Re: Fix PR53185 (vectorizer segfault)

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

On Wed, May 9, 2012 at 2:38 PM, Michael Matz <matz@suse.de> wrote:
> Hi,
>
> the current code for strided loads can't deal with the situation when a
> prologue loop (peeling for alignment) is created after analyzing the data
> refs. ?There are multiple issues (non-constant steps in DRs mainly), so
> this is a simple stop gap.
>
> Regtesting on x86_64-linux (all langs) in progress. ?Okay for trunk?

Ok.

Thanks,
Richard.

>
> Ciao,
> Michael.
> --------------------
> ? ? ? ?PR tree-optimization/53185
> ? ? ? ?* tree-vect-data-refs.c (vect_enhance_data_refs_alignment): Disable
> ? ? ? ?peeling when we see strided loads.
>
> testsuite/
> ? ? ? ?* gcc.dg/vect/pr53185.c: New test.
>
> Index: tree-vect-data-refs.c
> ===================================================================
> --- tree-vect-data-refs.c ? ? ? (revision 187287)
> +++ tree-vect-data-refs.c ? ? ? (working copy)
> @@ -1507,6 +1507,17 @@ vect_enhance_data_refs_alignment (loop_v
> ? ? ? ? ? && GROUP_FIRST_ELEMENT (stmt_info) != stmt)
> ? ? ? ? continue;
>
> + ? ? ?/* FORNOW: Any strided load prevents peeling. ?The induction
> + ? ? ? ? variable analysis will fail when the prologue loop is generated,
> + ? ? ? ?and so we can't generate the new base for the pointer. ?*/
> + ? ? ?if (STMT_VINFO_STRIDE_LOAD_P (stmt_info))
> + ? ? ? {
> + ? ? ? ? if (vect_print_dump_info (REPORT_DETAILS))
> + ? ? ? ? ? fprintf (vect_dump, "strided load prevents peeling");
> + ? ? ? ? do_peeling = false;
> + ? ? ? ? break;
> + ? ? ? }
> +
> ? ? ? /* For invariant accesses there is nothing to enhance. ?*/
> ? ? ? if (integer_zerop (DR_STEP (dr)))
> ? ? ? ?continue;
> Index: testsuite/gcc.dg/vect/pr53185.c
> ===================================================================
> --- testsuite/gcc.dg/vect/pr53185.c ? ? (revision 0)
> +++ testsuite/gcc.dg/vect/pr53185.c ? ? (revision 0)
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -ftree-vectorize" } */
> +unsigned short a, e;
> +int *b, *d;
> +int c;
> +extern int fn2();
> +void fn1 () {
> + ?void *f;
> + ?for (;;) {
> + ? ?fn2 ();
> + ? ?b = f;
> + ? ?e = 0;
> + ? ?for (; e < a; ++e)
> + ? ? ?b[e] = d[e * c];
> + ?}
> +}