[Bug rtl-optimization/67443] New: DSE removes required store instruction

[krebbel at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67443

            Bug ID: 67443
           Summary: DSE removes required store instruction
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: krebbel at gcc dot gnu.org
  Target Milestone: ---

Created attachment 36289
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36289&action=edit
Autoreduced testcase

This bug has been reported on the Debian mailing list. It occurs when building
the mozilla javascript engine with GCC 5 on S/390:

https://lists.debian.org/debian-s390/2015/08/msg00006.html

Bisecting shows that the failure occurred after this commit:

commit 90f3e775d6b7bec70e883579beb49b456c135a09
Author: wmi <wmi@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Thu Jan 22 17:59:23 2015 +0000

    2015-01-22  Wei Mi  <wmi@google.com>

            PR rtl-optimization/64557
            * dse.c (record_store): Call get_addr for mem_addr.
            (check_mem_read_rtx): Likewise.

Building the attached testcase with GCC before and after the commit shows that
a single stc (store character) instruction is missing after the patch.

Build options: -O2 -march=z900 -fPIC -std=gnu++11