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specify what a CGU is (#2163)

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Connor Tsui 2024-12-16 02:12:01 -05:00 committed by GitHub
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src/queries/incremental-compilation-in-detail.md
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@ -377,15 +377,14 @@ the result cache doesn't unnecessarily shrink again.
# Incremental Compilation and the Compiler Backend # Incremental Compilation and the Compiler Backend
The compiler backend, the part involving LLVM, is using the query system but The compiler backend, the part involving LLVM, is using the query system but
it is not implemented in terms of queries itself. As a consequence it is not implemented in terms of queries itself. As a consequence it does not
it does not automatically partake in dependency tracking. However, the manual automatically partake in dependency tracking. However, the manual integration
integration with the tracking system is pretty straight-forward. The compiler with the tracking system is pretty straight-forward. The compiler simply tracks
simply tracks what queries get invoked when generating the initial LLVM version what queries get invoked when generating the initial LLVM version of each
of each codegen unit, which results in a dep-node for each of them. In codegen unit (CGU), which results in a dep-node for each CGU. In subsequent
subsequent compilation sessions it then tries to mark the dep-node for a CGU as compilation sessions it then tries to mark the dep-node for a CGU as green. If
green. If it succeeds it knows that the corresponding object and bitcode files it succeeds, it knows that the corresponding object and bitcode files on disk
on disk are still valid. If it doesn't succeed, the entire codegen unit has to are still valid. If it doesn't succeed, the entire CGU has to be recompiled.
be recompiled.
This is the same approach that is used for regular queries. The main differences This is the same approach that is used for regular queries. The main differences
are: are: