[PATCH] D76140: [InlineFunction] update nonnnull attribute during inlining

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert requested changes to this revision.
jdoerfert added a comment.

In addition to @reames correctness concerns this is not valid for a different reason. You cannot backwards propagate information in the general case:

  __attribute__((nonnull)) int *foo(int c) {
     int *A = unknown();
     int *B = unknown();
     do_sth_with_ptr_and_may_use_nonnull(A, B);
     return c ? A : B; // or if (C) return A; else return B;
  }

Knowing `foo` returns a `nonnull` value cannot be used to annotate `A` or `B`.

I think this is generally problematic as it basically special cases a situation which we can handle in general just fine.
Let's assume we inline and keep the `nonnull` on the return values around, we run `nonnull` deduction on the caller and we get the `nonnull` where it is correct.
The benefit of doing it this way (D75825 <https://reviews.llvm.org/D75825>) is that it will also work with all other attributes as well without reinventing all the logic in the Attributor.


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76140/new/

https://reviews.llvm.org/D76140