With the new option, when doing caching we write the hash that we already
computed for the main output file to an extended attribute (xattr) on the file.
This is equivalent to clang's -fwrite-output-hash-xattr option.
The format of the xattr is
name: com.apple.clang.cas_output_hash
data:
* Null-terminated hash schema name, e.g. llvm.builtin.v2[BLAKE3].
* Hash length (4 bytes, little-endian).
* Hash bytes
rdar://171185394
Migrate all callers of getOrCreateDatabases to either create their own CAS
instances using createDatabases() or to use the ones stored in the
CompilerInstance. Also forwards the instances into the ClangImporter and its
various clang::CompilerInstance instances.
Validated locally that this does not result in any additional calls to
createDatabases across all the swift tests. In fact, there are fewer due to an
improvement on the clange side, so I also checked that the overall reduction
doesn't hide any issues. Looking at individual cas paths that are opened, which
are per-test paths, there are none that open more than before.
There were two cache replay code exists, one for cache replay from
swift-frontend, the other for replay using C API from libSwiftScan. It
is easy to forget to update one copy when new specialized cache replay
logic is added for some output kinds. Now unify the replay logics to a
single location to avoid confusion. This is a rewrite of the existing
logic and NFCI.
Argyrios Kyrtzidis
Argyrios Kyrtzidis
Ben Langmuir
Anthony Latsis
Steven Wu
Artem Chikin