeapObject>(*site), info->zone());
 }
 
 
 const char* AllocationSite::PretenureDecisionName(PretenureDecision decision) {
   switch (decision) {
     case kUndecided: return "undecided";
     case kDontTenure: return "don't tenure";
     case kMaybeTenure: return "maybe tenure";
@@ skipping 3765 matching lines @@
     Handle<HeapType> new_type = UpdatedType(cell, value);
     cell->set_type(*new_type);
   }
   return value;
 }
 
 
 // static
 void PropertyCell::AddDependentCompilationInfo(Handle<PropertyCell> cell,
                                                CompilationInfo* info) {
-  Handle<DependentCode> codes =
-      DependentCode::Insert(handle(cell->dependent_code(), info->isolate()),
-                            DependentCode::kPropertyCellChangedGroup,
-                            info->object_wrapper());
+  Handle<DependentCode> codes = DependentCode::InsertCompilationInfo(
+      handle(cell->dependent_code(), info->isolate()),
+      DependentCode::kPropertyCellChangedGroup, info->object_wrapper());
   if (*codes != cell->dependent_code()) cell->set_dependent_code(*codes);
   info->dependencies(DependentCode::kPropertyCellChangedGroup)->Add(
       cell, info->zone());
 }
 
 } }  // namespace v8::internal