Support for typed arrays added to Heap::RightTrimFixedArray().

BUG=chromium:472513
LOG=Y

Review URL: https://codereview.chromium.org/1058793002

Cr-Commit-Position: refs/heads/master@{#27586}

src/heap/heap.cc

@@ -3525,6 +3525,7 @@ void Heap::AdjustLiveBytes(Address address, int by, InvocationMode mode) {
 
 FixedArrayBase* Heap::LeftTrimFixedArray(FixedArrayBase* object,
                                          int elements_to_trim) {
+  DCHECK(!object->IsFixedTypedArrayBase());
   const int element_size = object->IsFixedArray() ? kPointerSize : kDoubleSize;
   const int bytes_to_trim = elements_to_trim * element_size;
   Map* map = object->map();
@@ -3580,14 +3581,30 @@ void Heap::RightTrimFixedArray<Heap::FROM_MUTATOR>(FixedArrayBase*, int);
 
 template<Heap::InvocationMode mode>
 void Heap::RightTrimFixedArray(FixedArrayBase* object, int elements_to_trim) {
-  const int element_size = object->IsFixedArray() ? kPointerSize : kDoubleSize;
-  const int bytes_to_trim = elements_to_trim * element_size;
+  const int len = object->length();
+  DCHECK(elements_to_trim < len);
+
+  int bytes_to_trim;
+  if (object->IsFixedTypedArrayBase()) {
+    InstanceType type = object->map()->instance_type();
+    bytes_to_trim =
+        FixedTypedArrayBase::TypedArraySize(type, len) -
+        FixedTypedArrayBase::TypedArraySize(type, len - elements_to_trim);
+  } else {
+    const int element_size =
+        object->IsFixedArray() ? kPointerSize : kDoubleSize;
+    bytes_to_trim = elements_to_trim * element_size;
+  }
 
   // For now this trick is only applied to objects in new and paged space.
   DCHECK(object->map() != fixed_cow_array_map());
 
-  const int len = object->length();
-  DCHECK(elements_to_trim < len);
+  if (bytes_to_trim == 0) {
+    // No need to create filler and update live bytes counters, just initialize
+    // header of the trimmed array.
+    object->synchronized_set_length(len - elements_to_trim);
+    return;
+  }
 
   // Calculate location of new array end.
   Address new_end = object->address() + object->Size() - bytes_to_trim;

src/objects-inl.h

@@ -4225,7 +4225,7 @@ void* FixedTypedArrayBase::DataPtr() {
 }
 
 
-int FixedTypedArrayBase::DataSize(InstanceType type) {
+int FixedTypedArrayBase::ElementSize(InstanceType type) {
   int element_size;
   switch (type) {
 #define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size)                       \
@@ -4239,7 +4239,12 @@ int FixedTypedArrayBase::DataSize(InstanceType type) {
       UNREACHABLE();
       return 0;
   }
-  return length() * element_size;
+  return element_size;
+}
+
+
+int FixedTypedArrayBase::DataSize(InstanceType type) {
+  return length() * ElementSize(type);
 }
 
 
@@ -4258,6 +4263,11 @@ int FixedTypedArrayBase::TypedArraySize(InstanceType type) {
 }
 
 
+int FixedTypedArrayBase::TypedArraySize(InstanceType type, int length) {
+  return OBJECT_POINTER_ALIGN(kDataOffset + length * ElementSize(type));
+}
+
+
 uint8_t Uint8ArrayTraits::defaultValue() { return 0; }
 
 

src/objects.h

@@ -4880,6 +4880,7 @@ class FixedTypedArrayBase: public FixedArrayBase {
 
   inline int size();
 
+  static inline int TypedArraySize(InstanceType type, int length);
   inline int TypedArraySize(InstanceType type);
 
   // Use with care: returns raw pointer into heap.
@@ -4888,6 +4889,8 @@ class FixedTypedArrayBase: public FixedArrayBase {
   inline int DataSize();
 
  private:
+  static inline int ElementSize(InstanceType type);
+
   inline int DataSize(InstanceType type);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(FixedTypedArrayBase);

test/cctest/test-heap.cc

@@ -5312,3 +5312,54 @@ TEST(WritableVsImmortalRoots) {
     CHECK(!immortal || !writable);
   }
 }
+
+
+static void TestRightTrimFixedTypedArray(v8::ExternalArrayType type,
+                                         int initial_length,
+                                         int elements_to_trim) {
+  v8::HandleScope scope(CcTest::isolate());
+  Isolate* isolate = CcTest::i_isolate();
+  Factory* factory = isolate->factory();
+  Heap* heap = isolate->heap();
+
+  Handle<FixedTypedArrayBase> array =
+      factory->NewFixedTypedArray(initial_length, type);
+  int old_size = array->size();
+  heap->RightTrimFixedArray<Heap::FROM_MUTATOR>(*array, elements_to_trim);
+
+  // Check that free space filler is at the right place and did not smash the
+  // array header.
+  CHECK(array->IsFixedArrayBase());
+  CHECK_EQ(initial_length - elements_to_trim, array->length());
+  int new_size = array->size();
+  if (new_size != old_size) {
+    // Free space filler should be created in this case.
+    Address next_obj_address = array->address() + array->size();
+    CHECK(HeapObject::FromAddress(next_obj_address)->IsFiller());
+  }
+  heap->CollectAllAvailableGarbage();
+}
+
+
+TEST(Regress472513) {
+  CcTest::InitializeVM();
+  v8::HandleScope scope(CcTest::isolate());
+
+  // The combination of type/initial_length/elements_to_trim triggered
+  // typed array header smashing with free space filler (crbug/472513).
+
+  // 64-bit cases.
+  TestRightTrimFixedTypedArray(v8::kExternalUint8Array, 32, 6);
+  TestRightTrimFixedTypedArray(v8::kExternalUint8Array, 32 - 7, 6);
+  TestRightTrimFixedTypedArray(v8::kExternalUint16Array, 16, 6);
+  TestRightTrimFixedTypedArray(v8::kExternalUint16Array, 16 - 3, 6);
+  TestRightTrimFixedTypedArray(v8::kExternalUint32Array, 8, 6);
+  TestRightTrimFixedTypedArray(v8::kExternalUint32Array, 8 - 1, 6);
+
+  // 32-bit cases.
+  TestRightTrimFixedTypedArray(v8::kExternalUint8Array, 16, 3);
+  TestRightTrimFixedTypedArray(v8::kExternalUint8Array, 16 - 3, 3);
+  TestRightTrimFixedTypedArray(v8::kExternalUint16Array, 8, 3);
+  TestRightTrimFixedTypedArray(v8::kExternalUint16Array, 8 - 1, 3);
+  TestRightTrimFixedTypedArray(v8::kExternalUint32Array, 4, 3);
+}