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Re: [x86,PATCH] Simple fix for Atom LEA splitting.


On Mon, Sep 16, 2013 at 2:50 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
> Hi All,
>
> Here is 1-line fix which improves Atom performance by better distance
> estimation. We got ~20% speedup on one of bench from eembc2.0 with
> this fix.
>
> Bootstrapping and regression testing were successful for x86-64.
>
> Is it OK for trunk?
>
> ChangeLog:
>
> 2013-09-16  Yuri Rumyantsev  <ysrumyan@gmail.com>
>
> * config/i386/i386.c (distance_agu_use_in_bb) : Proper initialization
> of 'prev' var to get better distance estimation.

Please rewrite this part to:

  basic_block bb = NULL;
  rtx next = start;
  rtx prev = NULL;

  if (start != NULL_RTX)
    {
      bb = BLOCK_FOR_INSN (start);
      if (start != BB_HEAD (bb))
    prev = insn;
    }

A comment would be also nice here. It took me quite some time to
decipher the code.

OK with these changes.

Thanks,
Uros.


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