1 /*
   2  * Copyright 2000-2009 Sun Microsystems, Inc.  All Rights Reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 #include "incls/_precompiled.incl"
  26 #include "incls/_loopTransform.cpp.incl"
  27 
  28 //------------------------------is_loop_exit-----------------------------------
  29 // Given an IfNode, return the loop-exiting projection or NULL if both
  30 // arms remain in the loop.
  31 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
  32   if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
  33   PhaseIdealLoop *phase = _phase;
  34   // Test is an IfNode, has 2 projections.  If BOTH are in the loop
  35   // we need loop unswitching instead of peeling.
  36   if( !is_member(phase->get_loop( iff->raw_out(0) )) )
  37     return iff->raw_out(0);
  38   if( !is_member(phase->get_loop( iff->raw_out(1) )) )
  39     return iff->raw_out(1);
  40   return NULL;
  41 }
  42 
  43 
  44 //=============================================================================
  45 
  46 
  47 //------------------------------record_for_igvn----------------------------
  48 // Put loop body on igvn work list
  49 void IdealLoopTree::record_for_igvn() {
  50   for( uint i = 0; i < _body.size(); i++ ) {
  51     Node *n = _body.at(i);
  52     _phase->_igvn._worklist.push(n);
  53   }
  54 }
  55 
  56 //------------------------------compute_profile_trip_cnt----------------------------
  57 // Compute loop trip count from profile data as
  58 //    (backedge_count + loop_exit_count) / loop_exit_count
  59 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
  60   if (!_head->is_CountedLoop()) {
  61     return;
  62   }
  63   CountedLoopNode* head = _head->as_CountedLoop();
  64   if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
  65     return; // Already computed
  66   }
  67   float trip_cnt = (float)max_jint; // default is big
  68 
  69   Node* back = head->in(LoopNode::LoopBackControl);
  70   while (back != head) {
  71     if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
  72         back->in(0) &&
  73         back->in(0)->is_If() &&
  74         back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
  75         back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
  76       break;
  77     }
  78     back = phase->idom(back);
  79   }
  80   if (back != head) {
  81     assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
  82            back->in(0), "if-projection exists");
  83     IfNode* back_if = back->in(0)->as_If();
  84     float loop_back_cnt = back_if->_fcnt * back_if->_prob;
  85 
  86     // Now compute a loop exit count
  87     float loop_exit_cnt = 0.0f;
  88     for( uint i = 0; i < _body.size(); i++ ) {
  89       Node *n = _body[i];
  90       if( n->is_If() ) {
  91         IfNode *iff = n->as_If();
  92         if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
  93           Node *exit = is_loop_exit(iff);
  94           if( exit ) {
  95             float exit_prob = iff->_prob;
  96             if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
  97             if (exit_prob > PROB_MIN) {
  98               float exit_cnt = iff->_fcnt * exit_prob;
  99               loop_exit_cnt += exit_cnt;
 100             }
 101           }
 102         }
 103       }
 104     }
 105     if (loop_exit_cnt > 0.0f) {
 106       trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
 107     } else {
 108       // No exit count so use
 109       trip_cnt = loop_back_cnt;
 110     }
 111   }
 112 #ifndef PRODUCT
 113   if (TraceProfileTripCount) {
 114     tty->print_cr("compute_profile_trip_cnt  lp: %d cnt: %f\n", head->_idx, trip_cnt);
 115   }
 116 #endif
 117   head->set_profile_trip_cnt(trip_cnt);
 118 }
 119 
 120 //---------------------is_invariant_addition-----------------------------
 121 // Return nonzero index of invariant operand for an Add or Sub
 122 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
 123 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
 124   int op = n->Opcode();
 125   if (op == Op_AddI || op == Op_SubI) {
 126     bool in1_invar = this->is_invariant(n->in(1));
 127     bool in2_invar = this->is_invariant(n->in(2));
 128     if (in1_invar && !in2_invar) return 1;
 129     if (!in1_invar && in2_invar) return 2;
 130   }
 131   return 0;
 132 }
 133 
 134 //---------------------reassociate_add_sub-----------------------------
 135 // Reassociate invariant add and subtract expressions:
 136 //
 137 // inv1 + (x + inv2)  =>  ( inv1 + inv2) + x
 138 // (x + inv2) + inv1  =>  ( inv1 + inv2) + x
 139 // inv1 + (x - inv2)  =>  ( inv1 - inv2) + x
 140 // inv1 - (inv2 - x)  =>  ( inv1 - inv2) + x
 141 // (x + inv2) - inv1  =>  (-inv1 + inv2) + x
 142 // (x - inv2) + inv1  =>  ( inv1 - inv2) + x
 143 // (x - inv2) - inv1  =>  (-inv1 - inv2) + x
 144 // inv1 + (inv2 - x)  =>  ( inv1 + inv2) - x
 145 // inv1 - (x - inv2)  =>  ( inv1 + inv2) - x
 146 // (inv2 - x) + inv1  =>  ( inv1 + inv2) - x
 147 // (inv2 - x) - inv1  =>  (-inv1 + inv2) - x
 148 // inv1 - (x + inv2)  =>  ( inv1 - inv2) - x
 149 //
 150 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
 151   if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
 152   if (is_invariant(n1)) return NULL;
 153   int inv1_idx = is_invariant_addition(n1, phase);
 154   if (!inv1_idx) return NULL;
 155   // Don't mess with add of constant (igvn moves them to expression tree root.)
 156   if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
 157   Node* inv1 = n1->in(inv1_idx);
 158   Node* n2 = n1->in(3 - inv1_idx);
 159   int inv2_idx = is_invariant_addition(n2, phase);
 160   if (!inv2_idx) return NULL;
 161   Node* x    = n2->in(3 - inv2_idx);
 162   Node* inv2 = n2->in(inv2_idx);
 163 
 164   bool neg_x    = n2->is_Sub() && inv2_idx == 1;
 165   bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
 166   bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
 167   if (n1->is_Sub() && inv1_idx == 1) {
 168     neg_x    = !neg_x;
 169     neg_inv2 = !neg_inv2;
 170   }
 171   Node* inv1_c = phase->get_ctrl(inv1);
 172   Node* inv2_c = phase->get_ctrl(inv2);
 173   Node* n_inv1;
 174   if (neg_inv1) {
 175     Node *zero = phase->_igvn.intcon(0);
 176     phase->set_ctrl(zero, phase->C->root());
 177     n_inv1 = new (phase->C, 3) SubINode(zero, inv1);
 178     phase->register_new_node(n_inv1, inv1_c);
 179   } else {
 180     n_inv1 = inv1;
 181   }
 182   Node* inv;
 183   if (neg_inv2) {
 184     inv = new (phase->C, 3) SubINode(n_inv1, inv2);
 185   } else {
 186     inv = new (phase->C, 3) AddINode(n_inv1, inv2);
 187   }
 188   phase->register_new_node(inv, phase->get_early_ctrl(inv));
 189 
 190   Node* addx;
 191   if (neg_x) {
 192     addx = new (phase->C, 3) SubINode(inv, x);
 193   } else {
 194     addx = new (phase->C, 3) AddINode(x, inv);
 195   }
 196   phase->register_new_node(addx, phase->get_ctrl(x));
 197   phase->_igvn.hash_delete(n1);
 198   phase->_igvn.subsume_node(n1, addx);
 199   return addx;
 200 }
 201 
 202 //---------------------reassociate_invariants-----------------------------
 203 // Reassociate invariant expressions:
 204 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
 205   for (int i = _body.size() - 1; i >= 0; i--) {
 206     Node *n = _body.at(i);
 207     for (int j = 0; j < 5; j++) {
 208       Node* nn = reassociate_add_sub(n, phase);
 209       if (nn == NULL) break;
 210       n = nn; // again
 211     };
 212   }
 213 }
 214 
 215 //------------------------------policy_peeling---------------------------------
 216 // Return TRUE or FALSE if the loop should be peeled or not.  Peel if we can
 217 // make some loop-invariant test (usually a null-check) happen before the loop.
 218 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
 219   Node *test = ((IdealLoopTree*)this)->tail();
 220   int  body_size = ((IdealLoopTree*)this)->_body.size();
 221   int  uniq      = phase->C->unique();
 222   // Peeling does loop cloning which can result in O(N^2) node construction
 223   if( body_size > 255 /* Prevent overflow for large body_size */
 224       || (body_size * body_size + uniq > MaxNodeLimit) ) {
 225     return false;           // too large to safely clone
 226   }
 227   while( test != _head ) {      // Scan till run off top of loop
 228     if( test->is_If() ) {       // Test?
 229       Node *ctrl = phase->get_ctrl(test->in(1));
 230       if (ctrl->is_top())
 231         return false;           // Found dead test on live IF?  No peeling!
 232       // Standard IF only has one input value to check for loop invariance
 233       assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
 234       // Condition is not a member of this loop?
 235       if( !is_member(phase->get_loop(ctrl)) &&
 236           is_loop_exit(test) )
 237         return true;            // Found reason to peel!
 238     }
 239     // Walk up dominators to loop _head looking for test which is
 240     // executed on every path thru loop.
 241     test = phase->idom(test);
 242   }
 243   return false;
 244 }
 245 
 246 //------------------------------peeled_dom_test_elim---------------------------
 247 // If we got the effect of peeling, either by actually peeling or by making
 248 // a pre-loop which must execute at least once, we can remove all
 249 // loop-invariant dominated tests in the main body.
 250 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
 251   bool progress = true;
 252   while( progress ) {
 253     progress = false;           // Reset for next iteration
 254     Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
 255     Node *test = prev->in(0);
 256     while( test != loop->_head ) { // Scan till run off top of loop
 257 
 258       int p_op = prev->Opcode();
 259       if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
 260           test->is_If() &&      // Test?
 261           !test->in(1)->is_Con() && // And not already obvious?
 262           // Condition is not a member of this loop?
 263           !loop->is_member(get_loop(get_ctrl(test->in(1))))){
 264         // Walk loop body looking for instances of this test
 265         for( uint i = 0; i < loop->_body.size(); i++ ) {
 266           Node *n = loop->_body.at(i);
 267           if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
 268             // IfNode was dominated by version in peeled loop body
 269             progress = true;
 270             dominated_by( old_new[prev->_idx], n );
 271           }
 272         }
 273       }
 274       prev = test;
 275       test = idom(test);
 276     } // End of scan tests in loop
 277 
 278   } // End of while( progress )
 279 }
 280 
 281 //------------------------------do_peeling-------------------------------------
 282 // Peel the first iteration of the given loop.
 283 // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 284 //         The pre-loop illegally has 2 control users (old & new loops).
 285 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 286 //         Do this by making the old-loop fall-in edges act as if they came
 287 //         around the loopback from the prior iteration (follow the old-loop
 288 //         backedges) and then map to the new peeled iteration.  This leaves
 289 //         the pre-loop with only 1 user (the new peeled iteration), but the
 290 //         peeled-loop backedge has 2 users.
 291 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 292 //         extra backedge user.
 293 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
 294 
 295   C->set_major_progress();
 296   // Peeling a 'main' loop in a pre/main/post situation obfuscates the
 297   // 'pre' loop from the main and the 'pre' can no longer have it's
 298   // iterations adjusted.  Therefore, we need to declare this loop as
 299   // no longer a 'main' loop; it will need new pre and post loops before
 300   // we can do further RCE.
 301   Node *h = loop->_head;
 302   if( h->is_CountedLoop() ) {
 303     CountedLoopNode *cl = h->as_CountedLoop();
 304     assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
 305     cl->set_trip_count(cl->trip_count() - 1);
 306     if( cl->is_main_loop() ) {
 307       cl->set_normal_loop();
 308 #ifndef PRODUCT
 309       if( PrintOpto && VerifyLoopOptimizations ) {
 310         tty->print("Peeling a 'main' loop; resetting to 'normal' ");
 311         loop->dump_head();
 312       }
 313 #endif
 314     }
 315   }
 316 
 317   // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 318   //         The pre-loop illegally has 2 control users (old & new loops).
 319   clone_loop( loop, old_new, dom_depth(loop->_head) );
 320 
 321 
 322   // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 323   //         Do this by making the old-loop fall-in edges act as if they came
 324   //         around the loopback from the prior iteration (follow the old-loop
 325   //         backedges) and then map to the new peeled iteration.  This leaves
 326   //         the pre-loop with only 1 user (the new peeled iteration), but the
 327   //         peeled-loop backedge has 2 users.
 328   for (DUIterator_Fast jmax, j = loop->_head->fast_outs(jmax); j < jmax; j++) {
 329     Node* old = loop->_head->fast_out(j);
 330     if( old->in(0) == loop->_head && old->req() == 3 &&
 331         (old->is_Loop() || old->is_Phi()) ) {
 332       Node *new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
 333       if( !new_exit_value )     // Backedge value is ALSO loop invariant?
 334         // Then loop body backedge value remains the same.
 335         new_exit_value = old->in(LoopNode::LoopBackControl);
 336       _igvn.hash_delete(old);
 337       old->set_req(LoopNode::EntryControl, new_exit_value);
 338     }
 339   }
 340 
 341 
 342   // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 343   //         extra backedge user.
 344   Node *nnn = old_new[loop->_head->_idx];
 345   _igvn.hash_delete(nnn);
 346   nnn->set_req(LoopNode::LoopBackControl, C->top());
 347   for (DUIterator_Fast j2max, j2 = nnn->fast_outs(j2max); j2 < j2max; j2++) {
 348     Node* use = nnn->fast_out(j2);
 349     if( use->in(0) == nnn && use->req() == 3 && use->is_Phi() ) {
 350       _igvn.hash_delete(use);
 351       use->set_req(LoopNode::LoopBackControl, C->top());
 352     }
 353   }
 354 
 355 
 356   // Step 4: Correct dom-depth info.  Set to loop-head depth.
 357   int dd = dom_depth(loop->_head);
 358   set_idom(loop->_head, loop->_head->in(1), dd);
 359   for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
 360     Node *old = loop->_body.at(j3);
 361     Node *nnn = old_new[old->_idx];
 362     if (!has_ctrl(nnn))
 363       set_idom(nnn, idom(nnn), dd-1);
 364     // While we're at it, remove any SafePoints from the peeled code
 365     if( old->Opcode() == Op_SafePoint ) {
 366       Node *nnn = old_new[old->_idx];
 367       lazy_replace(nnn,nnn->in(TypeFunc::Control));
 368     }
 369   }
 370 
 371   // Now force out all loop-invariant dominating tests.  The optimizer
 372   // finds some, but we _know_ they are all useless.
 373   peeled_dom_test_elim(loop,old_new);
 374 
 375   loop->record_for_igvn();
 376 }
 377 
 378 //------------------------------policy_maximally_unroll------------------------
 379 // Return exact loop trip count, or 0 if not maximally unrolling
 380 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
 381   CountedLoopNode *cl = _head->as_CountedLoop();
 382   assert( cl->is_normal_loop(), "" );
 383 
 384   Node *init_n = cl->init_trip();
 385   Node *limit_n = cl->limit();
 386 
 387   // Non-constant bounds
 388   if( init_n   == NULL || !init_n->is_Con()  ||
 389       limit_n  == NULL || !limit_n->is_Con() ||
 390       // protect against stride not being a constant
 391       !cl->stride_is_con() ) {
 392     return false;
 393   }
 394   int init   = init_n->get_int();
 395   int limit  = limit_n->get_int();
 396   int span   = limit - init;
 397   int stride = cl->stride_con();
 398 
 399   if (init >= limit || stride > span) {
 400     // return a false (no maximally unroll) and the regular unroll/peel
 401     // route will make a small mess which CCP will fold away.
 402     return false;
 403   }
 404   uint trip_count = span/stride;   // trip_count can be greater than 2 Gig.
 405   assert( (int)trip_count*stride == span, "must divide evenly" );
 406 
 407   // Real policy: if we maximally unroll, does it get too big?
 408   // Allow the unrolled mess to get larger than standard loop
 409   // size.  After all, it will no longer be a loop.
 410   uint body_size    = _body.size();
 411   uint unroll_limit = (uint)LoopUnrollLimit * 4;
 412   assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
 413   cl->set_trip_count(trip_count);
 414   if( trip_count <= unroll_limit && body_size <= unroll_limit ) {
 415     uint new_body_size = body_size * trip_count;
 416     if (new_body_size <= unroll_limit &&
 417         body_size == new_body_size / trip_count &&
 418         // Unrolling can result in a large amount of node construction
 419         new_body_size < MaxNodeLimit - phase->C->unique()) {
 420       return true;    // maximally unroll
 421     }
 422   }
 423 
 424   return false;               // Do not maximally unroll
 425 }
 426 
 427 
 428 //------------------------------policy_unroll----------------------------------
 429 // Return TRUE or FALSE if the loop should be unrolled or not.  Unroll if
 430 // the loop is a CountedLoop and the body is small enough.
 431 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
 432 
 433   CountedLoopNode *cl = _head->as_CountedLoop();
 434   assert( cl->is_normal_loop() || cl->is_main_loop(), "" );
 435 
 436   // protect against stride not being a constant
 437   if( !cl->stride_is_con() ) return false;
 438 
 439   // protect against over-unrolling
 440   if( cl->trip_count() <= 1 ) return false;
 441 
 442   int future_unroll_ct = cl->unrolled_count() * 2;
 443 
 444   // Don't unroll if the next round of unrolling would push us
 445   // over the expected trip count of the loop.  One is subtracted
 446   // from the expected trip count because the pre-loop normally
 447   // executes 1 iteration.
 448   if (UnrollLimitForProfileCheck > 0 &&
 449       cl->profile_trip_cnt() != COUNT_UNKNOWN &&
 450       future_unroll_ct        > UnrollLimitForProfileCheck &&
 451       (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
 452     return false;
 453   }
 454 
 455   // When unroll count is greater than LoopUnrollMin, don't unroll if:
 456   //   the residual iterations are more than 10% of the trip count
 457   //   and rounds of "unroll,optimize" are not making significant progress
 458   //   Progress defined as current size less than 20% larger than previous size.
 459   if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
 460       future_unroll_ct > LoopUnrollMin &&
 461       (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() &&
 462       1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
 463     return false;
 464   }
 465 
 466   Node *init_n = cl->init_trip();
 467   Node *limit_n = cl->limit();
 468   // Non-constant bounds.
 469   // Protect against over-unrolling when init or/and limit are not constant
 470   // (so that trip_count's init value is maxint) but iv range is known.
 471   if( init_n   == NULL || !init_n->is_Con()  ||
 472       limit_n  == NULL || !limit_n->is_Con() ) {
 473     Node* phi = cl->phi();
 474     if( phi != NULL ) {
 475       assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
 476       const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
 477       int next_stride = cl->stride_con() * 2; // stride after this unroll
 478       if( next_stride > 0 ) {
 479         if( iv_type->_lo + next_stride <= iv_type->_lo || // overflow
 480             iv_type->_lo + next_stride >  iv_type->_hi ) {
 481           return false;  // over-unrolling
 482         }
 483       } else if( next_stride < 0 ) {
 484         if( iv_type->_hi + next_stride >= iv_type->_hi || // overflow
 485             iv_type->_hi + next_stride <  iv_type->_lo ) {
 486           return false;  // over-unrolling
 487         }
 488       }
 489     }
 490   }
 491 
 492   // Adjust body_size to determine if we unroll or not
 493   uint body_size = _body.size();
 494   // Key test to unroll CaffeineMark's Logic test
 495   int xors_in_loop = 0;
 496   // Also count ModL, DivL and MulL which expand mightly
 497   for( uint k = 0; k < _body.size(); k++ ) {
 498     switch( _body.at(k)->Opcode() ) {
 499     case Op_XorI: xors_in_loop++; break; // CaffeineMark's Logic test
 500     case Op_ModL: body_size += 30; break;
 501     case Op_DivL: body_size += 30; break;
 502     case Op_MulL: body_size += 10; break;
 503     }
 504   }
 505 
 506   // Check for being too big
 507   if( body_size > (uint)LoopUnrollLimit ) {
 508     if( xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
 509     // Normal case: loop too big
 510     return false;
 511   }
 512 
 513   // Check for stride being a small enough constant
 514   if( abs(cl->stride_con()) > (1<<3) ) return false;
 515 
 516   // Unroll once!  (Each trip will soon do double iterations)
 517   return true;
 518 }
 519 
 520 //------------------------------policy_align-----------------------------------
 521 // Return TRUE or FALSE if the loop should be cache-line aligned.  Gather the
 522 // expression that does the alignment.  Note that only one array base can be
 523 // aligned in a loop (unless the VM guarantees mutual alignment).  Note that
 524 // if we vectorize short memory ops into longer memory ops, we may want to
 525 // increase alignment.
 526 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
 527   return false;
 528 }
 529 
 530 //------------------------------policy_range_check-----------------------------
 531 // Return TRUE or FALSE if the loop should be range-check-eliminated.
 532 // Actually we do iteration-splitting, a more powerful form of RCE.
 533 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
 534   if( !RangeCheckElimination ) return false;
 535 
 536   CountedLoopNode *cl = _head->as_CountedLoop();
 537   // If we unrolled with no intention of doing RCE and we later
 538   // changed our minds, we got no pre-loop.  Either we need to
 539   // make a new pre-loop, or we gotta disallow RCE.
 540   if( cl->is_main_no_pre_loop() ) return false; // Disallowed for now.
 541   Node *trip_counter = cl->phi();
 542 
 543   // Check loop body for tests of trip-counter plus loop-invariant vs
 544   // loop-invariant.
 545   for( uint i = 0; i < _body.size(); i++ ) {
 546     Node *iff = _body[i];
 547     if( iff->Opcode() == Op_If ) { // Test?
 548 
 549       // Comparing trip+off vs limit
 550       Node *bol = iff->in(1);
 551       if( bol->req() != 2 ) continue; // dead constant test
 552       if (!bol->is_Bool()) {
 553         assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
 554         continue;
 555       }
 556       Node *cmp = bol->in(1);
 557 
 558       Node *rc_exp = cmp->in(1);
 559       Node *limit = cmp->in(2);
 560 
 561       Node *limit_c = phase->get_ctrl(limit);
 562       if( limit_c == phase->C->top() )
 563         return false;           // Found dead test on live IF?  No RCE!
 564       if( is_member(phase->get_loop(limit_c) ) ) {
 565         // Compare might have operands swapped; commute them
 566         rc_exp = cmp->in(2);
 567         limit  = cmp->in(1);
 568         limit_c = phase->get_ctrl(limit);
 569         if( is_member(phase->get_loop(limit_c) ) )
 570           continue;             // Both inputs are loop varying; cannot RCE
 571       }
 572 
 573       if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
 574         continue;
 575       }
 576       // Yeah!  Found a test like 'trip+off vs limit'
 577       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
 578       // we need loop unswitching instead of iteration splitting.
 579       if( is_loop_exit(iff) )
 580         return true;            // Found reason to split iterations
 581     } // End of is IF
 582   }
 583 
 584   return false;
 585 }
 586 
 587 //------------------------------policy_peel_only-------------------------------
 588 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned.  Useful
 589 // for unrolling loops with NO array accesses.
 590 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
 591 
 592   for( uint i = 0; i < _body.size(); i++ )
 593     if( _body[i]->is_Mem() )
 594       return false;
 595 
 596   // No memory accesses at all!
 597   return true;
 598 }
 599 
 600 //------------------------------clone_up_backedge_goo--------------------------
 601 // If Node n lives in the back_ctrl block and cannot float, we clone a private
 602 // version of n in preheader_ctrl block and return that, otherwise return n.
 603 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ) {
 604   if( get_ctrl(n) != back_ctrl ) return n;
 605 
 606   Node *x = NULL;               // If required, a clone of 'n'
 607   // Check for 'n' being pinned in the backedge.
 608   if( n->in(0) && n->in(0) == back_ctrl ) {
 609     x = n->clone();             // Clone a copy of 'n' to preheader
 610     x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
 611   }
 612 
 613   // Recursive fixup any other input edges into x.
 614   // If there are no changes we can just return 'n', otherwise
 615   // we need to clone a private copy and change it.
 616   for( uint i = 1; i < n->req(); i++ ) {
 617     Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i) );
 618     if( g != n->in(i) ) {
 619       if( !x )
 620         x = n->clone();
 621       x->set_req(i, g);
 622     }
 623   }
 624   if( x ) {                     // x can legally float to pre-header location
 625     register_new_node( x, preheader_ctrl );
 626     return x;
 627   } else {                      // raise n to cover LCA of uses
 628     set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
 629   }
 630   return n;
 631 }
 632 
 633 //------------------------------insert_pre_post_loops--------------------------
 634 // Insert pre and post loops.  If peel_only is set, the pre-loop can not have
 635 // more iterations added.  It acts as a 'peel' only, no lower-bound RCE, no
 636 // alignment.  Useful to unroll loops that do no array accesses.
 637 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
 638 
 639   C->set_major_progress();
 640 
 641   // Find common pieces of the loop being guarded with pre & post loops
 642   CountedLoopNode *main_head = loop->_head->as_CountedLoop();
 643   assert( main_head->is_normal_loop(), "" );
 644   CountedLoopEndNode *main_end = main_head->loopexit();
 645   assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
 646   uint dd_main_head = dom_depth(main_head);
 647   uint max = main_head->outcnt();
 648 
 649   Node *pre_header= main_head->in(LoopNode::EntryControl);
 650   Node *init      = main_head->init_trip();
 651   Node *incr      = main_end ->incr();
 652   Node *limit     = main_end ->limit();
 653   Node *stride    = main_end ->stride();
 654   Node *cmp       = main_end ->cmp_node();
 655   BoolTest::mask b_test = main_end->test_trip();
 656 
 657   // Need only 1 user of 'bol' because I will be hacking the loop bounds.
 658   Node *bol = main_end->in(CountedLoopEndNode::TestValue);
 659   if( bol->outcnt() != 1 ) {
 660     bol = bol->clone();
 661     register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
 662     _igvn.hash_delete(main_end);
 663     main_end->set_req(CountedLoopEndNode::TestValue, bol);
 664   }
 665   // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
 666   if( cmp->outcnt() != 1 ) {
 667     cmp = cmp->clone();
 668     register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
 669     _igvn.hash_delete(bol);
 670     bol->set_req(1, cmp);
 671   }
 672 
 673   //------------------------------
 674   // Step A: Create Post-Loop.
 675   Node* main_exit = main_end->proj_out(false);
 676   assert( main_exit->Opcode() == Op_IfFalse, "" );
 677   int dd_main_exit = dom_depth(main_exit);
 678 
 679   // Step A1: Clone the loop body.  The clone becomes the post-loop.  The main
 680   // loop pre-header illegally has 2 control users (old & new loops).
 681   clone_loop( loop, old_new, dd_main_exit );
 682   assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
 683   CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
 684   post_head->set_post_loop(main_head);
 685 
 686   // Reduce the post-loop trip count.
 687   CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
 688   post_end->_prob = PROB_FAIR;
 689 
 690   // Build the main-loop normal exit.
 691   IfFalseNode *new_main_exit = new (C, 1) IfFalseNode(main_end);
 692   _igvn.register_new_node_with_optimizer( new_main_exit );
 693   set_idom(new_main_exit, main_end, dd_main_exit );
 694   set_loop(new_main_exit, loop->_parent);
 695 
 696   // Step A2: Build a zero-trip guard for the post-loop.  After leaving the
 697   // main-loop, the post-loop may not execute at all.  We 'opaque' the incr
 698   // (the main-loop trip-counter exit value) because we will be changing
 699   // the exit value (via unrolling) so we cannot constant-fold away the zero
 700   // trip guard until all unrolling is done.
 701   Node *zer_opaq = new (C, 2) Opaque1Node(C, incr);
 702   Node *zer_cmp  = new (C, 3) CmpINode( zer_opaq, limit );
 703   Node *zer_bol  = new (C, 2) BoolNode( zer_cmp, b_test );
 704   register_new_node( zer_opaq, new_main_exit );
 705   register_new_node( zer_cmp , new_main_exit );
 706   register_new_node( zer_bol , new_main_exit );
 707 
 708   // Build the IfNode
 709   IfNode *zer_iff = new (C, 2) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
 710   _igvn.register_new_node_with_optimizer( zer_iff );
 711   set_idom(zer_iff, new_main_exit, dd_main_exit);
 712   set_loop(zer_iff, loop->_parent);
 713 
 714   // Plug in the false-path, taken if we need to skip post-loop
 715   _igvn.hash_delete( main_exit );
 716   main_exit->set_req(0, zer_iff);
 717   _igvn._worklist.push(main_exit);
 718   set_idom(main_exit, zer_iff, dd_main_exit);
 719   set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
 720   // Make the true-path, must enter the post loop
 721   Node *zer_taken = new (C, 1) IfTrueNode( zer_iff );
 722   _igvn.register_new_node_with_optimizer( zer_taken );
 723   set_idom(zer_taken, zer_iff, dd_main_exit);
 724   set_loop(zer_taken, loop->_parent);
 725   // Plug in the true path
 726   _igvn.hash_delete( post_head );
 727   post_head->set_req(LoopNode::EntryControl, zer_taken);
 728   set_idom(post_head, zer_taken, dd_main_exit);
 729 
 730   // Step A3: Make the fall-in values to the post-loop come from the
 731   // fall-out values of the main-loop.
 732   for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
 733     Node* main_phi = main_head->fast_out(i);
 734     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
 735       Node *post_phi = old_new[main_phi->_idx];
 736       Node *fallmain  = clone_up_backedge_goo(main_head->back_control(),
 737                                               post_head->init_control(),
 738                                               main_phi->in(LoopNode::LoopBackControl));
 739       _igvn.hash_delete(post_phi);
 740       post_phi->set_req( LoopNode::EntryControl, fallmain );
 741     }
 742   }
 743 
 744   // Update local caches for next stanza
 745   main_exit = new_main_exit;
 746 
 747 
 748   //------------------------------
 749   // Step B: Create Pre-Loop.
 750 
 751   // Step B1: Clone the loop body.  The clone becomes the pre-loop.  The main
 752   // loop pre-header illegally has 2 control users (old & new loops).
 753   clone_loop( loop, old_new, dd_main_head );
 754   CountedLoopNode*    pre_head = old_new[main_head->_idx]->as_CountedLoop();
 755   CountedLoopEndNode* pre_end  = old_new[main_end ->_idx]->as_CountedLoopEnd();
 756   pre_head->set_pre_loop(main_head);
 757   Node *pre_incr = old_new[incr->_idx];
 758 
 759   // Reduce the pre-loop trip count.
 760   pre_end->_prob = PROB_FAIR;
 761 
 762   // Find the pre-loop normal exit.
 763   Node* pre_exit = pre_end->proj_out(false);
 764   assert( pre_exit->Opcode() == Op_IfFalse, "" );
 765   IfFalseNode *new_pre_exit = new (C, 1) IfFalseNode(pre_end);
 766   _igvn.register_new_node_with_optimizer( new_pre_exit );
 767   set_idom(new_pre_exit, pre_end, dd_main_head);
 768   set_loop(new_pre_exit, loop->_parent);
 769 
 770   // Step B2: Build a zero-trip guard for the main-loop.  After leaving the
 771   // pre-loop, the main-loop may not execute at all.  Later in life this
 772   // zero-trip guard will become the minimum-trip guard when we unroll
 773   // the main-loop.
 774   Node *min_opaq = new (C, 2) Opaque1Node(C, limit);
 775   Node *min_cmp  = new (C, 3) CmpINode( pre_incr, min_opaq );
 776   Node *min_bol  = new (C, 2) BoolNode( min_cmp, b_test );
 777   register_new_node( min_opaq, new_pre_exit );
 778   register_new_node( min_cmp , new_pre_exit );
 779   register_new_node( min_bol , new_pre_exit );
 780 
 781   // Build the IfNode (assume the main-loop is executed always).
 782   IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
 783   _igvn.register_new_node_with_optimizer( min_iff );
 784   set_idom(min_iff, new_pre_exit, dd_main_head);
 785   set_loop(min_iff, loop->_parent);
 786 
 787   // Plug in the false-path, taken if we need to skip main-loop
 788   _igvn.hash_delete( pre_exit );
 789   pre_exit->set_req(0, min_iff);
 790   set_idom(pre_exit, min_iff, dd_main_head);
 791   set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
 792   // Make the true-path, must enter the main loop
 793   Node *min_taken = new (C, 1) IfTrueNode( min_iff );
 794   _igvn.register_new_node_with_optimizer( min_taken );
 795   set_idom(min_taken, min_iff, dd_main_head);
 796   set_loop(min_taken, loop->_parent);
 797   // Plug in the true path
 798   _igvn.hash_delete( main_head );
 799   main_head->set_req(LoopNode::EntryControl, min_taken);
 800   set_idom(main_head, min_taken, dd_main_head);
 801 
 802   // Step B3: Make the fall-in values to the main-loop come from the
 803   // fall-out values of the pre-loop.
 804   for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
 805     Node* main_phi = main_head->fast_out(i2);
 806     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
 807       Node *pre_phi = old_new[main_phi->_idx];
 808       Node *fallpre  = clone_up_backedge_goo(pre_head->back_control(),
 809                                              main_head->init_control(),
 810                                              pre_phi->in(LoopNode::LoopBackControl));
 811       _igvn.hash_delete(main_phi);
 812       main_phi->set_req( LoopNode::EntryControl, fallpre );
 813     }
 814   }
 815 
 816   // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
 817   // RCE and alignment may change this later.
 818   Node *cmp_end = pre_end->cmp_node();
 819   assert( cmp_end->in(2) == limit, "" );
 820   Node *pre_limit = new (C, 3) AddINode( init, stride );
 821 
 822   // Save the original loop limit in this Opaque1 node for
 823   // use by range check elimination.
 824   Node *pre_opaq  = new (C, 3) Opaque1Node(C, pre_limit, limit);
 825 
 826   register_new_node( pre_limit, pre_head->in(0) );
 827   register_new_node( pre_opaq , pre_head->in(0) );
 828 
 829   // Since no other users of pre-loop compare, I can hack limit directly
 830   assert( cmp_end->outcnt() == 1, "no other users" );
 831   _igvn.hash_delete(cmp_end);
 832   cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
 833 
 834   // Special case for not-equal loop bounds:
 835   // Change pre loop test, main loop test, and the
 836   // main loop guard test to use lt or gt depending on stride
 837   // direction:
 838   // positive stride use <
 839   // negative stride use >
 840 
 841   if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
 842 
 843     BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
 844     // Modify pre loop end condition
 845     Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
 846     BoolNode* new_bol0 = new (C, 2) BoolNode(pre_bol->in(1), new_test);
 847     register_new_node( new_bol0, pre_head->in(0) );
 848     _igvn.hash_delete(pre_end);
 849     pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0);
 850     // Modify main loop guard condition
 851     assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
 852     BoolNode* new_bol1 = new (C, 2) BoolNode(min_bol->in(1), new_test);
 853     register_new_node( new_bol1, new_pre_exit );
 854     _igvn.hash_delete(min_iff);
 855     min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
 856     // Modify main loop end condition
 857     BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
 858     BoolNode* new_bol2 = new (C, 2) BoolNode(main_bol->in(1), new_test);
 859     register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
 860     _igvn.hash_delete(main_end);
 861     main_end->set_req(CountedLoopEndNode::TestValue, new_bol2);
 862   }
 863 
 864   // Flag main loop
 865   main_head->set_main_loop();
 866   if( peel_only ) main_head->set_main_no_pre_loop();
 867 
 868   // It's difficult to be precise about the trip-counts
 869   // for the pre/post loops.  They are usually very short,
 870   // so guess that 4 trips is a reasonable value.
 871   post_head->set_profile_trip_cnt(4.0);
 872   pre_head->set_profile_trip_cnt(4.0);
 873 
 874   // Now force out all loop-invariant dominating tests.  The optimizer
 875   // finds some, but we _know_ they are all useless.
 876   peeled_dom_test_elim(loop,old_new);
 877 }
 878 
 879 //------------------------------is_invariant-----------------------------
 880 // Return true if n is invariant
 881 bool IdealLoopTree::is_invariant(Node* n) const {
 882   Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
 883   if (n_c->is_top()) return false;
 884   return !is_member(_phase->get_loop(n_c));
 885 }
 886 
 887 
 888 //------------------------------do_unroll--------------------------------------
 889 // Unroll the loop body one step - make each trip do 2 iterations.
 890 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
 891   assert( LoopUnrollLimit, "" );
 892 #ifndef PRODUCT
 893   if( PrintOpto && VerifyLoopOptimizations ) {
 894     tty->print("Unrolling ");
 895     loop->dump_head();
 896   }
 897 #endif
 898   CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
 899   CountedLoopEndNode *loop_end = loop_head->loopexit();
 900   assert( loop_end, "" );
 901 
 902   // Remember loop node count before unrolling to detect
 903   // if rounds of unroll,optimize are making progress
 904   loop_head->set_node_count_before_unroll(loop->_body.size());
 905 
 906   Node *ctrl  = loop_head->in(LoopNode::EntryControl);
 907   Node *limit = loop_head->limit();
 908   Node *init  = loop_head->init_trip();
 909   Node *strid = loop_head->stride();
 910 
 911   Node *opaq = NULL;
 912   if( adjust_min_trip ) {       // If not maximally unrolling, need adjustment
 913     assert( loop_head->is_main_loop(), "" );
 914     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
 915     Node *iff = ctrl->in(0);
 916     assert( iff->Opcode() == Op_If, "" );
 917     Node *bol = iff->in(1);
 918     assert( bol->Opcode() == Op_Bool, "" );
 919     Node *cmp = bol->in(1);
 920     assert( cmp->Opcode() == Op_CmpI, "" );
 921     opaq = cmp->in(2);
 922     // Occasionally it's possible for a pre-loop Opaque1 node to be
 923     // optimized away and then another round of loop opts attempted.
 924     // We can not optimize this particular loop in that case.
 925     if( opaq->Opcode() != Op_Opaque1 )
 926       return;                   // Cannot find pre-loop!  Bail out!
 927   }
 928 
 929   C->set_major_progress();
 930 
 931   // Adjust max trip count. The trip count is intentionally rounded
 932   // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
 933   // the main, unrolled, part of the loop will never execute as it is protected
 934   // by the min-trip test.  See bug 4834191 for a case where we over-unrolled
 935   // and later determined that part of the unrolled loop was dead.
 936   loop_head->set_trip_count(loop_head->trip_count() / 2);
 937 
 938   // Double the count of original iterations in the unrolled loop body.
 939   loop_head->double_unrolled_count();
 940 
 941   // -----------
 942   // Step 2: Cut back the trip counter for an unroll amount of 2.
 943   // Loop will normally trip (limit - init)/stride_con.  Since it's a
 944   // CountedLoop this is exact (stride divides limit-init exactly).
 945   // We are going to double the loop body, so we want to knock off any
 946   // odd iteration: (trip_cnt & ~1).  Then back compute a new limit.
 947   Node *span = new (C, 3) SubINode( limit, init );
 948   register_new_node( span, ctrl );
 949   Node *trip = new (C, 3) DivINode( 0, span, strid );
 950   register_new_node( trip, ctrl );
 951   Node *mtwo = _igvn.intcon(-2);
 952   set_ctrl(mtwo, C->root());
 953   Node *rond = new (C, 3) AndINode( trip, mtwo );
 954   register_new_node( rond, ctrl );
 955   Node *spn2 = new (C, 3) MulINode( rond, strid );
 956   register_new_node( spn2, ctrl );
 957   Node *lim2 = new (C, 3) AddINode( spn2, init );
 958   register_new_node( lim2, ctrl );
 959 
 960   // Hammer in the new limit
 961   Node *ctrl2 = loop_end->in(0);
 962   Node *cmp2 = new (C, 3) CmpINode( loop_head->incr(), lim2 );
 963   register_new_node( cmp2, ctrl2 );
 964   Node *bol2 = new (C, 2) BoolNode( cmp2, loop_end->test_trip() );
 965   register_new_node( bol2, ctrl2 );
 966   _igvn.hash_delete(loop_end);
 967   loop_end->set_req(CountedLoopEndNode::TestValue, bol2);
 968 
 969   // Step 3: Find the min-trip test guaranteed before a 'main' loop.
 970   // Make it a 1-trip test (means at least 2 trips).
 971   if( adjust_min_trip ) {
 972     // Guard test uses an 'opaque' node which is not shared.  Hence I
 973     // can edit it's inputs directly.  Hammer in the new limit for the
 974     // minimum-trip guard.
 975     assert( opaq->outcnt() == 1, "" );
 976     _igvn.hash_delete(opaq);
 977     opaq->set_req(1, lim2);
 978   }
 979 
 980   // ---------
 981   // Step 4: Clone the loop body.  Move it inside the loop.  This loop body
 982   // represents the odd iterations; since the loop trips an even number of
 983   // times its backedge is never taken.  Kill the backedge.
 984   uint dd = dom_depth(loop_head);
 985   clone_loop( loop, old_new, dd );
 986 
 987   // Make backedges of the clone equal to backedges of the original.
 988   // Make the fall-in from the original come from the fall-out of the clone.
 989   for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
 990     Node* phi = loop_head->fast_out(j);
 991     if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
 992       Node *newphi = old_new[phi->_idx];
 993       _igvn.hash_delete( phi );
 994       _igvn.hash_delete( newphi );
 995 
 996       phi   ->set_req(LoopNode::   EntryControl, newphi->in(LoopNode::LoopBackControl));
 997       newphi->set_req(LoopNode::LoopBackControl, phi   ->in(LoopNode::LoopBackControl));
 998       phi   ->set_req(LoopNode::LoopBackControl, C->top());
 999     }
1000   }
1001   Node *clone_head = old_new[loop_head->_idx];
1002   _igvn.hash_delete( clone_head );
1003   loop_head ->set_req(LoopNode::   EntryControl, clone_head->in(LoopNode::LoopBackControl));
1004   clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1005   loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1006   loop->_head = clone_head;     // New loop header
1007 
1008   set_idom(loop_head,  loop_head ->in(LoopNode::EntryControl), dd);
1009   set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1010 
1011   // Kill the clone's backedge
1012   Node *newcle = old_new[loop_end->_idx];
1013   _igvn.hash_delete( newcle );
1014   Node *one = _igvn.intcon(1);
1015   set_ctrl(one, C->root());
1016   newcle->set_req(1, one);
1017   // Force clone into same loop body
1018   uint max = loop->_body.size();
1019   for( uint k = 0; k < max; k++ ) {
1020     Node *old = loop->_body.at(k);
1021     Node *nnn = old_new[old->_idx];
1022     loop->_body.push(nnn);
1023     if (!has_ctrl(old))
1024       set_loop(nnn, loop);
1025   }
1026 
1027   loop->record_for_igvn();
1028 }
1029 
1030 //------------------------------do_maximally_unroll----------------------------
1031 
1032 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1033   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1034   assert( cl->trip_count() > 0, "");
1035 
1036   // If loop is tripping an odd number of times, peel odd iteration
1037   if( (cl->trip_count() & 1) == 1 ) {
1038     do_peeling( loop, old_new );
1039   }
1040 
1041   // Now its tripping an even number of times remaining.  Double loop body.
1042   // Do not adjust pre-guards; they are not needed and do not exist.
1043   if( cl->trip_count() > 0 ) {
1044     do_unroll( loop, old_new, false );
1045   }
1046 }
1047 
1048 //------------------------------dominates_backedge---------------------------------
1049 // Returns true if ctrl is executed on every complete iteration
1050 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1051   assert(ctrl->is_CFG(), "must be control");
1052   Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1053   return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1054 }
1055 
1056 //------------------------------add_constraint---------------------------------
1057 // Constrain the main loop iterations so the condition:
1058 //    scale_con * I + offset  <  limit
1059 // always holds true.  That is, either increase the number of iterations in
1060 // the pre-loop or the post-loop until the condition holds true in the main
1061 // loop.  Stride, scale, offset and limit are all loop invariant.  Further,
1062 // stride and scale are constants (offset and limit often are).
1063 void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) {
1064 
1065   // Compute "I :: (limit-offset)/scale_con"
1066   Node *con = new (C, 3) SubINode( limit, offset );
1067   register_new_node( con, pre_ctrl );
1068   Node *scale = _igvn.intcon(scale_con);
1069   set_ctrl(scale, C->root());
1070   Node *X = new (C, 3) DivINode( 0, con, scale );
1071   register_new_node( X, pre_ctrl );
1072 
1073   // For positive stride, the pre-loop limit always uses a MAX function
1074   // and the main loop a MIN function.  For negative stride these are
1075   // reversed.
1076 
1077   // Also for positive stride*scale the affine function is increasing, so the
1078   // pre-loop must check for underflow and the post-loop for overflow.
1079   // Negative stride*scale reverses this; pre-loop checks for overflow and
1080   // post-loop for underflow.
1081   if( stride_con*scale_con > 0 ) {
1082     // Compute I < (limit-offset)/scale_con
1083     // Adjust main-loop last iteration to be MIN/MAX(main_loop,X)
1084     *main_limit = (stride_con > 0)
1085       ? (Node*)(new (C, 3) MinINode( *main_limit, X ))
1086       : (Node*)(new (C, 3) MaxINode( *main_limit, X ));
1087     register_new_node( *main_limit, pre_ctrl );
1088 
1089   } else {
1090     // Compute (limit-offset)/scale_con + SGN(-scale_con) <= I
1091     // Add the negation of the main-loop constraint to the pre-loop.
1092     // See footnote [++] below for a derivation of the limit expression.
1093     Node *incr = _igvn.intcon(scale_con > 0 ? -1 : 1);
1094     set_ctrl(incr, C->root());
1095     Node *adj = new (C, 3) AddINode( X, incr );
1096     register_new_node( adj, pre_ctrl );
1097     *pre_limit = (scale_con > 0)
1098       ? (Node*)new (C, 3) MinINode( *pre_limit, adj )
1099       : (Node*)new (C, 3) MaxINode( *pre_limit, adj );
1100     register_new_node( *pre_limit, pre_ctrl );
1101 
1102 //   [++] Here's the algebra that justifies the pre-loop limit expression:
1103 //
1104 //   NOT( scale_con * I + offset  <  limit )
1105 //      ==
1106 //   scale_con * I + offset  >=  limit
1107 //      ==
1108 //   SGN(scale_con) * I  >=  (limit-offset)/|scale_con|
1109 //      ==
1110 //   (limit-offset)/|scale_con|   <=  I * SGN(scale_con)
1111 //      ==
1112 //   (limit-offset)/|scale_con|-1  <  I * SGN(scale_con)
1113 //      ==
1114 //   ( if (scale_con > 0) /*common case*/
1115 //       (limit-offset)/scale_con - 1  <  I
1116 //     else
1117 //       (limit-offset)/scale_con + 1  >  I
1118 //    )
1119 //   ( if (scale_con > 0) /*common case*/
1120 //       (limit-offset)/scale_con + SGN(-scale_con)  <  I
1121 //     else
1122 //       (limit-offset)/scale_con + SGN(-scale_con)  >  I
1123   }
1124 }
1125 
1126 
1127 //------------------------------is_scaled_iv---------------------------------
1128 // Return true if exp is a constant times an induction var
1129 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1130   if (exp == iv) {
1131     if (p_scale != NULL) {
1132       *p_scale = 1;
1133     }
1134     return true;
1135   }
1136   int opc = exp->Opcode();
1137   if (opc == Op_MulI) {
1138     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1139       if (p_scale != NULL) {
1140         *p_scale = exp->in(2)->get_int();
1141       }
1142       return true;
1143     }
1144     if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1145       if (p_scale != NULL) {
1146         *p_scale = exp->in(1)->get_int();
1147       }
1148       return true;
1149     }
1150   } else if (opc == Op_LShiftI) {
1151     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1152       if (p_scale != NULL) {
1153         *p_scale = 1 << exp->in(2)->get_int();
1154       }
1155       return true;
1156     }
1157   }
1158   return false;
1159 }
1160 
1161 //-----------------------------is_scaled_iv_plus_offset------------------------------
1162 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1163 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1164   if (is_scaled_iv(exp, iv, p_scale)) {
1165     if (p_offset != NULL) {
1166       Node *zero = _igvn.intcon(0);
1167       set_ctrl(zero, C->root());
1168       *p_offset = zero;
1169     }
1170     return true;
1171   }
1172   int opc = exp->Opcode();
1173   if (opc == Op_AddI) {
1174     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1175       if (p_offset != NULL) {
1176         *p_offset = exp->in(2);
1177       }
1178       return true;
1179     }
1180     if (exp->in(2)->is_Con()) {
1181       Node* offset2 = NULL;
1182       if (depth < 2 &&
1183           is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
1184                                    p_offset != NULL ? &offset2 : NULL, depth+1)) {
1185         if (p_offset != NULL) {
1186           Node *ctrl_off2 = get_ctrl(offset2);
1187           Node* offset = new (C, 3) AddINode(offset2, exp->in(2));
1188           register_new_node(offset, ctrl_off2);
1189           *p_offset = offset;
1190         }
1191         return true;
1192       }
1193     }
1194   } else if (opc == Op_SubI) {
1195     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1196       if (p_offset != NULL) {
1197         Node *zero = _igvn.intcon(0);
1198         set_ctrl(zero, C->root());
1199         Node *ctrl_off = get_ctrl(exp->in(2));
1200         Node* offset = new (C, 3) SubINode(zero, exp->in(2));
1201         register_new_node(offset, ctrl_off);
1202         *p_offset = offset;
1203       }
1204       return true;
1205     }
1206     if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1207       if (p_offset != NULL) {
1208         *p_scale *= -1;
1209         *p_offset = exp->in(1);
1210       }
1211       return true;
1212     }
1213   }
1214   return false;
1215 }
1216 
1217 //------------------------------do_range_check---------------------------------
1218 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1219 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
1220 #ifndef PRODUCT
1221   if( PrintOpto && VerifyLoopOptimizations ) {
1222     tty->print("Range Check Elimination ");
1223     loop->dump_head();
1224   }
1225 #endif
1226   assert( RangeCheckElimination, "" );
1227   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1228   assert( cl->is_main_loop(), "" );
1229 
1230   // Find the trip counter; we are iteration splitting based on it
1231   Node *trip_counter = cl->phi();
1232   // Find the main loop limit; we will trim it's iterations
1233   // to not ever trip end tests
1234   Node *main_limit = cl->limit();
1235   // Find the pre-loop limit; we will expand it's iterations to
1236   // not ever trip low tests.
1237   Node *ctrl  = cl->in(LoopNode::EntryControl);
1238   assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
1239   Node *iffm = ctrl->in(0);
1240   assert( iffm->Opcode() == Op_If, "" );
1241   Node *p_f = iffm->in(0);
1242   assert( p_f->Opcode() == Op_IfFalse, "" );
1243   CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
1244   assert( pre_end->loopnode()->is_pre_loop(), "" );
1245   Node *pre_opaq1 = pre_end->limit();
1246   // Occasionally it's possible for a pre-loop Opaque1 node to be
1247   // optimized away and then another round of loop opts attempted.
1248   // We can not optimize this particular loop in that case.
1249   if( pre_opaq1->Opcode() != Op_Opaque1 )
1250     return;
1251   Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
1252   Node *pre_limit = pre_opaq->in(1);
1253 
1254   // Where do we put new limit calculations
1255   Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
1256 
1257   // Ensure the original loop limit is available from the
1258   // pre-loop Opaque1 node.
1259   Node *orig_limit = pre_opaq->original_loop_limit();
1260   if( orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP )
1261     return;
1262 
1263   // Need to find the main-loop zero-trip guard
1264   Node *bolzm = iffm->in(1);
1265   assert( bolzm->Opcode() == Op_Bool, "" );
1266   Node *cmpzm = bolzm->in(1);
1267   assert( cmpzm->is_Cmp(), "" );
1268   Node *opqzm = cmpzm->in(2);
1269   if( opqzm->Opcode() != Op_Opaque1 )
1270     return;
1271   assert( opqzm->in(1) == main_limit, "do not understand situation" );
1272 
1273   // Must know if its a count-up or count-down loop
1274 
1275   // protect against stride not being a constant
1276   if ( !cl->stride_is_con() ) {
1277     return;
1278   }
1279   int stride_con = cl->stride_con();
1280   Node *zero = _igvn.intcon(0);
1281   Node *one  = _igvn.intcon(1);
1282   set_ctrl(zero, C->root());
1283   set_ctrl(one,  C->root());
1284 
1285   // Range checks that do not dominate the loop backedge (ie.
1286   // conditionally executed) can lengthen the pre loop limit beyond
1287   // the original loop limit. To prevent this, the pre limit is
1288   // (for stride > 0) MINed with the original loop limit (MAXed
1289   // stride < 0) when some range_check (rc) is conditionally
1290   // executed.
1291   bool conditional_rc = false;
1292 
1293   // Check loop body for tests of trip-counter plus loop-invariant vs
1294   // loop-invariant.
1295   for( uint i = 0; i < loop->_body.size(); i++ ) {
1296     Node *iff = loop->_body[i];
1297     if( iff->Opcode() == Op_If ) { // Test?
1298 
1299       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
1300       // we need loop unswitching instead of iteration splitting.
1301       Node *exit = loop->is_loop_exit(iff);
1302       if( !exit ) continue;
1303       int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
1304 
1305       // Get boolean condition to test
1306       Node *i1 = iff->in(1);
1307       if( !i1->is_Bool() ) continue;
1308       BoolNode *bol = i1->as_Bool();
1309       BoolTest b_test = bol->_test;
1310       // Flip sense of test if exit condition is flipped
1311       if( flip )
1312         b_test = b_test.negate();
1313 
1314       // Get compare
1315       Node *cmp = bol->in(1);
1316 
1317       // Look for trip_counter + offset vs limit
1318       Node *rc_exp = cmp->in(1);
1319       Node *limit  = cmp->in(2);
1320       jint scale_con= 1;        // Assume trip counter not scaled
1321 
1322       Node *limit_c = get_ctrl(limit);
1323       if( loop->is_member(get_loop(limit_c) ) ) {
1324         // Compare might have operands swapped; commute them
1325         b_test = b_test.commute();
1326         rc_exp = cmp->in(2);
1327         limit  = cmp->in(1);
1328         limit_c = get_ctrl(limit);
1329         if( loop->is_member(get_loop(limit_c) ) )
1330           continue;             // Both inputs are loop varying; cannot RCE
1331       }
1332       // Here we know 'limit' is loop invariant
1333 
1334       // 'limit' maybe pinned below the zero trip test (probably from a
1335       // previous round of rce), in which case, it can't be used in the
1336       // zero trip test expression which must occur before the zero test's if.
1337       if( limit_c == ctrl ) {
1338         continue;  // Don't rce this check but continue looking for other candidates.
1339       }
1340 
1341       // Check for scaled induction variable plus an offset
1342       Node *offset = NULL;
1343 
1344       if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
1345         continue;
1346       }
1347 
1348       Node *offset_c = get_ctrl(offset);
1349       if( loop->is_member( get_loop(offset_c) ) )
1350         continue;               // Offset is not really loop invariant
1351       // Here we know 'offset' is loop invariant.
1352 
1353       // As above for the 'limit', the 'offset' maybe pinned below the
1354       // zero trip test.
1355       if( offset_c == ctrl ) {
1356         continue; // Don't rce this check but continue looking for other candidates.
1357       }
1358 
1359       // At this point we have the expression as:
1360       //   scale_con * trip_counter + offset :: limit
1361       // where scale_con, offset and limit are loop invariant.  Trip_counter
1362       // monotonically increases by stride_con, a constant.  Both (or either)
1363       // stride_con and scale_con can be negative which will flip about the
1364       // sense of the test.
1365 
1366       // Adjust pre and main loop limits to guard the correct iteration set
1367       if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
1368         if( b_test._test == BoolTest::lt ) { // Range checks always use lt
1369           // The overflow limit: scale*I+offset < limit
1370           add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit );
1371           // The underflow limit: 0 <= scale*I+offset.
1372           // Some math yields: -scale*I-(offset+1) < 0
1373           Node *plus_one = new (C, 3) AddINode( offset, one );
1374           register_new_node( plus_one, pre_ctrl );
1375           Node *neg_offset = new (C, 3) SubINode( zero, plus_one );
1376           register_new_node( neg_offset, pre_ctrl );
1377           add_constraint( stride_con, -scale_con, neg_offset, zero, pre_ctrl, &pre_limit, &main_limit );
1378           if (!conditional_rc) {
1379             conditional_rc = !loop->dominates_backedge(iff);
1380           }
1381         } else {
1382 #ifndef PRODUCT
1383           if( PrintOpto )
1384             tty->print_cr("missed RCE opportunity");
1385 #endif
1386           continue;             // In release mode, ignore it
1387         }
1388       } else {                  // Otherwise work on normal compares
1389         switch( b_test._test ) {
1390         case BoolTest::ge:      // Convert X >= Y to -X <= -Y
1391           scale_con = -scale_con;
1392           offset = new (C, 3) SubINode( zero, offset );
1393           register_new_node( offset, pre_ctrl );
1394           limit  = new (C, 3) SubINode( zero, limit  );
1395           register_new_node( limit, pre_ctrl );
1396           // Fall into LE case
1397         case BoolTest::le:      // Convert X <= Y to X < Y+1
1398           limit = new (C, 3) AddINode( limit, one );
1399           register_new_node( limit, pre_ctrl );
1400           // Fall into LT case
1401         case BoolTest::lt:
1402           add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit );
1403           if (!conditional_rc) {
1404             conditional_rc = !loop->dominates_backedge(iff);
1405           }
1406           break;
1407         default:
1408 #ifndef PRODUCT
1409           if( PrintOpto )
1410             tty->print_cr("missed RCE opportunity");
1411 #endif
1412           continue;             // Unhandled case
1413         }
1414       }
1415 
1416       // Kill the eliminated test
1417       C->set_major_progress();
1418       Node *kill_con = _igvn.intcon( 1-flip );
1419       set_ctrl(kill_con, C->root());
1420       _igvn.hash_delete(iff);
1421       iff->set_req(1, kill_con);
1422       _igvn._worklist.push(iff);
1423       // Find surviving projection
1424       assert(iff->is_If(), "");
1425       ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
1426       // Find loads off the surviving projection; remove their control edge
1427       for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
1428         Node* cd = dp->fast_out(i); // Control-dependent node
1429         if( cd->is_Load() ) {   // Loads can now float around in the loop
1430           _igvn.hash_delete(cd);
1431           // Allow the load to float around in the loop, or before it
1432           // but NOT before the pre-loop.
1433           cd->set_req(0, ctrl);   // ctrl, not NULL
1434           _igvn._worklist.push(cd);
1435           --i;
1436           --imax;
1437         }
1438       }
1439 
1440     } // End of is IF
1441 
1442   }
1443 
1444   // Update loop limits
1445   if (conditional_rc) {
1446     pre_limit = (stride_con > 0) ? (Node*)new (C,3) MinINode(pre_limit, orig_limit)
1447                                  : (Node*)new (C,3) MaxINode(pre_limit, orig_limit);
1448     register_new_node(pre_limit, pre_ctrl);
1449   }
1450   _igvn.hash_delete(pre_opaq);
1451   pre_opaq->set_req(1, pre_limit);
1452 
1453   // Note:: we are making the main loop limit no longer precise;
1454   // need to round up based on stride.
1455   if( stride_con != 1 && stride_con != -1 ) { // Cutout for common case
1456     // "Standard" round-up logic:  ([main_limit-init+(y-1)]/y)*y+init
1457     // Hopefully, compiler will optimize for powers of 2.
1458     Node *ctrl = get_ctrl(main_limit);
1459     Node *stride = cl->stride();
1460     Node *init = cl->init_trip();
1461     Node *span = new (C, 3) SubINode(main_limit,init);
1462     register_new_node(span,ctrl);
1463     Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
1464     Node *add = new (C, 3) AddINode(span,rndup);
1465     register_new_node(add,ctrl);
1466     Node *div = new (C, 3) DivINode(0,add,stride);
1467     register_new_node(div,ctrl);
1468     Node *mul = new (C, 3) MulINode(div,stride);
1469     register_new_node(mul,ctrl);
1470     Node *newlim = new (C, 3) AddINode(mul,init);
1471     register_new_node(newlim,ctrl);
1472     main_limit = newlim;
1473   }
1474 
1475   Node *main_cle = cl->loopexit();
1476   Node *main_bol = main_cle->in(1);
1477   // Hacking loop bounds; need private copies of exit test
1478   if( main_bol->outcnt() > 1 ) {// BoolNode shared?
1479     _igvn.hash_delete(main_cle);
1480     main_bol = main_bol->clone();// Clone a private BoolNode
1481     register_new_node( main_bol, main_cle->in(0) );
1482     main_cle->set_req(1,main_bol);
1483   }
1484   Node *main_cmp = main_bol->in(1);
1485   if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
1486     _igvn.hash_delete(main_bol);
1487     main_cmp = main_cmp->clone();// Clone a private CmpNode
1488     register_new_node( main_cmp, main_cle->in(0) );
1489     main_bol->set_req(1,main_cmp);
1490   }
1491   // Hack the now-private loop bounds
1492   _igvn.hash_delete(main_cmp);
1493   main_cmp->set_req(2, main_limit);
1494   _igvn._worklist.push(main_cmp);
1495   // The OpaqueNode is unshared by design
1496   _igvn.hash_delete(opqzm);
1497   assert( opqzm->outcnt() == 1, "cannot hack shared node" );
1498   opqzm->set_req(1,main_limit);
1499   _igvn._worklist.push(opqzm);
1500 }
1501 
1502 //------------------------------DCE_loop_body----------------------------------
1503 // Remove simplistic dead code from loop body
1504 void IdealLoopTree::DCE_loop_body() {
1505   for( uint i = 0; i < _body.size(); i++ )
1506     if( _body.at(i)->outcnt() == 0 )
1507       _body.map( i--, _body.pop() );
1508 }
1509 
1510 
1511 //------------------------------adjust_loop_exit_prob--------------------------
1512 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
1513 // Replace with a 1-in-10 exit guess.
1514 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
1515   Node *test = tail();
1516   while( test != _head ) {
1517     uint top = test->Opcode();
1518     if( top == Op_IfTrue || top == Op_IfFalse ) {
1519       int test_con = ((ProjNode*)test)->_con;
1520       assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
1521       IfNode *iff = test->in(0)->as_If();
1522       if( iff->outcnt() == 2 ) {        // Ignore dead tests
1523         Node *bol = iff->in(1);
1524         if( bol && bol->req() > 1 && bol->in(1) &&
1525             ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
1526              (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
1527              (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
1528              (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
1529              (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
1530              (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
1531              (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
1532           return;               // Allocation loops RARELY take backedge
1533         // Find the OTHER exit path from the IF
1534         Node* ex = iff->proj_out(1-test_con);
1535         float p = iff->_prob;
1536         if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
1537           if( top == Op_IfTrue ) {
1538             if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
1539               iff->_prob = PROB_STATIC_FREQUENT;
1540             }
1541           } else {
1542             if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
1543               iff->_prob = PROB_STATIC_INFREQUENT;
1544             }
1545           }
1546         }
1547       }
1548     }
1549     test = phase->idom(test);
1550   }
1551 }
1552 
1553 
1554 //------------------------------policy_do_remove_empty_loop--------------------
1555 // Micro-benchmark spamming.  Policy is to always remove empty loops.
1556 // The 'DO' part is to replace the trip counter with the value it will
1557 // have on the last iteration.  This will break the loop.
1558 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
1559   // Minimum size must be empty loop
1560   if( _body.size() > 7/*number of nodes in an empty loop*/ ) return false;
1561 
1562   if( !_head->is_CountedLoop() ) return false;     // Dead loop
1563   CountedLoopNode *cl = _head->as_CountedLoop();
1564   if( !cl->loopexit() ) return false; // Malformed loop
1565   if( !phase->is_member(this,phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)) ) )
1566     return false;             // Infinite loop
1567 #ifndef PRODUCT
1568   if( PrintOpto )
1569     tty->print_cr("Removing empty loop");
1570 #endif
1571 #ifdef ASSERT
1572   // Ensure only one phi which is the iv.
1573   Node* iv = NULL;
1574   for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
1575     Node* n = cl->fast_out(i);
1576     if (n->Opcode() == Op_Phi) {
1577       assert(iv == NULL, "Too many phis" );
1578       iv = n;
1579     }
1580   }
1581   assert(iv == cl->phi(), "Wrong phi" );
1582 #endif
1583   // Replace the phi at loop head with the final value of the last
1584   // iteration.  Then the CountedLoopEnd will collapse (backedge never
1585   // taken) and all loop-invariant uses of the exit values will be correct.
1586   Node *phi = cl->phi();
1587   Node *final = new (phase->C, 3) SubINode( cl->limit(), cl->stride() );
1588   phase->register_new_node(final,cl->in(LoopNode::EntryControl));
1589   phase->_igvn.hash_delete(phi);
1590   phase->_igvn.subsume_node(phi,final);
1591   phase->C->set_major_progress();
1592   return true;
1593 }
1594 
1595 
1596 //=============================================================================
1597 //------------------------------iteration_split_impl---------------------------
1598 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
1599   // Check and remove empty loops (spam micro-benchmarks)
1600   if( policy_do_remove_empty_loop(phase) )
1601     return true;  // Here we removed an empty loop
1602 
1603   bool should_peel = policy_peeling(phase); // Should we peel?
1604 
1605   bool should_unswitch = policy_unswitching(phase);
1606 
1607   // Non-counted loops may be peeled; exactly 1 iteration is peeled.
1608   // This removes loop-invariant tests (usually null checks).
1609   if( !_head->is_CountedLoop() ) { // Non-counted loop
1610     if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
1611       // Partial peel succeeded so terminate this round of loop opts
1612       return false;
1613     }
1614     if( should_peel ) {            // Should we peel?
1615 #ifndef PRODUCT
1616       if (PrintOpto) tty->print_cr("should_peel");
1617 #endif
1618       phase->do_peeling(this,old_new);
1619     } else if( should_unswitch ) {
1620       phase->do_unswitching(this, old_new);
1621     }
1622     return true;
1623   }
1624   CountedLoopNode *cl = _head->as_CountedLoop();
1625 
1626   if( !cl->loopexit() ) return true; // Ignore various kinds of broken loops
1627 
1628   // Do nothing special to pre- and post- loops
1629   if( cl->is_pre_loop() || cl->is_post_loop() ) return true;
1630 
1631   // Compute loop trip count from profile data
1632   compute_profile_trip_cnt(phase);
1633 
1634   // Before attempting fancy unrolling, RCE or alignment, see if we want
1635   // to completely unroll this loop or do loop unswitching.
1636   if( cl->is_normal_loop() ) {
1637     if (should_unswitch) {
1638       phase->do_unswitching(this, old_new);
1639       return true;
1640     }
1641     bool should_maximally_unroll =  policy_maximally_unroll(phase);
1642     if( should_maximally_unroll ) {
1643       // Here we did some unrolling and peeling.  Eventually we will
1644       // completely unroll this loop and it will no longer be a loop.
1645       phase->do_maximally_unroll(this,old_new);
1646       return true;
1647     }
1648   }
1649 
1650 
1651   // Counted loops may be peeled, may need some iterations run up
1652   // front for RCE, and may want to align loop refs to a cache
1653   // line.  Thus we clone a full loop up front whose trip count is
1654   // at least 1 (if peeling), but may be several more.
1655 
1656   // The main loop will start cache-line aligned with at least 1
1657   // iteration of the unrolled body (zero-trip test required) and
1658   // will have some range checks removed.
1659 
1660   // A post-loop will finish any odd iterations (leftover after
1661   // unrolling), plus any needed for RCE purposes.
1662 
1663   bool should_unroll = policy_unroll(phase);
1664 
1665   bool should_rce = policy_range_check(phase);
1666 
1667   bool should_align = policy_align(phase);
1668 
1669   // If not RCE'ing (iteration splitting) or Aligning, then we do not
1670   // need a pre-loop.  We may still need to peel an initial iteration but
1671   // we will not be needing an unknown number of pre-iterations.
1672   //
1673   // Basically, if may_rce_align reports FALSE first time through,
1674   // we will not be able to later do RCE or Aligning on this loop.
1675   bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
1676 
1677   // If we have any of these conditions (RCE, alignment, unrolling) met, then
1678   // we switch to the pre-/main-/post-loop model.  This model also covers
1679   // peeling.
1680   if( should_rce || should_align || should_unroll ) {
1681     if( cl->is_normal_loop() )  // Convert to 'pre/main/post' loops
1682       phase->insert_pre_post_loops(this,old_new, !may_rce_align);
1683 
1684     // Adjust the pre- and main-loop limits to let the pre and post loops run
1685     // with full checks, but the main-loop with no checks.  Remove said
1686     // checks from the main body.
1687     if( should_rce )
1688       phase->do_range_check(this,old_new);
1689 
1690     // Double loop body for unrolling.  Adjust the minimum-trip test (will do
1691     // twice as many iterations as before) and the main body limit (only do
1692     // an even number of trips).  If we are peeling, we might enable some RCE
1693     // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
1694     // peeling.
1695       if( should_unroll && !should_peel )
1696         phase->do_unroll(this,old_new, true);
1697 
1698     // Adjust the pre-loop limits to align the main body
1699     // iterations.
1700     if( should_align )
1701       Unimplemented();
1702 
1703   } else {                      // Else we have an unchanged counted loop
1704     if( should_peel )           // Might want to peel but do nothing else
1705       phase->do_peeling(this,old_new);
1706   }
1707   return true;
1708 }
1709 
1710 
1711 //=============================================================================
1712 //------------------------------iteration_split--------------------------------
1713 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
1714   // Recursively iteration split nested loops
1715   if( _child && !_child->iteration_split( phase, old_new ))
1716     return false;
1717 
1718   // Clean out prior deadwood
1719   DCE_loop_body();
1720 
1721 
1722   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
1723   // Replace with a 1-in-10 exit guess.
1724   if( _parent /*not the root loop*/ &&
1725       !_irreducible &&
1726       // Also ignore the occasional dead backedge
1727       !tail()->is_top() ) {
1728     adjust_loop_exit_prob(phase);
1729   }
1730 
1731 
1732   // Gate unrolling, RCE and peeling efforts.
1733   if( !_child &&                // If not an inner loop, do not split
1734       !_irreducible &&
1735       _allow_optimizations &&
1736       !tail()->is_top() ) {     // Also ignore the occasional dead backedge
1737     if (!_has_call) {
1738         if (!iteration_split_impl( phase, old_new )) {
1739           return false;
1740         }
1741     } else if (policy_unswitching(phase)) {
1742       phase->do_unswitching(this, old_new);
1743     }
1744   }
1745 
1746   // Minor offset re-organization to remove loop-fallout uses of
1747   // trip counter.
1748   if( _head->is_CountedLoop() ) phase->reorg_offsets( this );
1749   if( _next && !_next->iteration_split( phase, old_new ))
1750     return false;
1751   return true;
1752 }
1753 
1754 //-------------------------------is_uncommon_trap_proj----------------------------
1755 // Return true if proj is the form of "proj->[region->..]call_uct"
1756 bool PhaseIdealLoop::is_uncommon_trap_proj(ProjNode* proj, bool must_reason_predicate) {
1757   int path_limit = 10;
1758   assert(proj, "invalid argument");
1759   Node* out = proj;
1760   for (int ct = 0; ct < path_limit; ct++) {
1761     out = out->unique_ctrl_out();
1762     if (out == NULL || out->is_Root() || out->is_Start())
1763       return false;
1764     if (out->is_CallStaticJava()) {
1765       int req = out->as_CallStaticJava()->uncommon_trap_request();
1766       if (req != 0) {
1767         Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(req);
1768         if (!must_reason_predicate || reason == Deoptimization::Reason_predicate){
1769            return true;
1770         }
1771       }
1772       return false; // don't do further after call
1773     }
1774   }
1775   return false;
1776 }
1777 
1778 //-------------------------------is_uncommon_trap_if_pattern-------------------------
1779 // Return true  for "if(test)-> proj -> ...
1780 //                          |
1781 //                          V
1782 //                      other_proj->[region->..]call_uct"
1783 //
1784 // "must_reason_predicate" means the uct reason must be Reason_predicate
1785 bool PhaseIdealLoop::is_uncommon_trap_if_pattern(ProjNode *proj, bool must_reason_predicate) {
1786   Node *in0 = proj->in(0);
1787   if (!in0->is_If()) return false;
1788   // Variation of a dead If node.
1789   if (in0->outcnt() < 2)  return false;
1790   IfNode* iff = in0->as_If();
1791 
1792   // we need "If(Conv2B(Opaque1(...)))" pattern for must_reason_predicate
1793   if (must_reason_predicate) {
1794     if (iff->in(1)->Opcode() != Op_Conv2B ||
1795        iff->in(1)->in(1)->Opcode() != Op_Opaque1) {
1796       return false;
1797     }
1798   }
1799 
1800   ProjNode* other_proj = iff->proj_out(1-proj->_con)->as_Proj();
1801   return is_uncommon_trap_proj(other_proj, must_reason_predicate);
1802 }
1803 
1804 //------------------------------create_new_if_for_predicate------------------------
1805 // create a new if above the uct_if_pattern for the predicate to be promoted.
1806 //
1807 //          before                                after
1808 //        ----------                           ----------
1809 //           ctrl                                 ctrl
1810 //            |                                     |
1811 //            |                                     |
1812 //            v                                     v
1813 //           iff                                 new_iff
1814 //          /    \                                /      \
1815 //         /      \                              /        \
1816 //        v        v                            v          v
1817 //  uncommon_proj cont_proj                   if_uct     if_cont
1818 // \      |        |                           |          |
1819 //  \     |        |                           |          |
1820 //   v    v        v                           |          v
1821 //     rgn       loop                          |         iff
1822 //      |                                      |        /     \
1823 //      |                                      |       /       \
1824 //      v                                      |      v         v
1825 // uncommon_trap                               | uncommon_proj cont_proj
1826 //                                           \  \    |           |
1827 //                                            \  \   |           |
1828 //                                             v  v  v           v
1829 //                                               rgn           loop
1830 //                                                |
1831 //                                                |
1832 //                                                v
1833 //                                           uncommon_trap
1834 //
1835 //
1836 // We will create a region to guard the uct call if there is no one there.
1837 // The true projecttion (if_cont) of the new_iff is returned.
1838 ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj) {
1839   assert(is_uncommon_trap_if_pattern(cont_proj, true), "must be a uct if pattern!");
1840   IfNode* iff = cont_proj->in(0)->as_If();
1841 
1842   ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
1843   Node     *rgn   = uncommon_proj->unique_ctrl_out();
1844   assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
1845 
1846   if (!rgn->is_Region()) { // create a region to guard the call
1847     assert(rgn->is_Call(), "must be call uct");
1848     CallNode* call = rgn->as_Call();
1849     rgn = new (C, 1) RegionNode(1);
1850     _igvn.set_type(rgn, rgn->bottom_type());
1851     rgn->add_req(uncommon_proj);
1852     set_idom(rgn, idom(uncommon_proj), dom_depth(uncommon_proj)+1);
1853     _igvn.hash_delete(call);
1854     call->set_req(0, rgn);
1855   }
1856 
1857   // Create new_iff
1858   uint  iffdd  = dom_depth(iff);
1859   IdealLoopTree* lp = get_loop(iff);
1860   IfNode *new_iff = new (C, 2) IfNode(iff->in(0), NULL, iff->_prob, iff->_fcnt);
1861   register_node(new_iff, lp, idom(iff), iffdd);
1862   Node *if_cont = new (C, 1) IfTrueNode(new_iff);
1863   Node *if_uct  = new (C, 1) IfFalseNode(new_iff);
1864   if (cont_proj->is_IfFalse()) {
1865     // Swap
1866     Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
1867   }
1868   register_node(if_cont, lp, new_iff, iffdd);
1869   register_node(if_uct, get_loop(rgn), new_iff, iffdd);
1870 
1871   // if_cont to iff
1872   _igvn.hash_delete(iff);
1873   iff->set_req(0, if_cont);
1874   set_idom(iff, if_cont, dom_depth(iff));
1875 
1876   // if_uct to rgn
1877   _igvn.hash_delete(rgn);
1878   rgn->add_req(if_uct);
1879   Node* ridom = idom(rgn);
1880   Node* nrdom = dom_lca(ridom, new_iff);
1881   set_idom(rgn, nrdom, dom_depth(rgn));
1882 
1883   // rgn must have no phis
1884   assert(!rgn->as_Region()->has_phi(), "region must have no phis");
1885 
1886   return if_cont->as_Proj();
1887 }
1888 
1889 //------------------------------find_predicate_insertion_point--------------------------
1890 // Find a good location to insert a predicate
1891 ProjNode* PhaseIdealLoop::find_predicate_insertion_point(Node* start_c) {
1892   if (start_c == C->root() || !start_c->is_Proj())
1893     return NULL;
1894   if (is_uncommon_trap_if_pattern(start_c->as_Proj(), true/*Reason_Predicate*/)) {
1895     return start_c->as_Proj();
1896   }
1897   return NULL;
1898 }
1899 
1900 //------------------------------Invariance-----------------------------------
1901 // Helper class for loop_predication_impl to compute invariance on the fly and
1902 // clone invariants.
1903 class Invariance : public StackObj {
1904   VectorSet _visited, _invariant;
1905   Node_Stack _stack;
1906   VectorSet _clone_visited;
1907   Node_List _old_new; // map of old to new (clone)
1908   IdealLoopTree* _lpt;
1909   PhaseIdealLoop* _phase;
1910 
1911   // Helper function to set up the invariance for invariance computation
1912   // If n is a known invariant, set up directly. Otherwise, look up the
1913   // the possibility to push n onto the stack for further processing.
1914   void visit(Node* use, Node* n) {
1915     if (_lpt->is_invariant(n)) { // known invariant
1916       _invariant.set(n->_idx);
1917     } else if (!n->is_CFG()) {
1918       Node *n_ctrl = _phase->ctrl_or_self(n);
1919       Node *u_ctrl = _phase->ctrl_or_self(use); // self if use is a CFG
1920       if (_phase->is_dominator(n_ctrl, u_ctrl)) {
1921         _stack.push(n, n->in(0) == NULL ? 1 : 0);
1922       }
1923     }
1924   }
1925 
1926   // Compute invariance for "the_node" and (possibly) all its inputs recursively
1927   // on the fly
1928   void compute_invariance(Node* n) {
1929     assert(_visited.test(n->_idx), "must be");
1930     visit(n, n);
1931     while (_stack.is_nonempty()) {
1932       Node*  n = _stack.node();
1933       uint idx = _stack.index();
1934       if (idx == n->req()) { // all inputs are processed
1935         _stack.pop();
1936         // n is invariant if it's inputs are all invariant
1937         bool all_inputs_invariant = true;
1938         for (uint i = 0; i < n->req(); i++) {
1939           Node* in = n->in(i);
1940           if (in == NULL) continue;
1941           assert(_visited.test(in->_idx), "must have visited input");
1942           if (!_invariant.test(in->_idx)) { // bad guy
1943             all_inputs_invariant = false;
1944             break;
1945           }
1946         }
1947         if (all_inputs_invariant) {
1948           _invariant.set(n->_idx); // I am a invariant too
1949         }
1950       } else { // process next input
1951         _stack.set_index(idx + 1);
1952         Node* m = n->in(idx);
1953         if (m != NULL && !_visited.test_set(m->_idx)) {
1954           visit(n, m);
1955         }
1956       }
1957     }
1958   }
1959 
1960   // Helper function to set up _old_new map for clone_nodes.
1961   // If n is a known invariant, set up directly ("clone" of n == n).
1962   // Otherwise, push n onto the stack for real cloning.
1963   void clone_visit(Node* n) {
1964     assert(_invariant.test(n->_idx), "must be invariant");
1965     if (_lpt->is_invariant(n)) { // known invariant
1966       _old_new.map(n->_idx, n);
1967     } else{ // to be cloned
1968       assert (!n->is_CFG(), "should not see CFG here");
1969       _stack.push(n, n->in(0) == NULL ? 1 : 0);
1970     }
1971   }
1972 
1973   // Clone "n" and (possibly) all its inputs recursively
1974   void clone_nodes(Node* n, Node* ctrl) {
1975     clone_visit(n);
1976     while (_stack.is_nonempty()) {
1977       Node*  n = _stack.node();
1978       uint idx = _stack.index();
1979       if (idx == n->req()) { // all inputs processed, clone n!
1980         _stack.pop();
1981         // clone invariant node
1982         Node* n_cl = n->clone();
1983         _old_new.map(n->_idx, n_cl);
1984         _phase->register_new_node(n_cl, ctrl);
1985         for (uint i = 0; i < n->req(); i++) {
1986           Node* in = n_cl->in(i);
1987           if (in == NULL) continue;
1988           n_cl->set_req(i, _old_new[in->_idx]);
1989         }
1990       } else { // process next input
1991         _stack.set_index(idx + 1);
1992         Node* m = n->in(idx);
1993         if (m != NULL && !_clone_visited.test_set(m->_idx)) {
1994           clone_visit(m); // visit the input
1995         }
1996       }
1997     }
1998   }
1999 
2000  public:
2001   Invariance(Arena* area, IdealLoopTree* lpt) :
2002     _lpt(lpt), _phase(lpt->_phase),
2003     _visited(area), _invariant(area), _stack(area, 10 /* guess */),
2004     _clone_visited(area), _old_new(area)
2005   {}
2006 
2007   // Map old to n for invariance computation and clone
2008   void map_ctrl(Node* old, Node* n) {
2009     assert(old->is_CFG() && n->is_CFG(), "must be");
2010     _old_new.map(old->_idx, n); // "clone" of old is n
2011     _invariant.set(old->_idx);  // old is invariant
2012     _clone_visited.set(old->_idx);
2013   }
2014 
2015   // Driver function to compute invariance
2016   bool is_invariant(Node* n) {
2017     if (!_visited.test_set(n->_idx))
2018       compute_invariance(n);
2019     return (_invariant.test(n->_idx) != 0);
2020   }
2021 
2022   // Driver function to clone invariant
2023   Node* clone(Node* n, Node* ctrl) {
2024     assert(ctrl->is_CFG(), "must be");
2025     assert(_invariant.test(n->_idx), "must be an invariant");
2026     if (!_clone_visited.test(n->_idx))
2027       clone_nodes(n, ctrl);
2028     return _old_new[n->_idx];
2029   }
2030 };
2031 
2032 //------------------------------is_range_check_if -----------------------------------
2033 // Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format
2034 // Note: this function is particularly designed for loop predication. We require load_range
2035 //       and offset to be loop invariant computed on the fly by "invar"
2036 bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const {
2037   if (!is_loop_exit(iff)) {
2038     return false;
2039   }
2040   if (!iff->in(1)->is_Bool()) {
2041     return false;
2042   }
2043   const BoolNode *bol = iff->in(1)->as_Bool();
2044   if (bol->_test._test != BoolTest::lt) {
2045     return false;
2046   }
2047   if (!bol->in(1)->is_Cmp()) {
2048     return false;
2049   }
2050   const CmpNode *cmp = bol->in(1)->as_Cmp();
2051   if (cmp->Opcode() != Op_CmpU ) {
2052     return false;
2053   }
2054   if (cmp->in(2)->Opcode() != Op_LoadRange) {
2055     return false;
2056   }
2057   LoadRangeNode* lr = (LoadRangeNode*)cmp->in(2);
2058   if (!invar.is_invariant(lr)) { // loadRange must be invariant
2059     return false;
2060   }
2061   Node *iv     = _head->as_CountedLoop()->phi();
2062   int   scale  = 0;
2063   Node *offset = NULL;
2064   if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) {
2065     return false;
2066   }
2067   if(offset && !invar.is_invariant(offset)) { // offset must be invariant
2068     return false;
2069   }
2070   return true;
2071 }
2072 
2073 //------------------------------rc_predicate-----------------------------------
2074 // Create a range check predicate
2075 //
2076 // for (i = init; i < limit; i += stride) {
2077 //    a[scale*i+offset]
2078 // }
2079 //
2080 // Compute max(scale*i + offset) for init <= i < limit and build the predicate
2081 // as "max(scale*i + offset) u< a.length".
2082 //
2083 // There are two cases for max(scale*i + offset):
2084 // (1) stride*scale > 0
2085 //   max(scale*i + offset) = scale*(limit-stride) + offset
2086 // (2) stride*scale < 0
2087 //   max(scale*i + offset) = scale*init + offset
2088 BoolNode* PhaseIdealLoop::rc_predicate(Node* ctrl,
2089                                        int scale, Node* offset,
2090                                        Node* init, Node* limit, Node* stride,
2091                                        Node* range) {
2092   Node* max_idx_expr  = init;
2093   int stride_con = stride->get_int();
2094   if ((stride_con > 0) == (scale > 0)) {
2095     max_idx_expr = new (C, 3) SubINode(limit, stride);
2096     register_new_node(max_idx_expr, ctrl);
2097   }
2098 
2099   if (scale != 1) {
2100     ConNode* con_scale = _igvn.intcon(scale);
2101     max_idx_expr = new (C, 3) MulINode(max_idx_expr, con_scale);
2102     register_new_node(max_idx_expr, ctrl);
2103   }
2104 
2105   if (offset && (!offset->is_Con() || offset->get_int() != 0)){
2106     max_idx_expr = new (C, 3) AddINode(max_idx_expr, offset);
2107     register_new_node(max_idx_expr, ctrl);
2108   }
2109 
2110   CmpUNode* cmp = new (C, 3) CmpUNode(max_idx_expr, range);
2111   register_new_node(cmp, ctrl);
2112   BoolNode* bol = new (C, 2) BoolNode(cmp, BoolTest::lt);
2113   register_new_node(bol, ctrl);
2114   return bol;
2115 }
2116 
2117 //------------------------------ loop_predication_impl--------------------------
2118 // Insert loop predicates for null checks and range checks
2119 bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) {
2120   if (!UseLoopPredicate) return false;
2121 
2122   if (!loop->_head->is_Loop()) {
2123     // Could be a simple region when irreducible loops are present.
2124     return false;
2125   }
2126 
2127   CountedLoopNode *cl = NULL;
2128   if (loop->_head->is_CountedLoop()) {
2129     cl = loop->_head->as_CountedLoop();
2130     // do nothing for iteration-splitted loops
2131     if (!cl->is_normal_loop()) return false;
2132   }
2133 
2134   // Too many traps seen?
2135   bool tmt = C->too_many_traps(C->method(), 0, Deoptimization::Reason_predicate);
2136   int tc = C->trap_count(Deoptimization::Reason_predicate);
2137   if (tmt || tc > 0) {
2138     if (TraceLoopPredicate) {
2139       tty->print_cr("too many predicate traps: %d", tc);
2140       C->method()->print(); // which method has too many predicate traps
2141       tty->print_cr("");
2142     }
2143     return false;
2144   }
2145 
2146   LoopNode *lpn  = loop->_head->as_Loop();
2147   Node* entry = lpn->in(LoopNode::EntryControl);
2148 
2149   ProjNode *predicate_proj = find_predicate_insertion_point(entry);
2150   if (!predicate_proj){
2151 #ifndef PRODUCT
2152     if (TraceLoopPredicate) {
2153       tty->print("missing predicate:");
2154       loop->dump_head();
2155     }
2156 #endif
2157     return false;
2158   }
2159 
2160   ConNode* zero = _igvn.intcon(0);
2161   set_ctrl(zero, C->root());
2162   Node *cond_false = new (C, 2) Conv2BNode(zero);
2163   register_new_node(cond_false, C->root());
2164   ConNode* one = _igvn.intcon(1);
2165   set_ctrl(one, C->root());
2166   Node *cond_true = new (C, 2) Conv2BNode(one);
2167   register_new_node(cond_true, C->root());
2168 
2169   ResourceArea *area = Thread::current()->resource_area();
2170   Invariance invar(area, loop);
2171 
2172   // Create list of if-projs such that a newer proj dominates all older
2173   // projs in the list, and they all dominate loop->tail()
2174   Node_List if_proj_list(area);
2175   LoopNode *head  = loop->_head->as_Loop();
2176   Node *current_proj = loop->tail(); //start from tail
2177   while ( current_proj != head ) {
2178     if (loop == get_loop(current_proj) && // still in the loop ?
2179         current_proj->is_Proj()        && // is a projection  ?
2180         current_proj->in(0)->Opcode() == Op_If) { // is a if projection ?
2181       if_proj_list.push(current_proj);
2182     }
2183     current_proj = idom(current_proj);
2184   }
2185 
2186   bool hoisted = false; // true if at least one proj is promoted
2187   while (if_proj_list.size() > 0) {
2188     // Following are changed to nonnull when a predicate can be hoisted
2189     ProjNode* new_predicate_proj = NULL;
2190     BoolNode* new_predicate_bol   = NULL;
2191 
2192     ProjNode* proj = if_proj_list.pop()->as_Proj();
2193     IfNode*   iff  = proj->in(0)->as_If();
2194 
2195     if (!is_uncommon_trap_if_pattern(proj)) {
2196       if (loop->is_loop_exit(iff)) {
2197         // stop processing the remaining projs in the list because the execution of them
2198         // depends on the condition of "iff" (iff->in(1)).
2199         break;
2200       } else {
2201         // Both arms are inside the loop. There are two cases:
2202         // (1) there is one backward branch. In this case, any remaining proj
2203         //     in the if_proj list post-dominates "iff". So, the condition of "iff"
2204         //     does not determine the execution the remining projs directly, and we
2205         //     can safely continue.
2206         // (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj"
2207         //     does not dominate loop->tail(), so it can not be in the if_proj list.
2208         continue;
2209       }
2210     }
2211 
2212     Node*     test = iff->in(1);
2213     if (!test->is_Bool()){ //Conv2B, ...
2214       continue;
2215     }
2216     BoolNode* bol = test->as_Bool();
2217     if (invar.is_invariant(bol)) {
2218       // Invariant test
2219       new_predicate_proj = create_new_if_for_predicate(predicate_proj);
2220       Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0);
2221       new_predicate_bol  = invar.clone(bol, ctrl)->as_Bool();
2222       if (TraceLoopPredicate) tty->print("invariant");
2223     } else if (cl != NULL && loop->is_range_check_if(iff, this, invar)) {
2224       // Range check (only for counted loops)
2225       new_predicate_proj = create_new_if_for_predicate(predicate_proj);
2226       Node *ctrl = new_predicate_proj->in(0)->as_If()->in(0);
2227       const Node*    cmp    = bol->in(1)->as_Cmp();
2228       Node*          idx    = cmp->in(1);
2229       assert(!invar.is_invariant(idx), "index is variant");
2230       assert(cmp->in(2)->Opcode() == Op_LoadRange, "must be");
2231       LoadRangeNode* ld_rng = (LoadRangeNode*)cmp->in(2); // LoadRangeNode
2232       assert(invar.is_invariant(ld_rng), "load range must be invariant");
2233       ld_rng = (LoadRangeNode*)invar.clone(ld_rng, ctrl);
2234       int scale    = 1;
2235       Node* offset = zero;
2236       bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset);
2237       assert(ok, "must be index expression");
2238       if (offset && offset != zero) {
2239         assert(invar.is_invariant(offset), "offset must be loop invariant");
2240         offset = invar.clone(offset, ctrl);
2241       }
2242       Node* init    = cl->init_trip();
2243       Node* limit   = cl->limit();
2244       Node* stride  = cl->stride();
2245       new_predicate_bol = rc_predicate(ctrl, scale, offset, init, limit, stride, ld_rng);
2246       if (TraceLoopPredicate) tty->print("range check");
2247     }
2248 
2249     if (new_predicate_proj == NULL) {
2250       // The other proj of the "iff" is a uncommon trap projection, and we can assume
2251       // the other proj will not be executed ("executed" means uct raised).
2252       continue;
2253     } else {
2254       // Success - attach condition (new_predicate_bol) to predicate if
2255       invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate
2256       IfNode* new_iff = new_predicate_proj->in(0)->as_If();
2257 
2258       // Negate test if necessary
2259       if (proj->_con != predicate_proj->_con) {
2260         new_predicate_bol = new (C, 2) BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate());
2261         register_new_node(new_predicate_bol, new_iff->in(0));
2262         if (TraceLoopPredicate) tty->print_cr(" if negated: %d", iff->_idx);
2263       } else {
2264         if (TraceLoopPredicate) tty->print_cr(" if: %d", iff->_idx);
2265       }
2266 
2267       _igvn.hash_delete(new_iff);
2268       new_iff->set_req(1, new_predicate_bol);
2269 
2270       _igvn.hash_delete(iff);
2271       iff->set_req(1, proj->is_IfFalse() ? cond_false : cond_true);
2272 
2273       Node* ctrl = new_predicate_proj; // new control
2274       ProjNode* dp = proj;     // old control
2275       assert(get_loop(dp) == loop, "guarenteed at the time of collecting proj");
2276       // Find nodes (depends only on the test) off the surviving projection;
2277       // move them outside the loop with the control of proj_clone
2278       for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
2279         Node* cd = dp->fast_out(i); // Control-dependent node
2280         if (cd->depends_only_on_test()) {
2281           assert(cd->in(0) == dp, "");
2282           _igvn.hash_delete(cd);
2283           cd->set_req(0, ctrl); // ctrl, not NULL
2284           set_early_ctrl(cd);
2285           _igvn._worklist.push(cd);
2286           IdealLoopTree *new_loop = get_loop(get_ctrl(cd));
2287           if (new_loop != loop) {
2288             if (!loop->_child) loop->_body.yank(cd);
2289             if (!new_loop->_child ) new_loop->_body.push(cd);
2290           }
2291           --i;
2292           --imax;
2293         }
2294       }
2295 
2296       hoisted = true;
2297       C->set_major_progress();
2298     }
2299   } // end while
2300 
2301 #ifndef PRODUCT
2302     // report that the loop predication has been actually performed
2303     // for this loop
2304     if (TraceLoopPredicate && hoisted) {
2305       tty->print("Loop Predication Performed:");
2306       loop->dump_head();
2307     }
2308 #endif
2309 
2310   return hoisted;
2311 }
2312 
2313 //------------------------------loop_predication--------------------------------
2314 // driver routine for loop predication optimization
2315 bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) {
2316   bool hoisted = false;
2317   // Recursively promote predicates
2318   if ( _child ) {
2319     hoisted = _child->loop_predication( phase);
2320   }
2321 
2322   // self
2323   if (!_irreducible && !tail()->is_top()) {
2324     hoisted |= phase->loop_predication_impl(this);
2325   }
2326 
2327   if ( _next ) { //sibling
2328     hoisted |= _next->loop_predication( phase);
2329   }
2330 
2331   return hoisted;
2332 }
--- EOF ---