The minimizing filesystem used by the dependency scanner isn't great when it comes to the consistency of its caches. There are two problems that can be exposed by a filesystem that changes during dependency scan:
1. In-memory cache entries for original and minimized files are distinct, populated at different times using separate stat/open syscalls. This means that when a file is read with minimization disabled, its contents might be inconsistent when the same file is read with minimization enabled at later point (and vice versa).
2. In-memory cache entries are indexed by filename. This is problematic for symlinks, where the contents of the symlink might be inconsistent with contents of the original file (for the same reason as in problem 1).
This patch ensures consistency by always stating/reading a file exactly once. The original contents are always cached and minimized contents are derived from that on demand. The cache entries are now indexed by their `UniqueID` ensuring consistency for symlinks too. Moreover, the stat/read syscalls are now issued outside of critical section.
Depends on D115935.
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D114966
The minimizing and caching filesystem used by the dependency scanner keeps minimized and original files in separate caches.
This setup is not well suited for dealing with files that are sometimes minimized and sometimes not. Such files are being stat-ed and read twice, which is wasteful and also means the two versions of the file can get "out of sync".
This patch squashes the two caches together. When a file is stat-ed or read, its original contents are populated. If a file needs to be minimized, we give the minimizer the already loaded contents instead of reading the file again.
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D115346
The filesystem used during dependency scanning does two things: it caches file entries and minimizes source file contents. We use the term "ignored file" in a couple of places, but it's not clear what exactly that means. This commit clears up the semantics, explicitly spelling out this relates to minimization.
This moves the registry higher in the LLVM library dependency stack.
Every client of the target registry needs to link against MC anyway to
actually use the target, so we might as well move this out of Support.
This allows us to ensure that Support doesn't have includes from MC/*.
Differential Revision: https://reviews.llvm.org/D111454
This patch separates the local and global caches of `DependencyScanningFilesystem` into two buckets: minimized files and original files. This is necessary to deal with precompiled modules/headers.
Consider a single worker with its instance of filesystem:
1. Build system uses the worker to scan dependencies of module A => filesystem cache gets populated with minimized input files.
2. Build system uses the results to explicitly build module A => explicitly built module captures the state of the real filesystem (containing non-minimized input files).
3. Build system uses the prebuilt module A as an explicit precompiled dependency for another compile job B.
4. Build system uses the same worker to scan dependencies for job B => worker uses implicit modular build to discover dependencies, which validates the filesystem state embedded in the prebuilt module (non-minimized files) to the current view of the filesystem (minimized files), resulting in validation failures.
This problem can be avoided in step 4 by collecting input files from the precompiled module and marking them as "ignored" in the minimizing filesystem. This way, the validation should succeed, since we should be always dealing with the original (non-minized) input files. However, the filesystem already minimized the input files in step 1 and put it in the cache, which gets used in step 4 as well even though it's marked ignored (do not minimize). This patch essentially fixes this oversight by making the `"file is minimized"` part of the cache key (from high level).
Depends on D106064.
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D106146
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.
This fixes the issue where a filename dependendency was missing if the file that
was referenced with __has_include() was accessed through a symlink in an earlier run,
if the file manager was reused between runs.
llvm-svn: 370081
This fixes the issue where a filename dependendency was missing if the file that
was skipped was included through a symlink in an earlier run, if the file
manager was reused between runs.
llvm-svn: 369998
when the FileManager is reused across invocations
This commit introduces a parallel API to FileManager's getFile: getFileEntryRef, which returns
a reference to the FileEntry, and the name that was used to access the file. In the case of
a VFS with 'use-external-names', the FileEntyRef contains the external name of the file,
not the filename that was used to access it.
The new API is adopted only in the HeaderSearch and Preprocessor for include file lookup, so that the
accessed path can be propagated to SourceManager's FileInfo. SourceManager's FileInfo now can report this accessed path, using
the new getName method. This API is then adopted in the dependency collector, which now correctly reports dependencies when a file
is included both using a symlink and a real path in the case when the FileManager is reused across multiple Preprocessor invocations.
Note that this patch does not fix all dependency collector issues, as the same problem is still present in other cases when dependencies
are obtained using FileSkipped, InclusionDirective, and HasInclude. This will be fixed in follow-up commits.
Differential Revision: https://reviews.llvm.org/D65907
llvm-svn: 369680
Jan Svoboda