The locations stored in .swiftsourceinfo included the presumed file,
line, and column. When a location is requested it would read these, open
the external file, create a line map, and find the offset corresponding
to that line/column.
The offset is known during serialization though, so output it as well to
avoid having to read the file and generate the line map.
Since the serialized location is returned from `Decl::getLoc()`, it
should not be the presumed location. Instead, also output the line
directives so that the presumed location can be built as per normal
locations.
Finally, move the cache out of `Decl` and into `ASTContext`, since very
few declarations will actually have their locations deserialized. Make
sure to actually write to that cache so it's used - the old cache was
never written to.
- Add DocRangesLayout to the `.swiftsourceinfo`.
This is a blob containing an array of `SingleRawComment`
source locations.
- Add DocLocWriter for serializing `SingleRawComment` locs into the
`DocLocsLayout` buffer.
Serialize start line, start column, and length of `SingleRawComment`
pieces in `.swiftsourceinfo`
- Read doc locs when loading basic declaration locs from a ModuleFile.
- Load `DOC_LOCS` blob into ModuleFile::DocLocsData
- Reconstitute RawComment ranges when available from .swiftsourceinfo
- Allow requesting serialized raw comment if available
rdar://problem/58339492
After this change, we only use one single hash table for USR to USR id
mapping. The basic source locations are an array of fixed length
records that could be retrieved by using the USR id since each
USR id is guaranteed to be associated with one basic location entry.
The source file paths are refactored to a blob of 0-terminated strings.
Decl locations use offset in this blob to refer to the source file path
where the decl was defined.
After setting up the .swiftsourceinfo file, this patch starts to actually serialize
and de-serialize source locations for declaration. The binary format of .swiftsourceinfo
currently contains these three records:
BasicDeclLocs: a hash table mapping from a USR ID to a list of basic source locations. The USR id
could be retrieved from the following DeclUSRs record using an actual decl USR. The basic source locations
include a file ID and the results from Decl::getLoc(), ValueDecl::getNameLoc(), Decl::getStartLoc() and Decl::getEndLoc().
The file ID could be used to retrieve the actual file name from the following SourceFilePaths record.
Each location is encoded as a line:column pair.
DeclUSRS: a hash table mapping from USR to a USR ID used by location records.
SourceFilePaths: a hash table mapping from a file ID to actual file name.
BasicDeclLocs should be sufficient for most diagnostic cases. If additional source locations
are needed, we could always add new source location records without breaking the backward compatibility.
When de-serializing the source location from a module-imported decl, we calculate its USR, retrieve the USR ID
from the DeclUSRS record, and use the USR ID to look up the basic location list in the BasicDeclLocs record.
For more details about .swiftsourceinfo file: https://forums.swift.org/t/proposal-emitting-source-information-file-during-compilation
