Closed Quuxplusone closed 4 years ago
Bugzilla Link | PR43981 |
Status | RESOLVED FIXED |
Importance | P enhancement |
Reported by | John Regehr (regehr@cs.utah.edu) |
Reported on | 2019-11-12 08:40:38 -0800 |
Last modified on | 2019-12-17 16:32:14 -0800 |
Version | trunk |
Hardware | PC Linux |
CC | aemerson@apple.com, daniel_l_sanders@apple.com, htmldeveloper@gmail.com, jpaquette@apple.com, llvm-bugs@lists.llvm.org, nunoplopes@sapo.pt, quentin.colombet@gmail.com, xiaoqing_wu@apple.com |
Fixed by commit(s) | |
Attachments | |
Blocks | |
Blocked by | |
See also |
+Amara and Jessica since they work on the AArch64 backend
We have known missing support for some constructs in GlobalISel, so these cases in normal compilation should be falling back to SDAG. For most bugs like these I don't think it's worth reporting unless there's a crash even with fallbacks enabled, or there's some miscompilation happening.
Great, thanks -- I hadn't known about the fallback.
Are we talking about -global-isel-abort? If so, what numeric value for this option would you recommend?
It depends on if you want diagnostics when you fall back or not.
-global-isel-abort=0 => Fall back to SelectionDAG when you can't select
something
-global-isel-abort=2 => Same thing, but also emit a diagnostic when you fall
back
I usually use -global-isel-abort=2 during development.
Awesome, I'll only report bugs which make it through this.
(I'll let one of y'all close this but I have no reason for it to be open if it's not helpful.)
(In reply to John Regehr from comment #6)
> (I'll let one of y'all close this but I have no reason for it to be open if
> it's not helpful.)
Thanks John for filing this!
In general, I would rather that we keep them open until we fix the fallback.
Knowing that we still fall back in some places is a valuable source of
information IMHO.
Bottom line, please keep filing PRs for the cases where you see GISel falls
back (i.e., using the -global-isel-abort=2 that Jessica mentioned.)
Posted a fix for review: https://reviews.llvm.org/D71587
Fixed in a17619e0b097 (https://reviews.llvm.org/rGa17619e0b097)