[Bug rtl-optimization/85180] New: Infinite (?) loop in RTL DSE optimizer

[uweigand at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85180

            Bug ID: 85180
           Summary: Infinite (?) loop in RTL DSE optimizer
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: uweigand at gcc dot gnu.org
                CC: krebbel at gcc dot gnu.org
  Target Milestone: ---
            Target: s390x-ibm-linux

Created attachment 43828
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43828&action=edit
Test case - run with "cc1plus -O"

When attempting to compile the attached testcase simply with "cc1plus -O" on a
s390x-ibm-linux target, the compilation process never terminates.  The problem
appear to originate in the dse.c pass; building with -fno-dse makes the problem
go away.

I'm not completely sure that this is really an infinite loop, strictly
speaking, or just some exponential time behavior somewhere.  In any case, at
the time the compiler hangs, it sits in a long chain of find_base_term calls
ultimately originating at the canon_output_dependence in dse.c:1593
(record_store).