[Bug rtl-optimization/68536] LRA ICEs with new arm pattern

[ktkachov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68536

--- Comment #2 from ktkachov at gcc dot gnu.org ---
Sorry, I was doing this on top of the patch posted at
https://gcc.gnu.org/ml/gcc-patches/2015-11/msg00686.html

The subreg_highpart_operator predicate is defined as:
(define_special_predicate "subreg_highpart_operator"
  (and (match_code "subreg")
        (match_test "GET_MODE_SIZE (mode)
                       < GET_MODE_SIZE (GET_MODE (SUBREG_REG (op)))
                     && SUBREG_BYTE (op)
                        == subreg_highpart_offset (mode,
                                        GET_MODE (SUBREG_REG (op)))")))