Commit Graph

447 Commits

Author SHA1 Message Date
Kirill Bobyrev 4645ef17ff
[clangd] Add CMake dependencies for Protobuf-generated files
Summary:
Dependencies ensure that Protobufs are generated before all libraries
depending on the headers are **built**, not linked.

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: mgorny, ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D79085
2020-04-29 17:01:03 +02:00
Sam McCall ad97ccf6b2 [clangd] Move non-clang base pieces into separate support/ lib. NFCI
Summary:
This enforces layering, reduces a sprawling clangd/ directory, and makes life
easier for embedders.

Reviewers: kbobyrev

Subscribers: mgorny, ilya-biryukov, javed.absar, MaskRay, jkorous, arphaman, jfb, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D79014
2020-04-29 15:57:12 +02:00
Richard Smith c35f3f8679 Fix up clangd after clang commit llvmorg-11-init-13375-g0a088ead85f.
It's not clear whether clangd should really consider #import to mark a
header as self-contained or not, but this change preserves the old (and
unit-tested) behavior.
2020-04-28 23:49:35 -07:00
Sam McCall 4e769e93b9 Reland "Add a facility to get system cache directory and use it in clangd"
This reverts commit faf2dce1dd.
2020-04-29 00:56:36 +02:00
Eric Christopher faf2dce1dd Temporarily revert "Add a facility to get system cache directory and use it in clangd"
This reverts commit ad38f4b371.

As it broke building the unittests:

.../sources/llvm-project/llvm/unittests/Support/Path.cpp:334:5: error: use of undeclared identifier 'set'
    set(Value);
    ^
1 error generated.
2020-04-28 15:49:46 -07:00
Vojtěch Štěpančík ad38f4b371 Add a facility to get system cache directory and use it in clangd
Summary:
This patch adds a function that is similar to `llvm::sys::path::home_directory`, but provides access to the system cache directory.

For Windows, that is %LOCALAPPDATA%, and applications should put their files under %LOCALAPPDATA%\Organization\Product\.

For *nixes, it adheres to the XDG Base Directory Specification, so it first looks at the XDG_CACHE_HOME environment variable and falls back to ~/.cache/.

Subsequently, the Clangd Index storage leverages this new API to put index files somewhere else than the users home directory.

Fixes https://github.com/clangd/clangd/issues/341

Reviewers: sammccall, chandlerc, Bigcheese

Reviewed By: sammccall

Subscribers: hiraditya, ilya-biryukov, MaskRay, jkorous, dexonsmith, arphaman, kadircet, ormris, usaxena95, cfe-commits, llvm-commits

Tags: #clang-tools-extra, #clang, #llvm

Differential Revision: https://reviews.llvm.org/D78501
2020-04-28 23:18:31 +02:00
Kirill Bobyrev 9ff3f339e8
[clangd] Fix remote index build without shared libs mode
Summary:
Generated Protobuf library has to be in CLANG_EXPORTS and should also be
installed appropriately. The easiest way to do that is via CMake's
add_clang_library. That unfortunately applies "one directory - one
clang_(library|tool)" policy so .proto files should be in a separate directory
and complicates the layout.

This setup works both in shared and static libs mode.

Resolves: https://github.com/clangd/clangd/issues/351

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: mgorny, ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D78885
2020-04-28 19:16:37 +02:00
Kirill Bobyrev 9774c34a84 [clangd] NFC: Omit deduced template parameters
Related revision: D78521
2020-04-24 14:27:39 +02:00
Kirill Bobyrev 1ccfe475a7 [clangd] Fix build when CLANGD_REMOTE is not enabled 2020-04-24 14:07:39 +02:00
Kirill Bobyrev 67b2dbd5a3 [clangd] Extend dexp to support remote index
Summary:
* Merge clangd-remote-client into dexp
* Implement `clangd::remote::IndexClient` that is derived from `SymbolIndex`
* Upgrade remote mode-related CMake infrastructure

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: mgorny, ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78521
2020-04-24 13:59:21 +02:00
Sam McCall 098e40eac5 [clangd] Add index export to dexp
Summary: Add a command to dexp that exports index data in chosen format (e.g. YAML).

Reviewers: sammccall

Subscribers: kbobyrev, mgorny, ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang-tools-extra, #clang

Differential Revision: https://reviews.llvm.org/D77385
2020-04-19 14:34:46 +02:00
Sam McCall 8c68de2d63 [clangd] Extend YAML Serialization
Reviewers: sammccall

Reviewed By: sammccall

Subscribers: mgorny, ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang-tools-extra, #clang

Differential Revision: https://reviews.llvm.org/D77938
2020-04-19 14:32:31 +02:00
Kadir Cetinkaya 4503cf5f23
[clangd] Drop dangling relations while sharding
Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78359
2020-04-17 13:57:32 +02:00
Kirill Bobyrev cee80c0489 [clangd] Pull installed gRPC and introduce clangd-remote-(server|client)
Summary:
This patch allows using installed gRPC to build two simple tools which
currently provide the functionality of looking up the symbol by name.
remote-index-client is a simplified version of dexp which connects to
remote-index-server passes lookup requests.

I also significantly reduced the scope of this patch to prevent large changelist
and more bugs. The next steps would be:

* Extending Protocol for deep copies of Symbol and inherit RemoteIndex from
  Index to unify the interfaces
* Make remote-index-server more generic and merge the remote index client with
  dexp
* Modify Clangd to allow using remote index instead of the local one for all
  global index requests

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: mgorny, ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77794
2020-04-16 13:55:08 +02:00
Kirill Bobyrev f058673397 [dexp] NFC: Change positional argument format
Summary:
Before:

  USAGE: dexp [options] --index-path Path to the index

After:

  USAGE: dexp [options] <INDEX FILE>

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78089
2020-04-15 13:28:07 +02:00
Kadir Cetinkaya 2cd0be02b9
[clangd] Fix MSVC compile error, attempt 2 2020-04-15 09:33:12 +02:00
Kadir Cetinkaya 6d53897554
[clangd] Fix MSVC builds 2020-04-15 09:24:58 +02:00
Kadir Cetinkaya dffa9dfbda
[clangd] Shard preamble symbols in dynamic index
Summary:
This reduces memory usage by dynamic index from more than 400MB to 32MB
when all files in clang-tools-extra/clangd/*.cpp are active in clangd.

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77732
2020-04-15 09:10:10 +02:00
Sam McCall 49268a678c [clangd] Support dexp -c "some command"
Summary:
It runs one command and exits.
See D77385 for motivation.

Reviewers: mnauw, kbobyrev

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77645
2020-04-08 14:02:49 +02:00
Kazuaki Ishizaki dd5571d51a [clang-tools-extra] NFC: Fix trivial typo in documents and comments
Differential Revision: https://reviews.llvm.org/D77458
2020-04-05 15:28:40 +09:00
Benjamin Kramer 4065e92195 Upgrade some instances of std::sort to llvm::sort. NFC. 2020-03-28 19:23:29 +01:00
Sam McCall 2cd33e6fe6 [clangd] Track document versions, include them with diags, enhance logs
Summary:
This ties to an LSP feature (diagnostic versioning) but really a lot
of the value is in being able to log what's happening with file versions
and queues more descriptively and clearly.

As such it's fairly invasive, for a logging patch :-\

Key decisions:
 - at the LSP layer, we don't reqire the client to provide versions (LSP
   makes it mandatory but we never enforced it). If not provided,
   versions start at 0 and increment. DraftStore handles this.
 - don't propagate magically using contexts, but rather manually:
   addDocument -> ParseInputs -> (ParsedAST, Preamble, various callbacks)
   Context-propagation would hide the versions from ClangdServer, which
   would make producing good log messages hard
 - within ClangdServer, treat versions as opaque and unordered.
   std::string is a convenient type for this, and allows richer versions
   for embedders. They're "mandatory" but "null" is a reasonable default.

Subscribers: ilya-biryukov, javed.absar, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75582
2020-03-05 01:22:32 +01:00
Haojian Wu 5560a78820 [clangd] Bump index version number.
Summary:
Though we don't have new changes to the index format, we have changes to
symbol collector, e.g. collect marcos, spelled references. Bump the
version to force background-index to rebuild.

Reviewers: kadircet

Reviewed By: kadircet

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74127
2020-02-26 13:43:16 +01:00
Alexandre Ganea 8404aeb56a [Support] On Windows, ensure hardware_concurrency() extends to all CPU sockets and all NUMA groups
The goal of this patch is to maximize CPU utilization on multi-socket or high core count systems, so that parallel computations such as LLD/ThinLTO can use all hardware threads in the system. Before this patch, on Windows, a maximum of 64 hardware threads could be used at most, in some cases dispatched only on one CPU socket.

== Background ==
Windows doesn't have a flat cpu_set_t like Linux. Instead, it projects hardware CPUs (or NUMA nodes) to applications through a concept of "processor groups". A "processor" is the smallest unit of execution on a CPU, that is, an hyper-thread if SMT is active; a core otherwise. There's a limit of 32-bit processors on older 32-bit versions of Windows, which later was raised to 64-processors with 64-bit versions of Windows. This limit comes from the affinity mask, which historically is represented by the sizeof(void*). Consequently, the concept of "processor groups" was introduced for dealing with systems with more than 64 hyper-threads.

By default, the Windows OS assigns only one "processor group" to each starting application, in a round-robin manner. If the application wants to use more processors, it needs to programmatically enable it, by assigning threads to other "processor groups". This also means that affinity cannot cross "processor group" boundaries; one can only specify a "preferred" group on start-up, but the application is free to allocate more groups if it wants to.

This creates a peculiar situation, where newer CPUs like the AMD EPYC 7702P (64-cores, 128-hyperthreads) are projected by the OS as two (2) "processor groups". This means that by default, an application can only use half of the cores. This situation could only get worse in the years to come, as dies with more cores will appear on the market.

== The problem ==
The heavyweight_hardware_concurrency() API was introduced so that only *one hardware thread per core* was used. Once that API returns, that original intention is lost, only the number of threads is retained. Consider a situation, on Windows, where the system has 2 CPU sockets, 18 cores each, each core having 2 hyper-threads, for a total of 72 hyper-threads. Both heavyweight_hardware_concurrency() and hardware_concurrency() currently return 36, because on Windows they are simply wrappers over std:🧵:hardware_concurrency() -- which can only return processors from the current "processor group".

== The changes in this patch ==
To solve this situation, we capture (and retain) the initial intention until the point of usage, through a new ThreadPoolStrategy class. The number of threads to use is deferred as late as possible, until the moment where the std::threads are created (ThreadPool in the case of ThinLTO).

When using hardware_concurrency(), setting ThreadCount to 0 now means to use all the possible hardware CPU (SMT) threads. Providing a ThreadCount above to the maximum number of threads will have no effect, the maximum will be used instead.
The heavyweight_hardware_concurrency() is similar to hardware_concurrency(), except that only one thread per hardware *core* will be used.

When LLVM_ENABLE_THREADS is OFF, the threading APIs will always return 1, to ensure any caller loops will be exercised at least once.

Differential Revision: https://reviews.llvm.org/D71775
2020-02-14 10:24:22 -05:00
Haojian Wu b1309a18ba [clangd] Print the Spelled RefKind. 2020-02-13 13:28:11 +01:00
Haojian Wu ca9fd22adb [clangd] Set "spelled" flag for constructor references.
Summary:
DeclarationName for cxx constructor is special, it is not an identifier.
thus the "Spelled" flag are not set for all ctor references, this patch
fixes it.

Reviewers: kbobyrev

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74125
2020-02-06 16:59:45 +01:00
Kirill Bobyrev a6860c1af4
[clangd] Add a flag for spelled references in the Index
This patch allows the index does to provide a way to distinguish
implicit references (e.g. coming from macro expansions) from the spelled
ones. The corresponding flag was added to RefKind and symbols that are
referenced without spelling their name explicitly are now marked
implicit. This allows fixing incorrect behavior when renaming a symbol
that was referenced in macro expansions would try to rename macro
invocations.

Differential Revision: D72746

Reviewed by: hokein
2020-02-06 08:18:14 +01:00
Haojian Wu f8865c0194 [clangd] Pull out a isProtoFile function.
Reviewers: kadircet

Reviewed By: kadircet

Subscribers: merge_guards_bot, mgorny, ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73780
2020-02-05 12:04:03 +01:00
Benjamin Kramer adcd026838 Make llvm::StringRef to std::string conversions explicit.
This is how it should've been and brings it more in line with
std::string_view. There should be no functional change here.

This is mostly mechanical from a custom clang-tidy check, with a lot of
manual fixups. It uncovers a lot of minor inefficiencies.

This doesn't actually modify StringRef yet, I'll do that in a follow-up.
2020-01-28 23:25:25 +01:00
Sam McCall 7d20e80225 [clangd] Show background index status using LSP 3.15 work-done progress notifications
Summary:
It simply shows the completed/total items on the background queue, e.g.
 indexing: 233/1000
The denominator is reset to zero every time the queue goes idle.

The protocol is fairly complicated here (requires creating a remote "progress"
resource before sending updates). We implement the full protocol, but I've added
an extension allowing it to be skipped to reduce the burden on clients - in
particular the lit test takes this shortcut.

The addition of background index progress to DiagnosticConsumer seems ridiculous
at first glance, but I believe that interface is trending in the direction of
"ClangdServer callbacks" anyway. It's due for a rename, but otherwise actually
fits.

Reviewers: kadircet, usaxena95

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, jfb, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D73218
2020-01-24 12:21:08 +01:00
Utkarsh Saxena 583ba07884 [clangd] Add xref for macros to FileIndex.
Summary:
Adds macro references to the dynamic index.
Tests added.
Also exposed a new API to convert path to URI in URI.h

Reviewers: hokein

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D71406
2020-01-08 08:27:50 +01:00
Kazuaki Ishizaki b7ecf1c1c3 NFC: Fix trivial typos in comments 2020-01-04 10:28:41 -05:00
Mark de Wever 8dc7b982b4 [NFC] Fixes -Wrange-loop-analysis warnings
This avoids new warnings due to D68912 adds -Wrange-loop-analysis to -Wall.

Differential Revision: https://reviews.llvm.org/D71857
2020-01-01 20:01:37 +01:00
Kirill Bobyrev 3b9715cb21 [NFC] Fix typos in Clangd and Clang
Reviewed by: Jim

Differential Revision: https://reviews.llvm.org/D71455
2019-12-16 10:54:40 +01:00
Ilya Biryukov b63c35ebf7 [clangd] Simplify code using findName. NFC
`findName` was always used in conjuction with `spellingLocIfSpelled`.
This patch replaces patterns of the form:
  spellingLocIfSpelled(findName(&ND), SM)

With a new helper function:
  nameLocation(ND, SM)

And removes `spellingLocIfSpelled` and `findName`. Both are never used
anywhere else and the latter is an equivalent of `Decl::getLocation` if
we ever need it again.
2019-12-10 10:22:43 +01:00
Haojian Wu decdbc1155 [clangd] Use expansion location when the ref is inside macros.
Summary:
Previously, xrefs has inconsistent behavior when the reference is inside
macro body:
- AST-based xrefs (for main file) uses the expansion location;
- our index uses the spelling location;

This patch makes our index use file locations for references, which is
consistent with AST-based xrefs, and kythe as well.

After this patch, memory usage of static index on LLVM increases ~5%.

Reviewers: ilya-biryukov

Subscribers: merge_guards_bot, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70480
2019-12-09 16:34:01 +01:00
Utkarsh Saxena 9347655a27 [clangd] Add xref for macro to static index.
Summary:
This adds the references for macros to the SymbolCollector (used for static index).
Enabled if `CollectMacro` option is set.

Reviewers: hokein

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70489
2019-12-05 04:23:18 +01:00
Nico Weber 6f773205cd Revert "Use InitLLVM to setup a pretty stack printer"
This reverts commit 3f76260dc0.
Breaks at least these tests on Windows:
    Clang :: Driver/clang-offload-bundler.c
    Clang :: Driver/clang-offload-wrapper.c
2019-11-25 21:06:56 -05:00
Rui Ueyama 3f76260dc0 Use InitLLVM to setup a pretty stack printer
InitLLVM does not only save a few lines from main() but also makes the
commands do the right thing for multibyte character pathnames on
Windows (i.e. canonicalize argv's to UTF-8) because of the code we
have in this file:

https://github.com/llvm/llvm-project/blob/master/llvm/lib/Support/InitLLVM.cpp#L32

For many LLVM commands, we already have calls of InitLLVM, but there
are still remainings.

Differential Revision: https://reviews.llvm.org/D70702
2019-11-26 10:56:10 +09:00
Reid Kleckner 979da9a4c3 Avoid including Builtins.h in Preprocessor.h
Builtins are rarely if ever accessed via the Preprocessor. They are
typically found on the ASTContext, so there should be no performance
penalty to using a pointer indirection to store the builtin context.
2019-11-15 16:45:16 -08:00
Haojian Wu b221c9d09d [clangd] Replace getLangOpts().isHeaderFile usage with isHeaderFile helper.
Summary:
The helper is more correct to detect header file, this would fix our
issues caused by false positive before.

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: merge_guards_bot, ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70299
2019-11-15 16:28:10 +01:00
Haojian Wu 509efe5d8e [clangd] Add isHeaderFile helper.
Summary:
we have a few places using `ASTCtx.getLangOpts().IsHeaderFile` to
determine a header file, but it relies on "-x c-header" compiler flag,
if the compilation command doesn't have this flag, we will get a false
positive. We are encountering this issue in bazel build system.

To solve this problem, we infer the file from file name, actual changes will
come in follow-ups.

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70235
2019-11-15 16:18:27 +01:00
Ilya Biryukov 5a9547b007 [clangd] Simplify the code in Index::refs
Summary:
While here, also fix potential UB in MergeIndex.

Thanks Kadir for finding this!

Reviewers: hokein

Reviewed By: hokein

Subscribers: merge_guards_bot, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70225
2019-11-14 14:43:29 +01:00
Haojian Wu 33e882d5ad [clangd] Add bool return type to Index::refs API.
Summary:
Similar to fuzzyFind, the bool indicates whether there are more xref
results.

Reviewers: ilya-biryukov

Reviewed By: ilya-biryukov

Subscribers: merge_guards_bot, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70139
2019-11-13 14:42:30 +01:00
Utkarsh Saxena 02ec6ff77e [clangd] Use name of Macro to compute its SymbolID, NFC.
Summary:
We use the name from the IdentifierInfo of the Macro to compute its
SymbolID. It is better to just take the Name as a parameter to avoid
storing the IdentifierInfo whenever we need the SymbolID for the Macro.

Patch by UTKARSH SAXENA!

Reviewers: hokein

Reviewed By: hokein

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D69937
2019-11-11 12:38:49 +01:00
Haojian Wu 41104a9406 [clangd] Fix a regression of not showing documentation from forward declarations.
Summary:
There is a regression from https://reviews.llvm.org/D68467. Unlike class
forward declarations, function ducomentation is written in the declaration in
headers, the function definition doesn't contain any documentation, cases like:

```
foo.h
// this is foo.
void foo();
foo.cc

void foo() {}
```
we should still show documentation from the foo declaration.

Reviewers: ilya-biryukov

Reviewed By: ilya-biryukov

Subscribers: MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D69961
2019-11-11 10:46:52 +01:00
Ilya Biryukov 0019684900 [clangd] Set RetainCommentsFromSystemHeaders to true
clangd should retain comments from system headers.

fixes https://github.com/clangd/clangd/issues/96

Patch by lh123!

Differential revision: https://reviews.llvm.org/D69928
2019-11-07 09:54:20 +01:00
Haojian Wu bf71e4fe0a [clangd] Collect name references in the index.
Summary:
This is used for cross-file rename. When renaming a class, we expect to
rename all related constructors/destructors.

Reviewers: kadircet, ilya-biryukov

Subscribers: MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D69338
2019-10-24 10:25:16 +02:00
Haojian Wu c8e3f43ab5 [clangd] Use our own relation kind.
Summary:
Move the RelationKind from Serialization.h to Relation.h. This patch doesn't
introduce any breaking changes.

Reviewers: kadircet

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D68981

llvm-svn: 375117
2019-10-17 14:08:28 +00:00
Sam McCall 368e0f3757 [clangd] If an undocumented definition exists, don't accept documentation from other forward decls.
Summary:
This fixes cases like:
  foo.h
    class Undocumented{}
  bar.h
    // break an include cycle. we should refactor this!
    class Undocumented;
Where the comment doesn't describe the class.

Note that a forward decl that is *visible to the definition* will still have
its doc comment used, by SymbolCollector: Merge isn't involved here.

Reviewers: ilya-biryukov

Subscribers: MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D68467

llvm-svn: 373892
2019-10-07 10:53:56 +00:00