[Bug debug/52132] New: [4.7 Regression] ICE in loc_descriptor

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52132

             Bug #: 52132
           Summary: [4.7 Regression] ICE in loc_descriptor
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: jakub@gcc.gnu.org
        ReportedBy: jakub@gcc.gnu.org
            Target: i686-linux


The following testcase ICEs with -m32 -g -O2 -std=c99 on x86_64-linux.
The bug is likely in regstack, which changes:
rh787518.i.216r.sched2:(debug_insn 20 58 21 2 (var_location:SI D#1 (subreg:SI
(reg:SF 8 st [orig:66 D.1248 ] [66]) 0)) rh787518.i:10 -1
to:
rh787518.i.218r.stack:(debug_insn 20 58 21 2 (var_location:SI D#1 (reg:SF 8
st)) rh787518.i:10 -1
(note the lost subreg).

The regression started with
http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=178597 though that likely just
made a latent bug into a reprduceable one.