Re: [PATCH GCC][1/2]Feed bound computation to folder in loop split

["Bin.Cheng" <amker.cheng@gmail.com>]

On Fri, Jun 16, 2017 at 11:49 AM, Richard Biener
<richard.guenther@gmail.com> wrote:
> On Wed, Jun 14, 2017 at 3:07 PM, Bin Cheng <Bin.Cheng@arm.com> wrote:
>> Hi,
>> Loop split forces intermediate computation to gimple operands all the time when
>> computing bound information.  This is not good since folding opportunities are
>> missed.  This patch fixes the issue by feeding all computation to folder and only
>> forcing to gimple operand at last.
>>
>> Bootstrap and test on x86_64 and AArch64.  Is it OK?
>
> Hm?  It uses gimple_build () which should do the same as fold_buildN in terms
> of simplification.
>
> So where does that not work?  It is supposed to be the prefered way and no
> new code should use force_gimple_operand (unless dealing with generic
> coming from other middle-end infrastructure like SCEV or niter analysis)
Hmm, current code calls force_gimpele operand several times which
causes the inefficiency.  The patch avoids that and does one call at
the end.

Thanks,
bin
>
> Richard.
>
>>
>> Thanks,
>> bin
>> 2017-06-12  Bin Cheng  <bin.cheng@arm.com>
>>
>>         * tree-ssa-loop-split.c (compute_new_first_bound): Feed bound
>>         computation to folder, rather than force to gimple operands too
>>         early.