[clang][deps] Lazy dependency directives rdar://125519128 #8494
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Since b4c83a1, `Preprocessor` and `Lexer` are aware of the concept of scanning dependency directives. This makes it possible to scan for them on-demand rather than eagerly on the first filesystem operation (open, or even just stat). This might improve performance, but is also necessary for the "PCH as module" mode. Some precompiled header sources use the ".pch" file extension, which means they were not getting scanned for dependency directives. This was okay when the PCH was the main input file in a separate scan step, because there we just lex the file in a scanning-specific frontend action. But when such source gets treated as a module implicitly loaded from a TU, it will get compiled as any other module - with Sema - which will result in compilation errors. (See attached test case.) rdar://107663951 (cherry picked from commit b768a8c)
The CAS counterpart to the upstream llvm#86347. (cherry picked from commit 0d92d1c)
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@swift-ci please test |
akyrtzi
approved these changes
Mar 28, 2024
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Superseded by #8484 that automatically merges into |
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