Re: [PATCH][0/n] Merge from match-and-simplify

[Andrew Pinski <pinskia@gmail.com>]

On Thu, Oct 16, 2014 at 1:38 PM, Sebastian Pop <sebpop@gmail.com> wrote:
> Richard Biener wrote:
>>
>> I have posted 5 patches as part of a larger series to merge
>> (parts) from the match-and-simplify branch.  While I think
>> there was overall consensus that the idea behind the project
>> is sound there are technical questions left for how the
>> thing should look in the end.  I've raised them in 3/n
>> which is the only patch of the series that contains any
>> patterns sofar.
>>
>> To re-iterate here (as I expect most people will only look
>> at [0/n] patches ;)), the question is whether we are fine
>> with making fold-const (thus fold_{unary,binary,ternary})
>> not handle some cases it handles currently.
>
> I have tested on aarch64 all the code in the match-and-simplify against trunk as
> of the last merge at r216315:
>
> 2014-10-16  Richard Biener  <rguenther@suse.de>
>
>         Merge from trunk r216235 through r216315.
>
> Overall, I see a lot of perf regressions (about 2/3 of the tests) than
> improvements (1/3 of the tests).  I will try to reduce tests.
>
> For instance, saxpy regresses at -O3 on aarch64:
>
> void saxpy(double* x, double* y, double* z) {
>     int i=0;
>     for (i = 0 ; i < ARRAY_SIZE; i++) {
>         z[i] = x[i] + scalar*y[i];
>     }
> }

This looks like a scheduling issue rather than anything else.  The
scheduler for a57 is not complete and does not model some things like
the fusion of the compares and branch which is most likely what you
are seeing.

Thanks,
Andrew Pinski

>
> $ diff -u base.s mas.s
> --- base.s      2014-10-16 15:30:15.351430000 -0500
> +++ mas.s       2014-10-16 15:30:16.183035000 -0500
> @@ -2,12 +2,14 @@
>         add     x1, x2, 800
>         ldr     q0, [x0, x2]
>         add     x3, x2, 1600
> +       cmp     x0, 784
>         ldr     q1, [x0, x1]
> +       add     x1, x0, 16
>         fmla    v0.2d, v1.2d, v2.2d
>         str     q0, [x0, x3]
> -       add     x0, x0, 16
> -       cmp     x0, 800
> +       mov     x0, x1
>         bne     .L140
>  .LBE179:
> -       subs    w4, w4, #1
> +       cmp     w4, 1
> +       sub     w4, w4, #1
>         bne     .L139
>
>
>
> Thanks,
> Sebastian