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diff --git a/gcc/rtl-ssa/changes.h b/gcc/rtl-ssa/changes.h
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+// RTL SSA classes related to changing instructions                 -*- C++ -*-
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// 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/>.
+
+namespace rtl_ssa {
+
+// A class that describes a change that we're considering making to an
+// instruction.  There are three choices:
+//
+// (1) delete the instruction
+// (2) replace the instruction with a new instruction in-place
+// (3) replace the instruction with a new instruction at a different location
+//
+// Anything related to the "new instruction" is irrelevant for (1).
+//
+// The class doesn't actually change anything itself, it simply records
+// something that we might do.
+class insn_change
+{
+public:
+  enum delete_action { DELETE };
+
+  // Construct a possible change to INSN.
+  insn_change (insn_info *insn);
+
+  // Construct a possible deletion of INSN.
+  insn_change (insn_info *insn, delete_action);
+
+  // The instruction that we would change.
+  insn_info *insn () const { return m_insn; }
+
+  // The rtx_insn of the instruction that we would change.
+  rtx_insn *rtl () const { return m_insn->rtl (); }
+
+  // The basic block that contains insn ().
+  bb_info *bb () const { return m_insn->bb (); }
+
+  // The extended basic block that contains insn ().
+  ebb_info *ebb () const { return m_insn->ebb (); }
+
+  // The uid of the instruction that we would change.
+  unsigned int insn_uid () const { return m_insn->uid (); }
+
+  // The list of things that the original instruction defined and used.
+  def_array old_defs () const { return m_insn->defs (); }
+  use_array old_uses () const { return m_insn->uses (); }
+
+  // The cost of the original instruction, as calculated by the target.
+  unsigned int old_cost () const { return m_insn->cost (); }
+
+  // Return true if the original instruction would simply be deleted,
+  // rather than being replaced by a new instruction.
+  bool is_deletion () const { return m_is_deletion; }
+
+  // Print a description of the change to PP.
+  void print (pretty_printer *pp) const;
+
+  // Return an insn_change for deleting INSN.
+  static insn_change delete_insn (insn_info *insn) { return { insn, DELETE }; }
+
+private:
+  // The value returned by insn ().
+  insn_info *m_insn;
+
+public:
+  // The list of things that the new instruction would define and use.
+  def_array new_defs;
+  use_array new_uses;
+
+  // The range of instructions after which the instruction could be placed.
+  // The range can include INSN itself: placing the instruction after either
+  // INSN or INSN->prev_nondebug_insn () is equivalent to not moving the
+  // instruction.
+  insn_range_info move_range;
+
+  // The cost that the new instruction would have, as calculated by the target.
+  unsigned int new_cost;
+
+private:
+  // The value returned by is_deletion ().
+  bool m_is_deletion;
+};
+
+// A class that represents a closure of the two-argument form of
+// insn_is_changing.  See the comment above the one-argument form
+// for details.
+class insn_is_changing_closure
+{
+public:
+  insn_is_changing_closure (array_slice<insn_change *const> changes);
+  bool operator() (const insn_info *) const;
+
+private:
+  array_slice<insn_change *const> m_changes;
+};
+
+void pp_insn_change (pretty_printer *, const insn_change &);
+
+}
+
+void dump (FILE *, const rtl_ssa::insn_change &);
+
+void DEBUG_FUNCTION debug (const rtl_ssa::insn_change &);