[Bug c++/78689] [7 Regression] ICE (segfault) within cleanup_dead_labels

["jason at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78689

--- Comment #6 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #4)
> _ZN1XCI21WEi emitted in _ZN1XCI21WEi comdat, without _ZN1XCI11WEi alias,
> which has the argument only in GCC (bug?), e.g. as seen with -O0 saves 3
> arguments to stack instead of 2:
>         movq    %rdi, -8(%rbp)
>         movq    %rsi, -16(%rbp)
>         movl    %edx, -20(%rbp)
> but callers actually provide 2:
>   X::X (_2, _3);

Oops, not sure how that broke.  That's why reverting the tree-inline hunk
doesn't break anything.  I'll fix this issue.

And indeed there won't be any user labels in the branch we want to omit here. 
But perhaps we can do better in the front end.