Re: [DOC PATCH] Document the VEC_PERM_EXPR tree code (and minor clean-ups).

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

On Sat, Feb 4, 2023 at 9:35 PM Roger Sayle <roger@nextmovesoftware.com> wrote:
>
>
> This patch (primarily) documents the VEC_PERM_EXPR tree code in
> generic.texi.  For ease of review, it is provided below as a pair
> of diffs.  The first contains just the new text added to describe
> VEC_PERM_EXPR, the second tidies up this part of the documentation
> by sorting the tree codes into alphabetical order, and providing
> consistent section naming/capitalization, so changing this section
> from "Vectors" to "Vector Expressions" (matching the nearby
> "Unary and Binary Expressions").
>
> Tested with make pdf and make html on x86_64-pc-linux-gnu.
> The reviewer(s) can decide whether to approve just the new content,
> or the content+clean-up.  Ok for mainline?

+@item VEC_PERM_EXPR
+This node represents a vector permute/blend operation.  The three operands
+must be vectors of the same number of elements.  The first and second
+operands must be vectors of the same type as the entire expression,

this was recently relaxed for the case of constant permutes in which case
the first and second operands only have to have the same element type
as the result.  See tree-cfg.cc:verify_gimple_assign_ternary.

The following description will become a bit more awkward here and
for rhs1/rhs2 with different number of elements the modulo interpretation
doesn't hold - I believe we require in-bounds elements for constant
permutes.  Richard can probably clarify things here.

Thanks,
Richard.

>
>
> 2023-02-04  Roger Sayle  <roger@nextmovesoftware.com>
>
> gcc/ChangeLog
>         * doc/generic.texi <Expression Trees>: Standardize capitalization
>         of section titles from "Expression trees".
>         <Language-dependent Trees>: Likewise standardize capitalization
>         from "Language-dependent trees".
>         <Constant expressions>: Capitalized from "Constant Expressions".
>         <Vector Expressions>: Standardized section name from "Vectors".
>         Document VEC_PERM_EXPR tree code.  Sort tree codes alphabetically.
>
>
> Thanks in advance,
> Roger
> --
>