ifnode.cpp

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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#include "ci/ciTypeFlow.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"
#include "opto/addnode.hpp"
#include "opto/castnode.hpp"
#include "opto/cfgnode.hpp"
#include "opto/connode.hpp"
#include "opto/loopnode.hpp"
#include "opto/phaseX.hpp"
#include "opto/predicates_enums.hpp"
#include "opto/runtime.hpp"
#include "opto/rootnode.hpp"
#include "opto/subnode.hpp"
#include "opto/subtypenode.hpp"

// Portions of code courtesy of Clifford Click

// Optimization - Graph Style


#ifndef PRODUCT
extern uint explicit_null_checks_elided;
#endif

IfNode::IfNode(Node* control, Node* bol, float p, float fcnt)
    : MultiBranchNode(2),
      _prob(p),
      _fcnt(fcnt),
      _assertion_predicate_type(AssertionPredicateType::None) {
  init_node(control, bol);
}

IfNode::IfNode(Node* control, Node* bol, float p, float fcnt, AssertionPredicateType assertion_predicate_type)
    : MultiBranchNode(2),
      _prob(p),
      _fcnt(fcnt),
      _assertion_predicate_type(assertion_predicate_type) {
  init_node(control, bol);
}

//=============================================================================
//------------------------------Value------------------------------------------
// Return a tuple for whichever arm of the IF is reachable
const Type* IfNode::Value(PhaseGVN* phase) const {
  if( !in(0) ) return Type::TOP;
  if( phase->type(in(0)) == Type::TOP )
    return Type::TOP;
  const Type *t = phase->type(in(1));
  if( t == Type::TOP )          // data is undefined
    return TypeTuple::IFNEITHER; // unreachable altogether
  if( t == TypeInt::ZERO )      // zero, or false
    return TypeTuple::IFFALSE;  // only false branch is reachable
  if( t == TypeInt::ONE )       // 1, or true
    return TypeTuple::IFTRUE;   // only true branch is reachable
  assert( t == TypeInt::BOOL, "expected boolean type" );

  return TypeTuple::IFBOTH;     // No progress
}

const RegMask &IfNode::out_RegMask() const {
  return RegMask::Empty;
}

//------------------------------split_if---------------------------------------
// Look for places where we merge constants, then test on the merged value.
// If the IF test will be constant folded on the path with the constant, we
// win by splitting the IF to before the merge point.
static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
  // I could be a lot more general here, but I'm trying to squeeze this
  // in before the Christmas '98 break so I'm gonna be kinda restrictive
  // on the patterns I accept.  CNC

  // Look for a compare of a constant and a merged value
  Node *i1 = iff->in(1);
  if( !i1->is_Bool() ) return nullptr;
  BoolNode *b = i1->as_Bool();
  Node *cmp = b->in(1);
  if( !cmp->is_Cmp() ) return nullptr;
  i1 = cmp->in(1);
  if( i1 == nullptr || !i1->is_Phi() ) return nullptr;
  PhiNode *phi = i1->as_Phi();
  Node *con2 = cmp->in(2);
  if( !con2->is_Con() ) return nullptr;
  // See that the merge point contains some constants
  Node *con1=nullptr;
  uint i4;
  RegionNode* phi_region = phi->region();
  for (i4 = 1; i4 < phi->req(); i4++ ) {
    con1 = phi->in(i4);
    // Do not optimize partially collapsed merges
    if (con1 == nullptr || phi_region->in(i4) == nullptr || igvn->type(phi_region->in(i4)) == Type::TOP) {
      igvn->_worklist.push(iff);
      return nullptr;
    }
    if( con1->is_Con() ) break; // Found a constant
    // Also allow null-vs-not-null checks
    const TypePtr *tp = igvn->type(con1)->isa_ptr();
    if( tp && tp->_ptr == TypePtr::NotNull )
      break;
  }
  if( i4 >= phi->req() ) return nullptr; // Found no constants

  igvn->C->set_has_split_ifs(true); // Has chance for split-if

  // Make sure that the compare can be constant folded away
  Node *cmp2 = cmp->clone();
  cmp2->set_req(1,con1);
  cmp2->set_req(2,con2);
  const Type *t = cmp2->Value(igvn);
  // This compare is dead, so whack it!
  igvn->remove_dead_node(cmp2);
  if( !t->singleton() ) return nullptr;

  // No intervening control, like a simple Call
  Node* r = iff->in(0);
  if (!r->is_Region() || r->is_Loop() || phi_region != r || r->as_Region()->is_copy()) {
    return nullptr;
  }

  // No other users of the cmp/bool
  if (b->outcnt() != 1 || cmp->outcnt() != 1) {
    //tty->print_cr("many users of cmp/bool");
    return nullptr;
  }

  // Make sure we can determine where all the uses of merged values go
  for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
    Node* u = r->fast_out(j);
    if( u == r ) continue;
    if( u == iff ) continue;
    if( u->outcnt() == 0 ) continue; // use is dead & ignorable
    if( !u->is_Phi() ) {
      /*
      if( u->is_Start() ) {
        tty->print_cr("Region has inlined start use");
      } else {
        tty->print_cr("Region has odd use");
        u->dump(2);
      }*/
      return nullptr;
    }
    if( u != phi ) {
      // CNC - do not allow any other merged value
      //tty->print_cr("Merging another value");
      //u->dump(2);
      return nullptr;
    }
    // Make sure we can account for all Phi uses
    for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
      Node* v = u->fast_out(k); // User of the phi
      // CNC - Allow only really simple patterns.
      // In particular I disallow AddP of the Phi, a fairly common pattern
      if (v == cmp) continue;  // The compare is OK
      if (v->is_ConstraintCast()) {
        // If the cast is derived from data flow edges, it may not have a control edge.
        // If so, it should be safe to split. But follow-up code can not deal with
        // this (l. 359). So skip.
        if (v->in(0) == nullptr) {
          return nullptr;
        }
        if (v->in(0)->in(0) == iff) {
          continue;               // CastPP/II of the IfNode is OK
        }
      }
      // Disabled following code because I cannot tell if exactly one
      // path dominates without a real dominator check. CNC 9/9/1999
      //uint vop = v->Opcode();
      //if( vop == Op_Phi ) {        // Phi from another merge point might be OK
      //  Node *r = v->in(0);        // Get controlling point
      //  if( !r ) return nullptr;   // Degraded to a copy
      //  // Find exactly one path in (either True or False doms, but not IFF)
      //  int cnt = 0;
      //  for( uint i = 1; i < r->req(); i++ )
      //    if( r->in(i) && r->in(i)->in(0) == iff )
      //      cnt++;
      //  if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
      //}
      if( !v->is_Call() ) {
        /*
        if( v->Opcode() == Op_AddP ) {
          tty->print_cr("Phi has AddP use");
        } else if( v->Opcode() == Op_CastPP ) {
          tty->print_cr("Phi has CastPP use");
        } else if( v->Opcode() == Op_CastII ) {
          tty->print_cr("Phi has CastII use");
        } else {
          tty->print_cr("Phi has use I can't be bothered with");
        }
        */
      }
      return nullptr;

      /* CNC - Cut out all the fancy acceptance tests
      // Can we clone this use when doing the transformation?
      // If all uses are from Phis at this merge or constants, then YES.
      if( !v->in(0) && v != cmp ) {
        tty->print_cr("Phi has free-floating use");
        v->dump(2);
        return nullptr;
      }
      for( uint l = 1; l < v->req(); l++ ) {
        if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
            !v->in(l)->is_Con() ) {
          tty->print_cr("Phi has use");
          v->dump(2);
          return nullptr;
        } // End of if Phi-use input is neither Phi nor Constant
      } // End of for all inputs to Phi-use
      */
    } // End of for all uses of Phi
  } // End of for all uses of Region

  // Only do this if the IF node is in a sane state
  if (iff->outcnt() != 2)
    return nullptr;

  // Got a hit!  Do the Mondo Hack!
  //
  //ABC  a1c   def   ghi            B     1     e     h   A C   a c   d f   g i
  // R - Phi - Phi - Phi            Rc - Phi - Phi - Phi   Rx - Phi - Phi - Phi
  //     cmp - 2                         cmp - 2               cmp - 2
  //       bool                            bool_c                bool_x
  //       if                               if_c                  if_x
  //      T  F                              T  F                  T  F
  // ..s..    ..t ..                   ..s..    ..t..        ..s..    ..t..
  //
  // Split the paths coming into the merge point into 2 separate groups of
  // merges.  On the left will be all the paths feeding constants into the
  // Cmp's Phi.  On the right will be the remaining paths.  The Cmp's Phi
  // will fold up into a constant; this will let the Cmp fold up as well as
  // all the control flow.  Below the original IF we have 2 control
  // dependent regions, 's' and 't'.  Now we will merge the two paths
  // just prior to 's' and 't' from the two IFs.  At least 1 path (and quite
  // likely 2 or more) will promptly constant fold away.
  PhaseGVN *phase = igvn;

  // Make a region merging constants and a region merging the rest
  uint req_c = 0;
  for (uint ii = 1; ii < r->req(); ii++) {
    if (phi->in(ii) == con1) {
      req_c++;
    }
    if (Node::may_be_loop_entry(r->in(ii))) {
      // Bail out if splitting through a region with a Parse Predicate input (could
      // also be a loop header before loop opts creates a LoopNode for it).
      return nullptr;
    }
  }

  // If all the defs of the phi are the same constant, we already have the desired end state.
  // Skip the split that would create empty phi and region nodes.
  if ((r->req() - req_c) == 1) {
    return nullptr;
  }

  // At this point we know that we can apply the split if optimization. If the region is still on the worklist,
  // we should wait until it is processed. The region might be removed which makes this optimization redundant.
  // This also avoids the creation of dead data loops when rewiring data nodes below when a region is dying.
  if (igvn->_worklist.member(r)) {
    igvn->_worklist.push(iff); // retry split if later again
    return nullptr;
  }

  Node *region_c = new RegionNode(req_c + 1);
  Node *phi_c    = con1;
  uint  len      = r->req();
  Node *region_x = new RegionNode(len - req_c);
  Node *phi_x    = PhiNode::make_blank(region_x, phi);
  for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
    if (phi->in(i) == con1) {
      region_c->init_req( i_c++, r  ->in(i) );
    } else {
      region_x->init_req( i_x,   r  ->in(i) );
      phi_x   ->init_req( i_x++, phi->in(i) );
    }
  }

  // Register the new RegionNodes but do not transform them.  Cannot
  // transform until the entire Region/Phi conglomerate has been hacked
  // as a single huge transform.
  igvn->register_new_node_with_optimizer( region_c );
  igvn->register_new_node_with_optimizer( region_x );
  // Prevent the untimely death of phi_x.  Currently he has no uses.  He is
  // about to get one.  If this only use goes away, then phi_x will look dead.
  // However, he will be picking up some more uses down below.
  Node *hook = new Node(4);
  hook->init_req(0, phi_x);
  hook->init_req(1, phi_c);
  phi_x = phase->transform( phi_x );

  // Make the compare
  Node *cmp_c = phase->makecon(t);
  Node *cmp_x = cmp->clone();
  cmp_x->set_req(1,phi_x);
  cmp_x->set_req(2,con2);
  cmp_x = phase->transform(cmp_x);
  // Make the bool
  Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
  Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
  // Make the IfNode
  IfNode* iff_c = iff->clone()->as_If();
  iff_c->set_req(0, region_c);
  iff_c->set_req(1, b_c);
  igvn->set_type_bottom(iff_c);
  igvn->_worklist.push(iff_c);
  hook->init_req(2, iff_c);

  IfNode* iff_x = iff->clone()->as_If();
  iff_x->set_req(0, region_x);
  iff_x->set_req(1, b_x);
  igvn->set_type_bottom(iff_x);
  igvn->_worklist.push(iff_x);
  hook->init_req(3, iff_x);

  // Make the true/false arms
  Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
  Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
  Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
  Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));

  // Merge the TRUE paths
  Node *region_s = new RegionNode(3);
  igvn->_worklist.push(region_s);
  region_s->init_req(1, iff_c_t);
  region_s->init_req(2, iff_x_t);
  igvn->register_new_node_with_optimizer( region_s );

  // Merge the FALSE paths
  Node *region_f = new RegionNode(3);
  igvn->_worklist.push(region_f);
  region_f->init_req(1, iff_c_f);
  region_f->init_req(2, iff_x_f);
  igvn->register_new_node_with_optimizer( region_f );

  igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
  cmp->set_req(1,nullptr);  // Whack the inputs to cmp because it will be dead
  cmp->set_req(2,nullptr);
  // Check for all uses of the Phi and give them a new home.
  // The 'cmp' got cloned, but CastPP/IIs need to be moved.
  Node *phi_s = nullptr;     // do not construct unless needed
  Node *phi_f = nullptr;     // do not construct unless needed
  for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
    Node* v = phi->last_out(i2);// User of the phi
    igvn->rehash_node_delayed(v); // Have to fixup other Phi users
    uint vop = v->Opcode();
    Node *proj = nullptr;
    if( vop == Op_Phi ) {       // Remote merge point
      Node *r = v->in(0);
      for (uint i3 = 1; i3 < r->req(); i3++)
        if (r->in(i3) && r->in(i3)->in(0) == iff) {
          proj = r->in(i3);
          break;
        }
    } else if( v->is_ConstraintCast() ) {
      proj = v->in(0);          // Controlling projection
    } else {
      assert( 0, "do not know how to handle this guy" );
    }
    guarantee(proj != nullptr, "sanity");

    Node *proj_path_data, *proj_path_ctrl;
    if( proj->Opcode() == Op_IfTrue ) {
      if( phi_s == nullptr ) {
        // Only construct phi_s if needed, otherwise provides
        // interfering use.
        phi_s = PhiNode::make_blank(region_s,phi);
        phi_s->init_req( 1, phi_c );
        phi_s->init_req( 2, phi_x );
        hook->add_req(phi_s);
        phi_s = phase->transform(phi_s);
      }
      proj_path_data = phi_s;
      proj_path_ctrl = region_s;
    } else {
      if( phi_f == nullptr ) {
        // Only construct phi_f if needed, otherwise provides
        // interfering use.
        phi_f = PhiNode::make_blank(region_f,phi);
        phi_f->init_req( 1, phi_c );
        phi_f->init_req( 2, phi_x );
        hook->add_req(phi_f);
        phi_f = phase->transform(phi_f);
      }
      proj_path_data = phi_f;
      proj_path_ctrl = region_f;
    }

    // Fixup 'v' for for the split
    if( vop == Op_Phi ) {       // Remote merge point
      uint i;
      for( i = 1; i < v->req(); i++ )
        if( v->in(i) == phi )
          break;
      v->set_req(i, proj_path_data );
    } else if( v->is_ConstraintCast() ) {
      v->set_req(0, proj_path_ctrl );
      v->set_req(1, proj_path_data );
    } else
      ShouldNotReachHere();
  }

  // Now replace the original iff's True/False with region_s/region_t.
  // This makes the original iff go dead.
  for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
    Node* p = iff->last_out(i3);
    assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
    Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
    // Replace p with u
    igvn->add_users_to_worklist(p);
    for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
      Node* x = p->last_out(l);
      igvn->hash_delete(x);
      uint uses_found = 0;
      for( uint j = 0; j < x->req(); j++ ) {
        if( x->in(j) == p ) {
          x->set_req(j, u);
          uses_found++;
        }
      }
      l -= uses_found;    // we deleted 1 or more copies of this edge
    }
    igvn->remove_dead_node(p);
  }

  // Force the original merge dead
  igvn->hash_delete(r);
  // First, remove region's dead users.
  for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
    Node* u = r->last_out(l);
    if( u == r ) {
      r->set_req(0, nullptr);
    } else {
      assert(u->outcnt() == 0, "only dead users");
      igvn->remove_dead_node(u);
    }
    l -= 1;
  }
  igvn->remove_dead_node(r);

  // Now remove the bogus extra edges used to keep things alive
  igvn->remove_dead_node( hook );

  // Must return either the original node (now dead) or a new node
  // (Do not return a top here, since that would break the uniqueness of top.)
  return new ConINode(TypeInt::ZERO);
}

IfNode* IfNode::make_with_same_profile(IfNode* if_node_profile, Node* ctrl, Node* bol) {
  // Assert here that we only try to create a clone from an If node with the same profiling if that actually makes sense.
  // Some If node subtypes should not be cloned in this way. In theory, we should not clone BaseCountedLoopEndNodes.
  // But they can end up being used as normal If nodes when peeling a loop - they serve as zero-trip guard.
  // Allow them as well.
  assert(if_node_profile->Opcode() == Op_If || if_node_profile->is_RangeCheck()
         || if_node_profile->is_BaseCountedLoopEnd(), "should not clone other nodes");
  if (if_node_profile->is_RangeCheck()) {
    // RangeCheck nodes could be further optimized.
    return new RangeCheckNode(ctrl, bol, if_node_profile->_prob, if_node_profile->_fcnt);
  } else {
    // Not a RangeCheckNode? Fall back to IfNode.
    return new IfNode(ctrl, bol, if_node_profile->_prob, if_node_profile->_fcnt);
  }
}

// if this IfNode follows a range check pattern return the projection
// for the failed path
ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
  if (outcnt() != 2) {
    return nullptr;
  }
  Node* b = in(1);
  if (b == nullptr || !b->is_Bool())  return nullptr;
  BoolNode* bn = b->as_Bool();
  Node* cmp = bn->in(1);
  if (cmp == nullptr)  return nullptr;
  if (cmp->Opcode() != Op_CmpU)  return nullptr;

  l = cmp->in(1);
  r = cmp->in(2);
  flip_test = 1;
  if (bn->_test._test == BoolTest::le) {
    l = cmp->in(2);
    r = cmp->in(1);
    flip_test = 2;
  } else if (bn->_test._test != BoolTest::lt) {
    return nullptr;
  }
  if (l->is_top())  return nullptr;   // Top input means dead test
  if (r->Opcode() != Op_LoadRange && !is_RangeCheck())  return nullptr;

  // We have recognized one of these forms:
  //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
  //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...

  ProjNode* iftrap = proj_out_or_null(flip_test == 2 ? true : false);
  return iftrap;
}


//------------------------------is_range_check---------------------------------
// Return 0 if not a range check.  Return 1 if a range check and set index and
// offset.  Return 2 if we had to negate the test.  Index is null if the check
// is versus a constant.
int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) {
  int flip_test = 0;
  Node* l = nullptr;
  Node* r = nullptr;
  ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);

  if (iftrap == nullptr) {
    return 0;
  }

  // Make sure it's a real range check by requiring an uncommon trap
  // along the OOB path.  Otherwise, it's possible that the user wrote
  // something which optimized to look like a range check but behaves
  // in some other way.
  if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == nullptr) {
    return 0;
  }

  // Look for index+offset form
  Node* ind = l;
  jint  off = 0;
  if (l->is_top()) {
    return 0;
  } else if (l->Opcode() == Op_AddI) {
    if ((off = l->in(1)->find_int_con(0)) != 0) {
      ind = l->in(2)->uncast();
    } else if ((off = l->in(2)->find_int_con(0)) != 0) {
      ind = l->in(1)->uncast();
    }
  } else if ((off = l->find_int_con(-1)) >= 0) {
    // constant offset with no variable index
    ind = nullptr;
  } else {
    // variable index with no constant offset (or dead negative index)
    off = 0;
  }

  // Return all the values:
  index  = ind;
  offset = off;
  range  = r;
  return flip_test;
}

//------------------------------adjust_check-----------------------------------
// Adjust (widen) a prior range check
static void adjust_check(IfProjNode* proj, Node* range, Node* index,
                         int flip, jint off_lo, PhaseIterGVN* igvn) {
  PhaseGVN *gvn = igvn;
  // Break apart the old check
  Node *iff = proj->in(0);
  Node *bol = iff->in(1);
  if( bol->is_top() ) return;   // In case a partially dead range check appears
  // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
  DEBUG_ONLY( if (!bol->is_Bool()) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
  if (!bol->is_Bool()) return;

  Node *cmp = bol->in(1);
  // Compute a new check
  Node *new_add = gvn->intcon(off_lo);
  if (index) {
    new_add = off_lo ? gvn->transform(new AddINode(index, new_add)) : index;
  }
  Node *new_cmp = (flip == 1)
    ? new CmpUNode(new_add, range)
    : new CmpUNode(range, new_add);
  new_cmp = gvn->transform(new_cmp);
  // See if no need to adjust the existing check
  if (new_cmp == cmp) return;
  // Else, adjust existing check
  Node* new_bol = gvn->transform(new BoolNode(new_cmp, bol->as_Bool()->_test._test));
  igvn->rehash_node_delayed(iff);
  iff->set_req_X(1, new_bol, igvn);
  // As part of range check smearing, this range check is widened. Loads and range check Cast nodes that are control
  // dependent on this range check now depend on multiple dominating range checks. These control dependent nodes end up
  // at the lowest/nearest dominating check in the graph. To ensure that these Loads/Casts do not float above any of the
  // dominating checks (even when the lowest dominating check is later replaced by yet another dominating check), we
  // need to pin them at the lowest dominating check.
  proj->pin_array_access_nodes(igvn);
}

//------------------------------up_one_dom-------------------------------------
// Walk up the dominator tree one step.  Return null at root or true
// complex merges.  Skips through small diamonds.
Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
  Node *dom = curr->in(0);
  if( !dom )                    // Found a Region degraded to a copy?
    return curr->nonnull_req(); // Skip thru it

  if( curr != dom )             // Normal walk up one step?
    return dom;

  // Use linear_only if we are still parsing, since we cannot
  // trust the regions to be fully filled in.
  if (linear_only)
    return nullptr;

  if( dom->is_Root() )
    return nullptr;

  // Else hit a Region.  Check for a loop header
  if( dom->is_Loop() )
    return dom->in(1);          // Skip up thru loops

  // Check for small diamonds
  Node *din1, *din2, *din3, *din4;
  if( dom->req() == 3 &&        // 2-path merge point
      (din1 = dom ->in(1)) &&   // Left  path exists
      (din2 = dom ->in(2)) &&   // Right path exists
      (din3 = din1->in(0)) &&   // Left  path up one
      (din4 = din2->in(0)) ) {  // Right path up one
    if( din3->is_Call() &&      // Handle a slow-path call on either arm
        (din3 = din3->in(0)) )
      din3 = din3->in(0);
    if( din4->is_Call() &&      // Handle a slow-path call on either arm
        (din4 = din4->in(0)) )
      din4 = din4->in(0);
    if (din3 != nullptr && din3 == din4 && din3->is_If()) // Regions not degraded to a copy
      return din3;              // Skip around diamonds
  }

  // Give up the search at true merges
  return nullptr;                  // Dead loop?  Or hit root?
}


//------------------------------filtered_int_type--------------------------------
// Return a possibly more restrictive type for val based on condition control flow for an if
const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node* val, Node* if_proj) {
  assert(if_proj &&
         (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
  if (if_proj->in(0) && if_proj->in(0)->is_If()) {
    IfNode* iff = if_proj->in(0)->as_If();
    if (iff->in(1) && iff->in(1)->is_Bool()) {
      BoolNode* bol = iff->in(1)->as_Bool();
      if (bol->in(1) && bol->in(1)->is_Cmp()) {
        const CmpNode* cmp  = bol->in(1)->as_Cmp();
        if (cmp->in(1) == val) {
          const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
          if (cmp2_t != nullptr) {
            jint lo = cmp2_t->_lo;
            jint hi = cmp2_t->_hi;
            BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
            switch (msk) {
            case BoolTest::ne: {
              // If val is compared to its lower or upper bound, we can narrow the type
              const TypeInt* val_t = gvn->type(val)->isa_int();
              if (val_t != nullptr && !val_t->singleton() && cmp2_t->is_con()) {
                if (val_t->_lo == lo) {
                  return TypeInt::make(val_t->_lo + 1, val_t->_hi, val_t->_widen);
                } else if (val_t->_hi == hi) {
                  return TypeInt::make(val_t->_lo, val_t->_hi - 1, val_t->_widen);
                }
              }
              // Can't refine type
              return nullptr;
            }
            case BoolTest::eq:
              return cmp2_t;
            case BoolTest::lt:
              lo = TypeInt::INT->_lo;
              if (hi != min_jint) {
                hi = hi - 1;
              }
              break;
            case BoolTest::le:
              lo = TypeInt::INT->_lo;
              break;
            case BoolTest::gt:
              if (lo != max_jint) {
                lo = lo + 1;
              }
              hi = TypeInt::INT->_hi;
              break;
            case BoolTest::ge:
              // lo unchanged
              hi = TypeInt::INT->_hi;
              break;
            default:
              break;
            }
            const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
            return rtn_t;
          }
        }
      }
    }
  }
  return nullptr;
}

//------------------------------fold_compares----------------------------
// See if a pair of CmpIs can be converted into a CmpU.  In some cases
// the direction of this if is determined by the preceding if so it
// can be eliminate entirely.
//
// Given an if testing (CmpI n v) check for an immediately control
// dependent if that is testing (CmpI n v2) and has one projection
// leading to this if and the other projection leading to a region
// that merges one of this ifs control projections.
//
//                   If
//                  / |
//                 /  |
//                /   |
//              If    |
//              /\    |
//             /  \   |
//            /    \  |
//           /    Region
//
// Or given an if testing (CmpI n v) check for a dominating if that is
// testing (CmpI n v2), both having one projection leading to an
// uncommon trap. Allow Another independent guard in between to cover
// an explicit range check:
// if (index < 0 || index >= array.length) {
// which may need a null check to guard the LoadRange
//
//                   If
//                  / \
//                 /   \
//                /     \
//              If      unc
//              /\
//             /  \
//            /    \
//           /      unc
//

// Is the comparison for this If suitable for folding?
bool IfNode::cmpi_folds(PhaseIterGVN* igvn, bool fold_ne) {
  return in(1) != nullptr &&
    in(1)->is_Bool() &&
    in(1)->in(1) != nullptr &&
    in(1)->in(1)->Opcode() == Op_CmpI &&
    in(1)->in(1)->in(2) != nullptr &&
    in(1)->in(1)->in(2) != igvn->C->top() &&
    (in(1)->as_Bool()->_test.is_less() ||
     in(1)->as_Bool()->_test.is_greater() ||
     (fold_ne && in(1)->as_Bool()->_test._test == BoolTest::ne));
}

// Is a dominating control suitable for folding with this if?
bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
  return ctrl != nullptr &&
    ctrl->is_Proj() &&
    ctrl->outcnt() == 1 && // No side-effects
    ctrl->in(0) != nullptr &&
    ctrl->in(0)->Opcode() == Op_If &&
    ctrl->in(0)->outcnt() == 2 &&
    ctrl->in(0)->as_If()->cmpi_folds(igvn, true) &&
    // Must compare same value
    ctrl->in(0)->in(1)->in(1)->in(1) != nullptr &&
    ctrl->in(0)->in(1)->in(1)->in(1) != igvn->C->top() &&
    ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
}

// Do this If and the dominating If share a region?
bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
  ProjNode* otherproj = proj->other_if_proj();
  Node* otherproj_ctrl_use = otherproj->unique_ctrl_out_or_null();
  RegionNode* region = (otherproj_ctrl_use != nullptr && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : nullptr;
  success = nullptr;
  fail = nullptr;

  if (otherproj->outcnt() == 1 && region != nullptr && !region->has_phi()) {
    for (int i = 0; i < 2; i++) {
      ProjNode* proj = proj_out(i);
      if (success == nullptr && proj->outcnt() == 1 && proj->unique_out() == region) {
        success = proj;
      } else if (fail == nullptr) {
        fail = proj;
      } else {
        success = fail = nullptr;
      }
    }
  }
  return success != nullptr && fail != nullptr;
}

bool IfNode::is_dominator_unc(CallStaticJavaNode* dom_unc, CallStaticJavaNode* unc) {
  // Different methods and methods containing jsrs are not supported.
  ciMethod* method = unc->jvms()->method();
  ciMethod* dom_method = dom_unc->jvms()->method();
  if (method != dom_method || method->has_jsrs()) {
    return false;
  }
  // Check that both traps are in the same activation of the method (instead
  // of two activations being inlined through different call sites) by verifying
  // that the call stacks are equal for both JVMStates.
  JVMState* dom_caller = dom_unc->jvms()->caller();
  JVMState* caller = unc->jvms()->caller();
  if ((dom_caller == nullptr) != (caller == nullptr)) {
    // The current method must either be inlined into both dom_caller and
    // caller or must not be inlined at all (top method). Bail out otherwise.
    return false;
  } else if (dom_caller != nullptr && !dom_caller->same_calls_as(caller)) {
    return false;
  }
  // Check that the bci of the dominating uncommon trap dominates the bci
  // of the dominated uncommon trap. Otherwise we may not re-execute
  // the dominated check after deoptimization from the merged uncommon trap.
  ciTypeFlow* flow = dom_method->get_flow_analysis();
  int bci = unc->jvms()->bci();
  int dom_bci = dom_unc->jvms()->bci();
  if (!flow->is_dominated_by(bci, dom_bci)) {
    return false;
  }

  return true;
}

// Return projection that leads to an uncommon trap if any
ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call, Deoptimization::DeoptReason reason) const {
  for (int i = 0; i < 2; i++) {
    call = proj_out(i)->is_uncommon_trap_proj(reason);
    if (call != nullptr) {
      return proj_out(i);
    }
  }
  return nullptr;
}

// Do this If and the dominating If both branch out to an uncommon trap
bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
  ProjNode* otherproj = proj->other_if_proj();
  CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj();

  if (otherproj->outcnt() == 1 && dom_unc != nullptr) {
    // We need to re-execute the folded Ifs after deoptimization from the merged traps
    if (!dom_unc->jvms()->should_reexecute()) {
      return false;
    }

    CallStaticJavaNode* unc = nullptr;
    ProjNode* unc_proj = uncommon_trap_proj(unc);
    if (unc_proj != nullptr && unc_proj->outcnt() == 1) {
      if (dom_unc == unc) {
        // Allow the uncommon trap to be shared through a region
        RegionNode* r = unc->in(0)->as_Region();
        if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
          return false;
        }
        assert(r->has_phi() == nullptr, "simple region shouldn't have a phi");
      } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
        return false;
      }

      if (!is_dominator_unc(dom_unc, unc)) {
        return false;
      }

      // See merge_uncommon_traps: the reason of the uncommon trap
      // will be changed and the state of the dominating If will be
      // used. Checked that we didn't apply this transformation in a
      // previous compilation and it didn't cause too many traps
      ciMethod* dom_method = dom_unc->jvms()->method();
      int dom_bci = dom_unc->jvms()->bci();
      if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
          !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check) &&
          // Return true if c2 manages to reconcile with UnstableIf optimization. See the comments for it.
          igvn->C->remove_unstable_if_trap(dom_unc, true/*yield*/)) {
        success = unc_proj;
        fail = unc_proj->other_if_proj();
        return true;
      }
    }
  }
  return false;
}

// Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
  Node* this_cmp = in(1)->in(1);
  BoolNode* this_bool = in(1)->as_Bool();
  IfNode* dom_iff = proj->in(0)->as_If();
  BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
  Node* lo = dom_iff->in(1)->in(1)->in(2);
  Node* hi = this_cmp->in(2);
  Node* n = this_cmp->in(1);
  ProjNode* otherproj = proj->other_if_proj();

  const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
  const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);

  BoolTest::mask lo_test = dom_bool->_test._test;
  BoolTest::mask hi_test = this_bool->_test._test;
  BoolTest::mask cond = hi_test;

  // convert:
  //
  //          dom_bool = x {<,<=,>,>=} a
  //                           / \
  //     proj = {True,False}  /   \ otherproj = {False,True}
  //                         /
  //        this_bool = x {<,<=} b
  //                       / \
  //  fail = {True,False} /   \ success = {False,True}
  //                     /
  //
  // (Second test guaranteed canonicalized, first one may not have
  // been canonicalized yet)
  //
  // into:
  //
  // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
  //                       / \
  //                 fail /   \ success
  //                     /
  //

  // Figure out which of the two tests sets the upper bound and which
  // sets the lower bound if any.
  Node* adjusted_lim = nullptr;
  if (lo_type != nullptr && hi_type != nullptr && hi_type->_lo > lo_type->_hi &&
      hi_type->_hi == max_jint && lo_type->_lo == min_jint && lo_test != BoolTest::ne) {
    assert((dom_bool->_test.is_less() && !proj->_con) ||
           (dom_bool->_test.is_greater() && proj->_con), "incorrect test");

    // this_bool = <
    //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
    //     x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
    //     lo = a, hi = b, adjusted_lim = b-a, cond = <u
    //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
    //     x in ]a, b[ on the fail (= True) projection, b > a:
    //     lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
    // this_bool = <=
    //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
    //     x in [a, b] on the fail (= True) projection, b+1 > a-1:
    //     lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
    //     lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
    //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
    //     x in ]a, b] on the fail (= True) projection b+1 > a:
    //     lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
    //     lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <=u doesn't work because a = b is possible, then b-a-1 = -1

    if (hi_test == BoolTest::lt) {
      if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
        lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
      }
    } else if (hi_test == BoolTest::le) {
      if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
        adjusted_lim = igvn->transform(new SubINode(hi, lo));
        adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
        cond = BoolTest::lt;
      } else if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
        adjusted_lim = igvn->transform(new SubINode(hi, lo));
        lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
        cond = BoolTest::lt;
      } else {
        assert(false, "unhandled lo_test: %d", lo_test);
        return false;
      }
    } else {
      assert(igvn->_worklist.member(in(1)) && in(1)->Value(igvn) != igvn->type(in(1)), "unhandled hi_test: %d", hi_test);
      return false;
    }
    // this test was canonicalized
    assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
  } else if (lo_type != nullptr && hi_type != nullptr && lo_type->_lo > hi_type->_hi &&
             lo_type->_hi == max_jint && hi_type->_lo == min_jint && lo_test != BoolTest::ne) {

    // this_bool = <
    //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
    //     x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
    //     lo = b, hi = a, adjusted_lim = a-b, cond = >=u
    //   dom_bool = <= (proj = True) or dom_bool = > (proj = False)
    //     x in [b, a] on the fail (= False) projection, a+1 > b-1:
    //     lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
    //     lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
    // this_bool = <=
    //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
    //     x in ]b, a[ on the fail (= False) projection, a > b:
    //     lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u