PR 71439 - Only vectorize live PHIs that are inductions

For a PHI to be used outside the loop it needs to be vectorized. However
the
vectorizer currently will only vectorize PHIs that are an induction.

This patch fixes PR 71439 by only allowing a live PHI to be vectorized if
it
is an induction. In addition, live PHIs need to pass a
vectorizable_live_operation check.

Tested on x86 and aarch64.
Ok to commit?

Alan.

gcc/
	PR tree-optimization/71439
	* tree-vect-loop.c (vect_analyze_loop_operations): Additional check for
	live PHIs.

testsuite/
	PR tree-optimization/71439
	* gcc.dg/vect/pr71439.c: New



               /* A scalar-dependence cycle that we don't support.  */
@@ -1686,6 +1687,9 @@ vect_analyze_loop_operations (loop_vec_info
loop_vinfo)
                 ok = vectorizable_induction (phi, NULL, NULL);
             }

+	  if (ok && STMT_VINFO_LIVE_P (stmt_info))
+	    ok = vectorizable_live_operation (phi, NULL, NULL, -1, NULL);
+
           if (!ok)
             {
               if (dump_enabled_p ())

On Wed, Jun 15, 2016 at 10:49 AM, Alan Hayward <alan.hayward@arm.com> wrote:
> For a PHI to be used outside the loop it needs to be vectorized. However
> the
> vectorizer currently will only vectorize PHIs that are an induction.
>
> This patch fixes PR 71439 by only allowing a live PHI to be vectorized if
> it
> is an induction. In addition, live PHIs need to pass a
> vectorizable_live_operation check.
>
> Tested on x86 and aarch64.
> Ok to commit?

Ok.

Thanks,
Richard.

> Alan.
>
> gcc/
>         PR tree-optimization/71439
>         * tree-vect-loop.c (vect_analyze_loop_operations): Additional check for
>         live PHIs.
>
> testsuite/
>         PR tree-optimization/71439
>         * gcc.dg/vect/pr71439.c: New
>
>
>
> diff --git a/gcc/testsuite/gcc.dg/vect/pr71439.c
> b/gcc/testsuite/gcc.dg/vect/pr71439.c
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..95e4763bad6e9f301d53c20ffa160b96b
> dad9a53
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr71439.c
> @@ -0,0 +1,17 @@
> +#include "tree-vect.h"
> +
> +int a, b, c;
> +short fn1(int p1, int p2) { return p1 + p2; }
> +
> +int main() {
> +  a = 0;
> +  for (; a < 30; a = fn1(a, 4)) {
> +    c = b;
> +    b = 6;
> +  }
> +
> +  if (c != 6)
> +    abort ();
> +
> +  return 0;
> +}
> diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
> index
> 1231b95f6a71337833e8c4b24884da9f96a7b5bf..90ade75bcd212b542ad680877a79df717
> 751ff4b 100644
> --- a/gcc/tree-vect-loop.c
> +++ b/gcc/tree-vect-loop.c
> @@ -1669,7 +1669,8 @@ vect_analyze_loop_operations (loop_vec_info
> loop_vinfo)
>
>            gcc_assert (stmt_info);
>
> -          if (STMT_VINFO_RELEVANT (stmt_info) == vect_used_in_scope
> +          if ((STMT_VINFO_RELEVANT (stmt_info) == vect_used_in_scope
> +               || STMT_VINFO_LIVE_P (stmt_info))
>                && STMT_VINFO_DEF_TYPE (stmt_info) != vect_induction_def)
>              {
>                /* A scalar-dependence cycle that we don't support.  */
> @@ -1686,6 +1687,9 @@ vect_analyze_loop_operations (loop_vec_info
> loop_vinfo)
>                  ok = vectorizable_induction (phi, NULL, NULL);
>              }
>
> +         if (ok && STMT_VINFO_LIVE_P (stmt_info))
> +           ok = vectorizable_live_operation (phi, NULL, NULL, -1, NULL);
> +
>            if (!ok)
>              {
>                if (dump_enabled_p ())
>
>
>
>