[5.5][Dependency Scanning] Cherry-pick dependency scanner changes required for Explicit Module Builds #38704
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…-Module Dependencies Cache - Adds serialization format based on the LLVM Bitcode File Format (https://llvm.org/docs/BitCodeFormat.html). - Adds Serialization and Deserialization code.
…serialize and deserialize dependency scanner cache from a `.moddepcache` file. Using the serialization format added in swiftlang#37585. - Add load/save code for the `-scan-dependencies` code-path. - Add `libSwiftDriver` entry-points to load/store the cache of a given scanner instance.
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…to current search paths only. The dependency scanner's cache persists across different queries and answering a subsequent query's module lookup with a module not in the query's search path is not correct. For example, suppose we are looking for a Swift module `Foo` with a set of search paths `SP`. And dependency scanner cache already contains a module `Foo`, for which we found an interface file at location `L`. If `L`∉`SP`, then we cannot re-use the cached entry because we’d be resolving the scanning query to a filesystem location that the current scanning context is not aware of. Resolves rdar://81175942
Swift module building commands need -sdk because dependencies sometimes use sdk-relative paths (prebuilt modules for example). Without -sdk, the command will not be able to local these dependencies, leading to unnecessary rebuilding from textual interfaces. rdar://81177968
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nkcsgexi
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…nt scan cache & global. This change causes the cache to be layered with a local "cache" that wraps the global cache, which will serve as the source of truth. The local cache persists only for the duration of a given scanning action, and has a store of references to dependencies resolved as a part of the current scanning action only, while the global cache is the one that persists across scanning actions (e.g. in `DependencyScanningTool`) and stores actual module dependency info values. Only the local cache can answer dependency lookup queries, checking current scanning action results first, before falling back to querying the global cache, with queries disambiguated by the current scannning action's search paths, ensuring we never resolve a dependency lookup query with a module info that could not be found in the current action's search paths. This change is required because search-path disambiguation can lead to false-negatives: for example, the Clang dependency scanner may find modules relative to the compiler's path that are not on the compiler's direct search paths. While such false-negative query responses should be functionally safe, we rely on the current scanning action's results being always-present-in-the-cache for the scanner's functionality. This layering ensures that the cache use-sites remain unchanged and that we get both: preserved global state which can be queried disambiguated with the search path details, and an always-consistent local (current action) cache state.
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airspeedswift
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#38684: [Dependency Scanning] include -sdk in Swift module building command
#38703: [Dependency Scanning] Have the scanner cache answer queries relevant to current search paths only.
#37723: [Dependency Scanning] Add ability for
-scan-dependenciesaction to serialize and deserialize dependency scanner cache from a.moddepcachefile. Using the serialization format added in #37585.#37585: [Dependency Scanning] Add a binary serialization format for the Inter-Module Dependencies Cache
#38710: Frontend: remove -swift-module-file. NFC
#38761: [Dependency Scanning] Split the ModuleDependencyCache into two: current scan cache & global.