Changes imported from Abseil "staging" branch:

- f679f7de2957ac4dca0a862d04f1165d2f503525 Merge GitHub PR #78: Fix typo in thread_identity.h by Derek Mauro <dmauro@google.com>
  - 369cbefc9ebb8503e3c25b1516c856dab3bed7ac Minor refactor of operator-(uint128). by Alex Strelnikov <strel@google.com>
  - fba0f8c33b051d90936ad0fcaa4bea83f554bf8d Merge GitHub PR #75: Fix typo in per_thread_tls.h by Derek Mauro <dmauro@google.com>
  - 76d5d25a54ab93c1ea3bc74b5a28ba335b0f2bab Implement InlinedVector::shrink_to_fit() method. by Abseil Team <absl-team@google.com>

GitOrigin-RevId: f679f7de2957ac4dca0a862d04f1165d2f503525
Change-Id: I03b39fdbd70c00a455d98d949d413dd7c8019578
This commit is contained in:
Abseil Team 2018-01-10 11:46:09 -08:00 committed by Derek Mauro
parent 98bff8b2bc
commit c742b72354
3 changed files with 117 additions and 7 deletions

View file

@ -573,6 +573,42 @@ class InlinedVector {
}
}
// InlinedVector::shrink_to_fit()
//
// Reduces memory usage by freeing unused memory.
// After this call `capacity()` will be equal to `max(N, size())`.
//
// If `size() <= N` and the elements are currently stored on the heap, they
// will be moved to the inlined storage and the heap memory deallocated.
// If `size() > N` and `size() < capacity()` the elements will be moved to
// a reallocated storage on heap.
void shrink_to_fit() {
const auto s = size();
if (!allocated() || s == capacity()) {
// There's nothing to deallocate.
return;
}
if (s <= N) {
// Move the elements to the inlined storage.
// We have to do this using a temporary, because inlined_storage and
// allocation_storage are in a union field.
auto temp = std::move(*this);
assign(std::make_move_iterator(temp.begin()),
std::make_move_iterator(temp.end()));
return;
}
// Reallocate storage and move elements.
// We can't simply use the same approach as above, because assign() would
// call into reserve() internally and reserve larger capacity than we need.
Allocation new_allocation(allocator(), s);
UninitializedCopy(std::make_move_iterator(allocated_space()),
std::make_move_iterator(allocated_space() + s),
new_allocation.buffer());
ResetAllocation(new_allocation, s);
}
// InlinedVector::swap()
//
// Swaps the contents of this inlined vector with the contents of `other`.

View file

@ -407,6 +407,69 @@ TEST(InlinedVectorTest, EmplaceBack) {
EXPECT_EQ(allocated_element.second, 1729);
}
TEST(InlinedVectorTest, ShrinkToFitGrowingVector) {
absl::InlinedVector<std::pair<std::string, int>, 1> v;
v.shrink_to_fit();
EXPECT_EQ(v.capacity(), 1);
v.emplace_back("answer", 42);
v.shrink_to_fit();
EXPECT_EQ(v.capacity(), 1);
v.emplace_back("taxicab", 1729);
EXPECT_GE(v.capacity(), 2);
v.shrink_to_fit();
EXPECT_EQ(v.capacity(), 2);
v.reserve(100);
EXPECT_GE(v.capacity(), 100);
v.shrink_to_fit();
EXPECT_EQ(v.capacity(), 2);
}
TEST(InlinedVectorTest, ShrinkToFitEdgeCases) {
{
absl::InlinedVector<std::pair<std::string, int>, 1> v;
v.emplace_back("answer", 42);
v.emplace_back("taxicab", 1729);
EXPECT_GE(v.capacity(), 2);
v.pop_back();
v.shrink_to_fit();
EXPECT_EQ(v.capacity(), 1);
EXPECT_EQ(v[0].first, "answer");
EXPECT_EQ(v[0].second, 42);
}
{
absl::InlinedVector<std::string, 2> v(100);
v.resize(0);
v.shrink_to_fit();
EXPECT_EQ(v.capacity(), 2); // inlined capacity
}
{
absl::InlinedVector<std::string, 2> v(100);
v.resize(1);
v.shrink_to_fit();
EXPECT_EQ(v.capacity(), 2); // inlined capacity
}
{
absl::InlinedVector<std::string, 2> v(100);
v.resize(2);
v.shrink_to_fit();
EXPECT_EQ(v.capacity(), 2);
}
{
absl::InlinedVector<std::string, 2> v(100);
v.resize(3);
v.shrink_to_fit();
EXPECT_EQ(v.capacity(), 3);
}
}
TEST(IntVec, Insert) {
for (int len = 0; len < 20; len++) {
for (int pos = 0; pos <= len; pos++) {
@ -1589,6 +1652,20 @@ TEST(AllocatorSupportTest, CountAllocations) {
AllocVec v3(std::move(v), alloc3);
EXPECT_THAT(allocated3, v3.size() * sizeof(int));
}
EXPECT_EQ(allocated, 0);
{
// Test shrink_to_fit deallocations.
AllocVec v(8, 2, alloc);
EXPECT_EQ(allocated, 8 * sizeof(int));
v.resize(5);
EXPECT_EQ(allocated, 8 * sizeof(int));
v.shrink_to_fit();
EXPECT_EQ(allocated, 5 * sizeof(int));
v.resize(4);
EXPECT_EQ(allocated, 5 * sizeof(int));
v.shrink_to_fit();
EXPECT_EQ(allocated, 0);
}
}
TEST(AllocatorSupportTest, SwapBothAllocated) {

View file

@ -460,13 +460,10 @@ inline bool operator>=(uint128 lhs, uint128 rhs) {
// Unary operators.
inline uint128 operator-(uint128 val) {
const uint64_t hi_flip = ~Uint128High64(val);
const uint64_t lo_flip = ~Uint128Low64(val);
const uint64_t lo_add = lo_flip + 1;
if (lo_add < lo_flip) {
return MakeUint128(hi_flip + 1, lo_add);
}
return MakeUint128(hi_flip, lo_add);
uint64_t hi = ~Uint128High64(val);
uint64_t lo = ~Uint128Low64(val) + 1;
if (lo == 0) ++hi; // carry
return MakeUint128(hi, lo);
}
inline bool operator!(uint128 val) {