On Mon, 29 Jul 2024, Jakub Jelinek wrote:
> On Mon, Jul 29, 2024 at 02:14:40PM +0200, Richard Biener wrote:
> > The following adds a target hook to specify whether regs of MODE can be
> > used to transfer bits. The hook is supposed to be used for value-numbering
> > to decide whether a value loaded in such mode can be punned to another
> > mode instead of re-loading the value in the other mode and for SRA to
> > decide whether MODE is suitable as container holding a value to be
> > used in different modes.
> >
> > * target.def (mode_can_transfer_bits): New target hook.
> > * target.h (mode_can_transfer_bits): New function wrapping the
> > hook and providing default behavior.
> > * doc/tm.texi.in: Update.
> > * doc/tm.texi: Re-generate.
>
>
> > --- a/gcc/target.h
> > +++ b/gcc/target.h
> > @@ -312,6 +312,21 @@ estimated_poly_value (poly_int64 x,
> > return targetm.estimated_poly_value (x, kind);
> > }
> >
> > +/* Return true when MODE can be used to copy GET_MODE_BITSIZE bits
> > + unchanged. */
> > +
> > +inline bool
> > +mode_can_transfer_bits (machine_mode mode)
> > +{
>
> Shouldn't this start with
> mode = GET_MODE_INNER (mode);
> ?
I specifically wanted to avoid this (at least for the purpose of the
hook).
> I mean say XCmode has similar problems as XFmode, or
> V4SFmode as SFmode if i?86 -mno-sse.
> Though, admittedly, with i?86 -msse2 -mfpmath=387 perhaps some vector modes
> could work, which would argue for passing even vector modes to the hook.
> Though the GET_MODE_BITSIZE != GET_MODE_PRECISION check then wants the inner
> modes maybe.
We do not support vector inner modes with padding. I didn't think of
XCmode - though precision is 160 here and size 192, so the padding
check should work there as well.
For vector I think the x86 backend ensures we never get x87 modes as
components. The middle-end will also not allow vector(1) float
with SFmode like it allows vector(1) int with SImode.
That said, the i386 implementation needs to handle XCmode, will
adjust.
Richard.
>
> > + if (mode == BLKmode)
> > + return true;
> > + if (maybe_ne (GET_MODE_BITSIZE (mode), GET_MODE_PRECISION (mode)))
> > + return false;
> > + if (targetm.mode_can_transfer_bits)
> > + return targetm.mode_can_transfer_bits (mode);
> > + return true;
> > +}
> > +
> > #ifdef GCC_TM_H
> >
> > #ifndef CUMULATIVE_ARGS_MAGIC
> > --
> > 2.35.3
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
