testsuite: Fix up pr96573.c on aarch64 [PR96573]

testsuite: Fix up pr96573.c on aarch64 [PR96573]

On Thu, Apr 01, 2021 at 02:16:55PM +0100, Alex Coplan via Gcc-patches wrote:
> FYI, I'm seeing the new test failing on aarch64:
>
> PASS: gcc.dg/pr96573.c (test for excess errors)
> FAIL: gcc.dg/pr96573.c scan-tree-dump optimized "__builtin_bswap"

The vectorizer in the aarch64 case manages to emit a VEC_PERM_EXPR instead
(which is just as efficient).

So, do we want to go for the following (and/or perhaps also restrict the test to
a couple of targets where it works?  In my last distro build it failed only
on aarch64-linux, while armv7hl-linux-gnueabi and
{i686,x86_64,powerpc64le,s390x}-linux were fine)?

2021-04-06  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/96573
	* gcc.dg/pr96573.c: Instead of __builtin_bswap accept also
	VEC_PERM_EXPR with bswapping permutation.