Re: [PATCH v2 03/11] Remove MAX_BITSIZE_MODE_ANY_INT

["H.J. Lu" <hjl.tools@gmail.com>]

On Wed, May 12, 2021 at 2:00 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Wed, May 12, 2021 at 1:35 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > It is only defined for i386 and everyone uses the default:
> >
> >  #define MAX_BITSIZE_MODE_ANY_INT (64*BITS_PER_UNIT)
>
> The default is determined by genmodes.c which looks at the maximum
> size of any [partial] integer mode.  Since we have
>
> INT_MODE (OI, 32);
> INT_MODE (XI, 64);
>
> this will increase the size of wide_int.  aarch64 and arm are the only
> other targets with XImode, OImode is also used by s390 and ia64.
>
> Keeping wide_int small is desirable.

Since I want to use OImode and XImode in op_by_pieces operations,
wide_int needs to support OImode and XImode.

> Richard.
>
> > Whatever problems we had before, they have been fixed now.
> >
> >         * config/i386/i386-modes.def (MAX_BITSIZE_MODE_ANY_INT): Removed.
> > ---
> >  gcc/config/i386/i386-modes.def | 15 +++------------
> >  1 file changed, 3 insertions(+), 12 deletions(-)
> >
> > diff --git a/gcc/config/i386/i386-modes.def b/gcc/config/i386/i386-modes.def
> > index dbddfd8e48f..4e7014be034 100644
> > --- a/gcc/config/i386/i386-modes.def
> > +++ b/gcc/config/i386/i386-modes.def
> > @@ -107,19 +107,10 @@ INT_MODE (XI, 64);
> >  PARTIAL_INT_MODE (HI, 16, P2QI);
> >  PARTIAL_INT_MODE (SI, 32, P2HI);
> >
> > -/* Mode used for signed overflow checking of TImode.  As
> > -   MAX_BITSIZE_MODE_ANY_INT is only 160, wide-int.h reserves only that
> > -   rounded up to multiple of HOST_BITS_PER_WIDE_INT bits in wide_int etc.,
> > -   so OImode is too large.  For the overflow checking we actually need
> > -   just 1 or 2 bits beyond TImode precision.  Use 160 bits to have
> > -   a multiple of 32.  */
> > +/* Mode used for signed overflow checking of TImode.  For the overflow
> > +   checking we actually need just 1 or 2 bits beyond TImode precision.
> > +   Use 160 bits to have a multiple of 32.  */
> >  PARTIAL_INT_MODE (OI, 160, POI);
> >
> > -/* Keep the OI and XI modes from confusing the compiler into thinking
> > -   that these modes could actually be used for computation.  They are
> > -   only holders for vectors during data movement.  Include POImode precision
> > -   though.  */
> > -#define MAX_BITSIZE_MODE_ANY_INT (160)
> > -
> >  /* The symbol Pmode stands for one of the above machine modes (usually SImode).
> >     The tm.h file specifies which one.  It is not a distinct mode.  */
> > --
> > 2.31.1
> >



-- 
H.J.