https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92065
--- Comment #20 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> It's my impression that the code compiles also with -O2
> or -O3, which might be an interim solution until this
> bug is fixed.
I only get a different ICE:
19 | subroutine fun1(this, a)
| ^
internal compiler error: in set_parm_rtl, at cfgexpand.c:1401
