https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62077
--- Comment #67 from Sven C. Dack <sven.c.dack at virginmedia dot com> ---
(In reply to Richard Biener from comment #66)
> The issue re-appears with GCC 6, the workaround doing
> --enable-stage1-checking=release still works.
>
> Note that the comparison we do with LTO bootstrap is quite pointless as we
> only compile the internal IL at LTO streaming time but not the final result
> of optimization. For that we'd need to compare cc1, cc1plus, etc. itself.
To call it pointless is as dismissive of the effort as saying you'd be willing
to accept any indeterministic behaviour, including magic, into computer science
as long as it produces great software. Let's not be this lazy.
I believe there is still much to be had from a comparison in between the stages
and of all that can be determined. This particular case here may not have
revealed a serious issue. However, it makes it only a fortunate case, but it's
not a reason to welcome indetermination and luck into GCC's development or to
dismiss a good concept. I'd rather fear that in doing so you'd lose further
support from the scientific community.
Anyhow, this is my opinion. I should in fact not be getting any e-mails on this
report - I have excluded myself from the list some time ago - and yet did I did
get the mail.
> So a fix would be to make the comparison configurable to a tri-stage
> { object-files, binaries, off } where a boostrap with comparison off
> can also omit building stage3 but still get the benefit of building
> GCC with itself and not the host compiler.
>
> Comparing the binaries is generally slower of course.
