Re: [1/5] Improve tree-vect-patterns.c handling of boolean comparisons

[Richard Biener <richard.guenther@gmail.com>]

On Fri, Nov 29, 2019 at 11:12 AM Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> vect_recog_bool_pattern assumed that a comparison between two booleans
> should always become a comparison of vector mask types (implemented as an
> XOR_EXPR).  But if the booleans in question are generated as data values
> (e.g. because they're loaded directly from memory), we should treat them
> like ordinary integers instead, just as we do for boolean logic ops whose
> operands are loaded from memory.  vect_get_mask_type_for_stmt already
> handled this case:
>
>       /* We may compare boolean value loaded as vector of integers.
>          Fix mask_type in such case.  */
>       if (mask_type
>           && !VECTOR_BOOLEAN_TYPE_P (mask_type)
>           && gimple_code (stmt) == GIMPLE_ASSIGN
>           && TREE_CODE_CLASS (gimple_assign_rhs_code (stmt)) == tcc_comparison)
>         mask_type = truth_type_for (mask_type);
>
> and not handling it here complicated later patches.
>
> The initial list of targets for vect_bool_cmp is deliberately conservative.

OK.

Richard.

>
> 2019-11-30  Richard Sandiford  <richard.sandiford@arm.com>
>
> gcc/
>         * doc/sourcebuild.texi (vect_bool_cmp): Document.
>         * tree-vect-patterns.c (search_type_for_mask_1): If neither
>         operand to a boolean comparison is a natural vector mask,
>         handle both operands like normal integers instead.
>
> gcc/testsuite/
>         * gcc.dg/vect/vect-bool-cmp-2.c: New test.
>         * lib/target-supports.exp (check_effective_target_vect_bool_cmp): New
>         effective target procedure.
>
> Index: gcc/doc/sourcebuild.texi
> ===================================================================
> --- gcc/doc/sourcebuild.texi    2019-11-20 21:11:59.065472803 +0000
> +++ gcc/doc/sourcebuild.texi    2019-11-29 09:11:21.365130870 +0000
> @@ -1522,6 +1522,10 @@ Target does not support a vector add ins
>  @item vect_no_bitwise
>  Target does not support vector bitwise instructions.
>
> +@item vect_bool_cmp
> +Target supports comparison of @code{bool} vectors for at least one
> +vector length.
> +
>  @item vect_char_add
>  Target supports addition of @code{char} vectors for at least one
>  vector length.
> Index: gcc/tree-vect-patterns.c
> ===================================================================
> --- gcc/tree-vect-patterns.c    2019-11-16 10:29:21.207212217 +0000
> +++ gcc/tree-vect-patterns.c    2019-11-29 09:11:21.389130702 +0000
> @@ -3944,7 +3944,8 @@ search_type_for_mask_1 (tree var, vec_in
>                                              vinfo, cache);
>               if (!res || (res2 && TYPE_PRECISION (res) > TYPE_PRECISION (res2)))
>                 res = res2;
> -             break;
> +             if (res)
> +               break;
>             }
>
>           comp_vectype = get_vectype_for_scalar_type (vinfo, TREE_TYPE (rhs1));
> Index: gcc/testsuite/gcc.dg/vect/vect-bool-cmp-2.c
> ===================================================================
> --- /dev/null   2019-09-17 11:41:18.176664108 +0100
> +++ gcc/testsuite/gcc.dg/vect/vect-bool-cmp-2.c 2019-11-29 09:11:21.373130815 +0000
> @@ -0,0 +1,10 @@
> +/* { dg-do compile } */
> +
> +void
> +f (_Bool *restrict x, _Bool *restrict y)
> +{
> +  for (int i = 0; i < 128; ++i)
> +    x[i] = x[i] == y[i];
> +}
> +
> +/* { dg-final { scan-tree-dump "loop vectorized" "vect" { target vect_bool_cmp } } } */
> Index: gcc/testsuite/lib/target-supports.exp
> ===================================================================
> --- gcc/testsuite/lib/target-supports.exp       2019-11-26 22:11:24.494545152 +0000
> +++ gcc/testsuite/lib/target-supports.exp       2019-11-29 09:11:21.373130815 +0000
> @@ -5749,6 +5749,16 @@ proc check_effective_target_vect_bswap {
>              || [istarget amdgcn-*-*] }}]
>  }
>
> +# Return 1 if the target supports comparison of bool vectors for at
> +# least one vector length.
> +
> +proc check_effective_target_vect_bool_cmp { } {
> +    return [check_cached_effective_target_indexed vect_bool_cmp {
> +      expr { [istarget i?86-*-*] || [istarget x86_64-*-*]
> +            || [istarget aarch64*-*-*]
> +            || [is-effective-target arm_neon] }}]
> +}
> +
>  # Return 1 if the target supports addition of char vectors for at least
>  # one vector length.
>