Re: [Patch, testsuite] fix failure in test gcc.dg/vect/slp-perm-8.c

[Richard Guenther <richard dot guenther at gmail dot com>]

On Wed, Apr 25, 2012 at 4:27 PM, Greta Yorsh <Greta.Yorsh@arm.com> wrote:
> Richard Guenther wrote:
>> On Wed, Apr 25, 2012 at 3:34 PM, Greta Yorsh <Greta.Yorsh@arm.com>
>> wrote:
>> > Richard Guenther wrote:
>> >> On Wed, Apr 25, 2012 at 1:51 PM, Greta Yorsh <Greta.Yorsh@arm.com>
>> >> wrote:
>> >> > The test gcc.dg/vect/slp-perm-8.c fails on arm-none-eabi with neon
>> >> enabled:
>> >> > FAIL: gcc.dg/vect/slp-perm-8.c scan-tree-dump-times vect
>> "vectorized
>> >> 1
>> >> > loops" 2
>> >> >
>> >> > The test expects 2 loops to be vectorized, while gcc successfully
>> >> vectorizes
>> >> > 3 loops in this test using neon on arm. This patch adjusts the
>> >> expected
>> >> > output. Fixed test passes on qemu for arm and powerpc.
>> >> >
>> >> > OK for trunk?
>> >>
>> >> I think the proper fix is to instead of
>> >>
>> >> ? for (i = 0; i < N; i++)
>> >> ? ? {
>> >> ? ? ? input[i] = i;
>> >> ? ? ? output[i] = 0;
>> >> ? ? ? if (input[i] > 256)
>> >> ? ? ? ? abort ();
>> >> ? ? }
>> >>
>> >> use
>> >>
>> >> ? for (i = 0; i < N; i++)
>> >> ? ? {
>> >> ? ? ? input[i] = i;
>> >> ? ? ? output[i] = 0;
>> >> ? ? ? __asm__ volatile ("");
>> >> ? ? }
>> >>
>> >> to prevent vectorization of initialization loops.
>> >
>> > Actually, it looks like both arm and powerpc vectorize this
>> initialization loop (line 31), because the control flow is hoisted
>> outside the loop by previous optimizations. In addition, arm with neon
>> vectorizes the second loop (line 39), but powerpc does not:
>> >
>> > 39: not vectorized: relevant stmt not supported: D.2163_8 = i_40 * 9;
>> >
>> > If this is the expected behaviour for powerpc, then the patch I
>> proposed is still needed to fix the test failure on arm. Also, there
>> would be no need to disable vectorization of the initialization loop,
>> right?
>>
>> Ah, I thought that was what changed. ?Btw, the if () abort () tries to
>> disable
>> vectorization but does not succeed in doing so.
>>
>> Richard.
>
> Here is an updated patch. It prevents vectorization of the initialization
> loop, as Richard suggested, and updates the expected number of vectorized
> loops accordingly. This patch assumes that the second loop in main (line 39)
> should only be vectorized on arm with neon. ?The test passes for arm and
> powerpc.
>
> OK for trunk?

If arm cannot handle 9 * i then the approrpiate condition would be
vect_int_mult, not arm_neon_ok.

Ok with that change.

Richard.

> Thank you,
> Greta
>
> gcc/testsuite/ChangeLog
>
> 2012-04-25 ?Greta Yorsh ?<Greta.Yorsh@arm.com>
>
> ? ? ? ?* gcc.dg/vect/slp-perm-8.c (main): Prevent
> ? ? ? ?vectorization of initialization loop.
> ? ? ? ?(dg-final): Adjust the expected number of
> ? ? ? ?vectorized loops.
>
>
>
>