[Bug c++/82899] *this in constructors could not alias with reference input parameters of the same type

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82899

--- Comment #14 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #13)
> I have no idea what was changed in gcc-8 that
> helped the original testcase,

(optimization happens in FRE1)
It could be an optimization that says that either the objects don't alias and
we are writing _1, or they are the same object and we are writing _1, so just
write _1 without caring about aliasing. This was definitely discussed, but I
didn't remember that it had been committed (bug 80617 is still open).

Anyway, if you want to experiment, the function build_this_parm (in
gcc/cp/decl.c) seems like a good starting point.