Pushed to trunk to unblock sparc.
On Fri, May 3, 2024 at 4:24 PM Aldy Hernandez <al...@redhat.com> wrote:
>
> Ahh, that is indeed cleaner, and there's no longer a need to assert
> the sizeof of individual ranges.
>
> It looks like a default constructor is needed for the buffer now, but
> only for the default constructor of Value_Range.
>
> I have verified that the individual range constructors are not called
> on initialization to Value_Range, which was the original point of the
> patch. I have also run our performance suite, and there are no
> changes to VRP or overall.
>
> I would appreciate a review from someone more C++ savvy than me :).
>
> OK for trunk?
>
> On Fri, May 3, 2024 at 11:32 AM Andrew Pinski <pins...@gmail.com> wrote:
> >
> > On Fri, May 3, 2024 at 2:24 AM Aldy Hernandez <al...@redhat.com> wrote:
> > >
> > > Sparc requires strict alignment and is choking on the byte vector in
> > > Value_Range. Is this the right approach, or is there a more canonical
> > > way of forcing alignment?
> >
> > I think the suggestion was to change over to use an union and use the
> > types directly in the union (anonymous unions and unions containing
> > non-PODs are part of C++11).
> > That is:
> > union {
> > int_range_max int_range;
> > frange fload_range;
> > unsupported_range un_range;
> > };
> > ...
> > m_vrange = new (&int_range) int_range_max ();
> > ...
> >
> > Also the canonical way of forcing alignment in C++ is to use aliagnas
> > as my patch in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114912
> > did.
> > Also I suspect the alignment is not word alignment but rather the
> > alignment of HOST_WIDE_INT which is not always the same as the
> > alignment of the pointer but bigger and that is why it is failing on
> > sparc (32bit rather than 64bit).
> >
> > Thanks,
> > Andrew Pinski
> >
> > >
> > > If this is correct, OK for trunk?
> > >
> > > gcc/ChangeLog:
> > >
> > > * value-range.h (class Value_Range): Use a union.
> > > ---
> > > gcc/value-range.h | 24 +++++++++++++++---------
> > > 1 file changed, 15 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/gcc/value-range.h b/gcc/value-range.h
> > > index 934eec9e386..31af7888018 100644
> > > --- a/gcc/value-range.h
> > > +++ b/gcc/value-range.h
> > > @@ -740,9 +740,14 @@ private:
> > > void init (const vrange &);
> > >
> > > vrange *m_vrange;
> > > - // The buffer must be at least the size of the largest range.
> > > - static_assert (sizeof (int_range_max) > sizeof (frange), "");
> > > - char m_buffer[sizeof (int_range_max)];
> > > + union {
> > > + // The buffer must be at least the size of the largest range, and
> > > + // be aligned on a word boundary for strict alignment targets
> > > + // such as sparc.
> > > + static_assert (sizeof (int_range_max) > sizeof (frange), "");
> > > + char m_buffer[sizeof (int_range_max)];
> > > + void *align;
> > > + } u;
> > > };
> > >
> > > // The default constructor is uninitialized and must be initialized
> > > @@ -816,11 +821,11 @@ Value_Range::init (tree type)
> > > gcc_checking_assert (TYPE_P (type));
> > >
> > > if (irange::supports_p (type))
> > > - m_vrange = new (&m_buffer) int_range_max ();
> > > + m_vrange = new (&u.m_buffer) int_range_max ();
> > > else if (frange::supports_p (type))
> > > - m_vrange = new (&m_buffer) frange ();
> > > + m_vrange = new (&u.m_buffer) frange ();
> > > else
> > > - m_vrange = new (&m_buffer) unsupported_range ();
> > > + m_vrange = new (&u.m_buffer) unsupported_range ();
> > > }
> > >
> > > // Initialize object with a copy of R.
> > > @@ -829,11 +834,12 @@ inline void
> > > Value_Range::init (const vrange &r)
> > > {
> > > if (is_a <irange> (r))
> > > - m_vrange = new (&m_buffer) int_range_max (as_a <irange> (r));
> > > + m_vrange = new (&u.m_buffer) int_range_max (as_a <irange> (r));
> > > else if (is_a <frange> (r))
> > > - m_vrange = new (&m_buffer) frange (as_a <frange> (r));
> > > + m_vrange = new (&u.m_buffer) frange (as_a <frange> (r));
> > > else
> > > - m_vrange = new (&m_buffer) unsupported_range (as_a
> > > <unsupported_range> (r));
> > > + m_vrange
> > > + = new (&u.m_buffer) unsupported_range (as_a <unsupported_range>
> > > (r));
> > > }
> > >
> > > // Assignment operator. Copying incompatible types is allowed. That
> > > --
> > > 2.44.0
> > >
> >
