Re: [PATCH, ping 1] Move insns without introducing new temporaries in loop2_invariant

[Jeff Law <law at redhat dot com>]

On 05/12/2015 03:32 AM, Thomas Preud'homme wrote:
> > From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
> > owner@gcc.gnu.org] On Behalf Of Thomas Preud'homme
> >
> > > From: Jeff Law [mailto:law@redhat.com]
> > > Sent: Tuesday, May 12, 2015 4:17 AM
> > >
> > > > > +
> > > > > +  /* Check that all uses reached by the def in insn would still be
> > > reached
> > > > > +     it.  */
> > > > > +  dest_regno = REGNO (reg);
> > > > > +  for (use = DF_REG_USE_CHAIN (dest_regno); use; use =
> > > > > DF_REF_NEXT_REG (use))
> > > [ ... ]
> > > So isn't this overly conservative if DEST_REGNO is set multiple times
> > > since it's going to look at all the uses, even those not necessarily
> > > reached by the original SET of DEST_REGNO?
> > >
> > > Or is that not an issue for some reason?  And I'm not requiring you to
> > > make this optimal, but if I'm right, a comment here seems wise.
> >
> > My apologize, it is the comment that is incorrect since it doesn't match
> > the code (a remaining of an old version of this patch). The code actually
> > checks that the use was dominated by the instruction before it is moved
> > out of the loop.
>
> > > I think with the wrapping nits fixed and closure on the multi-set issue
> > > noted immediately above and this will be good for the trunk.
> >
> > I'll fix this comment right away.
>
> Please find below a patch with the comment fixed.
>
>
> *** gcc/ChangeLog ***
>
> 2015-05-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>
>
>          * loop-invariant.c (can_move_invariant_reg): New.
>          (move_invariant_reg): Call above new function to decide whether
>          instruction can just be moved, skipping creation of temporary
>          register.
>
> *** gcc/testsuite/ChangeLog ***
>
> 2015-05-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>
>
>          * gcc.dg/loop-8.c: New test.
>          * gcc.dg/loop-9.c: New test.
OK for the trunk.

Thanks for your patience,

Jeff