dexonsmith added a comment. In D126676#3687491 <https://reviews.llvm.org/D126676#3687491>, @mstorsjo wrote:
> In D126676#3687227 <https://reviews.llvm.org/D126676#3687227>, @dexonsmith > wrote: > >> There are cases where it’s safe to have mismatched defines (e.g., if a >> define can be proven during a cheap dependency scan not to matter for a >> given PCH, it’s better to canonicalize away the define and share the >> artifact more broadly) but if I understand correctly this patch won’t >> preclude compiler smarts like that. > > Yup. Any implementation of such logic hasn’t materialized during the 10 years > since todos hinting that we should implement that, but it doesn’t seem to be > a big practical issue either, outside of false positive matches with gcc PCH > directories - so I guess it’s not a high priority in practice. Note, FWIW, that clang-scan-deps is being used to canonicalize command-lines as of the last year; e.g., there are patches up (maybe committed?) to remove unused search paths for implicitly-discovered explicit modules. Finding unused defines is a bit harder and less urgent (search path explosion had to be fixed for performance parity with on-demand implicit modules, which have an unsound optimization of ignoring search path differences), but there’s now a framework where it can be reasonably implemented if/when it’s identified as a major bottleneck in builds. (Fallout from unsoundness in on-demand implicit modules is a big reason progress has been slow in this area.) Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D126676/new/ https://reviews.llvm.org/D126676 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
