Possible bug in cse.c affecting pre/post-modify mem access

[A. Skrobov]

On Fri, May 11, 2018 at 12:09 AM, Jeff Law <law@redhat.com> wrote:
>
> My recollection is that auto-increment addressing modes should not
> appear in the RTL in the CSE pass.

Fair enough; but they're explicitly listed in the big switch block in
hash_rtx_cb ().
Should my added line change from "invalidate_dest (XEXP (x, 0));" to
"gcc_unreachable ();" ?
Such a patch wouldn't need a testcase, I suppose.