[heap] Move use_lab_ to LinearAllocationArea

The new PagedNewSpace composes a PagedSpaceBase subclass
(PagedSpaceForNewSpace) to avoid a diamond inheritance since both
PagedSpaceBase and NewSpace inherit from SpaceWithLinearArea.
Both use the same LinearAllocationArea, LinearAreaOriginalData, and
AllocationCounter, but use_lab_ remained a field of SpaceWithLinearArea.
As a result, disabling inline allocations for new space only updated one
of the use_lab_ instances (the one in PagedNewSpace) while allocations
were using the other.
Moving this field to LinearAllocationArea lets both use the same field
and keep in sync.

Bug: v8:12612
Change-Id: I47eccc6444040efc3a3e5d93f6015fd2bdb611b1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3820065Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82315}

src/heap/linear-allocation-area.h

@@ -102,7 +102,10 @@ class LinearAllocationArea final {
 #endif  // DEBUG
   }
 
-  static constexpr int kSize = 3 * kSystemPointerSize;
+  static constexpr int kSize = 4 * kSystemPointerSize;
+
+  bool enabled() const { return enabled_; }
+  void SetEnabled(bool enabled) { enabled_ = enabled; }
 
  private:
   // The start of the LAB. Initially coincides with `top_`. As top is moved
@@ -113,9 +116,11 @@ class LinearAllocationArea final {
   Address top_ = kNullAddress;
   // Limit of the LAB the denotes the end of the valid range for allocation.
   Address limit_ = kNullAddress;
+
+  bool enabled_ = true;
 };
 
-static_assert(sizeof(LinearAllocationArea) == LinearAllocationArea::kSize,
+static_assert(sizeof(LinearAllocationArea) <= LinearAllocationArea::kSize,
               "LinearAllocationArea's size must be small because it "
               "is included in IsolateData.");
 

src/heap/spaces.cc

@@ -239,7 +239,7 @@ Address SpaceWithLinearArea::ComputeLimit(Address start, Address end,
                                           size_t min_size) const {
   DCHECK_GE(end - start, min_size);
 
-  if (!use_lab_) {
+  if (!allocation_info_.enabled()) {
     // LABs are disabled, so we fit the requested area exactly.
     return start + min_size;
   }
@@ -267,17 +267,17 @@ Address SpaceWithLinearArea::ComputeLimit(Address start, Address end,
 }
 
 void SpaceWithLinearArea::DisableInlineAllocation() {
-  if (!use_lab_) return;
+  if (!allocation_info_.enabled()) return;
 
-  use_lab_ = false;
+  allocation_info_.SetEnabled(false);
   FreeLinearAllocationArea();
   UpdateInlineAllocationLimit(0);
 }
 
 void SpaceWithLinearArea::EnableInlineAllocation() {
-  if (use_lab_) return;
+  if (allocation_info_.enabled()) return;
 
-  use_lab_ = true;
+  allocation_info_.SetEnabled(true);
   AdvanceAllocationObservers();
   UpdateInlineAllocationLimit(0);
 }

src/heap/spaces.h

@@ -561,7 +561,7 @@ class SpaceWithLinearArea : public Space {
 
   void DisableInlineAllocation();
   void EnableInlineAllocation();
-  bool IsInlineAllocationEnabled() const { return use_lab_; }
+  bool IsInlineAllocationEnabled() const { return allocation_info_.enabled(); }
 
   void PrintAllocationsOrigins() const;
 
@@ -635,8 +635,6 @@ class SpaceWithLinearArea : public Space {
   LinearAllocationArea& allocation_info_;
   LinearAreaOriginalData& linear_area_original_data_;
 
-  bool use_lab_ = true;
-
   size_t allocations_origins_[static_cast<int>(
       AllocationOrigin::kNumberOfAllocationOrigins)] = {0};
 };