RISC-V LLVM sync-up call 16 Apr 2020

For background on these calls, see
<http://lists.llvm.org/pipermail/llvm-dev/2019-September/135087.html>.

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've created a shared calendar which may help in keeping track, which
is 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:
* LTO/ThinLTO for RISC-V https://reviews.llvm.org/D78035
* Initial bitmanip patches landed last week (thank you all!). Next steps
* Differential testing work from Luis on GCC vs Clang missed
optimisation opportunities
* FYI/reminders
  * DAGCombiner improvement from Roger for bool comparisons looks
almost good to land https://reviews.llvm.org/D65802
  * Evandro is still seeking compact code model feedback
https://github.com/riscv/riscv-elf-psabi-doc/issues/140
  * vscale discussion on llvm-dev continues
http://lists.llvm.org/pipermail/llvm-dev/2020-April/140693.html
  * FDPIC discussions on RISC-V sw-dev are still continuing
https://groups.google.com/a/groups.riscv.org/d/msg/sw-dev/ZjYUJswknQ4/WYRRylTwAAAJ
* No other topics were submitted, as always, please do submit things
you'd like to discuss

Best,

Alex