Alternatives to https://reviews.llvm.org/D153114.
Try to address https://github.com/clangd/clangd/issues/1293.
See the links for design ideas and the consensus so far. We want to have
some initial support in clang18.
This is the initial support for C++20 Modules in clangd.
As suggested by sammccall in https://reviews.llvm.org/D153114,
we should minimize the scope of the initial patch to make it easier
to review and understand so that every one are in the same page:
> Don't attempt any cross-file or cross-version coordination: i.e. don't
> try to reuse BMIs between different files, don't try to reuse BMIs
> between (preamble) reparses of the same file, don't try to persist the
> module graph. Instead, when building a preamble, synchronously scan
> for the module graph, build the required PCMs on the single preamble
> thread with filenames private to that preamble, and then proceed to
> build the preamble.
This patch reflects the above opinions.
# Testing in real-world project
I tested this with a modularized library:
https://github.com/alibaba/async_simple/tree/CXX20Modules. This library
has 3 modules (async_simple, std and asio) and 65 module units. (Note
that a module consists of multiple module units). Both `std` module and
`asio` module have 100k+ lines of code (maybe more, I didn't count). And
async_simple itself has 8k lines of code. This is the scale of the
project.
The result shows that it works pretty well, ..., well, except I need to
wait roughly 10s after opening/editing any file. And this falls in our
expectations. We know it is hard to make it perfect in the first move.
# What this patch does in detail
- Introduced an option `--experimental-modules-support` for the support
for C++20 Modules. So that no matter how bad this is, it wouldn't affect
current users. Following off the page, we'll assume the option is
enabled.
- Introduced two classes `ModuleFilesInfo` and
`ModuleDependencyScanner`. Now `ModuleDependencyScanner` is only used by
`ModuleFilesInfo`.
- The class `ModuleFilesInfo` records the built module files for
specific single source file. The module files can only be built by the
static member function `ModuleFilesInfo::buildModuleFilesInfoFor(PathRef
File, ...)`.
- The class `PreambleData` adds a new member variable with type
`ModuleFilesInfo`. This refers to the needed module files for the
current file. It means the module files info is part of the preamble,
which is suggested in the first patch too.
- In `isPreambleCompatible()`, we add a call to
`ModuleFilesInfo::CanReuse()` to check if the built module files are
still up to date.
- When we build the AST for a source file, we will load the built module
files from ModuleFilesInfo.
# What we need to do next
Let's split the TODOs into clang part and clangd part to make things
more clear.
The TODOs in the clangd part include:
1. Enable reusing module files across source files. The may require us
to bring a ModulesManager like thing which need to handle `scheduling`,
`the possibility of BMI version conflicts` and `various events that can
invalidate the module graph`.
2. Get a more efficient method to get the `<module-name> ->
<module-unit-source>` map. Currently we always scan the whole project
during `ModuleFilesInfo::buildModuleFilesInfoFor(PathRef File, ...)`.
This is clearly inefficient even if the scanning process is pretty fast.
I think the potential solutions include:
- Make a global scanner to monitor the state of every source file like I
did in the first patch. The pain point is that we need to take care of
the data races.
- Ask the build systems to provide the map just like we ask them to
provide the compilation database.
3. Persist the module files. So that we can reuse module files across
clangd invocations or even across clangd instances.
TODOs in the clang part include:
1. Clang should offer an option/mode to skip writing/reading the bodies
of the functions. Or even if we can requrie the parser to skip parsing
the function bodies.
And it looks like we can say the support for C++20 Modules is initially
workable after we made (1) and (2) (or even without (2)).
Renaming header guards to match the LLVM convention.
This patch was created by automatically applying the fixes from
clang-tidy.
I've removed the [NFC] tag from the title, as we're adding header guards in some files and thus might trigger behavior changes.
Differential Revision: https://reviews.llvm.org/D113896
When preamble contains #undef, indexing code finds the matching #define
and uses that during indexing. However, it would only look for local
definitions. If the macro was defined in a module, MacroInfo
would be nullptr and clangd would crash.
This change makes clangd ignore any #undef without a matching #define
inside the same TU.
The indexing of macros happens for preamble only, so then #undef must be
in the preamble, which is why we need two .h files in a test.
Note that clangd is currently not ready for module support, but this
brings us one step closer.
This was previously attempted in
4061d9e42cff621462931ac7df9666806c77a237, but had to be reverted due to
broken test. This version fixes that test-only bug by setting a custom module
cache path to avoid re-use of modules across test invocations.
Differential Revision: https://reviews.llvm.org/D85923
This reverts commit 4061d9e42cff621462931ac7df9666806c77a237.
Tests are failing in some configuration, likely due to not cleaning up
module cache path before running the test.
Differential Revision: https://reviews.llvm.org/D85907
Summary:
When preamble contains #undef, indexing code finds the matching #define
and uses that during indexing. However, it would only look for local
definitions. If the macro was defined in a module, MacroInfo
would be nullptr and clangd would crash.
This change makes clangd ignore any #undef without a matching #define
inside the same TU.
The indexing of macros happens for preamble only, so then #undef must be
in the preamble, which is why we need two .h files in a test.
Note that clangd is currently not ready for module support, but this
brings us one step closer.
Reviewers: sammccall
Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D80525
Summary:
The Provider extension point is designed to also be implemented by
ClangdLSPServer (to inject config-over-lsp) and likely by embedders.
Reviewers: kadircet
Subscribers: mgorny, ilya-biryukov, MaskRay, jkorous, arphaman, jfb, usaxena95, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D82964
Summary:
By making all overloads non-virtual and delegating to a differently-named
private method, we avoid any (harmless) name-hiding in the subclasses.
Reviewers: kadircet
Subscribers: kristof.beyls, ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits, Quuxplusone, dblaikie
Tags: #clang
Differential Revision: https://reviews.llvm.org/D82793
Summary:
Clangd uses FSProvider to get threadsafe views into file systems. This
patch changes naming to make that more explicit.
Depends on D81920
Reviewers: sammccall
Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D81998
Summary:
We've faced a couple of problems when the returned FS didn't have the
proper working directory. New signature makes the API safer against such
problems.
Reviewers: sammccall
Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D81920
This was reverted in rL365678, the failure was due to YAML parsing of
compile_commands.json.
Converting backslashes to forward slashes to fix the issue in unittest.
llvm-svn: 365748
Summary:
Motivation:
- this layout is a pain to work with
- without a common root, it's painful to express things like "disable clangd" (D61122)
- CMake/lit configs are a maintenance hazard, and the more the one-off hacks
for various tools are entangled, the more we see apathy and non-ownership.
This attempts to use the bare-minimum configuration needed (while still
supporting the difficult cases: windows, standalone clang build, dynamic libs).
In particular the lit.cfg.py and lit.site.cfg.py.in are merged into lit.cfg.in.
The logic in these files is now minimal.
(Much of clang-tools-extra's lit configs can probably be cleaned up by reusing
lit.llvm.llvm_config.use_clang(), and every llvm project does its own version of
LDPATH mangling. I haven't attempted to fix any of those).
Docs are still in clang-tools-extra/docs, I don't have any plans to touch those.
Reviewers: gribozavr
Subscribers: mgorny, javed.absar, MaskRay, jkorous, arphaman, kadircet, jfb, cfe-commits, ilya-biryukov, thakis
Tags: #clang
Differential Revision: https://reviews.llvm.org/D61187
llvm-svn: 359424
