RISC-V LLVM sync-up call 7th Nov 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 GMT, via
<https://meet.google.com/ske-zcog-spp>. Both Europe and US have ended
daylight savings now, so the time should be stable for everyone.

I've created a shared calendar which may help in keeping track, which
is hopefully accessible at:
  * <https://calendar.google.com/calendar/b/1?cid=bG93cmlzYy5vcmdfMG41cGtlc2ZqY25wMGJoNWhwczFwMGJkODBAZ3JvdXAuY2FsZW5kYXIuZ29vZ2xlLmNvbQ>
  * <https://calendar.google.com/calendar/ical/lowrisc.org_0n5pkesfjcnp0bh5hps1p0bd80%40group.calendar.google.com/public/basic.ics>

Issues to discuss today include the following:
* Luís has posted D69723 for review, this removes CFI information from
function epilogs (which should help correctness)
* Luís is working on the FCOPYSIGN patch (D66725), expect updates
* D00657 which fixes evaluation of pcrel_lo is reviewed and ready to
land. We've had feedback that this is sufficient to allow LLD to link
a RISC-V FreeBSD userspace (with -mno-relax). As this area has been a
source of bugs before, more eyes are always useful.
* Sam is looking for another comment from anyone on new default
march/mabi patch: D69383 It will be merged this
week if no more comments are provided
* Other Updated Patches this week:
  * D66210 (Machine Outliner)
  * D62686 (Save/Restore via Libcalls)
  * D62190 (Shrink Wrapping)
* New Patches:
  * https://reviews.llvm.org/D69899 (better errors in MC layer)
  * https://reviews.llvm.org/D69894 (MC layer mnemonic spell checking)
  * https://reviews.llvm.org/D69808 (GlobalISel return lowering)