Re: [0/9] [middle-end] Add param to vec_perm_const hook to specify mode of input operand

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

On Tue, May 24, 2022 at 9:22 PM Prathamesh Kulkarni via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Tue, 24 May 2022 at 14:50, Richard Sandiford
> <richard.sandiford@arm.com> wrote:
> >
> > Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> writes:
> > > diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> > > index c5006afc00d..0a3c733ada9 100644
> > > --- a/gcc/doc/tm.texi
> > > +++ b/gcc/doc/tm.texi
> > > @@ -6088,14 +6088,18 @@ for the given scalar type @var{type}.  @var{is_packed} is false if the scalar
> > >  access using @var{type} is known to be naturally aligned.
> > >  @end deftypefn
> > >
> > > -@deftypefn {Target Hook} bool TARGET_VECTORIZE_VEC_PERM_CONST (machine_mode @var{mode}, rtx @var{output}, rtx @var{in0}, rtx @var{in1}, const vec_perm_indices @var{&sel})
> > > +@deftypefn {Target Hook} bool TARGET_VECTORIZE_VEC_PERM_CONST (machine_mode @var{mode}, machine_mode @var{op_mode}, rtx @var{output}, rtx @var{in0}, rtx @var{in1}, const vec_perm_indices @var{&sel})
> > >  This hook is used to test whether the target can permute up to two
> > > -vectors of mode @var{mode} using the permutation vector @code{sel}, and
> > > -also to emit such a permutation.  In the former case @var{in0}, @var{in1}
> > > -and @var{out} are all null.  In the latter case @var{in0} and @var{in1} are
> > > -the source vectors and @var{out} is the destination vector; all three are
> > > -operands of mode @var{mode}.  @var{in1} is the same as @var{in0} if
> > > -@var{sel} describes a permutation on one vector instead of two.
> > > +vectors of mode @var{op_mode} using the permutation vector @code{sel},
> > > +producing a vector of mode @var{mode}.The hook is also used to emit such
> >
> > Should be two spaces between “@var{mode}.” and “The”.
> >
> > > +a permutation.
> > > +
> > > +When the hook is being used to test whether the target supports a permutation,
> > > +@var{in0}, @var{in1}, and @var{out} are all null.When the hook is being used
> >
> > Same here: missing spaces before “When”.
> >
> > > +to emit a permutation, @var{in0} and @var{in1} are the source vectors of mode
> > > +@var{op_mode} and @var{out} is the destination vector of mode @var{mode}.
> > > +@var{in1} is the same as @var{in0} if @var{sel} describes a permutation on one
> > > +vector instead of two.
> > >
> > >  Return true if the operation is possible, emitting instructions for it
> > >  if rtxes are provided.
> > > diff --git a/gcc/match.pd b/gcc/match.pd
> > > index f5efa77560c..f2a527d9c42 100644
> > > --- a/gcc/match.pd
> > > +++ b/gcc/match.pd
> > > @@ -7596,6 +7596,8 @@ and,
> > >   (with
> > >    {
> > >      tree op0 = @0, op1 = @1, op2 = @2;
> > > +    machine_mode result_mode = TYPE_MODE (type);
> > > +    machine_mode op_mode = TYPE_MODE (TREE_TYPE (op0));
> > >
> > >      /* Build a vector of integers from the tree mask.  */
> > >      vec_perm_builder builder;
> > > @@ -7703,12 +7705,12 @@ and,
> > >              2-argument version.  */
> > >           tree oldop2 = op2;
> > >           if (sel.ninputs () == 2
> > > -            || can_vec_perm_const_p (TYPE_MODE (type), sel, false))
> > > +            || can_vec_perm_const_p (result_mode, op_mode, sel, false))
> > >             op2 = vec_perm_indices_to_tree (TREE_TYPE (op2), sel);
> > >           else
> > >             {
> > >               vec_perm_indices sel2 (builder, 2, nelts);
> > > -             if (can_vec_perm_const_p (TYPE_MODE (type), sel2, false))
> > > +             if (can_vec_perm_const_p (result_mode, op_mode, sel2, false))
> > >                 op2 = vec_perm_indices_to_tree (TREE_TYPE (op2), sel2);
> > >               else
> > >                 /* Not directly supported with either encoding,
> >
> > Please replace the use of TYPE_MODE here:
> >
> >         /* See if the permutation is performing a single element
> >            insert from a CONSTRUCTOR or constant and use a BIT_INSERT_EXPR
> >            in that case.  But only if the vector mode is supported,
> >            otherwise this is invalid GIMPLE.  */
> >         if (TYPE_MODE (type) != BLKmode
> >
> > as well.
> >
> > OK with those changes, thanks.
> Thanks, committed the patch in ae8decf1d2b8329af59592b4fa78ee8dfab3ba5e.

So the present state allows to ask can_vec_perm_const_p but the
implementation asks for

431           if (direct_optab_handler (vec_perm_optab, mode) !=
CODE_FOR_nothing)
432             return true;

which then breaks.  Also the VEC_PERMs are not yet valid.  Any reason this
was committed half-way through the review process of the series?

At least I have a user in the vectorizer ready - allowing more permutes
from existing vectors (of different sizes now) to be SLP vectorized.

Thanks,
Richard.

> Thanks,
> Prathamesh
> >
> > Richard