Re: [21/nn] Minor vn_reference_lookup_3 tweak

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

On Mon, Oct 23, 2017 at 1:30 PM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> The repeated checks for MEM_REF made this code hard to convert to
> poly_ints as-is.  Hopefully the new structure also makes it clearer
> at a glance what the two cases are.
>
>
> 2017-10-23  Richard Sandiford  <richard.sandiford@linaro.org>
>             Alan Hayward  <alan.hayward@arm.com>
>             David Sherwood  <david.sherwood@arm.com>
>
> gcc/
>         * tree-ssa-sccvn.c (vn_reference_lookup_3): Avoid repeated
>         checks for MEM_REF.
>
> Index: gcc/tree-ssa-sccvn.c
> ===================================================================
> --- gcc/tree-ssa-sccvn.c        2017-10-23 11:47:03.852769480 +0100
> +++ gcc/tree-ssa-sccvn.c        2017-10-23 11:47:44.596155858 +0100
> @@ -2234,6 +2234,7 @@ vn_reference_lookup_3 (ao_ref *ref, tree
>           || offset % BITS_PER_UNIT != 0
>           || ref->size % BITS_PER_UNIT != 0)
>         return (void *)-1;
> +      at = offset / BITS_PER_UNIT;

can you move this just

>        /* Extract a pointer base and an offset for the destination.  */
>        lhs = gimple_call_arg (def_stmt, 0);
> @@ -2301,19 +2302,18 @@ vn_reference_lookup_3 (ao_ref *ref, tree
>        copy_size = tree_to_uhwi (gimple_call_arg (def_stmt, 2));
>
>        /* The bases of the destination and the references have to agree.  */

here? Ok with that change.

Richard.

> -      if ((TREE_CODE (base) != MEM_REF
> -          && !DECL_P (base))
> -         || (TREE_CODE (base) == MEM_REF
> -             && (TREE_OPERAND (base, 0) != lhs
> -                 || !tree_fits_uhwi_p (TREE_OPERAND (base, 1))))
> -         || (DECL_P (base)
> -             && (TREE_CODE (lhs) != ADDR_EXPR
> -                 || TREE_OPERAND (lhs, 0) != base)))
> +      if (TREE_CODE (base) == MEM_REF)
> +       {
> +         if (TREE_OPERAND (base, 0) != lhs
> +             || !tree_fits_uhwi_p (TREE_OPERAND (base, 1)))
> +           return (void *) -1;
> +         at += tree_to_uhwi (TREE_OPERAND (base, 1));
> +       }
> +      else if (!DECL_P (base)
> +              || TREE_CODE (lhs) != ADDR_EXPR
> +              || TREE_OPERAND (lhs, 0) != base)
>         return (void *)-1;
>
> -      at = offset / BITS_PER_UNIT;
> -      if (TREE_CODE (base) == MEM_REF)
> -       at += tree_to_uhwi (TREE_OPERAND (base, 1));
>        /* If the access is completely outside of the memcpy destination
>          area there is no aliasing.  */
>        if (lhs_offset >= at + maxsize / BITS_PER_UNIT