1 /*
   2  * Copyright (c) 2000, 2013, 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       Node *rc_exp = cmp->in(1);
 780       Node *limit = cmp->in(2);
 781 
 782       Node *limit_c = phase->get_ctrl(limit);
 783       if( limit_c == phase->C->top() )
 784         return false;           // Found dead test on live IF?  No RCE!
 785       if( is_member(phase->get_loop(limit_c) ) ) {
 786         // Compare might have operands swapped; commute them
 787         rc_exp = cmp->in(2);
 788         limit  = cmp->in(1);
 789         limit_c = phase->get_ctrl(limit);
 790         if( is_member(phase->get_loop(limit_c) ) )
 791           continue;             // Both inputs are loop varying; cannot RCE
 792       }
 793 
 794       if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
 795         continue;
 796       }
 797       // Yeah!  Found a test like 'trip+off vs limit'
 798       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
 799       // we need loop unswitching instead of iteration splitting.
 800       if( is_loop_exit(iff) )
 801         return true;            // Found reason to split iterations
 802     } // End of is IF
 803   }
 804 
 805   return false;
 806 }
 807 
 808 //------------------------------policy_peel_only-------------------------------
 809 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned.  Useful
 810 // for unrolling loops with NO array accesses.
 811 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
 812 
 813   for( uint i = 0; i < _body.size(); i++ )
 814     if( _body[i]->is_Mem() )
 815       return false;
 816 
 817   // No memory accesses at all!
 818   return true;
 819 }
 820 
 821 //------------------------------clone_up_backedge_goo--------------------------
 822 // If Node n lives in the back_ctrl block and cannot float, we clone a private
 823 // version of n in preheader_ctrl block and return that, otherwise return n.
 824 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) {
 825   if( get_ctrl(n) != back_ctrl ) return n;
 826 
 827   // Only visit once
 828   if (visited.test_set(n->_idx)) {
 829     Node *x = clones.find(n->_idx);
 830     if (x != NULL)
 831       return x;
 832     return n;
 833   }
 834 
 835   Node *x = NULL;               // If required, a clone of 'n'
 836   // Check for 'n' being pinned in the backedge.
 837   if( n->in(0) && n->in(0) == back_ctrl ) {
 838     assert(clones.find(n->_idx) == NULL, "dead loop");
 839     x = n->clone();             // Clone a copy of 'n' to preheader
 840     clones.push(x, n->_idx);
 841     x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
 842   }
 843 
 844   // Recursive fixup any other input edges into x.
 845   // If there are no changes we can just return 'n', otherwise
 846   // we need to clone a private copy and change it.
 847   for( uint i = 1; i < n->req(); i++ ) {
 848     Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones );
 849     if( g != n->in(i) ) {
 850       if( !x ) {
 851         assert(clones.find(n->_idx) == NULL, "dead loop");
 852         x = n->clone();
 853         clones.push(x, n->_idx);
 854       }
 855       x->set_req(i, g);
 856     }
 857   }
 858   if( x ) {                     // x can legally float to pre-header location
 859     register_new_node( x, preheader_ctrl );
 860     return x;
 861   } else {                      // raise n to cover LCA of uses
 862     set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
 863   }
 864   return n;
 865 }
 866 
 867 //------------------------------insert_pre_post_loops--------------------------
 868 // Insert pre and post loops.  If peel_only is set, the pre-loop can not have
 869 // more iterations added.  It acts as a 'peel' only, no lower-bound RCE, no
 870 // alignment.  Useful to unroll loops that do no array accesses.
 871 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
 872 
 873 #ifndef PRODUCT
 874   if (TraceLoopOpts) {
 875     if (peel_only)
 876       tty->print("PeelMainPost ");
 877     else
 878       tty->print("PreMainPost  ");
 879     loop->dump_head();
 880   }
 881 #endif
 882   C->set_major_progress();
 883 
 884   // Find common pieces of the loop being guarded with pre & post loops
 885   CountedLoopNode *main_head = loop->_head->as_CountedLoop();
 886   assert( main_head->is_normal_loop(), "" );
 887   CountedLoopEndNode *main_end = main_head->loopexit();
 888   guarantee(main_end != NULL, "no loop exit node");
 889   assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
 890   uint dd_main_head = dom_depth(main_head);
 891   uint max = main_head->outcnt();
 892 
 893   Node *pre_header= main_head->in(LoopNode::EntryControl);
 894   Node *init      = main_head->init_trip();
 895   Node *incr      = main_end ->incr();
 896   Node *limit     = main_end ->limit();
 897   Node *stride    = main_end ->stride();
 898   Node *cmp       = main_end ->cmp_node();
 899   BoolTest::mask b_test = main_end->test_trip();
 900 
 901   // Need only 1 user of 'bol' because I will be hacking the loop bounds.
 902   Node *bol = main_end->in(CountedLoopEndNode::TestValue);
 903   if( bol->outcnt() != 1 ) {
 904     bol = bol->clone();
 905     register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
 906     _igvn.hash_delete(main_end);
 907     main_end->set_req(CountedLoopEndNode::TestValue, bol);
 908   }
 909   // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
 910   if( cmp->outcnt() != 1 ) {
 911     cmp = cmp->clone();
 912     register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
 913     _igvn.hash_delete(bol);
 914     bol->set_req(1, cmp);
 915   }
 916 
 917   //------------------------------
 918   // Step A: Create Post-Loop.
 919   Node* main_exit = main_end->proj_out(false);
 920   assert( main_exit->Opcode() == Op_IfFalse, "" );
 921   int dd_main_exit = dom_depth(main_exit);
 922 
 923   // Step A1: Clone the loop body.  The clone becomes the post-loop.  The main
 924   // loop pre-header illegally has 2 control users (old & new loops).
 925   clone_loop( loop, old_new, dd_main_exit );
 926   assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
 927   CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
 928   post_head->set_post_loop(main_head);
 929 
 930   // Reduce the post-loop trip count.
 931   CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
 932   post_end->_prob = PROB_FAIR;
 933 
 934   // Build the main-loop normal exit.
 935   IfFalseNode *new_main_exit = new (C) IfFalseNode(main_end);
 936   _igvn.register_new_node_with_optimizer( new_main_exit );
 937   set_idom(new_main_exit, main_end, dd_main_exit );
 938   set_loop(new_main_exit, loop->_parent);
 939 
 940   // Step A2: Build a zero-trip guard for the post-loop.  After leaving the
 941   // main-loop, the post-loop may not execute at all.  We 'opaque' the incr
 942   // (the main-loop trip-counter exit value) because we will be changing
 943   // the exit value (via unrolling) so we cannot constant-fold away the zero
 944   // trip guard until all unrolling is done.
 945   Node *zer_opaq = new (C) Opaque1Node(C, incr);
 946   Node *zer_cmp  = new (C) CmpINode( zer_opaq, limit );
 947   Node *zer_bol  = new (C) BoolNode( zer_cmp, b_test );
 948   register_new_node( zer_opaq, new_main_exit );
 949   register_new_node( zer_cmp , new_main_exit );
 950   register_new_node( zer_bol , new_main_exit );
 951 
 952   // Build the IfNode
 953   IfNode *zer_iff = new (C) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
 954   _igvn.register_new_node_with_optimizer( zer_iff );
 955   set_idom(zer_iff, new_main_exit, dd_main_exit);
 956   set_loop(zer_iff, loop->_parent);
 957 
 958   // Plug in the false-path, taken if we need to skip post-loop
 959   _igvn.replace_input_of(main_exit, 0, zer_iff);
 960   set_idom(main_exit, zer_iff, dd_main_exit);
 961   set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
 962   // Make the true-path, must enter the post loop
 963   Node *zer_taken = new (C) IfTrueNode( zer_iff );
 964   _igvn.register_new_node_with_optimizer( zer_taken );
 965   set_idom(zer_taken, zer_iff, dd_main_exit);
 966   set_loop(zer_taken, loop->_parent);
 967   // Plug in the true path
 968   _igvn.hash_delete( post_head );
 969   post_head->set_req(LoopNode::EntryControl, zer_taken);
 970   set_idom(post_head, zer_taken, dd_main_exit);
 971 
 972   Arena *a = Thread::current()->resource_area();
 973   VectorSet visited(a);
 974   Node_Stack clones(a, main_head->back_control()->outcnt());
 975   // Step A3: Make the fall-in values to the post-loop come from the
 976   // fall-out values of the main-loop.
 977   for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
 978     Node* main_phi = main_head->fast_out(i);
 979     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
 980       Node *post_phi = old_new[main_phi->_idx];
 981       Node *fallmain  = clone_up_backedge_goo(main_head->back_control(),
 982                                               post_head->init_control(),
 983                                               main_phi->in(LoopNode::LoopBackControl),
 984                                               visited, clones);
 985       _igvn.hash_delete(post_phi);
 986       post_phi->set_req( LoopNode::EntryControl, fallmain );
 987     }
 988   }
 989 
 990   // Update local caches for next stanza
 991   main_exit = new_main_exit;
 992 
 993 
 994   //------------------------------
 995   // Step B: Create Pre-Loop.
 996 
 997   // Step B1: Clone the loop body.  The clone becomes the pre-loop.  The main
 998   // loop pre-header illegally has 2 control users (old & new loops).
 999   clone_loop( loop, old_new, dd_main_head );
1000   CountedLoopNode*    pre_head = old_new[main_head->_idx]->as_CountedLoop();
1001   CountedLoopEndNode* pre_end  = old_new[main_end ->_idx]->as_CountedLoopEnd();
1002   pre_head->set_pre_loop(main_head);
1003   Node *pre_incr = old_new[incr->_idx];
1004 
1005   // Reduce the pre-loop trip count.
1006   pre_end->_prob = PROB_FAIR;
1007 
1008   // Find the pre-loop normal exit.
1009   Node* pre_exit = pre_end->proj_out(false);
1010   assert( pre_exit->Opcode() == Op_IfFalse, "" );
1011   IfFalseNode *new_pre_exit = new (C) IfFalseNode(pre_end);
1012   _igvn.register_new_node_with_optimizer( new_pre_exit );
1013   set_idom(new_pre_exit, pre_end, dd_main_head);
1014   set_loop(new_pre_exit, loop->_parent);
1015 
1016   // Step B2: Build a zero-trip guard for the main-loop.  After leaving the
1017   // pre-loop, the main-loop may not execute at all.  Later in life this
1018   // zero-trip guard will become the minimum-trip guard when we unroll
1019   // the main-loop.
1020   Node *min_opaq = new (C) Opaque1Node(C, limit);
1021   Node *min_cmp  = new (C) CmpINode( pre_incr, min_opaq );
1022   Node *min_bol  = new (C) BoolNode( min_cmp, b_test );
1023   register_new_node( min_opaq, new_pre_exit );
1024   register_new_node( min_cmp , new_pre_exit );
1025   register_new_node( min_bol , new_pre_exit );
1026 
1027   // Build the IfNode (assume the main-loop is executed always).
1028   IfNode *min_iff = new (C) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
1029   _igvn.register_new_node_with_optimizer( min_iff );
1030   set_idom(min_iff, new_pre_exit, dd_main_head);
1031   set_loop(min_iff, loop->_parent);
1032 
1033   // Plug in the false-path, taken if we need to skip main-loop
1034   _igvn.hash_delete( pre_exit );
1035   pre_exit->set_req(0, min_iff);
1036   set_idom(pre_exit, min_iff, dd_main_head);
1037   set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
1038   // Make the true-path, must enter the main loop
1039   Node *min_taken = new (C) IfTrueNode( min_iff );
1040   _igvn.register_new_node_with_optimizer( min_taken );
1041   set_idom(min_taken, min_iff, dd_main_head);
1042   set_loop(min_taken, loop->_parent);
1043   // Plug in the true path
1044   _igvn.hash_delete( main_head );
1045   main_head->set_req(LoopNode::EntryControl, min_taken);
1046   set_idom(main_head, min_taken, dd_main_head);
1047 
1048   visited.Clear();
1049   clones.clear();
1050   // Step B3: Make the fall-in values to the main-loop come from the
1051   // fall-out values of the pre-loop.
1052   for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
1053     Node* main_phi = main_head->fast_out(i2);
1054     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
1055       Node *pre_phi = old_new[main_phi->_idx];
1056       Node *fallpre  = clone_up_backedge_goo(pre_head->back_control(),
1057                                              main_head->init_control(),
1058                                              pre_phi->in(LoopNode::LoopBackControl),
1059                                              visited, clones);
1060       _igvn.hash_delete(main_phi);
1061       main_phi->set_req( LoopNode::EntryControl, fallpre );
1062     }
1063   }
1064 
1065   // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1066   // RCE and alignment may change this later.
1067   Node *cmp_end = pre_end->cmp_node();
1068   assert( cmp_end->in(2) == limit, "" );
1069   Node *pre_limit = new (C) AddINode( init, stride );
1070 
1071   // Save the original loop limit in this Opaque1 node for
1072   // use by range check elimination.
1073   Node *pre_opaq  = new (C) Opaque1Node(C, pre_limit, limit);
1074 
1075   register_new_node( pre_limit, pre_head->in(0) );
1076   register_new_node( pre_opaq , pre_head->in(0) );
1077 
1078   // Since no other users of pre-loop compare, I can hack limit directly
1079   assert( cmp_end->outcnt() == 1, "no other users" );
1080   _igvn.hash_delete(cmp_end);
1081   cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
1082 
1083   // Special case for not-equal loop bounds:
1084   // Change pre loop test, main loop test, and the
1085   // main loop guard test to use lt or gt depending on stride
1086   // direction:
1087   // positive stride use <
1088   // negative stride use >
1089   //
1090   // not-equal test is kept for post loop to handle case
1091   // when init > limit when stride > 0 (and reverse).
1092 
1093   if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
1094 
1095     BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
1096     // Modify pre loop end condition
1097     Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1098     BoolNode* new_bol0 = new (C) BoolNode(pre_bol->in(1), new_test);
1099     register_new_node( new_bol0, pre_head->in(0) );
1100     _igvn.hash_delete(pre_end);
1101     pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0);
1102     // Modify main loop guard condition
1103     assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
1104     BoolNode* new_bol1 = new (C) BoolNode(min_bol->in(1), new_test);
1105     register_new_node( new_bol1, new_pre_exit );
1106     _igvn.hash_delete(min_iff);
1107     min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
1108     // Modify main loop end condition
1109     BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1110     BoolNode* new_bol2 = new (C) BoolNode(main_bol->in(1), new_test);
1111     register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
1112     _igvn.hash_delete(main_end);
1113     main_end->set_req(CountedLoopEndNode::TestValue, new_bol2);
1114   }
1115 
1116   // Flag main loop
1117   main_head->set_main_loop();
1118   if( peel_only ) main_head->set_main_no_pre_loop();
1119 
1120   // Subtract a trip count for the pre-loop.
1121   main_head->set_trip_count(main_head->trip_count() - 1);
1122 
1123   // It's difficult to be precise about the trip-counts
1124   // for the pre/post loops.  They are usually very short,
1125   // so guess that 4 trips is a reasonable value.
1126   post_head->set_profile_trip_cnt(4.0);
1127   pre_head->set_profile_trip_cnt(4.0);
1128 
1129   // Now force out all loop-invariant dominating tests.  The optimizer
1130   // finds some, but we _know_ they are all useless.
1131   peeled_dom_test_elim(loop,old_new);
1132 }
1133 
1134 //------------------------------is_invariant-----------------------------
1135 // Return true if n is invariant
1136 bool IdealLoopTree::is_invariant(Node* n) const {
1137   Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
1138   if (n_c->is_top()) return false;
1139   return !is_member(_phase->get_loop(n_c));
1140 }
1141 
1142 
1143 //------------------------------do_unroll--------------------------------------
1144 // Unroll the loop body one step - make each trip do 2 iterations.
1145 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
1146   assert(LoopUnrollLimit, "");
1147   CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
1148   CountedLoopEndNode *loop_end = loop_head->loopexit();
1149   assert(loop_end, "");
1150 #ifndef PRODUCT
1151   if (PrintOpto && VerifyLoopOptimizations) {
1152     tty->print("Unrolling ");
1153     loop->dump_head();
1154   } else if (TraceLoopOpts) {
1155     if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
1156       tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
1157     } else {
1158       tty->print("Unroll %d     ", loop_head->unrolled_count()*2);
1159     }
1160     loop->dump_head();
1161   }
1162 #endif
1163 
1164   // Remember loop node count before unrolling to detect
1165   // if rounds of unroll,optimize are making progress
1166   loop_head->set_node_count_before_unroll(loop->_body.size());
1167 
1168   Node *ctrl  = loop_head->in(LoopNode::EntryControl);
1169   Node *limit = loop_head->limit();
1170   Node *init  = loop_head->init_trip();
1171   Node *stride = loop_head->stride();
1172 
1173   Node *opaq = NULL;
1174   if (adjust_min_trip) {       // If not maximally unrolling, need adjustment
1175     // Search for zero-trip guard.
1176     assert( loop_head->is_main_loop(), "" );
1177     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
1178     Node *iff = ctrl->in(0);
1179     assert( iff->Opcode() == Op_If, "" );
1180     Node *bol = iff->in(1);
1181     assert( bol->Opcode() == Op_Bool, "" );
1182     Node *cmp = bol->in(1);
1183     assert( cmp->Opcode() == Op_CmpI, "" );
1184     opaq = cmp->in(2);
1185     // Occasionally it's possible for a zero-trip guard Opaque1 node to be
1186     // optimized away and then another round of loop opts attempted.
1187     // We can not optimize this particular loop in that case.
1188     if (opaq->Opcode() != Op_Opaque1)
1189       return; // Cannot find zero-trip guard!  Bail out!
1190     // Zero-trip test uses an 'opaque' node which is not shared.
1191     assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
1192   }
1193 
1194   C->set_major_progress();
1195 
1196   Node* new_limit = NULL;
1197   if (UnrollLimitCheck) {
1198     int stride_con = stride->get_int();
1199     int stride_p = (stride_con > 0) ? stride_con : -stride_con;
1200     uint old_trip_count = loop_head->trip_count();
1201     // Verify that unroll policy result is still valid.
1202     assert(old_trip_count > 1 &&
1203            (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity");
1204 
1205     // Adjust loop limit to keep valid iterations number after unroll.
1206     // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
1207     // which may overflow.
1208     if (!adjust_min_trip) {
1209       assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
1210              "odd trip count for maximally unroll");
1211       // Don't need to adjust limit for maximally unroll since trip count is even.
1212     } else if (loop_head->has_exact_trip_count() && init->is_Con()) {
1213       // Loop's limit is constant. Loop's init could be constant when pre-loop
1214       // become peeled iteration.
1215       jlong init_con = init->get_int();
1216       // We can keep old loop limit if iterations count stays the same:
1217       //   old_trip_count == new_trip_count * 2
1218       // Note: since old_trip_count >= 2 then new_trip_count >= 1
1219       // so we also don't need to adjust zero trip test.
1220       jlong limit_con  = limit->get_int();
1221       // (stride_con*2) not overflow since stride_con <= 8.
1222       int new_stride_con = stride_con * 2;
1223       int stride_m    = new_stride_con - (stride_con > 0 ? 1 : -1);
1224       jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con;
1225       // New trip count should satisfy next conditions.
1226       assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
1227       uint new_trip_count = (uint)trip_count;
1228       adjust_min_trip = (old_trip_count != new_trip_count*2);
1229     }
1230 
1231     if (adjust_min_trip) {
1232       // Step 2: Adjust the trip limit if it is called for.
1233       // The adjustment amount is -stride. Need to make sure if the
1234       // adjustment underflows or overflows, then the main loop is skipped.
1235       Node* cmp = loop_end->cmp_node();
1236       assert(cmp->in(2) == limit, "sanity");
1237       assert(opaq != NULL && opaq->in(1) == limit, "sanity");
1238 
1239       // Verify that policy_unroll result is still valid.
1240       const TypeInt* limit_type = _igvn.type(limit)->is_int();
1241       assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) ||
1242              stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity");
1243 
1244       if (limit->is_Con()) {
1245         // The check in policy_unroll and the assert above guarantee
1246         // no underflow if limit is constant.
1247         new_limit = _igvn.intcon(limit->get_int() - stride_con);
1248         set_ctrl(new_limit, C->root());
1249       } else {
1250         // Limit is not constant.
1251         if (loop_head->unrolled_count() == 1) { // only for first unroll
1252           // Separate limit by Opaque node in case it is an incremented
1253           // variable from previous loop to avoid using pre-incremented
1254           // value which could increase register pressure.
1255           // Otherwise reorg_offsets() optimization will create a separate
1256           // Opaque node for each use of trip-counter and as result
1257           // zero trip guard limit will be different from loop limit.
1258           assert(has_ctrl(opaq), "should have it");
1259           Node* opaq_ctrl = get_ctrl(opaq);
1260           limit = new (C) Opaque2Node( C, limit );
1261           register_new_node( limit, opaq_ctrl );
1262         }
1263         if (stride_con > 0 && ((limit_type->_lo - stride_con) < limit_type->_lo) ||
1264                    stride_con < 0 && ((limit_type->_hi - stride_con) > limit_type->_hi)) {
1265           // No underflow.
1266           new_limit = new (C) SubINode(limit, stride);
1267         } else {
1268           // (limit - stride) may underflow.
1269           // Clamp the adjustment value with MININT or MAXINT:
1270           //
1271           //   new_limit = limit-stride
1272           //   if (stride > 0)
1273           //     new_limit = (limit < new_limit) ? MININT : new_limit;
1274           //   else
1275           //     new_limit = (limit > new_limit) ? MAXINT : new_limit;
1276           //
1277           BoolTest::mask bt = loop_end->test_trip();
1278           assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
1279           Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint);
1280           set_ctrl(adj_max, C->root());
1281           Node* old_limit = NULL;
1282           Node* adj_limit = NULL;
1283           Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL;
1284           if (loop_head->unrolled_count() > 1 &&
1285               limit->is_CMove() && limit->Opcode() == Op_CMoveI &&
1286               limit->in(CMoveNode::IfTrue) == adj_max &&
1287               bol->as_Bool()->_test._test == bt &&
1288               bol->in(1)->Opcode() == Op_CmpI &&
1289               bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) {
1290             // Loop was unrolled before.
1291             // Optimize the limit to avoid nested CMove:
1292             // use original limit as old limit.
1293             old_limit = bol->in(1)->in(1);
1294             // Adjust previous adjusted limit.
1295             adj_limit = limit->in(CMoveNode::IfFalse);
1296             adj_limit = new (C) SubINode(adj_limit, stride);
1297           } else {
1298             old_limit = limit;
1299             adj_limit = new (C) SubINode(limit, stride);
1300           }
1301           assert(old_limit != NULL && adj_limit != NULL, "");
1302           register_new_node( adj_limit, ctrl ); // adjust amount
1303           Node* adj_cmp = new (C) CmpINode(old_limit, adj_limit);
1304           register_new_node( adj_cmp, ctrl );
1305           Node* adj_bool = new (C) BoolNode(adj_cmp, bt);
1306           register_new_node( adj_bool, ctrl );
1307           new_limit = new (C) CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT);
1308         }
1309         register_new_node(new_limit, ctrl);
1310       }
1311       assert(new_limit != NULL, "");
1312       // Replace in loop test.
1313       assert(loop_end->in(1)->in(1) == cmp, "sanity");
1314       if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
1315         // Don't need to create new test since only one user.
1316         _igvn.hash_delete(cmp);
1317         cmp->set_req(2, new_limit);
1318       } else {
1319         // Create new test since it is shared.
1320         Node* ctrl2 = loop_end->in(0);
1321         Node* cmp2  = cmp->clone();
1322         cmp2->set_req(2, new_limit);
1323         register_new_node(cmp2, ctrl2);
1324         Node* bol2 = loop_end->in(1)->clone();
1325         bol2->set_req(1, cmp2);
1326         register_new_node(bol2, ctrl2);
1327         _igvn.hash_delete(loop_end);
1328         loop_end->set_req(1, bol2);
1329       }
1330       // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1331       // Make it a 1-trip test (means at least 2 trips).
1332 
1333       // Guard test uses an 'opaque' node which is not shared.  Hence I
1334       // can edit it's inputs directly.  Hammer in the new limit for the
1335       // minimum-trip guard.
1336       assert(opaq->outcnt() == 1, "");
1337       _igvn.hash_delete(opaq);
1338       opaq->set_req(1, new_limit);
1339     }
1340 
1341     // Adjust max trip count. The trip count is intentionally rounded
1342     // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1343     // the main, unrolled, part of the loop will never execute as it is protected
1344     // by the min-trip test.  See bug 4834191 for a case where we over-unrolled
1345     // and later determined that part of the unrolled loop was dead.
1346     loop_head->set_trip_count(old_trip_count / 2);
1347 
1348     // Double the count of original iterations in the unrolled loop body.
1349     loop_head->double_unrolled_count();
1350 
1351   } else { // LoopLimitCheck
1352 
1353     // Adjust max trip count. The trip count is intentionally rounded
1354     // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1355     // the main, unrolled, part of the loop will never execute as it is protected
1356     // by the min-trip test.  See bug 4834191 for a case where we over-unrolled
1357     // and later determined that part of the unrolled loop was dead.
1358     loop_head->set_trip_count(loop_head->trip_count() / 2);
1359 
1360     // Double the count of original iterations in the unrolled loop body.
1361     loop_head->double_unrolled_count();
1362 
1363     // -----------
1364     // Step 2: Cut back the trip counter for an unroll amount of 2.
1365     // Loop will normally trip (limit - init)/stride_con.  Since it's a
1366     // CountedLoop this is exact (stride divides limit-init exactly).
1367     // We are going to double the loop body, so we want to knock off any
1368     // odd iteration: (trip_cnt & ~1).  Then back compute a new limit.
1369     Node *span = new (C) SubINode( limit, init );
1370     register_new_node( span, ctrl );
1371     Node *trip = new (C) DivINode( 0, span, stride );
1372     register_new_node( trip, ctrl );
1373     Node *mtwo = _igvn.intcon(-2);
1374     set_ctrl(mtwo, C->root());
1375     Node *rond = new (C) AndINode( trip, mtwo );
1376     register_new_node( rond, ctrl );
1377     Node *spn2 = new (C) MulINode( rond, stride );
1378     register_new_node( spn2, ctrl );
1379     new_limit = new (C) AddINode( spn2, init );
1380     register_new_node( new_limit, ctrl );
1381 
1382     // Hammer in the new limit
1383     Node *ctrl2 = loop_end->in(0);
1384     Node *cmp2 = new (C) CmpINode( loop_head->incr(), new_limit );
1385     register_new_node( cmp2, ctrl2 );
1386     Node *bol2 = new (C) BoolNode( cmp2, loop_end->test_trip() );
1387     register_new_node( bol2, ctrl2 );
1388     _igvn.hash_delete(loop_end);
1389     loop_end->set_req(CountedLoopEndNode::TestValue, bol2);
1390 
1391     // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1392     // Make it a 1-trip test (means at least 2 trips).
1393     if( adjust_min_trip ) {
1394       assert( new_limit != NULL, "" );
1395       // Guard test uses an 'opaque' node which is not shared.  Hence I
1396       // can edit it's inputs directly.  Hammer in the new limit for the
1397       // minimum-trip guard.
1398       assert( opaq->outcnt() == 1, "" );
1399       _igvn.hash_delete(opaq);
1400       opaq->set_req(1, new_limit);
1401     }
1402   } // LoopLimitCheck
1403 
1404   // ---------
1405   // Step 4: Clone the loop body.  Move it inside the loop.  This loop body
1406   // represents the odd iterations; since the loop trips an even number of
1407   // times its backedge is never taken.  Kill the backedge.
1408   uint dd = dom_depth(loop_head);
1409   clone_loop( loop, old_new, dd );
1410 
1411   // Make backedges of the clone equal to backedges of the original.
1412   // Make the fall-in from the original come from the fall-out of the clone.
1413   for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1414     Node* phi = loop_head->fast_out(j);
1415     if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1416       Node *newphi = old_new[phi->_idx];
1417       _igvn.hash_delete( phi );
1418       _igvn.hash_delete( newphi );
1419 
1420       phi   ->set_req(LoopNode::   EntryControl, newphi->in(LoopNode::LoopBackControl));
1421       newphi->set_req(LoopNode::LoopBackControl, phi   ->in(LoopNode::LoopBackControl));
1422       phi   ->set_req(LoopNode::LoopBackControl, C->top());
1423     }
1424   }
1425   Node *clone_head = old_new[loop_head->_idx];
1426   _igvn.hash_delete( clone_head );
1427   loop_head ->set_req(LoopNode::   EntryControl, clone_head->in(LoopNode::LoopBackControl));
1428   clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1429   loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1430   loop->_head = clone_head;     // New loop header
1431 
1432   set_idom(loop_head,  loop_head ->in(LoopNode::EntryControl), dd);
1433   set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1434 
1435   // Kill the clone's backedge
1436   Node *newcle = old_new[loop_end->_idx];
1437   _igvn.hash_delete( newcle );
1438   Node *one = _igvn.intcon(1);
1439   set_ctrl(one, C->root());
1440   newcle->set_req(1, one);
1441   // Force clone into same loop body
1442   uint max = loop->_body.size();
1443   for( uint k = 0; k < max; k++ ) {
1444     Node *old = loop->_body.at(k);
1445     Node *nnn = old_new[old->_idx];
1446     loop->_body.push(nnn);
1447     if (!has_ctrl(old))
1448       set_loop(nnn, loop);
1449   }
1450 
1451   loop->record_for_igvn();
1452 }
1453 
1454 //------------------------------do_maximally_unroll----------------------------
1455 
1456 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1457   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1458   assert(cl->has_exact_trip_count(), "trip count is not exact");
1459   assert(cl->trip_count() > 0, "");
1460 #ifndef PRODUCT
1461   if (TraceLoopOpts) {
1462     tty->print("MaxUnroll  %d ", cl->trip_count());
1463     loop->dump_head();
1464   }
1465 #endif
1466 
1467   // If loop is tripping an odd number of times, peel odd iteration
1468   if ((cl->trip_count() & 1) == 1) {
1469     do_peeling(loop, old_new);
1470   }
1471 
1472   // Now its tripping an even number of times remaining.  Double loop body.
1473   // Do not adjust pre-guards; they are not needed and do not exist.
1474   if (cl->trip_count() > 0) {
1475     assert((cl->trip_count() & 1) == 0, "missed peeling");
1476     do_unroll(loop, old_new, false);
1477   }
1478 }
1479 
1480 //------------------------------dominates_backedge---------------------------------
1481 // Returns true if ctrl is executed on every complete iteration
1482 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1483   assert(ctrl->is_CFG(), "must be control");
1484   Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1485   return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1486 }
1487 
1488 //------------------------------adjust_limit-----------------------------------
1489 // Helper function for add_constraint().
1490 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) {
1491   // Compute "I :: (limit-offset)/scale"
1492   Node *con = new (C) SubINode(rc_limit, offset);
1493   register_new_node(con, pre_ctrl);
1494   Node *X = new (C) DivINode(0, con, scale);
1495   register_new_node(X, pre_ctrl);
1496 
1497   // Adjust loop limit
1498   loop_limit = (stride_con > 0)
1499                ? (Node*)(new (C) MinINode(loop_limit, X))
1500                : (Node*)(new (C) MaxINode(loop_limit, X));
1501   register_new_node(loop_limit, pre_ctrl);
1502   return loop_limit;
1503 }
1504 
1505 //------------------------------add_constraint---------------------------------
1506 // Constrain the main loop iterations so the conditions:
1507 //    low_limit <= scale_con * I + offset  <  upper_limit
1508 // always holds true.  That is, either increase the number of iterations in
1509 // the pre-loop or the post-loop until the condition holds true in the main
1510 // loop.  Stride, scale, offset and limit are all loop invariant.  Further,
1511 // stride and scale are constants (offset and limit often are).
1512 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 ) {
1513   // For positive stride, the pre-loop limit always uses a MAX function
1514   // and the main loop a MIN function.  For negative stride these are
1515   // reversed.
1516 
1517   // Also for positive stride*scale the affine function is increasing, so the
1518   // pre-loop must check for underflow and the post-loop for overflow.
1519   // Negative stride*scale reverses this; pre-loop checks for overflow and
1520   // post-loop for underflow.
1521 
1522   Node *scale = _igvn.intcon(scale_con);
1523   set_ctrl(scale, C->root());
1524 
1525   if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
1526     // The overflow limit: scale*I+offset < upper_limit
1527     // For main-loop compute
1528     //   ( if (scale > 0) /* and stride > 0 */
1529     //       I < (upper_limit-offset)/scale
1530     //     else /* scale < 0 and stride < 0 */
1531     //       I > (upper_limit-offset)/scale
1532     //   )
1533     //
1534     // (upper_limit-offset) may overflow or underflow.
1535     // But it is fine since main loop will either have
1536     // less iterations or will be skipped in such case.
1537     *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl);
1538 
1539     // The underflow limit: low_limit <= scale*I+offset.
1540     // For pre-loop compute
1541     //   NOT(scale*I+offset >= low_limit)
1542     //   scale*I+offset < low_limit
1543     //   ( if (scale > 0) /* and stride > 0 */
1544     //       I < (low_limit-offset)/scale
1545     //     else /* scale < 0 and stride < 0 */
1546     //       I > (low_limit-offset)/scale
1547     //   )
1548 
1549     if (low_limit->get_int() == -max_jint) {
1550       if (!RangeLimitCheck) return;
1551       // We need this guard when scale*pre_limit+offset >= limit
1552       // due to underflow. So we need execute pre-loop until
1553       // scale*I+offset >= min_int. But (min_int-offset) will
1554       // underflow when offset > 0 and X will be > original_limit
1555       // when stride > 0. To avoid it we replace positive offset with 0.
1556       //
1557       // Also (min_int+1 == -max_int) is used instead of min_int here
1558       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1559       Node* shift = _igvn.intcon(31);
1560       set_ctrl(shift, C->root());
1561       Node* sign = new (C) RShiftINode(offset, shift);
1562       register_new_node(sign, pre_ctrl);
1563       offset = new (C) AndINode(offset, sign);
1564       register_new_node(offset, pre_ctrl);
1565     } else {
1566       assert(low_limit->get_int() == 0, "wrong low limit for range check");
1567       // The only problem we have here when offset == min_int
1568       // since (0-min_int) == min_int. It may be fine for stride > 0
1569       // but for stride < 0 X will be < original_limit. To avoid it
1570       // max(pre_limit, original_limit) is used in do_range_check().
1571     }
1572     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1573     *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl);
1574 
1575   } else { // stride_con*scale_con < 0
1576     // For negative stride*scale pre-loop checks for overflow and
1577     // post-loop for underflow.
1578     //
1579     // The overflow limit: scale*I+offset < upper_limit
1580     // For pre-loop compute
1581     //   NOT(scale*I+offset < upper_limit)
1582     //   scale*I+offset >= upper_limit
1583     //   scale*I+offset+1 > upper_limit
1584     //   ( if (scale < 0) /* and stride > 0 */
1585     //       I < (upper_limit-(offset+1))/scale
1586     //     else /* scale > 0 and stride < 0 */
1587     //       I > (upper_limit-(offset+1))/scale
1588     //   )
1589     //
1590     // (upper_limit-offset-1) may underflow or overflow.
1591     // To avoid it min(pre_limit, original_limit) is used
1592     // in do_range_check() for stride > 0 and max() for < 0.
1593     Node *one  = _igvn.intcon(1);
1594     set_ctrl(one, C->root());
1595 
1596     Node *plus_one = new (C) AddINode(offset, one);
1597     register_new_node( plus_one, pre_ctrl );
1598     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1599     *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl);
1600 
1601     if (low_limit->get_int() == -max_jint) {
1602       if (!RangeLimitCheck) return;
1603       // We need this guard when scale*main_limit+offset >= limit
1604       // due to underflow. So we need execute main-loop while
1605       // scale*I+offset+1 > min_int. But (min_int-offset-1) will
1606       // underflow when (offset+1) > 0 and X will be < main_limit
1607       // when scale < 0 (and stride > 0). To avoid it we replace
1608       // positive (offset+1) with 0.
1609       //
1610       // Also (min_int+1 == -max_int) is used instead of min_int here
1611       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1612       Node* shift = _igvn.intcon(31);
1613       set_ctrl(shift, C->root());
1614       Node* sign = new (C) RShiftINode(plus_one, shift);
1615       register_new_node(sign, pre_ctrl);
1616       plus_one = new (C) AndINode(plus_one, sign);
1617       register_new_node(plus_one, pre_ctrl);
1618     } else {
1619       assert(low_limit->get_int() == 0, "wrong low limit for range check");
1620       // The only problem we have here when offset == max_int
1621       // since (max_int+1) == min_int and (0-min_int) == min_int.
1622       // But it is fine since main loop will either have
1623       // less iterations or will be skipped in such case.
1624     }
1625     // The underflow limit: low_limit <= scale*I+offset.
1626     // For main-loop compute
1627     //   scale*I+offset+1 > low_limit
1628     //   ( if (scale < 0) /* and stride > 0 */
1629     //       I < (low_limit-(offset+1))/scale
1630     //     else /* scale > 0 and stride < 0 */
1631     //       I > (low_limit-(offset+1))/scale
1632     //   )
1633 
1634     *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl);
1635   }
1636 }
1637 
1638 
1639 //------------------------------is_scaled_iv---------------------------------
1640 // Return true if exp is a constant times an induction var
1641 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1642   if (exp == iv) {
1643     if (p_scale != NULL) {
1644       *p_scale = 1;
1645     }
1646     return true;
1647   }
1648   int opc = exp->Opcode();
1649   if (opc == Op_MulI) {
1650     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1651       if (p_scale != NULL) {
1652         *p_scale = exp->in(2)->get_int();
1653       }
1654       return true;
1655     }
1656     if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1657       if (p_scale != NULL) {
1658         *p_scale = exp->in(1)->get_int();
1659       }
1660       return true;
1661     }
1662   } else if (opc == Op_LShiftI) {
1663     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1664       if (p_scale != NULL) {
1665         *p_scale = 1 << exp->in(2)->get_int();
1666       }
1667       return true;
1668     }
1669   }
1670   return false;
1671 }
1672 
1673 //-----------------------------is_scaled_iv_plus_offset------------------------------
1674 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1675 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1676   if (is_scaled_iv(exp, iv, p_scale)) {
1677     if (p_offset != NULL) {
1678       Node *zero = _igvn.intcon(0);
1679       set_ctrl(zero, C->root());
1680       *p_offset = zero;
1681     }
1682     return true;
1683   }
1684   int opc = exp->Opcode();
1685   if (opc == Op_AddI) {
1686     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1687       if (p_offset != NULL) {
1688         *p_offset = exp->in(2);
1689       }
1690       return true;
1691     }
1692     if (exp->in(2)->is_Con()) {
1693       Node* offset2 = NULL;
1694       if (depth < 2 &&
1695           is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
1696                                    p_offset != NULL ? &offset2 : NULL, depth+1)) {
1697         if (p_offset != NULL) {
1698           Node *ctrl_off2 = get_ctrl(offset2);
1699           Node* offset = new (C) AddINode(offset2, exp->in(2));
1700           register_new_node(offset, ctrl_off2);
1701           *p_offset = offset;
1702         }
1703         return true;
1704       }
1705     }
1706   } else if (opc == Op_SubI) {
1707     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1708       if (p_offset != NULL) {
1709         Node *zero = _igvn.intcon(0);
1710         set_ctrl(zero, C->root());
1711         Node *ctrl_off = get_ctrl(exp->in(2));
1712         Node* offset = new (C) SubINode(zero, exp->in(2));
1713         register_new_node(offset, ctrl_off);
1714         *p_offset = offset;
1715       }
1716       return true;
1717     }
1718     if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1719       if (p_offset != NULL) {
1720         *p_scale *= -1;
1721         *p_offset = exp->in(1);
1722       }
1723       return true;
1724     }
1725   }
1726   return false;
1727 }
1728 
1729 //------------------------------do_range_check---------------------------------
1730 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1731 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
1732 #ifndef PRODUCT
1733   if (PrintOpto && VerifyLoopOptimizations) {
1734     tty->print("Range Check Elimination ");
1735     loop->dump_head();
1736   } else if (TraceLoopOpts) {
1737     tty->print("RangeCheck   ");
1738     loop->dump_head();
1739   }
1740 #endif
1741   assert(RangeCheckElimination, "");
1742   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1743   assert(cl->is_main_loop(), "");
1744 
1745   // protect against stride not being a constant
1746   if (!cl->stride_is_con())
1747     return;
1748 
1749   // Find the trip counter; we are iteration splitting based on it
1750   Node *trip_counter = cl->phi();
1751   // Find the main loop limit; we will trim it's iterations
1752   // to not ever trip end tests
1753   Node *main_limit = cl->limit();
1754 
1755   // Need to find the main-loop zero-trip guard
1756   Node *ctrl  = cl->in(LoopNode::EntryControl);
1757   assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
1758   Node *iffm = ctrl->in(0);
1759   assert(iffm->Opcode() == Op_If, "");
1760   Node *bolzm = iffm->in(1);
1761   assert(bolzm->Opcode() == Op_Bool, "");
1762   Node *cmpzm = bolzm->in(1);
1763   assert(cmpzm->is_Cmp(), "");
1764   Node *opqzm = cmpzm->in(2);
1765   // Can not optimize a loop if zero-trip Opaque1 node is optimized
1766   // away and then another round of loop opts attempted.
1767   if (opqzm->Opcode() != Op_Opaque1)
1768     return;
1769   assert(opqzm->in(1) == main_limit, "do not understand situation");
1770 
1771   // Find the pre-loop limit; we will expand it's iterations to
1772   // not ever trip low tests.
1773   Node *p_f = iffm->in(0);
1774   assert(p_f->Opcode() == Op_IfFalse, "");
1775   CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
1776   assert(pre_end->loopnode()->is_pre_loop(), "");
1777   Node *pre_opaq1 = pre_end->limit();
1778   // Occasionally it's possible for a pre-loop Opaque1 node to be
1779   // optimized away and then another round of loop opts attempted.
1780   // We can not optimize this particular loop in that case.
1781   if (pre_opaq1->Opcode() != Op_Opaque1)
1782     return;
1783   Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
1784   Node *pre_limit = pre_opaq->in(1);
1785 
1786   // Where do we put new limit calculations
1787   Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
1788 
1789   // Ensure the original loop limit is available from the
1790   // pre-loop Opaque1 node.
1791   Node *orig_limit = pre_opaq->original_loop_limit();
1792   if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
1793     return;
1794 
1795   // Must know if its a count-up or count-down loop
1796 
1797   int stride_con = cl->stride_con();
1798   Node *zero = _igvn.intcon(0);
1799   Node *one  = _igvn.intcon(1);
1800   // Use symmetrical int range [-max_jint,max_jint]
1801   Node *mini = _igvn.intcon(-max_jint);
1802   set_ctrl(zero, C->root());
1803   set_ctrl(one,  C->root());
1804   set_ctrl(mini, C->root());
1805 
1806   // Range checks that do not dominate the loop backedge (ie.
1807   // conditionally executed) can lengthen the pre loop limit beyond
1808   // the original loop limit. To prevent this, the pre limit is
1809   // (for stride > 0) MINed with the original loop limit (MAXed
1810   // stride < 0) when some range_check (rc) is conditionally
1811   // executed.
1812   bool conditional_rc = false;
1813 
1814   // Check loop body for tests of trip-counter plus loop-invariant vs
1815   // loop-invariant.
1816   for( uint i = 0; i < loop->_body.size(); i++ ) {
1817     Node *iff = loop->_body[i];
1818     if( iff->Opcode() == Op_If ) { // Test?
1819 
1820       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
1821       // we need loop unswitching instead of iteration splitting.
1822       Node *exit = loop->is_loop_exit(iff);
1823       if( !exit ) continue;
1824       int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
1825 
1826       // Get boolean condition to test
1827       Node *i1 = iff->in(1);
1828       if( !i1->is_Bool() ) continue;
1829       BoolNode *bol = i1->as_Bool();
1830       BoolTest b_test = bol->_test;
1831       // Flip sense of test if exit condition is flipped
1832       if( flip )
1833         b_test = b_test.negate();
1834 
1835       // Get compare
1836       Node *cmp = bol->in(1);
1837 
1838       // Look for trip_counter + offset vs limit
1839       Node *rc_exp = cmp->in(1);
1840       Node *limit  = cmp->in(2);
1841       jint scale_con= 1;        // Assume trip counter not scaled
1842 
1843       Node *limit_c = get_ctrl(limit);
1844       if( loop->is_member(get_loop(limit_c) ) ) {
1845         // Compare might have operands swapped; commute them
1846         b_test = b_test.commute();
1847         rc_exp = cmp->in(2);
1848         limit  = cmp->in(1);
1849         limit_c = get_ctrl(limit);
1850         if( loop->is_member(get_loop(limit_c) ) )
1851           continue;             // Both inputs are loop varying; cannot RCE
1852       }
1853       // Here we know 'limit' is loop invariant
1854 
1855       // 'limit' maybe pinned below the zero trip test (probably from a
1856       // previous round of rce), in which case, it can't be used in the
1857       // zero trip test expression which must occur before the zero test's if.
1858       if( limit_c == ctrl ) {
1859         continue;  // Don't rce this check but continue looking for other candidates.
1860       }
1861 
1862       // Check for scaled induction variable plus an offset
1863       Node *offset = NULL;
1864 
1865       if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
1866         continue;
1867       }
1868 
1869       Node *offset_c = get_ctrl(offset);
1870       if( loop->is_member( get_loop(offset_c) ) )
1871         continue;               // Offset is not really loop invariant
1872       // Here we know 'offset' is loop invariant.
1873 
1874       // As above for the 'limit', the 'offset' maybe pinned below the
1875       // zero trip test.
1876       if( offset_c == ctrl ) {
1877         continue; // Don't rce this check but continue looking for other candidates.
1878       }
1879 #ifdef ASSERT
1880       if (TraceRangeLimitCheck) {
1881         tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
1882         bol->dump(2);
1883       }
1884 #endif
1885       // At this point we have the expression as:
1886       //   scale_con * trip_counter + offset :: limit
1887       // where scale_con, offset and limit are loop invariant.  Trip_counter
1888       // monotonically increases by stride_con, a constant.  Both (or either)
1889       // stride_con and scale_con can be negative which will flip about the
1890       // sense of the test.
1891 
1892       // Adjust pre and main loop limits to guard the correct iteration set
1893       if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
1894         if( b_test._test == BoolTest::lt ) { // Range checks always use lt
1895           // The underflow and overflow limits: 0 <= scale*I+offset < limit
1896           add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit );
1897           if (!conditional_rc) {
1898             // (0-offset)/scale could be outside of loop iterations range.
1899             conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1900           }
1901         } else {
1902 #ifndef PRODUCT
1903           if( PrintOpto )
1904             tty->print_cr("missed RCE opportunity");
1905 #endif
1906           continue;             // In release mode, ignore it
1907         }
1908       } else {                  // Otherwise work on normal compares
1909         switch( b_test._test ) {
1910         case BoolTest::gt:
1911           // Fall into GE case
1912         case BoolTest::ge:
1913           // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
1914           scale_con = -scale_con;
1915           offset = new (C) SubINode( zero, offset );
1916           register_new_node( offset, pre_ctrl );
1917           limit  = new (C) SubINode( zero, limit  );
1918           register_new_node( limit, pre_ctrl );
1919           // Fall into LE case
1920         case BoolTest::le:
1921           if (b_test._test != BoolTest::gt) {
1922             // Convert X <= Y to X < Y+1
1923             limit = new (C) AddINode( limit, one );
1924             register_new_node( limit, pre_ctrl );
1925           }
1926           // Fall into LT case
1927         case BoolTest::lt:
1928           // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
1929           // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
1930           // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
1931           add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit );
1932           if (!conditional_rc) {
1933             // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range.
1934             // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could
1935             // still be outside of loop range.
1936             conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1937           }
1938           break;
1939         default:
1940 #ifndef PRODUCT
1941           if( PrintOpto )
1942             tty->print_cr("missed RCE opportunity");
1943 #endif
1944           continue;             // Unhandled case
1945         }
1946       }
1947 
1948       // Kill the eliminated test
1949       C->set_major_progress();
1950       Node *kill_con = _igvn.intcon( 1-flip );
1951       set_ctrl(kill_con, C->root());
1952       _igvn.replace_input_of(iff, 1, kill_con);
1953       // Find surviving projection
1954       assert(iff->is_If(), "");
1955       ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
1956       // Find loads off the surviving projection; remove their control edge
1957       for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
1958         Node* cd = dp->fast_out(i); // Control-dependent node
1959         if (cd->is_Load() && cd->depends_only_on_test()) {   // Loads can now float around in the loop
1960           // Allow the load to float around in the loop, or before it
1961           // but NOT before the pre-loop.
1962           _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL
1963           --i;
1964           --imax;
1965         }
1966       }
1967 
1968     } // End of is IF
1969 
1970   }
1971 
1972   // Update loop limits
1973   if (conditional_rc) {
1974     pre_limit = (stride_con > 0) ? (Node*)new (C) MinINode(pre_limit, orig_limit)
1975                                  : (Node*)new (C) MaxINode(pre_limit, orig_limit);
1976     register_new_node(pre_limit, pre_ctrl);
1977   }
1978   _igvn.hash_delete(pre_opaq);
1979   pre_opaq->set_req(1, pre_limit);
1980 
1981   // Note:: we are making the main loop limit no longer precise;
1982   // need to round up based on stride.
1983   cl->set_nonexact_trip_count();
1984   if (!LoopLimitCheck && stride_con != 1 && stride_con != -1) { // Cutout for common case
1985     // "Standard" round-up logic:  ([main_limit-init+(y-1)]/y)*y+init
1986     // Hopefully, compiler will optimize for powers of 2.
1987     Node *ctrl = get_ctrl(main_limit);
1988     Node *stride = cl->stride();
1989     Node *init = cl->init_trip();
1990     Node *span = new (C) SubINode(main_limit,init);
1991     register_new_node(span,ctrl);
1992     Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
1993     Node *add = new (C) AddINode(span,rndup);
1994     register_new_node(add,ctrl);
1995     Node *div = new (C) DivINode(0,add,stride);
1996     register_new_node(div,ctrl);
1997     Node *mul = new (C) MulINode(div,stride);
1998     register_new_node(mul,ctrl);
1999     Node *newlim = new (C) AddINode(mul,init);
2000     register_new_node(newlim,ctrl);
2001     main_limit = newlim;
2002   }
2003 
2004   Node *main_cle = cl->loopexit();
2005   Node *main_bol = main_cle->in(1);
2006   // Hacking loop bounds; need private copies of exit test
2007   if( main_bol->outcnt() > 1 ) {// BoolNode shared?
2008     _igvn.hash_delete(main_cle);
2009     main_bol = main_bol->clone();// Clone a private BoolNode
2010     register_new_node( main_bol, main_cle->in(0) );
2011     main_cle->set_req(1,main_bol);
2012   }
2013   Node *main_cmp = main_bol->in(1);
2014   if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
2015     _igvn.hash_delete(main_bol);
2016     main_cmp = main_cmp->clone();// Clone a private CmpNode
2017     register_new_node( main_cmp, main_cle->in(0) );
2018     main_bol->set_req(1,main_cmp);
2019   }
2020   // Hack the now-private loop bounds
2021   _igvn.replace_input_of(main_cmp, 2, main_limit);
2022   // The OpaqueNode is unshared by design
2023   assert( opqzm->outcnt() == 1, "cannot hack shared node" );
2024   _igvn.replace_input_of(opqzm, 1, main_limit);
2025 }
2026 
2027 //------------------------------DCE_loop_body----------------------------------
2028 // Remove simplistic dead code from loop body
2029 void IdealLoopTree::DCE_loop_body() {
2030   for( uint i = 0; i < _body.size(); i++ )
2031     if( _body.at(i)->outcnt() == 0 )
2032       _body.map( i--, _body.pop() );
2033 }
2034 
2035 
2036 //------------------------------adjust_loop_exit_prob--------------------------
2037 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
2038 // Replace with a 1-in-10 exit guess.
2039 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
2040   Node *test = tail();
2041   while( test != _head ) {
2042     uint top = test->Opcode();
2043     if( top == Op_IfTrue || top == Op_IfFalse ) {
2044       int test_con = ((ProjNode*)test)->_con;
2045       assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
2046       IfNode *iff = test->in(0)->as_If();
2047       if( iff->outcnt() == 2 ) {        // Ignore dead tests
2048         Node *bol = iff->in(1);
2049         if( bol && bol->req() > 1 && bol->in(1) &&
2050             ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
2051              (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
2052              (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
2053              (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
2054              (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
2055              (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
2056              (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
2057           return;               // Allocation loops RARELY take backedge
2058         // Find the OTHER exit path from the IF
2059         Node* ex = iff->proj_out(1-test_con);
2060         float p = iff->_prob;
2061         if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
2062           if( top == Op_IfTrue ) {
2063             if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
2064               iff->_prob = PROB_STATIC_FREQUENT;
2065             }
2066           } else {
2067             if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
2068               iff->_prob = PROB_STATIC_INFREQUENT;
2069             }
2070           }
2071         }
2072       }
2073     }
2074     test = phase->idom(test);
2075   }
2076 }
2077 
2078 
2079 //------------------------------policy_do_remove_empty_loop--------------------
2080 // Micro-benchmark spamming.  Policy is to always remove empty loops.
2081 // The 'DO' part is to replace the trip counter with the value it will
2082 // have on the last iteration.  This will break the loop.
2083 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
2084   // Minimum size must be empty loop
2085   if (_body.size() > EMPTY_LOOP_SIZE)
2086     return false;
2087 
2088   if (!_head->is_CountedLoop())
2089     return false;     // Dead loop
2090   CountedLoopNode *cl = _head->as_CountedLoop();
2091   if (!cl->is_valid_counted_loop())
2092     return false; // Malformed loop
2093   if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
2094     return false;             // Infinite loop
2095 
2096 #ifdef ASSERT
2097   // Ensure only one phi which is the iv.
2098   Node* iv = NULL;
2099   for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
2100     Node* n = cl->fast_out(i);
2101     if (n->Opcode() == Op_Phi) {
2102       assert(iv == NULL, "Too many phis" );
2103       iv = n;
2104     }
2105   }
2106   assert(iv == cl->phi(), "Wrong phi" );
2107 #endif
2108 
2109   // main and post loops have explicitly created zero trip guard
2110   bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
2111   if (needs_guard) {
2112     // Skip guard if values not overlap.
2113     const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
2114     const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
2115     int  stride_con = cl->stride_con();
2116     if (stride_con > 0) {
2117       needs_guard = (init_t->_hi >= limit_t->_lo);
2118     } else {
2119       needs_guard = (init_t->_lo <= limit_t->_hi);
2120     }
2121   }
2122   if (needs_guard) {
2123     // Check for an obvious zero trip guard.
2124     Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl));
2125     if (inctrl->Opcode() == Op_IfTrue) {
2126       // The test should look like just the backedge of a CountedLoop
2127       Node* iff = inctrl->in(0);
2128       if (iff->is_If()) {
2129         Node* bol = iff->in(1);
2130         if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) {
2131           Node* cmp = bol->in(1);
2132           if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) {
2133             needs_guard = false;
2134           }
2135         }
2136       }
2137     }
2138   }
2139 
2140 #ifndef PRODUCT
2141   if (PrintOpto) {
2142     tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
2143     this->dump_head();
2144   } else if (TraceLoopOpts) {
2145     tty->print("Empty with%s zero trip guard   ", needs_guard ? "out" : "");
2146     this->dump_head();
2147   }
2148 #endif
2149 
2150   if (needs_guard) {
2151     // Peel the loop to ensure there's a zero trip guard
2152     Node_List old_new;
2153     phase->do_peeling(this, old_new);
2154   }
2155 
2156   // Replace the phi at loop head with the final value of the last
2157   // iteration.  Then the CountedLoopEnd will collapse (backedge never
2158   // taken) and all loop-invariant uses of the exit values will be correct.
2159   Node *phi = cl->phi();
2160   Node *exact_limit = phase->exact_limit(this);
2161   if (exact_limit != cl->limit()) {
2162     // We also need to replace the original limit to collapse loop exit.
2163     Node* cmp = cl->loopexit()->cmp_node();
2164     assert(cl->limit() == cmp->in(2), "sanity");
2165     phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
2166     phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist
2167   }
2168   // Note: the final value after increment should not overflow since
2169   // counted loop has limit check predicate.
2170   Node *final = new (phase->C) SubINode( exact_limit, cl->stride() );
2171   phase->register_new_node(final,cl->in(LoopNode::EntryControl));
2172   phase->_igvn.replace_node(phi,final);
2173   phase->C->set_major_progress();
2174   return true;
2175 }
2176 
2177 //------------------------------policy_do_one_iteration_loop-------------------
2178 // Convert one iteration loop into normal code.
2179 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) {
2180   if (!_head->as_Loop()->is_valid_counted_loop())
2181     return false; // Only for counted loop
2182 
2183   CountedLoopNode *cl = _head->as_CountedLoop();
2184   if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
2185     return false;
2186   }
2187 
2188 #ifndef PRODUCT
2189   if(TraceLoopOpts) {
2190     tty->print("OneIteration ");
2191     this->dump_head();
2192   }
2193 #endif
2194 
2195   Node *init_n = cl->init_trip();
2196 #ifdef ASSERT
2197   // Loop boundaries should be constant since trip count is exact.
2198   assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration");
2199 #endif
2200   // Replace the phi at loop head with the value of the init_trip.
2201   // Then the CountedLoopEnd will collapse (backedge will not be taken)
2202   // and all loop-invariant uses of the exit values will be correct.
2203   phase->_igvn.replace_node(cl->phi(), cl->init_trip());
2204   phase->C->set_major_progress();
2205   return true;
2206 }
2207 
2208 //=============================================================================
2209 //------------------------------iteration_split_impl---------------------------
2210 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
2211   // Compute exact loop trip count if possible.
2212   compute_exact_trip_count(phase);
2213 
2214   // Convert one iteration loop into normal code.
2215   if (policy_do_one_iteration_loop(phase))
2216     return true;
2217 
2218   // Check and remove empty loops (spam micro-benchmarks)
2219   if (policy_do_remove_empty_loop(phase))
2220     return true;  // Here we removed an empty loop
2221 
2222   bool should_peel = policy_peeling(phase); // Should we peel?
2223 
2224   bool should_unswitch = policy_unswitching(phase);
2225 
2226   // Non-counted loops may be peeled; exactly 1 iteration is peeled.
2227   // This removes loop-invariant tests (usually null checks).
2228   if (!_head->is_CountedLoop()) { // Non-counted loop
2229     if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
2230       // Partial peel succeeded so terminate this round of loop opts
2231       return false;
2232     }
2233     if (should_peel) {            // Should we peel?
2234 #ifndef PRODUCT
2235       if (PrintOpto) tty->print_cr("should_peel");
2236 #endif
2237       phase->do_peeling(this,old_new);
2238     } else if (should_unswitch) {
2239       phase->do_unswitching(this, old_new);
2240     }
2241     return true;
2242   }
2243   CountedLoopNode *cl = _head->as_CountedLoop();
2244 
2245   if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops
2246 
2247   // Do nothing special to pre- and post- loops
2248   if (cl->is_pre_loop() || cl->is_post_loop()) return true;
2249 
2250   // Compute loop trip count from profile data
2251   compute_profile_trip_cnt(phase);
2252 
2253   // Before attempting fancy unrolling, RCE or alignment, see if we want
2254   // to completely unroll this loop or do loop unswitching.
2255   if (cl->is_normal_loop()) {
2256     if (should_unswitch) {
2257       phase->do_unswitching(this, old_new);
2258       return true;
2259     }
2260     bool should_maximally_unroll =  policy_maximally_unroll(phase);
2261     if (should_maximally_unroll) {
2262       // Here we did some unrolling and peeling.  Eventually we will
2263       // completely unroll this loop and it will no longer be a loop.
2264       phase->do_maximally_unroll(this,old_new);
2265       return true;
2266     }
2267   }
2268 
2269   // Skip next optimizations if running low on nodes. Note that
2270   // policy_unswitching and policy_maximally_unroll have this check.
2271   uint nodes_left = MaxNodeLimit - (uint) phase->C->live_nodes();
2272   if ((2 * _body.size()) > nodes_left) {
2273     return true;
2274   }
2275 
2276   // Counted loops may be peeled, may need some iterations run up
2277   // front for RCE, and may want to align loop refs to a cache
2278   // line.  Thus we clone a full loop up front whose trip count is
2279   // at least 1 (if peeling), but may be several more.
2280 
2281   // The main loop will start cache-line aligned with at least 1
2282   // iteration of the unrolled body (zero-trip test required) and
2283   // will have some range checks removed.
2284 
2285   // A post-loop will finish any odd iterations (leftover after
2286   // unrolling), plus any needed for RCE purposes.
2287 
2288   bool should_unroll = policy_unroll(phase);
2289 
2290   bool should_rce = policy_range_check(phase);
2291 
2292   bool should_align = policy_align(phase);
2293 
2294   // If not RCE'ing (iteration splitting) or Aligning, then we do not
2295   // need a pre-loop.  We may still need to peel an initial iteration but
2296   // we will not be needing an unknown number of pre-iterations.
2297   //
2298   // Basically, if may_rce_align reports FALSE first time through,
2299   // we will not be able to later do RCE or Aligning on this loop.
2300   bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
2301 
2302   // If we have any of these conditions (RCE, alignment, unrolling) met, then
2303   // we switch to the pre-/main-/post-loop model.  This model also covers
2304   // peeling.
2305   if (should_rce || should_align || should_unroll) {
2306     if (cl->is_normal_loop())  // Convert to 'pre/main/post' loops
2307       phase->insert_pre_post_loops(this,old_new, !may_rce_align);
2308 
2309     // Adjust the pre- and main-loop limits to let the pre and post loops run
2310     // with full checks, but the main-loop with no checks.  Remove said
2311     // checks from the main body.
2312     if (should_rce)
2313       phase->do_range_check(this,old_new);
2314 
2315     // Double loop body for unrolling.  Adjust the minimum-trip test (will do
2316     // twice as many iterations as before) and the main body limit (only do
2317     // an even number of trips).  If we are peeling, we might enable some RCE
2318     // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
2319     // peeling.
2320     if (should_unroll && !should_peel)
2321       phase->do_unroll(this,old_new, true);
2322 
2323     // Adjust the pre-loop limits to align the main body
2324     // iterations.
2325     if (should_align)
2326       Unimplemented();
2327 
2328   } else {                      // Else we have an unchanged counted loop
2329     if (should_peel)           // Might want to peel but do nothing else
2330       phase->do_peeling(this,old_new);
2331   }
2332   return true;
2333 }
2334 
2335 
2336 //=============================================================================
2337 //------------------------------iteration_split--------------------------------
2338 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
2339   // Recursively iteration split nested loops
2340   if (_child && !_child->iteration_split(phase, old_new))
2341     return false;
2342 
2343   // Clean out prior deadwood
2344   DCE_loop_body();
2345 
2346 
2347   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
2348   // Replace with a 1-in-10 exit guess.
2349   if (_parent /*not the root loop*/ &&
2350       !_irreducible &&
2351       // Also ignore the occasional dead backedge
2352       !tail()->is_top()) {
2353     adjust_loop_exit_prob(phase);
2354   }
2355 
2356   // Gate unrolling, RCE and peeling efforts.
2357   if (!_child &&                // If not an inner loop, do not split
2358       !_irreducible &&
2359       _allow_optimizations &&
2360       !tail()->is_top()) {     // Also ignore the occasional dead backedge
2361     if (!_has_call) {
2362         if (!iteration_split_impl(phase, old_new)) {
2363           return false;
2364         }
2365     } else if (policy_unswitching(phase)) {
2366       phase->do_unswitching(this, old_new);
2367     }
2368   }
2369 
2370   // Minor offset re-organization to remove loop-fallout uses of
2371   // trip counter when there was no major reshaping.
2372   phase->reorg_offsets(this);
2373 
2374   if (_next && !_next->iteration_split(phase, old_new))
2375     return false;
2376   return true;
2377 }
2378 
2379 
2380 //=============================================================================
2381 // Process all the loops in the loop tree and replace any fill
2382 // patterns with an intrisc version.
2383 bool PhaseIdealLoop::do_intrinsify_fill() {
2384   bool changed = false;
2385   for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2386     IdealLoopTree* lpt = iter.current();
2387     changed |= intrinsify_fill(lpt);
2388   }
2389   return changed;
2390 }
2391 
2392 
2393 // Examine an inner loop looking for a a single store of an invariant
2394 // value in a unit stride loop,
2395 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
2396                                      Node*& shift, Node*& con) {
2397   const char* msg = NULL;
2398   Node* msg_node = NULL;
2399 
2400   store_value = NULL;
2401   con = NULL;
2402   shift = NULL;
2403 
2404   // Process the loop looking for stores.  If there are multiple
2405   // stores or extra control flow give at this point.
2406   CountedLoopNode* head = lpt->_head->as_CountedLoop();
2407   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2408     Node* n = lpt->_body.at(i);
2409     if (n->outcnt() == 0) continue; // Ignore dead
2410     if (n->is_Store()) {
2411       if (store != NULL) {
2412         msg = "multiple stores";
2413         break;
2414       }
2415       int opc = n->Opcode();
2416       if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass || opc == Op_StoreCM) {
2417         msg = "oop fills not handled";
2418         break;
2419       }
2420       Node* value = n->in(MemNode::ValueIn);
2421       if (!lpt->is_invariant(value)) {
2422         msg  = "variant store value";
2423       } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
2424         msg = "not array address";
2425       }
2426       store = n;
2427       store_value = value;
2428     } else if (n->is_If() && n != head->loopexit()) {
2429       msg = "extra control flow";
2430       msg_node = n;
2431     }
2432   }
2433 
2434   if (store == NULL) {
2435     // No store in loop
2436     return false;
2437   }
2438 
2439   if (msg == NULL && head->stride_con() != 1) {
2440     // could handle negative strides too
2441     if (head->stride_con() < 0) {
2442       msg = "negative stride";
2443     } else {
2444       msg = "non-unit stride";
2445     }
2446   }
2447 
2448   if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
2449     msg = "can't handle store address";
2450     msg_node = store->in(MemNode::Address);
2451   }
2452 
2453   if (msg == NULL &&
2454       (!store->in(MemNode::Memory)->is_Phi() ||
2455        store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
2456     msg = "store memory isn't proper phi";
2457     msg_node = store->in(MemNode::Memory);
2458   }
2459 
2460   // Make sure there is an appropriate fill routine
2461   BasicType t = store->as_Mem()->memory_type();
2462   const char* fill_name;
2463   if (msg == NULL &&
2464       StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
2465     msg = "unsupported store";
2466     msg_node = store;
2467   }
2468 
2469   if (msg != NULL) {
2470 #ifndef PRODUCT
2471     if (TraceOptimizeFill) {
2472       tty->print_cr("not fill intrinsic candidate: %s", msg);
2473       if (msg_node != NULL) msg_node->dump();
2474     }
2475 #endif
2476     return false;
2477   }
2478 
2479   // Make sure the address expression can be handled.  It should be
2480   // head->phi * elsize + con.  head->phi might have a ConvI2L.
2481   Node* elements[4];
2482   Node* conv = NULL;
2483   bool found_index = false;
2484   int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
2485   for (int e = 0; e < count; e++) {
2486     Node* n = elements[e];
2487     if (n->is_Con() && con == NULL) {
2488       con = n;
2489     } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
2490       Node* value = n->in(1);
2491 #ifdef _LP64
2492       if (value->Opcode() == Op_ConvI2L) {
2493         conv = value;
2494         value = value->in(1);
2495       }
2496 #endif
2497       if (value != head->phi()) {
2498         msg = "unhandled shift in address";
2499       } else {
2500         if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) {
2501           msg = "scale doesn't match";
2502         } else {
2503           found_index = true;
2504           shift = n;
2505         }
2506       }
2507     } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
2508       if (n->in(1) == head->phi()) {
2509         found_index = true;
2510         conv = n;
2511       } else {
2512         msg = "unhandled input to ConvI2L";
2513       }
2514     } else if (n == head->phi()) {
2515       // no shift, check below for allowed cases
2516       found_index = true;
2517     } else {
2518       msg = "unhandled node in address";
2519       msg_node = n;
2520     }
2521   }
2522 
2523   if (count == -1) {
2524     msg = "malformed address expression";
2525     msg_node = store;
2526   }
2527 
2528   if (!found_index) {
2529     msg = "missing use of index";
2530   }
2531 
2532   // byte sized items won't have a shift
2533   if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
2534     msg = "can't find shift";
2535     msg_node = store;
2536   }
2537 
2538   if (msg != NULL) {
2539 #ifndef PRODUCT
2540     if (TraceOptimizeFill) {
2541       tty->print_cr("not fill intrinsic: %s", msg);
2542       if (msg_node != NULL) msg_node->dump();
2543     }
2544 #endif
2545     return false;
2546   }
2547 
2548   // No make sure all the other nodes in the loop can be handled
2549   VectorSet ok(Thread::current()->resource_area());
2550 
2551   // store related values are ok
2552   ok.set(store->_idx);
2553   ok.set(store->in(MemNode::Memory)->_idx);
2554 
2555   CountedLoopEndNode* loop_exit = head->loopexit();
2556   guarantee(loop_exit != NULL, "no loop exit node");
2557 
2558   // Loop structure is ok
2559   ok.set(head->_idx);
2560   ok.set(loop_exit->_idx);
2561   ok.set(head->phi()->_idx);
2562   ok.set(head->incr()->_idx);
2563   ok.set(loop_exit->cmp_node()->_idx);
2564   ok.set(loop_exit->in(1)->_idx);
2565 
2566   // Address elements are ok
2567   if (con)   ok.set(con->_idx);
2568   if (shift) ok.set(shift->_idx);
2569   if (conv)  ok.set(conv->_idx);
2570 
2571   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2572     Node* n = lpt->_body.at(i);
2573     if (n->outcnt() == 0) continue; // Ignore dead
2574     if (ok.test(n->_idx)) continue;
2575     // Backedge projection is ok
2576     if (n->is_IfTrue() && n->in(0) == loop_exit) continue;
2577     if (!n->is_AddP()) {
2578       msg = "unhandled node";
2579       msg_node = n;
2580       break;
2581     }
2582   }
2583 
2584   // Make sure no unexpected values are used outside the loop
2585   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2586     Node* n = lpt->_body.at(i);
2587     // These values can be replaced with other nodes if they are used
2588     // outside the loop.
2589     if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue;
2590     for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
2591       Node* use = iter.get();
2592       if (!lpt->_body.contains(use)) {
2593         msg = "node is used outside loop";
2594         // lpt->_body.dump();
2595         msg_node = n;
2596         break;
2597       }
2598     }
2599   }
2600 
2601 #ifdef ASSERT
2602   if (TraceOptimizeFill) {
2603     if (msg != NULL) {
2604       tty->print_cr("no fill intrinsic: %s", msg);
2605       if (msg_node != NULL) msg_node->dump();
2606     } else {
2607       tty->print_cr("fill intrinsic for:");
2608     }
2609     store->dump();
2610     if (Verbose) {
2611       lpt->_body.dump();
2612     }
2613   }
2614 #endif
2615 
2616   return msg == NULL;
2617 }
2618 
2619 
2620 
2621 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
2622   // Only for counted inner loops
2623   if (!lpt->is_counted() || !lpt->is_inner()) {
2624     return false;
2625   }
2626 
2627   // Must have constant stride
2628   CountedLoopNode* head = lpt->_head->as_CountedLoop();
2629   if (!head->is_valid_counted_loop() || !head->is_normal_loop()) {
2630     return false;
2631   }
2632 
2633   // Check that the body only contains a store of a loop invariant
2634   // value that is indexed by the loop phi.
2635   Node* store = NULL;
2636   Node* store_value = NULL;
2637   Node* shift = NULL;
2638   Node* offset = NULL;
2639   if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
2640     return false;
2641   }
2642 
2643 #ifndef PRODUCT
2644   if (TraceLoopOpts) {
2645     tty->print("ArrayFill    ");
2646     lpt->dump_head();
2647   }
2648 #endif
2649 
2650   // Now replace the whole loop body by a call to a fill routine that
2651   // covers the same region as the loop.
2652   Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
2653 
2654   // Build an expression for the beginning of the copy region
2655   Node* index = head->init_trip();
2656 #ifdef _LP64
2657   index = new (C) ConvI2LNode(index);
2658   _igvn.register_new_node_with_optimizer(index);
2659 #endif
2660   if (shift != NULL) {
2661     // byte arrays don't require a shift but others do.
2662     index = new (C) LShiftXNode(index, shift->in(2));
2663     _igvn.register_new_node_with_optimizer(index);
2664   }
2665   index = new (C) AddPNode(base, base, index);
2666   _igvn.register_new_node_with_optimizer(index);
2667   Node* from = new (C) AddPNode(base, index, offset);
2668   _igvn.register_new_node_with_optimizer(from);
2669   // Compute the number of elements to copy
2670   Node* len = new (C) SubINode(head->limit(), head->init_trip());
2671   _igvn.register_new_node_with_optimizer(len);
2672 
2673   BasicType t = store->as_Mem()->memory_type();
2674   bool aligned = false;
2675   if (offset != NULL && head->init_trip()->is_Con()) {
2676     int element_size = type2aelembytes(t);
2677     aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
2678   }
2679 
2680   // Build a call to the fill routine
2681   const char* fill_name;
2682   address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
2683   assert(fill != NULL, "what?");
2684 
2685   // Convert float/double to int/long for fill routines
2686   if (t == T_FLOAT) {
2687     store_value = new (C) MoveF2INode(store_value);
2688     _igvn.register_new_node_with_optimizer(store_value);
2689   } else if (t == T_DOUBLE) {
2690     store_value = new (C) MoveD2LNode(store_value);
2691     _igvn.register_new_node_with_optimizer(store_value);
2692   }
2693 
2694   if (CCallingConventionRequiresIntsAsLongs &&
2695       // See StubRoutines::select_fill_function for types. FLOAT has been converted to INT.
2696       (t == T_FLOAT || t == T_INT ||  is_subword_type(t))) {
2697     store_value = new (C) ConvI2LNode(store_value);
2698     _igvn.register_new_node_with_optimizer(store_value);
2699   }
2700 
2701   Node* mem_phi = store->in(MemNode::Memory);
2702   Node* result_ctrl;
2703   Node* result_mem;
2704   const TypeFunc* call_type = OptoRuntime::array_fill_Type();
2705   CallLeafNode *call = new (C) CallLeafNoFPNode(call_type, fill,
2706                                                 fill_name, TypeAryPtr::get_array_body_type(t));
2707   uint cnt = 0;
2708   call->init_req(TypeFunc::Parms + cnt++, from);
2709   call->init_req(TypeFunc::Parms + cnt++, store_value);
2710   if (CCallingConventionRequiresIntsAsLongs) {
2711     call->init_req(TypeFunc::Parms + cnt++, C->top());
2712   }
2713 #ifdef _LP64
2714   len = new (C) ConvI2LNode(len);
2715   _igvn.register_new_node_with_optimizer(len);
2716 #endif
2717   call->init_req(TypeFunc::Parms + cnt++, len);
2718 #ifdef _LP64
2719   call->init_req(TypeFunc::Parms + cnt++, C->top());
2720 #endif
2721   call->init_req(TypeFunc::Control,   head->init_control());
2722   call->init_req(TypeFunc::I_O,       C->top());       // Does no I/O.
2723   call->init_req(TypeFunc::Memory,    mem_phi->in(LoopNode::EntryControl));
2724   call->init_req(TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr));
2725   call->init_req(TypeFunc::FramePtr,  C->start()->proj_out(TypeFunc::FramePtr));
2726   _igvn.register_new_node_with_optimizer(call);
2727   result_ctrl = new (C) ProjNode(call,TypeFunc::Control);
2728   _igvn.register_new_node_with_optimizer(result_ctrl);
2729   result_mem = new (C) ProjNode(call,TypeFunc::Memory);
2730   _igvn.register_new_node_with_optimizer(result_mem);
2731 
2732 /* Disable following optimization until proper fix (add missing checks).
2733 
2734   // If this fill is tightly coupled to an allocation and overwrites
2735   // the whole body, allow it to take over the zeroing.
2736   AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
2737   if (alloc != NULL && alloc->is_AllocateArray()) {
2738     Node* length = alloc->as_AllocateArray()->Ideal_length();
2739     if (head->limit() == length &&
2740         head->init_trip() == _igvn.intcon(0)) {
2741       if (TraceOptimizeFill) {
2742         tty->print_cr("Eliminated zeroing in allocation");
2743       }
2744       alloc->maybe_set_complete(&_igvn);
2745     } else {
2746 #ifdef ASSERT
2747       if (TraceOptimizeFill) {
2748         tty->print_cr("filling array but bounds don't match");
2749         alloc->dump();
2750         head->init_trip()->dump();
2751         head->limit()->dump();
2752         length->dump();
2753       }
2754 #endif
2755     }
2756   }
2757 */
2758 
2759   // Redirect the old control and memory edges that are outside the loop.
2760   Node* exit = head->loopexit()->proj_out(0);
2761   // Sometimes the memory phi of the head is used as the outgoing
2762   // state of the loop.  It's safe in this case to replace it with the
2763   // result_mem.
2764   _igvn.replace_node(store->in(MemNode::Memory), result_mem);
2765   _igvn.replace_node(exit, result_ctrl);
2766   _igvn.replace_node(store, result_mem);
2767   // Any uses the increment outside of the loop become the loop limit.
2768   _igvn.replace_node(head->incr(), head->limit());
2769 
2770   // Disconnect the head from the loop.
2771   for (uint i = 0; i < lpt->_body.size(); i++) {
2772     Node* n = lpt->_body.at(i);
2773     _igvn.replace_node(n, C->top());
2774   }
2775 
2776   return true;
2777 }