On Mon, Jun 7, 2021 at 7:59 PM Richard Biener
<richard.guent...@gmail.com> wrote:
>
> On Mon, Jun 7, 2021 at 4:19 PM H.J. Lu <hjl.to...@gmail.com> wrote:
> >
> > 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.
>
> 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. Richard. > Richard. > > > Thanks. > > > > -- > > H.J.
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