/*

 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

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 */

#include "incls/_precompiled.incl"

#include "incls/_split_if.cpp.incl"

//------------------------------split_thru_region------------------------------

// Split Node 'n' through merge point.

Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) {

  uint wins = 0;

  assert( n->is_CFG(), "" );

  assert( region->is_Region(), "" );

  Node *r = new (C, region->req()) RegionNode( region->req() );

  IdealLoopTree *loop = get_loop( n );

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

    Node *x = n->clone();

    Node *in0 = n->in(0);

    if( in0->in(0) == region ) x->set_req( 0, in0->in(i) );

    for( uint j = 1; j < n->req(); j++ ) {

      Node *in = n->in(j);

      if( get_ctrl(in) == region )

        x->set_req( j, in->in(i) );

    }

    _igvn.register_new_node_with_optimizer(x);

    set_loop(x, loop);

    set_idom(x, x->in(0), dom_depth(x->in(0))+1);

    r->init_req(i, x);

  }

  // Record region

  r->set_req(0,region);         // Not a TRUE RegionNode

  _igvn.register_new_node_with_optimizer(r);

  set_loop(r, loop);

  if( !loop->_child )

    loop->_body.push(r);

  return r;

}

//------------------------------split_up---------------------------------------

// Split block-local op up through the phis to empty the current block

bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {

  if( n->is_CFG() ) {

    assert( n->in(0) != blk1, "Lousy candidate for split-if" );

    return false;

  }

  if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 )

    return false;               // Not block local

  if( n->is_Phi() ) return false; // Local PHIs are expected

  // Recursively split-up inputs

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

    if( split_up( n->in(i), blk1, blk2 ) ) {

      // Got split recursively and self went dead?

      if (n->outcnt() == 0)

        _igvn.remove_dead_node(n);

      return true;

    }

  }

  // Check for needing to clone-up a compare.  Can't do that, it forces

  // another (nested) split-if transform.  Instead, clone it "down".

  if( n->is_Cmp() ) {

    assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");

    // Check for simple Cmp/Bool/CMove which we can clone-up.  Cmp/Bool/CMove

    // sequence can have no other users and it must all reside in the split-if

    // block.  Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -

    // private, per-use versions of the Cmp and Bool are made.  These sink to

    // the CMove block.  If the CMove is in the split-if block, then in the

    // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.

    Node *bol, *cmov;

    if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() &&

          (bol = n->unique_out()->as_Bool()) &&

          (get_ctrl(bol) == blk1 ||

           get_ctrl(bol) == blk2) &&

          bol->outcnt() == 1 &&

          bol->unique_out()->is_CMove() &&

          (cmov = bol->unique_out()->as_CMove()) &&

          (get_ctrl(cmov) == blk1 ||

           get_ctrl(cmov) == blk2) ) ) {

      // Must clone down

#ifndef PRODUCT

      if( PrintOpto && VerifyLoopOptimizations ) {

        tty->print("Cloning down: ");

        n->dump();

      }

#endif

      // Clone down any block-local BoolNode uses of this CmpNode

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

        Node* bol = n->out(i);

        assert( bol->is_Bool(), "" );

        if (bol->outcnt() == 1) {

          Node* use = bol->unique_out();

          Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use);

          if (use_c == blk1 || use_c == blk2) {

            continue;

          }

        }

        if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) {

          // Recursively sink any BoolNode

#ifndef PRODUCT

          if( PrintOpto && VerifyLoopOptimizations ) {

            tty->print("Cloning down: ");

            bol->dump();

          }

#endif

          for (DUIterator_Last jmin, j = bol->last_outs(jmin); j >= jmin; --j) {

            // Uses are either IfNodes or CMoves

            Node* iff = bol->last_out(j);

            assert( iff->in(1) == bol, "" );

            // Get control block of either the CMove or the If input

            Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);

            Node *x = bol->clone();

            register_new_node(x, iff_ctrl);

            _igvn.hash_delete(iff);

            iff->set_req(1, x);

            _igvn._worklist.push(iff);

          }

          _igvn.remove_dead_node( bol );

          --i;

        }

      }

      // Clone down this CmpNode

      for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {

        Node* bol = n->last_out(j);

        assert( bol->in(1) == n, "" );

        Node *x = n->clone();

        register_new_node(x, get_ctrl(bol));

        _igvn.hash_delete(bol);

        bol->set_req(1, x);

        _igvn._worklist.push(bol);

      }

      _igvn.remove_dead_node( n );

      return true;

    }

  }

  // See if splitting-up a Store.  Any anti-dep loads must go up as

  // well.  An anti-dep load might be in the wrong block, because in

  // this particular layout/schedule we ignored anti-deps and allow

  // memory to be alive twice.  This only works if we do the same

  // operations on anti-dep loads as we do their killing stores.

  if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {

    // Get store's memory slice

    int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());

    // Get memory-phi anti-dep loads will be using

    Node *memphi = n->in(MemNode::Memory);

    assert( memphi->is_Phi(), "" );

    // Hoist any anti-dep load to the splitting block;

    // it will then "split-up".

    for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {

      Node *load = memphi->fast_out(i);

      if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )

        set_ctrl(load,blk1);

    }

  }

  // Found some other Node; must clone it up

#ifndef PRODUCT

  if( PrintOpto && VerifyLoopOptimizations ) {

    tty->print("Cloning up: ");

    n->dump();

  }

#endif

  // Now actually split-up this guy.  One copy per control path merging.

  Node *phi = PhiNode::make_blank(blk1, n);

  for( uint j = 1; j < blk1->req(); j++ ) {

    Node *x = n->clone();

    if( n->in(0) && n->in(0) == blk1 )

      x->set_req( 0, blk1->in(j) );

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

      Node *m = n->in(i);

      if( get_ctrl(m) == blk1 ) {

        assert( m->in(0) == blk1, "" );

        x->set_req( i, m->in(j) );

      }

    }

    register_new_node( x, blk1->in(j) );

    phi->init_req( j, x );

  }

  // Announce phi to optimizer

  register_new_node(phi, blk1);

  // Remove cloned-up value from optimizer; use phi instead

  _igvn.hash_delete(n);

  _igvn.subsume_node( n, phi );

  // (There used to be a self-recursive call to split_up() here,

  // but it is not needed.  All necessary forward walking is done

  // by do_split_if() below.)

  return true;

}

//------------------------------register_new_node------------------------------

void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {

  assert(!n->is_CFG(), "must be data node");

  _igvn.register_new_node_with_optimizer(n);

  set_ctrl(n, blk);

  IdealLoopTree *loop = get_loop(blk);

  if( !loop->_child )

    loop->_body.push(n);

}

//------------------------------small_cache------------------------------------

struct small_cache : public Dict {

  small_cache() : Dict( cmpkey, hashptr ) {}

  Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }

  void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }

};

//------------------------------spinup-----------------------------------------

// "Spin up" the dominator tree, starting at the use site and stopping when we

// find the post-dominating point.

// We must be at the merge point which post-dominates 'new_false' and

// 'new_true'.  Figure out which edges into the RegionNode eventually lead up

// to false and which to true.  Put in a PhiNode to merge values; plug in

// the appropriate false-arm or true-arm values.  If some path leads to the

// original IF, then insert a Phi recursively.

Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {

  if (use_blk->is_top())        // Handle dead uses

    return use_blk;

  Node *prior_n = (Node*)0xdeadbeef;

  Node *n = use_blk;            // Get path input

  assert( use_blk != iff_dom, "" );

  // Here's the "spinup" the dominator tree loop.  Do a cache-check

  // along the way, in case we've come this way before.

  while( n != iff_dom ) {       // Found post-dominating point?

    prior_n = n;

    n = idom(n);                // Search higher

    Node *s = cache->probe( prior_n ); // Check cache

    if( s ) return s;           // Cache hit!

  }

  Node *phi_post;

  if( prior_n == new_false || prior_n == new_true ) {

    phi_post = def->clone();

    phi_post->set_req(0, prior_n );

    register_new_node(phi_post, prior_n);

  } else {

    // This method handles both control uses (looking for Regions) or data

    // uses (looking for Phis).  If looking for a control use, then we need

    // to insert a Region instead of a Phi; however Regions always exist

    // previously (the hash_find_insert below would always hit) so we can

    // return the existing Region.

    if( def->is_CFG() ) {

      phi_post = prior_n;       // If looking for CFG, return prior

    } else {

      assert( def->is_Phi(), "" );

      assert( prior_n->is_Region(), "must be a post-dominating merge point" );

      // Need a Phi here

      phi_post = PhiNode::make_blank(prior_n, def);

      // Search for both true and false on all paths till find one.

      for( uint i = 1; i < phi_post->req(); i++ ) // For all paths

        phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );

      Node *t = _igvn.hash_find_insert(phi_post);

      if( t ) {                 // See if we already have this one

        // phi_post will not be used, so kill it

        _igvn.remove_dead_node(phi_post);

        phi_post->destruct();

        phi_post = t;

      } else {

        register_new_node( phi_post, prior_n );

      }

    }

  }

  // Update cache everywhere

  prior_n = (Node*)0xdeadbeef;  // Reset IDOM walk

  n = use_blk;                  // Get path input

  // Spin-up the idom tree again, basically doing path-compression.

  // Insert cache entries along the way, so that if we ever hit this

  // point in the IDOM tree again we'll stop immediately on a cache hit.

  while( n != iff_dom ) {       // Found post-dominating point?

    prior_n = n;

    n = idom(n);                // Search higher

    cache->lru_insert( prior_n, phi_post ); // Fill cache

  } // End of while not gone high enough

  return phi_post;

}

//------------------------------find_use_block---------------------------------

// Find the block a USE is in.  Normally USE's are in the same block as the

// using instruction.  For Phi-USE's, the USE is in the predecessor block

// along the corresponding path.

Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {

  // CFG uses are their own block

  if( use->is_CFG() )

    return use;

  if( use->is_Phi() ) {         // Phi uses in prior block

    // Grab the first Phi use; there may be many.

    // Each will be handled as a separate iteration of

    // the "while( phi->outcnt() )" loop.

    uint j;

    for( j = 1; j < use->req(); j++ )

      if( use->in(j) == def )

        break;

    assert( j < use->req(), "def should be among use's inputs" );

    return use->in(0)->in(j);

  }

  // Normal (non-phi) use

  Node *use_blk = get_ctrl(use);

  // Some uses are directly attached to the old (and going away)

  // false and true branches.

  if( use_blk == old_false ) {

    use_blk = new_false;

    set_ctrl(use, new_false);

  }

  if( use_blk == old_true ) {

    use_blk = new_true;

    set_ctrl(use, new_true);

  }

  if (use_blk == NULL) {        // He's dead, Jim

    _igvn.hash_delete(use);

    _igvn.subsume_node(use, C->top());

  }

  return use_blk;

}

//------------------------------handle_use-------------------------------------

// Handle uses of the merge point.  Basically, split-if makes the merge point

// go away so all uses of the merge point must go away as well.  Most block

// local uses have already been split-up, through the merge point.  Uses from

// far below the merge point can't always be split up (e.g., phi-uses are

// pinned) and it makes too much stuff live.  Instead we use a path-based

// solution to move uses down.

//

// If the use is along the pre-split-CFG true branch, then the new use will

// be from the post-split-CFG true merge point.  Vice-versa for the false

// path.  Some uses will be along both paths; then we sink the use to the

// post-dominating location; we may need to insert a Phi there.

void PhaseIdealLoop::handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true ) {

  Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);

  if( !use_blk ) return;        // He's dead, Jim

  // Walk up the dominator tree until I hit either the old IfFalse, the old

  // IfTrue or the old If.  Insert Phis where needed.

  Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );

  // Found where this USE goes.  Re-point him.

  uint i;

  for( i = 0; i < use->req(); i++ )

    if( use->in(i) == def )

      break;

  assert( i < use->req(), "def should be among use's inputs" );

  _igvn.hash_delete(use);

  use->set_req(i, new_def);

  _igvn._worklist.push(use);

}

//------------------------------do_split_if------------------------------------

// Found an If getting its condition-code input from a Phi in the same block.

// Split thru the Region.

void PhaseIdealLoop::do_split_if( Node *iff ) {

#ifndef PRODUCT

  if( PrintOpto && VerifyLoopOptimizations )

    tty->print_cr("Split-if");

#endif

  C->set_major_progress();

  Node *region = iff->in(0);

  Node *region_dom = idom(region);

  // We are going to clone this test (and the control flow with it) up through

  // the incoming merge point.  We need to empty the current basic block.

  // Clone any instructions which must be in this block up through the merge

  // point.

  DUIterator i, j;

  bool progress = true;

  while (progress) {

    progress = false;

    for (i = region->outs(); region->has_out(i); i++) {

      Node* n = region->out(i);

      if( n == region ) continue;

      // The IF to be split is OK.

      if( n == iff ) continue;

      if( !n->is_Phi() ) {      // Found pinned memory op or such

        if (split_up(n, region, iff)) {

          i = region->refresh_out_pos(i);

          progress = true;

        }

        continue;

      }

      assert( n->in(0) == region, "" );

      // Recursively split up all users of a Phi

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

        Node* m = n->out(j);

        // If m is dead, throw it away, and declare progress

        if (_nodes[m->_idx] == NULL) {

          _igvn.remove_dead_node(m);

          // fall through

        }

        else if (m != iff && split_up(m, region, iff)) {

          // fall through

        } else {

          continue;

        }

        // Something unpredictable changed.

        // Tell the iterators to refresh themselves, and rerun the loop.

        i = region->refresh_out_pos(i);

        j = region->refresh_out_pos(j);

        progress = true;

      }

    }

  }

  // Now we have no instructions in the block containing the IF.

  // Split the IF.

  Node *new_iff = split_thru_region( iff, region );

  // Replace both uses of 'new_iff' with Regions merging True/False

  // paths.  This makes 'new_iff' go dead.

  Node *old_false, *old_true;

  Node *new_false, *new_true;

  for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {

    Node *ifp = iff->last_out(j2);

    assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );

    ifp->set_req(0, new_iff);

    Node *ifpx = split_thru_region( ifp, region );

    // Replace 'If' projection of a Region with a Region of

    // 'If' projections.

    ifpx->set_req(0, ifpx);       // A TRUE RegionNode

    // Setup dominator info

    set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);

    // Check for splitting loop tails

    if( get_loop(iff)->tail() == ifp )

      get_loop(iff)->_tail = ifpx;

    // Replace in the graph with lazy-update mechanism

    new_iff->set_req(0, new_iff); // hook self so it does not go dead

    lazy_replace_proj( ifp, ifpx );

    new_iff->set_req(0, region);

    // Record bits for later xforms

    if( ifp->Opcode() == Op_IfFalse ) {

      old_false = ifp;

      new_false = ifpx;

    } else {

      old_true = ifp;

      new_true = ifpx;

    }

  }

  _igvn.remove_dead_node(new_iff);

  // Lazy replace IDOM info with the region's dominator

  lazy_replace( iff, region_dom );

  // Now make the original merge point go dead, by handling all its uses.

  small_cache region_cache;

  // Preload some control flow in region-cache

  region_cache.lru_insert( new_false, new_false );

  region_cache.lru_insert( new_true , new_true  );

  // Now handle all uses of the splitting block

  for (DUIterator_Last kmin, k = region->last_outs(kmin); k >= kmin; --k) {

    Node* phi = region->last_out(k);

    if( !phi->in(0) ) {         // Dead phi?  Remove it

      _igvn.remove_dead_node(phi);

      continue;

    }

    assert( phi->in(0) == region, "" );

    if( phi == region ) {       // Found the self-reference

      phi->set_req(0, NULL);

      continue;                 // Break the self-cycle

    }

    // Expected common case: Phi hanging off of Region

    if( phi->is_Phi() ) {

      // Need a per-def cache.  Phi represents a def, so make a cache

      small_cache phi_cache;

      // Inspect all Phi uses to make the Phi go dead

      for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {

        Node* use = phi->last_out(l);

        // Compute the new DEF for this USE.  New DEF depends on the path

        // taken from the original DEF to the USE.  The new DEF may be some

        // collection of PHI's merging values from different paths.  The Phis

        // inserted depend only on the location of the USE.  We use a

        // 2-element cache to handle multiple uses from the same block.

        handle_use( use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true );

      } // End of while phi has uses

      // Because handle_use might relocate region->_out,

      // we must refresh the iterator.