BigfootDev/flatbuffers
1
0
Fork 1
mirror of https://github.com/google/flatbuffers.git synced 2026-06-02 04:04:19 +00:00
Code Issues Packages Projects Releases Wiki Activity

Flatbuffer C++ UnpackTo optimization for vectors of non-bool bytes. (#6154)

Browse Source 
UnpackTo copies vector elements one-by-one, which can be very inefficient depending on the quality of the compiler optimizations performed. This change updates the operation for vectors of bytes that aren't enums to use 'std::copy', which is usually highly optimized.

vectors of types that are more than one byte can't be optimized in this way because of the endianness of the serialized bytes vs. the target architecture endianness.

vectors of enums can't be optimized because they are required to be static_cast into the appropriate enum type when stored in the vector.

vectors of bools can be optimized in most cases, but since the standard
allows std::vector<bool> template specialization for space-savings,
std::copy doesn't work on every implementation (looking at you
Microsoft). Thus, this optimization is skipped for vector<bool>.

For a specific example, this improves the latency of unpacking large buffers on the Hexagon DSP by about 10x.

Co-authored-by: Matthew Markwell <markwell@google.com>
This commit is contained in:
mrmarkwell
2020-10-06 10:56:45 -07:00
committed by GitHub
parent 5975658ebd
commit 08943aa26f
4 changed files with 71 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
samples/monster_generated.h
View File

@@ -580,7 +580,7 @@ inline void Monster::UnPackTo(MonsterT *_o, const flatbuffers::resolver_function
{ auto _e = mana(); _o->mana = _e; }
{ auto _e = hp(); _o->hp = _e; }
{ auto _e = name(); if (_e) _o->name = _e->str(); }
{ auto _e = inventory(); if (_e) { _o->inventory.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->inventory[_i] = _e->Get(_i); } } }
{ auto _e = inventory(); if (_e) { _o->inventory.resize(_e->size()); std::copy(_e->begin(), _e->end(), _o->inventory.begin()); } }
{ auto _e = color(); _o->color = _e; }
{ auto _e = weapons(); if (_e) { _o->weapons.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->weapons[_i] = flatbuffers::unique_ptr<MyGame::Sample::WeaponT>(_e->Get(_i)->UnPack(_resolver)); } } }
{ auto _e = equipped_type(); _o->equipped.type = _e; }

107
src/idl_gen_cpp.cpp
View File

@@ -2498,58 +2498,75 @@ class CppGenerator : public BaseGenerator {
std::string code;
switch (field.value.type.base_type) {
case BASE_TYPE_VECTOR: {
auto cpp_type = field.attributes.Lookup("cpp_type");
std::string indexing;
if (field.value.type.enum_def) {
indexing += "static_cast<" +
WrapInNameSpace(*field.value.type.enum_def) + ">(";
}
indexing += "_e->Get(_i)";
if (field.value.type.enum_def) { indexing += ")"; }
if (field.value.type.element == BASE_TYPE_BOOL) { indexing += " != 0"; }
// Generate code that pushes data from _e to _o in the form:
// for (uoffset_t i = 0; i < _e->size(); ++i) {
// _o->field.push_back(_e->Get(_i));
// }
auto name = Name(field);
if (field.value.type.element == BASE_TYPE_UTYPE) {
name = StripUnionType(Name(field));
}
auto access =
field.value.type.element == BASE_TYPE_UTYPE
? ".type"
: (field.value.type.element == BASE_TYPE_UNION ? ".value" : "");
code += "{ _o->" + name + ".resize(_e->size()); ";
code += "for (flatbuffers::uoffset_t _i = 0;";
code += " _i < _e->size(); _i++) { ";
if (cpp_type) {
// Generate code that resolves the cpp pointer type, of the form:
// if (resolver)
// (*resolver)(&_o->field, (hash_value_t)(_e));
// else
// _o->field = nullptr;
code += "//vector resolver, " + PtrType(&field) + "\n";
code += "if (_resolver) ";
code += "(*_resolver)";
code += "(reinterpret_cast<void **>(&_o->" + name + "[_i]" + access +
"), ";
code += "static_cast<flatbuffers::hash_value_t>(" + indexing + "));";
if (PtrType(&field) == "naked") {
code += " else ";
code += "_o->" + name + "[_i]" + access + " = nullptr";
} else {
// code += " else ";
// code += "_o->" + name + "[_i]" + access + " = " +
// GenTypeNativePtr(cpp_type->constant, &field, true) + "();";
code += "/* else do nothing */";
}
if (!field.value.type.enum_def && !IsBool(field.value.type.element) &&
IsOneByte(field.value.type.element)) {
// For vectors of bytes, std::copy is used to improve performance.
// This doesn't work for:
// - enum types because they have to be explicitly static_cast.
// - vectors of bool, since they are a template specialization.
// - multiple-byte types due to endianness.
code +=
"std::copy(_e->begin(), _e->end(), _o->" + name + ".begin()); }";
} else {
code += "_o->" + name + "[_i]" + access + " = ";
code += GenUnpackVal(field.value.type.VectorType(), indexing, true,
field);
std::string indexing;
if (field.value.type.enum_def) {
indexing += "static_cast<" +
WrapInNameSpace(*field.value.type.enum_def) + ">(";
}
indexing += "_e->Get(_i)";
if (field.value.type.enum_def) {
indexing += ")";
}
if (field.value.type.element == BASE_TYPE_BOOL) {
indexing += " != 0";
}
// Generate code that pushes data from _e to _o in the form:
// for (uoffset_t i = 0; i < _e->size(); ++i) {
// _o->field.push_back(_e->Get(_i));
// }
auto access =
field.value.type.element == BASE_TYPE_UTYPE
? ".type"
: (field.value.type.element == BASE_TYPE_UNION ? ".value"
: "");
code += "for (flatbuffers::uoffset_t _i = 0;";
code += " _i < _e->size(); _i++) { ";
auto cpp_type = field.attributes.Lookup("cpp_type");
if (cpp_type) {
// Generate code that resolves the cpp pointer type, of the form:
// if (resolver)
// (*resolver)(&_o->field, (hash_value_t)(_e));
// else
// _o->field = nullptr;
code += "//vector resolver, " + PtrType(&field) + "\n";
code += "if (_resolver) ";
code += "(*_resolver)";
code += "(reinterpret_cast<void **>(&_o->" + name + "[_i]" +
access + "), ";
code +=
"static_cast<flatbuffers::hash_value_t>(" + indexing + "));";
if (PtrType(&field) == "naked") {
code += " else ";
code += "_o->" + name + "[_i]" + access + " = nullptr";
} else {
// code += " else ";
// code += "_o->" + name + "[_i]" + access + " = " +
// GenTypeNativePtr(cpp_type->constant, &field, true) + "();";
code += "/* else do nothing */";
}
} else {
code += "_o->" + name + "[_i]" + access + " = ";
code += GenUnpackVal(field.value.type.VectorType(), indexing, true,
field);
}
code += "; } }";
}
code += "; } }";
break;
}
case BASE_TYPE_UTYPE: {

8
tests/cpp17/generated_cpp17/monster_test_generated.h
View File

@@ -2298,7 +2298,7 @@ inline void Monster::UnPackTo(MonsterT *_o, const flatbuffers::resolver_function
{ auto _e = mana(); _o->mana = _e; }
{ auto _e = hp(); _o->hp = _e; }
{ auto _e = name(); if (_e) _o->name = _e->str(); }
{ auto _e = inventory(); if (_e) { _o->inventory.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->inventory[_i] = _e->Get(_i); } } }
{ auto _e = inventory(); if (_e) { _o->inventory.resize(_e->size()); std::copy(_e->begin(), _e->end(), _o->inventory.begin()); } }
{ auto _e = color(); _o->color = _e; }
{ auto _e = test_type(); _o->test.type = _e; }
{ auto _e = test(); if (_e) _o->test.value = MyGame::Example::AnyUnion::UnPack(_e, test_type(), _resolver); }
@@ -2306,7 +2306,7 @@ inline void Monster::UnPackTo(MonsterT *_o, const flatbuffers::resolver_function
{ auto _e = testarrayofstring(); if (_e) { _o->testarrayofstring.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayofstring[_i] = _e->Get(_i)->str(); } } }
{ auto _e = testarrayoftables(); if (_e) { _o->testarrayoftables.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayoftables[_i] = std::unique_ptr<MyGame::Example::MonsterT>(_e->Get(_i)->UnPack(_resolver)); } } }
{ auto _e = enemy(); if (_e) _o->enemy = std::unique_ptr<MyGame::Example::MonsterT>(_e->UnPack(_resolver)); }
{ auto _e = testnestedflatbuffer(); if (_e) { _o->testnestedflatbuffer.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testnestedflatbuffer[_i] = _e->Get(_i); } } }
{ auto _e = testnestedflatbuffer(); if (_e) { _o->testnestedflatbuffer.resize(_e->size()); std::copy(_e->begin(), _e->end(), _o->testnestedflatbuffer.begin()); } }
{ auto _e = testempty(); if (_e) _o->testempty = std::unique_ptr<MyGame::Example::StatT>(_e->UnPack(_resolver)); }
{ auto _e = testbool(); _o->testbool = _e; }
{ auto _e = testhashs32_fnv1(); _o->testhashs32_fnv1 = _e; }
@@ -2324,7 +2324,7 @@ if (_resolver) (*_resolver)(reinterpret_cast<void **>(&_o->testhashu32_fnv1a), s
{ auto _e = testf3(); _o->testf3 = _e; }
{ auto _e = testarrayofstring2(); if (_e) { _o->testarrayofstring2.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayofstring2[_i] = _e->Get(_i)->str(); } } }
{ auto _e = testarrayofsortedstruct(); if (_e) { _o->testarrayofsortedstruct.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayofsortedstruct[_i] = *_e->Get(_i); } } }
{ auto _e = flex(); if (_e) { _o->flex.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->flex[_i] = _e->Get(_i); } } }
{ auto _e = flex(); if (_e) { _o->flex.resize(_e->size()); std::copy(_e->begin(), _e->end(), _o->flex.begin()); } }
{ auto _e = test5(); if (_e) { _o->test5.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->test5[_i] = *_e->Get(_i); } } }
{ auto _e = vector_of_longs(); if (_e) { _o->vector_of_longs.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->vector_of_longs[_i] = _e->Get(_i); } } }
{ auto _e = vector_of_doubles(); if (_e) { _o->vector_of_doubles.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->vector_of_doubles[_i] = _e->Get(_i); } } }
@@ -2478,7 +2478,7 @@ inline void TypeAliases::UnPackTo(TypeAliasesT *_o, const flatbuffers::resolver_
{ auto _e = u64(); _o->u64 = _e; }
{ auto _e = f32(); _o->f32 = _e; }
{ auto _e = f64(); _o->f64 = _e; }
{ auto _e = v8(); if (_e) { _o->v8.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->v8[_i] = _e->Get(_i); } } }
{ auto _e = v8(); if (_e) { _o->v8.resize(_e->size()); std::copy(_e->begin(), _e->end(), _o->v8.begin()); } }
{ auto _e = vf64(); if (_e) { _o->vf64.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->vf64[_i] = _e->Get(_i); } } }
}

8
tests/monster_test_generated.h
View File

@@ -2580,7 +2580,7 @@ inline void Monster::UnPackTo(MonsterT *_o, const flatbuffers::resolver_function
{ auto _e = mana(); _o->mana = _e; }
{ auto _e = hp(); _o->hp = _e; }
{ auto _e = name(); if (_e) _o->name = _e->str(); }
{ auto _e = inventory(); if (_e) { _o->inventory.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->inventory[_i] = _e->Get(_i); } } }
{ auto _e = inventory(); if (_e) { _o->inventory.resize(_e->size()); std::copy(_e->begin(), _e->end(), _o->inventory.begin()); } }
{ auto _e = color(); _o->color = _e; }
{ auto _e = test_type(); _o->test.type = _e; }
{ auto _e = test(); if (_e) _o->test.value = MyGame::Example::AnyUnion::UnPack(_e, test_type(), _resolver); }
@@ -2588,7 +2588,7 @@ inline void Monster::UnPackTo(MonsterT *_o, const flatbuffers::resolver_function
{ auto _e = testarrayofstring(); if (_e) { _o->testarrayofstring.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayofstring[_i] = _e->Get(_i)->str(); } } }
{ auto _e = testarrayoftables(); if (_e) { _o->testarrayoftables.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayoftables[_i] = flatbuffers::unique_ptr<MyGame::Example::MonsterT>(_e->Get(_i)->UnPack(_resolver)); } } }
{ auto _e = enemy(); if (_e) _o->enemy = flatbuffers::unique_ptr<MyGame::Example::MonsterT>(_e->UnPack(_resolver)); }
{ auto _e = testnestedflatbuffer(); if (_e) { _o->testnestedflatbuffer.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testnestedflatbuffer[_i] = _e->Get(_i); } } }
{ auto _e = testnestedflatbuffer(); if (_e) { _o->testnestedflatbuffer.resize(_e->size()); std::copy(_e->begin(), _e->end(), _o->testnestedflatbuffer.begin()); } }
{ auto _e = testempty(); if (_e) _o->testempty = flatbuffers::unique_ptr<MyGame::Example::StatT>(_e->UnPack(_resolver)); }
{ auto _e = testbool(); _o->testbool = _e; }
{ auto _e = testhashs32_fnv1(); _o->testhashs32_fnv1 = _e; }
@@ -2606,7 +2606,7 @@ if (_resolver) (*_resolver)(reinterpret_cast<void **>(&_o->testhashu32_fnv1a), s
{ auto _e = testf3(); _o->testf3 = _e; }
{ auto _e = testarrayofstring2(); if (_e) { _o->testarrayofstring2.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayofstring2[_i] = _e->Get(_i)->str(); } } }
{ auto _e = testarrayofsortedstruct(); if (_e) { _o->testarrayofsortedstruct.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayofsortedstruct[_i] = *_e->Get(_i); } } }
{ auto _e = flex(); if (_e) { _o->flex.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->flex[_i] = _e->Get(_i); } } }
{ auto _e = flex(); if (_e) { _o->flex.resize(_e->size()); std::copy(_e->begin(), _e->end(), _o->flex.begin()); } }
{ auto _e = test5(); if (_e) { _o->test5.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->test5[_i] = *_e->Get(_i); } } }
{ auto _e = vector_of_longs(); if (_e) { _o->vector_of_longs.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->vector_of_longs[_i] = _e->Get(_i); } } }
{ auto _e = vector_of_doubles(); if (_e) { _o->vector_of_doubles.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->vector_of_doubles[_i] = _e->Get(_i); } } }
@@ -2760,7 +2760,7 @@ inline void TypeAliases::UnPackTo(TypeAliasesT *_o, const flatbuffers::resolver_
{ auto _e = u64(); _o->u64 = _e; }
{ auto _e = f32(); _o->f32 = _e; }
{ auto _e = f64(); _o->f64 = _e; }
{ auto _e = v8(); if (_e) { _o->v8.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->v8[_i] = _e->Get(_i); } } }
{ auto _e = v8(); if (_e) { _o->v8.resize(_e->size()); std::copy(_e->begin(), _e->end(), _o->v8.begin()); } }
{ auto _e = vf64(); if (_e) { _o->vf64.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->vf64[_i] = _e->Get(_i); } } }
}