gcc/range-op.h

/* Header file for range operator class.
   Copyright (C) 2017-2021 Free Software Foundation, Inc.
   Contributed by Andrew MacLeod <amacleod@redhat.com>
   and Aldy Hernandez <aldyh@redhat.com>.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#ifndef GCC_RANGE_OP_H
#define GCC_RANGE_OP_H

// This class is implemented for each kind of operator supported by
// the range generator.  It serves various purposes.
//
// 1 - Generates range information for the specific operation between
//     two ranges.  This provides the ability to fold ranges for an
//     expression.
//
// 2 - Performs range algebra on the expression such that a range can be
//     adjusted in terms of one of the operands:
//
//       def = op1 + op2
//
//     Given a range for def, we can adjust the range so that it is in
//     terms of either operand.
//
//     op1_range (def_range, op2) will adjust the range in place so it
//     is in terms of op1.  Since op1 = def - op2, it will subtract
//     op2 from each element of the range.
//
// 3 - Creates a range for an operand based on whether the result is 0 or
//     non-zero.  This is mostly for logical true false, but can serve other
//     purposes.
//       ie   0 = op1 - op2 implies op2 has the same range as op1.

class range_operator
{
public:
  // Perform an operation between 2 ranges and return it.
  virtual bool fold_range (irange &r, tree type,
			   const irange &lh,
			   const irange &rh,
			   relation_kind rel = VREL_NONE) const;

  // Return the range for op[12] in the general case.  LHS is the range for
  // the LHS of the expression, OP[12]is the range for the other
  //
  // The operand and the result is returned in R.
  //
  // TYPE is the expected type of the range.
  //
  // Return TRUE if the operation is performed and a valid range is available.
  //
  // i.e.  [LHS] = ??? + OP2
  // is re-formed as R = [LHS] - OP2.
  virtual bool op1_range (irange &r, tree type,
			  const irange &lhs,
			  const irange &op2,
			  relation_kind rel = VREL_NONE) const;
  virtual bool op2_range (irange &r, tree type,
			  const irange &lhs,
			  const irange &op1,
			  relation_kind rel = VREL_NONE) const;

  // The following routines are used to represent relations between the
  // various operations.  If the caller knows where the symbolics are,
  // it can query for relationships between them given known ranges.
  virtual enum tree_code lhs_op1_relation (const irange &lhs,
					   const irange &op1,
					   const irange &op2) const;
  virtual enum tree_code lhs_op2_relation (const irange &lhs,
					   const irange &op1,
					   const irange &op2) const;
  virtual enum tree_code op1_op2_relation (const irange &lhs) const;
protected:
  // Perform an integral operation between 2 sub-ranges and return it.
  virtual void wi_fold (irange &r, tree type,
		        const wide_int &lh_lb,
		        const wide_int &lh_ub,
		        const wide_int &rh_lb,
		        const wide_int &rh_ub) const;
  // Side effect of relation for generic fold_range clients.
  virtual bool op1_op2_relation_effect (irange &lhs_range, tree type,
					const irange &op1_range,
					const irange &op2_range,
					relation_kind rel) const;
  // Called by fold range to split small subranges into parts.
  void wi_fold_in_parts (irange &r, tree type,
			 const wide_int &lh_lb,
			 const wide_int &lh_ub,
			 const wide_int &rh_lb,
			 const wide_int &rh_ub) const;
};

extern range_operator *range_op_handler (enum tree_code code, tree type);
extern void range_cast (irange &, tree type);
extern void wi_set_zero_nonzero_bits (tree type,
				      const wide_int &, const wide_int &,
				      wide_int &maybe_nonzero,
				      wide_int &mustbe_nonzero);

#endif // GCC_RANGE_OP_H