Files
clang-p2996/flang/lib/Parser/tools.cpp
Peter Klausler cd03e96f00 [flang] Add & use a better visit() (take 2)
Adds flang/include/flang/Common/log2-visit.h, which defines
a Fortran::common::visit() template function that is a drop-in
replacement for std::visit().  Modifies most use sites in
the front-end and runtime to use common::visit().

The C++ standard mandates that std::visit() have O(1) execution
time, which forces implementations to build dispatch tables.
This new common::visit() is O(log2 N) in the number of alternatives
in a variant<>, but that N tends to be small and so this change
produces a fairly significant improvement in compiler build
memory requirements, a 5-10% improvement in compiler build time,
and a small improvement in compiler execution time.

Building with -DFLANG_USE_STD_VISIT causes common::visit()
to be an alias for std::visit().

Calls to common::visit() with multiple variant arguments
are referred to std::visit(), pending further work.

This change is enabled only for GCC builds with GCC >= 9;
an earlier attempt (D122441) ran into bugs in some versions of
clang and was reverted rather than simply disabled; and it is
not well tested with MSVC. In non-GCC and older GCC builds,
common::visit() is simply an alias for std::visit().
2022-04-16 16:00:48 -07:00

174 lines
5.5 KiB
C++

//===-- lib/Parser/tools.cpp ----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "flang/Parser/tools.h"
namespace Fortran::parser {
const Name &GetLastName(const Name &x) { return x; }
const Name &GetLastName(const StructureComponent &x) {
return GetLastName(x.component);
}
const Name &GetLastName(const DataRef &x) {
return common::visit(
common::visitors{
[](const Name &name) -> const Name & { return name; },
[](const common::Indirection<StructureComponent> &sc)
-> const Name & { return GetLastName(sc.value()); },
[](const common::Indirection<ArrayElement> &sc) -> const Name & {
return GetLastName(sc.value().base);
},
[](const common::Indirection<CoindexedNamedObject> &ci)
-> const Name & { return GetLastName(ci.value().base); },
},
x.u);
}
const Name &GetLastName(const Substring &x) {
return GetLastName(std::get<DataRef>(x.t));
}
const Name &GetLastName(const Designator &x) {
return common::visit(
[](const auto &y) -> const Name & { return GetLastName(y); }, x.u);
}
const Name &GetLastName(const ProcComponentRef &x) {
return GetLastName(x.v.thing);
}
const Name &GetLastName(const ProcedureDesignator &x) {
return common::visit(
[](const auto &y) -> const Name & { return GetLastName(y); }, x.u);
}
const Name &GetLastName(const Call &x) {
return GetLastName(std::get<ProcedureDesignator>(x.t));
}
const Name &GetLastName(const FunctionReference &x) { return GetLastName(x.v); }
const Name &GetLastName(const Variable &x) {
return common::visit(
[](const auto &indirection) -> const Name & {
return GetLastName(indirection.value());
},
x.u);
}
const Name &GetLastName(const AllocateObject &x) {
return common::visit(
[](const auto &y) -> const Name & { return GetLastName(y); }, x.u);
}
const Name &GetFirstName(const Name &x) { return x; }
const Name &GetFirstName(const StructureComponent &x) {
return GetFirstName(x.base);
}
const Name &GetFirstName(const DataRef &x) {
return common::visit(
common::visitors{
[](const Name &name) -> const Name & { return name; },
[](const common::Indirection<StructureComponent> &sc)
-> const Name & { return GetFirstName(sc.value()); },
[](const common::Indirection<ArrayElement> &sc) -> const Name & {
return GetFirstName(sc.value().base);
},
[](const common::Indirection<CoindexedNamedObject> &ci)
-> const Name & { return GetFirstName(ci.value().base); },
},
x.u);
}
const Name &GetFirstName(const Substring &x) {
return GetFirstName(std::get<DataRef>(x.t));
}
const Name &GetFirstName(const Designator &x) {
return common::visit(
[](const auto &y) -> const Name & { return GetFirstName(y); }, x.u);
}
const Name &GetFirstName(const ProcComponentRef &x) {
return GetFirstName(x.v.thing);
}
const Name &GetFirstName(const ProcedureDesignator &x) {
return common::visit(
[](const auto &y) -> const Name & { return GetFirstName(y); }, x.u);
}
const Name &GetFirstName(const Call &x) {
return GetFirstName(std::get<ProcedureDesignator>(x.t));
}
const Name &GetFirstName(const FunctionReference &x) {
return GetFirstName(x.v);
}
const Name &GetFirstName(const Variable &x) {
return common::visit(
[](const auto &indirect) -> const Name & {
return GetFirstName(indirect.value());
},
x.u);
}
const CoindexedNamedObject *GetCoindexedNamedObject(const DataRef &base) {
return common::visit(
common::visitors{
[](const Name &) -> const CoindexedNamedObject * { return nullptr; },
[](const common::Indirection<CoindexedNamedObject> &x)
-> const CoindexedNamedObject * { return &x.value(); },
[](const auto &x) -> const CoindexedNamedObject * {
return GetCoindexedNamedObject(x.value().base);
},
},
base.u);
}
const CoindexedNamedObject *GetCoindexedNamedObject(
const Designator &designator) {
return common::visit(
common::visitors{
[](const DataRef &x) -> const CoindexedNamedObject * {
return GetCoindexedNamedObject(x);
},
[](const Substring &x) -> const CoindexedNamedObject * {
return GetCoindexedNamedObject(std::get<DataRef>(x.t));
},
},
designator.u);
}
const CoindexedNamedObject *GetCoindexedNamedObject(const Variable &variable) {
return common::visit(
common::visitors{
[](const common::Indirection<Designator> &designator)
-> const CoindexedNamedObject * {
return GetCoindexedNamedObject(designator.value());
},
[](const auto &) -> const CoindexedNamedObject * { return nullptr; },
},
variable.u);
}
const CoindexedNamedObject *GetCoindexedNamedObject(
const AllocateObject &allocateObject) {
return common::visit(
common::visitors{
[](const StructureComponent &x) -> const CoindexedNamedObject * {
return GetCoindexedNamedObject(x.base);
},
[](const auto &) -> const CoindexedNamedObject * { return nullptr; },
},
allocateObject.u);
}
} // namespace Fortran::parser