Add ability to disable inline bump-pointer allocation.

src/spaces.cc

Index: src/spaces.cc
diff --git a/src/spaces.cc b/src/spaces.cc
index 1e0d9bc7f26e266f50ac55e7c9f81bcb481401c6..ee19a02967d69b2b21551b16a2f46cd5243df2eb 100644
--- a/src/spaces.cc
+++ b/src/spaces.cc
@@ -1350,7 +1350,6 @@ void NewSpace::Shrink() {
       }
     }
   }
-  allocation_info_.set_limit(to_space_.page_high());
   ASSERT_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
 }
 
@@ -1359,14 +1358,7 @@ void NewSpace::UpdateAllocationInfo() {
   MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
   allocation_info_.set_top(to_space_.page_low());
   allocation_info_.set_limit(to_space_.page_high());
-
-  // Lower limit during incremental marking.
-  if (heap()->incremental_marking()->IsMarking() &&
-      inline_allocation_limit_step() != 0) {
-    Address new_limit =
-        allocation_info_.top() + inline_allocation_limit_step();
-    allocation_info_.set_limit(Min(new_limit, allocation_info_.limit()));
-  }
+  UpdateInlineAllocationLimit(0);
   ASSERT_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
 }
 
@@ -1383,6 +1375,26 @@ void NewSpace::ResetAllocationInfo() {
 }
 
 
+void NewSpace::UpdateInlineAllocationLimit(int size_in_bytes) {
+  if (heap()->inline_allocation_disabled()) {
+    // Lowest limit when linear allocation was disabled.
+    Address high = to_space_.page_high();
+    Address new_top = allocation_info_.top() + size_in_bytes;
+    allocation_info_.set_limit(Min(new_top, high));
+  } else if (inline_allocation_limit_step() == 0) {
+    // Normal limit is the end of the current page.
+    allocation_info_.set_limit(to_space_.page_high());
+  } else {
+    // Lower limit during incremental marking.
+    Address high = to_space_.page_high();
+    Address new_top = allocation_info_.top() + size_in_bytes;
+    Address new_limit = new_top + inline_allocation_limit_step_;
+    allocation_info_.set_limit(Min(new_limit, high));
+  }
+  ASSERT_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
+}
+
+
 bool NewSpace::AddFreshPage() {
   Address top = allocation_info_.top();
   if (NewSpacePage::IsAtStart(top)) {
@@ -1417,18 +1429,16 @@ bool NewSpace::AddFreshPage() {
 
 MaybeObject* NewSpace::SlowAllocateRaw(int size_in_bytes) {
   Address old_top = allocation_info_.top();
-  Address new_top = old_top + size_in_bytes;
   Address high = to_space_.page_high();
   if (allocation_info_.limit() < high) {
-    // Incremental marking has lowered the limit to get a
-    // chance to do a step.
-    Address new_limit = Min(
-        allocation_info_.limit() + inline_allocation_limit_step_,
-        high);
-    allocation_info_.set_limit(new_limit);
+    // Either the limit has been lowered because linear allocation was disabled
+    // or because incremental marking wants to get a chance to do a step. Set
+    // the new limit accordingly.
+    Address new_top = old_top + size_in_bytes;
     int bytes_allocated = static_cast<int>(new_top - top_on_previous_step_);
     heap()->incremental_marking()->Step(
         bytes_allocated, IncrementalMarking::GC_VIA_STACK_GUARD);
+    UpdateInlineAllocationLimit(size_in_bytes);
     top_on_previous_step_ = new_top;
     return AllocateRaw(size_in_bytes);
   } else if (AddFreshPage()) {
@@ -2374,7 +2384,7 @@ HeapObject* FreeList::Allocate(int size_in_bytes) {
   int new_node_size = 0;
   FreeListNode* new_node = FindNodeFor(size_in_bytes, &new_node_size);
   if (new_node == NULL) {
-    owner_->SetTop(NULL, NULL);
+    owner_->SetTopAndLimit(NULL, NULL);
     return NULL;
   }
 
@@ -2399,26 +2409,31 @@ HeapObject* FreeList::Allocate(int size_in_bytes) {
   // a little of this again immediately - see below.
   owner_->Allocate(new_node_size);
 
-  if (bytes_left > kThreshold &&
-      owner_->heap()->incremental_marking()->IsMarkingIncomplete() &&
-      FLAG_incremental_marking_steps) {
+  if (owner_->heap()->inline_allocation_disabled()) {
+    // Keep the linear allocation area empty if requested to do so, just
+    // return area back to the free list instead.
+    owner_->Free(new_node->address() + size_in_bytes, bytes_left);
+    ASSERT(owner_->top() == NULL && owner_->limit() == NULL);
+  } else if (bytes_left > kThreshold &&
+             owner_->heap()->incremental_marking()->IsMarkingIncomplete() &&
+             FLAG_incremental_marking_steps) {
     int linear_size = owner_->RoundSizeDownToObjectAlignment(kThreshold);
     // We don't want to give too large linear areas to the allocator while
     // incremental marking is going on, because we won't check again whether
     // we want to do another increment until the linear area is used up.
     owner_->Free(new_node->address() + size_in_bytes + linear_size,
                  new_node_size - size_in_bytes - linear_size);
-    owner_->SetTop(new_node->address() + size_in_bytes,
-                   new_node->address() + size_in_bytes + linear_size);
+    owner_->SetTopAndLimit(new_node->address() + size_in_bytes,
+                           new_node->address() + size_in_bytes + linear_size);
   } else if (bytes_left > 0) {
     // Normally we give the rest of the node to the allocator as its new
     // linear allocation area.
-    owner_->SetTop(new_node->address() + size_in_bytes,
-                   new_node->address() + new_node_size);
+    owner_->SetTopAndLimit(new_node->address() + size_in_bytes,
+                           new_node->address() + new_node_size);
   } else {
     // TODO(gc) Try not freeing linear allocation region when bytes_left
     // are zero.
-    owner_->SetTop(NULL, NULL);
+    owner_->SetTopAndLimit(NULL, NULL);
   }
 
   return new_node;
@@ -2507,11 +2522,7 @@ intptr_t FreeList::SumFreeLists() {
 void PagedSpace::PrepareForMarkCompact() {
   // We don't have a linear allocation area while sweeping.  It will be restored
   // on the first allocation after the sweep.
-  // Mark the old linear allocation area with a free space map so it can be
-  // skipped when scanning the heap.
-  int old_linear_size = static_cast<int>(limit() - top());
-  Free(top(), old_linear_size);
-  SetTop(NULL, NULL);
+  EmptyAllocationInfo();
 
   // Stop lazy sweeping and clear marking bits for unswept pages.
   if (first_unswept_page_ != NULL) {