This reverts commit 2f20743952 because it
triggers an assertion when building an LLDB test program:
Assertion failed: (InstantiatingSpecializations.empty() && "failed to
clean up an InstantiatingTemplate?"), function ~Sema, file
/Users/buildslave/jenkins/workspace/lldb-cmake/llvm-project/clang/lib/Sema/Sema.cpp,
line 458.
More details in https://reviews.llvm.org/D126907.
It helps to avoid copy-paste mistakes and makes custom code paths more
noticeable.
Not funnelling all diagnostic through `ODRDiagDeclError` because plan to
break down `err_module_odr_violation_mismatch_decl_diff` into smaller
pieces instead of making it bigger and bigger.
Differential Revision: https://reviews.llvm.org/D128487
This patch gives basic parsing and semantic support for
"masked taskloop simd" construct introduced in OpenMP 5.1 (section 2.16.8)
Differential Revision: https://reviews.llvm.org/D128693
This patch gives basic parsing and semantic support for "masked taskloop"
construct introduced in OpenMP 5.1 (section 2.16.7)
Differential Revision: https://reviews.llvm.org/D128478
Currently we do not in general merge attributes when importing decls from modules. This patch handles availability, but long term we need to properly handle all attributes.
I tried to use Sema::mergeDeclAttributes, but it caused test crashes as I don't think it expects to be called in this context. We really shouldn't have duplicate code for merging attributes long term, but for now this fixes availability. There's already a TODO for this in the declaration of ASTDeclReader::mergeInheritableAttributes.
Differential Revision: https://reviews.llvm.org/D127182
rdar://85820301
This patch adds the codegen support for `atomic compare capture` in clang.
Reviewed By: ABataev
Differential Revision: https://reviews.llvm.org/D120290
This is a support for " #pragma omp atomic compare fail ". It has Parser & AST support for now.
Reviewed By: tianshilei1992
Differential Revision: https://reviews.llvm.org/D123235
Adds support for the reserved locator 'omp_all_memory' for use
in depend clauses with 'out' or 'inout' dependence-types.
Differential Revision: https://reviews.llvm.org/D125828
Number of statements in CompoundStmt is kept in a bit-field of the common
part of Stmt. The field has 24 bits for the number. To allocate a new
bit field (as attempted in https://reviews.llvm.org/D123952), this
number must be reduced, maximal number of statements in a compound
statement becomes smaller. It can result in compilation errors of some
programs.
With this change the number of statements is kept in a field of type
'unsigned int' rather than in bit-field. To make room in CompoundStmtBitfields
LBraceLoc is moved to fields of CompoundStmt.
Differential Revision: https://reviews.llvm.org/D125635
This is a 1.9% reduction in PCH size in my measurements.
In abbreviated records, VBR6 seems to be slightl better than VBR8 for locations
that may be delta-encoded (i.e. not the first)
Differential Revision: https://reviews.llvm.org/D125952
Much of the size of PCH/PCM files comes from stored SourceLocations.
These are encoded using (almost) their raw value, VBR-encoded. Absolute
SourceLocations can be relatively large numbers, so this commonly takes
20-30 bits per location.
We can reduce this by exploiting redundancy: many "nearby" SourceLocations are
stored differing only slightly and can be delta-encoded.
Randam-access loading of AST nodes constrains how long these sequences
can be, but we can do it at least within a node that always gets
deserialized as an atomic unit.
TypeLoc is implemented in this patch as it's a relatively small change
that shows most of the API.
This saves ~3.5% of PCH size, I have local changes applying this technique
further that save another 3%, I think it's possible to get to 10% total.
Differential Revision: https://reviews.llvm.org/D125403
This diff changes the serialization of the `ORIGINAL_PCH_DIR`
entry in module files to be serialized relative to the module's
`BaseDirectory`. This will allow for the module to be relocatable
across machines.
The path is restored relative to the module's BaseDirectory on
deserialization.
Reviewed By: urnathan
Differential Revision: https://reviews.llvm.org/D124946
This diff changes the serialization of the `SUBMODULE_TOPHEADER`
entry in module files to be serialized relative to the module's
`BaseDirectory`. This matches the behavior of the
`SUBMODULE_HEADER` entry and will allow for the module to be
relocatable across machines.
The path is restored relative to the module's `BaseDirectory` on
deserialization.
Reviewed By: urnathan
Differential Revision: https://reviews.llvm.org/D124938
This diff adds a new frontend flag `-fmodule-file-home-is-cwd`.
The behavior of this flag is similar to
`-fmodule-map-file-home-is-cwd` but does not require the module
map files to be modified to have inputs relative to the cwd.
Instead the output modules will have their `BaseDirectory` set
to the cwd and will try and resolve paths relative to that.
The motiviation for this change is to support relocatable pcm
files that are built on different machines with different paths
without having to alter module map files, which is sometimes not
possible as they are provided by 3rd parties.
Reviewed By: urnathan
Differential Revision: https://reviews.llvm.org/D124874
This includes a fix for the libc++ issue I ran across with friend
declarations not properly being identified as overloads.
This reverts commit 45c07db31c.
ASTWriter::associateDeclWithFile shows a lot in clangd perf profile due to O(n^2) behaviour in insertion of DeclIDs in SortedFileDeclIDs. Instead of doing that, this patch just appends it to the DeclIDs vector and sorts them at the end.
Reviewed By: akyrtzi
Differential Revision: https://reviews.llvm.org/D124840
This reverts commit a97899108e.
The patch caused some problems with the libc++ `__range_adaptor_closure`
that I haven't been able to figure out the cause of, so I am reverting
while I figure out whether this is a solvable problem/issue with the
CFE, or libc++ depending on an older 'incorrect' behavior.
This reverts commit 0c31da4838.
I've solved the issue with the PointerUnion by making the
`FunctionTemplateDecl` pointer be a NamedDecl, that could be a
`FunctionDecl` or `FunctionTemplateDecl` depending. This is enforced
with an assert.
This reverts commit 4b6c2cd647.
The patch caused numerous ARM 32 bit build failures, since we added a
5th item to the PointerUnion, and went over the 2-bits available in the
32 bit pointers.
As reported here: https://github.com/llvm/llvm-project/issues/44178
Concepts are not supposed to be instantiated until they are checked, so
this patch implements that and goes through significant amounts of work
to make sure we properly re-instantiate the concepts correctly.
Differential Revision: https://reviews.llvm.org/D119544
Emitting metadata for the same ivar multiple times can lead to
miscompilations. Objective-C runtime adds offsets to calculate ivar
position in memory and presence of duplicate offsets causes wrong final
position thus overwriting unrelated memory.
Such a situation is impossible with modules disabled as clang diagnoses
ivar redeclarations during sema checks after parsing
(`Sema::ActOnFields`). Fix the case with modules enabled by checking
during deserialization if ivar is already declared. We also support
a use case where the same category ends up in multiple modules. We
don't want to treat this case as ivar redeclaration and instead merge
corresponding ivars.
rdar://83468070
Differential Revision: https://reviews.llvm.org/D121177
When exprs are written unabbreviated:
- these were encoded as 5 x vbr6 = 30 bits
- now they fit exactly into a one-chunk vbr = 6 bits
clangd --check=clangd/AST.cpp reports ~1% reduction in PCH size
(42826720->42474460)
Differential Revision: https://reviews.llvm.org/D124250
This reverts commit eadf352707.
The reland fixes a couple of places in clang that were unneccesarily
requesting a null-terminated buffer of the PCH, and hitting assertions.
This patch changes type of the `File` parameter in `PPCallbacks::InclusionDirective()` from `const FileEntry *` to `Optional<FileEntryRef>`.
With the API change in place, this patch then removes some uses of the deprecated `FileEntry::getName()` (e.g. in `DependencyGraph.cpp` and `ModuleDependencyCollector.cpp`).
Reviewed By: dexonsmith, bnbarham
Differential Revision: https://reviews.llvm.org/D123574
Returning `std::array<uint8_t, N>` is better ergonomics for the hashing functions usage, instead of a `StringRef`:
* When returning `StringRef`, client code is "jumping through hoops" to do string manipulations instead of dealing with fixed array of bytes directly, which is more natural
* Returning `std::array<uint8_t, N>` avoids the need for the hasher classes to keep a field just for the purpose of wrapping it and returning it as a `StringRef`
As part of this patch also:
* Introduce `TruncatedBLAKE3` which is useful for using BLAKE3 as the hasher type for `HashBuilder` with non-default hash sizes.
* Make `MD5Result` inherit from `std::array<uint8_t, 16>` which improves & simplifies its API.
Differential Revision: https://reviews.llvm.org/D123100
Without the fix ivars with anonymous types can trigger errors like
> error: 'TestClass::structIvar' from module 'Target' is not present in definition of 'TestClass' provided earlier
> [...]
> note: declaration of 'structIvar' does not match
It happens because types of ivars from different modules are considered
to be different. And it is caused by not merging anonymous `TagDecl`
from different modules.
To fix that I've changed `serialization::needsAnonymousDeclarationNumber`
to handle anonymous `TagDecl` inside `ObjCInterfaceDecl`. But that's not
sufficient as C code inside `ObjCInterfaceDecl` doesn't use interface
decl as a decl context but switches to its parent (TranslationUnit in
most cases). I'm changing that to make `ObjCContainerDecl` the lexical
decl context but keeping the semantic decl context intact.
Test "check-dup-decls-inside-objc.m" doesn't reflect a change in
functionality but captures the existing behavior to prevent regressions.
rdar://85563013
Differential Revision: https://reviews.llvm.org/D118525
Previously, if a `#pragma clang assume_nonnull begin` was at the
end of a premable with a `#pragma clang assume_nonnull end` at the
end of the main file, clang would diagnose an unterminated begin in
the preamble and an unbalanced end in the main file.
With this change, those errors no longer occur and the case above is
now properly handled. I've added a corresponding test to clangd,
which makes use of preambles, in order to verify this works as
expected.
Differential Revision: https://reviews.llvm.org/D122179
This builtin returns the address of a global instance of the
`std::source_location::__impl` type, which must be defined (with an
appropriate shape) before calling the builtin.
It will be used to implement std::source_location in libc++ in a
future change. The builtin is compatible with GCC's implementation,
and libstdc++'s usage. An intentional divergence is that GCC declares
the builtin's return type to be `const void*` (for
ease-of-implementation reasons), while Clang uses the actual type,
`const std::source_location::__impl*`.
In order to support this new functionality, I've also added a new
'UnnamedGlobalConstantDecl'. This artificial Decl is modeled after
MSGuidDecl, and is used to represent a generic concept of an lvalue
constant with global scope, deduplicated by its value. It's possible
that MSGuidDecl itself, or some of the other similar sorts of things
in Clang might be able to be refactored onto this more-generic
concept, but there's enough special-case weirdness in MSGuidDecl that
I gave up attempting to share code there, at least for now.
Finally, for compatibility with libstdc++'s <source_location> header,
I've added a second exception to the "cannot cast from void* to T* in
constant evaluation" rule. This seems a bit distasteful, but feels
like the best available option.
Reviewers: aaron.ballman, erichkeane
Differential Revision: https://reviews.llvm.org/D120159
For header units we build the top level module directly from the header
that it represents and macros defined in this TU need to be emitted (when
such a definition is live at the end of the TU).
Differential Revision: https://reviews.llvm.org/D121097
Update `WeakUndeclaredIdentifiers` to hold a collection of weak
aliases per identifier instead of only one.
This also allows the "used" state to be removed from `WeakInfo`
because it is really only there as an alternative to removing
processed map entries, and we can represent that using an empty set
now. The serialization code is updated for the removal of the field.
Additionally, a PCH test is added for the new functionality.
The records are grouped by the "target" identifier, which was already
being used as a key for lookup purposes. We also store only one record
per alias name; combined, this means that diagnostics are grouped by
the "target" and limited to one per alias (which should be acceptable).
Fixes PR28611.
Fixesllvm/llvm-project#28985.
Reviewed By: aaron.ballman, cebowleratibm
Differential Revision: https://reviews.llvm.org/D121927
Co-authored-by: Rachel Craik <rcraik@ca.ibm.com>
Co-authored-by: Jamie Schmeiser <schmeise@ca.ibm.com>
Adds basic parsing/sema/serialization support for the
#pragma omp target parallel loop directive.
Differential Revision: https://reviews.llvm.org/D122359
Current ASTContext.getAttributedType() takes attribute kind,
ModifiedType and EquivType as the hash to decide whether an AST node
has been generated or note. But this is not enough for btf_type_tag
as the attribute might have the same ModifiedType and EquivType, but
still have different string associated with attribute.
For example, for a data structure like below,
struct map_value {
int __attribute__((btf_type_tag("tag1"))) __attribute__((btf_type_tag("tag3"))) *a;
int __attribute__((btf_type_tag("tag2"))) __attribute__((btf_type_tag("tag4"))) *b;
};
The current ASTContext.getAttributedType() will produce
an AST similar to below:
struct map_value {
int __attribute__((btf_type_tag("tag1"))) __attribute__((btf_type_tag("tag3"))) *a;
int __attribute__((btf_type_tag("tag1"))) __attribute__((btf_type_tag("tag3"))) *b;
};
and this is incorrect.
It is very difficult to use the current AttributedType as it is hard to
get the tag information. To fix the problem, this patch introduced
BTFTagAttributedType which is similar to AttributedType
in many ways but with an additional BTFTypeTagAttr. The tag itself can
be retrieved with BTFTypeTagAttr.
With the new BTFTagAttributed type, the debuginfo code can be greatly
simplified compared to previous TypeLoc based approach.
Differential Revision: https://reviews.llvm.org/D120296
With a sufficiently large output buffer, the only failure is Z_MEM_ERROR.
Check it and call the noreturn report_bad_alloc_error if applicable.
resize_for_overwrite may call report_bad_alloc_error as well.
Now that there is no other error type, we can replace the return type with void
and simplify call sites.
Reviewed By: ikudrin
Differential Revision: https://reviews.llvm.org/D121512
Since D106876, PCM files don't report module maps as input files unless they contributed to the compilation.
Reporting only module maps of (transitively) imported modules is not enough, though. For modules marked with `[no_undeclared_includes]`, other module maps affect the compilation by introducing anti-dependencies.
This patch makes sure such module maps are being reported as input files.
Depends on D120463.
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D120464
clang has support for lazy headers in module maps - if size and/or
modtime and provided in the cppmap file, headers are only resolved when
an include directive for a file with that size/modtime is encoutered.
Before this change, the lazy resolution was all-or-nothing per module.
That means as soon as even one file in that module potentially matched
an include, all lazy files in that module were resolved. With this
change, only files with matching size/modtime will be resolved.
The goal is to avoid unnecessary stat() calls on non-included files,
which is especially valuable on networked file systems, with higher
latency.
Differential Revision: https://reviews.llvm.org/D120569
This is an initial enabling patch for module partition support.
We add enumerations for partition interfaces/implementations.
This means that the module kind enumeration now occupies three
bits, so the AST streamer is adjusted for this. Adding one bit there
seems preferable to trying to overload the meanings of existing
kinds (and we will also want to add a C++20 header unit case later).
Differential Revision: https://reviews.llvm.org/D114714
Allocate on ASTContext, rather than just on heap, so that template
parameter lists are freed up.
Differential Revision: https://reviews.llvm.org/D120081
For redeclaration chains we maintain an invariant of having only a
single definition in the chain. In a single translation unit we make
sure not to create duplicates. But modules are separate translation
units and they can contain definitions for the same symbol
independently. When we load such modules together, we need to demote
duplicate definitions to keep the AST invariants.
Some AST clients are interested in distinguishing
declaration-that-was-demoted-from-definition and
declaration-that-was-never-a-definition. For that purpose introducing
`IsThisDeclarationADemotedDefinition`. No functional change intended.
rdar://84677782
Differential Revision: https://reviews.llvm.org/D118855
Recently we observed high memory pressure caused by clang during some parallel builds.
We discovered that we have several projects that have a large number of #define directives
in their TUs (on the order of millions), which caused huge memory consumption in clang due
to a lot of allocations for MacroInfo. We would like to reduce the memory overhead of
clang for a single #define to reduce the memory overhead for these files, to allow us to
reduce the memory pressure on the system during highly parallel builds. This change achieves
that by removing the SmallVector in MacroInfo and instead storing the tokens in an array
allocated using the bump pointer allocator, after all tokens are lexed.
The added unit test with 1000000 #define directives illustrates the problem. Prior to this
change, on arm64 macOS, clang's PP bump pointer allocator allocated 272007616 bytes, and
used roughly 272 bytes per #define. After this change, clang's PP bump pointer allocator
allocates 120002016 bytes, and uses only roughly 120 bytes per #define.
For an example test file that we have internally with 7.8 million #define directives, this
change produces the following improvement on arm64 macOS: Persistent allocation footprint for
this test case file as it's being compiled to LLVM IR went down 22% from 5.28 GB to 4.07 GB
and the total allocations went down 14% from 8.26 GB to 7.05 GB. Furthermore, this change
reduced the total number of allocations made by the system for this clang invocation from
1454853 to 133663, an order of magnitude improvement.
The recommit fixes the LLDB build failure.
Differential Revision: https://reviews.llvm.org/D117348
Recently we observed high memory pressure caused by clang during some parallel builds.
We discovered that we have several projects that have a large number of #define directives
in their TUs (on the order of millions), which caused huge memory consumption in clang due
to a lot of allocations for MacroInfo. We would like to reduce the memory overhead of
clang for a single #define to reduce the memory overhead for these files, to allow us to
reduce the memory pressure on the system during highly parallel builds. This change achieves
that by removing the SmallVector in MacroInfo and instead storing the tokens in an array
allocated using the bump pointer allocator, after all tokens are lexed.
The added unit test with 1000000 #define directives illustrates the problem. Prior to this
change, on arm64 macOS, clang's PP bump pointer allocator allocated 272007616 bytes, and
used roughly 272 bytes per #define. After this change, clang's PP bump pointer allocator
allocates 120002016 bytes, and uses only roughly 120 bytes per #define.
For an example test file that we have internally with 7.8 million #define directives, this
change produces the following improvement on arm64 macOS: Persistent allocation footprint for
this test case file as it's being compiled to LLVM IR went down 22% from 5.28 GB to 4.07 GB
and the total allocations went down 14% from 8.26 GB to 7.05 GB. Furthermore, this change
reduced the total number of allocations made by the system for this clang invocation from
1454853 to 133663, an order of magnitude improvement.
Differential Revision: https://reviews.llvm.org/D117348
ASTReader
This is a cleanup to reduce the lines of code to handle default template
argument in ASTReader.
Reviewed By: urnathan
Differential Revision: https://reviews.llvm.org/D118437
Currently we are trying to implement the semantics of C++ Modules. A big
challenge would be the ODR checking. Previously we did this in
ASTReader, it would handle the cases like:
```
module;
export module a_module;
import another_module; // check the ODR consistency here
```
or
```
export module m;
import a_module;
import another_module; // check the ODR consistency here
```
However, it wouldn't handle the case:
```
import another_module; // When we check ODR here, everything looks fine.
```
In the case, the read process is ended. But we need to check the ODR
still. To reuse the facility we do in ASTReader, this patch moves the
corresponding codes into ASTContext. This should be good since there
were facilities like `hasSameTemplateName` and `hasSameType`.
Although the patch is a little bit big, all of the change should be
trivial.
Reviewed By: erichkeane
Differential Revision: https://reviews.llvm.org/D118223
This patch replaces the exact include count of each file in `HeaderFileInfo` with a set of included files in `Preprocessor`.
The number of includes isn't a property of a header file but rather a preprocessor state. The exact number of includes is not used anywhere except statistic tracking.
Reviewed By: vsapsai
Differential Revision: https://reviews.llvm.org/D114095
The patch was reverted because it caused a crash during PCH build -- we
missed to update the RParenLoc in TreeTransform<Derived>::TransformAutoType.
This relands 55d96ac and 37ec65e with a test and fix.
This patch adds the support for `atomic compare` in parser. The support
in Sema and CodeGen will come soon. For now, it simply eimits an error when it
is encountered.
Reviewed By: ABataev
Differential Revision: https://reviews.llvm.org/D115561
This reverts commit cc56c66f27.
Fixed a bad assertion, the target of a UsingShadowDecl must not have
*local* qualifiers, but it can be a typedef whose underlying type is qualified.
Currently there's no way to find the UsingDecl that a typeloc found its
underlying type through. Compare to DeclRefExpr::getFoundDecl().
Design decisions:
- a sugar type, as there are many contexts this type of use may appear in
- UsingType is a leaf like TypedefType, the underlying type has no TypeLoc
- not unified with UnresolvedUsingType: a single name is appealing,
but being sometimes-sugar is often fiddly.
- not unified with TypedefType: the UsingShadowDecl is not a TypedefNameDecl or
even a TypeDecl, and users think of these differently.
- does not cover other rarer aliases like objc @compatibility_alias,
in order to be have a concrete API that's easy to understand.
- implicitly desugared by the hasDeclaration ASTMatcher, to avoid
breaking existing patterns and following the precedent of ElaboratedType.
Scope:
- This does not cover types associated with template names introduced by
using declarations. A future patch should introduce a sugar TemplateName
variant for this. (CTAD deduced types fall under this)
- There are enough AST matchers to fix the in-tree clang-tidy tests and
probably any other matchers, though more may be useful later.
Caveats:
- This changes a fairly common pattern in the AST people may depend on matching.
Previously, typeLoc(loc(recordType())) matched whether a struct was
referred to by its original scope or introduced via using-decl.
Now, the using-decl case is not matched, and needs a separate matcher.
This is similar to the case of typedefs but nevertheless both adds
complexity and breaks existing code.
Differential Revision: https://reviews.llvm.org/D114251
The compiler would judge two concepts is same by their addresses.
However, when we use modules, the addresses wouldn't be the same all the
time since one is parsed in their TU and another is imported in another
TU.
This patch fixes this by using isSameEntity to judge the two concepts.
Reviewed By: rsmith
Differential Revision: https://reviews.llvm.org/D114769
WG14 adopted the _ExtInt feature from Clang for C23, but renamed the
type to be _BitInt. This patch does the vast majority of the work to
rename _ExtInt to _BitInt, which accounts for most of its size. The new
type is exposed in older C modes and all C++ modes as a conforming
extension. However, there are functional changes worth calling out:
* Deprecates _ExtInt with a fix-it to help users migrate to _BitInt.
* Updates the mangling for the type.
* Updates the documentation and adds a release note to warn users what
is going on.
* Adds new diagnostics for use of _BitInt to call out when it's used as
a Clang extension or as a pre-C23 compatibility concern.
* Adds new tests for the new diagnostic behaviors.
I want to call out the ABI break specifically. We do not believe that
this break will cause a significant imposition for early adopters of
the feature, and so this is being done as a full break. If it turns out
there are critical uses where recompilation is not an option for some
reason, we can consider using ABI tags to ease the transition.
Eachempati.
This patch adds clang (parsing, sema, serialization, codegen) support for the 'depend' clause on the 'taskwait' directive.
Reviewed By: ABataev
Differential Revision: https://reviews.llvm.org/D113540
Problem:
PCM file includes references to all module maps used in compilation which created PCM. This problem leads to PCM-rebuilds in distributed compilations as some module maps could be missing in isolated compilation. (For example in our distributed build system we create a temp folder for every compilation with only modules and headers that are needed for that particular command).
Solution:
Add only affecting module map files to a PCM-file.
Reviewed By: rsmith
Differential Revision: https://reviews.llvm.org/D106876
Merge definition visibility the same way we do for other decls. Without
the fix the added test emits `-Wobjc-method-access` as it cannot find a
visible protocol. Make this warning `-Werror` so the test would fail
when protocol visibility regresses.
rdar://83600696
Differential Revision: https://reviews.llvm.org/D111860
For each selector encountered in the source code, we need to load
selectors from the imported modules and check that we are calling a
selector with compatible types.
At the moment, for each module we are storing methods declared in the
headers belonging to this module and methods from the transitive closure
of imported modules. When a module is imported by a few other modules,
methods from the shared module are duplicated in each importer. As the
result, we can end up with lots of identical methods that we try to add
to the global method pool. Doing this duplicate work is useless and
relatively expensive.
Avoid processing duplicate methods by storing in each module only its
own methods and not storing methods from dependencies. Collect methods
from dependencies by walking the graph of module dependencies.
The issue was discovered and reported by Richard Howell. He has done the
hard work for this fix as he has investigated and provided a detailed
explanation of the performance problem.
Differential Revision: https://reviews.llvm.org/D110123
We keep using the first encountered definition and need to take into
account visibility from subsequent definitions. For example, if the
first definition is hidden and the second is visible, we need to make
the first one visible too.
rdar://82263843
Differential Revision: https://reviews.llvm.org/D110453
While working on https://reviews.llvm.org/D110280 I've tried to merge
decl contexts as it seems to be correct and matching our handling of
decl contexts from different modules. It's not required for the fix in
https://reviews.llvm.org/D110280 but it revealed a missing diagnostic,
so separating this change into a separate commit.
Renamed some variables to distinguish diagnostic like "declaration of
'x' does not match" for different cases.
Differential Revision: https://reviews.llvm.org/D110287
Jonas Devlieghere