Revert of [heap] Remove border page

src/heap/spaces.cc

Index: src/heap/spaces.cc
diff --git a/src/heap/spaces.cc b/src/heap/spaces.cc
index 525e78461edf19e05f16d50e2b8ff6f25879df4d..daaf9ad0a0636ef463421d854497bc84687d2eec 100644
--- a/src/heap/spaces.cc
+++ b/src/heap/spaces.cc
@@ -1489,9 +1489,8 @@ void PagedSpace::Verify(ObjectVisitor* visitor) {
 
 bool NewSpace::SetUp(int initial_semispace_capacity,
                      int maximum_semispace_capacity) {
-  DCHECK_LE(initial_semispace_capacity, maximum_semispace_capacity);
+  DCHECK(initial_semispace_capacity <= maximum_semispace_capacity);
   DCHECK(base::bits::IsPowerOfTwo32(maximum_semispace_capacity));
-  DCHECK_GE(initial_semispace_capacity, 2 * Page::kPageSize);
 
   to_space_.SetUp(initial_semispace_capacity, maximum_semispace_capacity);
   from_space_.SetUp(initial_semispace_capacity, maximum_semispace_capacity);
@@ -1592,16 +1591,8 @@ bool SemiSpace::EnsureCurrentCapacity() {
       current_page = current_page->next_page();
       if (actual_pages > expected_pages) {
         Page* to_remove = current_page->prev_page();
-        if (to_remove == current_page_) {
-          // Corner case: All pages have been moved within new space. We are
-          // removing the page that contains the top pointer and need to set
-          // it to the end of the intermediate generation.
-          NewSpace* new_space = heap()->new_space();
-          CHECK_EQ(new_space->top(), current_page_->area_start());
-          current_page_ = to_remove->prev_page();
-          CHECK(current_page_->InIntermediateGeneration());
-          new_space->SetAllocationInfo(page_high(), page_high());
-        }
+        // Make sure we don't overtake the actual top pointer.
+        CHECK_NE(to_remove, current_page_);
         to_remove->Unlink();
         heap()->memory_allocator()->Free<MemoryAllocator::kPooledAndQueue>(
             to_remove);
@@ -1931,6 +1922,9 @@ bool SemiSpace::Commit() {
   }
   Reset();
   AccountCommitted(current_capacity_);
+  if (age_mark_ == nullptr) {
+    age_mark_ = first_page()->area_start();
+  }
   committed_ = true;
   return true;
 }
@@ -2042,7 +2036,7 @@ void SemiSpace::FixPagesFlags(intptr_t flags, intptr_t mask) {
     if (id_ == kToSpace) {
       page->ClearFlag(MemoryChunk::IN_FROM_SPACE);
       page->SetFlag(MemoryChunk::IN_TO_SPACE);
-      page->ClearFlag(MemoryChunk::IN_INTERMEDIATE_GENERATION);
+      page->ClearFlag(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK);
       page->ResetLiveBytes();
     } else {
       page->SetFlag(MemoryChunk::IN_FROM_SPACE);
@@ -2085,6 +2079,7 @@ void SemiSpace::Swap(SemiSpace* from, SemiSpace* to) {
   std::swap(from->current_capacity_, to->current_capacity_);
   std::swap(from->maximum_capacity_, to->maximum_capacity_);
   std::swap(from->minimum_capacity_, to->minimum_capacity_);
+  std::swap(from->age_mark_, to->age_mark_);
   std::swap(from->committed_, to->committed_);
   std::swap(from->anchor_, to->anchor_);
   std::swap(from->current_page_, to->current_page_);
@@ -2093,37 +2088,12 @@ void SemiSpace::Swap(SemiSpace* from, SemiSpace* to) {
   from->FixPagesFlags(0, 0);
 }
 
-void NewSpace::SealIntermediateGeneration() {
-  fragmentation_in_intermediate_generation_ = 0;
-  const Address mark = top();
-
-  if (mark == to_space_.space_start()) {
-    // Do not mark any pages as being part of the intermediate generation if no
-    // objects got moved.
-    return;
-  }
-
-  for (Page* p : NewSpacePageRange(to_space_.space_start(), mark)) {
-    p->SetFlag(MemoryChunk::IN_INTERMEDIATE_GENERATION);
-  }
-
-  Page* p = Page::FromAllocationAreaAddress(mark);
-  if (mark < p->area_end()) {
-    heap()->CreateFillerObjectAt(mark, static_cast<int>(p->area_end() - mark),
-                                 ClearRecordedSlots::kNo);
-    fragmentation_in_intermediate_generation_ =
-        static_cast<size_t>(p->area_end() - mark);
-    DCHECK_EQ(to_space_.current_page(), p);
-    if (to_space_.AdvancePage()) {
-      UpdateAllocationInfo();
-    } else {
-      allocation_info_.Reset(to_space_.page_high(), to_space_.page_high());
-    }
-  }
-  if (FLAG_trace_gc_verbose) {
-    PrintIsolate(heap()->isolate(),
-                 "Sealing intermediate generation: bytes_lost=%zu\n",
-                 fragmentation_in_intermediate_generation_);
+void SemiSpace::set_age_mark(Address mark) {
+  DCHECK_EQ(Page::FromAllocationAreaAddress(mark)->owner(), this);
+  age_mark_ = mark;
+  // Mark all pages up to the one containing mark.
+  for (Page* p : NewSpacePageRange(space_start(), mark)) {
+    p->SetFlag(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK);
   }
 }