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Use folly::IsRelocatable in folly::small_vector #1934

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Use folly::IsRelocatable in folly::small_vector #1934

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17 changes: 14 additions & 3 deletions folly/small_vector.h
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Original file line number Diff line number Diff line change
Expand Up @@ -549,9 +549,8 @@ class small_vector
this->u.setCapacity(o.u.getCapacity());
}
} else {
if (kShouldCopyInlineTrivial) {
copyInlineTrivial<Value>(o);
o.resetSizePolicy();
if (kShouldRelocateInlineTrivial) {
relocateInlineTrivial(o);
} else {
auto n = o.size();
std::uninitialized_copy(
Expand Down Expand Up @@ -1047,6 +1046,14 @@ class small_vector
this->setSize(sz);
}

void relocateInlineTrivial(small_vector& o) {
// Copy the entire inline storage, instead of just size() values, to make
// the loop fixed-size and unrollable.
std::memcpy(u.buffer(), o.u.buffer(), MaxInline * kSizeOfValue);
this->setSize(o.size());
o.resetSizePolicy();
}

template <class T>
typename std::enable_if<is_trivially_copyable_v<T>>::type copyInlineTrivial(
small_vector const& o) {
Expand Down Expand Up @@ -1313,6 +1320,10 @@ class small_vector
is_trivially_copyable_v<Value> &&
sizeof(InlineStorageType) <= hardware_constructive_interference_size / 2;

static constexpr bool kShouldRelocateInlineTrivial =
IsRelocatable<Value>::value &&
sizeof(InlineStorageType) <= hardware_constructive_interference_size / 2;

static bool constexpr kHasInlineCapacity = !BaseType::kAlwaysUseHeap &&
sizeof(HeapPtrWithCapacity) < sizeof(InlineStorageType);

Expand Down