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

[Jeff Law]

On 05/12/2018 10:02 AM, Richard Sandiford wrote:
> "A. Skrobov" <tyomitch@gmail.com> writes:
>>> 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.
> 
> I don't think we can assert even for cse, since AIUI these codes can
> still be used for stack pushes and pops.
No.  We're not supposed to have any auto-inc insns prior to the auto-inc
pass.  A stack push/pop early in the compiler would have to be
represented by a PARALLEL.

It's been this way forever.  It's documented in the internals manual
somewhere.

jeff