[Memory] Don't heap allocate instances of base::VirtualMemory.

- Changes some instance fields from VM pointers to VM.  
- Changes some comments to correctly describe code.  

Bug: v8:6635
Change-Id: I9ec93ef0b09d541c966caa6482c5832cd6b1e149
Reviewed-on: https://chromium-review.googlesource.com/584931
Commit-Queue: Bill Budge <bbudge@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46880}

src/base/platform/platform.h

@@ -285,11 +285,10 @@ class V8_BASE_EXPORT OS {
   DISALLOW_IMPLICIT_CONSTRUCTORS(OS);
 };
 
-
 // Represents and controls an area of reserved memory.
 // Control of the reserved memory can be assigned to another VirtualMemory
-// object by assignment or copy-contructing. This removes the reserved memory
-// from the original object.
+// object by calling TakeControl. This removes the reserved memory from the
+// 'from' instance.
 class V8_BASE_EXPORT VirtualMemory {
  public:
   // Empty VirtualMemory object, controlling no reserved memory.

src/heap/sequential-marking-deque.cc

@@ -13,15 +13,17 @@ namespace v8 {
 namespace internal {
 
 void SequentialMarkingDeque::SetUp() {
-  backing_store_ =
-      new base::VirtualMemory(kMaxSize, heap_->GetRandomMmapAddr());
-  backing_store_committed_size_ = 0;
-  if (backing_store_ == nullptr) {
+  base::VirtualMemory reservation(kMaxSize, heap_->GetRandomMmapAddr());
+  if (!reservation.IsReserved()) {
     V8::FatalProcessOutOfMemory("SequentialMarkingDeque::SetUp");
   }
+  backing_store_committed_size_ = 0;
+  backing_store_.TakeControl(&reservation);
 }
 
-void SequentialMarkingDeque::TearDown() { delete backing_store_; }
+void SequentialMarkingDeque::TearDown() {
+  if (backing_store_.IsReserved()) backing_store_.Release();
+}
 
 void SequentialMarkingDeque::StartUsing() {
   base::LockGuard<base::Mutex> guard(&mutex_);
@@ -32,7 +34,7 @@ void SequentialMarkingDeque::StartUsing() {
   }
   in_use_ = true;
   EnsureCommitted();
-  array_ = reinterpret_cast<HeapObject**>(backing_store_->address());
+  array_ = reinterpret_cast<HeapObject**>(backing_store_.address());
   size_t size = FLAG_force_marking_deque_overflows
                     ? 64 * kPointerSize
                     : backing_store_committed_size_;
@@ -64,8 +66,8 @@ void SequentialMarkingDeque::Clear() {
 
 void SequentialMarkingDeque::Uncommit() {
   DCHECK(!in_use_);
-  bool success = backing_store_->Uncommit(backing_store_->address(),
-                                          backing_store_committed_size_);
+  bool success = backing_store_.Uncommit(backing_store_.address(),
+                                         backing_store_committed_size_);
   backing_store_committed_size_ = 0;
   CHECK(success);
 }
@@ -75,7 +77,7 @@ void SequentialMarkingDeque::EnsureCommitted() {
   if (backing_store_committed_size_ > 0) return;
 
   for (size_t size = kMaxSize; size >= kMinSize; size /= 2) {
-    if (backing_store_->Commit(backing_store_->address(), size, false)) {
+    if (backing_store_.Commit(backing_store_.address(), size, false)) {
       backing_store_committed_size_ = size;
       break;
     }

src/heap/sequential-marking-deque.h

@@ -23,8 +23,7 @@ class HeapObject;
 class SequentialMarkingDeque {
  public:
   explicit SequentialMarkingDeque(Heap* heap)
-      : backing_store_(nullptr),
-        backing_store_committed_size_(0),
+      : backing_store_committed_size_(0),
         array_(nullptr),
         top_(0),
         bottom_(0),
@@ -132,7 +131,7 @@ class SequentialMarkingDeque {
 
   base::Mutex mutex_;
 
-  base::VirtualMemory* backing_store_;
+  base::VirtualMemory backing_store_;
   size_t backing_store_committed_size_;
   HeapObject** array_;
   // array_[(top - 1) & mask_] is the top element in the deque.  The Deque is

src/heap/spaces.cc

@@ -88,17 +88,14 @@ PauseAllocationObserversScope::~PauseAllocationObserversScope() {
 // -----------------------------------------------------------------------------
 // CodeRange
 
-
 CodeRange::CodeRange(Isolate* isolate)
     : isolate_(isolate),
-      code_range_(NULL),
       free_list_(0),
       allocation_list_(0),
       current_allocation_block_index_(0) {}
 
-
 bool CodeRange::SetUp(size_t requested) {
-  DCHECK(code_range_ == NULL);
+  DCHECK(!virtual_memory_.IsReserved());
 
   if (requested == 0) {
     // When a target requires the code range feature, we put all code objects
@@ -122,38 +119,31 @@ bool CodeRange::SetUp(size_t requested) {
 
   DCHECK(!kRequiresCodeRange || requested <= kMaximalCodeRangeSize);
 
-  code_range_ = new base::VirtualMemory(
+  base::VirtualMemory reservation(
       requested,
       Max(kCodeRangeAreaAlignment,
           static_cast<size_t>(base::OS::AllocateAlignment())),
       base::OS::GetRandomMmapAddr());
-  CHECK(code_range_ != NULL);
-  if (!code_range_->IsReserved()) {
-    delete code_range_;
-    code_range_ = NULL;
-    return false;
-  }
+  if (!reservation.IsReserved()) return false;
 
   // We are sure that we have mapped a block of requested addresses.
-  DCHECK(code_range_->size() == requested);
-  Address base = reinterpret_cast<Address>(code_range_->address());
+  DCHECK(reservation.size() == requested);
+  Address base = reinterpret_cast<Address>(reservation.address());
 
   // On some platforms, specifically Win64, we need to reserve some pages at
   // the beginning of an executable space.
   if (reserved_area > 0) {
-    if (!code_range_->Commit(base, reserved_area, true)) {
-      delete code_range_;
-      code_range_ = NULL;
-      return false;
-    }
+    if (!reservation.Commit(base, reserved_area, true)) return false;
+
     base += reserved_area;
   }
   Address aligned_base = RoundUp(base, MemoryChunk::kAlignment);
-  size_t size = code_range_->size() - (aligned_base - base) - reserved_area;
+  size_t size = reservation.size() - (aligned_base - base) - reserved_area;
   allocation_list_.Add(FreeBlock(aligned_base, size));
   current_allocation_block_index_ = 0;
 
-  LOG(isolate_, NewEvent("CodeRange", code_range_->address(), requested));
+  LOG(isolate_, NewEvent("CodeRange", reservation.address(), requested));
+  virtual_memory_.TakeControl(&reservation);
   return true;
 }
 
@@ -224,7 +214,7 @@ Address CodeRange::AllocateRawMemory(const size_t requested_size,
   DCHECK(*allocated <= current.size);
   DCHECK(IsAddressAligned(current.start, MemoryChunk::kAlignment));
   if (!isolate_->heap()->memory_allocator()->CommitExecutableMemory(
-          code_range_, current.start, commit_size, *allocated)) {
+          &virtual_memory_, current.start, commit_size, *allocated)) {
     *allocated = 0;
     ReleaseBlock(&current);
     return NULL;
@@ -240,7 +230,7 @@ bool CodeRange::CommitRawMemory(Address start, size_t length) {
 
 
 bool CodeRange::UncommitRawMemory(Address start, size_t length) {
-  return code_range_->Uncommit(start, length);
+  return virtual_memory_.Uncommit(start, length);
 }
 
 
@@ -248,13 +238,12 @@ void CodeRange::FreeRawMemory(Address address, size_t length) {
   DCHECK(IsAddressAligned(address, MemoryChunk::kAlignment));
   base::LockGuard<base::Mutex> guard(&code_range_mutex_);
   free_list_.Add(FreeBlock(address, length));
-  code_range_->Uncommit(address, length);
+  virtual_memory_.Uncommit(address, length);
 }
 
 
 void CodeRange::TearDown() {
-  delete code_range_;  // Frees all memory in the virtual memory range.
-  code_range_ = NULL;
+  if (virtual_memory_.IsReserved()) virtual_memory_.Release();
   base::LockGuard<base::Mutex> guard(&code_range_mutex_);
   free_list_.Free();
   allocation_list_.Free();

src/heap/spaces.h

@@ -1037,19 +1037,19 @@ class CodeRange {
   // Returns false on failure.
   bool SetUp(size_t requested_size);
 
-  bool valid() { return code_range_ != NULL; }
+  bool valid() { return virtual_memory_.IsReserved(); }
   Address start() {
     DCHECK(valid());
-    return static_cast<Address>(code_range_->address());
+    return static_cast<Address>(virtual_memory_.address());
   }
   size_t size() {
     DCHECK(valid());
-    return code_range_->size();
+    return virtual_memory_.size();
   }
   bool contains(Address address) {
     if (!valid()) return false;
-    Address start = static_cast<Address>(code_range_->address());
-    return start <= address && address < start + code_range_->size();
+    Address start = static_cast<Address>(virtual_memory_.address());
+    return start <= address && address < start + virtual_memory_.size();
   }
 
   // Allocates a chunk of memory from the large-object portion of
@@ -1099,7 +1099,7 @@ class CodeRange {
   Isolate* isolate_;
 
   // The reserved range of virtual memory that all code objects are put in.
-  base::VirtualMemory* code_range_;
+  base::VirtualMemory virtual_memory_;
 
   // The global mutex guards free_list_ and allocation_list_ as GC threads may
   // access both lists concurrently to the main thread.

src/heap/store-buffer.cc

@@ -16,11 +16,7 @@ namespace v8 {
 namespace internal {
 
 StoreBuffer::StoreBuffer(Heap* heap)
-    : heap_(heap),
-      top_(nullptr),
-      current_(0),
-      mode_(NOT_IN_GC),
-      virtual_memory_(nullptr) {
+    : heap_(heap), top_(nullptr), current_(0), mode_(NOT_IN_GC) {
   for (int i = 0; i < kStoreBuffers; i++) {
     start_[i] = nullptr;
     limit_[i] = nullptr;
@@ -35,10 +31,9 @@ void StoreBuffer::SetUp() {
   // Allocate 3x the buffer size, so that we can start the new store buffer
   // aligned to 2x the size.  This lets us use a bit test to detect the end of
   // the area.
-  virtual_memory_ =
-      new base::VirtualMemory(kStoreBufferSize * 3, heap_->GetRandomMmapAddr());
-  uintptr_t start_as_int =
-      reinterpret_cast<uintptr_t>(virtual_memory_->address());
+  base::VirtualMemory reservation(kStoreBufferSize * 3,
+                                  heap_->GetRandomMmapAddr());
+  uintptr_t start_as_int = reinterpret_cast<uintptr_t>(reservation.address());
   start_[0] =
       reinterpret_cast<Address*>(RoundUp(start_as_int, kStoreBufferSize));
   limit_[0] = start_[0] + (kStoreBufferSize / kPointerSize);
@@ -46,30 +41,30 @@ void StoreBuffer::SetUp() {
   limit_[1] = start_[1] + (kStoreBufferSize / kPointerSize);
 
   Address* vm_limit = reinterpret_cast<Address*>(
-      reinterpret_cast<char*>(virtual_memory_->address()) +
-      virtual_memory_->size());
+      reinterpret_cast<char*>(reservation.address()) + reservation.size());
 
   USE(vm_limit);
   for (int i = 0; i < kStoreBuffers; i++) {
-    DCHECK(reinterpret_cast<Address>(start_[i]) >= virtual_memory_->address());
-    DCHECK(reinterpret_cast<Address>(limit_[i]) >= virtual_memory_->address());
+    DCHECK(reinterpret_cast<Address>(start_[i]) >= reservation.address());
+    DCHECK(reinterpret_cast<Address>(limit_[i]) >= reservation.address());
     DCHECK(start_[i] <= vm_limit);
     DCHECK(limit_[i] <= vm_limit);
     DCHECK((reinterpret_cast<uintptr_t>(limit_[i]) & kStoreBufferMask) == 0);
   }
 
-  if (!virtual_memory_->Commit(reinterpret_cast<Address>(start_[0]),
-                               kStoreBufferSize * kStoreBuffers,
-                               false)) {  // Not executable.
+  if (!reservation.Commit(reinterpret_cast<Address>(start_[0]),
+                          kStoreBufferSize * kStoreBuffers,
+                          false)) {  // Not executable.
     V8::FatalProcessOutOfMemory("StoreBuffer::SetUp");
   }
   current_ = 0;
   top_ = start_[current_];
+  virtual_memory_.TakeControl(&reservation);
 }
 
 
 void StoreBuffer::TearDown() {
-  delete virtual_memory_;
+  if (virtual_memory_.IsReserved()) virtual_memory_.Release();
   top_ = nullptr;
   for (int i = 0; i < kStoreBuffers; i++) {
     start_[i] = nullptr;

src/heap/store-buffer.h

@@ -208,7 +208,7 @@ class StoreBuffer {
   // IN_GC mode.
   StoreBufferMode mode_;
 
-  base::VirtualMemory* virtual_memory_;
+  base::VirtualMemory virtual_memory_;
 
   // Callbacks are more efficient than reading out the gc state for every
   // store buffer operation.