[PATCH] D120781: [IRLinker] materialize Functions before moving any

[Duncan P. N. Exon Smith via Phabricator via llvm-commits]

dexonsmith added a comment.

That case with `@x` reminded me of my concern about miscompiles due to `blockaddress` to a de-refinable function.

I was wondering if we could make those illegal in the verifier. In particular, reject a reference `blockaddress(@f, ...)` if:

- it's not a self-reference (it appears outside the body of `@f`) AND
- `@f` is de-refinable (linkage is `available_externally` or `{weak,linkonce}{,_odr}`) AND
- the reference is NOT in the same `comdat` as `@f`.

But I think we probably can't disallow it. Clang will generate IR that violates that for:

  void sink(...);
  inline void f1() {
    static void *Label = &&label;
    sink(Label);
  label:
    return;
  }
  void f2() { f1(); }

Maybe it'd be desirable to change Clang to put `Label` in the same `comdat` as `f1()`, but that won't solve object formats (like Mach-O) that don't have comdats.

For this case, the linker probably *in practice* probably selects them from the same object file.


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https://reviews.llvm.org/D120781