diff src/share/vm/opto/ifnode.cpp @ 0:a61af66fc99e

Initial load
author duke
date Sat, 01 Dec 2007 00:00:00 +0000
parents
children ff5961f4c095
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/opto/ifnode.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,922 @@
+/*
+ * Copyright 2000-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// Portions of code courtesy of Clifford Click
+
+// Optimization - Graph Style
+
+#include "incls/_precompiled.incl"
+#include "incls/_ifnode.cpp.incl"
+
+
+extern int explicit_null_checks_elided;
+
+//=============================================================================
+//------------------------------Value------------------------------------------
+// Return a tuple for whichever arm of the IF is reachable
+const Type *IfNode::Value( PhaseTransform *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 NULL;
+  BoolNode *b = i1->as_Bool();
+  Node *cmp = b->in(1);
+  if( !cmp->is_Cmp() ) return NULL;
+  i1 = cmp->in(1);
+  if( i1 == NULL || !i1->is_Phi() ) return NULL;
+  PhiNode *phi = i1->as_Phi();
+  if( phi->is_copy() ) return NULL;
+  Node *con2 = cmp->in(2);
+  if( !con2->is_Con() ) return NULL;
+  // See that the merge point contains some constants
+  Node *con1=NULL;
+  uint i4;
+  for( i4 = 1; i4 < phi->req(); i4++ ) {
+    con1 = phi->in(i4);
+    if( !con1 ) return NULL;    // Do not optimize partially collaped merges
+    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 NULL; // 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 NULL;
+
+  // No intervening control, like a simple Call
+  Node *r = iff->in(0);
+  if( !r->is_Region() ) return NULL;
+  if( phi->region() != r ) return NULL;
+  // No other users of the cmp/bool
+  if (b->outcnt() != 1 || cmp->outcnt() != 1) {
+    //tty->print_cr("many users of cmp/bool");
+    return NULL;
+  }
+
+  // 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 NULL;
+    }
+    if( u != phi ) {
+      // CNC - do not allow any other merged value
+      //tty->print_cr("Merging another value");
+      //u->dump(2);
+      return NULL;
+    }
+    // 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()) &&
+          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 NULL;   // 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 cant be bothered with");
+        }
+        */
+      }
+      return NULL;
+
+      /* 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 NULL;
+      }
+      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 NULL;
+        } // 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 NULL;
+
+  // 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 seperate 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++;
+    }
+  }
+  Node *region_c = new (igvn->C, req_c + 1) RegionNode(req_c + 1);
+  Node *phi_c    = con1;
+  uint  len      = r->req();
+  Node *region_x = new (igvn->C, len - req_c + 1) RegionNode(len - req_c + 1);
+  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 conglerate has been hacked
+  // as a single huge transform.
+  igvn->register_new_node_with_optimizer( region_c );
+  igvn->register_new_node_with_optimizer( region_x );
+  phi_x = phase->transform( phi_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 (igvn->C, 4) Node(4);
+  hook->init_req(0, phi_x);
+  hook->init_req(1, phi_c);
+
+  // 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 (igvn->C, 2) BoolNode(cmp_c,b->_test._test));
+  Node *b_x = phase->transform(new (igvn->C, 2) BoolNode(cmp_x,b->_test._test));
+  // Make the IfNode
+  IfNode *iff_c = new (igvn->C, 2) IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
+  igvn->set_type_bottom(iff_c);
+  igvn->_worklist.push(iff_c);
+  hook->init_req(2, iff_c);
+
+  IfNode *iff_x = new (igvn->C, 2) IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
+  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 (igvn->C, 1) IfTrueNode (iff_c));
+  Node *iff_c_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_c));
+  Node *iff_x_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_x));
+  Node *iff_x_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_x));
+
+  // Merge the TRUE paths
+  Node *region_s = new (igvn->C, 3) 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 (igvn->C, 3) 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,NULL);  // Whack the inputs to cmp because it will be dead
+  cmp->set_req(2,NULL);
+  // 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 = NULL;     // do not construct unless needed
+  Node *phi_f = NULL;     // 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->hash_delete(v);       // Have to fixup other Phi users
+    igvn->_worklist.push(v);
+    uint vop = v->Opcode();
+    Node *proj = NULL;
+    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" );
+    }
+
+    Node *proj_path_data, *proj_path_ctrl;
+    if( proj->Opcode() == Op_IfTrue ) {
+      if( phi_s == NULL ) {
+        // 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 );
+        phi_s = phase->transform(phi_s);
+      }
+      proj_path_data = phi_s;
+      proj_path_ctrl = region_s;
+    } else {
+      if( phi_f == NULL ) {
+        // 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 );
+        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);
+  r->set_req_X(0,NULL,igvn);
+
+  // 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 (igvn->C, 1) ConINode(TypeInt::ZERO);
+}
+
+//------------------------------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 IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
+  Node* b = in(1);
+  if (b == NULL || !b->is_Bool())  return 0;
+  BoolNode* bn = b->as_Bool();
+  Node* cmp = bn->in(1);
+  if (cmp == NULL)  return 0;
+  if (cmp->Opcode() != Op_CmpU)  return 0;
+
+  Node* l = cmp->in(1);
+  Node* r = cmp->in(2);
+  int 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 0;
+  }
+  if (l->is_top())  return 0;   // Top input means dead test
+  if (r->Opcode() != Op_LoadRange)  return 0;
+
+  // We have recognized one of these forms:
+  //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
+  //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...
+
+  // 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.
+  Node* iftrap = proj_out(flip_test == 2 ? true : false);
+  bool found_trap = false;
+  if (iftrap != NULL) {
+    Node* u = iftrap->unique_ctrl_out();
+    if (u != NULL) {
+      // It could be a merge point (Region) for uncommon trap.
+      if (u->is_Region()) {
+        Node* c = u->unique_ctrl_out();
+        if (c != NULL) {
+          iftrap = u;
+          u = c;
+        }
+      }
+      if (u->in(0) == iftrap && u->is_CallStaticJava()) {
+        int req = u->as_CallStaticJava()->uncommon_trap_request();
+        if (Deoptimization::trap_request_reason(req) ==
+            Deoptimization::Reason_range_check) {
+          found_trap = true;
+        }
+      }
+    }
+  }
+  if (!found_trap)  return 0;   // sorry, no cigar
+
+  // Look for index+offset form
+  Node* ind = l;
+  jint  off = 0;
+  if (l->is_top()) {
+    return 0;
+  } else if (l->is_Add()) {
+    if ((off = l->in(1)->find_int_con(0)) != 0) {
+      ind = l->in(2);
+    } else if ((off = l->in(2)->find_int_con(0)) != 0) {
+      ind = l->in(1);
+    }
+  } else if ((off = l->find_int_con(-1)) >= 0) {
+    // constant offset with no variable index
+    ind = NULL;
+  } 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(Node* 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 (gvn->C, 3) AddINode( index, new_add )) : index;
+  }
+  Node *new_cmp = (flip == 1)
+    ? new (gvn->C, 3) CmpUNode( new_add, range )
+    : new (gvn->C, 3) 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 (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
+  igvn->hash_delete( iff );
+  iff->set_req_X( 1, new_bol, 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 NULL;
+
+  // 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 == din4 && din3->is_If() )
+      return din3;              // Skip around diamonds
+  }
+
+  // Give up the search at true merges
+  return NULL;                  // Dead loop?  Or hit root?
+}
+
+//------------------------------remove_useless_bool----------------------------
+// Check for people making a useless boolean: things like
+// if( (x < y ? true : false) ) { ... }
+// Replace with if( x < y ) { ... }
+static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
+  Node *i1 = iff->in(1);
+  if( !i1->is_Bool() ) return NULL;
+  BoolNode *bol = i1->as_Bool();
+
+  Node *cmp = bol->in(1);
+  if( cmp->Opcode() != Op_CmpI ) return NULL;
+
+  // Must be comparing against a bool
+  const Type *cmp2_t = phase->type( cmp->in(2) );
+  if( cmp2_t != TypeInt::ZERO &&
+      cmp2_t != TypeInt::ONE )
+    return NULL;
+
+  // Find a prior merge point merging the boolean
+  i1 = cmp->in(1);
+  if( !i1->is_Phi() ) return NULL;
+  PhiNode *phi = i1->as_Phi();
+  if( phase->type( phi ) != TypeInt::BOOL )
+    return NULL;
+
+  // Check for diamond pattern
+  int true_path = phi->is_diamond_phi();
+  if( true_path == 0 ) return NULL;
+
+  // phi->region->if_proj->ifnode->bool->cmp
+  BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
+
+  // Now get the 'sense' of the test correct so we can plug in
+  // either iff2->in(1) or its complement.
+  int flip = 0;
+  if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
+  else if( bol->_test._test != BoolTest::eq ) return NULL;
+  if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
+
+  const Type *phi1_t = phase->type( phi->in(1) );
+  const Type *phi2_t = phase->type( phi->in(2) );
+  // Check for Phi(0,1) and flip
+  if( phi1_t == TypeInt::ZERO ) {
+    if( phi2_t != TypeInt::ONE ) return NULL;
+    flip = 1-flip;
+  } else {
+    // Check for Phi(1,0)
+    if( phi1_t != TypeInt::ONE  ) return NULL;
+    if( phi2_t != TypeInt::ZERO ) return NULL;
+  }
+  if( true_path == 2 ) {
+    flip = 1-flip;
+  }
+
+  Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
+  iff->set_req(1, new_bol);
+  // Intervening diamond probably goes dead
+  phase->C->set_major_progress();
+  return iff;
+}
+
+static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
+
+//------------------------------Ideal------------------------------------------
+// Return a node which is more "ideal" than the current node.  Strip out
+// control copies
+Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
+  if (remove_dead_region(phase, can_reshape))  return this;
+  // No Def-Use info?
+  if (!can_reshape)  return NULL;
+  PhaseIterGVN *igvn = phase->is_IterGVN();
+
+  // Don't bother trying to transform a dead if
+  if (in(0)->is_top())  return NULL;
+  // Don't bother trying to transform an if with a dead test
+  if (in(1)->is_top())  return NULL;
+  // Another variation of a dead test
+  if (in(1)->is_Con())  return NULL;
+  // Another variation of a dead if
+  if (outcnt() < 2)  return NULL;
+
+  // Canonicalize the test.
+  Node* idt_if = idealize_test(phase, this);
+  if (idt_if != NULL)  return idt_if;
+
+  // Try to split the IF
+  Node *s = split_if(this, igvn);
+  if (s != NULL)  return s;
+
+  // Check for people making a useless boolean: things like
+  // if( (x < y ? true : false) ) { ... }
+  // Replace with if( x < y ) { ... }
+  Node *bol2 = remove_useless_bool(this, phase);
+  if( bol2 ) return bol2;
+
+  // Setup to scan up the CFG looking for a dominating test
+  Node *dom = in(0);
+  Node *prev_dom = this;
+
+  // Check for range-check vs other kinds of tests
+  Node *index1, *range1;
+  jint offset1;
+  int flip1 = is_range_check(range1, index1, offset1);
+  if( flip1 ) {
+    Node *first_prev_dom = NULL;
+
+    // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
+    // so all checks we inspect post-dominate the top-most check we find.
+    // If we are going to fail the current check and we reach the top check
+    // then we are guarenteed to fail, so just start interpreting there.
+    // We 'expand' the top 2 range checks to include all post-dominating
+    // checks.
+
+    // The top 2 range checks seen
+    Node *prev_chk1 = NULL;
+    Node *prev_chk2 = NULL;
+    // Low and high offsets seen so far
+    jint off_lo = offset1;
+    jint off_hi = offset1;
+
+    // Scan for the top 2 checks and collect range of offsets
+    for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit
+      if( dom->Opcode() == Op_If &&  // Not same opcode?
+          prev_dom->in(0) == dom ) { // One path of test does dominate?
+        if( dom == this ) return NULL; // dead loop
+        // See if this is a range check
+        Node *index2, *range2;
+        jint offset2;
+        int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
+        // See if this is a _matching_ range check, checking against
+        // the same array bounds.
+        if( flip2 == flip1 && range2 == range1 && index2 == index1 &&
+            dom->outcnt() == 2 ) {
+          // Gather expanded bounds
+          off_lo = MIN2(off_lo,offset2);
+          off_hi = MAX2(off_hi,offset2);
+          // Record top 2 range checks
+          prev_chk2 = prev_chk1;
+          prev_chk1 = prev_dom;
+          // If we match the test exactly, then the top test covers
+          // both our lower and upper bounds.
+          if( dom->in(1) == in(1) )
+            prev_chk2 = prev_chk1;
+        }
+      }
+      prev_dom = dom;
+      dom = up_one_dom( dom );
+      if( !dom ) break;
+    }
+
+
+    // Attempt to widen the dominating range check to cover some later
+    // ones.  Since range checks "fail" by uncommon-trapping to the
+    // interpreter, widening a check can make us speculative enter the
+    // interpreter.  If we see range-check deopt's, do not widen!
+    if (!phase->C->allow_range_check_smearing())  return NULL;
+
+    // Constant indices only need to check the upper bound.
+    // Non-constance indices must check both low and high.
+    if( index1 ) {
+      // Didn't find 2 prior covering checks, so cannot remove anything.
+      if( !prev_chk2 ) return NULL;
+      // 'Widen' the offsets of the 1st and 2nd covering check
+      adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn );
+      // Do not call adjust_check twice on the same projection
+      // as the first call may have transformed the BoolNode to a ConI
+      if( prev_chk1 != prev_chk2 ) {
+        adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn );
+      }
+      // Test is now covered by prior checks, dominate it out
+      prev_dom = prev_chk2;
+    } else {
+      // Didn't find prior covering check, so cannot remove anything.
+      if( !prev_chk1 ) return NULL;
+      // 'Widen' the offset of the 1st and only covering check
+      adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn );
+      // Test is now covered by prior checks, dominate it out
+      prev_dom = prev_chk1;
+    }
+
+
+  } else {                      // Scan for an equivalent test
+
+    Node *cmp;
+    int dist = 0;               // Cutoff limit for search
+    int op = Opcode();
+    if( op == Op_If &&
+        (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
+      if( cmp->in(2) != NULL && // make sure cmp is not already dead
+          cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
+        dist = 64;              // Limit for null-pointer scans
+      } else {
+        dist = 4;               // Do not bother for random pointer tests
+      }
+    } else {
+      dist = 4;                 // Limit for random junky scans
+    }
+
+    // Normal equivalent-test check.
+    if( !dom ) return NULL;     // Dead loop?
+
+    // Search up the dominator tree for an If with an identical test
+    while( dom->Opcode() != op    ||  // Not same opcode?
+           dom->in(1)    != in(1) ||  // Not same input 1?
+           (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
+           prev_dom->in(0) != dom ) { // One path of test does not dominate?
+      if( dist < 0 ) return NULL;
+
+      dist--;
+      prev_dom = dom;
+      dom = up_one_dom( dom );
+      if( !dom ) return NULL;
+    }
+
+    // Check that we did not follow a loop back to ourselves
+    if( this == dom )
+      return NULL;
+
+    if( dist > 2 )              // Add to count of NULL checks elided
+      explicit_null_checks_elided++;
+
+  } // End of Else scan for an equivalent test
+
+  // Hit!  Remove this IF
+#ifndef PRODUCT
+  if( TraceIterativeGVN ) {
+    tty->print("   Removing IfNode: "); this->dump();
+  }
+  if( VerifyOpto && !phase->allow_progress() ) {
+    // Found an equivalent dominating test,
+    // we can not guarantee reaching a fix-point for these during iterativeGVN
+    // since intervening nodes may not change.
+    return NULL;
+  }
+#endif
+
+  // Replace dominated IfNode
+  dominated_by( prev_dom, igvn );
+
+  // 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 (phase->C, 1) ConINode(TypeInt::ZERO);
+}
+
+//------------------------------dominated_by-----------------------------------
+void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
+  igvn->hash_delete(this);      // Remove self to prevent spurious V-N
+  Node *idom = in(0);
+  // Need opcode to decide which way 'this' test goes
+  int prev_op = prev_dom->Opcode();
+  Node *top = igvn->C->top(); // Shortcut to top
+
+  // Now walk the current IfNode's projections.
+  // Loop ends when 'this' has no more uses.
+  for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
+    Node *ifp = last_out(i);     // Get IfTrue/IfFalse
+    igvn->add_users_to_worklist(ifp);
+    // Check which projection it is and set target.
+    // Data-target is either the dominating projection of the same type
+    // or TOP if the dominating projection is of opposite type.
+    // Data-target will be used as the new control edge for the non-CFG
+    // nodes like Casts and Loads.
+    Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top;
+    // Control-target is just the If's immediate dominator or TOP.
+    Node *ctrl_target = (ifp->Opcode() == prev_op ) ?     idom : top;
+
+    // For each child of an IfTrue/IfFalse projection, reroute.
+    // Loop ends when projection has no more uses.
+    for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
+      Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
+      igvn->hash_delete(s);         // Yank from hash table before edge hacking
+      if( !s->depends_only_on_test() ) {
+        // Find the control input matching this def-use edge.
+        // For Regions it may not be in slot 0.
+        uint l;
+        for( l = 0; s->in(l) != ifp; l++ ) { }
+        s->set_req(l, ctrl_target);
+      } else {                      // Else, for control producers,
+        s->set_req(0, data_target); // Move child to data-target
+      }
+      igvn->_worklist.push(s);  // Revisit collapsed Phis
+    } // End for each child of a projection
+
+    igvn->remove_dead_node(ifp);
+  } // End for each IfTrue/IfFalse child of If
+
+  // Kill the IfNode
+  igvn->remove_dead_node(this);
+}
+
+//------------------------------Identity---------------------------------------
+// If the test is constant & we match, then we are the input Control
+Node *IfTrueNode::Identity( PhaseTransform *phase ) {
+  // Can only optimize if cannot go the other way
+  const TypeTuple *t = phase->type(in(0))->is_tuple();
+  return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
+    ? in(0)->in(0)              // IfNode control
+    : this;                     // no progress
+}
+
+//------------------------------dump_spec--------------------------------------
+#ifndef PRODUCT
+void IfNode::dump_spec(outputStream *st) const {
+  st->print("P=%f, C=%f",_prob,_fcnt);
+}
+#endif
+
+//------------------------------idealize_test----------------------------------
+// Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
+// come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
+// converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
+// needed.
+static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
+  assert(iff->in(0) != NULL, "If must be live");
+
+  if (iff->outcnt() != 2)  return NULL; // Malformed projections.
+  Node* old_if_f = iff->proj_out(false);
+  Node* old_if_t = iff->proj_out(true);
+
+  // CountedLoopEnds want the back-control test to be TRUE, irregardless of
+  // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
+  // happens in count-down loops
+  if (iff->is_CountedLoopEnd())  return NULL;
+  if (!iff->in(1)->is_Bool())  return NULL; // Happens for partially optimized IF tests
+  BoolNode *b = iff->in(1)->as_Bool();
+  BoolTest bt = b->_test;
+  // Test already in good order?
+  if( bt.is_canonical() )
+    return NULL;
+
+  // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
+  // cloning the IfNode.
+  Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) );
+  if( !new_b->is_Bool() ) return NULL;
+  b = new_b->as_Bool();
+
+  PhaseIterGVN *igvn = phase->is_IterGVN();
+  assert( igvn, "Test is not canonical in parser?" );
+
+  // The IF node never really changes, but it needs to be cloned
+  iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
+
+  Node *prior = igvn->hash_find_insert(iff);
+  if( prior ) {
+    igvn->remove_dead_node(iff);
+    iff = (IfNode*)prior;
+  } else {
+    // Cannot call transform on it just yet
+    igvn->set_type_bottom(iff);
+  }
+  igvn->_worklist.push(iff);
+
+  // Now handle projections.  Cloning not required.
+  Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff ));
+  Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff ));
+
+  igvn->register_new_node_with_optimizer(new_if_f);
+  igvn->register_new_node_with_optimizer(new_if_t);
+  igvn->hash_delete(old_if_f);
+  igvn->hash_delete(old_if_t);
+  // Flip test, so flip trailing control
+  igvn->subsume_node(old_if_f, new_if_t);
+  igvn->subsume_node(old_if_t, new_if_f);
+
+  // Progress
+  return iff;
+}
+
+//------------------------------Identity---------------------------------------
+// If the test is constant & we match, then we are the input Control
+Node *IfFalseNode::Identity( PhaseTransform *phase ) {
+  // Can only optimize if cannot go the other way
+  const TypeTuple *t = phase->type(in(0))->is_tuple();
+  return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
+    ? in(0)->in(0)              // IfNode control
+    : this;                     // no progress
+}