Original commit message:
"
Commit https://github.com/llvm/llvm-project/commit/46f3ade introduced a notion
of printing the attributes on the left to improve the printing of attributes
attached to variable declarations. The intent was to produce more GCC compatible
code because clang tends to print the attributes on the right hand side which is
not accepted by gcc.
This approach has increased the complexity in tablegen and the attrubutes
themselves as now the are supposed to know where they could appear. That lead to
mishandling of the `override` keyword which is modelled as an attribute in
clang.
This patch takes an inspiration from the existing approach and tries to keep the
position of the attributes as they were written. To do so we use simpler
heuristic which checks if the source locations of the attribute precedes the
declaration. If so, it is considered to be printed before the declaration.
Fixes https://github.com/llvm/llvm-project/issues/87151
"
The reason for the bot breakage is that attributes coming from ApiNotes are not
marked implicit even though they do not have source locations. This caused an
assert to trigger. This patch forces attributes with no source location
information to be printed on the left. That change is consistent to the overall
intent of the change to increase the chances for attributes to compile across
toolchains and at the same time the produced code to be as close as possible to
the one written by the user.
Commit https://github.com/llvm/llvm-project/commit/46f3ade introduced a
notion of printing the attributes on the left to improve the printing of
attributes attached to variable declarations. The intent was to produce
more GCC compatible code because clang tends to print the attributes on
the right hand side which is not accepted by gcc.
This approach has increased the complexity in tablegen and the
attrubutes themselves as now the are supposed to know where they could
appear. That lead to mishandling of the `override` keyword which is
modelled as an attribute in clang.
This patch takes an inspiration from the existing approach and tries to
keep the position of the attributes as they were written. To do so we
use simpler heuristic which checks if the source locations of the
attribute precedes the declaration. If so, it is considered to be
printed before the declaration.
Fixes https://github.com/llvm/llvm-project/issues/87151
The values for `__has_cpp_attribute` don't have to be guarded behind
`LangOpts.CPlusPlus` because `__has_cpp_attribute` isn't available if
Clang isn't in a C++ mode.
Fixes#82995
EnumArgument may be a string or an identifier. If it is a string, it
should be parsed as unevaluated string literal. Add IsString flag to
EnumArgument so that the parser can choose the correct parsing method.
Target-specific attributes that share spelling may have different
attribute "prototypes". For example, ARM's version of "interrupt"
attribute accepts a string enum, while MSP430's version accepts an
unsigned integer. Adjust ClangAttrEmitter so that the generated
`attributeStringLiteralListArg` returns the correct mask depending on
target triple.
It is worth noting that even after this change some string arguments are
still parsed as identifiers or, worse, as expressions. This is because
of some special logic in `ParseAttributeArgsCommon`. Fixing it is out of
scope of this patch.
GCC 14 defines `__arm_streaming` as a macro expanding to
`[[arm::streaming]]`. Due to the nested macro use, this gets expanded
prior to concatenation.
It doesn't look like C++ has a really clean way to prevent macro
expansion. The best I have found is to use `EMPTY ## X` where `EMPTY` is
an empty macro argument, so this is the hack I'm implementing here.
Fixes https://github.com/llvm/llvm-project/issues/78691.
This upstreams more of the Clang API Notes functionality that is
currently implemented in the Apple fork:
https://github.com/apple/llvm-project/tree/next/clang/lib/APINotes
This is the largest chunk of the API Notes functionality in the
upstreaming process. I will soon submit a follow-up patch to actually
enable usage of this functionality by having a Clang driver flag that
enables API Notes, along with tests.
This patch replaces the `__arm_new_za`, `__arm_shared_za` and
`__arm_preserves_za` attributes in favour of:
* `__arm_new("za")`
* `__arm_in("za")`
* `__arm_out("za")`
* `__arm_inout("za")`
* `__arm_preserves("za")`
As described in https://github.com/ARM-software/acle/pull/276.
One change is that `__arm_in/out/inout/preserves(S)` are all mutually
exclusive, whereas previously it was fine to write `__arm_shared_za
__arm_preserves_za`. This case is now represented with `__arm_in("za")`.
The current implementation uses the same LLVM attributes under the hood,
since `__arm_in/out/inout` are all variations of "shared ZA", so can use
the existing `aarch64_pstate_za_shared` attribute in LLVM.
#77941 will add support for the new "zt0" state as introduced
with SME2.
Rather than write a bunch of logic to shepherd between enums with the
same sets of values, add the ability for EnumArgument to refer to an
external enum in the first place.
1. The generated file contained a lot of duplicate switch cases, e.g.:
```
switch (Syntax) {
case AttributeCommonInfo::Syntax::AS_GNU:
return llvm::StringSwitch<int>(Name)
...
.Case("error", 1)
.Case("warning", 1)
.Case("error", 1)
.Case("warning", 1)
```
2. Some attributes were listed in wrong places, e.g.:
```
case AttributeCommonInfo::Syntax::AS_CXX11: {
if (ScopeName == "") {
return llvm::StringSwitch<int>(Name)
...
.Case("warn_unused_result", LangOpts.CPlusPlus11 ? 201907 : 0)
```
`warn_unused_result` is a non-standard attribute and should not be
available as [[warn_unused_result]].
3. Some attributes had the wrong version, e.g.:
```
case AttributeCommonInfo::Syntax::AS_CXX11: {
} else if (ScopeName == "gnu") {
return llvm::StringSwitch<int>(Name)
...
.Case("fallthrough", LangOpts.CPlusPlus11 ? 201603 : 0)
```
[[gnu::fallthrough]] is a non-standard spelling and should not have the
standard version. Instead, __has_cpp_attribute should return 1 for it.
There is another issue with attributes that share spellings, e.g.:
```
.Case("interrupt", true && (T.getArch() == llvm::Triple::arm || ...) ? 1 : 0)
.Case("interrupt", true && (T.getArch() == llvm::Triple::avr) ? 1 : 0)
...
.Case("interrupt", true && (T.getArch() == llvm::Triple::riscv32 || ...) ? 1 : 0)
```
As can be seen, __has_attribute(interrupt) would only return true for
ARM targets. This patch does not address this issue.
Differential Revision: https://reviews.llvm.org/D159393
This implements the [[msvc::no_unique_address]] attribute.
There is not ABI compatibility in this patch because the attribute is
relatively new and there's still some uncertainty in the MSVC version.
The recommit changes the attribute definitions so that instead of making
two separate attributes for no_unique_address
and msvc::no_unique_address, it modifies the attributes tablegen emitter
to allow spellings to be target-specific.
This reverts commit 71f9e7695b87298f9855d8890f0e6a3b89381eb5.
Inside `writePrettyPrintFunction()`, we check if we need to emit the
given argument:
```C++
if (!arg->isOptional() || arg->getIsOmitted() == "false") {
FoundNonOptArg = true;
continue;
}
```
For the `AssumeAligned` attribute, the second argument was optional, but
the `getIsOmitted()` returned `false`, thus we treated this argument as
**non-optional** in the end because of that disjunction.
It was because `getIsOmitted()` did not account for `Expr *` type, and
returned `false` on the fallthrough branch.
Fixes#67156
Currently there is no PrintOnLeft attribute set, which results in an
empty switch-case. When compiling this, MSVC issues a warning saying
that the switch-case is empty. Fix this by using a macro and checking
if this macro is defined or not.
Links to D157394
Previously clang AST prints the following declaration:
int fun_var_unused() {
int x __attribute__((unused)) = 0;
return x;
}
and
int __declspec(thread) x = 0;
as:
int fun_var_unused() {
int x = 0 __attribute__((unused));
return x;
}
and
int x = __declspec(thread) 0;
which is rejected by C/C++ parser. This patch modifies the logic to
print old C attributes for variables as:
int __attribute__((unused)) x = 0;
and the __declspec case as:
int __declspec(thread) x = 0;
Fixes: https://github.com/llvm/llvm-project/issues/59973
Previous version: D141714.
Differential Revision:https://reviews.llvm.org/D141714
The attributes changes were left out of Clang 17.
Attributes that used to take a string literal now accept an unevaluated
string literal instead, which means they reject numeric escape sequences
and strings literal with an encoding prefix - but the later was already
ill-formed in most cases.
We need to know that we are going to parse an unevaluated string literal
before we do - so we can reject numeric escape sequence,
so we derive from Attrs.td which attributes parameters are expected
to be string literals.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D156237
This does the rename for most internal uses of C2x, but does not rename
or reword diagnostics (those will be done in a follow-up).
I also updated standards references and citations to the final wording
in the standard.
This patch adds the Parse and Sema support for RegularKeyword attributes,
following on from a previous patch that added Attr.td support.
The patch is quite large. However, nothing outside the tests is
specific to the first RegularKeyword attribute (__arm_streaming).
The patch should therefore be a one-off, up-front cost. Other
attributes just need an entry in Attr.td and the usual Sema support.
The approach taken in the patch is that the keywords can be used with
any language version. If standard attributes were added in language
version Y, the keyword rules for version X<Y are the same as they were
for version Y (to the extent possible). Any extensions beyond Y are
handled in the same way for both keywords and attributes. This ensures
that existing C++11 successors like C++17 are not treated differently
from versions that have yet to be defined.
Some notes on the implementation:
* The patch emits errors rather than warnings for diagnostics that
relate to keywords.
* Where possible, the patch drops “attribute” from diagnostics
relating to keywords.
* One exception to the previous point is that warnings about C++
extensions do still mention attributes. The use there seemed OK
since the diagnostics are noting a change in the production rules.
* If a diagnostic string needs to be different for keywords and
attributes, the patch standardizes on passing the attribute/
name/token followed by 0 for attributes and 1 for keywords.
* Although the patch updates warn_attribute_wrong_decl_type_str,
warn_attribute_wrong_decl_type, and warn_attribute_wrong_decl_type,
only the error forms of these strings are used for keywords.
* I couldn't trigger the warnings in checkUnusedDeclAttributes,
even for existing attributes. An assert on the warnings caused
no failures in the testsuite. I think in practice all standard
attributes would be diagnosed before this.
* The patch drops a call to standardAttributesAllowed in
ParseFunctionDeclarator. This is because MaybeParseCXX11Attributes
checks the same thing itself, where appropriate.
* The new tests are based on c2x-attributes.c and
cxx0x-attributes.cpp. The C++ test also incorporates a version of
cxx11-base-spec-attributes.cpp. The FIXMEs are carried across from
the originals.
Differential Revision: https://reviews.llvm.org/D148702
Platform-specific language extensions often want to provide a way of
indicating that certain functions should be called in a different way,
compiled in a different way, or otherwise treated differently from a
“normal” function. Honoring these indications is often required for
correctness, rather being than an optimization/QoI thing.
If a function declaration has a property P that matters for correctness,
it will be ODR-incompatible with a function that does not have property P.
If a function type has a property P that affects the calling convention,
it will not be two-way compatible with a function type that does not
have property P. These properties therefore affect language semantics.
That in turn means that they cannot be treated as standard [[]]
attributes.
Until now, many of these properties have been specified using GNU-style
attributes instead. GNU attributes have traditionally been more lax
than standard attributes, with many of them having semantic meaning.
Examples include calling conventions and the vector_size attribute.
However, there is a big drawback to using GNU attributes for semantic
information: compilers that don't understand the attributes will
(by default) emit a warning rather than an error. They will go on to
compile the code as though the attributes weren't present, which will
inevitably lead to wrong code in most cases. For users who live
dangerously and disable the warning, this wrong code could even be
generated silently.
A more robust approach would be to specify the properties using
keywords, which older compilers would then reject. Some vendor-specific
extensions have already taken this approach. But traditionally, each
such keyword has been treated as a language extension in its own right.
This has three major drawbacks:
(1) The parsing rules need to be kept up-to-date as the language evolves.
(2) There are often corner cases that similar extensions handle differently.
(3) Each extension requires more custom code than a standard attribute.
The underlying problem for all three is that, unlike for true attributes,
there is no established template that extensions can reuse. The purpose
of this patch series is to try to provide such a template.
One option would have been to pick an existing keyword and do whatever
that keyword does. The problem with that is that most keywords only
apply to specific kinds of types, kinds of decls, etc., and so the
parsing rules are (for good reason) not generally applicable to all
types and decls.
Really, the “only” thing wrong with using standard attributes is that
standard attributes cannot affect semantics. In all other respects
they provide exactly what we need: a well-defined grammar that evolves
with the language, clear rules about what an attribute appertains to,
and so on.
This series therefore adds keyword “attributes” that can appear
exactly where a standard attribute can appear and that appertain
to exactly what a standard attribute would appertain to. The link is
mechanical and no opt-outs or variations are allowed. This should
make the keywords predictable for programmers who are already
familiar with standard attributes.
This does mean that these keywords will be accepted for parsing purposes
in many more places than necessary. Inappropriate uses will then be
diagnosed during semantic analysis. However, the compiler would need
to reject the keywords in those positions whatever happens, and treating
them as ostensible attributes shouldn't be any worse than the alternative.
In some cases it might even be better. For example, SME's
__arm_streaming attribute would make conceptual sense as a statement
attribute, so someone who takes a “try-it-and-see” approach might write:
__arm_streaming { …block-of-code…; }
In fact, we did consider supporting this originally. The reason for
rejecting it was that it was too difficult to implement, rather than
because it didn't make conceptual sense.
One slight disadvantage of the keyword-based approach is that it isn't
possible to use #pragma clang attribute with the keywords. Perhaps we
could add support for that in future, if it turns out to be useful.
For want of a better term, I've called the new attributes "regular"
keyword attributes (in the sense that their parsing is regular wrt
standard attributes), as opposed to "custom" keyword attributes that
have their own parsing rules.
This patch adds the Attr.td support for regular keyword attributes.
Adding an attribute with a RegularKeyword spelling causes tablegen
to define the associated tokens and to record that attributes created
with that syntax are regular keyword attributes rather than custom
keyword attributes.
A follow-on patch contains the main Parse and Sema support,
which is enabled automatically by the Attr.td definition.
Other notes:
* The series does not allow regular keyword attributes to take
arguments, but this could be added in future.
* I wondered about trying to use tablegen for
TypePrinter::printAttributedAfter too, but decided against it.
RegularKeyword is really a spelling-level classification rather
than an attribute-level classification, and in general, an attribute
could have both GNU and RegularKeyword spellings. In contrast,
printAttributedAfter is only given the attribute kind and the type
that results from applying the attribute. AFAIK, it doesn't have
access to the original attribute spelling. This means that some
attribute-specific or type-specific knowledge might be needed
to print the attribute in the best way.
* Generating the tokens automatically from Attr.td means that
pseudo's libgrammar does now depend on tablegen.
* The patch uses the SME __arm_streaming attribute as an example
for testing purposes. The attribute does not do anything at this
stage. Later SME-specific patches will add proper semantics for it,
and add other SME-related keyword attributes.
Differential Revision: https://reviews.llvm.org/D148700
Reported by Coverity:
AUTO_CAUSES_COPY
Unnecessary object copies can affect performance.
1. Inside "SemaDeclCXX.cpp" file, in <unnamed>::DiagnoseUninitializedFields(clang::Sema &, clang::CXXConstructorDecl const *): Using the auto keyword without an & causes the copy of an object of type CXXBaseSpecifier.
2. Inside "ClangAttrEmitter.cpp" file, in clang::EmitClangAttrParsedAttrImpl(llvm::RecordKeeper &, llvm::raw_ostream &): Using the auto keyword without an & causes the copy of an object of type pair.
3. Inside "Marshallers.h" file, in clang::ast_matchers::dynamic::internal::MapAnyOfBuilderDescriptor::buildMatcherCtor(clang::ast_matchers::dynamic::SourceRange, llvm::ArrayRef<clang::ast_matchers::dynamic::ParserValue>, clang::ast_matchers::dynamic::Diagnostics *): Using the auto keyword without an & causes the copy of an object of type ParserValue.
4. Inside "CGVTables.cpp" file, in clang::CodeGen::CodeGenModule::GetVCallVisibilityLevel(clang::CXXRecordDecl const *, llvm::DenseSet<clang::CXXRecordDecl const *, llvm::DenseMapInfo<clang::CXXRecordDecl const *, void>> &): Using the auto keyword without an & causes the copy of an object of type CXXBaseSpecifier.
5. Inside "ASTContext.cpp" file, in hasTemplateSpecializationInEncodedString(clang::Type const *, bool): Using the auto keyword without an & causes the copy of an object of type CXXBaseSpecifier.
6. Inside "ComputeDependence.cpp" file, in clang::computeDependence(clang::DependentScopeDeclRefExpr *): Using the auto keyword without an & causes the copy of an object of type TemplateArgumentLoc.
Reviewed By: tahonermann, erichkeane
Differential Revision: https://reviews.llvm.org/D148812
AttributeCommonInfo::isAlignasAttribute() was used in one place:
isCXX11Attribute(). The intention was for isAlignasAttribute()
to return true for the C++ alignas keyword. However, as a FIXME
noted, the function also returned true for the C _Alignas keyword.
This meant that isCXX11Attribute() returned true for _Alignas as
well as for alignas.
AttributeCommonInfos are now always constructed with an
AttributeCommonInfo::Form. We can use that Form to convey whether
a keyword is alignas or not.
The patch uses 1 bit of an 8-bit hole in the current layout
of AttributeCommonInfo. This might not be the best long-term design,
but it should be easy to adapt the layout if necessary (that is,
if other uses are found for the spare bits).
I don't know of a way of testing this (other than grep -c FIXME)
Differential Revision: https://reviews.llvm.org/D148105
This patch adds static functions for constructing most
AttributeCommonInfo::Forms. Direct construction is only retained where
all fields (currently the syntax and spelling) are specified explicitly.
This is a wash on its own. The purpose is to allow extra fields
to be added to Form without disrupting all callers. In particular,
it allows extra information to be stored about keywords without
affecting non-keyword uses.
No functional change intended.
Differential Revision: https://reviews.llvm.org/D148104
When constructing an attribute, the syntactic form was specified
using two arguments: an attribute-independent syntax type and an
attribute-specific spelling index. This patch replaces them with
a single argument.
In most cases, that's done using a new Form class that combines the
syntax and spelling into a single object. This has the minor benefit
of removing a couple of constructors. But the main purpose is to allow
additional information to be stored as well, beyond just the syntax and
spelling enums.
In the case of the attribute-specific Create and CreateImplicit
functions, the patch instead uses the attribute-specific spelling
enum. This helps to ensure that the syntax and spelling are
consistent with each other and with the Attr.td definition.
If a Create or CreateImplicit caller specified a syntax and
a spelling, the patch drops the syntax argument and keeps the
spelling. If the caller instead specified only a syntax
(so that the spelling was SpellingNotCalculated), the patch
simply drops the syntax argument.
There were two cases of the latter: TargetVersion and Weak.
TargetVersionAttrs were created with GNU syntax, which matches
their definition in Attr.td, but which is also the default.
WeakAttrs were created with Pragma syntax, which does not match
their definition in Attr.td. Dropping the argument switches
them to AS_GNU too (to match [GCC<"weak">]).
Differential Revision: https://reviews.llvm.org/D148102
The purpose of this patch and follow-on patches is to ensure that
AttributeCommonInfos always have a syntax that is appropriate for
their kind (i.e. that it matches one of the entries in Attr.td).
The attribute-specific Create and CreateImplicit methods had four
overloads, based on their tail arguments:
(1) no extra arguments
(2) an AttributeCommonInfo
(3) a SourceRange
(4) a SourceRange, a syntax, and (where necessary) a spelling
When (4) had a spelling argument, it defaulted to
SpellingNotCalculated.
One disadvantage of this was that (1) and (3) zero-initialized
the syntax field of the AttributeCommonInfo, which corresponds
to AS_GNU. But AS_GNU isn't always listed as a possibility
in Attr.td.
This patch therefore removes (1) and (3) and instead provides
the same functionality using default arguments on (4) (a bit
like the existing default argument for the spelling).
The default syntax is taken from the attribute's first valid
spelling.
Doing that raises the question: what should happen for attributes
like AlignNatural and CUDAInvalidTarget that are only ever created
implicitly, and so have no source-code manifestation at all?
The patch adds a new AS_Implicit "syntax" for that case.
The patch also removes the syntax argument for these attributes,
since the syntax must always be AS_Implicit.
For similar reasons, the patch removes the syntax argument if
there is exactly one valid spelling.
Doing this means that AttributeCommonInfo no longer needs the
single-argument constructors. It is always given a syntax instead.
Differential Revision: https://reviews.llvm.org/D148101
The single-argument constructors of this class were not marked explicit
and that led to some incorrect uses that slipped under the radar (see
changes in SemaDeclAttr.cpp). This makes the constructors explicit,
changes the benignly incorrect uses, and updates the tablegen code to
emit the correct support code to call the explicit constructors.
While this does correct a misuse, that incorrect usage could not be
observed except via a debugger and so no additional tests are added.
Differential Revision: https://reviews.llvm.org/D147661
Allow the user to specify a concrete USR in the external_source_symbol attribute.
That will let Clang's indexer to use Swift USRs for Swift declarations that are
represented with C++ declarations.
This new clause is used by Swift when generating a C++ header representation
of a Swift module:
https://github.com/apple/swift/pull/63002
Differential Revision: https://reviews.llvm.org/D141324
HLSL entry function parameters must have parameter annotations. This
allows appropriate intrinsic values to be populated into parameters
during code generation.
This does not handle entry function return values, which will be
handled in a subsequent commit because we don't currently support any
annotations that are valid for function returns.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D131625
In preparation for allowing the prefer_type list in the append_args clause,
use the OMPInteropInfo in the attribute for 'declare variant'.
This requires adding a new Argument kind to the attribute code. This change
adds a specific attribute to pass an array of OMPInteropInfo. It implements
new tablegen needed to handle the interop-type part of the structure. When
prefer_type is added, more work will be needed to dump, instantiate, and
serialize the PreferTypes field in OMPInteropInfo.
Differential Revision: https://reviews.llvm.org/D132270
Almost all attributes currently marked `Undocumented` are user-facing
attributes which _ought_ to be documented, but nobody has written it
yet. This change ensures that we at least acknowledge that these
attributes exist in the documentation, even if we have no description
of their semantics.
A new category, `InternalOnly` has been added for those few attributes
which are not user-facing, and should remain omitted from the docs.
For backwards compatiblity, we emit only a warning instead of an error if the
attribute is one of the existing type attributes that we have historically
allowed to "slide" to the `DeclSpec` just as if it had been specified in GNU
syntax. (We will call these "legacy type attributes" below.)
The high-level changes that achieve this are:
- We introduce a new field `Declarator::DeclarationAttrs` (with appropriate
accessors) to store C++11 attributes occurring in the attribute-specifier-seq
at the beginning of a simple-declaration (and other similar declarations).
Previously, these attributes were placed on the `DeclSpec`, which made it
impossible to reconstruct later on whether the attributes had in fact been
placed on the decl-specifier-seq or ahead of the declaration.
- In the parser, we propgate declaration attributes and decl-specifier-seq
attributes separately until we can place them in
`Declarator::DeclarationAttrs` or `DeclSpec::Attrs`, respectively.
- In `ProcessDeclAttributes()`, in addition to processing declarator attributes,
we now also process the attributes from `Declarator::DeclarationAttrs` (except
if they are legacy type attributes).
- In `ConvertDeclSpecToType()`, in addition to processing `DeclSpec` attributes,
we also process any legacy type attributes that occur in
`Declarator::DeclarationAttrs` (and emit a warning).
- We make `ProcessDeclAttribute` emit an error if it sees any non-declaration
attributes in C++11 syntax, except in the following cases:
- If it is being called for attributes on a `DeclSpec` or `DeclaratorChunk`
- If the attribute is a legacy type attribute (in which case we only emit
a warning)
The standard justifies treating attributes at the beginning of a
simple-declaration and attributes after a declarator-id the same. Here are some
relevant parts of the standard:
- The attribute-specifier-seq at the beginning of a simple-declaration
"appertains to each of the entities declared by the declarators of the
init-declarator-list" (https://eel.is/c++draft/dcl.dcl#dcl.pre-3)
- "In the declaration for an entity, attributes appertaining to that entity can
appear at the start of the declaration and after the declarator-id for that
declaration." (https://eel.is/c++draft/dcl.dcl#dcl.pre-note-2)
- "The optional attribute-specifier-seq following a declarator-id appertains to
the entity that is declared."
(https://eel.is/c++draft/dcl.dcl#dcl.meaning.general-1)
The standard contains similar wording to that for a simple-declaration in other
similar types of declarations, for example:
- "The optional attribute-specifier-seq in a parameter-declaration appertains to
the parameter." (https://eel.is/c++draft/dcl.fct#3)
- "The optional attribute-specifier-seq in an exception-declaration appertains
to the parameter of the catch clause" (https://eel.is/c++draft/except.pre#1)
The new behavior is tested both on the newly added type attribute
`annotate_type`, for which we emit errors, and for the legacy type attribute
`address_space` (chosen somewhat randomly from the various legacy type
attributes), for which we emit warnings.
Depends On D111548
Reviewed By: aaron.ballman, rsmith
Differential Revision: https://reviews.llvm.org/D126061
HLSL has a language feature called Semantics which get attached to
declarations like attributes and are used in a variety of ways.
One example of semantic use is here with the `SV_GroupIndex` semantic
which, when applied to an input for a compute shader is pre-populated
by the driver with a flattened thread index.
Differential Revision: https://reviews.llvm.org/D122699
# Conflicts:
# clang/include/clang/Basic/Attr.td
# clang/include/clang/Basic/AttrDocs.td
