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Downgrade message members to base class pointer in oneofs with "too many" message fields.

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The compiler can merge all the different switch cases for all the message alternatives and generates O(1) accessors instead. The switch dispatch is effectively replaced with a virtual function dispatch.
This can significantly reduce code size for oneofs with a lot of message alternatives, specially if it _only_ has message alternatives.

PiperOrigin-RevId: 718025165
pull/20004/head
Protobuf Team Bot 1 month ago committed by Copybara-Service
parent a5920a728d
commit 7eec7a0043
5 changed files with 117 additions and 81 deletions
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  1. 132
      src/google/protobuf/compiler/cpp/field_generators/message_field.cc
  2. 4
      src/google/protobuf/compiler/plugin.pb.h
  3. 46
      src/google/protobuf/descriptor.pb.h
  4. 7
      src/google/protobuf/message_lite.cc
  5. 9
      src/google/protobuf/message_lite.h

132
src/google/protobuf/compiler/cpp/field_generators/message_field.cc
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@ -37,47 +37,38 @@ using ::google::protobuf::io::AnnotationCollector;
using Sub = ::google::protobuf::io::Printer::Sub;
std::vector<Sub> Vars(const FieldDescriptor* field, const Options& opts,
bool weak) {
bool is_weak, bool use_base_class) {
bool split = ShouldSplit(field, opts);
bool is_foreign = IsCrossFileMessage(field);
std::string field_name = FieldMemberName(field, split);
std::string qualified_type = FieldMessageTypeName(field, opts);
std::string default_ref =
QualifiedDefaultInstanceName(field->message_type(), opts);
std::string default_ptr =
QualifiedDefaultInstancePtr(field->message_type(), opts);
std::string base =
absl::StrCat("::", ProtobufNamespace(opts), "::", "MessageLite");
std::string base = absl::StrCat(
"::", ProtobufNamespace(opts), "::",
HasDescriptorMethods(field->file(), opts) ? "Message" : "MessageLite");
return {
{"Submsg", qualified_type},
{"MemberType", !weak ? qualified_type : base},
{"CompleteType", !is_foreign ? qualified_type : base},
{"MemberType", use_base_class ? base : qualified_type},
{"kDefault", default_ref},
{"kDefaultPtr", !weak
? default_ptr
: absl::Substitute("reinterpret_cast<const $0*>($1)",
base, default_ptr)},
Sub{"base_cast", !is_foreign && !weak
? ""
: absl::Substitute("reinterpret_cast<$0*>", base)}
Sub{"cast_to_field",
use_base_class ? absl::Substitute("reinterpret_cast<$0*>", base) : ""}
.ConditionalFunctionCall(),
Sub{"weak_cast",
!weak ? "" : absl::Substitute("reinterpret_cast<$0*>", base)}
.ConditionalFunctionCall(),
Sub{"foreign_cast",
Sub{"arena_cast",
!is_foreign ? "" : absl::Substitute("reinterpret_cast<$0*>", base)}
.ConditionalFunctionCall(),
{"cast_field_", !weak ? field_name
: absl::Substitute("reinterpret_cast<$0*>($1)",
qualified_type, field_name)},
{"Weak", weak ? "Weak" : ""},
{".weak", weak ? ".weak" : ""},
{"_weak", weak ? "_weak" : ""},
Sub("StrongRef",
!weak ? ""
: absl::StrCat(
StrongReferenceToType(field->message_type(), opts), ";"))
{"cast_field_", use_base_class
? absl::Substitute("reinterpret_cast<$0*>($1)",
qualified_type, field_name)
: field_name},
{"Weak", is_weak ? "Weak" : ""},
{".weak", is_weak ? ".weak" : ""},
{"_weak", is_weak ? "_weak" : ""},
Sub("StrongRef", !is_weak ? ""
: absl::StrCat(StrongReferenceToType(
field->message_type(), opts),
";"))
.WithSuffix(";"),
};
}
@ -94,7 +85,7 @@ class SingularMessage : public FieldGeneratorBase {
~SingularMessage() override = default;
std::vector<Sub> MakeVars() const override {
return Vars(field_, *opts_, is_weak());
return Vars(field_, *opts_, is_weak(), is_weak());
}
void GeneratePrivateMembers(io::Printer* p) const override {
@ -289,14 +280,11 @@ void SingularMessage::GenerateInlineAccessorDefinitions(io::Printer* p) const {
$TsanDetectConcurrentMutation$;
$PrepareSplitMessageForWrite$;
if (message_arena == nullptr) {
delete $base_cast$($field_$);
delete reinterpret_cast<$pb$::MessageLite*>($field_$);
}
if (value != nullptr) {
//~ When $Submsg$ is a cross-file type, have to read the arena
//~ through the virtual method, because the type isn't defined in
//~ this file, only forward-declared.
$pb$::Arena* submessage_arena = $base_cast$(value)->GetArena();
$pb$::Arena* submessage_arena = $arena_cast$(value)->GetArena();
if (message_arena != submessage_arena) {
value = $pbi$::GetOwnedMessage(message_arena, value, submessage_arena);
}
@ -468,10 +456,44 @@ class OneofMessage : public SingularMessage {
public:
OneofMessage(const FieldDescriptor* descriptor, const Options& options,
MessageSCCAnalyzer* scc_analyzer)
: SingularMessage(descriptor, options, scc_analyzer) {}
: SingularMessage(descriptor, options, scc_analyzer) {
auto* oneof = descriptor->containing_oneof();
num_message_fields_in_oneof_ = 0;
for (int i = 0; i < oneof->field_count(); ++i) {
num_message_fields_in_oneof_ +=
oneof->field(i)->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE;
}
}
~OneofMessage() override = default;
bool use_base_class() const {
if (is_weak()) return true;
// For non-weak oneof fields, we choose to use a base class pointer when the
// oneof has many message fields in it. Using a base class here is not
// about correctness, but about performance and binary size.
//
// This allows the compiler to merge all the different switch cases (since
// the code is identical for all message alternatives) reducing binary size.
// The runtime dispatch is effectively changed from a switch statement to a
// virtual function call. For many oneofs, it completely elides the switch
// dispatch.
//
// This constant is a tradeoff. We want to allow optimizations (like
// inlining) on small oneofs. For small oneofs the compiler can use faster
// alternatives to table-based jumps. Also, the technique used here has less
// of a binary size win for small oneofs.
static constexpr int kMaxStaticTypeCount = 3;
return num_message_fields_in_oneof_ >= kMaxStaticTypeCount &&
// Hot alternatives are kept as their static type for performance..
!IsLikelyPresent(field_, *opts_);
}
std::vector<Sub> MakeVars() const override {
return Vars(field_, *opts_, is_weak(), use_base_class());
}
void GenerateInlineAccessorDefinitions(io::Printer* p) const override;
void GenerateNonInlineAccessorDefinitions(io::Printer* p) const override;
void GenerateClearingCode(io::Printer* p) const override;
@ -484,6 +506,9 @@ class OneofMessage : public SingularMessage {
bool NeedsIsInitialized() const override;
void GenerateMergingCode(io::Printer* p) const override;
bool RequiresArena(GeneratorFunction func) const override;
private:
int num_message_fields_in_oneof_;
};
void OneofMessage::GenerateNonInlineAccessorDefinitions(io::Printer* p) const {
@ -492,7 +517,7 @@ void OneofMessage::GenerateNonInlineAccessorDefinitions(io::Printer* p) const {
$pb$::Arena* message_arena = GetArena();
clear_$oneof_name$();
if ($name$) {
$pb$::Arena* submessage_arena = $foreign_cast$($name$)->GetArena();
$pb$::Arena* submessage_arena = $arena_cast$($name$)->GetArena();
if (message_arena != submessage_arena) {
$name$ = $pbi$::GetOwnedMessage(message_arena, $name$, submessage_arena);
}
@ -569,7 +594,7 @@ void OneofMessage::GenerateInlineAccessorDefinitions(io::Printer* p) const {
clear_$oneof_name$();
if (value) {
set_has_$name_internal$();
$field_$ = $weak_cast$(value);
$field_$ = $cast_to_field$(value);
}
$annotate_set$;
// @@protoc_insertion_point(field_unsafe_arena_set_allocated:$pkg.Msg.field$)
@ -581,8 +606,8 @@ void OneofMessage::GenerateInlineAccessorDefinitions(io::Printer* p) const {
if ($not_has_field$) {
clear_$oneof_name$();
set_has_$name_internal$();
$field_$ =
$weak_cast$($superclass$::DefaultConstruct<$Submsg$>(GetArena()));
$field_$ = $cast_to_field$(
$superclass$::DefaultConstruct<$Submsg$>(GetArena()));
}
return $cast_field_$;
}
@ -662,22 +687,17 @@ void OneofMessage::GenerateIsInitialized(io::Printer* p) const {
bool OneofMessage::NeedsIsInitialized() const { return has_required_; }
void OneofMessage::GenerateMergingCode(io::Printer* p) const {
if (is_weak()) {
p->Emit(R"cc(
if (oneof_needs_init) {
_this->$field_$ = from.$field_$->New(arena);
}
_this->$field_$->CheckTypeAndMergeFrom(*from.$field_$);
)cc");
} else {
p->Emit(R"cc(
if (oneof_needs_init) {
_this->$field_$ = $superclass$::CopyConstruct(arena, *from.$field_$);
} else {
_this->$field_$->MergeFrom(from._internal_$name$());
}
)cc");
}
p->Emit({{"merge",
use_base_class() && !HasDescriptorMethods(field_->file(), options_)
? "CheckTypeAndMergeFrom"
: "MergeFrom"}},
R"cc(
if (oneof_needs_init) {
_this->$field_$ = $superclass$::CopyConstruct(arena, *from.$field_$);
} else {
_this->$field_$->$merge$(*from.$field_$);
}
)cc");
}
bool OneofMessage::RequiresArena(GeneratorFunction func) const {
@ -699,7 +719,7 @@ class RepeatedMessage : public FieldGeneratorBase {
~RepeatedMessage() override = default;
std::vector<Sub> MakeVars() const override {
return Vars(field_, *opts_, is_weak());
return Vars(field_, *opts_, is_weak(), is_weak());
}
void GeneratePrivateMembers(io::Printer* p) const override;

4
src/google/protobuf/compiler/plugin.pb.h
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@ -1652,7 +1652,7 @@ inline void CodeGeneratorRequest::set_allocated_compiler_version(::google::proto
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.compiler_version_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.compiler_version_);
}
if (value != nullptr) {
@ -1960,7 +1960,7 @@ inline void CodeGeneratorResponse_File::set_allocated_generated_code_info(::goog
}
if (value != nullptr) {
::google::protobuf::Arena* submessage_arena = reinterpret_cast<::google::protobuf::MessageLite*>(value)->GetArena();
::google::protobuf::Arena* submessage_arena = reinterpret_cast<::google::protobuf::Message*>(value)->GetArena();
if (message_arena != submessage_arena) {
value = ::google::protobuf::internal::GetOwnedMessage(message_arena, value, submessage_arena);
}

46
src/google/protobuf/descriptor.pb.h
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@ -12880,7 +12880,7 @@ inline void FileDescriptorProto::set_allocated_options(::google::protobuf::FileO
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.options_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.options_);
}
if (value != nullptr) {
@ -12978,7 +12978,7 @@ inline void FileDescriptorProto::set_allocated_source_code_info(::google::protob
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.source_code_info_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.source_code_info_);
}
if (value != nullptr) {
@ -13236,7 +13236,7 @@ inline void DescriptorProto_ExtensionRange::set_allocated_options(::google::prot
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.options_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.options_);
}
if (value != nullptr) {
@ -13767,7 +13767,7 @@ inline void DescriptorProto::set_allocated_options(::google::protobuf::MessageOp
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.options_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.options_);
}
if (value != nullptr) {
@ -14309,7 +14309,7 @@ inline void ExtensionRangeOptions::set_allocated_features(::google::protobuf::Fe
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.features_);
}
if (value != nullptr) {
@ -14905,7 +14905,7 @@ inline void FieldDescriptorProto::set_allocated_options(::google::protobuf::Fiel
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.options_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.options_);
}
if (value != nullptr) {
@ -15104,7 +15104,7 @@ inline void OneofDescriptorProto::set_allocated_options(::google::protobuf::Oneo
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.options_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.options_);
}
if (value != nullptr) {
@ -15385,7 +15385,7 @@ inline void EnumDescriptorProto::set_allocated_options(::google::protobuf::EnumO
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.options_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.options_);
}
if (value != nullptr) {
@ -15698,7 +15698,7 @@ inline void EnumValueDescriptorProto::set_allocated_options(::google::protobuf::
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.options_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.options_);
}
if (value != nullptr) {
@ -15919,7 +15919,7 @@ inline void ServiceDescriptorProto::set_allocated_options(::google::protobuf::Se
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.options_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.options_);
}
if (value != nullptr) {
@ -16228,7 +16228,7 @@ inline void MethodDescriptorProto::set_allocated_options(::google::protobuf::Met
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.options_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.options_);
}
if (value != nullptr) {
@ -17331,7 +17331,7 @@ inline void FileOptions::set_allocated_features(::google::protobuf::FeatureSet*
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.features_);
}
if (value != nullptr) {
@ -17623,7 +17623,7 @@ inline void MessageOptions::set_allocated_features(::google::protobuf::FeatureSe
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.features_);
}
if (value != nullptr) {
@ -18408,7 +18408,7 @@ inline void FieldOptions::set_allocated_features(::google::protobuf::FeatureSet*
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.features_);
}
if (value != nullptr) {
@ -18506,7 +18506,7 @@ inline void FieldOptions::set_allocated_feature_support(::google::protobuf::Fiel
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.feature_support_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.feature_support_);
}
if (value != nullptr) {
@ -18658,7 +18658,7 @@ inline void OneofOptions::set_allocated_features(::google::protobuf::FeatureSet*
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.features_);
}
if (value != nullptr) {
@ -18894,7 +18894,7 @@ inline void EnumOptions::set_allocated_features(::google::protobuf::FeatureSet*
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.features_);
}
if (value != nullptr) {
@ -19074,7 +19074,7 @@ inline void EnumValueOptions::set_allocated_features(::google::protobuf::Feature
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.features_);
}
if (value != nullptr) {
@ -19200,7 +19200,7 @@ inline void EnumValueOptions::set_allocated_feature_support(::google::protobuf::
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.feature_support_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.feature_support_);
}
if (value != nullptr) {
@ -19352,7 +19352,7 @@ inline void ServiceOptions::set_allocated_features(::google::protobuf::FeatureSe
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.features_);
}
if (value != nullptr) {
@ -19591,7 +19591,7 @@ inline void MethodOptions::set_allocated_features(::google::protobuf::FeatureSet
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.features_);
}
if (value != nullptr) {
@ -20441,7 +20441,7 @@ inline void FeatureSetDefaults_FeatureSetEditionDefault::set_allocated_overridab
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.overridable_features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.overridable_features_);
}
if (value != nullptr) {
@ -20539,7 +20539,7 @@ inline void FeatureSetDefaults_FeatureSetEditionDefault::set_allocated_fixed_fea
::google::protobuf::Arena* message_arena = GetArena();
::google::protobuf::internal::TSanWrite(&_impl_);
if (message_arena == nullptr) {
delete _impl_.fixed_features_;
delete reinterpret_cast<::google::protobuf::MessageLite*>(_impl_.fixed_features_);
}
if (value != nullptr) {

7
src/google/protobuf/message_lite.cc
Unescape View File

@ -50,6 +50,13 @@
namespace google {
namespace protobuf {
MessageLite* MessageLite::CopyConstruct(Arena* arena, const MessageLite& from) {
auto* data = from.GetClassData();
auto* res = data->New(arena);
data->merge_to_from(*res, from);
return res;
}
void MessageLite::DestroyInstance() {
#if defined(PROTOBUF_CUSTOM_VTABLE)
_class_data_->destroy_message(*this);

9
src/google/protobuf/message_lite.h
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@ -920,6 +920,15 @@ class PROTOBUF_EXPORT MessageLite {
return static_cast<T*>(Arena::CopyConstruct<T>(arena, &from));
}
// As above, but for fields that use base class type. Eg foreign weak fields.
static MessageLite* CopyConstruct(Arena* arena, const MessageLite& from);
PROTOBUF_ALWAYS_INLINE static Message* CopyConstruct(Arena* arena,
const Message& from) {
return reinterpret_cast<Message*>(
CopyConstruct(arena, reinterpret_cast<const MessageLite&>(from)));
}
const internal::TcParseTableBase* GetTcParseTable() const {
auto* data = GetClassData();
ABSL_DCHECK(data != nullptr);

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