[PATCH] middle-end/100951 - make sure to generate VECTOR_CST in lowering

H.J. Lu hjl.tools@gmail.com
Wed Jun 9 21:31:01 GMT 2021


On Wed, Jun 9, 2021 at 2:03 PM Jeff Law <jeffreyalaw@gmail.com> wrote:
>
>
>
> On 6/7/2021 2:33 PM, H.J. Lu via Gcc-patches wrote:
>
> On Mon, Jun 7, 2021 at 11:10 AM Richard Biener
> <richard.guenther@gmail.com> wrote:
>
> On Mon, Jun 7, 2021 at 7:59 PM Richard Biener
> <richard.guenther@gmail.com> wrote:
>
> On Mon, Jun 7, 2021 at 4:19 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Mon, Jun 7, 2021 at 12:12 AM Richard Sandiford
> <richard.sandiford@arm.com> wrote:
>
> "H.J. Lu" <hjl.tools@gmail.com> writes:
>
> Update vec_duplicate to allow to fail so that backend can only allow
> broadcasting an integer constant to a vector when broadcast instruction
> is available.
>
> I'm not sure why we need this to fail though.  Once the optab is defined
> for target X, the optab should handle all duplicates for target X,
> even if there are different strategies it can use.
>
> AIUI the case you want to make conditional is the constant case.
> I guess the first question is: why don't we simplify those CONSTRUCTORs
> to VECTOR_CSTs in gimple?  I'm surprised we still see the constant case
> as a constructor here.
>
> The particular testcase for vec_duplicate is gcc.dg/pr100239.c.
>
> If we can't rely on that happening, then would it work to change:
>
>         /* Try using vec_duplicate_optab for uniform vectors.  */
>         if (!TREE_SIDE_EFFECTS (exp)
>             && VECTOR_MODE_P (mode)
>             && eltmode == GET_MODE_INNER (mode)
>             && ((icode = optab_handler (vec_duplicate_optab, mode))
>                 != CODE_FOR_nothing)
>             && (elt = uniform_vector_p (exp)))
>
> to something like:
>
>         /* Try using vec_duplicate_optab for uniform vectors.  */
>         if (!TREE_SIDE_EFFECTS (exp)
>             && VECTOR_MODE_P (mode)
>             && eltmode == GET_MODE_INNER (mode)
>             && (elt = uniform_vector_p (exp)))
>           {
>             if (TREE_CODE (elt) == INTEGER_CST
>                 || TREE_CODE (elt) == POLY_INT_CST
>                 || TREE_CODE (elt) == REAL_CST
>                 || TREE_CODE (elt) == FIXED_CST)
>               {
>                 rtx src = gen_const_vec_duplicate (mode, expand_normal (node));
>                 emit_move_insn (target, src);
>                 break;
>               }
>>           }
>
> I will give it a try.
>
> I can confirm that veclower leaves us with an unfolded constant CTOR.
> If you file a PR to remind me I'll fix that.
>
> The attached untested patch fixes this for the testcase.
>
> Here is the patch + the testcase.
>
>
> 0001-middle-end-100951-make-sure-to-generate-VECTOR_CST-i.patch
>
> From aac56894719b59e552b493c970946225ed8c27f6 Mon Sep 17 00:00:00 2001
> From: Richard Biener <rguenther@suse.de>
> Date: Mon, 7 Jun 2021 20:08:13 +0200
> Subject: [PATCH] middle-end/100951 - make sure to generate VECTOR_CST in
>  lowering
>
> When vector lowering creates piecewise ops make sure to create
> VECTOR_CSTs instead of CONSTRUCTORs when possible.
>
> gcc/
>
> 2021-06-07  Richard Biener  <rguenther@suse.de>
>
> PR middle-end/100951
> * tree-vect-generic.c (): Build a VECTOR_CST if all
> elements are constant.
>
> gcc/testsuite/
>
> 2021-06-07  H.J. Lu  <hjl.tools@gmail.com>
>
> PR middle-end/100951
> * gcc.target/i386/pr100951.c: New test.
>
> Assuming this passed testing it is OK.
> jeff

Richard has committed:

commit ffe3a37f54ab866d85bdde48c2a32be5e09d8515
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Jun 7 20:08:13 2021 +0200

    middle-end/100951 - make sure to generate VECTOR_CST in lowering

    When vector lowering creates piecewise ops make sure to create
    VECTOR_CSTs instead of CONSTRUCTORs when possible.


-- 
H.J.


More information about the Gcc-patches mailing list