RE: [PATCH][GCC][SLP][testsuite] Turn off vect-epilogue-nomask for slp-rect-3

[Tamar Christina <Tamar.Christina@arm.com>]

Hi Richi,

> >
> > This patch turns off vect-epilogue-nomask for slp-reduc-3 as it seems
> > that the epiloque in this loop is vectorizable using SLP and smaller
> > VF.  Since this test expects there to be no SLP vectorization at all
> > the testcase then fails for arm targets.
> 
> Actually we do expect SLP vectorization, just the counting might go wrong.
> 
> What's the actual FAIL for arm?

I should have worded this better considering the testcase literally contains SLP in the name...

The failure is for the XFAIL 

/* { dg-final { scan-tree-dump-times "vectorizing stmts using SLP" 1 "vect" { xfail { vect_widen_sum_hi_to_si_pattern || { ! vect_unpack } } } } } */

And my understanding as to what is happening is that without epiloque no mask it would only try HI modes, but thanks to the epiloques nomask
It tries QI mode as well which succeeds.  The xfail then generates an xpass since the condition on it checks for HI to SI and not QI.

So I disabled the epiloque mask since it seems to violate the conditions the test actually wanted to test for.

Not quite sure why it's failing only on Arm though.

Regards,
Tamar

> 
> Disabling epilogue vect is of course OK if it simplifies things.
> 
> > Regtested on arm-none-eabi and no issues.
> >
> > Ok for trunk?
> 
> > Thanks,
> > Tamar
> >
> > gcc/testsuite/ChangeLog:
> >
> > 2019-11-28  Tamar Christina  <tamar.christina@arm.com>
> >
> > 	* gcc.dg/vect/slp-reduc-3.c: Turn off epilogue-nomask.
> >
> >
> 
> --
> Richard Biener <rguenther@suse.de>
> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409
> Nuernberg, Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)