/*

 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "memory/resourceArea.hpp"

#include "opto/cfgnode.hpp"

#include "opto/phaseX.hpp"

#include "opto/replacednodes.hpp"

void ReplacedNodes::allocate_if_necessary() {

  if (_replaced_nodes == NULL) {

    _replaced_nodes = new GrowableArray<ReplacedNode>();

  }

}

bool ReplacedNodes::is_empty() const {

  return _replaced_nodes == NULL || _replaced_nodes->length() == 0;

}

bool ReplacedNodes::has_node(const ReplacedNode& r) const {

  return _replaced_nodes->find(r) != -1;

}

bool ReplacedNodes::has_target_node(Node* n) const {

  for (int i = 0; i < _replaced_nodes->length(); i++) {

    if (_replaced_nodes->at(i).improved() == n) {

      return true;

    }

  }

  return false;

}

// Record replaced node if not seen before

void ReplacedNodes::record(Node* initial, Node* improved) {

  allocate_if_necessary();

  ReplacedNode r(initial, improved);

  if (!has_node(r)) {

    _replaced_nodes->push(r);

  }

}

// Copy replaced nodes from one map to another. idx is used to

// identify nodes that are too new to be of interest in the target

// node list.

void ReplacedNodes::transfer_from(const ReplacedNodes& other, uint idx) {

  if (other.is_empty()) {

    return;

  }

  allocate_if_necessary();

  for (int i = 0; i < other._replaced_nodes->length(); i++) {

    ReplacedNode replaced = other._replaced_nodes->at(i);

    // Only transfer the nodes that can actually be useful

    if (!has_node(replaced) && (replaced.initial()->_idx < idx || has_target_node(replaced.initial()))) {

      _replaced_nodes->push(replaced);

    }

  }

}

void ReplacedNodes::clone() {

  if (_replaced_nodes != NULL) {

    GrowableArray<ReplacedNode>* replaced_nodes_clone = new GrowableArray<ReplacedNode>();

    replaced_nodes_clone->appendAll(_replaced_nodes);

    _replaced_nodes = replaced_nodes_clone;

  }

}

void ReplacedNodes::reset() {

  if (_replaced_nodes != NULL) {

    _replaced_nodes->clear();

  }

}

// Perfom node replacement (used when returning to caller)

void ReplacedNodes::apply(Node* n, uint idx) {

  if (is_empty()) {

    return;

  }

  for (int i = 0; i < _replaced_nodes->length(); i++) {

    ReplacedNode replaced = _replaced_nodes->at(i);

    // Only apply if improved node was created in a callee to avoid

    // issues with irreducible loops in the caller

    if (replaced.improved()->_idx >= idx) {

      n->replace_edge(replaced.initial(), replaced.improved());

    }

  }

}

static void enqueue_use(Node* n, Node* use, Unique_Node_List& work) {

  if (use->is_Phi()) {

    Node* r = use->in(0);

    assert(r->is_Region(), "Phi should have Region");

    for (uint i = 1; i < use->req(); i++) {

      if (use->in(i) == n) {

        work.push(r->in(i));

      }

    }

  } else {

    work.push(use);

  }

}

// Perfom node replacement following late inlining

void ReplacedNodes::apply(Compile* C, Node* ctl) {

  // ctl is the control on exit of the method that was late inlined

  if (is_empty()) {

    return;

  }

  for (int i = 0; i < _replaced_nodes->length(); i++) {

    ReplacedNode replaced = _replaced_nodes->at(i);

    Node* initial = replaced.initial();

    Node* improved = replaced.improved();

    assert (ctl != NULL && !ctl->is_top(), "replaced node should have actual control");

    ResourceMark rm;

    Unique_Node_List work;

    // Go over all the uses of the node that is considered for replacement...

    for (DUIterator j = initial->outs(); initial->has_out(j); j++) {

      Node* use = initial->out(j);

      if (use == improved || use->outcnt() == 0) {

        continue;

      }

      work.clear();

      enqueue_use(initial, use, work);

      bool replace = true;

      // Check that this use is dominated by ctl. Go ahead with the

      // replacement if it is.

      while (work.size() != 0 && replace) {

        Node* n = work.pop();

        if (use->outcnt() == 0) {

          continue;

        }

        if (n->is_CFG() || (n->in(0) != NULL && !n->in(0)->is_top())) {

          int depth = 0;

          Node *m = n;

          if (!n->is_CFG()) {

            n = n->in(0);

          }

          assert(n->is_CFG(), "should be CFG now");

          while(n != ctl) {

            n = IfNode::up_one_dom(n);

            depth++;

            // limit search depth

            if (depth >= 100 || n == NULL) {

              replace = false;

              break;

            }

          }

        } else {

          for (DUIterator k = n->outs(); n->has_out(k); k++) {

            enqueue_use(n, n->out(k), work);

          }

        }

      }

      if (replace) {

        bool is_in_table = C->initial_gvn()->hash_delete(use);

        int replaced = use->replace_edge(initial, improved);

        if (is_in_table) {

          C->initial_gvn()->hash_find_insert(use);

        }

        C->record_for_igvn(use);

        assert(replaced > 0, "inconsistent");

        --j;

      }

    }

  }

}

void ReplacedNodes::dump(outputStream *st) const {

  if (!is_empty()) {

    st->print("replaced nodes: ");

    for (int i = 0; i < _replaced_nodes->length(); i++) {

      st->print("%d->%d", _replaced_nodes->at(i).initial()->_idx, _replaced_nodes->at(i).improved()->_idx);

      if (i < _replaced_nodes->length()-1) {

        st->print(",");

      }

    }

  }

}

// Merge 2 list of replaced node at a point where control flow paths merge

void ReplacedNodes::merge_with(const ReplacedNodes& other) {

  if (is_empty()) {

    return;

  }

  if (other.is_empty()) {

    reset();

    return;

  }

  int shift = 0;

  int len = _replaced_nodes->length();

  for (int i = 0; i < len; i++) {

    if (!other.has_node(_replaced_nodes->at(i))) {

      shift++;

    } else if (shift > 0) {

      _replaced_nodes->at_put(i-shift, _replaced_nodes->at(i));

    }

  }

  if (shift > 0) {

    _replaced_nodes->trunc_to(len - shift);

  }

}