Embedded constant pools.

src/heap/mark-compact.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/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 2809 matching lines @@
 
     if (compacting_ && dst->IsJSFunction()) {
       Address code_entry_slot = dst_addr + JSFunction::kCodeEntryOffset;
       Address code_entry = Memory::Address_at(code_entry_slot);
 
       if (Page::FromAddress(code_entry)->IsEvacuationCandidate()) {
         SlotsBuffer::AddTo(&slots_buffer_allocator_, &migration_slots_buffer_,
                            SlotsBuffer::CODE_ENTRY_SLOT, code_entry_slot,
                            SlotsBuffer::IGNORE_OVERFLOW);
       }
-    } else if (dst->IsConstantPoolArray()) {
-      // We special case ConstantPoolArrays since they could contain integers
-      // value entries which look like tagged pointers.
-      // TODO(mstarzinger): restructure this code to avoid this special-casing.
-      ConstantPoolArray* array = ConstantPoolArray::cast(dst);
-      ConstantPoolArray::Iterator code_iter(array, ConstantPoolArray::CODE_PTR);
-      while (!code_iter.is_finished()) {
-        Address code_entry_slot =
-            dst_addr + array->OffsetOfElementAt(code_iter.next_index());
-        Address code_entry = Memory::Address_at(code_entry_slot);
-
-        if (Page::FromAddress(code_entry)->IsEvacuationCandidate()) {
-          SlotsBuffer::AddTo(&slots_buffer_allocator_, &migration_slots_buffer_,
-                             SlotsBuffer::CODE_ENTRY_SLOT, code_entry_slot,
-                             SlotsBuffer::IGNORE_OVERFLOW);
-        }
-      }
-      ConstantPoolArray::Iterator heap_iter(array, ConstantPoolArray::HEAP_PTR);
-      while (!heap_iter.is_finished()) {
-        Address heap_slot =
-            dst_addr + array->OffsetOfElementAt(heap_iter.next_index());
-        Object* value = Memory::Object_at(heap_slot);
-        RecordMigratedSlot(value, heap_slot);
-      }
     }
   } else if (dest == CODE_SPACE) {
     PROFILE(isolate(), CodeMoveEvent(src_addr, dst_addr));
     heap()->MoveBlock(dst_addr, src_addr, size);
     SlotsBuffer::AddTo(&slots_buffer_allocator_, &migration_slots_buffer_,
                        SlotsBuffer::RELOCATED_CODE_OBJECT, dst_addr,
                        SlotsBuffer::IGNORE_OVERFLOW);
     Code::cast(dst)->Relocate(dst_addr - src_addr);
   } else {
     DCHECK(dest == NEW_SPACE);
@@ skipping 596 matching lines @@
     case SlotsBuffer::JS_RETURN_SLOT: {
       RelocInfo rinfo(addr, RelocInfo::JS_RETURN, 0, NULL);
       if (rinfo.IsPatchedReturnSequence()) rinfo.Visit(isolate, v);
       break;
     }
     case SlotsBuffer::EMBEDDED_OBJECT_SLOT: {
       RelocInfo rinfo(addr, RelocInfo::EMBEDDED_OBJECT, 0, NULL);
       rinfo.Visit(isolate, v);
       break;
     }
+    case SlotsBuffer::OBJECT_SLOT: {
+      v->VisitPointer(reinterpret_cast<Object**>(addr));
+      break;
+    }
     default:
       UNREACHABLE();
       break;
   }
 }
 
 
 enum SweepingMode { SWEEP_ONLY, SWEEP_AND_VISIT_LIVE_OBJECTS };
 
 
@@ skipping 1149 matching lines @@
   return SlotsBuffer::NUMBER_OF_SLOT_TYPES;
 }
 
 
 void MarkCompactCollector::RecordRelocSlot(RelocInfo* rinfo, Object* target) {
   Page* target_page = Page::FromAddress(reinterpret_cast<Address>(target));
   RelocInfo::Mode rmode = rinfo->rmode();
   if (target_page->IsEvacuationCandidate() &&
       (rinfo->host() == NULL ||
        !ShouldSkipEvacuationSlotRecording(rinfo->host()))) {
+    Address addr = rinfo->pc();
+    SlotsBuffer::SlotType slot_type = SlotTypeForRMode(rmode);
+    if (rinfo->IsInConstantPool()) {
+      addr = rinfo->constant_pool_entry_address();
+      if (RelocInfo::IsCodeTarget(rmode)) {
+        slot_type = SlotsBuffer::CODE_ENTRY_SLOT;
+      } else {
+        DCHECK(RelocInfo::IsEmbeddedObject(rmode));
+        slot_type = SlotsBuffer::OBJECT_SLOT;

[rmcilroy, 2015/05/20 14:32:11]

why are these changes to add OBJECT_SLOT to the mark compact collector required?
Can they be made in a different CL?

[MTBrandyberry, 2015/05/20 22:28:22]

This is required. 
https://chromium.googlesource.com/v8/v8/+/7ad9980d995b0381046ee8677861491ef6d...
effectively broke ool/embedded constant pools.  I believe this restores
functionality without violating the intent of that change.

[rmcilroy, 2015/06/01 09:52:08]

ishell@: Could you have a quick look at this change an check it won't cause
issues with slot filtering again.

[Igor Sheludko, 2015/06/01 10:42:30]

Sgtm. Since we have a typed slot here the slots filtering should not be
affected.

+      }
+    }
     bool success = SlotsBuffer::AddTo(
         &slots_buffer_allocator_, target_page->slots_buffer_address(),
-        SlotTypeForRMode(rmode), rinfo->pc(), SlotsBuffer::FAIL_ON_OVERFLOW);
+        slot_type, addr, SlotsBuffer::FAIL_ON_OVERFLOW);
     if (!success) {
       EvictPopularEvacuationCandidate(target_page);
     }
   }
 }
 
 
 void MarkCompactCollector::EvictPopularEvacuationCandidate(Page* page) {
   if (FLAG_trace_fragmentation) {
     PrintF("Page %p is too popular. Disabling evacuation.\n",
@@ skipping 105 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }
 }  // namespace v8::internal