Revision: 5311
Author: [email protected]
Date: Fri Aug 20 05:38:33 2010
Log: We can use the array trim trick in old paged space as well as
new space.
Review URL: http://codereview.chromium.org/3143032
http://code.google.com/p/v8/source/detail?r=5311
Modified:
/branches/bleeding_edge/src/builtins.cc
=======================================
--- /branches/bleeding_edge/src/builtins.cc Mon Aug 16 10:19:38 2010
+++ /branches/bleeding_edge/src/builtins.cc Fri Aug 20 05:38:33 2010
@@ -306,12 +306,10 @@
static FixedArray* LeftTrimFixedArray(FixedArray* elms, int to_trim) {
ASSERT(elms->map() != Heap::fixed_cow_array_map());
- // For now this trick is only applied to fixed arrays in new space.
+ // For now this trick is only applied to fixed arrays in new and paged
space.
// In large object space the object's start must coincide with chunk
// and thus the trick is just not applicable.
- // In old space we do not use this trick to avoid dealing with
- // region dirty marks.
- ASSERT(Heap::new_space()->Contains(elms));
+ ASSERT(!Heap::lo_space()->Contains(elms));
STATIC_ASSERT(FixedArray::kMapOffset == 0);
STATIC_ASSERT(FixedArray::kLengthOffset == kPointerSize);
@@ -321,6 +319,17 @@
const int len = elms->length();
+ if (to_trim > FixedArray::kHeaderSize / kPointerSize &&
+ !Heap::new_space()->Contains(elms)) {
+ // If we are doing a big trim in old space then we zap the space that
was
+ // formerly part of the array so that the GC (aided by the card-based
+ // remembered set) won't find pointers to new-space there.
+ Object** zap = reinterpret_cast<Object**>(elms->address());
+ zap++; // Header of filler must be at least one word so skip that.
+ for (int i = 1; i < to_trim; i++) {
+ *zap++ = Smi::FromInt(0);
+ }
+ }
// Technically in new space this write might be omitted (except for
// debug mode which iterates through the heap), but to play safer
// we still do it.
@@ -329,9 +338,8 @@
former_start[to_trim] = Heap::fixed_array_map();
former_start[to_trim + 1] = Smi::FromInt(len - to_trim);
- ASSERT_EQ(elms->address() + to_trim * kPointerSize,
- (elms + to_trim * kPointerSize)->address());
- return elms + to_trim * kPointerSize;
+ return FixedArray::cast(HeapObject::FromAddress(
+ elms->address() + to_trim * kPointerSize));
}
@@ -497,8 +505,8 @@
first = Heap::undefined_value();
}
- if (Heap::new_space()->Contains(elms)) {
- // As elms still in the same space they used to be (new space),
+ if (!Heap::lo_space()->Contains(elms)) {
+ // As elms still in the same space they used to be,
// there is no need to update region dirty mark.
array->set_elements(LeftTrimFixedArray(elms, 1), SKIP_WRITE_BARRIER);
} else {
@@ -724,7 +732,7 @@
if (item_count < actual_delete_count) {
// Shrink the array.
- const bool trim_array = Heap::new_space()->Contains(elms) &&
+ const bool trim_array = !Heap::lo_space()->Contains(elms) &&
((actual_start + item_count) <
(len - actual_delete_count - actual_start));
if (trim_array) {
--
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