[DependencyScanning] Allow sharing of explicit modules between a PCH and a TU that doesn't use PCH #6691
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This is particularly useful to avoid diverging the modules between a PCH and a translation-unit compilation. Differential Revision: https://reviews.llvm.org/D148369
For explicit modules workflow `NeededByPCHOrCompilationUsesPCH` is not a meaningful difference for creation of explicit modules and we canonicalize it away. Treat it as benign for the purposes of AST reading, when in the context of explicit modules workflow. Note this commit makes `test/ClangScanDeps/shared-module-for-tu-and-pch.c` pass, which is why it is not accompanied by its own test.
akyrtzi
commented
Apr 20, 2023
| bool ExistingNeededByPCHOrCompilationUsesPCH = | ||
| ExistingLangOpts.NeededByPCHOrCompilationUsesPCH; | ||
| if (IsExplicitModulesWorkflow) { | ||
| // Match NeededByPCHOrCompilationUsesPCH to make it "benign". |
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I don't particularly like this hack but I wanted to minimize the differences from upstream when dealing with NeededByPCHOrCompilationUsesPCH.
Author
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I had offline discussion with @jansvoboda11 and he had a suggestion for the build system to treat the prefix header as a module, which would avoid all these hacks that we have to deal with. |
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This cherry-picks https://reviews.llvm.org/D148369 along with adding a commit to deal with
NeededByPCHOrCompilationUsesPCH(that only exists in apple fork) so the upstream test can actually pass.