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This patch stops storing a source range in `CXXOperatorCallExpr` and
keeps only the begin location.
This change allows us to retain the optimization #141058 when switching
to 64-bit source locations.
Performance results:
https://llvm-compile-time-tracker.com/compare.php?from=0588e8188c647460b641b09467fe6b13a8d510d5&to=5958f83476a8b8ba97936f262396d3ff98fb1662&stat=instructions:u
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Due to we didn't consider (this, auto) information when setting abbrev
for calls, we use incorrect format for calls, which cause crashes.
From
https://github.com/llvm/llvm-project/issues/118137
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This removes the delayed typo correction functionality from Clang
(regular typo correction still remains) due to fragility of the
solution.
An RFC was posted here:
https://discourse.llvm.org/t/rfc-removing-support-for-delayed-typo-correction/86631
and while that RFC was asking for folks to consider stepping up to be
maintainers, and we did have a few new contributors show some interest,
experiments show that it's likely worth it to remove this functionality
entirely and focus efforts on improving regular typo correction.
This removal fixes ~20 open issues (quite possibly more), improves
compile time performance by roughly .3-.4%
(https://llvm-compile-time-tracker.com/?config=Overview&stat=instructions%3Au&remote=AaronBallman&sortBy=date),
and does not appear to regress diagnostic behavior in a way we wouldn't
find acceptable.
Fixes #142457
Fixes #139913
Fixes #138850
Fixes #137867
Fixes #137860
Fixes #107840
Fixes #93308
Fixes #69470
Fixes #59391
Fixes #58172
Fixes #46215
Fixes #45915
Fixes #45891
Fixes #44490
Fixes #36703
Fixes #32903
Fixes #23312
Fixes #69874
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This patch reduces the size of several AST nodes by moving some fields
into the free bitfield space in the base `Stmt` class:
* `CXXForRangeStmt`: 96 → 88 bytes
* `ChooseExpr`: 56 → 48 bytes
* `ArrayTypeTraitExpr`: 56 → 48 bytes
* `ExpressionTraitExpr`: 40 → 32 bytes
* `CXXFoldExpr`: 64 → 56 bytes
* `ShuffleExpr`: 40 → 32 bytes
* `PackIndexingExpr`: 48 → 40 bytes
There are no noticeable memory savings (`Expr/Stmt` memory usage
125,824,496 vs 125,826,336 bytes for `SemaExpr.cpp`) in my testing,
likely because these node types are not among the most common in typical
ASTs.
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These are identified by misc-include-cleaner. I've filtered out those
that break builds. Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.
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The bulk of the changes are in `CallExpr`
We cache Begin/End source locs in the trailing objects, in the space
left by making the offset to the trailing objects static.
We also set a flag to indicate that we are calling an explicit object
member function, further reducing the cost of getBeginLoc.
Fixes #140876
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This fixes a PCM non-determinism regression reported here:
https://github.com/llvm/llvm-project/pull/134560#issuecomment-2797744370
There was a bit in `SubstNonTypeTemplateParmPackExpr` which we missed to
serialize, and that bit eventually propagates to
`SubstNonTypeTemplateParmExpr`.
As a drive by, improve serialization for PackIndex on
SubstNonTypeTemplateParmExpr by using the newly introduced
UnsignedOrNone helpers.
There are no release notes since this regression was never released.
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This is a basic implementation of P2719: "Type-aware allocation and
deallocation functions" described at http://wg21.link/P2719
The proposal includes some more details but the basic change in
functionality is the addition of support for an additional implicit
parameter in operators `new` and `delete` to act as a type tag. Tag is
of type `std::type_identity<T>` where T is the concrete type being
allocated. So for example, a custom type specific allocator for `int`
say can be provided by the declaration of
void *operator new(std::type_identity<int>, size_t, std::align_val_t);
void operator delete(std::type_identity<int>, void*, size_t, std::align_val_t);
However this becomes more powerful by specifying templated declarations,
for example
template <typename T> void *operator new(std::type_identity<T>, size_t, std::align_val_t);
template <typename T> void operator delete(std::type_identity<T>, void*, size_t, std::align_val_t););
Where the operators being resolved will be the concrete type being
operated over (NB. A completely unconstrained global definition as above
is not recommended as it triggers many problems similar to a general
override of the global operators).
These type aware operators can be declared as either free functions or
in class, and can be specified with or without the other implicit
parameters, with overload resolution performed according to the existing
standard parameter prioritisation, only with type parameterised
operators having higher precedence than non-type aware operators. The
only exception is destroying_delete which for reasons discussed in the
paper we do not support type-aware variants by default.
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This fixes a couple of mistakes introduced when merging
https://github.com/llvm/llvm-project/pull/132748
Fixes msan failure reported here:
https://github.com/llvm/llvm-project/pull/132748#issuecomment-2781105225
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std::optional<unsigned> (#134142)
This introduces a new class 'UnsignedOrNone', which models a lite
version of `std::optional<unsigned>`, but has the same size as
'unsigned'.
This replaces most uses of `std::optional<unsigned>`, and similar
schemes utilizing 'int' and '-1' as sentinel.
Besides the smaller size advantage, this is simpler to serialize, as its
internal representation is a single unsigned int as well.
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This was added in OpenACC PR #511 in the 3.4 branch. From an AST/Sema
perspective this is pretty trivial as the infrastructure for 'if'
already exists, however the atomic construct needed to be taught to take
clauses. This patch does that and adds some testing to do so.
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Introduce a trait to determine the number of bindings that would be
produced by
```cpp
auto [...p] = expr;
```
This is necessary to implement P2300
(https://eel.is/c++draft/exec#snd.concepts-5), but can also be used to
implement a general get<N> function that supports aggregates
`__builtin_structured_binding_size` is a unary type trait that evaluates
to the number of bindings in a decomposition
If the argument cannot be decomposed, a sfinae-friendly error is
produced.
A type is considered a valid tuple if `std::tuple_size_v<T>` is a valid
expression, even if there is no valid `std::tuple_element`
specialization or suitable `get` function for that type.
Fixes #46049
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Implements GCC's constexpr string ASM extension
https://gcc.gnu.org/onlinedocs/gcc/Asm-constexprs.html
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This statement level construct takes no clauses and has no associated
statement, and simply labels a number of array elements as valid for
caching. The implementation here is pretty simple, but it is a touch of
a special case for parsing, so the parsing code reflects that.
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This patch allows using fpfeatures pragmas with __builtin_convertvector:
- added TrailingObjects with FPOptionsOverride and methods for handling
it to ConvertVectorExpr
- added support for codegen, node dumping, and serialization of
fpfeatures contained in ConvertVectorExpr
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FunctionParmPackExpr (#125394)
This merges the functionality of ResolvedUnexpandedPackExpr into
FunctionParmPackExpr. I also added a test to show that
https://github.com/llvm/llvm-project/issues/125103 should be fixed with
this. I put the removal of ResolvedUnexpandedPackExpr in its own commit.
Let me know what you think.
Fixes #125103
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This patch was reviewed and approved here:
https://github.com/llvm/llvm-project/pull/119891
However it has been reverted here:
https://github.com/alejandro-alvarez-sonarsource/llvm-project/commit/083df25dc256154cccbc0e127d79fbac4d0583c5
due to a build issue here:
https://lab.llvm.org/buildbot/#/builders/51/builds/10694
This patch is reintroducing the support.
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This reverts commit 070f84ebc89b11df616a83a56df9ac56efbab783.
Buildbot failure:
https://lab.llvm.org/buildbot/#/builders/51/builds/10694
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Implement basic parsing and semantic support for `#pragma omp stripe`
constuct introduced in
https://www.openmp.org/wp-content/uploads/[OpenMP-API-Specification-6-0.pdf](https://www.openmp.org/wp-content/uploads/OpenMP-API-Specification-6-0.pdf),
section 11.7.
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The atomic construct is a particularly complicated one. The directive
itself is pretty simple, it has 5 options for the 'atomic-clause'.
However, the associated statement is fairly complicated.
'read' accepts:
v = x;
'write' accepts:
x = expr;
'update' (or no clause) accepts:
x++;
x--;
++x;
--x;
x binop= expr;
x = x binop expr;
x = expr binop x;
'capture' accepts either a compound statement, or:
v = x++;
v = x--;
v = ++x;
v = --x;
v = x binop= expr;
v = x = x binop expr;
v = x = expr binop x;
IF 'capture' has a compound statement, it accepts:
{v = x; x binop= expr; }
{x binop= expr; v = x; }
{v = x; x = x binop expr; }
{v = x; x = expr binop x; }
{x = x binop expr ;v = x; }
{x = expr binop x; v = x; }
{v = x; x = expr; }
{v = x; x++; }
{v = x; ++x; }
{x++; v = x; }
{++x; v = x; }
{v = x; x--; }
{v = x; --x; }
{x--; v = x; }
{--x; v = x; }
While these are all quite complicated, there is a significant amount
of similarity between the 'capture' and 'update' lists, so this patch
reuses a lot of the same functions.
This patch implements the entirety of 'atomic', creating a new Sema file
for the sema for it, as it is fairly sizable.
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This is an implementation of P1061 Structure Bindings Introduce a Pack
without the ability to use packs outside of templates. There is a couple
of ways the AST could have been sliced so let me know what you think.
The only part of this change that I am unsure of is the
serialization/deserialization stuff. I followed the implementation of
other Exprs, but I do not really know how it is tested. Thank you for
your time considering this.
---------
Co-authored-by: Yanzuo Liu <zwuis@outlook.com>
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Note that PointerUnion::dyn_cast has 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>
Literal migration would result in dyn_cast_if_present (see the
definition of PointerUnion::dyn_cast), but this patch uses dyn_cast
because we expect DetailRecord to be nonnull.
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A SYCL kernel entry point function is a non-member function or a static
member function declared with the `sycl_kernel_entry_point` attribute.
Such functions define a pattern for an offload kernel entry point
function to be generated to enable execution of a SYCL kernel on a
device. A SYCL library implementation orchestrates the invocation of
these functions with corresponding SYCL kernel arguments in response to
calls to SYCL kernel invocation functions specified by the SYCL 2020
specification.
The offload kernel entry point function (sometimes referred to as the
SYCL kernel caller function) is generated from the SYCL kernel entry
point function by a transformation of the function parameters followed
by a transformation of the function body to replace references to the
original parameters with references to the transformed ones. Exactly how
parameters are transformed will be explained in a future change that
implements non-trivial transformations. For now, it suffices to state
that a given parameter of the SYCL kernel entry point function may be
transformed to multiple parameters of the offload kernel entry point as
needed to satisfy offload kernel argument passing requirements.
Parameters that are decomposed in this way are reconstituted as local
variables in the body of the generated offload kernel entry point
function.
For example, given the following SYCL kernel entry point function
definition:
```
template<typename KernelNameType, typename KernelType>
[[clang::sycl_kernel_entry_point(KernelNameType)]]
void sycl_kernel_entry_point(KernelType kernel) {
kernel();
}
```
and the following call:
```
struct Kernel {
int dm1;
int dm2;
void operator()() const;
};
Kernel k;
sycl_kernel_entry_point<class kernel_name>(k);
```
the corresponding offload kernel entry point function that is generated
might look as follows (assuming `Kernel` is a type that requires
decomposition):
```
void offload_kernel_entry_point_for_kernel_name(int dm1, int dm2) {
Kernel kernel{dm1, dm2};
kernel();
}
```
Other details of the generated offload kernel entry point function, such
as its name and calling convention, are implementation details that need
not be reflected in the AST and may differ across target devices. For
that reason, only the transformation described above is represented in
the AST; other details will be filled in during code generation.
These transformations are represented using new AST nodes introduced
with this change. `OutlinedFunctionDecl` holds a sequence of
`ImplicitParamDecl` nodes and a sequence of statement nodes that
correspond to the transformed parameters and function body.
`SYCLKernelCallStmt` wraps the original function body and associates it
with an `OutlinedFunctionDecl` instance. For the example above, the AST
generated for the `sycl_kernel_entry_point<kernel_name>` specialization
would look as follows:
```
FunctionDecl 'sycl_kernel_entry_point<kernel_name>(Kernel)'
TemplateArgument type 'kernel_name'
TemplateArgument type 'Kernel'
ParmVarDecl kernel 'Kernel'
SYCLKernelCallStmt
CompoundStmt
<original statements>
OutlinedFunctionDecl
ImplicitParamDecl 'dm1' 'int'
ImplicitParamDecl 'dm2' 'int'
CompoundStmt
VarDecl 'kernel' 'Kernel'
<initialization of 'kernel' with 'dm1' and 'dm2'>
<transformed statements with redirected references of 'kernel'>
```
Any ODR-use of the SYCL kernel entry point function will (with future
changes) suffice for the offload kernel entry point to be emitted. An
actual call to the SYCL kernel entry point function will result in a
call to the function. However, evaluation of a `SYCLKernelCallStmt`
statement is a no-op, so such calls will have no effect other than to
trigger emission of the offload kernel entry point.
Additionally, as a related change inspired by code review feedback,
these changes disallow use of the `sycl_kernel_entry_point` attribute
with functions defined with a _function-try-block_. The SYCL 2020
specification prohibits the use of C++ exceptions in device functions.
Even if exceptions were not prohibited, it is unclear what the semantics
would be for an exception that escapes the SYCL kernel entry point
function; the boundary between host and device code could be an implicit
noexcept boundary that results in program termination if violated, or
the exception could perhaps be propagated to host code via the SYCL
library. Pending support for C++ exceptions in device code and clear
semantics for handling them at the host-device boundary, this change
makes use of the `sycl_kernel_entry_point` attribute with a function
defined with a _function-try-block_ an error.
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This executable construct has a larger list of clauses than some of the
others, plus has some additional restrictions. This patch implements
the AST node, plus the 'cannot be the body of a if, while, do, switch,
or label' statement restriction. Future patches will handle the
rest of the restrictions, which are based on clauses.
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The 'set' construct is another fairly simple one, it doesn't have an
associated statement and only a handful of allowed clauses. This patch
implements it and all the rules for it, allowing 3 of its for clauses.
The only exception is default_async, which will be implemented in a
future patch, because it isn't just being enabled, it needs a complete
new implementation.
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These two constructs are very simple and similar, and only support 3
different clauses, two of which are already implemented. This patch
adds AST nodes for both constructs, and leaves the device_num clause
unimplemented, but enables the other two.
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The arguments to this are the same as for the 'wait' clause, so this
reuses all of that infrastructure. So all this has to do is support a
pair of clauses that are already implemented (if and async), plus create
an AST node. This patch does so, and adds proper testing.
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These constructs are all very similar and closely related, so this patch
creates the AST nodes for them, serialization, printing/etc.
Additionally the restrictions are all added as tests/todos in the tests,
as those will have to be implemented once we get those clauses implemented.
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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.
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Substituting into pack indexing types/expressions can still result in
unexpanded types/expressions, such as `PackIndexingType` or
`PackIndexingExpr`. To handle these cases correctly, we should defer the
pack size checks to the next round of transformation, when the patterns
can be fully expanded.
To that end, the `FullySubstituted` flag is now necessary for computing
the dependencies of `PackIndexingExprs`. Conveniently, this flag can
also represent the prior `ExpandsToEmpty` status with an additional
emptiness check. Therefore, I converted all stored flags to use
`FullySubstituted`.
Fixes https://github.com/llvm/llvm-project/issues/116105
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Combined constructs (OpenACC 3.3 section 2.11) are a short-cut for
writing a `loop` construct immediately inside of a `compute` construct.
However, this interaction requires we do additional work to ensure that
we get the semantics between the two correct, as well as diagnostics.
This patch adds the semantic analysis for the constructs (but no
clauses), as well as the AST nodes.
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After implementing 'loop', we determined that the link to its parent
only ever uses the type, not the construct itself. This patch removes
it, as it is both a waste and causes problems with serialization.
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This patch removes `ASTWriter::Context` and starts passing `ASTContext
&` explicitly to functions that actually need it. This is a
non-functional change with the end-goal of being able to write
lightweight PCM files with no `ASTContext` at all.
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Fixes #101863
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The 'tile' clause shares quite a bit of the rules with 'collapse', so a
followup patch will add those tests/behaviors. This patch deals with
adding the AST node.
The 'tile' clause takes a series of integer constant expressions, or *.
The asterisk is now represented by a new OpenACCAsteriskSizeExpr node,
else this clause is very similar to others.
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HLSL output parameters are denoted with the `inout` and `out` keywords
in the function declaration. When an argument to an output parameter is
constructed a temporary value is constructed for the argument.
For `inout` pamameters the argument is initialized via copy-initialization
from the argument lvalue expression to the parameter type. For `out`
parameters the argument is not initialized before the call.
In both cases on return of the function the temporary value is written
back to the argument lvalue expression through an implicit assignment
binary operator with casting as required.
This change introduces a new HLSLOutArgExpr ast node which represents
the output argument behavior. The OutArgExpr has three defined children:
- An OpaqueValueExpr of the argument lvalue expression.
- An OpaqueValueExpr of the copy-initialized parameter.
- A BinaryOpExpr assigning the first with the value of the second.
Fixes #87526
---------
Co-authored-by: Damyan Pepper <damyanp@microsoft.com>
Co-authored-by: John McCall <rjmccall@gmail.com>
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Introduce "-fsanitize-undefined-ignore-overflow-pattern=" which can
be used to disable sanitizer instrumentation for common overflow-dependent
code patterns.
For a wide selection of projects, proper overflow sanitization could
help catch bugs and solve security vulnerabilities. Unfortunately, in
some cases the integer overflow sanitizers are too noisy for their users
and are often left disabled. Providing users with a method to disable
sanitizer instrumentation of common patterns could mean more projects
actually utilize the sanitizers in the first place.
One such project that has opted to not use integer overflow (or
truncation) sanitizers is the Linux Kernel. There has been some
discussion[1] recently concerning mitigation strategies for unexpected
arithmetic overflow. This discussion is still ongoing and a succinct
article[2] accurately sums up the discussion. In summary, many Kernel
developers do not want to introduce more arithmetic wrappers when
most developers understand the code patterns as they are.
Patterns like:
if (base + offset < base) { ... }
or
while (i--) { ... }
or
#define SOME -1UL
are extremely common in a code base like the Linux Kernel. It is
perhaps too much to ask of kernel developers to use arithmetic wrappers
in these cases. For example:
while (wrapping_post_dec(i)) { ... }
which wraps some builtin would not fly. This would incur too many
changes to existing code; the code churn would be too much, at least too
much to justify turning on overflow sanitizers.
Currently, this commit tackles three pervasive idioms:
1. "if (a + b < a)" or some logically-equivalent re-ordering like "if (a > b + a)"
2. "while (i--)" (for unsigned) a post-decrement always overflows here
3. "-1UL, -2UL, etc" negation of unsigned constants will always overflow
The patterns that are excluded can be chosen from the following list:
- add-overflow-test
- post-decr-while
- negated-unsigned-const
These can be enabled with a comma-separated list:
-fsanitize-undefined-ignore-overflow-pattern=add-overflow-test,negated-unsigned-const
"all" or "none" may also be used to specify that all patterns should be
excluded or that none should be.
[1] https://lore.kernel.org/all/202404291502.612E0A10@keescook/
[2] https://lwn.net/Articles/979747/
CCs: @efriedma-quic @kees @jyknight @fmayer @vitalybuka
Signed-off-by: Justin Stitt <justinstitt@google.com>
Co-authored-by: Bill Wendling <morbo@google.com>
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This reverts commit 9a666deecb9ff6ca3a6b12e6c2877e19b74b54da.
Reason: broke buildbots
e.g., fork-ubsan.test started failing at
https://lab.llvm.org/buildbot/#/builders/66/builds/2819/steps/9/logs/stdio
Clang :: CodeGen/compound-assign-overflow.c
Clang :: CodeGen/sanitize-atomic-int-overflow.c
started failing with https://lab.llvm.org/buildbot/#/builders/52/builds/1570
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Introduce "-fsanitize-overflow-pattern-exclusion=" which can be used to
disable sanitizer instrumentation for common overflow-dependent code
patterns.
For a wide selection of projects, proper overflow sanitization could
help catch bugs and solve security vulnerabilities. Unfortunately, in
some cases the integer overflow sanitizers are too noisy for their users
and are often left disabled. Providing users with a method to disable
sanitizer instrumentation of common patterns could mean more projects
actually utilize the sanitizers in the first place.
One such project that has opted to not use integer overflow (or
truncation) sanitizers is the Linux Kernel. There has been some
discussion[1] recently concerning mitigation strategies for unexpected
arithmetic overflow. This discussion is still ongoing and a succinct
article[2] accurately sums up the discussion. In summary, many Kernel
developers do not want to introduce more arithmetic wrappers when
most developers understand the code patterns as they are.
Patterns like:
if (base + offset < base) { ... }
or
while (i--) { ... }
or
#define SOME -1UL
are extremely common in a code base like the Linux Kernel. It is
perhaps too much to ask of kernel developers to use arithmetic wrappers
in these cases. For example:
while (wrapping_post_dec(i)) { ... }
which wraps some builtin would not fly. This would incur too many
changes to existing code; the code churn would be too much, at least too
much to justify turning on overflow sanitizers.
Currently, this commit tackles three pervasive idioms:
1. "if (a + b < a)" or some logically-equivalent re-ordering like "if (a > b + a)"
2. "while (i--)" (for unsigned) a post-decrement always overflows here
3. "-1UL, -2UL, etc" negation of unsigned constants will always overflow
The patterns that are excluded can be chosen from the following list:
- add-overflow-test
- post-decr-while
- negated-unsigned-const
These can be enabled with a comma-separated list:
-fsanitize-overflow-pattern-exclusion=add-overflow-test,negated-unsigned-const
"all" or "none" may also be used to specify that all patterns should be
excluded or that none should be.
[1] https://lore.kernel.org/all/202404291502.612E0A10@keescook/
[2] https://lwn.net/Articles/979747/
CCs: @efriedma-quic @kees @jyknight @fmayer @vitalybuka
Signed-off-by: Justin Stitt <justinstitt@google.com>
Co-authored-by: Bill Wendling <morbo@google.com>
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This is a minimal patch to support parsing for "omp assume" directives.
These are meant to be hints to a compiler's optimisers: as such, it is
legitimate (if not very useful) to ignore them. The patch builds on top
of the existing support for "omp assumes" directives (note spelling!).
Unlike the "omp [begin/end] assumes" directives, "omp assume" is
associated with a compound statement, i.e. it can appear within a
function. The "holds" assumption could (theoretically) be mapped onto
the existing builtin "__builtin_assume", though the latter applies to a
single point in the program, and the former to a range (i.e. the whole
of the associated compound statement).
This patch fixes sollve's OpenMP 5.1 "omp assume"-based tests.
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Given "loop" construct, clang will try to treat it as "for",
"distribute" or "simd", depending on either the implied binding, or the
bind clause if present. This patch moves the code that performs this
construct remapping from sema to codegen.
For a "loop" construct without a bind clause, this patch will create an
implicit bind clause based on implied binding to simplify further
analysis.
During codegen the function `EmitOMPGenericLoopDirective` (i.e. "loop")
will invoke the "emit" functions for "for", "distribute" or "simd",
depending on the bind clause.
---------
Co-authored-by: Alexey Bataev <a.bataev@gmx.com>
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Add the interchange directive which will be introduced in the upcoming
OpenMP 6.0 specification. A preview has been published in [Technical
Report 12](https://www.openmp.org/wp-content/uploads/openmp-TR12.pdf).
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Add the reverse directive which will be introduced in the upcoming
OpenMP 6.0 specification. A preview has been published in [Technical
Report 12](https://www.openmp.org/wp-content/uploads/openmp-TR12.pdf).
---------
Co-authored-by: Alexey Bataev <a.bataev@outlook.com>
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This reverts commit ce4aada6e2135e29839f672a6599db628b53295d and a
follow-up patch 8ef26f1289bf069ccc0d6383f2f4c0116a1206c1.
This new warning can not be fully suppressed by the
`-Wno-missing-dependent-template-keyword` flag, this gives developer no
time to do the cleanup in a large codebase, see https://github.com/llvm/llvm-project/pull/98547#issuecomment-2228250884
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ConstraintSatisfaction (#98654)
This expression doesn't appear to be ever used, so let's remove it from
the data structure.
Fixed some spelling issues as well.
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Reapplies #92957, fixing an instance where the `template` keyword was
missing prior to a dependent name in `llvm/ADT/ArrayRef.h`. An
_alias-declaration_ is used to work around a bug affecting GCC releases
before 11.1 (see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94799) which
rejects the use of the `template` keyword prior to the
_nested-name-specifier_ in the class member access.
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ppc64le-lld-multistage-test has been failing.
This reverts commit 7bfb98c34687d9784f36937c3ff3e735698b498a.
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CWG1835 was one of the many core issues resolved by P1787R6: "Declarations and where to
find them" (http://wg21.link/p1787r6). Its resolution changes how
member-qualified names (as defined by [basic.lookup.qual.general] p2) are looked
up. This patch implementation that resolution.
Previously, an _identifier_ following `.` or `->` would be first looked
up in the type of the object expression (i.e. qualified lookup), and
then in the context of the _postfix-expression_ (i.e. unqualified
lookup) if nothing was found; the result of the second lookup was
required to name a class template. Notably, this second lookup would
occur even when the object expression was dependent, and its result
would be used to determine whether a `<` token is the start of a
_template-argument_list_.
The new wording in [basic.lookup.qual.general] p2 states:
> A member-qualified name is the (unique) component name, if any, of
> - an _unqualified-id_ or
> - a _nested-name-specifier_ of the form _`type-name ::`_ or
_`namespace-name ::`_
>
> in the id-expression of a class member access expression. A
***qualified name*** is
> - a member-qualified name or
> - the terminal name of
> - a _qualified-id_,
> - a _using-declarator_,
> - a _typename-specifier_,
> - a _qualified-namespace-specifier_, or
> - a _nested-name-specifier_, _elaborated-type-specifier_, or
_class-or-decltype_ that has a _nested-name-specifier_.
>
> The _lookup context_ of a member-qualified name is the type of its
associated object expression (considered dependent if the object
expression is type-dependent). The lookup context of any other qualified
name is the type, template, or namespace nominated by the preceding
_nested-name-specifier_.
And [basic.lookup.qual.general] p3 now states:
> _Qualified name lookup_ in a class, namespace, or enumeration performs
a search of the scope associated with it except as specified below.
Unless otherwise specified, a qualified name undergoes qualified name
lookup in its lookup context from the point where it appears unless the
lookup context either is dependent and is not the current instantiation
or is not a class or class template. If nothing is found by qualified
lookup for a member-qualified name that is the terminal name of a
_nested-name-specifier_ and is not dependent, it undergoes unqualified
lookup.
In non-standardese terms, these two paragraphs essentially state the
following:
- A name that immediately follows `.` or `->` in a class member access
expression is a member-qualified name
- A member-qualified name will be first looked up in the type of the
object expression `T` unless `T` is a dependent type that is _not_ the
current instantiation, e.g.
```
template<typename T>
struct A
{
void f(T* t)
{
this->x; // type of the object expression is 'A<T>'. although 'A<T>' is dependent, it is the
// current instantiation so we look up 'x' in the template definition context.
t->y; // type of the object expression is 'T' ('->' is transformed to '.' per [expr.ref]).
// 'T' is dependent and is *not* the current instantiation, so we lookup 'y' in the
// template instantiation context.
}
};
```
- If the first lookup finds nothing and:
- the member-qualified name is the first component of a
_nested-name-specifier_ (which could be an _identifier_ or a
_simple-template-id_), and either:
- the type of the object expression is the current instantiation and it
has no dependent base classes, or
- the type of the object expression is not dependent
then we lookup the name again, this time via unqualified lookup.
Although the second (unqualified) lookup is stated not to occur when the
member-qualified name is dependent, a dependent name will _not_ be
dependent once the template is instantiated, so the second lookup must
"occur" during instantiation if qualified lookup does not find anything.
This means that we must perform the second (unqualified) lookup during
parsing even when the type of the object expression is dependent, but
those results are _not_ used to determine whether a `<` token is the
start of a _template-argument_list_; they are stored so we can replicate
the second lookup during instantiation.
In even simpler terms (paraphrasing the meeting minutes from the review of P1787; see https://wiki.edg.com/bin/view/Wg21summer2020/P1787%28Lookup%29Review2020-06-15Through2020-06-18):
- Unqualified lookup always happens for the first name in a
_nested-name-specifier_ that follows `.` or `->`
- The result of that lookup is only used to determine whether `<` is the
start of a _template-argument-list_ if the first (qualified) lookup
found nothing and the lookup context:
- is not dependent, or
- is the current instantiation and has no dependent base classes.
An example:
```
struct A
{
void f();
};
template<typename T>
using B = A;
template<typename T>
struct C : A
{
template<typename U>
void g();
void h(T* t)
{
this->g<int>(); // ok, '<' is the start of a template-argument-list ('g' was found via qualified lookup in the current instantiation)
this->B<void>::f(); // ok, '<' is the start of a template-argument-list (current instantiation has no dependent bases, 'B' was found via unqualified lookup)
t->g<int>(); // error: '<' means less than (unqualified lookup does not occur for a member-qualified name that isn't the first component of a nested-name-specifier)
t->B<void>::f(); // error: '<' means less than (unqualified lookup does not occur if the name is dependent)
t->template B<void>::f(); // ok: '<' is the start of a template-argument-list ('template' keyword used)
}
};
```
Some additional notes:
- Per [basic.lookup.qual.general] p1, lookup for a
member-qualified name only considers namespaces, types, and templates
whose specializations are types if it's an _identifier_ followed by
`::`; lookup for the component name of a _simple-template-id_ followed
by `::` is _not_ subject to this rule.
- The wording which specifies when the second unqualified lookup occurs
appears to be paradoxical. We are supposed to do it only for the first
component name of a _nested-name-specifier_ that follows `.` or `->`
when qualified lookup finds nothing. However, when that name is followed
by `<` (potentially starting a _simple-template-id_) we don't _know_
whether it will be the start of a _nested-name-specifier_ until we do
the lookup -- but we aren't supposed to do the lookup until we know it's
part of a _nested-name-specifier_! ***However***, since we only do the
second lookup when the first lookup finds nothing (and the name isn't
dependent), ***and*** since neither lookup is type-only, the only valid
option is for the name to be the _template-name_ in a
_simple-template-id_ that is followed by `::` (it can't be an
_unqualified-id_ naming a member because we already determined that the
lookup context doesn't have a member with that name). Thus, we can lock
into the _nested-name-specifier_ interpretation and do the second lookup
without having to know whether the _simple-template-id_ will be followed
by `::` yet.
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In no transitive change mode, the unresolved ADL may not
be referenced, then it is problematic if the change didn't get
propagated correctly. This patch add references to all the possible
module files for the unresolved ADL to solve the problem.
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This commit implements the entirety of the now-accepted [N3017
-Preprocessor
Embed](https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3017.htm) and
its sister C++ paper [p1967](https://wg21.link/p1967). It implements
everything in the specification, and includes an implementation that
drastically improves the time it takes to embed data in specific
scenarios (the initialization of character type arrays). The mechanisms
used to do this are used under the "as-if" rule, and in general when the
system cannot detect it is initializing an array object in a variable
declaration, will generate EmbedExpr AST node which will be expanded by
AST consumers (CodeGen or constant expression evaluators) or expand
embed directive as a comma expression.
This reverts commit
https://github.com/llvm/llvm-project/commit/682d461d5a231cee54d65910e6341769419a67d7.
---------
Co-authored-by: The Phantom Derpstorm <phdofthehouse@gmail.com>
Co-authored-by: Aaron Ballman <aaron@aaronballman.com>
Co-authored-by: cor3ntin <corentinjabot@gmail.com>
Co-authored-by: H. Vetinari <h.vetinari@gmx.com>
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