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Re: [RFC PATCH, i386]: Rewrite pop patterns to use POST_INC memory operands
On Mon, Aug 30, 2010 at 7:47 PM, Jakub Jelinek <jakub@redhat.com> wrote:
>> > I will wait for eventual comments due to scary %%% comment (this is
>> > also why the patch is in the RFC state ATM).
>>
>> I'm sure I'm not aware of all the dataflow changes in the past years,
>> so I have no real constructive feedback as to whether it should be
>> expected to work now.
>
> I must say I'm very surprised if the patch works reliably, there are many
> #ifdef AUTO_INC_DEC guarded hunks and not all of them are related only
> to automatic inc/dec additions, but just whether the code should look for
> PRE/POST_INC/DEC/MODIFY in the IL. ?E.g. cleanup_auto_inc_dec
> in the combiner.c to give some example.
> And, cselib does very poor job with inc/dec addressing currently (except for
> var-tracking which removes inc/dec addressing from the IL before feeding it
> into cselib).
i386 was already AUTO_INC_DEC target due to pre_decrement push insn,
The patch just balances the machine description by re-defining pop in
terms of post_increment.
Uros.