[heap] Add page evacuation mode for new->new

src/heap/spaces.cc

 // Copyright 2011 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/spaces.h"
 
 #include "src/base/bits.h"
 #include "src/base/platform/platform.h"
 #include "src/base/platform/semaphore.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 1873 matching lines @@
   new_page->SetFlags(old_page->GetFlags(), Page::kCopyAllFlags);
   new_page->set_next_page(old_page->next_page());
   new_page->set_prev_page(old_page->prev_page());
   old_page->next_page()->set_prev_page(new_page);
   old_page->prev_page()->set_next_page(new_page);
   heap()->CreateFillerObjectAt(new_page->area_start(), new_page->area_size(),
                                ClearRecordedSlots::kNo);
   return true;
 }
 
+void SemiSpace::PrependPage(Page* page) {
+  // Remove page at the end.
+  Page* replacement_page = anchor()->prev_page();
+  replacement_page->next_page()->set_prev_page(replacement_page->prev_page());
+  replacement_page->prev_page()->set_next_page(replacement_page->next_page());
+  DCHECK_NE(current_page(), replacement_page);
+
+  SemiSpace* old_semi_space = reinterpret_cast<SemiSpace*>(page->owner());
+  if (page == old_semi_space->current_page()) {
+    old_semi_space->current_page_ = replacement_page;
+  }
+
+  // Replace it.
+  replacement_page->set_owner(page->owner());
+  replacement_page->SetFlags(page->GetFlags(), Page::kCopyAllFlags);
+  page->next_page()->set_prev_page(replacement_page);
+  page->prev_page()->set_next_page(replacement_page);
+  replacement_page->set_prev_page(page->prev_page());
+  replacement_page->set_next_page(page->next_page());
+  page->set_next_page(nullptr);
+  page->set_prev_page(nullptr);
+  page->SetFlags(current_page()->GetFlags(), Page::kCopyAllFlags);
+  page->set_owner(this);
+  page->InsertAfter(anchor());
+}
+
 void SemiSpace::Swap(SemiSpace* from, SemiSpace* to) {
   // We won't be swapping semispaces without data in them.
   DCHECK_NE(from->anchor_.next_page(), &from->anchor_);
   DCHECK_NE(to->anchor_.next_page(), &to->anchor_);
 
   intptr_t saved_to_space_flags = to->current_page()->GetFlags();
 
   // We swap all properties but id_.
   std::swap(from->current_capacity_, to->current_capacity_);
   std::swap(from->maximum_capacity_, to->maximum_capacity_);
@@ skipping 1318 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 }  // namespace internal
 }  // namespace v8