On Fri, Sep 10, 2021 at 9:44 PM Hongtao Liu <crazy...@gmail.com> wrote:
>
> On Fri, Sep 10, 2021 at 9:32 PM Richard Biener
> <richard.guent...@gmail.com> wrote:
> >
> > On September 10, 2021 3:27:09 PM GMT+02:00, Hongtao Liu
> > <crazy...@gmail.com> wrote:
> > >On Fri, Sep 10, 2021 at 9:16 PM Richard Biener via Gcc-patches
> > ><gcc-patches@gcc.gnu.org> wrote:
> > >>
> > >> On Fri, Sep 10, 2021 at 2:58 PM liuhongt <hongtao....@intel.com> wrote:
> > >> >
> > >> > gcc/ChangeLog:
> > >> >
> > >> > * expmed.c (extract_bit_field_using_extv): validate_subreg
> > >> > before call gen_lowpart.
> > >> > ---
> > >> > gcc/expmed.c | 6 +++++-
> > >> > 1 file changed, 5 insertions(+), 1 deletion(-)
> > >> >
> > >> > diff --git a/gcc/expmed.c b/gcc/expmed.c
> > >> > index 3143f38e057..10d62d857a8 100644
> > >> > --- a/gcc/expmed.c
> > >> > +++ b/gcc/expmed.c
> > >> > @@ -1571,12 +1571,16 @@ extract_bit_field_using_extv (const
> > >> > extraction_insn *extv, rtx op0,
> > >> >
> > >> > if (GET_MODE (target) != ext_mode)
> > >> > {
> > >> > + machine_mode tmode = GET_MODE (target);
> > >> > /* Don't use LHS paradoxical subreg if explicit truncation is
> > >> > needed
> > >> > between the mode of the extraction (word_mode) and the target
> > >> > mode. Instead, create a temporary and use convert_move to set
> > >> > the target. */
> > >> > if (REG_P (target)
> > >> > - && TRULY_NOOP_TRUNCATION_MODES_P (GET_MODE (target),
> > >> > ext_mode))
> > >>
> > >> ^^^
> > >>
> > >> I wonder if herein lies the problem in that the HFmode "truncation" from
> > >> SImode
> > >> is considered noop? Note the underlying target hook only looks at the
> > >> mode
> > >> precision and thus receives 16 and 32, and thus maybe that
> > >> TRULY_NOOP_TRUNCATION_MODES_P query only makes sense for
> > >> integer modes? Though the documentation of the hook only talks about
> > >> "conversion" of "values" ...
> > >>
> > >> So maybe a targetm.modes_tieable_p (GET_MODE (target), extmode) check
> > >> is missing?
> > >
> > >According to document, it should be true for
> > >targetm.modes_tieable_p(HFmode, SImode) since HFmode can be allocated
> > >to gpr.
> > >
> > >----------------
> > >This hook returns true if a value of mode mode1 is accessible in mode
> > >mode2 without
> > >copying
> > >-------------------
> > >
> > >and also here gen_lowpart (SImode, HFmode, target) is called and hit
> > >gcc_assert, not (subreg:HF (reg:SI) 0)
> >
> > I see. Of course that leads to a suggestion to allow the subreg based on
> > modes_tieable_p, but then others will know why that's the wrong thing to do?
> I'm testing this
>
> 1 file changed, 2 insertions(+), 1 deletion(-)
> gcc/expmed.c | 3 ++-
>
> modified gcc/expmed.c
> @@ -1576,7 +1576,8 @@ extract_bit_field_using_extv (const
> extraction_insn *extv, rtx op0,
> mode. Instead, create a temporary and use convert_move to set
> the target. */
> if (REG_P (target)
> - && TRULY_NOOP_TRUNCATION_MODES_P (GET_MODE (target), ext_mode))
> + && TRULY_NOOP_TRUNCATION_MODES_P (GET_MODE (target), ext_mode)
> + && targetm.modes_tieable_p (GET_MODE (target), ext_mode))
> {
> target = gen_lowpart (ext_mode, target);
> if (partial_subreg_p (GET_MODE (spec_target), ext_mode))
>
Updated patch.
Bootstrapped and regtested on x86_64-linux-gnu{-m32,}, do I need to
run this patch on other targets machine, or the patch is supposed to
have minimal impact on other targets?
Then, ok for trunk?
> >
> > Richard.
> >
> > >>
> > >> > + && TRULY_NOOP_TRUNCATION_MODES_P (tmode, ext_mode)
> > >> > + && validate_subreg (ext_mode, tmode,
> > >> > + target,
> > >> > + subreg_lowpart_offset (ext_mode, tmode)))
> > >> > {
> > >> > target = gen_lowpart (ext_mode, target);
> > >> > if (partial_subreg_p (GET_MODE (spec_target), ext_mode))
> > >> > --
> > >> > 2.27.0
> > >> >
> > >
> > >
> > >
> >
>
>
> --
> BR,
> Hongtao
--
BR,
Hongtao
v2-0001-Check-modes_tieable_p-before-call-gen_lowpart-to-.patch
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