[Bug rtl-optimization/78751] [7 Regression] ICE in extract_insn, at recog.c:2311 (error: unrecognizable insn) w/ -Os -misel

[aldyh at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78751

Aldy Hernandez <aldyh at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2016-12-09
                 CC|                            |aldyh at gcc dot gnu.org,
                   |                            |meissner at gcc dot gnu.org,
                   |                            |segher at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
Confirmed.  Started with the patch below, though it is unlikely to be the
problem, as this is a back end problem.  It is most likely associated with a
handful of rs6000 changes by Meissner or Segher around the same time.

commit 0d56015c6a1200605edf7bb30bea06f0b436a183
Author: law <law@138bc75d-0d04-0410-961f-82ee72b054a4>                      
Date:   Fri Nov 11 16:00:47 2016 +0000

        * gimple-ssa-isolate-paths.c (is_divmod_with_given_divisor): New
        function.
        (stmt_uses_name_in_undefined_way): New function, extracted from
        find_implicit_erroneous_behavior and extended for div/mod case.
        (stmt_uses_0_or_null_in_undefined_way): New function, extracted from
        find_explicit_erroneous_behavior and extended for div/mod case.
        (find_implicit_erroneous_behavior): Use new helper function.
        (find_explicit_erroneous_behavior): Use new helper function.

        * gcc.dg/tree-ssa/isolate-6.c: New test.                               
     * gcc.dg/tree-ssa/isolate-7.c: New test.

    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@242075
138bc75d-0d04-0410-961f-82ee72b054a4