[PATCH] [vect]Use intermiediate integer type for float_expr/fix_trunc_expr when direct optab is not existed.

[Richard Biener]

On Wed, Jun 21, 2023 at 9:50 AM Uros Bizjak via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Tue, Jun 20, 2023 at 6:11 PM liuhongt via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > I notice there's some refactor in vectorizable_conversion
> > for code_helper,so I've adjusted my patch to that.
> > Here's the patch I'm going to commit.
> >
> > We have already use intermidate type in case WIDEN, but not for NONE,
> > this patch extended that.
> >
> > gcc/ChangeLog:
> >
> >         PR target/110018
> >         * tree-vect-stmts.cc (vectorizable_conversion): Use
> >         intermiediate integer type for float_expr/fix_trunc_expr when
> >         direct optab is not existed.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * gcc.target/i386/pr110018-1.c: New test.
>
> > +
> > +      /* For conversions between float and smaller integer types try whether we
> > +        can use intermediate signed integer types to support the
> > +        conversion.  */
>
> I'm trying to enhance testcase coverage with explicit signed/unsigned
> types (patch attached), and I have noticed that zero-extension is used
> for unsigned types. So, the above comment that mentions only signed
> integer types is not entirely correct.

The comment says the intermediate sized vector types are always
signed (because float conversions to/from unsigned are always somewhat
awkward), but yes, if the original type was unsigned zero-extension is
used and if it was signed sign-extension.

The testcase adjustments / additions look good to me btw.

Thanks,
Richard.

>
> Uros.