This is a major change on how we represent nested name qualifications in
the AST.
* The nested name specifier itself and how it's stored is changed. The
prefixes for types are handled within the type hierarchy, which makes
canonicalization for them super cheap, no memory allocation required.
Also translating a type into nested name specifier form becomes a no-op.
An identifier is stored as a DependentNameType. The nested name
specifier gains a lightweight handle class, to be used instead of
passing around pointers, which is similar to what is implemented for
TemplateName. There is still one free bit available, and this handle can
be used within a PointerUnion and PointerIntPair, which should keep
bit-packing aficionados happy.
* The ElaboratedType node is removed, all type nodes in which it could
previously apply to can now store the elaborated keyword and name
qualifier, tail allocating when present.
* TagTypes can now point to the exact declaration found when producing
these, as opposed to the previous situation of there only existing one
TagType per entity. This increases the amount of type sugar retained,
and can have several applications, for example in tracking module
ownership, and other tools which care about source file origins, such as
IWYU. These TagTypes are lazily allocated, in order to limit the
increase in AST size.
This patch offers a great performance benefit.
It greatly improves compilation time for
[stdexec](https://github.com/NVIDIA/stdexec). For one datapoint, for
`test_on2.cpp` in that project, which is the slowest compiling test,
this patch improves `-c` compilation time by about 7.2%, with the
`-fsyntax-only` improvement being at ~12%.
This has great results on compile-time-tracker as well:
This patch also further enables other optimziations in the future, and
will reduce the performance impact of template specialization resugaring
when that lands.
It has some other miscelaneous drive-by fixes.
About the review: Yes the patch is huge, sorry about that. Part of the
reason is that I started by the nested name specifier part, before the
ElaboratedType part, but that had a huge performance downside, as
ElaboratedType is a big performance hog. I didn't have the steam to go
back and change the patch after the fact.
There is also a lot of internal API changes, and it made sense to remove
ElaboratedType in one go, versus removing it from one type at a time, as
that would present much more churn to the users. Also, the nested name
specifier having a different API avoids missing changes related to how
prefixes work now, which could make existing code compile but not work.
How to review: The important changes are all in
`clang/include/clang/AST` and `clang/lib/AST`, with also important
changes in `clang/lib/Sema/TreeTransform.h`.
The rest and bulk of the changes are mostly consequences of the changes
in API.
PS: TagType::getDecl is renamed to `getOriginalDecl` in this patch, just
for easier to rebasing. I plan to rename it back after this lands.
Fixes#136624
Fixes https://github.com/llvm/llvm-project/issues/43179
Fixes https://github.com/llvm/llvm-project/issues/68670
Fixes https://github.com/llvm/llvm-project/issues/92757
`ASTImporterLookupTable` did use the `getPrimaryContext` function to get
the declaration context of the inserted items. This is problematic
because the primary context can change during import of AST items, most
likely if a definition of a previously not defined class is imported.
(For any record the primary context is the definition if there is one.)
The use of primary context is really not important, only for namespaces
because these can be re-opened and lookup in one namespace block is not
enough. This special search is now moved into ASTImporter instead of
relying on the lookup table.
The declaration of __builtin_va_list seems to be handled specially
by ASTContext and/or Sema. The normal AST traversal probably can
not find it, therefore it is not added to ASTImporterLookupTable.
If it is not added, errors can occur because a duplicated
VaList declaration is created at import. To fix the problem the
VaList declaration is added manually to ASTImporterLookupTable
at construction.
In special cases this declaration is inside a "invisible" 'std'
namespace that behaves the same way. This namespace must be added
to the table too.
Reviewed By: vabridgers, donat.nagy
Differential Revision: https://reviews.llvm.org/D144273
ASTImporterLookupTable did not handle correctly friend declarations
where the friend type is an UsingType (type of a declaration that
comes from an using-declaration). The problem is fixed by handling
it in the same way as a friend with TypedefType.
Reviewed By: steakhal
Differential Revision: https://reviews.llvm.org/D142607
Declaration context of template parameters of a FunctionTemplateDecl
may be different for each one parameter if the template is a
deduction guide. This case is handled correctly after this change.
Reviewed By: martong
Differential Revision: https://reviews.llvm.org/D114418
Sometimes it would be useful to see which Decl kind caused some issue,
along with the name of the concrete instance of the Decl in the source
code.
Reviewed By: martong
Differential Revision: https://reviews.llvm.org/D113668
ParmVarDecl is created with translation unit as the parent DeclContext
and later moved to the correct DeclContext. ASTImporterLookupTable
should be updated at this move.
Reviewed By: martong
Differential Revision: https://reviews.llvm.org/D103231
We found a case where Typedef Name Declarations were not being added
correctly when importing builtin types. This exposed the need for a
TypedefNameDecl visitor so these types can be added by RecordDecl and
fields.
This code is covered by the ASTImporterTest cases that use the implicit
struct __NSConstantString_tag definitions.
Thanks to @martong for the debugging assist!
Depends on D83970.
Reviewed By: martong
Differential Revision: https://reviews.llvm.org/D83992
Summary:
In most cases the FriendDecl contains the declaration of the befriended
class as a child node, so it is discovered during the recursive
visitation. However, there are cases when the befriended class is not a
child, thus it must be fetched explicitly from the FriendDecl, and only
then can we add it to the lookup table.
(Note, this does affect only CTU and does not affect LLDB, because we
cannot and do not use the ASTImporterLookupTable in LLDB.)
Reviewers: a_sidorin, a.sidorin, shafik
Subscribers: rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D62064
llvm-svn: 363062
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
Summary:
There are certain cases when normal C/C++ lookup (localUncachedLookup)
does not find AST nodes. E.g.:
Example 1:
template <class T>
struct X {
friend void foo(); // this is never found in the DC of the TU.
};
Example 2:
// The fwd decl to Foo is not found in the lookupPtr of the DC of the
// translation unit decl.
struct A { struct Foo *p; };
In these cases we create a new node instead of returning with the old one.
To fix it we create a new lookup table which holds every node and we are
not interested in any C++ specific visibility considerations.
Simply, we must know if there is an existing Decl in a given DC.
Reviewers: a_sidorin, a.sidorin
Subscribers: mgorny, rnkovacs, dkrupp, Szelethus, cfe-commits
Differential Revision: https://reviews.llvm.org/D53708
llvm-svn: 349351
