[Bug target/94052] New: Paradoxical subregs out of expand causes ICE with multi register modes

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94052

            Bug ID: 94052
           Summary: Paradoxical subregs out of expand causes ICE with
                    multi register modes
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: tnfchris at gcc dot gnu.org
          Reporter: tnfchris at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64-*

Created attachment 47979
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47979&action=edit
repro

Expand generates the following paradoxical subreg

(insn 446 354 445 2 (set (reg:CI 383)
 (subreg:CI (reg:V4SI 291) 0)) "small.i":146:22 3408 {*aarch64_movci}
 (nil))

but reload can't deal with this so it ICEs as it loops and reached the maximum
number of reloads while trying to break apart this subreg and do the reload.