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Reduce code size for Initializer: reuse the implementation of `refe…
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…rence` for

`const_reference` when their code is the same.

PiperOrigin-RevId: 670529775
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@QrczakMK
QrczakMK committed Sep 3, 2024
1 parent 5318b7b commit ccd777a
Showing 1 changed file with 102 additions and 47 deletions.
149 changes: 102 additions & 47 deletions riegeli/base/initializer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -217,7 +217,8 @@ class InitializerBase {
const T& ConstReference(TemporaryStorage<T>&& storage
ABSL_ATTRIBUTE_LIFETIME_BOUND =
TemporaryStorage<T>()) && {
return methods()->const_reference(context(), std::move(storage));
T&& reference = methods()->const_reference(context(), std::move(storage));
return reference;
}

private:
Expand Down Expand Up @@ -265,25 +266,27 @@ class InitializerBase {
static T&& ReferenceMethodFromConstMaker(TypeErasedRef context,
TemporaryStorage<T>&& storage);

static const T& ConstReferenceMethodDefault(TypeErasedRef context,
TemporaryStorage<T>&& storage);

template <typename Arg,
std::enable_if_t<CanBindTo<const T&, Arg&&>::value, int> = 0>
static const T& ConstReferenceMethodFromObject(TypeErasedRef context,
TemporaryStorage<T>&& storage);
template <typename Arg,
std::enable_if_t<!CanBindTo<const T&, Arg&&>::value, int> = 0>
static const T& ConstReferenceMethodFromObject(TypeErasedRef context,
TemporaryStorage<T>&& storage);
// This is used only if `!CanBindTo<T&&, Arg&&>::value` and
// `CanBindTo<const T&, Arg&&>::value`. Otherwise
// `ConstReferenceMethodFromObject` reuses `ReferenceMethodFromObject`.
template <typename Arg>
static T&& ConstReferenceMethodFromObject(TypeErasedRef context,
TemporaryStorage<T>&& storage);

// This is used only if `!CanBindTo<T&&, Args&&...>::value` and
// `CanBindTo<const T&, Args&&...>::value`. Otherwise
// `ConstReferenceMethodFromMaker` reuses `ReferenceMethodFromMaker`.
template <typename... Args>
static const T& ConstReferenceMethodFromMaker(TypeErasedRef context,
TemporaryStorage<T>&& storage);
static T&& ConstReferenceMethodFromMaker(TypeErasedRef context,
TemporaryStorage<T>&& storage);

// This is used only if `!CanBindTo<T&&, Args&&...>::value` and
// `CanBindTo<const T&, Args&&...>::value`. Otherwise
// `ConstReferenceMethodFromConstMaker` reuses
// `ReferenceMethodFromConstMaker`.
template <typename... Args>
static const T& ConstReferenceMethodFromConstMaker(
TypeErasedRef context, TemporaryStorage<T>&& storage);
static T&& ConstReferenceMethodFromConstMaker(TypeErasedRef context,
TemporaryStorage<T>&& storage);

protected:
struct Methods {
Expand All @@ -293,8 +296,10 @@ class InitializerBase {
void (*construct_at)(TypeErasedRef context, void* ptr);
#endif
T && (*reference)(TypeErasedRef context, TemporaryStorage<T>&& storage);
const T& (*const_reference)(TypeErasedRef context,
TemporaryStorage<T>&& storage);
// `const_reference` returns `const T&` cast to `T&&`, so that its
// implementations can reuse code from `reference` if possible.
T && (*const_reference)(TypeErasedRef context,
TemporaryStorage<T>&& storage);
};

explicit InitializerBase(const Methods* methods);
Expand All @@ -312,7 +317,27 @@ class InitializerBase {
#else
ConstructAtMethodDefault,
#endif
ReferenceMethodDefault, ConstReferenceMethodDefault};
ReferenceMethodDefault, ReferenceMethodDefault};

template <
typename Arg,
std::enable_if_t<absl::conjunction<absl::negation<CanBindTo<T&&, Arg&&>>,
CanBindTo<const T&, Arg&&>>::value,
int> = 0>
static constexpr auto MakeConstReferenceMethodFromObject()
-> T && (*)(TypeErasedRef context, TemporaryStorage<T>&& storage) {
return ConstReferenceMethodFromObject<Arg>;
}
template <
typename Arg,
std::enable_if_t<
absl::disjunction<CanBindTo<T&&, Arg&&>,
absl::negation<CanBindTo<const T&, Arg&&>>>::value,
int> = 0>
static constexpr auto MakeConstReferenceMethodFromObject()
-> T && (*)(TypeErasedRef context, TemporaryStorage<T>&& storage) {
return ReferenceMethodFromObject<Arg>;
}

template <typename Arg>
static constexpr Methods kMethodsFromObject = {
Expand All @@ -321,7 +346,28 @@ class InitializerBase {
#else
ConstructAtMethodFromObject<Arg>,
#endif
ReferenceMethodFromObject<Arg>, ConstReferenceMethodFromObject<Arg>};
ReferenceMethodFromObject<Arg>,
MakeConstReferenceMethodFromObject<Arg>()};

template <typename... Args,
std::enable_if_t<
absl::conjunction<absl::negation<CanBindTo<T&&, Args&&...>>,
CanBindTo<const T&, Args&&...>>::value,
int> = 0>
static constexpr auto MakeConstReferenceMethodFromMaker()
-> T && (*)(TypeErasedRef context, TemporaryStorage<T>&& storage) {
return ConstReferenceMethodFromMaker<Args...>;
}
template <typename... Args,
std::enable_if_t<
absl::disjunction<
CanBindTo<T&&, Args&&...>,
absl::negation<CanBindTo<const T&, Args&&...>>>::value,
int> = 0>
static constexpr auto MakeConstReferenceMethodFromMaker()
-> T && (*)(TypeErasedRef context, TemporaryStorage<T>&& storage) {
return ReferenceMethodFromMaker<Args...>;
}

template <typename... Args>
static constexpr Methods kMethodsFromMaker = {
Expand All @@ -331,7 +377,27 @@ class InitializerBase {
ConstructAtMethodFromMaker<Args...>,
#endif
ReferenceMethodFromMaker<Args...>,
ConstReferenceMethodFromMaker<Args...>};
MakeConstReferenceMethodFromMaker<Args...>()};

template <typename... Args,
std::enable_if_t<
absl::conjunction<absl::negation<CanBindTo<T&&, Args&&...>>,
CanBindTo<const T&, Args&&...>>::value,
int> = 0>
static constexpr auto MakeConstReferenceMethodFromConstMaker()
-> T && (*)(TypeErasedRef context, TemporaryStorage<T>&& storage) {
return ConstReferenceMethodFromConstMaker<Args...>;
}
template <typename... Args,
std::enable_if_t<
absl::disjunction<
CanBindTo<T&&, Args&&...>,
absl::negation<CanBindTo<const T&, Args&&...>>>::value,
int> = 0>
static constexpr auto MakeConstReferenceMethodFromConstMaker()
-> T && (*)(TypeErasedRef context, TemporaryStorage<T>&& storage) {
return ReferenceMethodFromConstMaker<Args...>;
}

template <typename... Args>
static constexpr Methods kMethodsFromConstMaker = {
Expand All @@ -341,7 +407,7 @@ class InitializerBase {
ConstructAtMethodFromConstMaker<Args...>,
#endif
ReferenceMethodFromConstMaker<Args...>,
ConstReferenceMethodFromConstMaker<Args...>};
MakeConstReferenceMethodFromConstMaker<Args...>()};

const Methods* methods() const { return methods_; }
TypeErasedRef context() const { return context_; }
Expand Down Expand Up @@ -998,43 +1064,32 @@ T&& InitializerBase<T>::ReferenceMethodFromConstMaker(
}

template <typename T>
const T& InitializerBase<T>::ConstReferenceMethodDefault(
ABSL_ATTRIBUTE_UNUSED TypeErasedRef context,
TemporaryStorage<T>&& storage) {
return storage.emplace();
}

template <typename T>
template <typename Arg,
std::enable_if_t<CanBindTo<const T&, Arg&&>::value, int>>
const T& InitializerBase<T>::ConstReferenceMethodFromObject(
template <typename Arg>
T&& InitializerBase<T>::ConstReferenceMethodFromObject(
TypeErasedRef context,
ABSL_ATTRIBUTE_UNUSED TemporaryStorage<T>&& storage) {
return context.Cast<Arg>();
}

template <typename T>
template <typename Arg,
std::enable_if_t<!CanBindTo<const T&, Arg&&>::value, int>>
const T& InitializerBase<T>::ConstReferenceMethodFromObject(
TypeErasedRef context, TemporaryStorage<T>&& storage) {
return storage.emplace(context.Cast<Arg>());
const T& reference = context.Cast<Arg>();
return const_cast<T&&>(reference);
}

template <typename T>
template <typename... Args>
const T& InitializerBase<T>::ConstReferenceMethodFromMaker(
T&& InitializerBase<T>::ConstReferenceMethodFromMaker(
TypeErasedRef context, TemporaryStorage<T>&& storage) {
return context.Cast<MakerType<Args...>>().template ConstReference<T>(
std::move(storage));
const T& reference =
context.Cast<MakerType<Args...>>().template ConstReference<T>(
std::move(storage));
return const_cast<T&&>(reference);
}

template <typename T>
template <typename... Args>
const T& InitializerBase<T>::ConstReferenceMethodFromConstMaker(
T&& InitializerBase<T>::ConstReferenceMethodFromConstMaker(
TypeErasedRef context, TemporaryStorage<T>&& storage) {
return context.Cast<const MakerType<Args...>&>().template ConstReference<T>(
std::move(storage));
const T& reference =
context.Cast<const MakerType<Args...>&>().template ConstReference<T>(
std::move(storage));
return const_cast<T&&>(reference);
}

#if !__cpp_guaranteed_copy_elision
Expand Down

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