[clang][deps] Skip slow UNHASHED_CONTROL_BLOCK records (#69975)
#7746
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Deserialization of the `DIAGNOSTIC_OPTIONS` and `HEADER_SEARCH_PATHS` records is slow and done for every transitively loaded PCM. Deserialization of these records cannot be skipped, because the words are VBR6-encoded and we don't store the length of the entire record. We could either turn them into binary blobs that can be skipped during deserialization, or skip writing them altogether. This patch takes the latter approach, since these records are not necessary in scanning PCMs. The scanner doesn't make any guarantees about the accuracy of diagnostics, and we always have the same header search paths due to strict context hashing. The commit that makes the `DIAGNOSTIC_OPTIONS` record skippable was originally implemented by @benlangmuir in a downstream repo. (cherry picked from commit 6c465a2)
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@swift-ci please test |
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Deserialization of the
DIAGNOSTIC_OPTIONSandHEADER_SEARCH_PATHSrecords is slow and done for every transitively loaded PCM. Deserialization of these records cannot be skipped, because the words are VBR6-encoded and we don't store the length of the entire record. We could either turn them into binary blobs that can be skipped during deserialization, or skip writing them altogether. This patch takes the latter approach, since these records are not necessary in scanning PCMs. The scanner doesn't make any guarantees about the accuracy of diagnostics, and we always have the same header search paths due to strict context hashing.The commit that makes the
DIAGNOSTIC_OPTIONSrecord skippable was originally implemented by @benlangmuir in a downstream repo.(cherry picked from commit 6c465a2)