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

[A. Skrobov]

> If we look in sel-sched-ir.c we see that it calls into hash_rtx_cb
> (sigh, bad modularity).   I'm not at all familiar with how the hashing
> is used within the selective scheduler, so I can't really say what the
> selective scheduler *should* be doing here.

OK, I see. Now what do you think would be the best course of action?
Leave everything as it is? The selective scheduler may or may not want
these memory accesses ignored.