Use bit-CCP in range-ops.

  After Jakub and Richi's suggestion of using the same representation
for tracking known bits as we do in CCP, I took a peek at the code and
realized there's a plethora of bit-tracking code there that we could
be sharing with range-ops.  For example, the multiplication
optimizations are way better than what I had cobbled together.  For
that matter, our maybe nonzero tracking as a whole has a lot of room
for improvement.  Being the lazy ass that I am, I think we should just
use one code base (CCP's).

This patch provides a thin wrapper for converting the irange maybe
nonzero bits to what CCP requires, and uses that to call into
bit_value_binop().  I have so far converted the MULT_EXPR range-op
entry to use it, as the DIV_EXPR entry we have gets a case CCP doesn't
get so I'd like to contribute the enhancement to CCP before converting
over.

I'd like to use this approach with the dozen or so tree_code's that
are handled in CCP, thus saving us from having to implement any of
them :).

Early next season I'd like to change irange's internal representation
to a pair of value / mask, and start tracking all known bits.  This
ties in nicely with our plan for tracking known set bits.

Perhaps if the stars align, we could merge the bit twiddling in CCP
into range-ops and have a central repository for it.  That is, once we
make the switch to wide-ints, and assuming there are no performance
issues.  Note that range-ops is our lowest level abstraction.
i.e. it's just the math, there's no GORI or ranger, or even the
concept of a symbolic or SSA.

I'd love to hear comments and ideas, and if no one objects push this.
Please let me know if I missed anything.

Tested on x86-64 Linux.

gcc/ChangeLog:

	* range-op.cc (irange_to_masked_value): New.
	(update_known_bitmask): New.
	(operator_mult::fold_range): Call update_known_bitmask.
---
 gcc/range-op.cc | 63 +++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 50 insertions(+), 13 deletions(-)
  

Pushed.

I'd still love to hear feedback though ;-).

Aldy

On Sun, Nov 6, 2022 at 5:14 PM Aldy Hernandez <aldyh@redhat.com> wrote:
>
> After Jakub and Richi's suggestion of using the same representation
> for tracking known bits as we do in CCP, I took a peek at the code and
> realized there's a plethora of bit-tracking code there that we could
> be sharing with range-ops.  For example, the multiplication
> optimizations are way better than what I had cobbled together.  For
> that matter, our maybe nonzero tracking as a whole has a lot of room
> for improvement.  Being the lazy ass that I am, I think we should just
> use one code base (CCP's).
>
> This patch provides a thin wrapper for converting the irange maybe
> nonzero bits to what CCP requires, and uses that to call into
> bit_value_binop().  I have so far converted the MULT_EXPR range-op
> entry to use it, as the DIV_EXPR entry we have gets a case CCP doesn't
> get so I'd like to contribute the enhancement to CCP before converting
> over.
>
> I'd like to use this approach with the dozen or so tree_code's that
> are handled in CCP, thus saving us from having to implement any of
> them :).
>
> Early next season I'd like to change irange's internal representation
> to a pair of value / mask, and start tracking all known bits.  This
> ties in nicely with our plan for tracking known set bits.
>
> Perhaps if the stars align, we could merge the bit twiddling in CCP
> into range-ops and have a central repository for it.  That is, once we
> make the switch to wide-ints, and assuming there are no performance
> issues.  Note that range-ops is our lowest level abstraction.
> i.e. it's just the math, there's no GORI or ranger, or even the
> concept of a symbolic or SSA.
>
> I'd love to hear comments and ideas, and if no one objects push this.
> Please let me know if I missed anything.
>
> Tested on x86-64 Linux.
>
> gcc/ChangeLog:
>
>         * range-op.cc (irange_to_masked_value): New.
>         (update_known_bitmask): New.
>         (operator_mult::fold_range): Call update_known_bitmask.
> ---
>  gcc/range-op.cc | 63 +++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 50 insertions(+), 13 deletions(-)
>
> diff --git a/gcc/range-op.cc b/gcc/range-op.cc
> index 25c004d8287..6d9914d8d12 100644
> --- a/gcc/range-op.cc
> +++ b/gcc/range-op.cc
> @@ -46,6 +46,54 @@ along with GCC; see the file COPYING3.  If not see
>  #include "wide-int.h"
>  #include "value-relation.h"
>  #include "range-op.h"
> +#include "tree-ssa-ccp.h"
> +
> +// Convert irange bitmasks into a VALUE MASK pair suitable for calling CCP.
> +
> +static void
> +irange_to_masked_value (const irange &r, widest_int &value, widest_int &mask)
> +{
> +  if (r.singleton_p ())
> +    {
> +      mask = 0;
> +      value = widest_int::from (r.lower_bound (), TYPE_SIGN (r.type ()));
> +    }
> +  else
> +    {
> +      mask = widest_int::from (r.get_nonzero_bits (), TYPE_SIGN (r.type ()));
> +      value = 0;
> +    }
> +}
> +
> +// Update the known bitmasks in R when applying the operation CODE to
> +// LH and RH.
> +
> +static void
> +update_known_bitmask (irange &r, tree_code code,
> +                     const irange &lh, const irange &rh)
> +{
> +  if (r.undefined_p ())
> +    return;
> +
> +  widest_int value, mask, lh_mask, rh_mask, lh_value, rh_value;
> +  tree type = r.type ();
> +  signop sign = TYPE_SIGN (type);
> +  int prec = TYPE_PRECISION (type);
> +  signop lh_sign = TYPE_SIGN (lh.type ());
> +  signop rh_sign = TYPE_SIGN (rh.type ());
> +  int lh_prec = TYPE_PRECISION (lh.type ());
> +  int rh_prec = TYPE_PRECISION (rh.type ());
> +
> +  irange_to_masked_value (lh, lh_value, lh_mask);
> +  irange_to_masked_value (rh, rh_value, rh_mask);
> +  bit_value_binop (code, sign, prec, &value, &mask,
> +                  lh_sign, lh_prec, lh_value, lh_mask,
> +                  rh_sign, rh_prec, rh_value, rh_mask);
> +
> +  int_range<2> tmp (type);
> +  tmp.set_nonzero_bits (value | mask);
> +  r.intersect (tmp);
> +}
>
>  // Return the upper limit for a type.
>
> @@ -1774,21 +1822,10 @@ operator_mult::fold_range (irange &r, tree type,
>    if (!cross_product_operator::fold_range (r, type, lh, rh, trio))
>      return false;
>
> -  if (lh.undefined_p ())
> +  if (lh.undefined_p () || rh.undefined_p ())
>      return true;
>
> -  tree t;
> -  if (rh.singleton_p (&t))
> -    {
> -      wide_int w = wi::to_wide (t);
> -      int shift = wi::exact_log2 (w);
> -      if (shift != -1)
> -       {
> -         wide_int nz = lh.get_nonzero_bits ();
> -         nz = wi::lshift (nz, shift);
> -         r.set_nonzero_bits (nz);
> -       }
> -    }
> +  update_known_bitmask (r, MULT_EXPR, lh, rh);
>    return true;
>  }
>
> --
> 2.38.1
>