rjmccall wrote: > Oh, sorry for not providing context earlier. The reasoning behind is to allow > certain optimizations involving errno-writing libcalls (marked as > `memory(errnomem: write)`) to occur, if we are able to prove the involved > memory location does not alias errno (e.g., because we are accessing a > float-typed pointer). IIUC, in standard C, errno is an int, so all legitimate > accesses must use int-compatible types (or otherwise violating strict > aliasing). Hence, we should be able to leverage TBAA and prove not aliasing > with errno, if we do not alias for any nodes belonging to `!llvm.errno.tbaa` > (which is presumably gathering all int-based nodes; this should require > confirmation).
I see. So the idea here is *not* that we're changing the TBAA nodes used for any actual accesses. Instead, we're using a named global metadata to specify the TBAA node that all `errno` accesses would use so that LLVM can do alias analysis around these libcalls (presumably to allow load/store optimization across them). That makes a lot of sense, thanks for the clarification. Please update your commit messages and PR title and description; I think if you re-read them, you're see that they sound as if you're trying to change how accesses to `errno` are annotated. In the meantime, I think I have the context to review the PR now. https://github.com/llvm/llvm-project/pull/125258 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
