On Tue, 9 Aug 2016, Jakub Jelinek wrote:
> On Tue, Aug 09, 2016 at 08:53:54AM +0200, Richard Biener wrote:
> > Hmm, I don't think we should see -0.0 as +0.0 with -fno-signed-zeros.
> > As far as I can see this is a memory load/store op and we may not
> > transform, say,
> >
> > double x = a[i];
> > b[i] = x;
> >
> > into a copy that changes -0.0 to +0.0. loop distribution looks for
> > a value with all-zero bytes.
>
> So shall I just drop the if (!HONOR_SIGNED_ZEROS (val)) return 0; from the
> patch? With that removed, it will not transform b[i] = -0.0; into
> memset (b, 0, ...); even with -fno-signed-zeros.
Yes, ok with that change (maybe add a comment that we do this on purpose).
Thanks,
Richard.
> > > 2016-08-08 Jakub Jelinek <ja...@redhat.com>
> > >
> > > PR tree-optimization/72824
> > > * tree-loop-distribution.c (const_with_all_bytes_same): If honoring
> > > signed zeros, verify real_zerop is not negative.
> > >
> > > * gcc.c-torture/execute/ieee/pr72824.c: New test.
> > >
> > > --- gcc/tree-loop-distribution.c.jj 2016-07-16 10:41:04.000000000
> > > +0200
> > > +++ gcc/tree-loop-distribution.c 2016-08-07 13:55:19.704681784 +0200
> > > @@ -750,12 +750,40 @@ const_with_all_bytes_same (tree val)
> > > int i, len;
> > >
> > > if (integer_zerop (val)
> > > - || real_zerop (val)
> > > || (TREE_CODE (val) == CONSTRUCTOR
> > > && !TREE_CLOBBER_P (val)
> > > && CONSTRUCTOR_NELTS (val) == 0))
> > > return 0;
> > >
> > > + if (real_zerop (val))
> > > + {
> > > + if (!HONOR_SIGNED_ZEROS (val))
> > > + return 0;
> > > + /* If honoring signed zeros, only return 0 for +0.0, not for -0.0.
> > > */
> > > + switch (TREE_CODE (val))
> > > + {
> > > + case REAL_CST:
> > > + if (!real_isneg (TREE_REAL_CST_PTR (val)))
> > > + return 0;
> > > + break;
> > > + case COMPLEX_CST:
> > > + if (!const_with_all_bytes_same (TREE_REALPART (val))
> > > + && !const_with_all_bytes_same (TREE_IMAGPART (val)))
> > > + return 0;
> > > + break;
> > > + case VECTOR_CST:
> > > + unsigned int j;
> > > + for (j = 0; j < VECTOR_CST_NELTS (val); ++j)
> > > + if (const_with_all_bytes_same (val))
> > > + break;
> > > + if (j == VECTOR_CST_NELTS (val))
> > > + return 0;
> > > + break;
> > > + default:
> > > + break;
> > > + }
> > > + }
> > > +
> > > if (CHAR_BIT != 8 || BITS_PER_UNIT != 8)
> > > return -1;
> > >
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
