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Add arena enabled copy construction.
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Arena enabled copy construction provides efficiency gains for the rather common construct where a message is currently copied by first creating a default initialized instance through the regular (arena) constructor, and then recursively filled from the source message using 'MergeFrom' or 'CopyFrom'.

Arena enabled copy construction is feature gated in port_def.inc and currently not enabled by default.

PiperOrigin-RevId: 558854125
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@martijnvels @copybara-github
martijnvels authored and copybara-github committed Aug 21, 2023
1 parent ef58724 commit a2b3470
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Showing 13 changed files with 930 additions and 17 deletions.
60 changes: 54 additions & 6 deletions src/google/protobuf/compiler/cpp/field.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,7 @@ FieldGeneratorBase::FieldGeneratorBase(const FieldDescriptor* descriptor,
const Options& options,
MessageSCCAnalyzer* scc)
: descriptor_(descriptor), options_(options) {
bool is_repeated_or_map = descriptor->is_repeated();
should_split_ = ShouldSplit(descriptor, options);
is_oneof_ = descriptor->real_containing_oneof() != nullptr;
switch (descriptor->cpp_type()) {
Expand All @@ -132,26 +133,71 @@ FieldGeneratorBase::FieldGeneratorBase(const FieldDescriptor* descriptor,
case FieldDescriptor::CPPTYPE_FLOAT:
case FieldDescriptor::CPPTYPE_DOUBLE:
case FieldDescriptor::CPPTYPE_BOOL:
is_trivial_ = !(descriptor->is_repeated() || descriptor->is_map());
has_trivial_value_ = is_trivial_;
is_trivial_ = has_trivial_value_ = !is_repeated_or_map;
has_default_constexpr_constructor_ = is_repeated_or_map;
break;
case FieldDescriptor::CPPTYPE_STRING:
is_string_ = true;
string_type_ = descriptor->options().ctype();
is_inlined_ = IsStringInlined(descriptor, options);
is_bytes_ = descriptor->type() == FieldDescriptor::TYPE_BYTES;
has_default_constexpr_constructor_ = is_repeated_or_map;
break;
case FieldDescriptor::CPPTYPE_MESSAGE:
is_message_ = true;
is_group_ = descriptor->type() == FieldDescriptor::TYPE_GROUP;
is_foreign_ = IsCrossFileMessage(descriptor);
is_lazy_ = IsLazy(descriptor, options, scc);
is_weak_ = IsImplicitWeakField(descriptor, options, scc);
if (!(descriptor->is_repeated() || descriptor->is_map())) {
has_trivial_value_ = !is_lazy_;
}
is_lazy_ = IsLazy(descriptor, options, scc);
has_trivial_value_ = !(is_repeated_or_map || is_lazy_);
has_default_constexpr_constructor_ = is_repeated_or_map || is_lazy_;
break;
}

has_trivial_zero_default_ = CanInitializeByZeroing(descriptor, options, scc);
}

void FieldGeneratorBase::GenerateMemberConstexprConstructor(
io::Printer* p) const {
ABSL_CHECK(!descriptor_->is_extension());
if (descriptor_->is_repeated()) {
p->Emit("$name$_{}");
} else {
p->Emit({{"default", DefaultValue(options_, descriptor_)}},
"$name$_{$default$}");
}
}

void FieldGeneratorBase::GenerateMemberConstructor(io::Printer* p) const {
ABSL_CHECK(!descriptor_->is_extension());
if (descriptor_->is_map()) {
p->Emit("$name$_{visibility, arena}");
} else if (descriptor_->is_repeated()) {
if (ShouldSplit(descriptor_, options_)) {
p->Emit("$name$_{}"); // RawPtr<Repeated>
} else {
p->Emit("$name$_{visibility, arena}");
}
} else {
p->Emit({{"default", DefaultValue(options_, descriptor_)}},
"$name$_{$default$}");
}
}

void FieldGeneratorBase::GenerateMemberCopyConstructor(io::Printer* p) const {
ABSL_CHECK(!descriptor_->is_extension());
if (descriptor_->is_repeated()) {
p->Emit("$name$_{visibility, arena, from.$name$_}");
} else {
p->Emit("$name$_{from.$name$_}");
}
}

void FieldGeneratorBase::GenerateOneofCopyConstruct(io::Printer* p) const {
ABSL_CHECK(!descriptor_->is_extension()) << "Not supported";
ABSL_CHECK(!descriptor_->is_repeated()) << "Not supported";
ABSL_CHECK(!descriptor_->is_map()) << "Not supported";
p->Emit("$field$ = from.$field$;\n");
}

void FieldGeneratorBase::GenerateAggregateInitializer(io::Printer* p) const {
Expand Down Expand Up @@ -275,6 +321,8 @@ void InlinedStringVars(const FieldDescriptor* field, const Options& opts,

int32_t index = *idx / 32;
std::string mask = absl::StrFormat("0x%08xu", 1u << (*idx % 32));
vars.emplace_back("inlined_string_index", index);
vars.emplace_back("inlined_string_mask", mask);

absl::string_view array = IsMapEntryMessage(field->containing_type())
? "_inlined_string_donated_"
Expand Down
81 changes: 80 additions & 1 deletion src/google/protobuf/compiler/cpp/field.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,10 @@ class FieldGeneratorBase {
// trivial, or a (raw) pointer value to a singular, non lazy message.
bool has_trivial_value() const { return has_trivial_value_; }

// Returns true if the provided field has a trivial zero default.
// I.e., the field can be initialized with `memset(&field, 0, sizeof(field))`
bool has_trivial_zero_default() const { return has_trivial_zero_default_; }

// Returns true if the field is a singular or repeated message.
// This includes group message types. To explicitly check if a message
// type is a group type, use the `is_group()` function,
Expand Down Expand Up @@ -113,6 +117,12 @@ class FieldGeneratorBase {
// allocated. Applies to string and message value.
bool is_inlined() const { return is_inlined_; }

// Returns true if this field has an appropriate default constexpr
// constructor. i.e., there is no need for an explicit initializer.
bool has_default_constexpr_constructor() const {
return has_default_constexpr_constructor_;
}

virtual std::vector<io::Printer::Sub> MakeVars() const { return {}; }

virtual void GeneratePrivateMembers(io::Printer* p) const = 0;
Expand Down Expand Up @@ -150,6 +160,32 @@ class FieldGeneratorBase {
<< descriptor_->cpp_type_name();
}

// Generates constexpr member initialization code, e.g.: `foo_{5}`.
// The default implementation generates the following code:
// - repeated fields and maps: `field_{}`
// - all other fields: `field_{<default value>}`
virtual void GenerateMemberConstexprConstructor(io::Printer* p) const;

// Generates member initialization code, e.g.: `foo_(5)`.
// The default implementation generates the following code:
// - repeated fields and maps: `field_{visibility, arena}`
// - split repeated fields (RawPtr): `field_{}`
// - all other fields: `field_{<default value>}`
virtual void GenerateMemberConstructor(io::Printer* p) const;

// Generates member copy initialization code, e.g.: `foo_(5)`.
// The default implementation generates the following code:
// - repeated fields and maps: `field_{visibility, arena, from.field_}`
// - all other fields: `field_{from.field_}`
virtual void GenerateMemberCopyConstructor(io::Printer* p) const;

// Generates 'placement new' copy construction code used to
// explicitly copy initialize oneof field values.
// The default implementation checks the current field to not be repeated,
// an extension or a map, and generates the following code:
// - `field_ = from.field_`
virtual void GenerateOneofCopyConstruct(io::Printer* p) const;

virtual void GenerateAggregateInitializer(io::Printer* p) const;

virtual void GenerateConstexprAggregateInitializer(io::Printer* p) const;
Expand All @@ -170,15 +206,16 @@ class FieldGeneratorBase {
}

protected:
// TODO(b/245791219): Remove these members and make this a pure interface.
const FieldDescriptor* descriptor_;
const Options& options_;
MessageSCCAnalyzer* scc_;
absl::flat_hash_map<absl::string_view, std::string> variables_;

private:
bool should_split_ = false;
bool is_trivial_ = false;
bool has_trivial_value_ = false;
bool has_trivial_zero_default_ = false;
bool is_message_ = false;
bool is_group_ = false;
bool is_string_ = false;
Expand All @@ -189,6 +226,7 @@ class FieldGeneratorBase {
bool is_weak_ = false;
bool is_oneof_ = false;
FieldOptions::CType string_type_ = FieldOptions::STRING;
bool has_default_constexpr_constructor_ = false;
};

inline FieldGeneratorBase::~FieldGeneratorBase() = default;
Expand Down Expand Up @@ -220,6 +258,27 @@ class FieldGenerator {
FieldGenerator(FieldGenerator&&) = default;
FieldGenerator& operator=(FieldGenerator&&) = default;

// Properties: see FieldGeneratorBase for documentation
bool should_split() const { return impl_->should_split(); }
bool is_trivial() const { return impl_->is_trivial(); }
bool has_trivial_value() const { return impl_->has_trivial_value(); }
bool has_trivial_zero_default() const {
return impl_->has_trivial_zero_default();
}
bool is_message() const { return impl_->is_message(); }
bool is_group() const { return impl_->is_group(); }
bool is_weak() const { return impl_->is_weak(); }
bool is_lazy() const { return impl_->is_lazy(); }
bool is_foreign() const { return impl_->is_foreign(); }
bool is_string() const { return impl_->is_string(); }
bool is_bytes() const { return impl_->is_bytes(); }
FieldOptions::CType string_type() const { return impl_->string_type(); }
bool is_oneof() const { return impl_->is_oneof(); }
bool is_inlined() const { return impl_->is_inlined(); }
bool has_default_constexpr_constructor() const {
return impl_->has_default_constexpr_constructor();
}

// Prints private members needed to represent this field.
//
// These are placed inside the class definition.
Expand All @@ -236,6 +295,26 @@ class FieldGenerator {
impl_->GenerateStaticMembers(p);
}

void GenerateMemberConstructor(io::Printer* p) const {
auto vars = PushVarsForCall(p);
impl_->GenerateMemberConstructor(p);
}

void GenerateMemberCopyConstructor(io::Printer* p) const {
auto vars = PushVarsForCall(p);
impl_->GenerateMemberCopyConstructor(p);
}

void GenerateOneofCopyConstruct(io::Printer* p) const {
auto vars = PushVarsForCall(p);
impl_->GenerateOneofCopyConstruct(p);
}

void GenerateMemberConstexprConstructor(io::Printer* p) const {
auto vars = PushVarsForCall(p);
impl_->GenerateMemberConstexprConstructor(p);
}

// Generates declarations for all of the accessor functions related to this
// field.
//
Expand Down
37 changes: 36 additions & 1 deletion src/google/protobuf/compiler/cpp/field_generators/cord_field.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,7 @@ void SetCordVariables(
(*variables)["default_variable_field"] = MakeDefaultFieldName(descriptor);
(*variables)["default_variable"] =
descriptor->default_value_string().empty()
? absl::StrCat(ProtobufNamespace(options),
? absl::StrCat("::", ProtobufNamespace(options),
"::internal::GetEmptyCordAlreadyInited()")
: absl::StrCat(
QualifiedClassName(descriptor->containing_type(), options),
Expand All @@ -88,7 +88,9 @@ class CordFieldGenerator : public FieldGeneratorBase {
void GenerateMergingCode(io::Printer* printer) const override;
void GenerateSwappingCode(io::Printer* printer) const override;
void GenerateConstructorCode(io::Printer* printer) const override;
#ifndef PROTOBUF_EXPLICIT_CONSTRUCTORS
void GenerateDestructorCode(io::Printer* printer) const override;
#endif // !PROTOBUF_EXPLICIT_CONSTRUCTORS
void GenerateArenaDestructorCode(io::Printer* printer) const override;
void GenerateSerializeWithCachedSizesToArray(
io::Printer* printer) const override;
Expand All @@ -99,6 +101,37 @@ class CordFieldGenerator : public FieldGeneratorBase {
ArenaDtorNeeds NeedsArenaDestructor() const override {
return ArenaDtorNeeds::kRequired;
}

void GenerateMemberConstexprConstructor(io::Printer* p) const override {
if (descriptor_->default_value_string().empty()) {
p->Emit("$name$_{}");
} else {
p->Emit({{"Split", ShouldSplit(descriptor_, options_) ? "Split::" : ""}},
"$name$_{::absl::strings_internal::MakeStringConstant("
"$classname$::Impl_::$Split$_default_$name$_func_{})}");
}
}

void GenerateMemberConstructor(io::Printer* p) const override {
auto vars = p->WithVars(variables_);
if (descriptor_->default_value_string().empty()) {
p->Emit("$name$_{}");
} else {
p->Emit("$name$_{::absl::string_view($default$, $default_length$)}");
}
}

void GenerateMemberCopyConstructor(io::Printer* p) const override {
auto vars = p->WithVars(variables_);
p->Emit("$name$_{from.$name$_}");
}

void GenerateOneofCopyConstruct(io::Printer* p) const override {
auto vars = p->WithVars(variables_);
p->Emit(R"cc(
$field$ = ::$proto_ns$::Arena::Create<absl::Cord>(arena, *from.$field$);
)cc");
}
};

class CordOneofFieldGenerator : public CordFieldGenerator {
Expand Down Expand Up @@ -224,6 +257,7 @@ void CordFieldGenerator::GenerateConstructorCode(io::Printer* printer) const {
}
}

#ifndef PROTOBUF_EXPLICIT_CONSTRUCTORS
void CordFieldGenerator::GenerateDestructorCode(io::Printer* printer) const {
Formatter format(printer, variables_);
if (should_split()) {
Expand All @@ -233,6 +267,7 @@ void CordFieldGenerator::GenerateDestructorCode(io::Printer* printer) const {
}
format("$field$.~Cord();\n");
}
#endif // !PROTOBUF_EXPLICIT_CONSTRUCTORS

void CordFieldGenerator::GenerateArenaDestructorCode(
io::Printer* printer) const {
Expand Down
28 changes: 28 additions & 0 deletions src/google/protobuf/compiler/cpp/field_generators/enum_field.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,7 @@
#include <vector>

#include "absl/log/absl_check.h"
#include "absl/log/absl_log.h"
#include "absl/memory/memory.h"
#include "absl/strings/substitute.h"
#include "google/protobuf/compiler/cpp/field.h"
Expand Down Expand Up @@ -304,9 +305,11 @@ class RepeatedEnum : public FieldGeneratorBase {
$field_$.DeleteIfNotDefault();
)cc");
} else {
#ifndef PROTOBUF_EXPLICIT_CONSTRUCTORS
p->Emit(R"cc(
_internal_mutable_$name$()->~RepeatedField();
)cc");
#endif // !PROTOBUF_EXPLICIT_CONSTRUCTORS
}
}

Expand Down Expand Up @@ -346,6 +349,31 @@ class RepeatedEnum : public FieldGeneratorBase {
}
}

void GenerateMemberConstexprConstructor(io::Printer* p) const override {
p->Emit("$name$_{}");
if (has_cached_size_) {
p->Emit(",\n_$name$_cached_byte_size_{0}");
}
}

void GenerateMemberConstructor(io::Printer* p) const override {
p->Emit("$name$_{visibility, arena}");
if (has_cached_size_) {
p->Emit(",\n_$name$_cached_byte_size_{0}");
}
}

void GenerateMemberCopyConstructor(io::Printer* p) const override {
p->Emit("$name$_{visibility, arena, from.$name$_}");
if (has_cached_size_) {
p->Emit(",\n_$name$_cached_byte_size_{0}");
}
}

void GenerateOneofCopyConstruct(io::Printer* p) const override {
ABSL_LOG(FATAL) << "Not supported";
}

void GenerateCopyConstructorCode(io::Printer* p) const override {
if (should_split()) {
p->Emit(R"cc(
Expand Down
3 changes: 2 additions & 1 deletion src/google/protobuf/compiler/cpp/field_generators/map_field.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -182,10 +182,11 @@ class Map : public FieldGeneratorBase {
)cc");
return;
}

#ifndef PROTOBUF_EXPLICIT_CONSTRUCTORS
p->Emit(R"cc(
$field_$.~$MapField$();
)cc");
#endif // !PROTOBUF_EXPLICIT_CONSTRUCTORS
}

void GeneratePrivateMembers(io::Printer* p) const override;
Expand Down
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