1 /*
   2  * Copyright (c) 2000, 2012, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "compiler/compileLog.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "opto/addnode.hpp"
  29 #include "opto/callnode.hpp"
  30 #include "opto/connode.hpp"
  31 #include "opto/divnode.hpp"
  32 #include "opto/loopnode.hpp"
  33 #include "opto/mulnode.hpp"
  34 #include "opto/rootnode.hpp"
  35 #include "opto/runtime.hpp"
  36 #include "opto/subnode.hpp"
  37 
  38 //------------------------------is_loop_exit-----------------------------------
  39 // Given an IfNode, return the loop-exiting projection or NULL if both
  40 // arms remain in the loop.
  41 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
  42   if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
  43   PhaseIdealLoop *phase = _phase;
  44   // Test is an IfNode, has 2 projections.  If BOTH are in the loop
  45   // we need loop unswitching instead of peeling.
  46   if( !is_member(phase->get_loop( iff->raw_out(0) )) )
  47     return iff->raw_out(0);
  48   if( !is_member(phase->get_loop( iff->raw_out(1) )) )
  49     return iff->raw_out(1);
  50   return NULL;
  51 }
  52 
  53 
  54 //=============================================================================
  55 
  56 
  57 //------------------------------record_for_igvn----------------------------
  58 // Put loop body on igvn work list
  59 void IdealLoopTree::record_for_igvn() {
  60   for( uint i = 0; i < _body.size(); i++ ) {
  61     Node *n = _body.at(i);
  62     _phase->_igvn._worklist.push(n);
  63   }
  64 }
  65 
  66 //------------------------------compute_exact_trip_count-----------------------
  67 // Compute loop exact trip count if possible. Do not recalculate trip count for
  68 // split loops (pre-main-post) which have their limits and inits behind Opaque node.
  69 void IdealLoopTree::compute_exact_trip_count( PhaseIdealLoop *phase ) {
  70   if (!_head->as_Loop()->is_valid_counted_loop()) {
  71     return;
  72   }
  73   CountedLoopNode* cl = _head->as_CountedLoop();
  74   // Trip count may become nonexact for iteration split loops since
  75   // RCE modifies limits. Note, _trip_count value is not reset since
  76   // it is used to limit unrolling of main loop.
  77   cl->set_nonexact_trip_count();
  78 
  79   // Loop's test should be part of loop.
  80   if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
  81     return; // Infinite loop
  82 
  83 #ifdef ASSERT
  84   BoolTest::mask bt = cl->loopexit()->test_trip();
  85   assert(bt == BoolTest::lt || bt == BoolTest::gt ||
  86          bt == BoolTest::ne, "canonical test is expected");
  87 #endif
  88 
  89   Node* init_n = cl->init_trip();
  90   Node* limit_n = cl->limit();
  91   if (init_n  != NULL &&  init_n->is_Con() &&
  92       limit_n != NULL && limit_n->is_Con()) {
  93     // Use longs to avoid integer overflow.
  94     int stride_con  = cl->stride_con();
  95     jlong init_con   = cl->init_trip()->get_int();
  96     jlong limit_con  = cl->limit()->get_int();
  97     int stride_m    = stride_con - (stride_con > 0 ? 1 : -1);
  98     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
  99     if (trip_count > 0 && (julong)trip_count < (julong)max_juint) {
 100       // Set exact trip count.
 101       cl->set_exact_trip_count((uint)trip_count);
 102     }
 103   }
 104 }
 105 
 106 //------------------------------compute_profile_trip_cnt----------------------------
 107 // Compute loop trip count from profile data as
 108 //    (backedge_count + loop_exit_count) / loop_exit_count
 109 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
 110   if (!_head->is_CountedLoop()) {
 111     return;
 112   }
 113   CountedLoopNode* head = _head->as_CountedLoop();
 114   if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
 115     return; // Already computed
 116   }
 117   float trip_cnt = (float)max_jint; // default is big
 118 
 119   Node* back = head->in(LoopNode::LoopBackControl);
 120   while (back != head) {
 121     if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
 122         back->in(0) &&
 123         back->in(0)->is_If() &&
 124         back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
 125         back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
 126       break;
 127     }
 128     back = phase->idom(back);
 129   }
 130   if (back != head) {
 131     assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
 132            back->in(0), "if-projection exists");
 133     IfNode* back_if = back->in(0)->as_If();
 134     float loop_back_cnt = back_if->_fcnt * back_if->_prob;
 135 
 136     // Now compute a loop exit count
 137     float loop_exit_cnt = 0.0f;
 138     for( uint i = 0; i < _body.size(); i++ ) {
 139       Node *n = _body[i];
 140       if( n->is_If() ) {
 141         IfNode *iff = n->as_If();
 142         if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
 143           Node *exit = is_loop_exit(iff);
 144           if( exit ) {
 145             float exit_prob = iff->_prob;
 146             if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
 147             if (exit_prob > PROB_MIN) {
 148               float exit_cnt = iff->_fcnt * exit_prob;
 149               loop_exit_cnt += exit_cnt;
 150             }
 151           }
 152         }
 153       }
 154     }
 155     if (loop_exit_cnt > 0.0f) {
 156       trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
 157     } else {
 158       // No exit count so use
 159       trip_cnt = loop_back_cnt;
 160     }
 161   }
 162 #ifndef PRODUCT
 163   if (TraceProfileTripCount) {
 164     tty->print_cr("compute_profile_trip_cnt  lp: %d cnt: %f\n", head->_idx, trip_cnt);
 165   }
 166 #endif
 167   head->set_profile_trip_cnt(trip_cnt);
 168 }
 169 
 170 //---------------------is_invariant_addition-----------------------------
 171 // Return nonzero index of invariant operand for an Add or Sub
 172 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
 173 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
 174   int op = n->Opcode();
 175   if (op == Op_AddI || op == Op_SubI) {
 176     bool in1_invar = this->is_invariant(n->in(1));
 177     bool in2_invar = this->is_invariant(n->in(2));
 178     if (in1_invar && !in2_invar) return 1;
 179     if (!in1_invar && in2_invar) return 2;
 180   }
 181   return 0;
 182 }
 183 
 184 //---------------------reassociate_add_sub-----------------------------
 185 // Reassociate invariant add and subtract expressions:
 186 //
 187 // inv1 + (x + inv2)  =>  ( inv1 + inv2) + x
 188 // (x + inv2) + inv1  =>  ( inv1 + inv2) + x
 189 // inv1 + (x - inv2)  =>  ( inv1 - inv2) + x
 190 // inv1 - (inv2 - x)  =>  ( inv1 - inv2) + x
 191 // (x + inv2) - inv1  =>  (-inv1 + inv2) + x
 192 // (x - inv2) + inv1  =>  ( inv1 - inv2) + x
 193 // (x - inv2) - inv1  =>  (-inv1 - inv2) + x
 194 // inv1 + (inv2 - x)  =>  ( inv1 + inv2) - x
 195 // inv1 - (x - inv2)  =>  ( inv1 + inv2) - x
 196 // (inv2 - x) + inv1  =>  ( inv1 + inv2) - x
 197 // (inv2 - x) - inv1  =>  (-inv1 + inv2) - x
 198 // inv1 - (x + inv2)  =>  ( inv1 - inv2) - x
 199 //
 200 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
 201   if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
 202   if (is_invariant(n1)) return NULL;
 203   int inv1_idx = is_invariant_addition(n1, phase);
 204   if (!inv1_idx) return NULL;
 205   // Don't mess with add of constant (igvn moves them to expression tree root.)
 206   if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
 207   Node* inv1 = n1->in(inv1_idx);
 208   Node* n2 = n1->in(3 - inv1_idx);
 209   int inv2_idx = is_invariant_addition(n2, phase);
 210   if (!inv2_idx) return NULL;
 211   Node* x    = n2->in(3 - inv2_idx);
 212   Node* inv2 = n2->in(inv2_idx);
 213 
 214   bool neg_x    = n2->is_Sub() && inv2_idx == 1;
 215   bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
 216   bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
 217   if (n1->is_Sub() && inv1_idx == 1) {
 218     neg_x    = !neg_x;
 219     neg_inv2 = !neg_inv2;
 220   }
 221   Node* inv1_c = phase->get_ctrl(inv1);
 222   Node* inv2_c = phase->get_ctrl(inv2);
 223   Node* n_inv1;
 224   if (neg_inv1) {
 225     Node *zero = phase->_igvn.intcon(0);
 226     phase->set_ctrl(zero, phase->C->root());
 227     n_inv1 = new (phase->C) SubINode(zero, inv1);
 228     phase->register_new_node(n_inv1, inv1_c);
 229   } else {
 230     n_inv1 = inv1;
 231   }
 232   Node* inv;
 233   if (neg_inv2) {
 234     inv = new (phase->C) SubINode(n_inv1, inv2);
 235   } else {
 236     inv = new (phase->C) AddINode(n_inv1, inv2);
 237   }
 238   phase->register_new_node(inv, phase->get_early_ctrl(inv));
 239 
 240   Node* addx;
 241   if (neg_x) {
 242     addx = new (phase->C) SubINode(inv, x);
 243   } else {
 244     addx = new (phase->C) AddINode(x, inv);
 245   }
 246   phase->register_new_node(addx, phase->get_ctrl(x));
 247   phase->_igvn.replace_node(n1, addx);
 248   assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
 249   _body.yank(n1);
 250   return addx;
 251 }
 252 
 253 //---------------------reassociate_invariants-----------------------------
 254 // Reassociate invariant expressions:
 255 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
 256   for (int i = _body.size() - 1; i >= 0; i--) {
 257     Node *n = _body.at(i);
 258     for (int j = 0; j < 5; j++) {
 259       Node* nn = reassociate_add_sub(n, phase);
 260       if (nn == NULL) break;
 261       n = nn; // again
 262     };
 263   }
 264 }
 265 
 266 //------------------------------policy_peeling---------------------------------
 267 // Return TRUE or FALSE if the loop should be peeled or not.  Peel if we can
 268 // make some loop-invariant test (usually a null-check) happen before the loop.
 269 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
 270   Node *test = ((IdealLoopTree*)this)->tail();
 271   int  body_size = ((IdealLoopTree*)this)->_body.size();
 272   int  live_node_count = phase->C->live_nodes();
 273   // Peeling does loop cloning which can result in O(N^2) node construction
 274   if( body_size > 255 /* Prevent overflow for large body_size */
 275       || (body_size * body_size + live_node_count > MaxNodeLimit) ) {
 276     return false;           // too large to safely clone
 277   }
 278   while( test != _head ) {      // Scan till run off top of loop
 279     if( test->is_If() ) {       // Test?
 280       Node *ctrl = phase->get_ctrl(test->in(1));
 281       if (ctrl->is_top())
 282         return false;           // Found dead test on live IF?  No peeling!
 283       // Standard IF only has one input value to check for loop invariance
 284       assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
 285       // Condition is not a member of this loop?
 286       if( !is_member(phase->get_loop(ctrl)) &&
 287           is_loop_exit(test) )
 288         return true;            // Found reason to peel!
 289     }
 290     // Walk up dominators to loop _head looking for test which is
 291     // executed on every path thru loop.
 292     test = phase->idom(test);
 293   }
 294   return false;
 295 }
 296 
 297 //------------------------------peeled_dom_test_elim---------------------------
 298 // If we got the effect of peeling, either by actually peeling or by making
 299 // a pre-loop which must execute at least once, we can remove all
 300 // loop-invariant dominated tests in the main body.
 301 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
 302   bool progress = true;
 303   while( progress ) {
 304     progress = false;           // Reset for next iteration
 305     Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
 306     Node *test = prev->in(0);
 307     while( test != loop->_head ) { // Scan till run off top of loop
 308 
 309       int p_op = prev->Opcode();
 310       if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
 311           test->is_If() &&      // Test?
 312           !test->in(1)->is_Con() && // And not already obvious?
 313           // Condition is not a member of this loop?
 314           !loop->is_member(get_loop(get_ctrl(test->in(1))))){
 315         // Walk loop body looking for instances of this test
 316         for( uint i = 0; i < loop->_body.size(); i++ ) {
 317           Node *n = loop->_body.at(i);
 318           if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
 319             // IfNode was dominated by version in peeled loop body
 320             progress = true;
 321             dominated_by( old_new[prev->_idx], n );
 322           }
 323         }
 324       }
 325       prev = test;
 326       test = idom(test);
 327     } // End of scan tests in loop
 328 
 329   } // End of while( progress )
 330 }
 331 
 332 //------------------------------do_peeling-------------------------------------
 333 // Peel the first iteration of the given loop.
 334 // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 335 //         The pre-loop illegally has 2 control users (old & new loops).
 336 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 337 //         Do this by making the old-loop fall-in edges act as if they came
 338 //         around the loopback from the prior iteration (follow the old-loop
 339 //         backedges) and then map to the new peeled iteration.  This leaves
 340 //         the pre-loop with only 1 user (the new peeled iteration), but the
 341 //         peeled-loop backedge has 2 users.
 342 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 343 //         extra backedge user.
 344 //
 345 //                   orig
 346 //
 347 //                  stmt1
 348 //                    |
 349 //                    v
 350 //              loop predicate
 351 //                    |
 352 //                    v
 353 //                   loop<----+
 354 //                     |      |
 355 //                   stmt2    |
 356 //                     |      |
 357 //                     v      |
 358 //                    if      ^
 359 //                   / \      |
 360 //                  /   \     |
 361 //                 v     v    |
 362 //               false true   |
 363 //               /       \    |
 364 //              /         ----+
 365 //             |
 366 //             v
 367 //           exit
 368 //
 369 //
 370 //            after clone loop
 371 //
 372 //                   stmt1
 373 //                     |
 374 //                     v
 375 //               loop predicate
 376 //                 /       \
 377 //        clone   /         \   orig
 378 //               /           \
 379 //              /             \
 380 //             v               v
 381 //   +---->loop clone          loop<----+
 382 //   |      |                    |      |
 383 //   |    stmt2 clone          stmt2    |
 384 //   |      |                    |      |
 385 //   |      v                    v      |
 386 //   ^      if clone            If      ^
 387 //   |      / \                / \      |
 388 //   |     /   \              /   \     |
 389 //   |    v     v            v     v    |
 390 //   |    true  false      false true   |
 391 //   |    /         \      /       \    |
 392 //   +----           \    /         ----+
 393 //                    \  /
 394 //                    1v v2
 395 //                  region
 396 //                     |
 397 //                     v
 398 //                   exit
 399 //
 400 //
 401 //         after peel and predicate move
 402 //
 403 //                   stmt1
 404 //                    /
 405 //                   /
 406 //        clone     /            orig
 407 //                 /
 408 //                /              +----------+
 409 //               /               |          |
 410 //              /          loop predicate   |
 411 //             /                 |          |
 412 //            v                  v          |
 413 //   TOP-->loop clone          loop<----+   |
 414 //          |                    |      |   |
 415 //        stmt2 clone          stmt2    |   |
 416 //          |                    |      |   ^
 417 //          v                    v      |   |
 418 //          if clone            If      ^   |
 419 //          / \                / \      |   |
 420 //         /   \              /   \     |   |
 421 //        v     v            v     v    |   |
 422 //      true   false      false  true   |   |
 423 //        |         \      /       \    |   |
 424 //        |          \    /         ----+   ^
 425 //        |           \  /                  |
 426 //        |           1v v2                 |
 427 //        v         region                  |
 428 //        |            |                    |
 429 //        |            v                    |
 430 //        |          exit                   |
 431 //        |                                 |
 432 //        +--------------->-----------------+
 433 //
 434 //
 435 //              final graph
 436 //
 437 //                  stmt1
 438 //                    |
 439 //                    v
 440 //                  stmt2 clone
 441 //                    |
 442 //                    v
 443 //                   if clone
 444 //                  / |
 445 //                 /  |
 446 //                v   v
 447 //            false  true
 448 //             |      |
 449 //             |      v
 450 //             | loop predicate
 451 //             |      |
 452 //             |      v
 453 //             |     loop<----+
 454 //             |      |       |
 455 //             |    stmt2     |
 456 //             |      |       |
 457 //             |      v       |
 458 //             v      if      ^
 459 //             |     /  \     |
 460 //             |    /    \    |
 461 //             |   v     v    |
 462 //             | false  true  |
 463 //             |  |        \  |
 464 //             v  v         --+
 465 //            region
 466 //              |
 467 //              v
 468 //             exit
 469 //
 470 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
 471 
 472   C->set_major_progress();
 473   // Peeling a 'main' loop in a pre/main/post situation obfuscates the
 474   // 'pre' loop from the main and the 'pre' can no longer have it's
 475   // iterations adjusted.  Therefore, we need to declare this loop as
 476   // no longer a 'main' loop; it will need new pre and post loops before
 477   // we can do further RCE.
 478 #ifndef PRODUCT
 479   if (TraceLoopOpts) {
 480     tty->print("Peel         ");
 481     loop->dump_head();
 482   }
 483 #endif
 484   Node* head = loop->_head;
 485   bool counted_loop = head->is_CountedLoop();
 486   if (counted_loop) {
 487     CountedLoopNode *cl = head->as_CountedLoop();
 488     assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
 489     cl->set_trip_count(cl->trip_count() - 1);
 490     if (cl->is_main_loop()) {
 491       cl->set_normal_loop();
 492 #ifndef PRODUCT
 493       if (PrintOpto && VerifyLoopOptimizations) {
 494         tty->print("Peeling a 'main' loop; resetting to 'normal' ");
 495         loop->dump_head();
 496       }
 497 #endif
 498     }
 499   }
 500   Node* entry = head->in(LoopNode::EntryControl);
 501 
 502   // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 503   //         The pre-loop illegally has 2 control users (old & new loops).
 504   clone_loop( loop, old_new, dom_depth(head) );
 505 
 506   // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 507   //         Do this by making the old-loop fall-in edges act as if they came
 508   //         around the loopback from the prior iteration (follow the old-loop
 509   //         backedges) and then map to the new peeled iteration.  This leaves
 510   //         the pre-loop with only 1 user (the new peeled iteration), but the
 511   //         peeled-loop backedge has 2 users.
 512   Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx];
 513   _igvn.hash_delete(head);
 514   head->set_req(LoopNode::EntryControl, new_entry);
 515   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
 516     Node* old = head->fast_out(j);
 517     if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
 518       Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
 519       if (!new_exit_value )     // Backedge value is ALSO loop invariant?
 520         // Then loop body backedge value remains the same.
 521         new_exit_value = old->in(LoopNode::LoopBackControl);
 522       _igvn.hash_delete(old);
 523       old->set_req(LoopNode::EntryControl, new_exit_value);
 524     }
 525   }
 526 
 527 
 528   // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 529   //         extra backedge user.
 530   Node* new_head = old_new[head->_idx];
 531   _igvn.hash_delete(new_head);
 532   new_head->set_req(LoopNode::LoopBackControl, C->top());
 533   for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
 534     Node* use = new_head->fast_out(j2);
 535     if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
 536       _igvn.hash_delete(use);
 537       use->set_req(LoopNode::LoopBackControl, C->top());
 538     }
 539   }
 540 
 541 
 542   // Step 4: Correct dom-depth info.  Set to loop-head depth.
 543   int dd = dom_depth(head);
 544   set_idom(head, head->in(1), dd);
 545   for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
 546     Node *old = loop->_body.at(j3);
 547     Node *nnn = old_new[old->_idx];
 548     if (!has_ctrl(nnn))
 549       set_idom(nnn, idom(nnn), dd-1);
 550   }
 551 
 552   // Now force out all loop-invariant dominating tests.  The optimizer
 553   // finds some, but we _know_ they are all useless.
 554   peeled_dom_test_elim(loop,old_new);
 555 
 556   loop->record_for_igvn();
 557 }
 558 
 559 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop
 560 
 561 //------------------------------policy_maximally_unroll------------------------
 562 // Calculate exact loop trip count and return true if loop can be maximally
 563 // unrolled.
 564 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
 565   CountedLoopNode *cl = _head->as_CountedLoop();
 566   assert(cl->is_normal_loop(), "");
 567   if (!cl->is_valid_counted_loop())
 568     return false; // Malformed counted loop
 569 
 570   if (!cl->has_exact_trip_count()) {
 571     // Trip count is not exact.
 572     return false;
 573   }
 574 
 575   uint trip_count = cl->trip_count();
 576   // Note, max_juint is used to indicate unknown trip count.
 577   assert(trip_count > 1, "one iteration loop should be optimized out already");
 578   assert(trip_count < max_juint, "exact trip_count should be less than max_uint.");
 579 
 580   // Real policy: if we maximally unroll, does it get too big?
 581   // Allow the unrolled mess to get larger than standard loop
 582   // size.  After all, it will no longer be a loop.
 583   uint body_size    = _body.size();
 584   uint unroll_limit = (uint)LoopUnrollLimit * 4;
 585   assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
 586   if (trip_count > unroll_limit || body_size > unroll_limit) {
 587     return false;
 588   }
 589 
 590   // Fully unroll a loop with few iterations regardless next
 591   // conditions since following loop optimizations will split
 592   // such loop anyway (pre-main-post).
 593   if (trip_count <= 3)
 594     return true;
 595 
 596   // Take into account that after unroll conjoined heads and tails will fold,
 597   // otherwise policy_unroll() may allow more unrolling than max unrolling.
 598   uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count;
 599   uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE;
 600   if (body_size != tst_body_size) // Check for int overflow
 601     return false;
 602   if (new_body_size > unroll_limit ||
 603       // Unrolling can result in a large amount of node construction
 604       new_body_size >= MaxNodeLimit - (uint) phase->C->live_nodes()) {
 605     return false;
 606   }
 607 
 608   // Do not unroll a loop with String intrinsics code.
 609   // String intrinsics are large and have loops.
 610   for (uint k = 0; k < _body.size(); k++) {
 611     Node* n = _body.at(k);
 612     switch (n->Opcode()) {
 613       case Op_StrComp:
 614       case Op_StrEquals:
 615       case Op_StrIndexOf:
 616       case Op_EncodeISOArray:
 617       case Op_AryEq: {
 618         return false;
 619       }
 620     } // switch
 621   }
 622 
 623   return true; // Do maximally unroll
 624 }
 625 
 626 
 627 //------------------------------policy_unroll----------------------------------
 628 // Return TRUE or FALSE if the loop should be unrolled or not.  Unroll if
 629 // the loop is a CountedLoop and the body is small enough.
 630 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
 631 
 632   CountedLoopNode *cl = _head->as_CountedLoop();
 633   assert(cl->is_normal_loop() || cl->is_main_loop(), "");
 634 
 635   if (!cl->is_valid_counted_loop())
 636     return false; // Malformed counted loop
 637 
 638   // Protect against over-unrolling.
 639   // After split at least one iteration will be executed in pre-loop.
 640   if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false;
 641 
 642   int future_unroll_ct = cl->unrolled_count() * 2;
 643   if (future_unroll_ct > LoopMaxUnroll) return false;
 644 
 645   // Check for initial stride being a small enough constant
 646   if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false;
 647 
 648   // Don't unroll if the next round of unrolling would push us
 649   // over the expected trip count of the loop.  One is subtracted
 650   // from the expected trip count because the pre-loop normally
 651   // executes 1 iteration.
 652   if (UnrollLimitForProfileCheck > 0 &&
 653       cl->profile_trip_cnt() != COUNT_UNKNOWN &&
 654       future_unroll_ct        > UnrollLimitForProfileCheck &&
 655       (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
 656     return false;
 657   }
 658 
 659   // When unroll count is greater than LoopUnrollMin, don't unroll if:
 660   //   the residual iterations are more than 10% of the trip count
 661   //   and rounds of "unroll,optimize" are not making significant progress
 662   //   Progress defined as current size less than 20% larger than previous size.
 663   if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
 664       future_unroll_ct > LoopUnrollMin &&
 665       (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() &&
 666       1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
 667     return false;
 668   }
 669 
 670   Node *init_n = cl->init_trip();
 671   Node *limit_n = cl->limit();
 672   int stride_con = cl->stride_con();
 673   // Non-constant bounds.
 674   // Protect against over-unrolling when init or/and limit are not constant
 675   // (so that trip_count's init value is maxint) but iv range is known.
 676   if (init_n   == NULL || !init_n->is_Con()  ||
 677       limit_n  == NULL || !limit_n->is_Con()) {
 678     Node* phi = cl->phi();
 679     if (phi != NULL) {
 680       assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
 681       const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
 682       int next_stride = stride_con * 2; // stride after this unroll
 683       if (next_stride > 0) {
 684         if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
 685             iv_type->_lo + next_stride >  iv_type->_hi) {
 686           return false;  // over-unrolling
 687         }
 688       } else if (next_stride < 0) {
 689         if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
 690             iv_type->_hi + next_stride <  iv_type->_lo) {
 691           return false;  // over-unrolling
 692         }
 693       }
 694     }
 695   }
 696 
 697   // After unroll limit will be adjusted: new_limit = limit-stride.
 698   // Bailout if adjustment overflow.
 699   const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
 700   if (stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi) ||
 701       stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo))
 702     return false;  // overflow
 703 
 704   // Adjust body_size to determine if we unroll or not
 705   uint body_size = _body.size();
 706   // Key test to unroll loop in CRC32 java code
 707   int xors_in_loop = 0;
 708   // Also count ModL, DivL and MulL which expand mightly
 709   for (uint k = 0; k < _body.size(); k++) {
 710     Node* n = _body.at(k);
 711     switch (n->Opcode()) {
 712       case Op_XorI: xors_in_loop++; break; // CRC32 java code
 713       case Op_ModL: body_size += 30; break;
 714       case Op_DivL: body_size += 30; break;
 715       case Op_MulL: body_size += 10; break;
 716       case Op_StrComp:
 717       case Op_StrEquals:
 718       case Op_StrIndexOf:
 719       case Op_EncodeISOArray:
 720       case Op_AryEq: {
 721         // Do not unroll a loop with String intrinsics code.
 722         // String intrinsics are large and have loops.
 723         return false;
 724       }
 725     } // switch
 726   }
 727 
 728   // Check for being too big
 729   if (body_size > (uint)LoopUnrollLimit) {
 730     if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
 731     // Normal case: loop too big
 732     return false;
 733   }
 734 
 735   // Unroll once!  (Each trip will soon do double iterations)
 736   return true;
 737 }
 738 
 739 //------------------------------policy_align-----------------------------------
 740 // Return TRUE or FALSE if the loop should be cache-line aligned.  Gather the
 741 // expression that does the alignment.  Note that only one array base can be
 742 // aligned in a loop (unless the VM guarantees mutual alignment).  Note that
 743 // if we vectorize short memory ops into longer memory ops, we may want to
 744 // increase alignment.
 745 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
 746   return false;
 747 }
 748 
 749 //------------------------------policy_range_check-----------------------------
 750 // Return TRUE or FALSE if the loop should be range-check-eliminated.
 751 // Actually we do iteration-splitting, a more powerful form of RCE.
 752 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
 753   if (!RangeCheckElimination) return false;
 754 
 755   CountedLoopNode *cl = _head->as_CountedLoop();
 756   // If we unrolled with no intention of doing RCE and we later
 757   // changed our minds, we got no pre-loop.  Either we need to
 758   // make a new pre-loop, or we gotta disallow RCE.
 759   if (cl->is_main_no_pre_loop()) return false; // Disallowed for now.
 760   Node *trip_counter = cl->phi();
 761 
 762   // Check loop body for tests of trip-counter plus loop-invariant vs
 763   // loop-invariant.
 764   for (uint i = 0; i < _body.size(); i++) {
 765     Node *iff = _body[i];
 766     if (iff->Opcode() == Op_If) { // Test?
 767 
 768       // Comparing trip+off vs limit
 769       Node *bol = iff->in(1);
 770       if (bol->req() != 2) continue; // dead constant test
 771       if (!bol->is_Bool()) {
 772         assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
 773         continue;
 774       }
 775       if (bol->as_Bool()->_test._test == BoolTest::ne)
 776         continue; // not RC
 777 
 778       Node *cmp = bol->in(1);
 779 
 780       Node *rc_exp = cmp->in(1);
 781       Node *limit = cmp->in(2);
 782 
 783       Node *limit_c = phase->get_ctrl(limit);
 784       if( limit_c == phase->C->top() )
 785         return false;           // Found dead test on live IF?  No RCE!
 786       if( is_member(phase->get_loop(limit_c) ) ) {
 787         // Compare might have operands swapped; commute them
 788         rc_exp = cmp->in(2);
 789         limit  = cmp->in(1);
 790         limit_c = phase->get_ctrl(limit);
 791         if( is_member(phase->get_loop(limit_c) ) )
 792           continue;             // Both inputs are loop varying; cannot RCE
 793       }
 794 
 795       if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
 796         continue;
 797       }
 798       // Yeah!  Found a test like 'trip+off vs limit'
 799       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
 800       // we need loop unswitching instead of iteration splitting.
 801       if( is_loop_exit(iff) )
 802         return true;            // Found reason to split iterations
 803     } // End of is IF
 804   }
 805 
 806   return false;
 807 }
 808 
 809 //------------------------------policy_peel_only-------------------------------
 810 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned.  Useful
 811 // for unrolling loops with NO array accesses.
 812 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
 813 
 814   for( uint i = 0; i < _body.size(); i++ )
 815     if( _body[i]->is_Mem() )
 816       return false;
 817 
 818   // No memory accesses at all!
 819   return true;
 820 }
 821 
 822 //------------------------------clone_up_backedge_goo--------------------------
 823 // If Node n lives in the back_ctrl block and cannot float, we clone a private
 824 // version of n in preheader_ctrl block and return that, otherwise return n.
 825 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) {
 826   if( get_ctrl(n) != back_ctrl ) return n;
 827 
 828   // Only visit once
 829   if (visited.test_set(n->_idx)) {
 830     Node *x = clones.find(n->_idx);
 831     if (x != NULL)
 832       return x;
 833     return n;
 834   }
 835 
 836   Node *x = NULL;               // If required, a clone of 'n'
 837   // Check for 'n' being pinned in the backedge.
 838   if( n->in(0) && n->in(0) == back_ctrl ) {
 839     assert(clones.find(n->_idx) == NULL, "dead loop");
 840     x = n->clone();             // Clone a copy of 'n' to preheader
 841     clones.push(x, n->_idx);
 842     x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
 843   }
 844 
 845   // Recursive fixup any other input edges into x.
 846   // If there are no changes we can just return 'n', otherwise
 847   // we need to clone a private copy and change it.
 848   for( uint i = 1; i < n->req(); i++ ) {
 849     Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones );
 850     if( g != n->in(i) ) {
 851       if( !x ) {
 852         assert(clones.find(n->_idx) == NULL, "dead loop");
 853         x = n->clone();
 854         clones.push(x, n->_idx);
 855       }
 856       x->set_req(i, g);
 857     }
 858   }
 859   if( x ) {                     // x can legally float to pre-header location
 860     register_new_node( x, preheader_ctrl );
 861     return x;
 862   } else {                      // raise n to cover LCA of uses
 863     set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
 864   }
 865   return n;
 866 }
 867 
 868 //------------------------------insert_pre_post_loops--------------------------
 869 // Insert pre and post loops.  If peel_only is set, the pre-loop can not have
 870 // more iterations added.  It acts as a 'peel' only, no lower-bound RCE, no
 871 // alignment.  Useful to unroll loops that do no array accesses.
 872 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
 873 
 874 #ifndef PRODUCT
 875   if (TraceLoopOpts) {
 876     if (peel_only)
 877       tty->print("PeelMainPost ");
 878     else
 879       tty->print("PreMainPost  ");
 880     loop->dump_head();
 881   }
 882 #endif
 883   C->set_major_progress();
 884 
 885   // Find common pieces of the loop being guarded with pre & post loops
 886   CountedLoopNode *main_head = loop->_head->as_CountedLoop();
 887   assert( main_head->is_normal_loop(), "" );
 888   CountedLoopEndNode *main_end = main_head->loopexit();
 889   guarantee(main_end != NULL, "no loop exit node");
 890   assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
 891   uint dd_main_head = dom_depth(main_head);
 892   uint max = main_head->outcnt();
 893 
 894   Node *pre_header= main_head->in(LoopNode::EntryControl);
 895   Node *init      = main_head->init_trip();
 896   Node *incr      = main_end ->incr();
 897   Node *limit     = main_end ->limit();
 898   Node *stride    = main_end ->stride();
 899   Node *cmp       = main_end ->cmp_node();
 900   BoolTest::mask b_test = main_end->test_trip();
 901 
 902   // Need only 1 user of 'bol' because I will be hacking the loop bounds.
 903   Node *bol = main_end->in(CountedLoopEndNode::TestValue);
 904   if( bol->outcnt() != 1 ) {
 905     bol = bol->clone();
 906     register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
 907     _igvn.hash_delete(main_end);
 908     main_end->set_req(CountedLoopEndNode::TestValue, bol);
 909   }
 910   // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
 911   if( cmp->outcnt() != 1 ) {
 912     cmp = cmp->clone();
 913     register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
 914     _igvn.hash_delete(bol);
 915     bol->set_req(1, cmp);
 916   }
 917 
 918   //------------------------------
 919   // Step A: Create Post-Loop.
 920   Node* main_exit = main_end->proj_out(false);
 921   assert( main_exit->Opcode() == Op_IfFalse, "" );
 922   int dd_main_exit = dom_depth(main_exit);
 923 
 924   // Step A1: Clone the loop body.  The clone becomes the post-loop.  The main
 925   // loop pre-header illegally has 2 control users (old & new loops).
 926   clone_loop( loop, old_new, dd_main_exit );
 927   assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
 928   CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
 929   post_head->set_post_loop(main_head);
 930 
 931   // Reduce the post-loop trip count.
 932   CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
 933   post_end->_prob = PROB_FAIR;
 934 
 935   // Build the main-loop normal exit.
 936   IfFalseNode *new_main_exit = new (C) IfFalseNode(main_end);
 937   _igvn.register_new_node_with_optimizer( new_main_exit );
 938   set_idom(new_main_exit, main_end, dd_main_exit );
 939   set_loop(new_main_exit, loop->_parent);
 940 
 941   // Step A2: Build a zero-trip guard for the post-loop.  After leaving the
 942   // main-loop, the post-loop may not execute at all.  We 'opaque' the incr
 943   // (the main-loop trip-counter exit value) because we will be changing
 944   // the exit value (via unrolling) so we cannot constant-fold away the zero
 945   // trip guard until all unrolling is done.
 946   Node *zer_opaq = new (C) Opaque1Node(C, incr);
 947   Node *zer_cmp  = new (C) CmpINode( zer_opaq, limit );
 948   Node *zer_bol  = new (C) BoolNode( zer_cmp, b_test );
 949   register_new_node( zer_opaq, new_main_exit );
 950   register_new_node( zer_cmp , new_main_exit );
 951   register_new_node( zer_bol , new_main_exit );
 952 
 953   // Build the IfNode
 954   IfNode *zer_iff = new (C) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
 955   _igvn.register_new_node_with_optimizer( zer_iff );
 956   set_idom(zer_iff, new_main_exit, dd_main_exit);
 957   set_loop(zer_iff, loop->_parent);
 958 
 959   // Plug in the false-path, taken if we need to skip post-loop
 960   _igvn.replace_input_of(main_exit, 0, zer_iff);
 961   set_idom(main_exit, zer_iff, dd_main_exit);
 962   set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
 963   // Make the true-path, must enter the post loop
 964   Node *zer_taken = new (C) IfTrueNode( zer_iff );
 965   _igvn.register_new_node_with_optimizer( zer_taken );
 966   set_idom(zer_taken, zer_iff, dd_main_exit);
 967   set_loop(zer_taken, loop->_parent);
 968   // Plug in the true path
 969   _igvn.hash_delete( post_head );
 970   post_head->set_req(LoopNode::EntryControl, zer_taken);
 971   set_idom(post_head, zer_taken, dd_main_exit);
 972 
 973   Arena *a = Thread::current()->resource_area();
 974   VectorSet visited(a);
 975   Node_Stack clones(a, main_head->back_control()->outcnt());
 976   // Step A3: Make the fall-in values to the post-loop come from the
 977   // fall-out values of the main-loop.
 978   for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
 979     Node* main_phi = main_head->fast_out(i);
 980     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
 981       Node *post_phi = old_new[main_phi->_idx];
 982       Node *fallmain  = clone_up_backedge_goo(main_head->back_control(),
 983                                               post_head->init_control(),
 984                                               main_phi->in(LoopNode::LoopBackControl),
 985                                               visited, clones);
 986       _igvn.hash_delete(post_phi);
 987       post_phi->set_req( LoopNode::EntryControl, fallmain );
 988     }
 989   }
 990 
 991   // Update local caches for next stanza
 992   main_exit = new_main_exit;
 993 
 994 
 995   //------------------------------
 996   // Step B: Create Pre-Loop.
 997 
 998   // Step B1: Clone the loop body.  The clone becomes the pre-loop.  The main
 999   // loop pre-header illegally has 2 control users (old & new loops).
1000   clone_loop( loop, old_new, dd_main_head );
1001   CountedLoopNode*    pre_head = old_new[main_head->_idx]->as_CountedLoop();
1002   CountedLoopEndNode* pre_end  = old_new[main_end ->_idx]->as_CountedLoopEnd();
1003   pre_head->set_pre_loop(main_head);
1004   Node *pre_incr = old_new[incr->_idx];
1005 
1006   // Reduce the pre-loop trip count.
1007   pre_end->_prob = PROB_FAIR;
1008 
1009   // Find the pre-loop normal exit.
1010   Node* pre_exit = pre_end->proj_out(false);
1011   assert( pre_exit->Opcode() == Op_IfFalse, "" );
1012   IfFalseNode *new_pre_exit = new (C) IfFalseNode(pre_end);
1013   _igvn.register_new_node_with_optimizer( new_pre_exit );
1014   set_idom(new_pre_exit, pre_end, dd_main_head);
1015   set_loop(new_pre_exit, loop->_parent);
1016 
1017   // Step B2: Build a zero-trip guard for the main-loop.  After leaving the
1018   // pre-loop, the main-loop may not execute at all.  Later in life this
1019   // zero-trip guard will become the minimum-trip guard when we unroll
1020   // the main-loop.
1021   Node *min_opaq = new (C) Opaque1Node(C, limit);
1022   Node *min_cmp  = new (C) CmpINode( pre_incr, min_opaq );
1023   Node *min_bol  = new (C) BoolNode( min_cmp, b_test );
1024   register_new_node( min_opaq, new_pre_exit );
1025   register_new_node( min_cmp , new_pre_exit );
1026   register_new_node( min_bol , new_pre_exit );
1027 
1028   // Build the IfNode (assume the main-loop is executed always).
1029   IfNode *min_iff = new (C) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
1030   _igvn.register_new_node_with_optimizer( min_iff );
1031   set_idom(min_iff, new_pre_exit, dd_main_head);
1032   set_loop(min_iff, loop->_parent);
1033 
1034   // Plug in the false-path, taken if we need to skip main-loop
1035   _igvn.hash_delete( pre_exit );
1036   pre_exit->set_req(0, min_iff);
1037   set_idom(pre_exit, min_iff, dd_main_head);
1038   set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
1039   // Make the true-path, must enter the main loop
1040   Node *min_taken = new (C) IfTrueNode( min_iff );
1041   _igvn.register_new_node_with_optimizer( min_taken );
1042   set_idom(min_taken, min_iff, dd_main_head);
1043   set_loop(min_taken, loop->_parent);
1044   // Plug in the true path
1045   _igvn.hash_delete( main_head );
1046   main_head->set_req(LoopNode::EntryControl, min_taken);
1047   set_idom(main_head, min_taken, dd_main_head);
1048 
1049   visited.Clear();
1050   clones.clear();
1051   // Step B3: Make the fall-in values to the main-loop come from the
1052   // fall-out values of the pre-loop.
1053   for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
1054     Node* main_phi = main_head->fast_out(i2);
1055     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
1056       Node *pre_phi = old_new[main_phi->_idx];
1057       Node *fallpre  = clone_up_backedge_goo(pre_head->back_control(),
1058                                              main_head->init_control(),
1059                                              pre_phi->in(LoopNode::LoopBackControl),
1060                                              visited, clones);
1061       _igvn.hash_delete(main_phi);
1062       main_phi->set_req( LoopNode::EntryControl, fallpre );
1063     }
1064   }
1065 
1066   // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1067   // RCE and alignment may change this later.
1068   Node *cmp_end = pre_end->cmp_node();
1069   assert( cmp_end->in(2) == limit, "" );
1070   Node *pre_limit = new (C) AddINode( init, stride );
1071 
1072   // Save the original loop limit in this Opaque1 node for
1073   // use by range check elimination.
1074   Node *pre_opaq  = new (C) Opaque1Node(C, pre_limit, limit);
1075 
1076   register_new_node( pre_limit, pre_head->in(0) );
1077   register_new_node( pre_opaq , pre_head->in(0) );
1078 
1079   // Since no other users of pre-loop compare, I can hack limit directly
1080   assert( cmp_end->outcnt() == 1, "no other users" );
1081   _igvn.hash_delete(cmp_end);
1082   cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
1083 
1084   // Special case for not-equal loop bounds:
1085   // Change pre loop test, main loop test, and the
1086   // main loop guard test to use lt or gt depending on stride
1087   // direction:
1088   // positive stride use <
1089   // negative stride use >
1090   //
1091   // not-equal test is kept for post loop to handle case
1092   // when init > limit when stride > 0 (and reverse).
1093 
1094   if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
1095 
1096     BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
1097     // Modify pre loop end condition
1098     Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1099     BoolNode* new_bol0 = new (C) BoolNode(pre_bol->in(1), new_test);
1100     register_new_node( new_bol0, pre_head->in(0) );
1101     _igvn.hash_delete(pre_end);
1102     pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0);
1103     // Modify main loop guard condition
1104     assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
1105     BoolNode* new_bol1 = new (C) BoolNode(min_bol->in(1), new_test);
1106     register_new_node( new_bol1, new_pre_exit );
1107     _igvn.hash_delete(min_iff);
1108     min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
1109     // Modify main loop end condition
1110     BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1111     BoolNode* new_bol2 = new (C) BoolNode(main_bol->in(1), new_test);
1112     register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
1113     _igvn.hash_delete(main_end);
1114     main_end->set_req(CountedLoopEndNode::TestValue, new_bol2);
1115   }
1116 
1117   // Flag main loop
1118   main_head->set_main_loop();
1119   if( peel_only ) main_head->set_main_no_pre_loop();
1120 
1121   // Subtract a trip count for the pre-loop.
1122   main_head->set_trip_count(main_head->trip_count() - 1);
1123 
1124   // It's difficult to be precise about the trip-counts
1125   // for the pre/post loops.  They are usually very short,
1126   // so guess that 4 trips is a reasonable value.
1127   post_head->set_profile_trip_cnt(4.0);
1128   pre_head->set_profile_trip_cnt(4.0);
1129 
1130   // Now force out all loop-invariant dominating tests.  The optimizer
1131   // finds some, but we _know_ they are all useless.
1132   peeled_dom_test_elim(loop,old_new);
1133 }
1134 
1135 //------------------------------is_invariant-----------------------------
1136 // Return true if n is invariant
1137 bool IdealLoopTree::is_invariant(Node* n) const {
1138   Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
1139   if (n_c->is_top()) return false;
1140   return !is_member(_phase->get_loop(n_c));
1141 }
1142 
1143 
1144 //------------------------------do_unroll--------------------------------------
1145 // Unroll the loop body one step - make each trip do 2 iterations.
1146 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
1147   assert(LoopUnrollLimit, "");
1148   CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
1149   CountedLoopEndNode *loop_end = loop_head->loopexit();
1150   assert(loop_end, "");
1151 #ifndef PRODUCT
1152   if (PrintOpto && VerifyLoopOptimizations) {
1153     tty->print("Unrolling ");
1154     loop->dump_head();
1155   } else if (TraceLoopOpts) {
1156     if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
1157       tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
1158     } else {
1159       tty->print("Unroll %d     ", loop_head->unrolled_count()*2);
1160     }
1161     loop->dump_head();
1162   }
1163 #endif
1164 
1165   // Remember loop node count before unrolling to detect
1166   // if rounds of unroll,optimize are making progress
1167   loop_head->set_node_count_before_unroll(loop->_body.size());
1168 
1169   Node *ctrl  = loop_head->in(LoopNode::EntryControl);
1170   Node *limit = loop_head->limit();
1171   Node *init  = loop_head->init_trip();
1172   Node *stride = loop_head->stride();
1173 
1174   Node *opaq = NULL;
1175   if (adjust_min_trip) {       // If not maximally unrolling, need adjustment
1176     // Search for zero-trip guard.
1177     assert( loop_head->is_main_loop(), "" );
1178     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
1179     Node *iff = ctrl->in(0);
1180     assert( iff->Opcode() == Op_If, "" );
1181     Node *bol = iff->in(1);
1182     assert( bol->Opcode() == Op_Bool, "" );
1183     Node *cmp = bol->in(1);
1184     assert( cmp->Opcode() == Op_CmpI, "" );
1185     opaq = cmp->in(2);
1186     // Occasionally it's possible for a zero-trip guard Opaque1 node to be
1187     // optimized away and then another round of loop opts attempted.
1188     // We can not optimize this particular loop in that case.
1189     if (opaq->Opcode() != Op_Opaque1)
1190       return; // Cannot find zero-trip guard!  Bail out!
1191     // Zero-trip test uses an 'opaque' node which is not shared.
1192     assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
1193   }
1194 
1195   C->set_major_progress();
1196 
1197   Node* new_limit = NULL;
1198   if (UnrollLimitCheck) {
1199     int stride_con = stride->get_int();
1200     int stride_p = (stride_con > 0) ? stride_con : -stride_con;
1201     uint old_trip_count = loop_head->trip_count();
1202     // Verify that unroll policy result is still valid.
1203     assert(old_trip_count > 1 &&
1204            (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity");
1205 
1206     // Adjust loop limit to keep valid iterations number after unroll.
1207     // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
1208     // which may overflow.
1209     if (!adjust_min_trip) {
1210       assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
1211              "odd trip count for maximally unroll");
1212       // Don't need to adjust limit for maximally unroll since trip count is even.
1213     } else if (loop_head->has_exact_trip_count() && init->is_Con()) {
1214       // Loop's limit is constant. Loop's init could be constant when pre-loop
1215       // become peeled iteration.
1216       jlong init_con = init->get_int();
1217       // We can keep old loop limit if iterations count stays the same:
1218       //   old_trip_count == new_trip_count * 2
1219       // Note: since old_trip_count >= 2 then new_trip_count >= 1
1220       // so we also don't need to adjust zero trip test.
1221       jlong limit_con  = limit->get_int();
1222       // (stride_con*2) not overflow since stride_con <= 8.
1223       int new_stride_con = stride_con * 2;
1224       int stride_m    = new_stride_con - (stride_con > 0 ? 1 : -1);
1225       jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con;
1226       // New trip count should satisfy next conditions.
1227       assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
1228       uint new_trip_count = (uint)trip_count;
1229       adjust_min_trip = (old_trip_count != new_trip_count*2);
1230     }
1231 
1232     if (adjust_min_trip) {
1233       // Step 2: Adjust the trip limit if it is called for.
1234       // The adjustment amount is -stride. Need to make sure if the
1235       // adjustment underflows or overflows, then the main loop is skipped.
1236       Node* cmp = loop_end->cmp_node();
1237       assert(cmp->in(2) == limit, "sanity");
1238       assert(opaq != NULL && opaq->in(1) == limit, "sanity");
1239 
1240       // Verify that policy_unroll result is still valid.
1241       const TypeInt* limit_type = _igvn.type(limit)->is_int();
1242       assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) ||
1243              stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity");
1244 
1245       if (limit->is_Con()) {
1246         // The check in policy_unroll and the assert above guarantee
1247         // no underflow if limit is constant.
1248         new_limit = _igvn.intcon(limit->get_int() - stride_con);
1249         set_ctrl(new_limit, C->root());
1250       } else {
1251         // Limit is not constant.
1252         if (loop_head->unrolled_count() == 1) { // only for first unroll
1253           // Separate limit by Opaque node in case it is an incremented
1254           // variable from previous loop to avoid using pre-incremented
1255           // value which could increase register pressure.
1256           // Otherwise reorg_offsets() optimization will create a separate
1257           // Opaque node for each use of trip-counter and as result
1258           // zero trip guard limit will be different from loop limit.
1259           assert(has_ctrl(opaq), "should have it");
1260           Node* opaq_ctrl = get_ctrl(opaq);
1261           limit = new (C) Opaque2Node( C, limit );
1262           register_new_node( limit, opaq_ctrl );
1263         }
1264         if (stride_con > 0 && ((limit_type->_lo - stride_con) < limit_type->_lo) ||
1265                    stride_con < 0 && ((limit_type->_hi - stride_con) > limit_type->_hi)) {
1266           // No underflow.
1267           new_limit = new (C) SubINode(limit, stride);
1268         } else {
1269           // (limit - stride) may underflow.
1270           // Clamp the adjustment value with MININT or MAXINT:
1271           //
1272           //   new_limit = limit-stride
1273           //   if (stride > 0)
1274           //     new_limit = (limit < new_limit) ? MININT : new_limit;
1275           //   else
1276           //     new_limit = (limit > new_limit) ? MAXINT : new_limit;
1277           //
1278           BoolTest::mask bt = loop_end->test_trip();
1279           assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
1280           Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint);
1281           set_ctrl(adj_max, C->root());
1282           Node* old_limit = NULL;
1283           Node* adj_limit = NULL;
1284           Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL;
1285           if (loop_head->unrolled_count() > 1 &&
1286               limit->is_CMove() && limit->Opcode() == Op_CMoveI &&
1287               limit->in(CMoveNode::IfTrue) == adj_max &&
1288               bol->as_Bool()->_test._test == bt &&
1289               bol->in(1)->Opcode() == Op_CmpI &&
1290               bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) {
1291             // Loop was unrolled before.
1292             // Optimize the limit to avoid nested CMove:
1293             // use original limit as old limit.
1294             old_limit = bol->in(1)->in(1);
1295             // Adjust previous adjusted limit.
1296             adj_limit = limit->in(CMoveNode::IfFalse);
1297             adj_limit = new (C) SubINode(adj_limit, stride);
1298           } else {
1299             old_limit = limit;
1300             adj_limit = new (C) SubINode(limit, stride);
1301           }
1302           assert(old_limit != NULL && adj_limit != NULL, "");
1303           register_new_node( adj_limit, ctrl ); // adjust amount
1304           Node* adj_cmp = new (C) CmpINode(old_limit, adj_limit);
1305           register_new_node( adj_cmp, ctrl );
1306           Node* adj_bool = new (C) BoolNode(adj_cmp, bt);
1307           register_new_node( adj_bool, ctrl );
1308           new_limit = new (C) CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT);
1309         }
1310         register_new_node(new_limit, ctrl);
1311       }
1312       assert(new_limit != NULL, "");
1313       // Replace in loop test.
1314       assert(loop_end->in(1)->in(1) == cmp, "sanity");
1315       if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
1316         // Don't need to create new test since only one user.
1317         _igvn.hash_delete(cmp);
1318         cmp->set_req(2, new_limit);
1319       } else {
1320         // Create new test since it is shared.
1321         Node* ctrl2 = loop_end->in(0);
1322         Node* cmp2  = cmp->clone();
1323         cmp2->set_req(2, new_limit);
1324         register_new_node(cmp2, ctrl2);
1325         Node* bol2 = loop_end->in(1)->clone();
1326         bol2->set_req(1, cmp2);
1327         register_new_node(bol2, ctrl2);
1328         _igvn.hash_delete(loop_end);
1329         loop_end->set_req(1, bol2);
1330       }
1331       // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1332       // Make it a 1-trip test (means at least 2 trips).
1333 
1334       // Guard test uses an 'opaque' node which is not shared.  Hence I
1335       // can edit it's inputs directly.  Hammer in the new limit for the
1336       // minimum-trip guard.
1337       assert(opaq->outcnt() == 1, "");
1338       _igvn.hash_delete(opaq);
1339       opaq->set_req(1, new_limit);
1340     }
1341 
1342     // Adjust max trip count. The trip count is intentionally rounded
1343     // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1344     // the main, unrolled, part of the loop will never execute as it is protected
1345     // by the min-trip test.  See bug 4834191 for a case where we over-unrolled
1346     // and later determined that part of the unrolled loop was dead.
1347     loop_head->set_trip_count(old_trip_count / 2);
1348 
1349     // Double the count of original iterations in the unrolled loop body.
1350     loop_head->double_unrolled_count();
1351 
1352   } else { // LoopLimitCheck
1353 
1354     // Adjust max trip count. The trip count is intentionally rounded
1355     // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1356     // the main, unrolled, part of the loop will never execute as it is protected
1357     // by the min-trip test.  See bug 4834191 for a case where we over-unrolled
1358     // and later determined that part of the unrolled loop was dead.
1359     loop_head->set_trip_count(loop_head->trip_count() / 2);
1360 
1361     // Double the count of original iterations in the unrolled loop body.
1362     loop_head->double_unrolled_count();
1363 
1364     // -----------
1365     // Step 2: Cut back the trip counter for an unroll amount of 2.
1366     // Loop will normally trip (limit - init)/stride_con.  Since it's a
1367     // CountedLoop this is exact (stride divides limit-init exactly).
1368     // We are going to double the loop body, so we want to knock off any
1369     // odd iteration: (trip_cnt & ~1).  Then back compute a new limit.
1370     Node *span = new (C) SubINode( limit, init );
1371     register_new_node( span, ctrl );
1372     Node *trip = new (C) DivINode( 0, span, stride );
1373     register_new_node( trip, ctrl );
1374     Node *mtwo = _igvn.intcon(-2);
1375     set_ctrl(mtwo, C->root());
1376     Node *rond = new (C) AndINode( trip, mtwo );
1377     register_new_node( rond, ctrl );
1378     Node *spn2 = new (C) MulINode( rond, stride );
1379     register_new_node( spn2, ctrl );
1380     new_limit = new (C) AddINode( spn2, init );
1381     register_new_node( new_limit, ctrl );
1382 
1383     // Hammer in the new limit
1384     Node *ctrl2 = loop_end->in(0);
1385     Node *cmp2 = new (C) CmpINode( loop_head->incr(), new_limit );
1386     register_new_node( cmp2, ctrl2 );
1387     Node *bol2 = new (C) BoolNode( cmp2, loop_end->test_trip() );
1388     register_new_node( bol2, ctrl2 );
1389     _igvn.hash_delete(loop_end);
1390     loop_end->set_req(CountedLoopEndNode::TestValue, bol2);
1391 
1392     // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1393     // Make it a 1-trip test (means at least 2 trips).
1394     if( adjust_min_trip ) {
1395       assert( new_limit != NULL, "" );
1396       // Guard test uses an 'opaque' node which is not shared.  Hence I
1397       // can edit it's inputs directly.  Hammer in the new limit for the
1398       // minimum-trip guard.
1399       assert( opaq->outcnt() == 1, "" );
1400       _igvn.hash_delete(opaq);
1401       opaq->set_req(1, new_limit);
1402     }
1403   } // LoopLimitCheck
1404 
1405   // ---------
1406   // Step 4: Clone the loop body.  Move it inside the loop.  This loop body
1407   // represents the odd iterations; since the loop trips an even number of
1408   // times its backedge is never taken.  Kill the backedge.
1409   uint dd = dom_depth(loop_head);
1410   clone_loop( loop, old_new, dd );
1411 
1412   // Make backedges of the clone equal to backedges of the original.
1413   // Make the fall-in from the original come from the fall-out of the clone.
1414   for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1415     Node* phi = loop_head->fast_out(j);
1416     if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1417       Node *newphi = old_new[phi->_idx];
1418       _igvn.hash_delete( phi );
1419       _igvn.hash_delete( newphi );
1420 
1421       phi   ->set_req(LoopNode::   EntryControl, newphi->in(LoopNode::LoopBackControl));
1422       newphi->set_req(LoopNode::LoopBackControl, phi   ->in(LoopNode::LoopBackControl));
1423       phi   ->set_req(LoopNode::LoopBackControl, C->top());
1424     }
1425   }
1426   Node *clone_head = old_new[loop_head->_idx];
1427   _igvn.hash_delete( clone_head );
1428   loop_head ->set_req(LoopNode::   EntryControl, clone_head->in(LoopNode::LoopBackControl));
1429   clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1430   loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1431   loop->_head = clone_head;     // New loop header
1432 
1433   set_idom(loop_head,  loop_head ->in(LoopNode::EntryControl), dd);
1434   set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1435 
1436   // Kill the clone's backedge
1437   Node *newcle = old_new[loop_end->_idx];
1438   _igvn.hash_delete( newcle );
1439   Node *one = _igvn.intcon(1);
1440   set_ctrl(one, C->root());
1441   newcle->set_req(1, one);
1442   // Force clone into same loop body
1443   uint max = loop->_body.size();
1444   for( uint k = 0; k < max; k++ ) {
1445     Node *old = loop->_body.at(k);
1446     Node *nnn = old_new[old->_idx];
1447     loop->_body.push(nnn);
1448     if (!has_ctrl(old))
1449       set_loop(nnn, loop);
1450   }
1451 
1452   loop->record_for_igvn();
1453 }
1454 
1455 //------------------------------do_maximally_unroll----------------------------
1456 
1457 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1458   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1459   assert(cl->has_exact_trip_count(), "trip count is not exact");
1460   assert(cl->trip_count() > 0, "");
1461 #ifndef PRODUCT
1462   if (TraceLoopOpts) {
1463     tty->print("MaxUnroll  %d ", cl->trip_count());
1464     loop->dump_head();
1465   }
1466 #endif
1467 
1468   // If loop is tripping an odd number of times, peel odd iteration
1469   if ((cl->trip_count() & 1) == 1) {
1470     do_peeling(loop, old_new);
1471   }
1472 
1473   // Now its tripping an even number of times remaining.  Double loop body.
1474   // Do not adjust pre-guards; they are not needed and do not exist.
1475   if (cl->trip_count() > 0) {
1476     assert((cl->trip_count() & 1) == 0, "missed peeling");
1477     do_unroll(loop, old_new, false);
1478   }
1479 }
1480 
1481 //------------------------------dominates_backedge---------------------------------
1482 // Returns true if ctrl is executed on every complete iteration
1483 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1484   assert(ctrl->is_CFG(), "must be control");
1485   Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1486   return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1487 }
1488 
1489 //------------------------------adjust_limit-----------------------------------
1490 // Helper function for add_constraint().
1491 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) {
1492   // Compute "I :: (limit-offset)/scale"
1493   Node *con = new (C) SubINode(rc_limit, offset);
1494   register_new_node(con, pre_ctrl);
1495   Node *X = new (C) DivINode(0, con, scale);
1496   register_new_node(X, pre_ctrl);
1497 
1498   // Adjust loop limit
1499   loop_limit = (stride_con > 0)
1500                ? (Node*)(new (C) MinINode(loop_limit, X))
1501                : (Node*)(new (C) MaxINode(loop_limit, X));
1502   register_new_node(loop_limit, pre_ctrl);
1503   return loop_limit;
1504 }
1505 
1506 //------------------------------add_constraint---------------------------------
1507 // Constrain the main loop iterations so the conditions:
1508 //    low_limit <= scale_con * I + offset  <  upper_limit
1509 // always holds true.  That is, either increase the number of iterations in
1510 // the pre-loop or the post-loop until the condition holds true in the main
1511 // loop.  Stride, scale, offset and limit are all loop invariant.  Further,
1512 // stride and scale are constants (offset and limit often are).
1513 void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *low_limit, Node *upper_limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) {
1514   // For positive stride, the pre-loop limit always uses a MAX function
1515   // and the main loop a MIN function.  For negative stride these are
1516   // reversed.
1517 
1518   // Also for positive stride*scale the affine function is increasing, so the
1519   // pre-loop must check for underflow and the post-loop for overflow.
1520   // Negative stride*scale reverses this; pre-loop checks for overflow and
1521   // post-loop for underflow.
1522 
1523   Node *scale = _igvn.intcon(scale_con);
1524   set_ctrl(scale, C->root());
1525 
1526   if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
1527     // The overflow limit: scale*I+offset < upper_limit
1528     // For main-loop compute
1529     //   ( if (scale > 0) /* and stride > 0 */
1530     //       I < (upper_limit-offset)/scale
1531     //     else /* scale < 0 and stride < 0 */
1532     //       I > (upper_limit-offset)/scale
1533     //   )
1534     //
1535     // (upper_limit-offset) may overflow or underflow.
1536     // But it is fine since main loop will either have
1537     // less iterations or will be skipped in such case.
1538     *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl);
1539 
1540     // The underflow limit: low_limit <= scale*I+offset.
1541     // For pre-loop compute
1542     //   NOT(scale*I+offset >= low_limit)
1543     //   scale*I+offset < low_limit
1544     //   ( if (scale > 0) /* and stride > 0 */
1545     //       I < (low_limit-offset)/scale
1546     //     else /* scale < 0 and stride < 0 */
1547     //       I > (low_limit-offset)/scale
1548     //   )
1549 
1550     if (low_limit->get_int() == -max_jint) {
1551       if (!RangeLimitCheck) return;
1552       // We need this guard when scale*pre_limit+offset >= limit
1553       // due to underflow. So we need execute pre-loop until
1554       // scale*I+offset >= min_int. But (min_int-offset) will
1555       // underflow when offset > 0 and X will be > original_limit
1556       // when stride > 0. To avoid it we replace positive offset with 0.
1557       //
1558       // Also (min_int+1 == -max_int) is used instead of min_int here
1559       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1560       Node* shift = _igvn.intcon(31);
1561       set_ctrl(shift, C->root());
1562       Node* sign = new (C) RShiftINode(offset, shift);
1563       register_new_node(sign, pre_ctrl);
1564       offset = new (C) AndINode(offset, sign);
1565       register_new_node(offset, pre_ctrl);
1566     } else {
1567       assert(low_limit->get_int() == 0, "wrong low limit for range check");
1568       // The only problem we have here when offset == min_int
1569       // since (0-min_int) == min_int. It may be fine for stride > 0
1570       // but for stride < 0 X will be < original_limit. To avoid it
1571       // max(pre_limit, original_limit) is used in do_range_check().
1572     }
1573     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1574     *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl);
1575 
1576   } else { // stride_con*scale_con < 0
1577     // For negative stride*scale pre-loop checks for overflow and
1578     // post-loop for underflow.
1579     //
1580     // The overflow limit: scale*I+offset < upper_limit
1581     // For pre-loop compute
1582     //   NOT(scale*I+offset < upper_limit)
1583     //   scale*I+offset >= upper_limit
1584     //   scale*I+offset+1 > upper_limit
1585     //   ( if (scale < 0) /* and stride > 0 */
1586     //       I < (upper_limit-(offset+1))/scale
1587     //     else /* scale > 0 and stride < 0 */
1588     //       I > (upper_limit-(offset+1))/scale
1589     //   )
1590     //
1591     // (upper_limit-offset-1) may underflow or overflow.
1592     // To avoid it min(pre_limit, original_limit) is used
1593     // in do_range_check() for stride > 0 and max() for < 0.
1594     Node *one  = _igvn.intcon(1);
1595     set_ctrl(one, C->root());
1596 
1597     Node *plus_one = new (C) AddINode(offset, one);
1598     register_new_node( plus_one, pre_ctrl );
1599     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1600     *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl);
1601 
1602     if (low_limit->get_int() == -max_jint) {
1603       if (!RangeLimitCheck) return;
1604       // We need this guard when scale*main_limit+offset >= limit
1605       // due to underflow. So we need execute main-loop while
1606       // scale*I+offset+1 > min_int. But (min_int-offset-1) will
1607       // underflow when (offset+1) > 0 and X will be < main_limit
1608       // when scale < 0 (and stride > 0). To avoid it we replace
1609       // positive (offset+1) with 0.
1610       //
1611       // Also (min_int+1 == -max_int) is used instead of min_int here
1612       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1613       Node* shift = _igvn.intcon(31);
1614       set_ctrl(shift, C->root());
1615       Node* sign = new (C) RShiftINode(plus_one, shift);
1616       register_new_node(sign, pre_ctrl);
1617       plus_one = new (C) AndINode(plus_one, sign);
1618       register_new_node(plus_one, pre_ctrl);
1619     } else {
1620       assert(low_limit->get_int() == 0, "wrong low limit for range check");
1621       // The only problem we have here when offset == max_int
1622       // since (max_int+1) == min_int and (0-min_int) == min_int.
1623       // But it is fine since main loop will either have
1624       // less iterations or will be skipped in such case.
1625     }
1626     // The underflow limit: low_limit <= scale*I+offset.
1627     // For main-loop compute
1628     //   scale*I+offset+1 > low_limit
1629     //   ( if (scale < 0) /* and stride > 0 */
1630     //       I < (low_limit-(offset+1))/scale
1631     //     else /* scale > 0 and stride < 0 */
1632     //       I > (low_limit-(offset+1))/scale
1633     //   )
1634 
1635     *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl);
1636   }
1637 }
1638 
1639 
1640 //------------------------------is_scaled_iv---------------------------------
1641 // Return true if exp is a constant times an induction var
1642 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1643   if (exp == iv) {
1644     if (p_scale != NULL) {
1645       *p_scale = 1;
1646     }
1647     return true;
1648   }
1649   int opc = exp->Opcode();
1650   if (opc == Op_MulI) {
1651     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1652       if (p_scale != NULL) {
1653         *p_scale = exp->in(2)->get_int();
1654       }
1655       return true;
1656     }
1657     if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1658       if (p_scale != NULL) {
1659         *p_scale = exp->in(1)->get_int();
1660       }
1661       return true;
1662     }
1663   } else if (opc == Op_LShiftI) {
1664     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1665       if (p_scale != NULL) {
1666         *p_scale = 1 << exp->in(2)->get_int();
1667       }
1668       return true;
1669     }
1670   }
1671   return false;
1672 }
1673 
1674 //-----------------------------is_scaled_iv_plus_offset------------------------------
1675 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1676 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1677   if (is_scaled_iv(exp, iv, p_scale)) {
1678     if (p_offset != NULL) {
1679       Node *zero = _igvn.intcon(0);
1680       set_ctrl(zero, C->root());
1681       *p_offset = zero;
1682     }
1683     return true;
1684   }
1685   int opc = exp->Opcode();
1686   if (opc == Op_AddI) {
1687     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1688       if (p_offset != NULL) {
1689         *p_offset = exp->in(2);
1690       }
1691       return true;
1692     }
1693     if (exp->in(2)->is_Con()) {
1694       Node* offset2 = NULL;
1695       if (depth < 2 &&
1696           is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
1697                                    p_offset != NULL ? &offset2 : NULL, depth+1)) {
1698         if (p_offset != NULL) {
1699           Node *ctrl_off2 = get_ctrl(offset2);
1700           Node* offset = new (C) AddINode(offset2, exp->in(2));
1701           register_new_node(offset, ctrl_off2);
1702           *p_offset = offset;
1703         }
1704         return true;
1705       }
1706     }
1707   } else if (opc == Op_SubI) {
1708     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1709       if (p_offset != NULL) {
1710         Node *zero = _igvn.intcon(0);
1711         set_ctrl(zero, C->root());
1712         Node *ctrl_off = get_ctrl(exp->in(2));
1713         Node* offset = new (C) SubINode(zero, exp->in(2));
1714         register_new_node(offset, ctrl_off);
1715         *p_offset = offset;
1716       }
1717       return true;
1718     }
1719     if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1720       if (p_offset != NULL) {
1721         *p_scale *= -1;
1722         *p_offset = exp->in(1);
1723       }
1724       return true;
1725     }
1726   }
1727   return false;
1728 }
1729 
1730 //------------------------------do_range_check---------------------------------
1731 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1732 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
1733 #ifndef PRODUCT
1734   if (PrintOpto && VerifyLoopOptimizations) {
1735     tty->print("Range Check Elimination ");
1736     loop->dump_head();
1737   } else if (TraceLoopOpts) {
1738     tty->print("RangeCheck   ");
1739     loop->dump_head();
1740   }
1741 #endif
1742   assert(RangeCheckElimination, "");
1743   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1744   assert(cl->is_main_loop(), "");
1745 
1746   // protect against stride not being a constant
1747   if (!cl->stride_is_con())
1748     return;
1749 
1750   // Find the trip counter; we are iteration splitting based on it
1751   Node *trip_counter = cl->phi();
1752   // Find the main loop limit; we will trim it's iterations
1753   // to not ever trip end tests
1754   Node *main_limit = cl->limit();
1755 
1756   // Need to find the main-loop zero-trip guard
1757   Node *ctrl  = cl->in(LoopNode::EntryControl);
1758   assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
1759   Node *iffm = ctrl->in(0);
1760   assert(iffm->Opcode() == Op_If, "");
1761   Node *bolzm = iffm->in(1);
1762   assert(bolzm->Opcode() == Op_Bool, "");
1763   Node *cmpzm = bolzm->in(1);
1764   assert(cmpzm->is_Cmp(), "");
1765   Node *opqzm = cmpzm->in(2);
1766   // Can not optimize a loop if zero-trip Opaque1 node is optimized
1767   // away and then another round of loop opts attempted.
1768   if (opqzm->Opcode() != Op_Opaque1)
1769     return;
1770   assert(opqzm->in(1) == main_limit, "do not understand situation");
1771 
1772   // Find the pre-loop limit; we will expand it's iterations to
1773   // not ever trip low tests.
1774   Node *p_f = iffm->in(0);
1775   assert(p_f->Opcode() == Op_IfFalse, "");
1776   CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
1777   assert(pre_end->loopnode()->is_pre_loop(), "");
1778   Node *pre_opaq1 = pre_end->limit();
1779   // Occasionally it's possible for a pre-loop Opaque1 node to be
1780   // optimized away and then another round of loop opts attempted.
1781   // We can not optimize this particular loop in that case.
1782   if (pre_opaq1->Opcode() != Op_Opaque1)
1783     return;
1784   Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
1785   Node *pre_limit = pre_opaq->in(1);
1786 
1787   // Where do we put new limit calculations
1788   Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
1789 
1790   // Ensure the original loop limit is available from the
1791   // pre-loop Opaque1 node.
1792   Node *orig_limit = pre_opaq->original_loop_limit();
1793   if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
1794     return;
1795 
1796   // Must know if its a count-up or count-down loop
1797 
1798   int stride_con = cl->stride_con();
1799   Node *zero = _igvn.intcon(0);
1800   Node *one  = _igvn.intcon(1);
1801   // Use symmetrical int range [-max_jint,max_jint]
1802   Node *mini = _igvn.intcon(-max_jint);
1803   set_ctrl(zero, C->root());
1804   set_ctrl(one,  C->root());
1805   set_ctrl(mini, C->root());
1806 
1807   // Range checks that do not dominate the loop backedge (ie.
1808   // conditionally executed) can lengthen the pre loop limit beyond
1809   // the original loop limit. To prevent this, the pre limit is
1810   // (for stride > 0) MINed with the original loop limit (MAXed
1811   // stride < 0) when some range_check (rc) is conditionally
1812   // executed.
1813   bool conditional_rc = false;
1814 
1815   // Check loop body for tests of trip-counter plus loop-invariant vs
1816   // loop-invariant.
1817   for( uint i = 0; i < loop->_body.size(); i++ ) {
1818     Node *iff = loop->_body[i];
1819     if( iff->Opcode() == Op_If ) { // Test?
1820 
1821       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
1822       // we need loop unswitching instead of iteration splitting.
1823       Node *exit = loop->is_loop_exit(iff);
1824       if( !exit ) continue;
1825       int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
1826 
1827       // Get boolean condition to test
1828       Node *i1 = iff->in(1);
1829       if( !i1->is_Bool() ) continue;
1830       BoolNode *bol = i1->as_Bool();
1831       BoolTest b_test = bol->_test;
1832       // Flip sense of test if exit condition is flipped
1833       if( flip )
1834         b_test = b_test.negate();
1835 
1836       // Get compare
1837       Node *cmp = bol->in(1);
1838 
1839       // Look for trip_counter + offset vs limit
1840       Node *rc_exp = cmp->in(1);
1841       Node *limit  = cmp->in(2);
1842       jint scale_con= 1;        // Assume trip counter not scaled
1843 
1844       Node *limit_c = get_ctrl(limit);
1845       if( loop->is_member(get_loop(limit_c) ) ) {
1846         // Compare might have operands swapped; commute them
1847         b_test = b_test.commute();
1848         rc_exp = cmp->in(2);
1849         limit  = cmp->in(1);
1850         limit_c = get_ctrl(limit);
1851         if( loop->is_member(get_loop(limit_c) ) )
1852           continue;             // Both inputs are loop varying; cannot RCE
1853       }
1854       // Here we know 'limit' is loop invariant
1855 
1856       // 'limit' maybe pinned below the zero trip test (probably from a
1857       // previous round of rce), in which case, it can't be used in the
1858       // zero trip test expression which must occur before the zero test's if.
1859       if( limit_c == ctrl ) {
1860         continue;  // Don't rce this check but continue looking for other candidates.
1861       }
1862 
1863       // Check for scaled induction variable plus an offset
1864       Node *offset = NULL;
1865 
1866       if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
1867         continue;
1868       }
1869 
1870       Node *offset_c = get_ctrl(offset);
1871       if( loop->is_member( get_loop(offset_c) ) )
1872         continue;               // Offset is not really loop invariant
1873       // Here we know 'offset' is loop invariant.
1874 
1875       // As above for the 'limit', the 'offset' maybe pinned below the
1876       // zero trip test.
1877       if( offset_c == ctrl ) {
1878         continue; // Don't rce this check but continue looking for other candidates.
1879       }
1880 #ifdef ASSERT
1881       if (TraceRangeLimitCheck) {
1882         tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
1883         bol->dump(2);
1884       }
1885 #endif
1886       // At this point we have the expression as:
1887       //   scale_con * trip_counter + offset :: limit
1888       // where scale_con, offset and limit are loop invariant.  Trip_counter
1889       // monotonically increases by stride_con, a constant.  Both (or either)
1890       // stride_con and scale_con can be negative which will flip about the
1891       // sense of the test.
1892 
1893       // Adjust pre and main loop limits to guard the correct iteration set
1894       if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
1895         if( b_test._test == BoolTest::lt ) { // Range checks always use lt
1896           // The underflow and overflow limits: 0 <= scale*I+offset < limit
1897           add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit );
1898           if (!conditional_rc) {
1899             // (0-offset)/scale could be outside of loop iterations range.
1900             conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1901           }
1902         } else {
1903 #ifndef PRODUCT
1904           if( PrintOpto )
1905             tty->print_cr("missed RCE opportunity");
1906 #endif
1907           continue;             // In release mode, ignore it
1908         }
1909       } else {                  // Otherwise work on normal compares
1910         switch( b_test._test ) {
1911         case BoolTest::gt:
1912           // Fall into GE case
1913         case BoolTest::ge:
1914           // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
1915           scale_con = -scale_con;
1916           offset = new (C) SubINode( zero, offset );
1917           register_new_node( offset, pre_ctrl );
1918           limit  = new (C) SubINode( zero, limit  );
1919           register_new_node( limit, pre_ctrl );
1920           // Fall into LE case
1921         case BoolTest::le:
1922           if (b_test._test != BoolTest::gt) {
1923             // Convert X <= Y to X < Y+1
1924             limit = new (C) AddINode( limit, one );
1925             register_new_node( limit, pre_ctrl );
1926           }
1927           // Fall into LT case
1928         case BoolTest::lt:
1929           // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
1930           // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
1931           // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
1932           add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit );
1933           if (!conditional_rc) {
1934             // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range.
1935             // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could
1936             // still be outside of loop range.
1937             conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1938           }
1939           break;
1940         default:
1941 #ifndef PRODUCT
1942           if( PrintOpto )
1943             tty->print_cr("missed RCE opportunity");
1944 #endif
1945           continue;             // Unhandled case
1946         }
1947       }
1948 
1949       // Kill the eliminated test
1950       C->set_major_progress();
1951       Node *kill_con = _igvn.intcon( 1-flip );
1952       set_ctrl(kill_con, C->root());
1953       _igvn.replace_input_of(iff, 1, kill_con);
1954       // Find surviving projection
1955       assert(iff->is_If(), "");
1956       ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
1957       // Find loads off the surviving projection; remove their control edge
1958       for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
1959         Node* cd = dp->fast_out(i); // Control-dependent node
1960         if( cd->is_Load() ) {   // Loads can now float around in the loop
1961           // Allow the load to float around in the loop, or before it
1962           // but NOT before the pre-loop.
1963           _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL
1964           --i;
1965           --imax;
1966         }
1967       }
1968 
1969     } // End of is IF
1970 
1971   }
1972 
1973   // Update loop limits
1974   if (conditional_rc) {
1975     pre_limit = (stride_con > 0) ? (Node*)new (C) MinINode(pre_limit, orig_limit)
1976                                  : (Node*)new (C) MaxINode(pre_limit, orig_limit);
1977     register_new_node(pre_limit, pre_ctrl);
1978   }
1979   _igvn.hash_delete(pre_opaq);
1980   pre_opaq->set_req(1, pre_limit);
1981 
1982   // Note:: we are making the main loop limit no longer precise;
1983   // need to round up based on stride.
1984   cl->set_nonexact_trip_count();
1985   if (!LoopLimitCheck && stride_con != 1 && stride_con != -1) { // Cutout for common case
1986     // "Standard" round-up logic:  ([main_limit-init+(y-1)]/y)*y+init
1987     // Hopefully, compiler will optimize for powers of 2.
1988     Node *ctrl = get_ctrl(main_limit);
1989     Node *stride = cl->stride();
1990     Node *init = cl->init_trip();
1991     Node *span = new (C) SubINode(main_limit,init);
1992     register_new_node(span,ctrl);
1993     Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
1994     Node *add = new (C) AddINode(span,rndup);
1995     register_new_node(add,ctrl);
1996     Node *div = new (C) DivINode(0,add,stride);
1997     register_new_node(div,ctrl);
1998     Node *mul = new (C) MulINode(div,stride);
1999     register_new_node(mul,ctrl);
2000     Node *newlim = new (C) AddINode(mul,init);
2001     register_new_node(newlim,ctrl);
2002     main_limit = newlim;
2003   }
2004 
2005   Node *main_cle = cl->loopexit();
2006   Node *main_bol = main_cle->in(1);
2007   // Hacking loop bounds; need private copies of exit test
2008   if( main_bol->outcnt() > 1 ) {// BoolNode shared?
2009     _igvn.hash_delete(main_cle);
2010     main_bol = main_bol->clone();// Clone a private BoolNode
2011     register_new_node( main_bol, main_cle->in(0) );
2012     main_cle->set_req(1,main_bol);
2013   }
2014   Node *main_cmp = main_bol->in(1);
2015   if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
2016     _igvn.hash_delete(main_bol);
2017     main_cmp = main_cmp->clone();// Clone a private CmpNode
2018     register_new_node( main_cmp, main_cle->in(0) );
2019     main_bol->set_req(1,main_cmp);
2020   }
2021   // Hack the now-private loop bounds
2022   _igvn.replace_input_of(main_cmp, 2, main_limit);
2023   // The OpaqueNode is unshared by design
2024   assert( opqzm->outcnt() == 1, "cannot hack shared node" );
2025   _igvn.replace_input_of(opqzm, 1, main_limit);
2026 }
2027 
2028 //------------------------------DCE_loop_body----------------------------------
2029 // Remove simplistic dead code from loop body
2030 void IdealLoopTree::DCE_loop_body() {
2031   for( uint i = 0; i < _body.size(); i++ )
2032     if( _body.at(i)->outcnt() == 0 )
2033       _body.map( i--, _body.pop() );
2034 }
2035 
2036 
2037 //------------------------------adjust_loop_exit_prob--------------------------
2038 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
2039 // Replace with a 1-in-10 exit guess.
2040 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
2041   Node *test = tail();
2042   while( test != _head ) {
2043     uint top = test->Opcode();
2044     if( top == Op_IfTrue || top == Op_IfFalse ) {
2045       int test_con = ((ProjNode*)test)->_con;
2046       assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
2047       IfNode *iff = test->in(0)->as_If();
2048       if( iff->outcnt() == 2 ) {        // Ignore dead tests
2049         Node *bol = iff->in(1);
2050         if( bol && bol->req() > 1 && bol->in(1) &&
2051             ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
2052              (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
2053              (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
2054              (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
2055              (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
2056              (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
2057              (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
2058           return;               // Allocation loops RARELY take backedge
2059         // Find the OTHER exit path from the IF
2060         Node* ex = iff->proj_out(1-test_con);
2061         float p = iff->_prob;
2062         if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
2063           if( top == Op_IfTrue ) {
2064             if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
2065               iff->_prob = PROB_STATIC_FREQUENT;
2066             }
2067           } else {
2068             if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
2069               iff->_prob = PROB_STATIC_INFREQUENT;
2070             }
2071           }
2072         }
2073       }
2074     }
2075     test = phase->idom(test);
2076   }
2077 }
2078 
2079 
2080 //------------------------------policy_do_remove_empty_loop--------------------
2081 // Micro-benchmark spamming.  Policy is to always remove empty loops.
2082 // The 'DO' part is to replace the trip counter with the value it will
2083 // have on the last iteration.  This will break the loop.
2084 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
2085   // Minimum size must be empty loop
2086   if (_body.size() > EMPTY_LOOP_SIZE)
2087     return false;
2088 
2089   if (!_head->is_CountedLoop())
2090     return false;     // Dead loop
2091   CountedLoopNode *cl = _head->as_CountedLoop();
2092   if (!cl->is_valid_counted_loop())
2093     return false; // Malformed loop
2094   if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
2095     return false;             // Infinite loop
2096 
2097 #ifdef ASSERT
2098   // Ensure only one phi which is the iv.
2099   Node* iv = NULL;
2100   for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
2101     Node* n = cl->fast_out(i);
2102     if (n->Opcode() == Op_Phi) {
2103       assert(iv == NULL, "Too many phis" );
2104       iv = n;
2105     }
2106   }
2107   assert(iv == cl->phi(), "Wrong phi" );
2108 #endif
2109 
2110   // main and post loops have explicitly created zero trip guard
2111   bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
2112   if (needs_guard) {
2113     // Skip guard if values not overlap.
2114     const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
2115     const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
2116     int  stride_con = cl->stride_con();
2117     if (stride_con > 0) {
2118       needs_guard = (init_t->_hi >= limit_t->_lo);
2119     } else {
2120       needs_guard = (init_t->_lo <= limit_t->_hi);
2121     }
2122   }
2123   if (needs_guard) {
2124     // Check for an obvious zero trip guard.
2125     Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl));
2126     if (inctrl->Opcode() == Op_IfTrue) {
2127       // The test should look like just the backedge of a CountedLoop
2128       Node* iff = inctrl->in(0);
2129       if (iff->is_If()) {
2130         Node* bol = iff->in(1);
2131         if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) {
2132           Node* cmp = bol->in(1);
2133           if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) {
2134             needs_guard = false;
2135           }
2136         }
2137       }
2138     }
2139   }
2140 
2141 #ifndef PRODUCT
2142   if (PrintOpto) {
2143     tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
2144     this->dump_head();
2145   } else if (TraceLoopOpts) {
2146     tty->print("Empty with%s zero trip guard   ", needs_guard ? "out" : "");
2147     this->dump_head();
2148   }
2149 #endif
2150 
2151   if (needs_guard) {
2152     // Peel the loop to ensure there's a zero trip guard
2153     Node_List old_new;
2154     phase->do_peeling(this, old_new);
2155   }
2156 
2157   // Replace the phi at loop head with the final value of the last
2158   // iteration.  Then the CountedLoopEnd will collapse (backedge never
2159   // taken) and all loop-invariant uses of the exit values will be correct.
2160   Node *phi = cl->phi();
2161   Node *exact_limit = phase->exact_limit(this);
2162   if (exact_limit != cl->limit()) {
2163     // We also need to replace the original limit to collapse loop exit.
2164     Node* cmp = cl->loopexit()->cmp_node();
2165     assert(cl->limit() == cmp->in(2), "sanity");
2166     phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
2167     phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist
2168   }
2169   // Note: the final value after increment should not overflow since
2170   // counted loop has limit check predicate.
2171   Node *final = new (phase->C) SubINode( exact_limit, cl->stride() );
2172   phase->register_new_node(final,cl->in(LoopNode::EntryControl));
2173   phase->_igvn.replace_node(phi,final);
2174   phase->C->set_major_progress();
2175   return true;
2176 }
2177 
2178 //------------------------------policy_do_one_iteration_loop-------------------
2179 // Convert one iteration loop into normal code.
2180 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) {
2181   if (!_head->as_Loop()->is_valid_counted_loop())
2182     return false; // Only for counted loop
2183 
2184   CountedLoopNode *cl = _head->as_CountedLoop();
2185   if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
2186     return false;
2187   }
2188 
2189 #ifndef PRODUCT
2190   if(TraceLoopOpts) {
2191     tty->print("OneIteration ");
2192     this->dump_head();
2193   }
2194 #endif
2195 
2196   Node *init_n = cl->init_trip();
2197 #ifdef ASSERT
2198   // Loop boundaries should be constant since trip count is exact.
2199   assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration");
2200 #endif
2201   // Replace the phi at loop head with the value of the init_trip.
2202   // Then the CountedLoopEnd will collapse (backedge will not be taken)
2203   // and all loop-invariant uses of the exit values will be correct.
2204   phase->_igvn.replace_node(cl->phi(), cl->init_trip());
2205   phase->C->set_major_progress();
2206   return true;
2207 }
2208 
2209 //=============================================================================
2210 //------------------------------iteration_split_impl---------------------------
2211 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
2212   // Compute exact loop trip count if possible.
2213   compute_exact_trip_count(phase);
2214 
2215   // Convert one iteration loop into normal code.
2216   if (policy_do_one_iteration_loop(phase))
2217     return true;
2218 
2219   // Check and remove empty loops (spam micro-benchmarks)
2220   if (policy_do_remove_empty_loop(phase))
2221     return true;  // Here we removed an empty loop
2222 
2223   bool should_peel = policy_peeling(phase); // Should we peel?
2224 
2225   bool should_unswitch = policy_unswitching(phase);
2226 
2227   // Non-counted loops may be peeled; exactly 1 iteration is peeled.
2228   // This removes loop-invariant tests (usually null checks).
2229   if (!_head->is_CountedLoop()) { // Non-counted loop
2230     if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
2231       // Partial peel succeeded so terminate this round of loop opts
2232       return false;
2233     }
2234     if (should_peel) {            // Should we peel?
2235 #ifndef PRODUCT
2236       if (PrintOpto) tty->print_cr("should_peel");
2237 #endif
2238       phase->do_peeling(this,old_new);
2239     } else if (should_unswitch) {
2240       phase->do_unswitching(this, old_new);
2241     }
2242     return true;
2243   }
2244   CountedLoopNode *cl = _head->as_CountedLoop();
2245 
2246   if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops
2247 
2248   // Do nothing special to pre- and post- loops
2249   if (cl->is_pre_loop() || cl->is_post_loop()) return true;
2250 
2251   // Compute loop trip count from profile data
2252   compute_profile_trip_cnt(phase);
2253 
2254   // Before attempting fancy unrolling, RCE or alignment, see if we want
2255   // to completely unroll this loop or do loop unswitching.
2256   if (cl->is_normal_loop()) {
2257     if (should_unswitch) {
2258       phase->do_unswitching(this, old_new);
2259       return true;
2260     }
2261     bool should_maximally_unroll =  policy_maximally_unroll(phase);
2262     if (should_maximally_unroll) {
2263       // Here we did some unrolling and peeling.  Eventually we will
2264       // completely unroll this loop and it will no longer be a loop.
2265       phase->do_maximally_unroll(this,old_new);
2266       return true;
2267     }
2268   }
2269 
2270   // Skip next optimizations if running low on nodes. Note that
2271   // policy_unswitching and policy_maximally_unroll have this check.
2272   uint nodes_left = MaxNodeLimit - (uint) phase->C->live_nodes();
2273   if ((2 * _body.size()) > nodes_left) {
2274     return true;
2275   }
2276 
2277   // Counted loops may be peeled, may need some iterations run up
2278   // front for RCE, and may want to align loop refs to a cache
2279   // line.  Thus we clone a full loop up front whose trip count is
2280   // at least 1 (if peeling), but may be several more.
2281 
2282   // The main loop will start cache-line aligned with at least 1
2283   // iteration of the unrolled body (zero-trip test required) and
2284   // will have some range checks removed.
2285 
2286   // A post-loop will finish any odd iterations (leftover after
2287   // unrolling), plus any needed for RCE purposes.
2288 
2289   bool should_unroll = policy_unroll(phase);
2290 
2291   bool should_rce = policy_range_check(phase);
2292 
2293   bool should_align = policy_align(phase);
2294 
2295   // If not RCE'ing (iteration splitting) or Aligning, then we do not
2296   // need a pre-loop.  We may still need to peel an initial iteration but
2297   // we will not be needing an unknown number of pre-iterations.
2298   //
2299   // Basically, if may_rce_align reports FALSE first time through,
2300   // we will not be able to later do RCE or Aligning on this loop.
2301   bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
2302 
2303   // If we have any of these conditions (RCE, alignment, unrolling) met, then
2304   // we switch to the pre-/main-/post-loop model.  This model also covers
2305   // peeling.
2306   if (should_rce || should_align || should_unroll) {
2307     if (cl->is_normal_loop())  // Convert to 'pre/main/post' loops
2308       phase->insert_pre_post_loops(this,old_new, !may_rce_align);
2309 
2310     // Adjust the pre- and main-loop limits to let the pre and post loops run
2311     // with full checks, but the main-loop with no checks.  Remove said
2312     // checks from the main body.
2313     if (should_rce)
2314       phase->do_range_check(this,old_new);
2315 
2316     // Double loop body for unrolling.  Adjust the minimum-trip test (will do
2317     // twice as many iterations as before) and the main body limit (only do
2318     // an even number of trips).  If we are peeling, we might enable some RCE
2319     // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
2320     // peeling.
2321     if (should_unroll && !should_peel)
2322       phase->do_unroll(this,old_new, true);
2323 
2324     // Adjust the pre-loop limits to align the main body
2325     // iterations.
2326     if (should_align)
2327       Unimplemented();
2328 
2329   } else {                      // Else we have an unchanged counted loop
2330     if (should_peel)           // Might want to peel but do nothing else
2331       phase->do_peeling(this,old_new);
2332   }
2333   return true;
2334 }
2335 
2336 
2337 //=============================================================================
2338 //------------------------------iteration_split--------------------------------
2339 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
2340   // Recursively iteration split nested loops
2341   if (_child && !_child->iteration_split(phase, old_new))
2342     return false;
2343 
2344   // Clean out prior deadwood
2345   DCE_loop_body();
2346 
2347 
2348   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
2349   // Replace with a 1-in-10 exit guess.
2350   if (_parent /*not the root loop*/ &&
2351       !_irreducible &&
2352       // Also ignore the occasional dead backedge
2353       !tail()->is_top()) {
2354     adjust_loop_exit_prob(phase);
2355   }
2356 
2357   // Gate unrolling, RCE and peeling efforts.
2358   if (!_child &&                // If not an inner loop, do not split
2359       !_irreducible &&
2360       _allow_optimizations &&
2361       !tail()->is_top()) {     // Also ignore the occasional dead backedge
2362     if (!_has_call) {
2363         if (!iteration_split_impl(phase, old_new)) {
2364           return false;
2365         }
2366     } else if (policy_unswitching(phase)) {
2367       phase->do_unswitching(this, old_new);
2368     }
2369   }
2370 
2371   // Minor offset re-organization to remove loop-fallout uses of
2372   // trip counter when there was no major reshaping.
2373   phase->reorg_offsets(this);
2374 
2375   if (_next && !_next->iteration_split(phase, old_new))
2376     return false;
2377   return true;
2378 }
2379 
2380 
2381 //=============================================================================
2382 // Process all the loops in the loop tree and replace any fill
2383 // patterns with an intrisc version.
2384 bool PhaseIdealLoop::do_intrinsify_fill() {
2385   bool changed = false;
2386   for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2387     IdealLoopTree* lpt = iter.current();
2388     changed |= intrinsify_fill(lpt);
2389   }
2390   return changed;
2391 }
2392 
2393 
2394 // Examine an inner loop looking for a a single store of an invariant
2395 // value in a unit stride loop,
2396 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
2397                                      Node*& shift, Node*& con) {
2398   const char* msg = NULL;
2399   Node* msg_node = NULL;
2400 
2401   store_value = NULL;
2402   con = NULL;
2403   shift = NULL;
2404 
2405   // Process the loop looking for stores.  If there are multiple
2406   // stores or extra control flow give at this point.
2407   CountedLoopNode* head = lpt->_head->as_CountedLoop();
2408   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2409     Node* n = lpt->_body.at(i);
2410     if (n->outcnt() == 0) continue; // Ignore dead
2411     if (n->is_Store()) {
2412       if (store != NULL) {
2413         msg = "multiple stores";
2414         break;
2415       }
2416       int opc = n->Opcode();
2417       if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass || opc == Op_StoreCM) {
2418         msg = "oop fills not handled";
2419         break;
2420       }
2421       Node* value = n->in(MemNode::ValueIn);
2422       if (!lpt->is_invariant(value)) {
2423         msg  = "variant store value";
2424       } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
2425         msg = "not array address";
2426       }
2427       store = n;
2428       store_value = value;
2429     } else if (n->is_If() && n != head->loopexit()) {
2430       msg = "extra control flow";
2431       msg_node = n;
2432     }
2433   }
2434 
2435   if (store == NULL) {
2436     // No store in loop
2437     return false;
2438   }
2439 
2440   if (msg == NULL && head->stride_con() != 1) {
2441     // could handle negative strides too
2442     if (head->stride_con() < 0) {
2443       msg = "negative stride";
2444     } else {
2445       msg = "non-unit stride";
2446     }
2447   }
2448 
2449   if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
2450     msg = "can't handle store address";
2451     msg_node = store->in(MemNode::Address);
2452   }
2453 
2454   if (msg == NULL &&
2455       (!store->in(MemNode::Memory)->is_Phi() ||
2456        store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
2457     msg = "store memory isn't proper phi";
2458     msg_node = store->in(MemNode::Memory);
2459   }
2460 
2461   // Make sure there is an appropriate fill routine
2462   BasicType t = store->as_Mem()->memory_type();
2463   const char* fill_name;
2464   if (msg == NULL &&
2465       StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
2466     msg = "unsupported store";
2467     msg_node = store;
2468   }
2469 
2470   if (msg != NULL) {
2471 #ifndef PRODUCT
2472     if (TraceOptimizeFill) {
2473       tty->print_cr("not fill intrinsic candidate: %s", msg);
2474       if (msg_node != NULL) msg_node->dump();
2475     }
2476 #endif
2477     return false;
2478   }
2479 
2480   // Make sure the address expression can be handled.  It should be
2481   // head->phi * elsize + con.  head->phi might have a ConvI2L.
2482   Node* elements[4];
2483   Node* conv = NULL;
2484   bool found_index = false;
2485   int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
2486   for (int e = 0; e < count; e++) {
2487     Node* n = elements[e];
2488     if (n->is_Con() && con == NULL) {
2489       con = n;
2490     } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
2491       Node* value = n->in(1);
2492 #ifdef _LP64
2493       if (value->Opcode() == Op_ConvI2L) {
2494         conv = value;
2495         value = value->in(1);
2496       }
2497 #endif
2498       if (value != head->phi()) {
2499         msg = "unhandled shift in address";
2500       } else {
2501         if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) {
2502           msg = "scale doesn't match";
2503         } else {
2504           found_index = true;
2505           shift = n;
2506         }
2507       }
2508     } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
2509       if (n->in(1) == head->phi()) {
2510         found_index = true;
2511         conv = n;
2512       } else {
2513         msg = "unhandled input to ConvI2L";
2514       }
2515     } else if (n == head->phi()) {
2516       // no shift, check below for allowed cases
2517       found_index = true;
2518     } else {
2519       msg = "unhandled node in address";
2520       msg_node = n;
2521     }
2522   }
2523 
2524   if (count == -1) {
2525     msg = "malformed address expression";
2526     msg_node = store;
2527   }
2528 
2529   if (!found_index) {
2530     msg = "missing use of index";
2531   }
2532 
2533   // byte sized items won't have a shift
2534   if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
2535     msg = "can't find shift";
2536     msg_node = store;
2537   }
2538 
2539   if (msg != NULL) {
2540 #ifndef PRODUCT
2541     if (TraceOptimizeFill) {
2542       tty->print_cr("not fill intrinsic: %s", msg);
2543       if (msg_node != NULL) msg_node->dump();
2544     }
2545 #endif
2546     return false;
2547   }
2548 
2549   // No make sure all the other nodes in the loop can be handled
2550   VectorSet ok(Thread::current()->resource_area());
2551 
2552   // store related values are ok
2553   ok.set(store->_idx);
2554   ok.set(store->in(MemNode::Memory)->_idx);
2555 
2556   CountedLoopEndNode* loop_exit = head->loopexit();
2557   guarantee(loop_exit != NULL, "no loop exit node");
2558 
2559   // Loop structure is ok
2560   ok.set(head->_idx);
2561   ok.set(loop_exit->_idx);
2562   ok.set(head->phi()->_idx);
2563   ok.set(head->incr()->_idx);
2564   ok.set(loop_exit->cmp_node()->_idx);
2565   ok.set(loop_exit->in(1)->_idx);
2566 
2567   // Address elements are ok
2568   if (con)   ok.set(con->_idx);
2569   if (shift) ok.set(shift->_idx);
2570   if (conv)  ok.set(conv->_idx);
2571 
2572   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2573     Node* n = lpt->_body.at(i);
2574     if (n->outcnt() == 0) continue; // Ignore dead
2575     if (ok.test(n->_idx)) continue;
2576     // Backedge projection is ok
2577     if (n->is_IfTrue() && n->in(0) == loop_exit) continue;
2578     if (!n->is_AddP()) {
2579       msg = "unhandled node";
2580       msg_node = n;
2581       break;
2582     }
2583   }
2584 
2585   // Make sure no unexpected values are used outside the loop
2586   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2587     Node* n = lpt->_body.at(i);
2588     // These values can be replaced with other nodes if they are used
2589     // outside the loop.
2590     if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue;
2591     for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
2592       Node* use = iter.get();
2593       if (!lpt->_body.contains(use)) {
2594         msg = "node is used outside loop";
2595         // lpt->_body.dump();
2596         msg_node = n;
2597         break;
2598       }
2599     }
2600   }
2601 
2602 #ifdef ASSERT
2603   if (TraceOptimizeFill) {
2604     if (msg != NULL) {
2605       tty->print_cr("no fill intrinsic: %s", msg);
2606       if (msg_node != NULL) msg_node->dump();
2607     } else {
2608       tty->print_cr("fill intrinsic for:");
2609     }
2610     store->dump();
2611     if (Verbose) {
2612       lpt->_body.dump();
2613     }
2614   }
2615 #endif
2616 
2617   return msg == NULL;
2618 }
2619 
2620 
2621 
2622 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
2623   // Only for counted inner loops
2624   if (!lpt->is_counted() || !lpt->is_inner()) {
2625     return false;
2626   }
2627 
2628   // Must have constant stride
2629   CountedLoopNode* head = lpt->_head->as_CountedLoop();
2630   if (!head->is_valid_counted_loop() || !head->is_normal_loop()) {
2631     return false;
2632   }
2633 
2634   // Check that the body only contains a store of a loop invariant
2635   // value that is indexed by the loop phi.
2636   Node* store = NULL;
2637   Node* store_value = NULL;
2638   Node* shift = NULL;
2639   Node* offset = NULL;
2640   if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
2641     return false;
2642   }
2643 
2644 #ifndef PRODUCT
2645   if (TraceLoopOpts) {
2646     tty->print("ArrayFill    ");
2647     lpt->dump_head();
2648   }
2649 #endif
2650 
2651   // Now replace the whole loop body by a call to a fill routine that
2652   // covers the same region as the loop.
2653   Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
2654 
2655   // Build an expression for the beginning of the copy region
2656   Node* index = head->init_trip();
2657 #ifdef _LP64
2658   index = new (C) ConvI2LNode(index);
2659   _igvn.register_new_node_with_optimizer(index);
2660 #endif
2661   if (shift != NULL) {
2662     // byte arrays don't require a shift but others do.
2663     index = new (C) LShiftXNode(index, shift->in(2));
2664     _igvn.register_new_node_with_optimizer(index);
2665   }
2666   index = new (C) AddPNode(base, base, index);
2667   _igvn.register_new_node_with_optimizer(index);
2668   Node* from = new (C) AddPNode(base, index, offset);
2669   _igvn.register_new_node_with_optimizer(from);
2670   // Compute the number of elements to copy
2671   Node* len = new (C) SubINode(head->limit(), head->init_trip());
2672   _igvn.register_new_node_with_optimizer(len);
2673 
2674   BasicType t = store->as_Mem()->memory_type();
2675   bool aligned = false;
2676   if (offset != NULL && head->init_trip()->is_Con()) {
2677     int element_size = type2aelembytes(t);
2678     aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
2679   }
2680 
2681   // Build a call to the fill routine
2682   const char* fill_name;
2683   address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
2684   assert(fill != NULL, "what?");
2685 
2686   // Convert float/double to int/long for fill routines
2687   if (t == T_FLOAT) {
2688     store_value = new (C) MoveF2INode(store_value);
2689     _igvn.register_new_node_with_optimizer(store_value);
2690   } else if (t == T_DOUBLE) {
2691     store_value = new (C) MoveD2LNode(store_value);
2692     _igvn.register_new_node_with_optimizer(store_value);
2693   }
2694 
2695   if (CCallingConventionRequiresIntsAsLongs &&
2696       // See StubRoutines::select_fill_function for types. FLOAT has been converted to INT.
2697       (t == T_FLOAT || t == T_INT ||  is_subword_type(t))) {
2698     store_value = new (C) ConvI2LNode(store_value);
2699     _igvn.register_new_node_with_optimizer(store_value);
2700   }
2701 
2702   Node* mem_phi = store->in(MemNode::Memory);
2703   Node* result_ctrl;
2704   Node* result_mem;
2705   const TypeFunc* call_type = OptoRuntime::array_fill_Type();
2706   CallLeafNode *call = new (C) CallLeafNoFPNode(call_type, fill,
2707                                                 fill_name, TypeAryPtr::get_array_body_type(t));
2708   uint cnt = 0;
2709   call->init_req(TypeFunc::Parms + cnt++, from);
2710   call->init_req(TypeFunc::Parms + cnt++, store_value);
2711   if (CCallingConventionRequiresIntsAsLongs) {
2712     call->init_req(TypeFunc::Parms + cnt++, C->top());
2713   }
2714 #ifdef _LP64
2715   len = new (C) ConvI2LNode(len);
2716   _igvn.register_new_node_with_optimizer(len);
2717 #endif
2718   call->init_req(TypeFunc::Parms + cnt++, len);
2719 #ifdef _LP64
2720   call->init_req(TypeFunc::Parms + cnt++, C->top());
2721 #endif
2722   call->init_req(TypeFunc::Control,   head->init_control());
2723   call->init_req(TypeFunc::I_O,       C->top());       // Does no I/O.
2724   call->init_req(TypeFunc::Memory,    mem_phi->in(LoopNode::EntryControl));
2725   call->init_req(TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr));
2726   call->init_req(TypeFunc::FramePtr,  C->start()->proj_out(TypeFunc::FramePtr));
2727   _igvn.register_new_node_with_optimizer(call);
2728   result_ctrl = new (C) ProjNode(call,TypeFunc::Control);
2729   _igvn.register_new_node_with_optimizer(result_ctrl);
2730   result_mem = new (C) ProjNode(call,TypeFunc::Memory);
2731   _igvn.register_new_node_with_optimizer(result_mem);
2732 
2733 /* Disable following optimization until proper fix (add missing checks).
2734 
2735   // If this fill is tightly coupled to an allocation and overwrites
2736   // the whole body, allow it to take over the zeroing.
2737   AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
2738   if (alloc != NULL && alloc->is_AllocateArray()) {
2739     Node* length = alloc->as_AllocateArray()->Ideal_length();
2740     if (head->limit() == length &&
2741         head->init_trip() == _igvn.intcon(0)) {
2742       if (TraceOptimizeFill) {
2743         tty->print_cr("Eliminated zeroing in allocation");
2744       }
2745       alloc->maybe_set_complete(&_igvn);
2746     } else {
2747 #ifdef ASSERT
2748       if (TraceOptimizeFill) {
2749         tty->print_cr("filling array but bounds don't match");
2750         alloc->dump();
2751         head->init_trip()->dump();
2752         head->limit()->dump();
2753         length->dump();
2754       }
2755 #endif
2756     }
2757   }
2758 */
2759 
2760   // Redirect the old control and memory edges that are outside the loop.
2761   Node* exit = head->loopexit()->proj_out(0);
2762   // Sometimes the memory phi of the head is used as the outgoing
2763   // state of the loop.  It's safe in this case to replace it with the
2764   // result_mem.
2765   _igvn.replace_node(store->in(MemNode::Memory), result_mem);
2766   _igvn.replace_node(exit, result_ctrl);
2767   _igvn.replace_node(store, result_mem);
2768   // Any uses the increment outside of the loop become the loop limit.
2769   _igvn.replace_node(head->incr(), head->limit());
2770 
2771   // Disconnect the head from the loop.
2772   for (uint i = 0; i < lpt->_body.size(); i++) {
2773     Node* n = lpt->_body.at(i);
2774     _igvn.replace_node(n, C->top());
2775   }
2776 
2777   return true;
2778 }