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[IdentityMap] Fix size if GC short-cuts objects.

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BUG=chromium:704132

Change-Id: I6146c907d4f26147676f7dde4974c44fe541e8fe
Reviewed-on: https://chromium-review.googlesource.com/541362
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46059}
This commit is contained in:
Ross McIlroy 2017-06-20 16:05:28 +01:00 committed by Commit Bot
parent 73ddfb146b
commit d58bb2dcfa
2 changed files with 56 additions and 3 deletions
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7
src/identity-map.cc
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@ -243,6 +243,13 @@ void IdentityMapBase::Rehash() {
for (auto pair : reinsert) {
int index = InsertKey(pair.first);
DCHECK_GE(index, 0);
if (values_[index] != nullptr) {
// During GC some objects have been shortcut to point to the same
// underlying object - we can only chose one of the entries so keep the
// first one seen and reduce the size of the map appropriately
// (see crbug.com/704132 for details).
size_--;
}
values_[index] = pair.second;
}
}

52
test/cctest/test-identity-map.cc
View File

@ -187,7 +187,6 @@ class IdentityMapTester : public HandleAndZoneScope {
void Rehash() { map.Rehash(); }
};
TEST(Find_smi_not_found) {
IdentityMapTester t;
for (int i = 0; i < 100; i++) {
@ -673,7 +672,6 @@ TEST(Collisions_7) { CollisionTest(7); }
TEST(Resize) { CollisionTest(9, false, true); }
TEST(Rehash) { CollisionTest(11, true, false); }
TEST(ExplicitGC) {
IdentityMapTester t;
Handle<Object> num_keys[] = {t.num(2.1), t.num(2.4), t.num(3.3), t.num(4.3),
@ -695,7 +693,6 @@ TEST(ExplicitGC) {
}
}
TEST(CanonicalHandleScope) {
Isolate* isolate = CcTest::i_isolate();
Heap* heap = CcTest::heap();
@ -775,5 +772,54 @@ TEST(CanonicalHandleScope) {
}
}
TEST(GCShortCutting) {
IdentityMapTester t;
Isolate* isolate = CcTest::i_isolate();
Factory* factory = isolate->factory();
const int kDummyValue = 0;
for (int i = 0; i < 16; i++) {
// Insert a varying number of Smis as padding to ensure some tests straddle
// a boundary where the thin string short cutting will cause size_ to be
// greater to capacity_ if not corrected by IdentityMap
// (see crbug.com/704132).
for (int j = 0; j < i; j++) {
t.map.Set(t.smi(j), reinterpret_cast<void*>(kDummyValue));
}
Handle<String> thin_string =
factory->NewStringFromAsciiChecked("thin_string");
Handle<String> internalized_string =
factory->InternalizeString(thin_string);
DCHECK_IMPLIES(FLAG_thin_strings, thin_string->IsThinString());
DCHECK_NE(*thin_string, *internalized_string);
// Insert both keys into the map.
t.map.Set(thin_string, &thin_string);
t.map.Set(internalized_string, &internalized_string);
// Do an explicit, real GC, this should short-cut the thin string to point
// to the internalized string.
t.heap()->CollectGarbage(i::NEW_SPACE,
i::GarbageCollectionReason::kTesting);
DCHECK_IMPLIES(FLAG_thin_strings && !FLAG_optimize_for_size,
*thin_string == *internalized_string);
// Check that getting the object points to one of the handles.
void** thin_string_entry = t.map.Get(thin_string);
CHECK(*thin_string_entry == &thin_string ||
*thin_string_entry == &internalized_string);
void** internalized_string_entry = t.map.Get(internalized_string);
CHECK(*internalized_string_entry == &thin_string ||
*internalized_string_entry == &internalized_string);
// Trigger resize.
for (int j = 0; j < 16; j++) {
t.map.Set(t.smi(j + 16), reinterpret_cast<void*>(kDummyValue));
}
t.map.Clear();
}
}
} // namespace internal
} // namespace v8