Re: Plumbers CF MCs

[Peter Zijlstra <peterz@infradead.org>]

On Mon, Mar 22, 2021 at 01:23:03PM -0700, Nick Desaulniers wrote:
> Hi all,
> I saw plumbers opened call for microconferences:
> https://www.linuxplumbersconf.org/blog/2021/index.php/2021/03/18/cfp-open-microconferences/
> 
> I was going to put together a submission; do we want to do a combined
> toolchain MC, or have distinct ones this year?
> 
> I know in 2020 the GNU cauldron was co-located with Plumbers, as well
> as a GNU Tools Track MC and LLVM MC.

A combined MC focussed on kernel issues seems very interesting. We still
have the control dependency (volatile-if?) thing pending. We had a bit
of a discussion on that after last year, but I don't think anything
really came of that, can we pick that up? Ideally a compiler person does
an actual proposal for this year.

If we can sort that, there's the rest of the dependencies Will outlined
:-)

Then there seemed to be people that thought __always_inline was a
suggestion... I think we need to explore how that was ever possible.

There's the endless UB debate... can we define more to reduce the UB? I
mean, we're already bound by architecture ABI on the one hand, and
actual use on the other. It would be so very nice to be able to get more
-fwrapv and -fno-strict-aliasing knobs that define UBs away.

There also is talk about straight line speculation mitigations. for x86
we should probably emit an INT3 after every JMP and RET. Although this
might not be controversial and be sorted by the time Plumbers happens.

There was some talk about how compilers could help objtool make sense of
jump tables.

GCC's status on asm-goto with outputs?

Clang's getting asm-constraints wrong ("rm" and it always picks "m").


And I'm sure there was more..