RISC-V LLVM sync-up call 16th Jan 2020

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

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:
* LLVM 10.0 has branched!
  * Shrink wrapping landed, though msave-restore didn't. See below for LTO.
* LTO: Sam+(hopefully) Zakk will talk through the current thinking,
what we want to land for
10.0, what the plan is going forwards. See
<https://reviews.llvm.org/D72755> Adds the target-abi module flag
and <https://reviews.llvm.org/D72768> Ensures the target-abi module
flag is accurate.
* Scheduler patch status <https://reviews.llvm.org/D68685>
* Sign/zero-extension of asm operands came up again. In supporting a
customer we tracked down the difference between gcc and clang
behaviour causing an issue with Musl. Luis proposed a patch to
upstream musl <https://www.openwall.com/lists/musl/2020/01/15/2>
* [RFC] Upsream development of support for yet-to-be-ratified RISC-V
extensions <https://docs.google.com/document/d/1YtbEfPip_mCOiqWARCB2dBWaY8W6Gyu8KmJISohZloc/edit>.
I hope we can dedicate time to talking through this. If people aren't
strongly opposed, I'd hope to post to llvm-dev soon after the meeting
and we can continue discussion there.