RISC-V LLVM sync-up call 19th Sep 2019

For background on these calls, see

Reminder: the purpose is to co-ordinate between active contributors.
If you have support questions etc then it's best to post to llvm-dev.

We have a call each Thursday at 4pm BST, via
<https://meet.google.com/ske-zcog-spp>. I appreciate if you haven't joined
previously that's no notice - but we look forward to talking next week
or beyond!

Issues to discuss today include:
* Machine scheduler
  * Trivial patch to enable has now landed (rL372106), interested in
seeing an in-tree scheduling model (Michael has been working on this)
* GCC torture suite support in the LLVM test suite
  * Sam has been working on updating this - thanks to Kristof for
review feedback
* RA as reserved va callee-saved: <https://reviews.llvm.org/D67698>
  * Thoughts? My recollection is that different backends made
different choices here. I could imagine that RA always holding RA may
be useful for some use cases that don't want to parse DWARF
* Other things to discuss, if interest/time:
  * Machine outliner https://reviews.llvm.org/D66210
  * LTO https://reviews.llvm.org/D67409
  * pcrel_lo evaluation https://reviews.llvm.org/D60657
* Anything else (as usual, always helpful to drop me an email ahead of
time to add to the agenda - but feel free to list things here)

I should be dialed in but traveling, so Sam will lead today's call.