[Bug rtl-optimization/71724] [5/6/7 Regression] ICE: Segmentation fault, deep recursion between combine_simplify_rtx and subst

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71724

Alan Modra <amodra at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2016-08-09
                 CC|                            |amodra at gmail dot com
     Ever confirmed|0                           |1

--- Comment #1 from Alan Modra <amodra at gmail dot com> ---
combine goes into infinite recursion inside this call:
 newpat = subst (newpat, i0dest, i0src, 0, 0, 0);

The args of the failing subst are:
x:
(parallel [
        (set (reg:SI 181)
            (plus:SI (ltu:SI (plus:SI (reg:SI 165)
                        (reg:SI 174 [ t9.0_1+4 ]))
                    (reg:SI 165))
                (reg:SI 173 [ t9.0_1 ])))
        (clobber (reg:SI 76 ca))
    ])
from:
(reg:SI 174 [ t9.0_1+4 ])
to:
(if_then_else:SI (eq (reg:CC 185)
        (const_int 0 [0]))
    (reg:SI 165)
    (reg:SI 174 [ t9.0_1+4 ]))