- typos
- use insert instead of back inserter to make allocations more efficient
- make sure the constraint cache uses canonicalized keys to avoid
redundant work
In the standard, constraint satisfaction checking is done on the
normalized form of a constraint.
Clang instead substitutes on the non-normalized form, which causes us to
report substitution failures in template arguments or concept ids, which
is non-conforming but unavoidable without a parameter mapping
This patch normalizes before satisfaction checking. However, we preserve
concept-id nodes in the normalized form, solely for diagnostics
purposes.
This addresses https://github.com/llvm/llvm-project/issues/61811 and
related concepts conformance bugs, ideally to make the remaining
implementation of concept template parameters easier
Fixes https://github.com/llvm/llvm-project/issues/135190
Fixes https://github.com/llvm/llvm-project/issues/61811
Co-authored-by: Younan Zhang
[zyn7109@gmail.com](mailto:zyn7109@gmail.com)
---------
Co-authored-by: Younan Zhang <zyn7109@gmail.com>
In the standard, constraint satisfaction checking is done on the
normalized form of a constraint.
Clang instead substitutes on the non-normalized form, which causes us to
report substitution failures in template arguments or concept ids, which
is non-conforming but unavoidable without a parameter mapping
This patch normalizes before satisfaction checking. However, we preserve
concept-id nodes in the normalized form, solely for diagnostics
purposes.
This addresses #61811 and related concepts conformance bugs, ideally to
make the remaining implementation of concept template parameters easier
Fixes#135190
Fixes #61811
Co-authored-by: Younan Zhang <zyn7109@gmail.com>
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
This is a first pass at implementing
[P2841R7](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p2841r7.pdf).
The implementation is far from complete; however, I'm aiming to do that
in chunks, to make our lives easier.
In particular, this does not implement
- Subsumption
- Mangling
- Satisfaction checking is minimal as we should focus on #141776 first
(note that I'm currently very stuck)
FTM, release notes, status page, etc, will be updated once the feature
is more mature. Given the state of the feature, it is not yet allowed in
older language modes.
Of note:
- Mismatches between template template arguments and template template
parameters are a bit wonky. This is addressed by #130603
- We use `UnresolvedLookupExpr` to model template-id. While this is
pre-existing, I have been wondering if we want to introduce a different
OverloadExpr subclass for that. I did not make the change in this patch.
Note that PointerUnion::{is,get} have been soft deprecated in
PointerUnion.h:
// FIXME: Replace the uses of is(), get() and dyn_cast() with
// isa<T>, cast<T> and the llvm::dyn_cast<T>
I'm not touching PointerUnion::dyn_cast for now because it's a bit
complicated; we could blindly migrate it to dyn_cast_if_present, but
we should probably use dyn_cast when the operand is known to be
non-null.
Limit the #includes to the least necessary to still compile. Move the
"new" function into the .cpp file to remove the need to #include
ASTContext.h into ASTConcept.h.
Differential Revision: https://reviews.llvm.org/D159320
This reverts commit 192d69f7e65a625e344421841e731e39f80595f5.
This fixes the condition to check whether this is a situation where we
are in a recovery-expr'ed concept a little better, so we don't access an
inactive member of a union, which should make the bots happy.
Differential Revision: https://reviews.llvm.org/D134542
This reverts commit e3d14bee238b672a7a112311eefee55e142eaefc.
There are apparently a large number of crashes in libcxx and some JSON
Parser thing, so clearly this has some sort of serious issue. Reverting
so I can take some time to figure out what is going on.
Discovered by reducing a different problem, we currently assert because
we failed to make the constraint expressions not dependent, since a
RecoveryExpr cannot be transformed.
This patch fixes that, and gets reasonably nice diagnostics by
introducing a concept (hah!) of "ContainsErrors" to the Satisfaction
types, which causes us to treat the candidate as non-viable.
However, just making THAT candidate non-viable would result in choosing
the 'next best' canddiate, which can result in awkward errors, where we
start evaluating a candidate that is not intended to be selected.
Because of this, and to make diagnostics more relevant, we now just
cause the entire lookup to result in a 'no-viable-candidates'.
This means we will only emit the list of candidates, rather than any
cascading failures.
Some files still contained the old University of Illinois Open Source
Licence header. This patch replaces that with the Apache 2 with LLVM
Exception licence.
Differential Revision: https://reviews.llvm.org/D107528
We would previously try to evaluate atomic constraints of non-template functions as-is,
and since they are now unevaluated at first, this would cause incorrect evaluation (bugs #44657, #44656).
Substitute into atomic constraints of non-template functions as we would atomic constraints
of template functions, in order to rebuild the expressions in a constant-evaluated context.
Add a simple cache for constraint satisfaction results. Whether or not this simple caching
would be permitted in final C++2a is currently being discussed but it is required for
acceptable performance so we use it in the meantime, with the possibility of adding some
cache invalidation mechanisms later.
Differential Revision: https://reviews.llvm.org/D72552
Part of the C++20 concepts implementation effort.
- Associated constraints (requires clauses, currently) are now enforced when instantiating/specializing templates and when considering partial specializations and function overloads.
- Elaborated diagnostics give helpful insight as to why the constraints were not satisfied.
Phabricator: D41569
Re-commit, after fixing some memory bugs.
Part of the C++20 concepts implementation effort.
- Associated constraints (requires clauses, currently) are now enforced when instantiating/specializing templates and when considering partial specializations and function overloads.
- Elaborated diagnostics give helpful insight as to why the constraints were not satisfied.
Phabricator: D41569
