On Mon, Jun 7, 2021 at 12:12 AM Richard Sandiford
<richard.sandif...@arm.com> wrote:
>
> "H.J. Lu" <hjl.to...@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.
Thanks.
--
H.J.
