Made zone segments aligned in memory and included a pointer to the zone in the header. Larger objec…

src/zone.h

Index: src/zone.h
diff --git a/src/zone.h b/src/zone.h
index 29055cb70d053547d44091cdfaf420e0f6736e2d..94eeff3c376ee4f8a3fabe33f4738ad9a0b86dfe 100644
--- a/src/zone.h
+++ b/src/zone.h
@@ -10,6 +10,7 @@
 #include "src/base/accounting-allocator.h"
 #include "src/base/hashmap.h"
 #include "src/base/logging.h"
+#include "src/base/platform/platform.h"
 #include "src/globals.h"
 #include "src/list.h"
 #include "src/splay-tree.h"
@@ -34,6 +35,9 @@ class Segment;
 // Note: The implementation is inherently not thread safe. Do not use
 // from multi-threaded code.
 class Zone final {
+  friend class ZoneObject;
+  friend class Segment;

[jochen (gone - plz use gerrit), 2016/09/01 12:04:52]

nit. please move those declarations down to the private: section
https://google.github.io/styleguide/cppguide.html#Declaration_Order

[heimbuef, 2016/09/05 12:38:14]

Acknowledged.

+
  public:
   explicit Zone(base::AccountingAllocator* allocator);
   ~Zone();
@@ -66,6 +70,10 @@ class Zone final {
 
   base::AccountingAllocator* allocator() const { return allocator_; }
 
+  // Returns the zone the pointer belongs to. Only works in case the pointer
+  // actually lies within a zone segment.
+  static Zone* GetZoneFromPointer(const void* ptr);
+
  private:
   // All pointers returned from New() have this alignment.  In addition, if the
   // object being allocated has a size that is divisible by 8 then its alignment
@@ -83,12 +91,24 @@ class Zone final {
   // Never allocate segments larger than this size in bytes.
   static const size_t kMaximumSegmentSize = 1 * MB;
 
+  static const uint8_t kSegmentAlignmentBits = 20;
+
+  // Always align new segments to this size
+  static const size_t kSegmentAlignmentSize = 1 << kSegmentAlignmentBits;
+
+  static const size_t kSegmentAlignmentMask =
+      ~((1 << kSegmentAlignmentBits) - 1);
+
+  STATIC_ASSERT(kMaximumSegmentSize <= kSegmentAlignmentSize);
+
   // Never keep segments larger than this size in bytes around.
   static const size_t kMaximumKeptSegmentSize = 64 * KB;
 
   // Report zone excess when allocation exceeds this limit.
   static const size_t kExcessLimit = 256 * MB;
 
+  static Segment* GetZoneSegmentFromPointer(const void* ptr);
+
   // The number of bytes allocated in this zone so far.
   size_t allocation_size_;
 
@@ -97,18 +117,14 @@ class Zone final {
   // the zone.
   size_t segment_bytes_allocated_;
 
-  // Expand the Zone to hold at least 'size' more bytes and allocate
-  // the bytes. Returns the address of the newly allocated chunk of
-  // memory in the Zone. Should only be called if there isn't enough
-  // room in the Zone already.
-  Address NewExpand(size_t size);
+  Address NewNormalSegment(size_t size);
 
-  // Creates a new segment, sets it size, and pushes it to the front
-  // of the segment chain. Returns the new segment.
-  inline Segment* NewSegment(size_t size);
+  Address NewLargeObjectSegment(size_t size);
 
-  // Deletes the given segment. Does not touch the segment chain.
-  inline void DeleteSegment(Segment* segment, size_t size);
+  size_t CalculateSegmentSize(const size_t requested);
+
+  // Creates a new segment, initializes it. Returns the new segment.
+  inline Segment* NewSegment(size_t size);
 
   // The free region in the current (front) segment is represented as
   // the half-open interval [position, limit). The 'position' variable
@@ -121,7 +137,6 @@ class Zone final {
   Segment* segment_head_;
 };
 
-
 // ZoneObject is an abstraction that helps define classes of objects
 // allocated in the Zone. Use it as a base class; see ast.h.
 class ZoneObject {
@@ -129,6 +144,8 @@ class ZoneObject {
   // Allocate a new ZoneObject of 'size' bytes in the Zone.
   void* operator new(size_t size, Zone* zone) { return zone->New(size); }
 
+  Zone* zone() const { return Zone::GetZoneFromPointer(this); }
+
   // Ideally, the delete operator should be private instead of
   // public, but unfortunately the compiler sometimes synthesizes
   // (unused) destructors for classes derived from ZoneObject, which
@@ -179,8 +196,9 @@ class ZoneList final : public List<T, ZoneAllocationPolicy> {
  public:
   // Construct a new ZoneList with the given capacity; the length is
   // always zero. The capacity must be non-negative.
+  // The lists storage will be placed in the given zone.
   ZoneList(int capacity, Zone* zone)
-      : List<T, ZoneAllocationPolicy>(capacity, ZoneAllocationPolicy(zone)) { }
+      : List<T, ZoneAllocationPolicy>(capacity, ZoneAllocationPolicy(zone)) {}
 
   void* operator new(size_t size, Zone* zone) { return zone->New(size); }
 
@@ -191,33 +209,53 @@ class ZoneList final : public List<T, ZoneAllocationPolicy> {
     AddAll(other, zone);
   }
 
-  // We add some convenience wrappers so that we can pass in a Zone
-  // instead of a (less convenient) ZoneAllocationPolicy.
   void Add(const T& element, Zone* zone) {
+    DCHECK_IMPLIES(this->has_storage_zone(), this->storage_zone() == zone);
     List<T, ZoneAllocationPolicy>::Add(element, ZoneAllocationPolicy(zone));
   }
+
   void AddAll(const List<T, ZoneAllocationPolicy>& other, Zone* zone) {
+    DCHECK_IMPLIES(this->has_storage_zone(), this->storage_zone() == zone);
     List<T, ZoneAllocationPolicy>::AddAll(other, ZoneAllocationPolicy(zone));
   }
+
   void AddAll(const Vector<T>& other, Zone* zone) {
+    DCHECK_IMPLIES(this->has_storage_zone(), this->storage_zone() == zone);
     List<T, ZoneAllocationPolicy>::AddAll(other, ZoneAllocationPolicy(zone));
   }
+
   void InsertAt(int index, const T& element, Zone* zone) {
+    DCHECK_IMPLIES(this->has_storage_zone(), this->storage_zone() == zone);
     List<T, ZoneAllocationPolicy>::InsertAt(index, element,
                                             ZoneAllocationPolicy(zone));
   }
+
   Vector<T> AddBlock(T value, int count, Zone* zone) {
+    DCHECK_IMPLIES(this->has_storage_zone(), this->storage_zone() == zone);
     return List<T, ZoneAllocationPolicy>::AddBlock(value, count,
                                                    ZoneAllocationPolicy(zone));
   }
+
   void Allocate(int length, Zone* zone) {
+    DCHECK_IMPLIES(this->has_storage_zone(), this->storage_zone() == zone);
     List<T, ZoneAllocationPolicy>::Allocate(length, ZoneAllocationPolicy(zone));
   }
+
   void Initialize(int capacity, Zone* zone) {
+    DCHECK_IMPLIES(this->has_storage_zone(), this->storage_zone() == zone);
     List<T, ZoneAllocationPolicy>::Initialize(capacity,
                                               ZoneAllocationPolicy(zone));
   }
 
+  bool has_storage_zone() const { return this->capacity() > 0; }
+
+  // Returns the zone the storage is located in
+  Zone* storage_zone() const {
+    DCHECK(this->has_storage_zone());
+    // ZoneList storage lives in a zone, so this works.
+    return Zone::GetZoneFromPointer(this->data());
+  }
+
   void operator delete(void* pointer) { UNREACHABLE(); }
   void operator delete(void* pointer, Zone* zone) { UNREACHABLE(); }
 };