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

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index b0ddc7d457e8dd6091d28802475f9bfe57cc27f1..0273abc525e147c08bd5fefc6e01a3c40f98641f 100644
--- a/src/heap/heap.cc
+++ b/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();
@@ -3580,17 +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);
-
-  // Calculate location of new array end.
-  Address new_end = object->address() + object->Size() - bytes_to_trim;
+  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;
+  }
 
   // Technically in new space this write might be omitted (except for
   // debug mode which iterates through the heap), but to play safer
@@ -3599,6 +3613,8 @@ void Heap::RightTrimFixedArray(FixedArrayBase* object, int elements_to_trim) {
   // TODO(hpayer): We should shrink the large object page if the size
   // of the object changed significantly.
   if (!lo_space()->Contains(object)) {
+    // Calculate location of new array end.
+    Address new_end = object->address() + object->Size() - bytes_to_trim;

[Michael Starzinger, 2015/04/02 10:45:27]

nit: Can we keep the calculation outside where it was before? The common case is
that the object is not in LO-space, so the runtime impact doesn't matter. But
IMHO it keeps the code way more readable.

[Igor Sheludko, 2015/04/02 11:03:10]

Done.

     CreateFillerObjectAt(new_end, bytes_to_trim);
   }