1 /*
   2  * Copyright (c) 2000, 2018, 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/castnode.hpp"
  31 #include "opto/connode.hpp"
  32 #include "opto/convertnode.hpp"
  33 #include "opto/divnode.hpp"
  34 #include "opto/loopnode.hpp"
  35 #include "opto/mulnode.hpp"
  36 #include "opto/movenode.hpp"
  37 #include "opto/opaquenode.hpp"
  38 #include "opto/rootnode.hpp"
  39 #include "opto/runtime.hpp"
  40 #include "opto/subnode.hpp"
  41 #include "opto/superword.hpp"
  42 #include "opto/vectornode.hpp"
  43 
  44 //------------------------------is_loop_exit-----------------------------------
  45 // Given an IfNode, return the loop-exiting projection or NULL if both
  46 // arms remain in the loop.
  47 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
  48   if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
  49   PhaseIdealLoop *phase = _phase;
  50   // Test is an IfNode, has 2 projections.  If BOTH are in the loop
  51   // we need loop unswitching instead of peeling.
  52   if( !is_member(phase->get_loop( iff->raw_out(0) )) )
  53     return iff->raw_out(0);
  54   if( !is_member(phase->get_loop( iff->raw_out(1) )) )
  55     return iff->raw_out(1);
  56   return NULL;
  57 }
  58 
  59 
  60 //=============================================================================
  61 
  62 
  63 //------------------------------record_for_igvn----------------------------
  64 // Put loop body on igvn work list
  65 void IdealLoopTree::record_for_igvn() {
  66   for( uint i = 0; i < _body.size(); i++ ) {
  67     Node *n = _body.at(i);
  68     _phase->_igvn._worklist.push(n);
  69   }
  70   // put body of outer strip mined loop on igvn work list as well
  71   if (_head->is_CountedLoop() && _head->as_Loop()->is_strip_mined()) {
  72     CountedLoopNode* l = _head->as_CountedLoop();
  73     Node* outer_loop = l->outer_loop();
  74     assert(outer_loop != NULL, "missing piece of strip mined loop");
  75     _phase->_igvn._worklist.push(outer_loop);
  76     Node* outer_loop_tail = l->outer_loop_tail();
  77     assert(outer_loop_tail != NULL, "missing piece of strip mined loop");
  78     _phase->_igvn._worklist.push(outer_loop_tail);
  79     Node* outer_loop_end = l->outer_loop_end();
  80     assert(outer_loop_end != NULL, "missing piece of strip mined loop");
  81     _phase->_igvn._worklist.push(outer_loop_end);
  82     Node* outer_safepoint = l->outer_safepoint();
  83     assert(outer_safepoint != NULL, "missing piece of strip mined loop");
  84     _phase->_igvn._worklist.push(outer_safepoint);
  85     Node* cle_out = _head->as_CountedLoop()->loopexit()->proj_out(false);
  86     assert(cle_out != NULL, "missing piece of strip mined loop");
  87     _phase->_igvn._worklist.push(cle_out);
  88   }
  89 }
  90 
  91 //------------------------------compute_exact_trip_count-----------------------
  92 // Compute loop trip count if possible. Do not recalculate trip count for
  93 // split loops (pre-main-post) which have their limits and inits behind Opaque node.
  94 void IdealLoopTree::compute_trip_count(PhaseIdealLoop* phase) {
  95   if (!_head->as_Loop()->is_valid_counted_loop()) {
  96     return;
  97   }
  98   CountedLoopNode* cl = _head->as_CountedLoop();
  99   // Trip count may become nonexact for iteration split loops since
 100   // RCE modifies limits. Note, _trip_count value is not reset since
 101   // it is used to limit unrolling of main loop.
 102   cl->set_nonexact_trip_count();
 103 
 104   // Loop's test should be part of loop.
 105   if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
 106     return; // Infinite loop
 107 
 108 #ifdef ASSERT
 109   BoolTest::mask bt = cl->loopexit()->test_trip();
 110   assert(bt == BoolTest::lt || bt == BoolTest::gt ||
 111          bt == BoolTest::ne, "canonical test is expected");
 112 #endif
 113 
 114   Node* init_n = cl->init_trip();
 115   Node* limit_n = cl->limit();
 116   if (init_n != NULL && limit_n != NULL) {
 117     // Use longs to avoid integer overflow.
 118     int stride_con = cl->stride_con();
 119     const TypeInt* init_type = phase->_igvn.type(init_n)->is_int();
 120     const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
 121     jlong init_con = (stride_con > 0) ? init_type->_lo : init_type->_hi;
 122     jlong limit_con = (stride_con > 0) ? limit_type->_hi : limit_type->_lo;
 123     int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
 124     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
 125     if (trip_count > 0 && (julong)trip_count < (julong)max_juint) {
 126       if (init_n->is_Con() && limit_n->is_Con()) {
 127         // Set exact trip count.
 128         cl->set_exact_trip_count((uint)trip_count);
 129       } else if (cl->unrolled_count() == 1) {
 130         // Set maximum trip count before unrolling.
 131         cl->set_trip_count((uint)trip_count);
 132       }
 133     }
 134   }
 135 }
 136 
 137 //------------------------------compute_profile_trip_cnt----------------------------
 138 // Compute loop trip count from profile data as
 139 //    (backedge_count + loop_exit_count) / loop_exit_count
 140 
 141 float IdealLoopTree::compute_profile_trip_cnt_helper(Node* n) {
 142   if (n->is_If()) {
 143     IfNode *iff = n->as_If();
 144     if (iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN) {
 145       Node *exit = is_loop_exit(iff);
 146       if (exit) {
 147         float exit_prob = iff->_prob;
 148         if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
 149         if (exit_prob > PROB_MIN) {
 150           float exit_cnt = iff->_fcnt * exit_prob;
 151           return exit_cnt;
 152         }
 153       }
 154     }
 155   }
 156   if (n->is_Jump()) {
 157     JumpNode *jmp = n->as_Jump();
 158     if (jmp->_fcnt != COUNT_UNKNOWN) {
 159       float* probs = jmp->_probs;
 160       float exit_prob = 0;
 161       PhaseIdealLoop *phase = _phase;
 162       for (DUIterator_Fast imax, i = jmp->fast_outs(imax); i < imax; i++) {
 163         JumpProjNode* u = jmp->fast_out(i)->as_JumpProj();
 164         if (!is_member(_phase->get_loop(u))) {
 165           exit_prob += probs[u->_con];
 166         }
 167       }
 168       return exit_prob * jmp->_fcnt;
 169     }
 170   }
 171   return 0;
 172 }
 173 
 174 void IdealLoopTree::compute_profile_trip_cnt(PhaseIdealLoop *phase) {
 175   if (!_head->is_Loop()) {
 176     return;
 177   }
 178   LoopNode* head = _head->as_Loop();
 179   if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
 180     return; // Already computed
 181   }
 182   float trip_cnt = (float)max_jint; // default is big
 183 
 184   Node* back = head->in(LoopNode::LoopBackControl);
 185   while (back != head) {
 186     if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
 187         back->in(0) &&
 188         back->in(0)->is_If() &&
 189         back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
 190         back->in(0)->as_If()->_prob != PROB_UNKNOWN &&
 191         (back->Opcode() == Op_IfTrue ? 1-back->in(0)->as_If()->_prob : back->in(0)->as_If()->_prob) > PROB_MIN) {
 192       break;
 193     }
 194     back = phase->idom(back);
 195   }
 196   if (back != head) {
 197     assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
 198            back->in(0), "if-projection exists");
 199     IfNode* back_if = back->in(0)->as_If();
 200     float loop_back_cnt = back_if->_fcnt * (back->Opcode() == Op_IfTrue ? back_if->_prob : (1 - back_if->_prob));
 201 
 202     // Now compute a loop exit count
 203     float loop_exit_cnt = 0.0f;
 204     if (_child == NULL) {
 205       for( uint i = 0; i < _body.size(); i++ ) {
 206         Node *n = _body[i];
 207         loop_exit_cnt += compute_profile_trip_cnt_helper(n);
 208       }
 209     } else {
 210       ResourceMark rm;
 211       Unique_Node_List wq;
 212       wq.push(back);
 213       for (uint i = 0; i < wq.size(); i++) {
 214         Node *n = wq.at(i);
 215         assert(n->is_CFG(), "only control nodes");
 216         if (n != head) {
 217           if (n->is_Region()) {
 218             for (uint j = 1; j < n->req(); j++) {
 219               wq.push(n->in(j));
 220             }
 221           } else {
 222             loop_exit_cnt += compute_profile_trip_cnt_helper(n);
 223             wq.push(n->in(0));
 224           }
 225         }
 226       }
 227 
 228     }
 229     if (loop_exit_cnt > 0.0f) {
 230       trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
 231     } else {
 232       // No exit count so use
 233       trip_cnt = loop_back_cnt;
 234     }
 235   } else {
 236     head->mark_profile_trip_failed();
 237   }
 238 #ifndef PRODUCT
 239   if (TraceProfileTripCount) {
 240     tty->print_cr("compute_profile_trip_cnt  lp: %d cnt: %f\n", head->_idx, trip_cnt);
 241   }
 242 #endif
 243   head->set_profile_trip_cnt(trip_cnt);
 244 }
 245 
 246 //---------------------is_invariant_addition-----------------------------
 247 // Return nonzero index of invariant operand for an Add or Sub
 248 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
 249 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
 250   int op = n->Opcode();
 251   if (op == Op_AddI || op == Op_SubI) {
 252     bool in1_invar = this->is_invariant(n->in(1));
 253     bool in2_invar = this->is_invariant(n->in(2));
 254     if (in1_invar && !in2_invar) return 1;
 255     if (!in1_invar && in2_invar) return 2;
 256   }
 257   return 0;
 258 }
 259 
 260 //---------------------reassociate_add_sub-----------------------------
 261 // Reassociate invariant add and subtract expressions:
 262 //
 263 // inv1 + (x + inv2)  =>  ( inv1 + inv2) + x
 264 // (x + inv2) + inv1  =>  ( inv1 + inv2) + x
 265 // inv1 + (x - inv2)  =>  ( inv1 - inv2) + x
 266 // inv1 - (inv2 - x)  =>  ( inv1 - inv2) + x
 267 // (x + inv2) - inv1  =>  (-inv1 + inv2) + x
 268 // (x - inv2) + inv1  =>  ( inv1 - inv2) + x
 269 // (x - inv2) - inv1  =>  (-inv1 - inv2) + x
 270 // inv1 + (inv2 - x)  =>  ( inv1 + inv2) - x
 271 // inv1 - (x - inv2)  =>  ( inv1 + inv2) - x
 272 // (inv2 - x) + inv1  =>  ( inv1 + inv2) - x
 273 // (inv2 - x) - inv1  =>  (-inv1 + inv2) - x
 274 // inv1 - (x + inv2)  =>  ( inv1 - inv2) - x
 275 //
 276 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
 277   if ((!n1->is_Add() && !n1->is_Sub()) || n1->outcnt() == 0) return NULL;
 278   if (is_invariant(n1)) return NULL;
 279   int inv1_idx = is_invariant_addition(n1, phase);
 280   if (!inv1_idx) return NULL;
 281   // Don't mess with add of constant (igvn moves them to expression tree root.)
 282   if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
 283   Node* inv1 = n1->in(inv1_idx);
 284   Node* n2 = n1->in(3 - inv1_idx);
 285   int inv2_idx = is_invariant_addition(n2, phase);
 286   if (!inv2_idx) return NULL;
 287   Node* x    = n2->in(3 - inv2_idx);
 288   Node* inv2 = n2->in(inv2_idx);
 289 
 290   bool neg_x    = n2->is_Sub() && inv2_idx == 1;
 291   bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
 292   bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
 293   if (n1->is_Sub() && inv1_idx == 1) {
 294     neg_x    = !neg_x;
 295     neg_inv2 = !neg_inv2;
 296   }
 297   Node* inv1_c = phase->get_ctrl(inv1);
 298   Node* inv2_c = phase->get_ctrl(inv2);
 299   Node* n_inv1;
 300   if (neg_inv1) {
 301     Node *zero = phase->_igvn.intcon(0);
 302     phase->set_ctrl(zero, phase->C->root());
 303     n_inv1 = new SubINode(zero, inv1);
 304     phase->register_new_node(n_inv1, inv1_c);
 305   } else {
 306     n_inv1 = inv1;
 307   }
 308   Node* inv;
 309   if (neg_inv2) {
 310     inv = new SubINode(n_inv1, inv2);
 311   } else {
 312     inv = new AddINode(n_inv1, inv2);
 313   }
 314   phase->register_new_node(inv, phase->get_early_ctrl(inv));
 315 
 316   Node* addx;
 317   if (neg_x) {
 318     addx = new SubINode(inv, x);
 319   } else {
 320     addx = new AddINode(x, inv);
 321   }
 322   phase->register_new_node(addx, phase->get_ctrl(x));
 323   phase->_igvn.replace_node(n1, addx);
 324   assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
 325   _body.yank(n1);
 326   return addx;
 327 }
 328 
 329 //---------------------reassociate_invariants-----------------------------
 330 // Reassociate invariant expressions:
 331 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
 332   for (int i = _body.size() - 1; i >= 0; i--) {
 333     Node *n = _body.at(i);
 334     for (int j = 0; j < 5; j++) {
 335       Node* nn = reassociate_add_sub(n, phase);
 336       if (nn == NULL) break;
 337       n = nn; // again
 338     };
 339   }
 340 }
 341 
 342 //------------------------------policy_peeling---------------------------------
 343 // Return TRUE or FALSE if the loop should be peeled or not.  Peel if we can
 344 // make some loop-invariant test (usually a null-check) happen before the loop.
 345 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
 346   Node *test = ((IdealLoopTree*)this)->tail();
 347   int  body_size = ((IdealLoopTree*)this)->_body.size();
 348   // Peeling does loop cloning which can result in O(N^2) node construction
 349   if( body_size > 255 /* Prevent overflow for large body_size */
 350       || (body_size * body_size + phase->C->live_nodes()) > phase->C->max_node_limit() ) {
 351     return false;           // too large to safely clone
 352   }
 353 
 354   // check for vectorized loops, any peeling done was already applied
 355   if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) return false;
 356 
 357   if (_head->is_CountedLoop() && _head->as_CountedLoop()->trip_count() == 1) {
 358     return false;
 359   }
 360 
 361   while( test != _head ) {      // Scan till run off top of loop
 362     if( test->is_If() ) {       // Test?
 363       Node *ctrl = phase->get_ctrl(test->in(1));
 364       if (ctrl->is_top())
 365         return false;           // Found dead test on live IF?  No peeling!
 366       // Standard IF only has one input value to check for loop invariance
 367       assert(test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd || test->Opcode() == Op_RangeCheck, "Check this code when new subtype is added");
 368       // Condition is not a member of this loop?
 369       if( !is_member(phase->get_loop(ctrl)) &&
 370           is_loop_exit(test) )
 371         return true;            // Found reason to peel!
 372     }
 373     // Walk up dominators to loop _head looking for test which is
 374     // executed on every path thru loop.
 375     test = phase->idom(test);
 376   }
 377   return false;
 378 }
 379 
 380 //------------------------------peeled_dom_test_elim---------------------------
 381 // If we got the effect of peeling, either by actually peeling or by making
 382 // a pre-loop which must execute at least once, we can remove all
 383 // loop-invariant dominated tests in the main body.
 384 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
 385   bool progress = true;
 386   while( progress ) {
 387     progress = false;           // Reset for next iteration
 388     Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
 389     Node *test = prev->in(0);
 390     while( test != loop->_head ) { // Scan till run off top of loop
 391 
 392       int p_op = prev->Opcode();
 393       if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
 394           test->is_If() &&      // Test?
 395           !test->in(1)->is_Con() && // And not already obvious?
 396           // Condition is not a member of this loop?
 397           !loop->is_member(get_loop(get_ctrl(test->in(1))))){
 398         // Walk loop body looking for instances of this test
 399         for( uint i = 0; i < loop->_body.size(); i++ ) {
 400           Node *n = loop->_body.at(i);
 401           if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
 402             // IfNode was dominated by version in peeled loop body
 403             progress = true;
 404             dominated_by( old_new[prev->_idx], n );
 405           }
 406         }
 407       }
 408       prev = test;
 409       test = idom(test);
 410     } // End of scan tests in loop
 411 
 412   } // End of while( progress )
 413 }
 414 
 415 //------------------------------do_peeling-------------------------------------
 416 // Peel the first iteration of the given loop.
 417 // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 418 //         The pre-loop illegally has 2 control users (old & new loops).
 419 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 420 //         Do this by making the old-loop fall-in edges act as if they came
 421 //         around the loopback from the prior iteration (follow the old-loop
 422 //         backedges) and then map to the new peeled iteration.  This leaves
 423 //         the pre-loop with only 1 user (the new peeled iteration), but the
 424 //         peeled-loop backedge has 2 users.
 425 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 426 //         extra backedge user.
 427 //
 428 //                   orig
 429 //
 430 //                  stmt1
 431 //                    |
 432 //                    v
 433 //              loop predicate
 434 //                    |
 435 //                    v
 436 //                   loop<----+
 437 //                     |      |
 438 //                   stmt2    |
 439 //                     |      |
 440 //                     v      |
 441 //                    if      ^
 442 //                   / \      |
 443 //                  /   \     |
 444 //                 v     v    |
 445 //               false true   |
 446 //               /       \    |
 447 //              /         ----+
 448 //             |
 449 //             v
 450 //           exit
 451 //
 452 //
 453 //            after clone loop
 454 //
 455 //                   stmt1
 456 //                     |
 457 //                     v
 458 //               loop predicate
 459 //                 /       \
 460 //        clone   /         \   orig
 461 //               /           \
 462 //              /             \
 463 //             v               v
 464 //   +---->loop clone          loop<----+
 465 //   |      |                    |      |
 466 //   |    stmt2 clone          stmt2    |
 467 //   |      |                    |      |
 468 //   |      v                    v      |
 469 //   ^      if clone            If      ^
 470 //   |      / \                / \      |
 471 //   |     /   \              /   \     |
 472 //   |    v     v            v     v    |
 473 //   |    true  false      false true   |
 474 //   |    /         \      /       \    |
 475 //   +----           \    /         ----+
 476 //                    \  /
 477 //                    1v v2
 478 //                  region
 479 //                     |
 480 //                     v
 481 //                   exit
 482 //
 483 //
 484 //         after peel and predicate move
 485 //
 486 //                   stmt1
 487 //                    /
 488 //                   /
 489 //        clone     /            orig
 490 //                 /
 491 //                /              +----------+
 492 //               /               |          |
 493 //              /          loop predicate   |
 494 //             /                 |          |
 495 //            v                  v          |
 496 //   TOP-->loop clone          loop<----+   |
 497 //          |                    |      |   |
 498 //        stmt2 clone          stmt2    |   |
 499 //          |                    |      |   ^
 500 //          v                    v      |   |
 501 //          if clone            If      ^   |
 502 //          / \                / \      |   |
 503 //         /   \              /   \     |   |
 504 //        v     v            v     v    |   |
 505 //      true   false      false  true   |   |
 506 //        |         \      /       \    |   |
 507 //        |          \    /         ----+   ^
 508 //        |           \  /                  |
 509 //        |           1v v2                 |
 510 //        v         region                  |
 511 //        |            |                    |
 512 //        |            v                    |
 513 //        |          exit                   |
 514 //        |                                 |
 515 //        +--------------->-----------------+
 516 //
 517 //
 518 //              final graph
 519 //
 520 //                  stmt1
 521 //                    |
 522 //                    v
 523 //                  stmt2 clone
 524 //                    |
 525 //                    v
 526 //                   if clone
 527 //                  / |
 528 //                 /  |
 529 //                v   v
 530 //            false  true
 531 //             |      |
 532 //             |      v
 533 //             | loop predicate
 534 //             |      |
 535 //             |      v
 536 //             |     loop<----+
 537 //             |      |       |
 538 //             |    stmt2     |
 539 //             |      |       |
 540 //             |      v       |
 541 //             v      if      ^
 542 //             |     /  \     |
 543 //             |    /    \    |
 544 //             |   v     v    |
 545 //             | false  true  |
 546 //             |  |        \  |
 547 //             v  v         --+
 548 //            region
 549 //              |
 550 //              v
 551 //             exit
 552 //
 553 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
 554 
 555   C->set_major_progress();
 556   // Peeling a 'main' loop in a pre/main/post situation obfuscates the
 557   // 'pre' loop from the main and the 'pre' can no longer have its
 558   // iterations adjusted.  Therefore, we need to declare this loop as
 559   // no longer a 'main' loop; it will need new pre and post loops before
 560   // we can do further RCE.
 561 #ifndef PRODUCT
 562   if (TraceLoopOpts) {
 563     tty->print("Peel         ");
 564     loop->dump_head();
 565   }
 566 #endif
 567   LoopNode* head = loop->_head->as_Loop();
 568   bool counted_loop = head->is_CountedLoop();
 569   if (counted_loop) {
 570     CountedLoopNode *cl = head->as_CountedLoop();
 571     assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
 572     cl->set_trip_count(cl->trip_count() - 1);
 573     if (cl->is_main_loop()) {
 574       cl->set_normal_loop();
 575 #ifndef PRODUCT
 576       if (PrintOpto && VerifyLoopOptimizations) {
 577         tty->print("Peeling a 'main' loop; resetting to 'normal' ");
 578         loop->dump_head();
 579       }
 580 #endif
 581     }
 582   }
 583   Node* entry = head->in(LoopNode::EntryControl);
 584 
 585   // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 586   //         The pre-loop illegally has 2 control users (old & new loops).
 587   clone_loop(loop, old_new, dom_depth(head->skip_strip_mined()), ControlAroundStripMined);
 588 
 589   // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 590   //         Do this by making the old-loop fall-in edges act as if they came
 591   //         around the loopback from the prior iteration (follow the old-loop
 592   //         backedges) and then map to the new peeled iteration.  This leaves
 593   //         the pre-loop with only 1 user (the new peeled iteration), but the
 594   //         peeled-loop backedge has 2 users.
 595   Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx];
 596   _igvn.hash_delete(head->skip_strip_mined());
 597   head->skip_strip_mined()->set_req(LoopNode::EntryControl, new_entry);
 598   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
 599     Node* old = head->fast_out(j);
 600     if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
 601       Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
 602       if (!new_exit_value )     // Backedge value is ALSO loop invariant?
 603         // Then loop body backedge value remains the same.
 604         new_exit_value = old->in(LoopNode::LoopBackControl);
 605       _igvn.hash_delete(old);
 606       old->set_req(LoopNode::EntryControl, new_exit_value);
 607     }
 608   }
 609 
 610 
 611   // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 612   //         extra backedge user.
 613   Node* new_head = old_new[head->_idx];
 614   _igvn.hash_delete(new_head);
 615   new_head->set_req(LoopNode::LoopBackControl, C->top());
 616   for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
 617     Node* use = new_head->fast_out(j2);
 618     if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
 619       _igvn.hash_delete(use);
 620       use->set_req(LoopNode::LoopBackControl, C->top());
 621     }
 622   }
 623 
 624 
 625   // Step 4: Correct dom-depth info.  Set to loop-head depth.
 626   int dd = dom_depth(head);
 627   set_idom(head, head->in(1), dd);
 628   for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
 629     Node *old = loop->_body.at(j3);
 630     Node *nnn = old_new[old->_idx];
 631     if (!has_ctrl(nnn))
 632       set_idom(nnn, idom(nnn), dd-1);
 633   }
 634 
 635   // Now force out all loop-invariant dominating tests.  The optimizer
 636   // finds some, but we _know_ they are all useless.
 637   peeled_dom_test_elim(loop,old_new);
 638 
 639   loop->record_for_igvn();
 640 }
 641 
 642 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop
 643 
 644 //------------------------------policy_maximally_unroll------------------------
 645 // Calculate exact loop trip count and return true if loop can be maximally
 646 // unrolled.
 647 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
 648   CountedLoopNode *cl = _head->as_CountedLoop();
 649   assert(cl->is_normal_loop(), "");
 650   if (!cl->is_valid_counted_loop())
 651     return false; // Malformed counted loop
 652 
 653   if (!cl->has_exact_trip_count()) {
 654     // Trip count is not exact.
 655     return false;
 656   }
 657 
 658   uint trip_count = cl->trip_count();
 659   // Note, max_juint is used to indicate unknown trip count.
 660   assert(trip_count > 1, "one iteration loop should be optimized out already");
 661   assert(trip_count < max_juint, "exact trip_count should be less than max_uint.");
 662 
 663   // Real policy: if we maximally unroll, does it get too big?
 664   // Allow the unrolled mess to get larger than standard loop
 665   // size.  After all, it will no longer be a loop.
 666   uint body_size    = _body.size();
 667   uint unroll_limit = (uint)LoopUnrollLimit * 4;
 668   assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
 669   if (trip_count > unroll_limit || body_size > unroll_limit) {
 670     return false;
 671   }
 672 
 673   // Fully unroll a loop with few iterations regardless next
 674   // conditions since following loop optimizations will split
 675   // such loop anyway (pre-main-post).
 676   if (trip_count <= 3)
 677     return true;
 678 
 679   // Take into account that after unroll conjoined heads and tails will fold,
 680   // otherwise policy_unroll() may allow more unrolling than max unrolling.
 681   uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count;
 682   uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE;
 683   if (body_size != tst_body_size) // Check for int overflow
 684     return false;
 685   if (new_body_size > unroll_limit ||
 686       // Unrolling can result in a large amount of node construction
 687       new_body_size >= phase->C->max_node_limit() - phase->C->live_nodes()) {
 688     return false;
 689   }
 690 
 691   // Do not unroll a loop with String intrinsics code.
 692   // String intrinsics are large and have loops.
 693   for (uint k = 0; k < _body.size(); k++) {
 694     Node* n = _body.at(k);
 695     switch (n->Opcode()) {
 696       case Op_StrComp:
 697       case Op_StrEquals:
 698       case Op_StrIndexOf:
 699       case Op_StrIndexOfChar:
 700       case Op_EncodeISOArray:
 701       case Op_AryEq:
 702       case Op_HasNegatives: {
 703         return false;
 704       }
 705 #if INCLUDE_RTM_OPT
 706       case Op_FastLock:
 707       case Op_FastUnlock: {
 708         // Don't unroll RTM locking code because it is large.
 709         if (UseRTMLocking) {
 710           return false;
 711         }
 712       }
 713 #endif
 714     } // switch
 715   }
 716 
 717   return true; // Do maximally unroll
 718 }
 719 
 720 
 721 //------------------------------policy_unroll----------------------------------
 722 // Return TRUE or FALSE if the loop should be unrolled or not.  Unroll if
 723 // the loop is a CountedLoop and the body is small enough.
 724 bool IdealLoopTree::policy_unroll(PhaseIdealLoop *phase) {
 725 
 726   CountedLoopNode *cl = _head->as_CountedLoop();
 727   assert(cl->is_normal_loop() || cl->is_main_loop(), "");
 728 
 729   if (!cl->is_valid_counted_loop())
 730     return false; // Malformed counted loop
 731 
 732   // Protect against over-unrolling.
 733   // After split at least one iteration will be executed in pre-loop.
 734   if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false;
 735 
 736   _local_loop_unroll_limit = LoopUnrollLimit;
 737   _local_loop_unroll_factor = 4;
 738   int future_unroll_ct = cl->unrolled_count() * 2;
 739   if (!cl->is_vectorized_loop()) {
 740     if (future_unroll_ct > LoopMaxUnroll) return false;
 741   } else {
 742     // obey user constraints on vector mapped loops with additional unrolling applied
 743     int unroll_constraint = (cl->slp_max_unroll()) ? cl->slp_max_unroll() : 1;
 744     if ((future_unroll_ct / unroll_constraint) > LoopMaxUnroll) return false;
 745   }
 746 
 747   // Check for initial stride being a small enough constant
 748   if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false;
 749 
 750   // Don't unroll if the next round of unrolling would push us
 751   // over the expected trip count of the loop.  One is subtracted
 752   // from the expected trip count because the pre-loop normally
 753   // executes 1 iteration.
 754   if (UnrollLimitForProfileCheck > 0 &&
 755       cl->profile_trip_cnt() != COUNT_UNKNOWN &&
 756       future_unroll_ct        > UnrollLimitForProfileCheck &&
 757       (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
 758     return false;
 759   }
 760 
 761   // When unroll count is greater than LoopUnrollMin, don't unroll if:
 762   //   the residual iterations are more than 10% of the trip count
 763   //   and rounds of "unroll,optimize" are not making significant progress
 764   //   Progress defined as current size less than 20% larger than previous size.
 765   if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
 766       future_unroll_ct > LoopUnrollMin &&
 767       (future_unroll_ct - 1) * (100 / LoopPercentProfileLimit) > cl->profile_trip_cnt() &&
 768       1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
 769     return false;
 770   }
 771 
 772   Node *init_n = cl->init_trip();
 773   Node *limit_n = cl->limit();
 774   int stride_con = cl->stride_con();
 775   if (limit_n == NULL) return false; // We will dereference it below.
 776 
 777   // Non-constant bounds.
 778   // Protect against over-unrolling when init or/and limit are not constant
 779   // (so that trip_count's init value is maxint) but iv range is known.
 780   if (init_n == NULL || !init_n->is_Con() || !limit_n->is_Con()) {
 781     Node* phi = cl->phi();
 782     if (phi != NULL) {
 783       assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
 784       const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
 785       int next_stride = stride_con * 2; // stride after this unroll
 786       if (next_stride > 0) {
 787         if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
 788             iv_type->_lo + next_stride >  iv_type->_hi) {
 789           return false;  // over-unrolling
 790         }
 791       } else if (next_stride < 0) {
 792         if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
 793             iv_type->_hi + next_stride <  iv_type->_lo) {
 794           return false;  // over-unrolling
 795         }
 796       }
 797     }
 798   }
 799 
 800   // After unroll limit will be adjusted: new_limit = limit-stride.
 801   // Bailout if adjustment overflow.
 802   const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
 803   if ((stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi)) ||
 804       (stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo)))
 805     return false;  // overflow
 806 
 807   // Adjust body_size to determine if we unroll or not
 808   uint body_size = _body.size();
 809   // Key test to unroll loop in CRC32 java code
 810   int xors_in_loop = 0;
 811   // Also count ModL, DivL and MulL which expand mightly
 812   for (uint k = 0; k < _body.size(); k++) {
 813     Node* n = _body.at(k);
 814     switch (n->Opcode()) {
 815       case Op_XorI: xors_in_loop++; break; // CRC32 java code
 816       case Op_ModL: body_size += 30; break;
 817       case Op_DivL: body_size += 30; break;
 818       case Op_MulL: body_size += 10; break;
 819       case Op_StrComp:
 820       case Op_StrEquals:
 821       case Op_StrIndexOf:
 822       case Op_StrIndexOfChar:
 823       case Op_EncodeISOArray:
 824       case Op_AryEq:
 825       case Op_HasNegatives: {
 826         // Do not unroll a loop with String intrinsics code.
 827         // String intrinsics are large and have loops.
 828         return false;
 829       }
 830 #if INCLUDE_RTM_OPT
 831       case Op_FastLock:
 832       case Op_FastUnlock: {
 833         // Don't unroll RTM locking code because it is large.
 834         if (UseRTMLocking) {
 835           return false;
 836         }
 837       }
 838 #endif
 839     } // switch
 840   }
 841 
 842   if (UseSuperWord) {
 843     if (!cl->is_reduction_loop()) {
 844       phase->mark_reductions(this);
 845     }
 846 
 847     // Only attempt slp analysis when user controls do not prohibit it
 848     if (LoopMaxUnroll > _local_loop_unroll_factor) {
 849       // Once policy_slp_analysis succeeds, mark the loop with the
 850       // maximal unroll factor so that we minimize analysis passes
 851       if (future_unroll_ct >= _local_loop_unroll_factor) {
 852         policy_unroll_slp_analysis(cl, phase, future_unroll_ct);
 853       }
 854     }
 855   }
 856 
 857   int slp_max_unroll_factor = cl->slp_max_unroll();
 858   if ((LoopMaxUnroll < slp_max_unroll_factor) && FLAG_IS_DEFAULT(LoopMaxUnroll) && UseSubwordForMaxVector) {
 859     LoopMaxUnroll = slp_max_unroll_factor;
 860   }
 861   if (cl->has_passed_slp()) {
 862     if (slp_max_unroll_factor >= future_unroll_ct) return true;
 863     // Normal case: loop too big
 864     return false;
 865   }
 866 
 867   // Check for being too big
 868   if (body_size > (uint)_local_loop_unroll_limit) {
 869     if ((cl->is_subword_loop() || xors_in_loop >= 4) && body_size < (uint)LoopUnrollLimit * 4) {
 870       return true;
 871     }
 872     // Normal case: loop too big
 873     return false;
 874   }
 875 
 876   if (cl->do_unroll_only()) {
 877     if (TraceSuperWordLoopUnrollAnalysis) {
 878       tty->print_cr("policy_unroll passed vector loop(vlen=%d,factor = %d)\n", slp_max_unroll_factor, future_unroll_ct);
 879     }
 880   }
 881 
 882   // Unroll once!  (Each trip will soon do double iterations)
 883   return true;
 884 }
 885 
 886 void IdealLoopTree::policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct) {
 887   // Enable this functionality target by target as needed
 888   if (SuperWordLoopUnrollAnalysis) {
 889     if (!cl->was_slp_analyzed()) {
 890       SuperWord sw(phase);
 891       sw.transform_loop(this, false);
 892 
 893       // If the loop is slp canonical analyze it
 894       if (sw.early_return() == false) {
 895         sw.unrolling_analysis(_local_loop_unroll_factor);
 896       }
 897     }
 898 
 899     if (cl->has_passed_slp()) {
 900       int slp_max_unroll_factor = cl->slp_max_unroll();
 901       if (slp_max_unroll_factor >= future_unroll_ct) {
 902         int new_limit = cl->node_count_before_unroll() * slp_max_unroll_factor;
 903         if (new_limit > LoopUnrollLimit) {
 904           if (TraceSuperWordLoopUnrollAnalysis) {
 905             tty->print_cr("slp analysis unroll=%d, default limit=%d\n", new_limit, _local_loop_unroll_limit);
 906           }
 907           _local_loop_unroll_limit = new_limit;
 908         }
 909       }
 910     }
 911   }
 912 }
 913 
 914 //------------------------------policy_align-----------------------------------
 915 // Return TRUE or FALSE if the loop should be cache-line aligned.  Gather the
 916 // expression that does the alignment.  Note that only one array base can be
 917 // aligned in a loop (unless the VM guarantees mutual alignment).  Note that
 918 // if we vectorize short memory ops into longer memory ops, we may want to
 919 // increase alignment.
 920 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
 921   return false;
 922 }
 923 
 924 //------------------------------policy_range_check-----------------------------
 925 // Return TRUE or FALSE if the loop should be range-check-eliminated.
 926 // Actually we do iteration-splitting, a more powerful form of RCE.
 927 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
 928   if (!RangeCheckElimination) return false;
 929 
 930   CountedLoopNode *cl = _head->as_CountedLoop();
 931   // If we unrolled with no intention of doing RCE and we later
 932   // changed our minds, we got no pre-loop.  Either we need to
 933   // make a new pre-loop, or we gotta disallow RCE.
 934   if (cl->is_main_no_pre_loop()) return false; // Disallowed for now.
 935   Node *trip_counter = cl->phi();
 936 
 937   // check for vectorized loops, some opts are no longer needed
 938   if (cl->do_unroll_only()) return false;
 939 
 940   // Check loop body for tests of trip-counter plus loop-invariant vs
 941   // loop-invariant.
 942   for (uint i = 0; i < _body.size(); i++) {
 943     Node *iff = _body[i];
 944     if (iff->Opcode() == Op_If ||
 945         iff->Opcode() == Op_RangeCheck) { // Test?
 946 
 947       // Comparing trip+off vs limit
 948       Node *bol = iff->in(1);
 949       if (bol->req() != 2) continue; // dead constant test
 950       if (!bol->is_Bool()) {
 951         assert(bol->Opcode() == Op_Conv2B, "predicate check only");
 952         continue;
 953       }
 954       if (bol->as_Bool()->_test._test == BoolTest::ne)
 955         continue; // not RC
 956 
 957       Node *cmp = bol->in(1);
 958       Node *rc_exp = cmp->in(1);
 959       Node *limit = cmp->in(2);
 960 
 961       Node *limit_c = phase->get_ctrl(limit);
 962       if( limit_c == phase->C->top() )
 963         return false;           // Found dead test on live IF?  No RCE!
 964       if( is_member(phase->get_loop(limit_c) ) ) {
 965         // Compare might have operands swapped; commute them
 966         rc_exp = cmp->in(2);
 967         limit  = cmp->in(1);
 968         limit_c = phase->get_ctrl(limit);
 969         if( is_member(phase->get_loop(limit_c) ) )
 970           continue;             // Both inputs are loop varying; cannot RCE
 971       }
 972 
 973       if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
 974         continue;
 975       }
 976       // Yeah!  Found a test like 'trip+off vs limit'
 977       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
 978       // we need loop unswitching instead of iteration splitting.
 979       if( is_loop_exit(iff) )
 980         return true;            // Found reason to split iterations
 981     } // End of is IF
 982   }
 983 
 984   return false;
 985 }
 986 
 987 //------------------------------policy_peel_only-------------------------------
 988 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned.  Useful
 989 // for unrolling loops with NO array accesses.
 990 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
 991   // check for vectorized loops, any peeling done was already applied
 992   if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) return false;
 993 
 994   for( uint i = 0; i < _body.size(); i++ )
 995     if( _body[i]->is_Mem() )
 996       return false;
 997 
 998   // No memory accesses at all!
 999   return true;
1000 }
1001 
1002 //------------------------------clone_up_backedge_goo--------------------------
1003 // If Node n lives in the back_ctrl block and cannot float, we clone a private
1004 // version of n in preheader_ctrl block and return that, otherwise return n.
1005 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) {
1006   if( get_ctrl(n) != back_ctrl ) return n;
1007 
1008   // Only visit once
1009   if (visited.test_set(n->_idx)) {
1010     Node *x = clones.find(n->_idx);
1011     if (x != NULL)
1012       return x;
1013     return n;
1014   }
1015 
1016   Node *x = NULL;               // If required, a clone of 'n'
1017   // Check for 'n' being pinned in the backedge.
1018   if( n->in(0) && n->in(0) == back_ctrl ) {
1019     assert(clones.find(n->_idx) == NULL, "dead loop");
1020     x = n->clone();             // Clone a copy of 'n' to preheader
1021     clones.push(x, n->_idx);
1022     x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
1023   }
1024 
1025   // Recursive fixup any other input edges into x.
1026   // If there are no changes we can just return 'n', otherwise
1027   // we need to clone a private copy and change it.
1028   for( uint i = 1; i < n->req(); i++ ) {
1029     Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones );
1030     if( g != n->in(i) ) {
1031       if( !x ) {
1032         assert(clones.find(n->_idx) == NULL, "dead loop");
1033         x = n->clone();
1034         clones.push(x, n->_idx);
1035       }
1036       x->set_req(i, g);
1037     }
1038   }
1039   if( x ) {                     // x can legally float to pre-header location
1040     register_new_node( x, preheader_ctrl );
1041     return x;
1042   } else {                      // raise n to cover LCA of uses
1043     set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
1044   }
1045   return n;
1046 }
1047 
1048 Node* PhaseIdealLoop::cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop) {
1049   Node* castii = new CastIINode(incr, TypeInt::INT, true);
1050   castii->set_req(0, ctrl);
1051   register_new_node(castii, ctrl);
1052   for (DUIterator_Fast imax, i = incr->fast_outs(imax); i < imax; i++) {
1053     Node* n = incr->fast_out(i);
1054     if (n->is_Phi() && n->in(0) == loop) {
1055       int nrep = n->replace_edge(incr, castii);
1056       return castii;
1057     }
1058   }
1059   return NULL;
1060 }
1061 
1062 // Make a copy of the skeleton range check predicates before the main
1063 // loop and set the initial value of loop as input. After unrolling,
1064 // the range of values for the induction variable in the main loop can
1065 // fall outside the allowed range of values by the array access (main
1066 // loop is never executed). When that happens, range check
1067 // CastII/ConvI2L nodes cause some data paths to die. For consistency,
1068 // the control paths must die too but the range checks were removed by
1069 // predication. The range checks that we add here guarantee that they do.
1070 void PhaseIdealLoop::duplicate_predicates_helper(Node* predicate, Node* castii, IdealLoopTree* outer_loop,
1071                                                  LoopNode* outer_main_head, uint dd_main_head) {
1072   if (predicate != NULL) {
1073     IfNode* iff = predicate->in(0)->as_If();
1074     ProjNode* uncommon_proj = iff->proj_out(1 - predicate->as_Proj()->_con);
1075     Node* rgn = uncommon_proj->unique_ctrl_out();
1076     assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
1077     assert(iff->in(1)->in(1)->Opcode() == Op_Opaque1, "unexpected predicate shape");
1078     predicate = iff->in(0);
1079     Node* current_proj = outer_main_head->in(LoopNode::EntryControl);
1080     Node* prev_proj = current_proj;
1081     while (predicate != NULL && predicate->is_Proj() && predicate->in(0)->is_If()) {
1082       iff = predicate->in(0)->as_If();
1083       uncommon_proj = iff->proj_out(1 - predicate->as_Proj()->_con);
1084       if (uncommon_proj->unique_ctrl_out() != rgn)
1085         break;
1086       if (iff->in(1)->Opcode() == Op_Opaque4) {
1087         // Clone the predicate twice and initialize one with the initial
1088         // value of the loop induction variable. Leave the other predicate
1089         // to be initialized when increasing the stride during loop unrolling.
1090         prev_proj = update_skeleton_predicate(iff, castii, predicate, uncommon_proj, current_proj, outer_loop, prev_proj);
1091         Node* value = new Opaque1Node(C, castii);
1092         register_new_node(value, current_proj);
1093         prev_proj = update_skeleton_predicate(iff, value, predicate, uncommon_proj, current_proj, outer_loop, prev_proj);
1094         // Remove the skeleton predicate from the pre-loop
1095         _igvn.replace_input_of(iff, 1, _igvn.intcon(1));
1096       }
1097       predicate = predicate->in(0)->in(0);
1098     }
1099     _igvn.replace_input_of(outer_main_head, LoopNode::EntryControl, prev_proj);
1100     set_idom(outer_main_head, prev_proj, dd_main_head);
1101   }
1102 }
1103 
1104 Node* PhaseIdealLoop::update_skeleton_predicate(Node* iff, Node* value, Node* predicate, Node* uncommon_proj,
1105                                                 Node* current_proj, IdealLoopTree* outer_loop, Node* prev_proj) {
1106   bool clone = (outer_loop != NULL); // Clone the predicate?
1107   Node_Stack to_clone(2);
1108   to_clone.push(iff->in(1), 1);
1109   uint current = C->unique();
1110   Node* result = NULL;
1111   // Look for the opaque node to replace with the new value
1112   // and clone everything in between. We keep the Opaque4 node
1113   // so the duplicated predicates are eliminated once loop
1114   // opts are over: they are here only to keep the IR graph
1115   // consistent.
1116   do {
1117     Node* n = to_clone.node();
1118     uint i = to_clone.index();
1119     Node* m = n->in(i);
1120     int op = m->Opcode();
1121     if (m->is_Bool() ||
1122         m->is_Cmp() ||
1123         op == Op_AndL ||
1124         op == Op_OrL ||
1125         op == Op_RShiftL ||
1126         op == Op_LShiftL ||
1127         op == Op_AddL ||
1128         op == Op_AddI ||
1129         op == Op_MulL ||
1130         op == Op_MulI ||
1131         op == Op_SubL ||
1132         op == Op_SubI ||
1133         op == Op_ConvI2L) {
1134         to_clone.push(m, 1);
1135         continue;
1136     }
1137     if (op == Op_Opaque1) {
1138       if (!clone) {
1139         // Update the input of the Opaque1Node and exit
1140         _igvn.replace_input_of(m, 1, value);
1141         return prev_proj;
1142       }
1143       if (n->_idx < current) {
1144         n = n->clone();
1145       }
1146       n->set_req(i, value);
1147       register_new_node(n, current_proj);
1148       to_clone.set_node(n);
1149     }
1150     for (;;) {
1151       Node* cur = to_clone.node();
1152       uint j = to_clone.index();
1153       if (j+1 < cur->req()) {
1154         to_clone.set_index(j+1);
1155         break;
1156       }
1157       to_clone.pop();
1158       if (to_clone.size() == 0) {
1159         result = cur;
1160         break;
1161       }
1162       Node* next = to_clone.node();
1163       j = to_clone.index();
1164       if (clone && cur->_idx >= current) {
1165         if (next->_idx < current) {
1166           next = next->clone();
1167           register_new_node(next, current_proj);
1168           to_clone.set_node(next);
1169         }
1170         assert(next->in(j) != cur, "input should have been cloned");
1171         next->set_req(j, cur);
1172       }
1173     }
1174   } while (result == NULL);
1175   if (!clone) {
1176     return NULL;
1177   }
1178   assert(result->_idx >= current, "new node expected");
1179 
1180   Node* proj = predicate->clone();
1181   Node* other_proj = uncommon_proj->clone();
1182   Node* new_iff = iff->clone();
1183   new_iff->set_req(1, result);
1184   proj->set_req(0, new_iff);
1185   other_proj->set_req(0, new_iff);
1186   Node *frame = new ParmNode(C->start(), TypeFunc::FramePtr);
1187   register_new_node(frame, C->start());
1188   // It's impossible for the predicate to fail at runtime. Use an Halt node.
1189   Node* halt = new HaltNode(other_proj, frame);
1190   C->root()->add_req(halt);
1191   new_iff->set_req(0, prev_proj);
1192 
1193   register_control(new_iff, outer_loop->_parent, prev_proj);
1194   register_control(proj, outer_loop->_parent, new_iff);
1195   register_control(other_proj, _ltree_root, new_iff);
1196   register_control(halt, _ltree_root, other_proj);
1197   return proj;
1198 }
1199 
1200 void PhaseIdealLoop::duplicate_predicates(CountedLoopNode* pre_head, Node* castii, IdealLoopTree* outer_loop,
1201                                           LoopNode* outer_main_head, uint dd_main_head) {
1202   if (UseLoopPredicate) {
1203     Node* entry = pre_head->in(LoopNode::EntryControl);
1204     Node* predicate = NULL;
1205     predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
1206     if (predicate != NULL) {
1207       entry = skip_loop_predicates(entry);
1208     }
1209     Node* profile_predicate = NULL;
1210     if (UseProfiledLoopPredicate) {
1211       profile_predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
1212       if (profile_predicate != NULL) {
1213         entry = skip_loop_predicates(entry);
1214       }
1215     }
1216     predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
1217     duplicate_predicates_helper(predicate, castii, outer_loop, outer_main_head, dd_main_head);
1218     duplicate_predicates_helper(profile_predicate, castii, outer_loop, outer_main_head, dd_main_head);
1219   }
1220 }
1221 
1222 //------------------------------insert_pre_post_loops--------------------------
1223 // Insert pre and post loops.  If peel_only is set, the pre-loop can not have
1224 // more iterations added.  It acts as a 'peel' only, no lower-bound RCE, no
1225 // alignment.  Useful to unroll loops that do no array accesses.
1226 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
1227 
1228 #ifndef PRODUCT
1229   if (TraceLoopOpts) {
1230     if (peel_only)
1231       tty->print("PeelMainPost ");
1232     else
1233       tty->print("PreMainPost  ");
1234     loop->dump_head();
1235   }
1236 #endif
1237   C->set_major_progress();
1238 
1239   // Find common pieces of the loop being guarded with pre & post loops
1240   CountedLoopNode *main_head = loop->_head->as_CountedLoop();
1241   assert( main_head->is_normal_loop(), "" );
1242   CountedLoopEndNode *main_end = main_head->loopexit();
1243   assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
1244 
1245   Node *pre_header= main_head->in(LoopNode::EntryControl);
1246   Node *init      = main_head->init_trip();
1247   Node *incr      = main_end ->incr();
1248   Node *limit     = main_end ->limit();
1249   Node *stride    = main_end ->stride();
1250   Node *cmp       = main_end ->cmp_node();
1251   BoolTest::mask b_test = main_end->test_trip();
1252 
1253   // Need only 1 user of 'bol' because I will be hacking the loop bounds.
1254   Node *bol = main_end->in(CountedLoopEndNode::TestValue);
1255   if( bol->outcnt() != 1 ) {
1256     bol = bol->clone();
1257     register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
1258     _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, bol);
1259   }
1260   // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
1261   if( cmp->outcnt() != 1 ) {
1262     cmp = cmp->clone();
1263     register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
1264     _igvn.replace_input_of(bol, 1, cmp);
1265   }
1266 
1267   // Add the post loop
1268   CountedLoopNode *post_head = NULL;
1269   Node *main_exit = insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_head);
1270 
1271   //------------------------------
1272   // Step B: Create Pre-Loop.
1273 
1274   // Step B1: Clone the loop body.  The clone becomes the pre-loop.  The main
1275   // loop pre-header illegally has 2 control users (old & new loops).
1276   LoopNode* outer_main_head = main_head;
1277   IdealLoopTree* outer_loop = loop;
1278   if (main_head->is_strip_mined()) {
1279     main_head->verify_strip_mined(1);
1280     outer_main_head = main_head->outer_loop();
1281     outer_loop = loop->_parent;
1282     assert(outer_loop->_head == outer_main_head, "broken loop tree");
1283   }
1284   uint dd_main_head = dom_depth(outer_main_head);
1285   clone_loop(loop, old_new, dd_main_head, ControlAroundStripMined);
1286   CountedLoopNode*    pre_head = old_new[main_head->_idx]->as_CountedLoop();
1287   CountedLoopEndNode* pre_end  = old_new[main_end ->_idx]->as_CountedLoopEnd();
1288   pre_head->set_pre_loop(main_head);
1289   Node *pre_incr = old_new[incr->_idx];
1290 
1291   // Reduce the pre-loop trip count.
1292   pre_end->_prob = PROB_FAIR;
1293 
1294   // Find the pre-loop normal exit.
1295   Node* pre_exit = pre_end->proj_out(false);
1296   assert( pre_exit->Opcode() == Op_IfFalse, "" );
1297   IfFalseNode *new_pre_exit = new IfFalseNode(pre_end);
1298   _igvn.register_new_node_with_optimizer( new_pre_exit );
1299   set_idom(new_pre_exit, pre_end, dd_main_head);
1300   set_loop(new_pre_exit, outer_loop->_parent);
1301 
1302   // Step B2: Build a zero-trip guard for the main-loop.  After leaving the
1303   // pre-loop, the main-loop may not execute at all.  Later in life this
1304   // zero-trip guard will become the minimum-trip guard when we unroll
1305   // the main-loop.
1306   Node *min_opaq = new Opaque1Node(C, limit);
1307   Node *min_cmp  = new CmpINode( pre_incr, min_opaq );
1308   Node *min_bol  = new BoolNode( min_cmp, b_test );
1309   register_new_node( min_opaq, new_pre_exit );
1310   register_new_node( min_cmp , new_pre_exit );
1311   register_new_node( min_bol , new_pre_exit );
1312 
1313   // Build the IfNode (assume the main-loop is executed always).
1314   IfNode *min_iff = new IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
1315   _igvn.register_new_node_with_optimizer( min_iff );
1316   set_idom(min_iff, new_pre_exit, dd_main_head);
1317   set_loop(min_iff, outer_loop->_parent);
1318 
1319   // Plug in the false-path, taken if we need to skip main-loop
1320   _igvn.hash_delete( pre_exit );
1321   pre_exit->set_req(0, min_iff);
1322   set_idom(pre_exit, min_iff, dd_main_head);
1323   set_idom(pre_exit->unique_ctrl_out(), min_iff, dd_main_head);
1324   // Make the true-path, must enter the main loop
1325   Node *min_taken = new IfTrueNode( min_iff );
1326   _igvn.register_new_node_with_optimizer( min_taken );
1327   set_idom(min_taken, min_iff, dd_main_head);
1328   set_loop(min_taken, outer_loop->_parent);
1329   // Plug in the true path
1330   _igvn.hash_delete(outer_main_head);
1331   outer_main_head->set_req(LoopNode::EntryControl, min_taken);
1332   set_idom(outer_main_head, min_taken, dd_main_head);
1333 
1334   Arena *a = Thread::current()->resource_area();
1335   VectorSet visited(a);
1336   Node_Stack clones(a, main_head->back_control()->outcnt());
1337   // Step B3: Make the fall-in values to the main-loop come from the
1338   // fall-out values of the pre-loop.
1339   for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
1340     Node* main_phi = main_head->fast_out(i2);
1341     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
1342       Node *pre_phi = old_new[main_phi->_idx];
1343       Node *fallpre  = clone_up_backedge_goo(pre_head->back_control(),
1344                                              main_head->skip_strip_mined()->in(LoopNode::EntryControl),
1345                                              pre_phi->in(LoopNode::LoopBackControl),
1346                                              visited, clones);
1347       _igvn.hash_delete(main_phi);
1348       main_phi->set_req( LoopNode::EntryControl, fallpre );
1349     }
1350   }
1351 
1352   // Nodes inside the loop may be control dependent on a predicate
1353   // that was moved before the preloop. If the back branch of the main
1354   // or post loops becomes dead, those nodes won't be dependent on the
1355   // test that guards that loop nest anymore which could lead to an
1356   // incorrect array access because it executes independently of the
1357   // test that was guarding the loop nest. We add a special CastII on
1358   // the if branch that enters the loop, between the input induction
1359   // variable value and the induction variable Phi to preserve correct
1360   // dependencies.
1361 
1362   // CastII for the main loop:
1363   Node* castii = cast_incr_before_loop( pre_incr, min_taken, main_head );
1364   assert(castii != NULL, "no castII inserted");
1365   duplicate_predicates(pre_head, castii, outer_loop, outer_main_head, dd_main_head);
1366 
1367   // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1368   // RCE and alignment may change this later.
1369   Node *cmp_end = pre_end->cmp_node();
1370   assert( cmp_end->in(2) == limit, "" );
1371   Node *pre_limit = new AddINode( init, stride );
1372 
1373   // Save the original loop limit in this Opaque1 node for
1374   // use by range check elimination.
1375   Node *pre_opaq  = new Opaque1Node(C, pre_limit, limit);
1376 
1377   register_new_node( pre_limit, pre_head->in(0) );
1378   register_new_node( pre_opaq , pre_head->in(0) );
1379 
1380   // Since no other users of pre-loop compare, I can hack limit directly
1381   assert( cmp_end->outcnt() == 1, "no other users" );
1382   _igvn.hash_delete(cmp_end);
1383   cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
1384 
1385   // Special case for not-equal loop bounds:
1386   // Change pre loop test, main loop test, and the
1387   // main loop guard test to use lt or gt depending on stride
1388   // direction:
1389   // positive stride use <
1390   // negative stride use >
1391   //
1392   // not-equal test is kept for post loop to handle case
1393   // when init > limit when stride > 0 (and reverse).
1394 
1395   if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
1396 
1397     BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
1398     // Modify pre loop end condition
1399     Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1400     BoolNode* new_bol0 = new BoolNode(pre_bol->in(1), new_test);
1401     register_new_node( new_bol0, pre_head->in(0) );
1402     _igvn.replace_input_of(pre_end, CountedLoopEndNode::TestValue, new_bol0);
1403     // Modify main loop guard condition
1404     assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
1405     BoolNode* new_bol1 = new BoolNode(min_bol->in(1), new_test);
1406     register_new_node( new_bol1, new_pre_exit );
1407     _igvn.hash_delete(min_iff);
1408     min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
1409     // Modify main loop end condition
1410     BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1411     BoolNode* new_bol2 = new BoolNode(main_bol->in(1), new_test);
1412     register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
1413     _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, new_bol2);
1414   }
1415 
1416   // Flag main loop
1417   main_head->set_main_loop();
1418   if( peel_only ) main_head->set_main_no_pre_loop();
1419 
1420   // Subtract a trip count for the pre-loop.
1421   main_head->set_trip_count(main_head->trip_count() - 1);
1422 
1423   // It's difficult to be precise about the trip-counts
1424   // for the pre/post loops.  They are usually very short,
1425   // so guess that 4 trips is a reasonable value.
1426   post_head->set_profile_trip_cnt(4.0);
1427   pre_head->set_profile_trip_cnt(4.0);
1428 
1429   // Now force out all loop-invariant dominating tests.  The optimizer
1430   // finds some, but we _know_ they are all useless.
1431   peeled_dom_test_elim(loop,old_new);
1432   loop->record_for_igvn();
1433 }
1434 
1435 //------------------------------insert_vector_post_loop------------------------
1436 // Insert a copy of the atomic unrolled vectorized main loop as a post loop,
1437 // unroll_policy has already informed us that more unrolling is about to happen to
1438 // the main loop.  The resultant post loop will serve as a vectorized drain loop.
1439 void PhaseIdealLoop::insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new) {
1440   if (!loop->_head->is_CountedLoop()) return;
1441 
1442   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1443 
1444   // only process vectorized main loops
1445   if (!cl->is_vectorized_loop() || !cl->is_main_loop()) return;
1446 
1447   int slp_max_unroll_factor = cl->slp_max_unroll();
1448   int cur_unroll = cl->unrolled_count();
1449 
1450   if (slp_max_unroll_factor == 0) return;
1451 
1452   // only process atomic unroll vector loops (not super unrolled after vectorization)
1453   if (cur_unroll != slp_max_unroll_factor) return;
1454 
1455   // we only ever process this one time
1456   if (cl->has_atomic_post_loop()) return;
1457 
1458 #ifndef PRODUCT
1459   if (TraceLoopOpts) {
1460     tty->print("PostVector  ");
1461     loop->dump_head();
1462   }
1463 #endif
1464   C->set_major_progress();
1465 
1466   // Find common pieces of the loop being guarded with pre & post loops
1467   CountedLoopNode *main_head = loop->_head->as_CountedLoop();
1468   CountedLoopEndNode *main_end = main_head->loopexit();
1469   // diagnostic to show loop end is not properly formed
1470   assert(main_end->outcnt() == 2, "1 true, 1 false path only");
1471 
1472   // mark this loop as processed
1473   main_head->mark_has_atomic_post_loop();
1474 
1475   Node *incr = main_end->incr();
1476   Node *limit = main_end->limit();
1477 
1478   // In this case we throw away the result as we are not using it to connect anything else.
1479   CountedLoopNode *post_head = NULL;
1480   insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_head);
1481 
1482   // It's difficult to be precise about the trip-counts
1483   // for post loops.  They are usually very short,
1484   // so guess that unit vector trips is a reasonable value.
1485   post_head->set_profile_trip_cnt(cur_unroll);
1486 
1487   // Now force out all loop-invariant dominating tests.  The optimizer
1488   // finds some, but we _know_ they are all useless.
1489   peeled_dom_test_elim(loop, old_new);
1490   loop->record_for_igvn();
1491 }
1492 
1493 
1494 //-------------------------insert_scalar_rced_post_loop------------------------
1495 // Insert a copy of the rce'd main loop as a post loop,
1496 // We have not unrolled the main loop, so this is the right time to inject this.
1497 // Later we will examine the partner of this post loop pair which still has range checks
1498 // to see inject code which tests at runtime if the range checks are applicable.
1499 void PhaseIdealLoop::insert_scalar_rced_post_loop(IdealLoopTree *loop, Node_List &old_new) {
1500   if (!loop->_head->is_CountedLoop()) return;
1501 
1502   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1503 
1504   // only process RCE'd main loops
1505   if (!cl->is_main_loop() || cl->range_checks_present()) return;
1506 
1507 #ifndef PRODUCT
1508   if (TraceLoopOpts) {
1509     tty->print("PostScalarRce  ");
1510     loop->dump_head();
1511   }
1512 #endif
1513   C->set_major_progress();
1514 
1515   // Find common pieces of the loop being guarded with pre & post loops
1516   CountedLoopNode *main_head = loop->_head->as_CountedLoop();
1517   CountedLoopEndNode *main_end = main_head->loopexit();
1518   // diagnostic to show loop end is not properly formed
1519   assert(main_end->outcnt() == 2, "1 true, 1 false path only");
1520 
1521   Node *incr = main_end->incr();
1522   Node *limit = main_end->limit();
1523 
1524   // In this case we throw away the result as we are not using it to connect anything else.
1525   CountedLoopNode *post_head = NULL;
1526   insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_head);
1527 
1528   // It's difficult to be precise about the trip-counts
1529   // for post loops.  They are usually very short,
1530   // so guess that unit vector trips is a reasonable value.
1531   post_head->set_profile_trip_cnt(4.0);
1532   post_head->set_is_rce_post_loop();
1533 
1534   // Now force out all loop-invariant dominating tests.  The optimizer
1535   // finds some, but we _know_ they are all useless.
1536   peeled_dom_test_elim(loop, old_new);
1537   loop->record_for_igvn();
1538 }
1539 
1540 
1541 //------------------------------insert_post_loop-------------------------------
1542 // Insert post loops.  Add a post loop to the given loop passed.
1543 Node *PhaseIdealLoop::insert_post_loop(IdealLoopTree *loop, Node_List &old_new,
1544                                        CountedLoopNode *main_head, CountedLoopEndNode *main_end,
1545                                        Node *incr, Node *limit, CountedLoopNode *&post_head) {
1546   IfNode* outer_main_end = main_end;
1547   IdealLoopTree* outer_loop = loop;
1548   if (main_head->is_strip_mined()) {
1549     main_head->verify_strip_mined(1);
1550     outer_main_end = main_head->outer_loop_end();
1551     outer_loop = loop->_parent;
1552     assert(outer_loop->_head == main_head->in(LoopNode::EntryControl), "broken loop tree");
1553   }
1554 
1555   //------------------------------
1556   // Step A: Create a new post-Loop.
1557   Node* main_exit = outer_main_end->proj_out(false);
1558   assert(main_exit->Opcode() == Op_IfFalse, "");
1559   int dd_main_exit = dom_depth(main_exit);
1560 
1561   // Step A1: Clone the loop body of main. The clone becomes the post-loop.
1562   // The main loop pre-header illegally has 2 control users (old & new loops).
1563   clone_loop(loop, old_new, dd_main_exit, ControlAroundStripMined);
1564   assert(old_new[main_end->_idx]->Opcode() == Op_CountedLoopEnd, "");
1565   post_head = old_new[main_head->_idx]->as_CountedLoop();
1566   post_head->set_normal_loop();
1567   post_head->set_post_loop(main_head);
1568 
1569   // Reduce the post-loop trip count.
1570   CountedLoopEndNode* post_end = old_new[main_end->_idx]->as_CountedLoopEnd();
1571   post_end->_prob = PROB_FAIR;
1572 
1573   // Build the main-loop normal exit.
1574   IfFalseNode *new_main_exit = new IfFalseNode(outer_main_end);
1575   _igvn.register_new_node_with_optimizer(new_main_exit);
1576   set_idom(new_main_exit, outer_main_end, dd_main_exit);
1577   set_loop(new_main_exit, outer_loop->_parent);
1578 
1579   // Step A2: Build a zero-trip guard for the post-loop.  After leaving the
1580   // main-loop, the post-loop may not execute at all.  We 'opaque' the incr
1581   // (the previous loop trip-counter exit value) because we will be changing
1582   // the exit value (via additional unrolling) so we cannot constant-fold away the zero
1583   // trip guard until all unrolling is done.
1584   Node *zer_opaq = new Opaque1Node(C, incr);
1585   Node *zer_cmp = new CmpINode(zer_opaq, limit);
1586   Node *zer_bol = new BoolNode(zer_cmp, main_end->test_trip());
1587   register_new_node(zer_opaq, new_main_exit);
1588   register_new_node(zer_cmp, new_main_exit);
1589   register_new_node(zer_bol, new_main_exit);
1590 
1591   // Build the IfNode
1592   IfNode *zer_iff = new IfNode(new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN);
1593   _igvn.register_new_node_with_optimizer(zer_iff);
1594   set_idom(zer_iff, new_main_exit, dd_main_exit);
1595   set_loop(zer_iff, outer_loop->_parent);
1596 
1597   // Plug in the false-path, taken if we need to skip this post-loop
1598   _igvn.replace_input_of(main_exit, 0, zer_iff);
1599   set_idom(main_exit, zer_iff, dd_main_exit);
1600   set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
1601   // Make the true-path, must enter this post loop
1602   Node *zer_taken = new IfTrueNode(zer_iff);
1603   _igvn.register_new_node_with_optimizer(zer_taken);
1604   set_idom(zer_taken, zer_iff, dd_main_exit);
1605   set_loop(zer_taken, outer_loop->_parent);
1606   // Plug in the true path
1607   _igvn.hash_delete(post_head);
1608   post_head->set_req(LoopNode::EntryControl, zer_taken);
1609   set_idom(post_head, zer_taken, dd_main_exit);
1610 
1611   Arena *a = Thread::current()->resource_area();
1612   VectorSet visited(a);
1613   Node_Stack clones(a, main_head->back_control()->outcnt());
1614   // Step A3: Make the fall-in values to the post-loop come from the
1615   // fall-out values of the main-loop.
1616   for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
1617     Node* main_phi = main_head->fast_out(i);
1618     if (main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0) {
1619       Node *cur_phi = old_new[main_phi->_idx];
1620       Node *fallnew = clone_up_backedge_goo(main_head->back_control(),
1621                                             post_head->init_control(),
1622                                             main_phi->in(LoopNode::LoopBackControl),
1623                                             visited, clones);
1624       _igvn.hash_delete(cur_phi);
1625       cur_phi->set_req(LoopNode::EntryControl, fallnew);
1626     }
1627   }
1628 
1629   // CastII for the new post loop:
1630   Node* castii = cast_incr_before_loop(zer_opaq->in(1), zer_taken, post_head);
1631   assert(castii != NULL, "no castII inserted");
1632 
1633   return new_main_exit;
1634 }
1635 
1636 //------------------------------is_invariant-----------------------------
1637 // Return true if n is invariant
1638 bool IdealLoopTree::is_invariant(Node* n) const {
1639   Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
1640   if (n_c->is_top()) return false;
1641   return !is_member(_phase->get_loop(n_c));
1642 }
1643 
1644 
1645 //------------------------------do_unroll--------------------------------------
1646 // Unroll the loop body one step - make each trip do 2 iterations.
1647 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
1648   assert(LoopUnrollLimit, "");
1649   CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
1650   CountedLoopEndNode *loop_end = loop_head->loopexit();
1651 #ifndef PRODUCT
1652   if (PrintOpto && VerifyLoopOptimizations) {
1653     tty->print("Unrolling ");
1654     loop->dump_head();
1655   } else if (TraceLoopOpts) {
1656     if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
1657       tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
1658     } else {
1659       tty->print("Unroll %d     ", loop_head->unrolled_count()*2);
1660     }
1661     loop->dump_head();
1662   }
1663 
1664   if (C->do_vector_loop() && (PrintOpto && (VerifyLoopOptimizations || TraceLoopOpts))) {
1665     Arena* arena = Thread::current()->resource_area();
1666     Node_Stack stack(arena, C->live_nodes() >> 2);
1667     Node_List rpo_list;
1668     VectorSet visited(arena);
1669     visited.set(loop_head->_idx);
1670     rpo( loop_head, stack, visited, rpo_list );
1671     dump(loop, rpo_list.size(), rpo_list );
1672   }
1673 #endif
1674 
1675   // Remember loop node count before unrolling to detect
1676   // if rounds of unroll,optimize are making progress
1677   loop_head->set_node_count_before_unroll(loop->_body.size());
1678 
1679   Node *ctrl  = loop_head->skip_strip_mined()->in(LoopNode::EntryControl);
1680   Node *limit = loop_head->limit();
1681   Node *init  = loop_head->init_trip();
1682   Node *stride = loop_head->stride();
1683 
1684   Node *opaq = NULL;
1685   if (adjust_min_trip) {       // If not maximally unrolling, need adjustment
1686     // Search for zero-trip guard.
1687 
1688     // Check the shape of the graph at the loop entry. If an inappropriate
1689     // graph shape is encountered, the compiler bails out loop unrolling;
1690     // compilation of the method will still succeed.
1691     if (!is_canonical_loop_entry(loop_head)) {
1692       return;
1693     }
1694     opaq = loop_head->skip_predicates()->in(0)->in(1)->in(1)->in(2);
1695     // Zero-trip test uses an 'opaque' node which is not shared.
1696     assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
1697   }
1698 
1699   C->set_major_progress();
1700 
1701   Node* new_limit = NULL;
1702   int stride_con = stride->get_int();
1703   int stride_p = (stride_con > 0) ? stride_con : -stride_con;
1704   uint old_trip_count = loop_head->trip_count();
1705   // Verify that unroll policy result is still valid.
1706   assert(old_trip_count > 1 &&
1707       (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity");
1708 
1709   if (UseLoopPredicate) {
1710     // Search for skeleton predicates and update them according to the new stride
1711     Node* entry = ctrl;
1712     while (entry != NULL && entry->is_Proj() && entry->in(0)->is_If()) {
1713       IfNode* iff = entry->in(0)->as_If();
1714       ProjNode* proj = iff->proj_out(1 - entry->as_Proj()->_con);
1715       if (proj->unique_ctrl_out()->Opcode() != Op_Halt) {
1716         break;
1717       }
1718       if (iff->in(1)->Opcode() == Op_Opaque4) {
1719         // Compute the value of the loop induction variable at the end of the
1720         // first iteration of the unrolled loop: init + new_stride_con - init_inc
1721         int init_inc = stride_con/loop_head->unrolled_count();
1722         assert(init_inc != 0, "invalid loop increment");
1723         int new_stride_con = stride_con * 2;
1724         Node* max_value = _igvn.intcon(new_stride_con - init_inc);
1725         max_value = new AddINode(init, max_value);
1726         register_new_node(max_value, get_ctrl(iff->in(1)));
1727         update_skeleton_predicate(iff, max_value);
1728       }
1729       entry = entry->in(0)->in(0);
1730     }
1731   }
1732 
1733   // Adjust loop limit to keep valid iterations number after unroll.
1734   // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
1735   // which may overflow.
1736   if (!adjust_min_trip) {
1737     assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
1738         "odd trip count for maximally unroll");
1739     // Don't need to adjust limit for maximally unroll since trip count is even.
1740   } else if (loop_head->has_exact_trip_count() && init->is_Con()) {
1741     // Loop's limit is constant. Loop's init could be constant when pre-loop
1742     // become peeled iteration.
1743     jlong init_con = init->get_int();
1744     // We can keep old loop limit if iterations count stays the same:
1745     //   old_trip_count == new_trip_count * 2
1746     // Note: since old_trip_count >= 2 then new_trip_count >= 1
1747     // so we also don't need to adjust zero trip test.
1748     jlong limit_con  = limit->get_int();
1749     // (stride_con*2) not overflow since stride_con <= 8.
1750     int new_stride_con = stride_con * 2;
1751     int stride_m    = new_stride_con - (stride_con > 0 ? 1 : -1);
1752     jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con;
1753     // New trip count should satisfy next conditions.
1754     assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
1755     uint new_trip_count = (uint)trip_count;
1756     adjust_min_trip = (old_trip_count != new_trip_count*2);
1757   }
1758 
1759   if (adjust_min_trip) {
1760     // Step 2: Adjust the trip limit if it is called for.
1761     // The adjustment amount is -stride. Need to make sure if the
1762     // adjustment underflows or overflows, then the main loop is skipped.
1763     Node* cmp = loop_end->cmp_node();
1764     assert(cmp->in(2) == limit, "sanity");
1765     assert(opaq != NULL && opaq->in(1) == limit, "sanity");
1766 
1767     // Verify that policy_unroll result is still valid.
1768     const TypeInt* limit_type = _igvn.type(limit)->is_int();
1769     assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) ||
1770         stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity");
1771 
1772     if (limit->is_Con()) {
1773       // The check in policy_unroll and the assert above guarantee
1774       // no underflow if limit is constant.
1775       new_limit = _igvn.intcon(limit->get_int() - stride_con);
1776       set_ctrl(new_limit, C->root());
1777     } else {
1778       // Limit is not constant.
1779       if (loop_head->unrolled_count() == 1) { // only for first unroll
1780         // Separate limit by Opaque node in case it is an incremented
1781         // variable from previous loop to avoid using pre-incremented
1782         // value which could increase register pressure.
1783         // Otherwise reorg_offsets() optimization will create a separate
1784         // Opaque node for each use of trip-counter and as result
1785         // zero trip guard limit will be different from loop limit.
1786         assert(has_ctrl(opaq), "should have it");
1787         Node* opaq_ctrl = get_ctrl(opaq);
1788         limit = new Opaque2Node( C, limit );
1789         register_new_node( limit, opaq_ctrl );
1790       }
1791       if ((stride_con > 0 && (java_subtract(limit_type->_lo, stride_con) < limit_type->_lo)) ||
1792           (stride_con < 0 && (java_subtract(limit_type->_hi, stride_con) > limit_type->_hi))) {
1793         // No underflow.
1794         new_limit = new SubINode(limit, stride);
1795       } else {
1796         // (limit - stride) may underflow.
1797         // Clamp the adjustment value with MININT or MAXINT:
1798         //
1799         //   new_limit = limit-stride
1800         //   if (stride > 0)
1801         //     new_limit = (limit < new_limit) ? MININT : new_limit;
1802         //   else
1803         //     new_limit = (limit > new_limit) ? MAXINT : new_limit;
1804         //
1805         BoolTest::mask bt = loop_end->test_trip();
1806         assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
1807         Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint);
1808         set_ctrl(adj_max, C->root());
1809         Node* old_limit = NULL;
1810         Node* adj_limit = NULL;
1811         Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL;
1812         if (loop_head->unrolled_count() > 1 &&
1813             limit->is_CMove() && limit->Opcode() == Op_CMoveI &&
1814             limit->in(CMoveNode::IfTrue) == adj_max &&
1815             bol->as_Bool()->_test._test == bt &&
1816             bol->in(1)->Opcode() == Op_CmpI &&
1817             bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) {
1818           // Loop was unrolled before.
1819           // Optimize the limit to avoid nested CMove:
1820           // use original limit as old limit.
1821           old_limit = bol->in(1)->in(1);
1822           // Adjust previous adjusted limit.
1823           adj_limit = limit->in(CMoveNode::IfFalse);
1824           adj_limit = new SubINode(adj_limit, stride);
1825         } else {
1826           old_limit = limit;
1827           adj_limit = new SubINode(limit, stride);
1828         }
1829         assert(old_limit != NULL && adj_limit != NULL, "");
1830         register_new_node( adj_limit, ctrl ); // adjust amount
1831         Node* adj_cmp = new CmpINode(old_limit, adj_limit);
1832         register_new_node( adj_cmp, ctrl );
1833         Node* adj_bool = new BoolNode(adj_cmp, bt);
1834         register_new_node( adj_bool, ctrl );
1835         new_limit = new CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT);
1836       }
1837       register_new_node(new_limit, ctrl);
1838     }
1839     assert(new_limit != NULL, "");
1840     // Replace in loop test.
1841     assert(loop_end->in(1)->in(1) == cmp, "sanity");
1842     if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
1843       // Don't need to create new test since only one user.
1844       _igvn.hash_delete(cmp);
1845       cmp->set_req(2, new_limit);
1846     } else {
1847       // Create new test since it is shared.
1848       Node* ctrl2 = loop_end->in(0);
1849       Node* cmp2  = cmp->clone();
1850       cmp2->set_req(2, new_limit);
1851       register_new_node(cmp2, ctrl2);
1852       Node* bol2 = loop_end->in(1)->clone();
1853       bol2->set_req(1, cmp2);
1854       register_new_node(bol2, ctrl2);
1855       _igvn.replace_input_of(loop_end, 1, bol2);
1856     }
1857     // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1858     // Make it a 1-trip test (means at least 2 trips).
1859 
1860     // Guard test uses an 'opaque' node which is not shared.  Hence I
1861     // can edit it's inputs directly.  Hammer in the new limit for the
1862     // minimum-trip guard.
1863     assert(opaq->outcnt() == 1, "");
1864     _igvn.replace_input_of(opaq, 1, new_limit);
1865   }
1866 
1867   // Adjust max trip count. The trip count is intentionally rounded
1868   // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1869   // the main, unrolled, part of the loop will never execute as it is protected
1870   // by the min-trip test.  See bug 4834191 for a case where we over-unrolled
1871   // and later determined that part of the unrolled loop was dead.
1872   loop_head->set_trip_count(old_trip_count / 2);
1873 
1874   // Double the count of original iterations in the unrolled loop body.
1875   loop_head->double_unrolled_count();
1876 
1877   // ---------
1878   // Step 4: Clone the loop body.  Move it inside the loop.  This loop body
1879   // represents the odd iterations; since the loop trips an even number of
1880   // times its backedge is never taken.  Kill the backedge.
1881   uint dd = dom_depth(loop_head);
1882   clone_loop(loop, old_new, dd, IgnoreStripMined);
1883 
1884   // Make backedges of the clone equal to backedges of the original.
1885   // Make the fall-in from the original come from the fall-out of the clone.
1886   for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1887     Node* phi = loop_head->fast_out(j);
1888     if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1889       Node *newphi = old_new[phi->_idx];
1890       _igvn.hash_delete( phi );
1891       _igvn.hash_delete( newphi );
1892 
1893       phi   ->set_req(LoopNode::   EntryControl, newphi->in(LoopNode::LoopBackControl));
1894       newphi->set_req(LoopNode::LoopBackControl, phi   ->in(LoopNode::LoopBackControl));
1895       phi   ->set_req(LoopNode::LoopBackControl, C->top());
1896     }
1897   }
1898   Node *clone_head = old_new[loop_head->_idx];
1899   _igvn.hash_delete( clone_head );
1900   loop_head ->set_req(LoopNode::   EntryControl, clone_head->in(LoopNode::LoopBackControl));
1901   clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1902   loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1903   loop->_head = clone_head;     // New loop header
1904 
1905   set_idom(loop_head,  loop_head ->in(LoopNode::EntryControl), dd);
1906   set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1907 
1908   // Kill the clone's backedge
1909   Node *newcle = old_new[loop_end->_idx];
1910   _igvn.hash_delete( newcle );
1911   Node *one = _igvn.intcon(1);
1912   set_ctrl(one, C->root());
1913   newcle->set_req(1, one);
1914   // Force clone into same loop body
1915   uint max = loop->_body.size();
1916   for( uint k = 0; k < max; k++ ) {
1917     Node *old = loop->_body.at(k);
1918     Node *nnn = old_new[old->_idx];
1919     loop->_body.push(nnn);
1920     if (!has_ctrl(old))
1921       set_loop(nnn, loop);
1922   }
1923 
1924   loop->record_for_igvn();
1925   loop_head->clear_strip_mined();
1926 
1927 #ifndef PRODUCT
1928   if (C->do_vector_loop() && (PrintOpto && (VerifyLoopOptimizations || TraceLoopOpts))) {
1929     tty->print("\nnew loop after unroll\n");       loop->dump_head();
1930     for (uint i = 0; i < loop->_body.size(); i++) {
1931       loop->_body.at(i)->dump();
1932     }
1933     if(C->clone_map().is_debug()) {
1934       tty->print("\nCloneMap\n");
1935       Dict* dict = C->clone_map().dict();
1936       DictI i(dict);
1937       tty->print_cr("Dict@%p[%d] = ", dict, dict->Size());
1938       for (int ii = 0; i.test(); ++i, ++ii) {
1939         NodeCloneInfo cl((uint64_t)dict->operator[]((void*)i._key));
1940         tty->print("%d->%d:%d,", (int)(intptr_t)i._key, cl.idx(), cl.gen());
1941         if (ii % 10 == 9) {
1942           tty->print_cr(" ");
1943         }
1944       }
1945       tty->print_cr(" ");
1946     }
1947   }
1948 #endif
1949 
1950 }
1951 
1952 //------------------------------do_maximally_unroll----------------------------
1953 
1954 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1955   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1956   assert(cl->has_exact_trip_count(), "trip count is not exact");
1957   assert(cl->trip_count() > 0, "");
1958 #ifndef PRODUCT
1959   if (TraceLoopOpts) {
1960     tty->print("MaxUnroll  %d ", cl->trip_count());
1961     loop->dump_head();
1962   }
1963 #endif
1964 
1965   // If loop is tripping an odd number of times, peel odd iteration
1966   if ((cl->trip_count() & 1) == 1) {
1967     do_peeling(loop, old_new);
1968   }
1969 
1970   // Now its tripping an even number of times remaining.  Double loop body.
1971   // Do not adjust pre-guards; they are not needed and do not exist.
1972   if (cl->trip_count() > 0) {
1973     assert((cl->trip_count() & 1) == 0, "missed peeling");
1974     do_unroll(loop, old_new, false);
1975   }
1976 }
1977 
1978 void PhaseIdealLoop::mark_reductions(IdealLoopTree *loop) {
1979   if (SuperWordReductions == false) return;
1980 
1981   CountedLoopNode* loop_head = loop->_head->as_CountedLoop();
1982   if (loop_head->unrolled_count() > 1) {
1983     return;
1984   }
1985 
1986   Node* trip_phi = loop_head->phi();
1987   for (DUIterator_Fast imax, i = loop_head->fast_outs(imax); i < imax; i++) {
1988     Node* phi = loop_head->fast_out(i);
1989     if (phi->is_Phi() && phi->outcnt() > 0 && phi != trip_phi) {
1990       // For definitions which are loop inclusive and not tripcounts.
1991       Node* def_node = phi->in(LoopNode::LoopBackControl);
1992 
1993       if (def_node != NULL) {
1994         Node* n_ctrl = get_ctrl(def_node);
1995         if (n_ctrl != NULL && loop->is_member(get_loop(n_ctrl))) {
1996           // Now test it to see if it fits the standard pattern for a reduction operator.
1997           int opc = def_node->Opcode();
1998           if (opc != ReductionNode::opcode(opc, def_node->bottom_type()->basic_type())) {
1999             if (!def_node->is_reduction()) { // Not marked yet
2000               // To be a reduction, the arithmetic node must have the phi as input and provide a def to it
2001               bool ok = false;
2002               for (unsigned j = 1; j < def_node->req(); j++) {
2003                 Node* in = def_node->in(j);
2004                 if (in == phi) {
2005                   ok = true;
2006                   break;
2007                 }
2008               }
2009 
2010               // do nothing if we did not match the initial criteria
2011               if (ok == false) {
2012                 continue;
2013               }
2014 
2015               // The result of the reduction must not be used in the loop
2016               for (DUIterator_Fast imax, i = def_node->fast_outs(imax); i < imax && ok; i++) {
2017                 Node* u = def_node->fast_out(i);
2018                 if (!loop->is_member(get_loop(ctrl_or_self(u)))) {
2019                   continue;
2020                 }
2021                 if (u == phi) {
2022                   continue;
2023                 }
2024                 ok = false;
2025               }
2026 
2027               // iff the uses conform
2028               if (ok) {
2029                 def_node->add_flag(Node::Flag_is_reduction);
2030                 loop_head->mark_has_reductions();
2031               }
2032             }
2033           }
2034         }
2035       }
2036     }
2037   }
2038 }
2039 
2040 //------------------------------adjust_limit-----------------------------------
2041 // Helper function for add_constraint().
2042 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl, bool round_up) {
2043   // Compute "I :: (limit-offset)/scale"
2044   Node *con = new SubINode(rc_limit, offset);
2045   register_new_node(con, pre_ctrl);
2046   Node *X = new DivINode(0, con, scale);
2047   register_new_node(X, pre_ctrl);
2048 
2049   // When the absolute value of scale is greater than one, the integer
2050   // division may round limit down so add one to the limit.
2051   if (round_up) {
2052     X = new AddINode(X, _igvn.intcon(1));
2053     register_new_node(X, pre_ctrl);
2054   }
2055 
2056   // Adjust loop limit
2057   loop_limit = (stride_con > 0)
2058                ? (Node*)(new MinINode(loop_limit, X))
2059                : (Node*)(new MaxINode(loop_limit, X));
2060   register_new_node(loop_limit, pre_ctrl);
2061   return loop_limit;
2062 }
2063 
2064 //------------------------------add_constraint---------------------------------
2065 // Constrain the main loop iterations so the conditions:
2066 //    low_limit <= scale_con * I + offset  <  upper_limit
2067 // always holds true.  That is, either increase the number of iterations in
2068 // the pre-loop or the post-loop until the condition holds true in the main
2069 // loop.  Stride, scale, offset and limit are all loop invariant.  Further,
2070 // stride and scale are constants (offset and limit often are).
2071 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 ) {
2072   // For positive stride, the pre-loop limit always uses a MAX function
2073   // and the main loop a MIN function.  For negative stride these are
2074   // reversed.
2075 
2076   // Also for positive stride*scale the affine function is increasing, so the
2077   // pre-loop must check for underflow and the post-loop for overflow.
2078   // Negative stride*scale reverses this; pre-loop checks for overflow and
2079   // post-loop for underflow.
2080 
2081   Node *scale = _igvn.intcon(scale_con);
2082   set_ctrl(scale, C->root());
2083 
2084   if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
2085     // The overflow limit: scale*I+offset < upper_limit
2086     // For main-loop compute
2087     //   ( if (scale > 0) /* and stride > 0 */
2088     //       I < (upper_limit-offset)/scale
2089     //     else /* scale < 0 and stride < 0 */
2090     //       I > (upper_limit-offset)/scale
2091     //   )
2092     //
2093     // (upper_limit-offset) may overflow or underflow.
2094     // But it is fine since main loop will either have
2095     // less iterations or will be skipped in such case.
2096     *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl, false);
2097 
2098     // The underflow limit: low_limit <= scale*I+offset.
2099     // For pre-loop compute
2100     //   NOT(scale*I+offset >= low_limit)
2101     //   scale*I+offset < low_limit
2102     //   ( if (scale > 0) /* and stride > 0 */
2103     //       I < (low_limit-offset)/scale
2104     //     else /* scale < 0 and stride < 0 */
2105     //       I > (low_limit-offset)/scale
2106     //   )
2107 
2108     if (low_limit->get_int() == -max_jint) {
2109       // We need this guard when scale*pre_limit+offset >= limit
2110       // due to underflow. So we need execute pre-loop until
2111       // scale*I+offset >= min_int. But (min_int-offset) will
2112       // underflow when offset > 0 and X will be > original_limit
2113       // when stride > 0. To avoid it we replace positive offset with 0.
2114       //
2115       // Also (min_int+1 == -max_int) is used instead of min_int here
2116       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
2117       Node* shift = _igvn.intcon(31);
2118       set_ctrl(shift, C->root());
2119       Node* sign = new RShiftINode(offset, shift);
2120       register_new_node(sign, pre_ctrl);
2121       offset = new AndINode(offset, sign);
2122       register_new_node(offset, pre_ctrl);
2123     } else {
2124       assert(low_limit->get_int() == 0, "wrong low limit for range check");
2125       // The only problem we have here when offset == min_int
2126       // since (0-min_int) == min_int. It may be fine for stride > 0
2127       // but for stride < 0 X will be < original_limit. To avoid it
2128       // max(pre_limit, original_limit) is used in do_range_check().
2129     }
2130     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
2131     *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl,
2132                               scale_con > 1 && stride_con > 0);
2133 
2134   } else { // stride_con*scale_con < 0
2135     // For negative stride*scale pre-loop checks for overflow and
2136     // post-loop for underflow.
2137     //
2138     // The overflow limit: scale*I+offset < upper_limit
2139     // For pre-loop compute
2140     //   NOT(scale*I+offset < upper_limit)
2141     //   scale*I+offset >= upper_limit
2142     //   scale*I+offset+1 > upper_limit
2143     //   ( if (scale < 0) /* and stride > 0 */
2144     //       I < (upper_limit-(offset+1))/scale
2145     //     else /* scale > 0 and stride < 0 */
2146     //       I > (upper_limit-(offset+1))/scale
2147     //   )
2148     //
2149     // (upper_limit-offset-1) may underflow or overflow.
2150     // To avoid it min(pre_limit, original_limit) is used
2151     // in do_range_check() for stride > 0 and max() for < 0.
2152     Node *one  = _igvn.intcon(1);
2153     set_ctrl(one, C->root());
2154 
2155     Node *plus_one = new AddINode(offset, one);
2156     register_new_node( plus_one, pre_ctrl );
2157     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
2158     *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl,
2159                               scale_con < -1 && stride_con > 0);
2160 
2161     if (low_limit->get_int() == -max_jint) {
2162       // We need this guard when scale*main_limit+offset >= limit
2163       // due to underflow. So we need execute main-loop while
2164       // scale*I+offset+1 > min_int. But (min_int-offset-1) will
2165       // underflow when (offset+1) > 0 and X will be < main_limit
2166       // when scale < 0 (and stride > 0). To avoid it we replace
2167       // positive (offset+1) with 0.
2168       //
2169       // Also (min_int+1 == -max_int) is used instead of min_int here
2170       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
2171       Node* shift = _igvn.intcon(31);
2172       set_ctrl(shift, C->root());
2173       Node* sign = new RShiftINode(plus_one, shift);
2174       register_new_node(sign, pre_ctrl);
2175       plus_one = new AndINode(plus_one, sign);
2176       register_new_node(plus_one, pre_ctrl);
2177     } else {
2178       assert(low_limit->get_int() == 0, "wrong low limit for range check");
2179       // The only problem we have here when offset == max_int
2180       // since (max_int+1) == min_int and (0-min_int) == min_int.
2181       // But it is fine since main loop will either have
2182       // less iterations or will be skipped in such case.
2183     }
2184     // The underflow limit: low_limit <= scale*I+offset.
2185     // For main-loop compute
2186     //   scale*I+offset+1 > low_limit
2187     //   ( if (scale < 0) /* and stride > 0 */
2188     //       I < (low_limit-(offset+1))/scale
2189     //     else /* scale > 0 and stride < 0 */
2190     //       I > (low_limit-(offset+1))/scale
2191     //   )
2192 
2193     *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl,
2194                                false);
2195   }
2196 }
2197 
2198 
2199 //------------------------------is_scaled_iv---------------------------------
2200 // Return true if exp is a constant times an induction var
2201 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
2202   if (exp == iv) {
2203     if (p_scale != NULL) {
2204       *p_scale = 1;
2205     }
2206     return true;
2207   }
2208   int opc = exp->Opcode();
2209   if (opc == Op_MulI) {
2210     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
2211       if (p_scale != NULL) {
2212         *p_scale = exp->in(2)->get_int();
2213       }
2214       return true;
2215     }
2216     if (exp->in(2) == iv && exp->in(1)->is_Con()) {
2217       if (p_scale != NULL) {
2218         *p_scale = exp->in(1)->get_int();
2219       }
2220       return true;
2221     }
2222   } else if (opc == Op_LShiftI) {
2223     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
2224       if (p_scale != NULL) {
2225         *p_scale = 1 << exp->in(2)->get_int();
2226       }
2227       return true;
2228     }
2229   }
2230   return false;
2231 }
2232 
2233 //-----------------------------is_scaled_iv_plus_offset------------------------------
2234 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
2235 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
2236   if (is_scaled_iv(exp, iv, p_scale)) {
2237     if (p_offset != NULL) {
2238       Node *zero = _igvn.intcon(0);
2239       set_ctrl(zero, C->root());
2240       *p_offset = zero;
2241     }
2242     return true;
2243   }
2244   int opc = exp->Opcode();
2245   if (opc == Op_AddI) {
2246     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
2247       if (p_offset != NULL) {
2248         *p_offset = exp->in(2);
2249       }
2250       return true;
2251     }
2252     if (is_scaled_iv(exp->in(2), iv, p_scale)) {
2253       if (p_offset != NULL) {
2254         *p_offset = exp->in(1);
2255       }
2256       return true;
2257     }
2258     if (exp->in(2)->is_Con()) {
2259       Node* offset2 = NULL;
2260       if (depth < 2 &&
2261           is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
2262                                    p_offset != NULL ? &offset2 : NULL, depth+1)) {
2263         if (p_offset != NULL) {
2264           Node *ctrl_off2 = get_ctrl(offset2);
2265           Node* offset = new AddINode(offset2, exp->in(2));
2266           register_new_node(offset, ctrl_off2);
2267           *p_offset = offset;
2268         }
2269         return true;
2270       }
2271     }
2272   } else if (opc == Op_SubI) {
2273     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
2274       if (p_offset != NULL) {
2275         Node *zero = _igvn.intcon(0);
2276         set_ctrl(zero, C->root());
2277         Node *ctrl_off = get_ctrl(exp->in(2));
2278         Node* offset = new SubINode(zero, exp->in(2));
2279         register_new_node(offset, ctrl_off);
2280         *p_offset = offset;
2281       }
2282       return true;
2283     }
2284     if (is_scaled_iv(exp->in(2), iv, p_scale)) {
2285       if (p_offset != NULL) {
2286         *p_scale *= -1;
2287         *p_offset = exp->in(1);
2288       }
2289       return true;
2290     }
2291   }
2292   return false;
2293 }
2294 
2295 // Same as PhaseIdealLoop::duplicate_predicates() but for range checks
2296 // eliminated by iteration splitting.
2297 Node* PhaseIdealLoop::add_range_check_predicate(IdealLoopTree* loop, CountedLoopNode* cl,
2298                                                 Node* predicate_proj, int scale_con, Node* offset,
2299                                                 Node* limit, jint stride_con) {
2300   bool overflow = false;
2301   BoolNode* bol = rc_predicate(loop, predicate_proj, scale_con, offset, cl->init_trip(), NULL, stride_con, limit, (stride_con > 0) != (scale_con > 0), overflow);
2302   Node* opaque_bol = new Opaque4Node(C, bol, _igvn.intcon(1));
2303   register_new_node(opaque_bol, predicate_proj);
2304   IfNode* new_iff = NULL;
2305   if (overflow) {
2306     new_iff = new IfNode(predicate_proj, opaque_bol, PROB_MAX, COUNT_UNKNOWN);
2307   } else {
2308     new_iff = new RangeCheckNode(predicate_proj, opaque_bol, PROB_MAX, COUNT_UNKNOWN);
2309   }
2310   register_control(new_iff, loop->_parent, predicate_proj);
2311   Node* iffalse = new IfFalseNode(new_iff);
2312   register_control(iffalse, _ltree_root, new_iff);
2313   ProjNode* iftrue = new IfTrueNode(new_iff);
2314   register_control(iftrue, loop->_parent, new_iff);
2315   Node *frame = new ParmNode(C->start(), TypeFunc::FramePtr);
2316   register_new_node(frame, C->start());
2317   Node* halt = new HaltNode(iffalse, frame);
2318   register_control(halt, _ltree_root, iffalse);
2319   C->root()->add_req(halt);
2320   return iftrue;
2321 }
2322 
2323 //------------------------------do_range_check---------------------------------
2324 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
2325 int PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
2326 #ifndef PRODUCT
2327   if (PrintOpto && VerifyLoopOptimizations) {
2328     tty->print("Range Check Elimination ");
2329     loop->dump_head();
2330   } else if (TraceLoopOpts) {
2331     tty->print("RangeCheck   ");
2332     loop->dump_head();
2333   }
2334 #endif
2335   assert(RangeCheckElimination, "");
2336   CountedLoopNode *cl = loop->_head->as_CountedLoop();
2337   // If we fail before trying to eliminate range checks, set multiversion state
2338   int closed_range_checks = 1;
2339 
2340   // protect against stride not being a constant
2341   if (!cl->stride_is_con())
2342     return closed_range_checks;
2343 
2344   // Find the trip counter; we are iteration splitting based on it
2345   Node *trip_counter = cl->phi();
2346   // Find the main loop limit; we will trim it's iterations
2347   // to not ever trip end tests
2348   Node *main_limit = cl->limit();
2349 
2350   // Check graph shape. Cannot optimize a loop if zero-trip
2351   // Opaque1 node is optimized away and then another round
2352   // of loop opts attempted.
2353   if (!is_canonical_loop_entry(cl)) {
2354     return closed_range_checks;
2355   }
2356 
2357   // Need to find the main-loop zero-trip guard
2358   Node *ctrl  = cl->skip_predicates();
2359   Node *iffm = ctrl->in(0);
2360   Node *opqzm = iffm->in(1)->in(1)->in(2);
2361   assert(opqzm->in(1) == main_limit, "do not understand situation");
2362 
2363   // Find the pre-loop limit; we will expand its iterations to
2364   // not ever trip low tests.
2365   Node *p_f = iffm->in(0);
2366   // pre loop may have been optimized out
2367   if (p_f->Opcode() != Op_IfFalse) {
2368     return closed_range_checks;
2369   }
2370   CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
2371   assert(pre_end->loopnode()->is_pre_loop(), "");
2372   Node *pre_opaq1 = pre_end->limit();
2373   // Occasionally it's possible for a pre-loop Opaque1 node to be
2374   // optimized away and then another round of loop opts attempted.
2375   // We can not optimize this particular loop in that case.
2376   if (pre_opaq1->Opcode() != Op_Opaque1)
2377     return closed_range_checks;
2378   Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
2379   Node *pre_limit = pre_opaq->in(1);
2380 
2381   // Where do we put new limit calculations
2382   Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
2383 
2384   // Ensure the original loop limit is available from the
2385   // pre-loop Opaque1 node.
2386   Node *orig_limit = pre_opaq->original_loop_limit();
2387   if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
2388     return closed_range_checks;
2389 
2390   // Must know if its a count-up or count-down loop
2391 
2392   int stride_con = cl->stride_con();
2393   Node *zero = _igvn.intcon(0);
2394   Node *one  = _igvn.intcon(1);
2395   // Use symmetrical int range [-max_jint,max_jint]
2396   Node *mini = _igvn.intcon(-max_jint);
2397   set_ctrl(zero, C->root());
2398   set_ctrl(one,  C->root());
2399   set_ctrl(mini, C->root());
2400 
2401   // Range checks that do not dominate the loop backedge (ie.
2402   // conditionally executed) can lengthen the pre loop limit beyond
2403   // the original loop limit. To prevent this, the pre limit is
2404   // (for stride > 0) MINed with the original loop limit (MAXed
2405   // stride < 0) when some range_check (rc) is conditionally
2406   // executed.
2407   bool conditional_rc = false;
2408 
2409   // Count number of range checks and reduce by load range limits, if zero,
2410   // the loop is in canonical form to multiversion.
2411   closed_range_checks = 0;
2412 
2413   Node* predicate_proj = cl->skip_strip_mined()->in(LoopNode::EntryControl);
2414   assert(predicate_proj->is_Proj() && predicate_proj->in(0)->is_If(), "if projection only");
2415   // Check loop body for tests of trip-counter plus loop-invariant vs loop-variant.
2416   for( uint i = 0; i < loop->_body.size(); i++ ) {
2417     Node *iff = loop->_body[i];
2418     if (iff->Opcode() == Op_If ||
2419         iff->Opcode() == Op_RangeCheck) { // Test?
2420       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
2421       // we need loop unswitching instead of iteration splitting.
2422       closed_range_checks++;
2423       Node *exit = loop->is_loop_exit(iff);
2424       if( !exit ) continue;
2425       int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
2426 
2427       // Get boolean condition to test
2428       Node *i1 = iff->in(1);
2429       if( !i1->is_Bool() ) continue;
2430       BoolNode *bol = i1->as_Bool();
2431       BoolTest b_test = bol->_test;
2432       // Flip sense of test if exit condition is flipped
2433       if( flip )
2434         b_test = b_test.negate();
2435 
2436       // Get compare
2437       Node *cmp = bol->in(1);
2438 
2439       // Look for trip_counter + offset vs limit
2440       Node *rc_exp = cmp->in(1);
2441       Node *limit  = cmp->in(2);
2442       int scale_con= 1;        // Assume trip counter not scaled
2443 
2444       Node *limit_c = get_ctrl(limit);
2445       if( loop->is_member(get_loop(limit_c) ) ) {
2446         // Compare might have operands swapped; commute them
2447         b_test = b_test.commute();
2448         rc_exp = cmp->in(2);
2449         limit  = cmp->in(1);
2450         limit_c = get_ctrl(limit);
2451         if( loop->is_member(get_loop(limit_c) ) )
2452           continue;             // Both inputs are loop varying; cannot RCE
2453       }
2454       // Here we know 'limit' is loop invariant
2455 
2456       // 'limit' maybe pinned below the zero trip test (probably from a
2457       // previous round of rce), in which case, it can't be used in the
2458       // zero trip test expression which must occur before the zero test's if.
2459       if (is_dominator(ctrl, limit_c)) {
2460         continue;  // Don't rce this check but continue looking for other candidates.
2461       }
2462 
2463       // Check for scaled induction variable plus an offset
2464       Node *offset = NULL;
2465 
2466       if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
2467         continue;
2468       }
2469 
2470       Node *offset_c = get_ctrl(offset);
2471       if( loop->is_member( get_loop(offset_c) ) )
2472         continue;               // Offset is not really loop invariant
2473       // Here we know 'offset' is loop invariant.
2474 
2475       // As above for the 'limit', the 'offset' maybe pinned below the
2476       // zero trip test.
2477       if (is_dominator(ctrl, offset_c)) {
2478         continue; // Don't rce this check but continue looking for other candidates.
2479       }
2480 #ifdef ASSERT
2481       if (TraceRangeLimitCheck) {
2482         tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
2483         bol->dump(2);
2484       }
2485 #endif
2486       // At this point we have the expression as:
2487       //   scale_con * trip_counter + offset :: limit
2488       // where scale_con, offset and limit are loop invariant.  Trip_counter
2489       // monotonically increases by stride_con, a constant.  Both (or either)
2490       // stride_con and scale_con can be negative which will flip about the
2491       // sense of the test.
2492 
2493       // Adjust pre and main loop limits to guard the correct iteration set
2494       if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
2495         if( b_test._test == BoolTest::lt ) { // Range checks always use lt
2496           // The underflow and overflow limits: 0 <= scale*I+offset < limit
2497           add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit );
2498           // (0-offset)/scale could be outside of loop iterations range.
2499           conditional_rc = true;
2500           predicate_proj = add_range_check_predicate(loop, cl, predicate_proj, scale_con, offset, limit, stride_con);
2501         } else {
2502           if (PrintOpto) {
2503             tty->print_cr("missed RCE opportunity");
2504           }
2505           continue;             // In release mode, ignore it
2506         }
2507       } else {                  // Otherwise work on normal compares
2508         switch( b_test._test ) {
2509         case BoolTest::gt:
2510           // Fall into GE case
2511         case BoolTest::ge:
2512           // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
2513           scale_con = -scale_con;
2514           offset = new SubINode( zero, offset );
2515           register_new_node( offset, pre_ctrl );
2516           limit  = new SubINode( zero, limit );
2517           register_new_node( limit, pre_ctrl );
2518           // Fall into LE case
2519         case BoolTest::le:
2520           if (b_test._test != BoolTest::gt) {
2521             // Convert X <= Y to X < Y+1
2522             limit = new AddINode( limit, one );
2523             register_new_node( limit, pre_ctrl );
2524           }
2525           // Fall into LT case
2526         case BoolTest::lt:
2527           // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
2528           // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
2529           // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
2530           add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit );
2531           // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range.
2532           // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could
2533           // still be outside of loop range.
2534           conditional_rc = true;
2535           break;
2536         default:
2537           if (PrintOpto) {
2538             tty->print_cr("missed RCE opportunity");
2539           }
2540           continue;             // Unhandled case
2541         }
2542       }
2543 
2544       // Kill the eliminated test
2545       C->set_major_progress();
2546       Node *kill_con = _igvn.intcon( 1-flip );
2547       set_ctrl(kill_con, C->root());
2548       _igvn.replace_input_of(iff, 1, kill_con);
2549       // Find surviving projection
2550       assert(iff->is_If(), "");
2551       ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
2552       // Find loads off the surviving projection; remove their control edge
2553       for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
2554         Node* cd = dp->fast_out(i); // Control-dependent node
2555         if (cd->is_Load() && cd->depends_only_on_test()) {   // Loads can now float around in the loop
2556           // Allow the load to float around in the loop, or before it
2557           // but NOT before the pre-loop.
2558           _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL
2559           --i;
2560           --imax;
2561         }
2562       }
2563       if (limit->Opcode() == Op_LoadRange) {
2564         closed_range_checks--;
2565       }
2566 
2567     } // End of is IF
2568 
2569   }
2570   if (predicate_proj != cl->skip_strip_mined()->in(LoopNode::EntryControl)) {
2571     _igvn.replace_input_of(cl->skip_strip_mined(), LoopNode::EntryControl, predicate_proj);
2572     set_idom(cl->skip_strip_mined(), predicate_proj, dom_depth(cl->skip_strip_mined()));
2573   }
2574 
2575   // Update loop limits
2576   if (conditional_rc) {
2577     pre_limit = (stride_con > 0) ? (Node*)new MinINode(pre_limit, orig_limit)
2578                                  : (Node*)new MaxINode(pre_limit, orig_limit);
2579     register_new_node(pre_limit, pre_ctrl);
2580   }
2581   _igvn.replace_input_of(pre_opaq, 1, pre_limit);
2582 
2583   // Note:: we are making the main loop limit no longer precise;
2584   // need to round up based on stride.
2585   cl->set_nonexact_trip_count();
2586   Node *main_cle = cl->loopexit();
2587   Node *main_bol = main_cle->in(1);
2588   // Hacking loop bounds; need private copies of exit test
2589   if( main_bol->outcnt() > 1 ) {// BoolNode shared?
2590     main_bol = main_bol->clone();// Clone a private BoolNode
2591     register_new_node( main_bol, main_cle->in(0) );
2592     _igvn.replace_input_of(main_cle, 1, main_bol);
2593   }
2594   Node *main_cmp = main_bol->in(1);
2595   if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
2596     main_cmp = main_cmp->clone();// Clone a private CmpNode
2597     register_new_node( main_cmp, main_cle->in(0) );
2598     _igvn.replace_input_of(main_bol, 1, main_cmp);
2599   }
2600   // Hack the now-private loop bounds
2601   _igvn.replace_input_of(main_cmp, 2, main_limit);
2602   // The OpaqueNode is unshared by design
2603   assert( opqzm->outcnt() == 1, "cannot hack shared node" );
2604   _igvn.replace_input_of(opqzm, 1, main_limit);
2605 
2606   return closed_range_checks;
2607 }
2608 
2609 //------------------------------has_range_checks-------------------------------
2610 // Check to see if RCE cleaned the current loop of range-checks.
2611 void PhaseIdealLoop::has_range_checks(IdealLoopTree *loop) {
2612   assert(RangeCheckElimination, "");
2613 
2614   // skip if not a counted loop
2615   if (!loop->is_counted()) return;
2616 
2617   CountedLoopNode *cl = loop->_head->as_CountedLoop();
2618 
2619   // skip this loop if it is already checked
2620   if (cl->has_been_range_checked()) return;
2621 
2622   // Now check for existence of range checks
2623   for (uint i = 0; i < loop->_body.size(); i++) {
2624     Node *iff = loop->_body[i];
2625     int iff_opc = iff->Opcode();
2626     if (iff_opc == Op_If || iff_opc == Op_RangeCheck) {
2627       cl->mark_has_range_checks();
2628       break;
2629     }
2630   }
2631   cl->set_has_been_range_checked();
2632 }
2633 
2634 //-------------------------multi_version_post_loops----------------------------
2635 // Check the range checks that remain, if simple, use the bounds to guard
2636 // which version to a post loop we execute, one with range checks or one without
2637 bool PhaseIdealLoop::multi_version_post_loops(IdealLoopTree *rce_loop, IdealLoopTree *legacy_loop) {
2638   bool multi_version_succeeded = false;
2639   assert(RangeCheckElimination, "");
2640   CountedLoopNode *legacy_cl = legacy_loop->_head->as_CountedLoop();
2641   assert(legacy_cl->is_post_loop(), "");
2642 
2643   // Check for existence of range checks using the unique instance to make a guard with
2644   Unique_Node_List worklist;
2645   for (uint i = 0; i < legacy_loop->_body.size(); i++) {
2646     Node *iff = legacy_loop->_body[i];
2647     int iff_opc = iff->Opcode();
2648     if (iff_opc == Op_If || iff_opc == Op_RangeCheck) {
2649       worklist.push(iff);
2650     }
2651   }
2652 
2653   // Find RCE'd post loop so that we can stage its guard.
2654   if (!is_canonical_loop_entry(legacy_cl)) return multi_version_succeeded;
2655   Node* ctrl = legacy_cl->in(LoopNode::EntryControl);
2656   Node* iffm = ctrl->in(0);
2657 
2658   // Now we test that both the post loops are connected
2659   Node* post_loop_region = iffm->in(0);
2660   if (post_loop_region == NULL) return multi_version_succeeded;
2661   if (!post_loop_region->is_Region()) return multi_version_succeeded;
2662   Node* covering_region = post_loop_region->in(RegionNode::Control+1);
2663   if (covering_region == NULL) return multi_version_succeeded;
2664   if (!covering_region->is_Region()) return multi_version_succeeded;
2665   Node* p_f = covering_region->in(RegionNode::Control);
2666   if (p_f == NULL) return multi_version_succeeded;
2667   if (!p_f->is_IfFalse()) return multi_version_succeeded;
2668   if (!p_f->in(0)->is_CountedLoopEnd()) return multi_version_succeeded;
2669   CountedLoopEndNode* rce_loop_end = p_f->in(0)->as_CountedLoopEnd();
2670   if (rce_loop_end == NULL) return multi_version_succeeded;
2671   CountedLoopNode* rce_cl = rce_loop_end->loopnode();
2672   if (rce_cl == NULL || !rce_cl->is_post_loop()) return multi_version_succeeded;
2673   CountedLoopNode *known_rce_cl = rce_loop->_head->as_CountedLoop();
2674   if (rce_cl != known_rce_cl) return multi_version_succeeded;
2675 
2676   // Then we fetch the cover entry test
2677   ctrl = rce_cl->in(LoopNode::EntryControl);
2678   if (!ctrl->is_IfTrue() && !ctrl->is_IfFalse()) return multi_version_succeeded;
2679 
2680 #ifndef PRODUCT
2681   if (TraceLoopOpts) {
2682     tty->print("PostMultiVersion\n");
2683     rce_loop->dump_head();
2684     legacy_loop->dump_head();
2685   }
2686 #endif
2687 
2688   // Now fetch the limit we want to compare against
2689   Node *limit = rce_cl->limit();
2690   bool first_time = true;
2691 
2692   // If we got this far, we identified the post loop which has been RCE'd and
2693   // we have a work list.  Now we will try to transform the if guard to cause
2694   // the loop pair to be multi version executed with the determination left to runtime
2695   // or the optimizer if full information is known about the given arrays at compile time.
2696   Node *last_min = NULL;
2697   multi_version_succeeded = true;
2698   while (worklist.size()) {
2699     Node* rc_iffm = worklist.pop();
2700     if (rc_iffm->is_If()) {
2701       Node *rc_bolzm = rc_iffm->in(1);
2702       if (rc_bolzm->is_Bool()) {
2703         Node *rc_cmpzm = rc_bolzm->in(1);
2704         if (rc_cmpzm->is_Cmp()) {
2705           Node *rc_left = rc_cmpzm->in(2);
2706           if (rc_left->Opcode() != Op_LoadRange) {
2707             multi_version_succeeded = false;
2708             break;
2709           }
2710           if (first_time) {
2711             last_min = rc_left;
2712             first_time = false;
2713           } else {
2714             Node *cur_min = new MinINode(last_min, rc_left);
2715             last_min = cur_min;
2716             _igvn.register_new_node_with_optimizer(last_min);
2717           }
2718         }
2719       }
2720     }
2721   }
2722 
2723   // All we have to do is update the limit of the rce loop
2724   // with the min of our expression and the current limit.
2725   // We will use this expression to replace the current limit.
2726   if (last_min && multi_version_succeeded) {
2727     Node *cur_min = new MinINode(last_min, limit);
2728     _igvn.register_new_node_with_optimizer(cur_min);
2729     Node *cmp_node = rce_loop_end->cmp_node();
2730     _igvn.replace_input_of(cmp_node, 2, cur_min);
2731     set_ctrl(cur_min, ctrl);
2732     set_loop(cur_min, rce_loop->_parent);
2733 
2734     legacy_cl->mark_is_multiversioned();
2735     rce_cl->mark_is_multiversioned();
2736     multi_version_succeeded = true;
2737 
2738     C->set_major_progress();
2739   }
2740 
2741   return multi_version_succeeded;
2742 }
2743 
2744 //-------------------------poison_rce_post_loop--------------------------------
2745 // Causes the rce'd post loop to be optimized away if multiversioning fails
2746 void PhaseIdealLoop::poison_rce_post_loop(IdealLoopTree *rce_loop) {
2747   CountedLoopNode *rce_cl = rce_loop->_head->as_CountedLoop();
2748   Node* ctrl = rce_cl->in(LoopNode::EntryControl);
2749   if (ctrl->is_IfTrue() || ctrl->is_IfFalse()) {
2750     Node* iffm = ctrl->in(0);
2751     if (iffm->is_If()) {
2752       Node* cur_bool = iffm->in(1);
2753       if (cur_bool->is_Bool()) {
2754         Node* cur_cmp = cur_bool->in(1);
2755         if (cur_cmp->is_Cmp()) {
2756           BoolTest::mask new_test = BoolTest::gt;
2757           BoolNode *new_bool = new BoolNode(cur_cmp, new_test);
2758           _igvn.replace_node(cur_bool, new_bool);
2759           _igvn._worklist.push(new_bool);
2760           Node* left_op = cur_cmp->in(1);
2761           _igvn.replace_input_of(cur_cmp, 2, left_op);
2762           C->set_major_progress();
2763         }
2764       }
2765     }
2766   }
2767 }
2768 
2769 //------------------------------DCE_loop_body----------------------------------
2770 // Remove simplistic dead code from loop body
2771 void IdealLoopTree::DCE_loop_body() {
2772   for( uint i = 0; i < _body.size(); i++ )
2773     if( _body.at(i)->outcnt() == 0 )
2774       _body.map( i--, _body.pop() );
2775 }
2776 
2777 
2778 //------------------------------adjust_loop_exit_prob--------------------------
2779 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
2780 // Replace with a 1-in-10 exit guess.
2781 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
2782   Node *test = tail();
2783   while( test != _head ) {
2784     uint top = test->Opcode();
2785     if( top == Op_IfTrue || top == Op_IfFalse ) {
2786       int test_con = ((ProjNode*)test)->_con;
2787       assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
2788       IfNode *iff = test->in(0)->as_If();
2789       if( iff->outcnt() == 2 ) {        // Ignore dead tests
2790         Node *bol = iff->in(1);
2791         if( bol && bol->req() > 1 && bol->in(1) &&
2792             ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
2793              (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
2794              (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
2795 #if INCLUDE_SHENANDOAHGC
2796              (bol->in(1)->Opcode() == Op_ShenandoahCompareAndExchangeP ) ||
2797              (bol->in(1)->Opcode() == Op_ShenandoahCompareAndExchangeN ) ||
2798              (bol->in(1)->Opcode() == Op_ShenandoahWeakCompareAndSwapP ) ||
2799              (bol->in(1)->Opcode() == Op_ShenandoahWeakCompareAndSwapN ) ||
2800              (bol->in(1)->Opcode() == Op_ShenandoahCompareAndSwapP ) ||
2801              (bol->in(1)->Opcode() == Op_ShenandoahCompareAndSwapN ) ||
2802 #endif
2803              (bol->in(1)->Opcode() == Op_CompareAndExchangeB ) ||
2804              (bol->in(1)->Opcode() == Op_CompareAndExchangeS ) ||
2805              (bol->in(1)->Opcode() == Op_CompareAndExchangeI ) ||
2806              (bol->in(1)->Opcode() == Op_CompareAndExchangeL ) ||
2807              (bol->in(1)->Opcode() == Op_CompareAndExchangeP ) ||
2808              (bol->in(1)->Opcode() == Op_CompareAndExchangeN ) ||
2809              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapB ) ||
2810              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapS ) ||
2811              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapI ) ||
2812              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapL ) ||
2813              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapP ) ||
2814              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapN ) ||
2815              (bol->in(1)->Opcode() == Op_CompareAndSwapB ) ||
2816              (bol->in(1)->Opcode() == Op_CompareAndSwapS ) ||
2817              (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
2818              (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
2819              (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
2820              (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
2821           return;               // Allocation loops RARELY take backedge
2822         // Find the OTHER exit path from the IF
2823         Node* ex = iff->proj_out(1-test_con);
2824         float p = iff->_prob;
2825         if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
2826           if( top == Op_IfTrue ) {
2827             if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
2828               iff->_prob = PROB_STATIC_FREQUENT;
2829             }
2830           } else {
2831             if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
2832               iff->_prob = PROB_STATIC_INFREQUENT;
2833             }
2834           }
2835         }
2836       }
2837     }
2838     test = phase->idom(test);
2839   }
2840 }
2841 
2842 #ifdef ASSERT
2843 static CountedLoopNode* locate_pre_from_main(CountedLoopNode *cl) {
2844   Node *ctrl  = cl->skip_predicates();
2845   assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
2846   Node *iffm = ctrl->in(0);
2847   assert(iffm->Opcode() == Op_If, "");
2848   Node *p_f = iffm->in(0);
2849   assert(p_f->Opcode() == Op_IfFalse, "");
2850   CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
2851   assert(pre_end->loopnode()->is_pre_loop(), "");
2852   return pre_end->loopnode();
2853 }
2854 #endif
2855 
2856 // Remove the main and post loops and make the pre loop execute all
2857 // iterations. Useful when the pre loop is found empty.
2858 void IdealLoopTree::remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase) {
2859   CountedLoopEndNode* pre_end = cl->loopexit();
2860   Node* pre_cmp = pre_end->cmp_node();
2861   if (pre_cmp->in(2)->Opcode() != Op_Opaque1) {
2862     // Only safe to remove the main loop if the compiler optimized it
2863     // out based on an unknown number of iterations
2864     return;
2865   }
2866 
2867   // Can we find the main loop?
2868   if (_next == NULL) {
2869     return;
2870   }
2871 
2872   Node* next_head = _next->_head;
2873   if (!next_head->is_CountedLoop()) {
2874     return;
2875   }
2876 
2877   CountedLoopNode* main_head = next_head->as_CountedLoop();
2878   if (!main_head->is_main_loop()) {
2879     return;
2880   }
2881 
2882   assert(locate_pre_from_main(main_head) == cl, "bad main loop");
2883   Node* main_iff = main_head->skip_predicates()->in(0);
2884 
2885   // Remove the Opaque1Node of the pre loop and make it execute all iterations
2886   phase->_igvn.replace_input_of(pre_cmp, 2, pre_cmp->in(2)->in(2));
2887   // Remove the Opaque1Node of the main loop so it can be optimized out
2888   Node* main_cmp = main_iff->in(1)->in(1);
2889   assert(main_cmp->in(2)->Opcode() == Op_Opaque1, "main loop has no opaque node?");
2890   phase->_igvn.replace_input_of(main_cmp, 2, main_cmp->in(2)->in(1));
2891 }
2892 
2893 //------------------------------policy_do_remove_empty_loop--------------------
2894 // Micro-benchmark spamming.  Policy is to always remove empty loops.
2895 // The 'DO' part is to replace the trip counter with the value it will
2896 // have on the last iteration.  This will break the loop.
2897 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
2898   // Minimum size must be empty loop
2899   if (_body.size() > EMPTY_LOOP_SIZE)
2900     return false;
2901 
2902   if (!_head->is_CountedLoop())
2903     return false;     // Dead loop
2904   CountedLoopNode *cl = _head->as_CountedLoop();
2905   if (!cl->is_valid_counted_loop())
2906     return false; // Malformed loop
2907   if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
2908     return false;             // Infinite loop
2909 
2910   if (cl->is_pre_loop()) {
2911     // If the loop we are removing is a pre-loop then the main and
2912     // post loop can be removed as well
2913     remove_main_post_loops(cl, phase);
2914   }
2915 
2916 #ifdef ASSERT
2917   // Ensure only one phi which is the iv.
2918   Node* iv = NULL;
2919   for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
2920     Node* n = cl->fast_out(i);
2921     if (n->Opcode() == Op_Phi) {
2922       assert(iv == NULL, "Too many phis" );
2923       iv = n;
2924     }
2925   }
2926   assert(iv == cl->phi(), "Wrong phi" );
2927 #endif
2928 
2929   // main and post loops have explicitly created zero trip guard
2930   bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
2931   if (needs_guard) {
2932     // Skip guard if values not overlap.
2933     const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
2934     const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
2935     int  stride_con = cl->stride_con();
2936     if (stride_con > 0) {
2937       needs_guard = (init_t->_hi >= limit_t->_lo);
2938     } else {
2939       needs_guard = (init_t->_lo <= limit_t->_hi);
2940     }
2941   }
2942   if (needs_guard) {
2943     // Check for an obvious zero trip guard.
2944     Node* inctrl = PhaseIdealLoop::skip_all_loop_predicates(cl->skip_predicates());
2945     if (inctrl->Opcode() == Op_IfTrue || inctrl->Opcode() == Op_IfFalse) {
2946       bool maybe_swapped = (inctrl->Opcode() == Op_IfFalse);
2947       // The test should look like just the backedge of a CountedLoop
2948       Node* iff = inctrl->in(0);
2949       if (iff->is_If()) {
2950         Node* bol = iff->in(1);
2951         if (bol->is_Bool()) {
2952           BoolTest test = bol->as_Bool()->_test;
2953           if (maybe_swapped) {
2954             test._test = test.commute();
2955             test._test = test.negate();
2956           }
2957           if (test._test == cl->loopexit()->test_trip()) {
2958             Node* cmp = bol->in(1);
2959             int init_idx = maybe_swapped ? 2 : 1;
2960             int limit_idx = maybe_swapped ? 1 : 2;
2961             if (cmp->is_Cmp() && cmp->in(init_idx) == cl->init_trip() && cmp->in(limit_idx) == cl->limit()) {
2962               needs_guard = false;
2963             }
2964           }
2965         }
2966       }
2967     }
2968   }
2969 
2970 #ifndef PRODUCT
2971   if (PrintOpto) {
2972     tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
2973     this->dump_head();
2974   } else if (TraceLoopOpts) {
2975     tty->print("Empty with%s zero trip guard   ", needs_guard ? "out" : "");
2976     this->dump_head();
2977   }
2978 #endif
2979 
2980   if (needs_guard) {
2981     // Peel the loop to ensure there's a zero trip guard
2982     Node_List old_new;
2983     phase->do_peeling(this, old_new);
2984   }
2985 
2986   // Replace the phi at loop head with the final value of the last
2987   // iteration.  Then the CountedLoopEnd will collapse (backedge never
2988   // taken) and all loop-invariant uses of the exit values will be correct.
2989   Node *phi = cl->phi();
2990   Node *exact_limit = phase->exact_limit(this);
2991   if (exact_limit != cl->limit()) {
2992     // We also need to replace the original limit to collapse loop exit.
2993     Node* cmp = cl->loopexit()->cmp_node();
2994     assert(cl->limit() == cmp->in(2), "sanity");
2995     phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
2996     phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist
2997   }
2998   // Note: the final value after increment should not overflow since
2999   // counted loop has limit check predicate.
3000   Node *final = new SubINode( exact_limit, cl->stride() );
3001   phase->register_new_node(final,cl->in(LoopNode::EntryControl));
3002   phase->_igvn.replace_node(phi,final);
3003   phase->C->set_major_progress();
3004   return true;
3005 }
3006 
3007 //------------------------------policy_do_one_iteration_loop-------------------
3008 // Convert one iteration loop into normal code.
3009 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) {
3010   if (!_head->as_Loop()->is_valid_counted_loop())
3011     return false; // Only for counted loop
3012 
3013   CountedLoopNode *cl = _head->as_CountedLoop();
3014   if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
3015     return false;
3016   }
3017 
3018 #ifndef PRODUCT
3019   if(TraceLoopOpts) {
3020     tty->print("OneIteration ");
3021     this->dump_head();
3022   }
3023 #endif
3024 
3025   Node *init_n = cl->init_trip();
3026 #ifdef ASSERT
3027   // Loop boundaries should be constant since trip count is exact.
3028   assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration");
3029 #endif
3030   // Replace the phi at loop head with the value of the init_trip.
3031   // Then the CountedLoopEnd will collapse (backedge will not be taken)
3032   // and all loop-invariant uses of the exit values will be correct.
3033   phase->_igvn.replace_node(cl->phi(), cl->init_trip());
3034   phase->C->set_major_progress();
3035   return true;
3036 }
3037 
3038 //=============================================================================
3039 //------------------------------iteration_split_impl---------------------------
3040 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
3041   // Compute loop trip count if possible.
3042   compute_trip_count(phase);
3043 
3044   // Convert one iteration loop into normal code.
3045   if (policy_do_one_iteration_loop(phase))
3046     return true;
3047 
3048   // Check and remove empty loops (spam micro-benchmarks)
3049   if (policy_do_remove_empty_loop(phase))
3050     return true;  // Here we removed an empty loop
3051 
3052   bool should_peel = policy_peeling(phase); // Should we peel?
3053 
3054   bool should_unswitch = policy_unswitching(phase);
3055 
3056   // Non-counted loops may be peeled; exactly 1 iteration is peeled.
3057   // This removes loop-invariant tests (usually null checks).
3058   if (!_head->is_CountedLoop()) { // Non-counted loop
3059     if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
3060       // Partial peel succeeded so terminate this round of loop opts
3061       return false;
3062     }
3063     if (should_peel) {            // Should we peel?
3064       if (PrintOpto) { tty->print_cr("should_peel"); }
3065       phase->do_peeling(this,old_new);
3066     } else if (should_unswitch) {
3067       phase->do_unswitching(this, old_new);
3068     }
3069     return true;
3070   }
3071   CountedLoopNode *cl = _head->as_CountedLoop();
3072 
3073   if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops
3074 
3075   // Do nothing special to pre- and post- loops
3076   if (cl->is_pre_loop() || cl->is_post_loop()) return true;
3077 
3078   // Compute loop trip count from profile data
3079   compute_profile_trip_cnt(phase);
3080 
3081   // Before attempting fancy unrolling, RCE or alignment, see if we want
3082   // to completely unroll this loop or do loop unswitching.
3083   if (cl->is_normal_loop()) {
3084     if (should_unswitch) {
3085       phase->do_unswitching(this, old_new);
3086       return true;
3087     }
3088     bool should_maximally_unroll =  policy_maximally_unroll(phase);
3089     if (should_maximally_unroll) {
3090       // Here we did some unrolling and peeling.  Eventually we will
3091       // completely unroll this loop and it will no longer be a loop.
3092       phase->do_maximally_unroll(this,old_new);
3093       return true;
3094     }
3095   }
3096 
3097   // Skip next optimizations if running low on nodes. Note that
3098   // policy_unswitching and policy_maximally_unroll have this check.
3099   int nodes_left = phase->C->max_node_limit() - phase->C->live_nodes();
3100   if ((int)(2 * _body.size()) > nodes_left) {
3101     return true;
3102   }
3103 
3104   // Counted loops may be peeled, may need some iterations run up
3105   // front for RCE, and may want to align loop refs to a cache
3106   // line.  Thus we clone a full loop up front whose trip count is
3107   // at least 1 (if peeling), but may be several more.
3108 
3109   // The main loop will start cache-line aligned with at least 1
3110   // iteration of the unrolled body (zero-trip test required) and
3111   // will have some range checks removed.
3112 
3113   // A post-loop will finish any odd iterations (leftover after
3114   // unrolling), plus any needed for RCE purposes.
3115 
3116   bool should_unroll = policy_unroll(phase);
3117 
3118   bool should_rce = policy_range_check(phase);
3119 
3120   bool should_align = policy_align(phase);
3121 
3122   // If not RCE'ing (iteration splitting) or Aligning, then we do not
3123   // need a pre-loop.  We may still need to peel an initial iteration but
3124   // we will not be needing an unknown number of pre-iterations.
3125   //
3126   // Basically, if may_rce_align reports FALSE first time through,
3127   // we will not be able to later do RCE or Aligning on this loop.
3128   bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
3129 
3130   // If we have any of these conditions (RCE, alignment, unrolling) met, then
3131   // we switch to the pre-/main-/post-loop model.  This model also covers
3132   // peeling.
3133   if (should_rce || should_align || should_unroll) {
3134     if (cl->is_normal_loop())  // Convert to 'pre/main/post' loops
3135       phase->insert_pre_post_loops(this,old_new, !may_rce_align);
3136 
3137     // Adjust the pre- and main-loop limits to let the pre and post loops run
3138     // with full checks, but the main-loop with no checks.  Remove said
3139     // checks from the main body.
3140     if (should_rce) {
3141       if (phase->do_range_check(this, old_new) != 0) {
3142         cl->mark_has_range_checks();
3143       }
3144     } else if (PostLoopMultiversioning) {
3145       phase->has_range_checks(this);
3146     }
3147 
3148     if (should_unroll && !should_peel && PostLoopMultiversioning) {
3149       // Try to setup multiversioning on main loops before they are unrolled
3150       if (cl->is_main_loop() && (cl->unrolled_count() == 1)) {
3151         phase->insert_scalar_rced_post_loop(this, old_new);
3152       }
3153     }
3154 
3155     // Double loop body for unrolling.  Adjust the minimum-trip test (will do
3156     // twice as many iterations as before) and the main body limit (only do
3157     // an even number of trips).  If we are peeling, we might enable some RCE
3158     // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
3159     // peeling.
3160     if (should_unroll && !should_peel) {
3161       if (SuperWordLoopUnrollAnalysis) {
3162         phase->insert_vector_post_loop(this, old_new);
3163       }
3164       phase->do_unroll(this, old_new, true);
3165     }
3166 
3167     // Adjust the pre-loop limits to align the main body
3168     // iterations.
3169     if (should_align)
3170       Unimplemented();
3171 
3172   } else {                      // Else we have an unchanged counted loop
3173     if (should_peel)           // Might want to peel but do nothing else
3174       phase->do_peeling(this,old_new);
3175   }
3176   return true;
3177 }
3178 
3179 
3180 //=============================================================================
3181 //------------------------------iteration_split--------------------------------
3182 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
3183   // Recursively iteration split nested loops
3184   if (_child && !_child->iteration_split(phase, old_new))
3185     return false;
3186 
3187   // Clean out prior deadwood
3188   DCE_loop_body();
3189 
3190 
3191   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
3192   // Replace with a 1-in-10 exit guess.
3193   if (_parent /*not the root loop*/ &&
3194       !_irreducible &&
3195       // Also ignore the occasional dead backedge
3196       !tail()->is_top()) {
3197     adjust_loop_exit_prob(phase);
3198   }
3199 
3200   // Gate unrolling, RCE and peeling efforts.
3201   if (!_child &&                // If not an inner loop, do not split
3202       !_irreducible &&
3203       _allow_optimizations &&
3204       !tail()->is_top()) {     // Also ignore the occasional dead backedge
3205     if (!_has_call) {
3206         if (!iteration_split_impl(phase, old_new)) {
3207           return false;
3208         }
3209     } else if (policy_unswitching(phase)) {
3210       phase->do_unswitching(this, old_new);
3211     }
3212   }
3213 
3214   // Minor offset re-organization to remove loop-fallout uses of
3215   // trip counter when there was no major reshaping.
3216   phase->reorg_offsets(this);
3217 
3218   if (_next && !_next->iteration_split(phase, old_new))
3219     return false;
3220   return true;
3221 }
3222 
3223 
3224 //=============================================================================
3225 // Process all the loops in the loop tree and replace any fill
3226 // patterns with an intrinsic version.
3227 bool PhaseIdealLoop::do_intrinsify_fill() {
3228   bool changed = false;
3229   for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3230     IdealLoopTree* lpt = iter.current();
3231     changed |= intrinsify_fill(lpt);
3232   }
3233   return changed;
3234 }
3235 
3236 
3237 // Examine an inner loop looking for a a single store of an invariant
3238 // value in a unit stride loop,
3239 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
3240                                      Node*& shift, Node*& con) {
3241   const char* msg = NULL;
3242   Node* msg_node = NULL;
3243 
3244   store_value = NULL;
3245   con = NULL;
3246   shift = NULL;
3247 
3248   // Process the loop looking for stores.  If there are multiple
3249   // stores or extra control flow give at this point.
3250   CountedLoopNode* head = lpt->_head->as_CountedLoop();
3251   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
3252     Node* n = lpt->_body.at(i);
3253     if (n->outcnt() == 0) continue; // Ignore dead
3254     if (n->is_Store()) {
3255       if (store != NULL) {
3256         msg = "multiple stores";
3257         break;
3258       }
3259       int opc = n->Opcode();
3260       if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass || opc == Op_StoreCM) {
3261         msg = "oop fills not handled";
3262         break;
3263       }
3264       Node* value = n->in(MemNode::ValueIn);
3265       if (!lpt->is_invariant(value)) {
3266         msg  = "variant store value";
3267       } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
3268         msg = "not array address";
3269       }
3270       store = n;
3271       store_value = value;
3272     } else if (n->is_If() && n != head->loopexit_or_null()) {
3273       msg = "extra control flow";
3274       msg_node = n;
3275     }
3276   }
3277 
3278   if (store == NULL) {
3279     // No store in loop
3280     return false;
3281   }
3282 
3283   if (msg == NULL && head->stride_con() != 1) {
3284     // could handle negative strides too
3285     if (head->stride_con() < 0) {
3286       msg = "negative stride";
3287     } else {
3288       msg = "non-unit stride";
3289     }
3290   }
3291 
3292   if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
3293     msg = "can't handle store address";
3294     msg_node = store->in(MemNode::Address);
3295   }
3296 
3297   if (msg == NULL &&
3298       (!store->in(MemNode::Memory)->is_Phi() ||
3299        store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
3300     msg = "store memory isn't proper phi";
3301     msg_node = store->in(MemNode::Memory);
3302   }
3303 
3304   // Make sure there is an appropriate fill routine
3305   BasicType t = store->as_Mem()->memory_type();
3306   const char* fill_name;
3307   if (msg == NULL &&
3308       StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
3309     msg = "unsupported store";
3310     msg_node = store;
3311   }
3312 
3313   if (msg != NULL) {
3314 #ifndef PRODUCT
3315     if (TraceOptimizeFill) {
3316       tty->print_cr("not fill intrinsic candidate: %s", msg);
3317       if (msg_node != NULL) msg_node->dump();
3318     }
3319 #endif
3320     return false;
3321   }
3322 
3323   // Make sure the address expression can be handled.  It should be
3324   // head->phi * elsize + con.  head->phi might have a ConvI2L(CastII()).
3325   Node* elements[4];
3326   Node* cast = NULL;
3327   Node* conv = NULL;
3328   bool found_index = false;
3329   int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
3330   for (int e = 0; e < count; e++) {
3331     Node* n = elements[e];
3332     if (n->is_Con() && con == NULL) {
3333       con = n;
3334     } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
3335       Node* value = n->in(1);
3336 #ifdef _LP64
3337       if (value->Opcode() == Op_ConvI2L) {
3338         conv = value;
3339         value = value->in(1);
3340       }
3341       if (value->Opcode() == Op_CastII &&
3342           value->as_CastII()->has_range_check()) {
3343         // Skip range check dependent CastII nodes
3344         cast = value;
3345         value = value->in(1);
3346       }
3347 #endif
3348       if (value != head->phi()) {
3349         msg = "unhandled shift in address";
3350       } else {
3351         if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) {
3352           msg = "scale doesn't match";
3353         } else {
3354           found_index = true;
3355           shift = n;
3356         }
3357       }
3358     } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
3359       conv = n;
3360       n = n->in(1);
3361       if (n->Opcode() == Op_CastII &&
3362           n->as_CastII()->has_range_check()) {
3363         // Skip range check dependent CastII nodes
3364         cast = n;
3365         n = n->in(1);
3366       }
3367       if (n == head->phi()) {
3368         found_index = true;
3369       } else {
3370         msg = "unhandled input to ConvI2L";
3371       }
3372     } else if (n == head->phi()) {
3373       // no shift, check below for allowed cases
3374       found_index = true;
3375     } else {
3376       msg = "unhandled node in address";
3377       msg_node = n;
3378     }
3379   }
3380 
3381   if (count == -1) {
3382     msg = "malformed address expression";
3383     msg_node = store;
3384   }
3385 
3386   if (!found_index) {
3387     msg = "missing use of index";
3388   }
3389 
3390   // byte sized items won't have a shift
3391   if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
3392     msg = "can't find shift";
3393     msg_node = store;
3394   }
3395 
3396   if (msg != NULL) {
3397 #ifndef PRODUCT
3398     if (TraceOptimizeFill) {
3399       tty->print_cr("not fill intrinsic: %s", msg);
3400       if (msg_node != NULL) msg_node->dump();
3401     }
3402 #endif
3403     return false;
3404   }
3405 
3406   // No make sure all the other nodes in the loop can be handled
3407   VectorSet ok(Thread::current()->resource_area());
3408 
3409   // store related values are ok
3410   ok.set(store->_idx);
3411   ok.set(store->in(MemNode::Memory)->_idx);
3412 
3413   CountedLoopEndNode* loop_exit = head->loopexit();
3414 
3415   // Loop structure is ok
3416   ok.set(head->_idx);
3417   ok.set(loop_exit->_idx);
3418   ok.set(head->phi()->_idx);
3419   ok.set(head->incr()->_idx);
3420   ok.set(loop_exit->cmp_node()->_idx);
3421   ok.set(loop_exit->in(1)->_idx);
3422 
3423   // Address elements are ok
3424   if (con)   ok.set(con->_idx);
3425   if (shift) ok.set(shift->_idx);
3426   if (cast)  ok.set(cast->_idx);
3427   if (conv)  ok.set(conv->_idx);
3428 
3429   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
3430     Node* n = lpt->_body.at(i);
3431     if (n->outcnt() == 0) continue; // Ignore dead
3432     if (ok.test(n->_idx)) continue;
3433     // Backedge projection is ok
3434     if (n->is_IfTrue() && n->in(0) == loop_exit) continue;
3435     if (!n->is_AddP()) {
3436       msg = "unhandled node";
3437       msg_node = n;
3438       break;
3439     }
3440   }
3441 
3442   // Make sure no unexpected values are used outside the loop
3443   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
3444     Node* n = lpt->_body.at(i);
3445     // These values can be replaced with other nodes if they are used
3446     // outside the loop.
3447     if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue;
3448     for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
3449       Node* use = iter.get();
3450       if (!lpt->_body.contains(use)) {
3451         msg = "node is used outside loop";
3452         // lpt->_body.dump();
3453         msg_node = n;
3454         break;
3455       }
3456     }
3457   }
3458 
3459 #ifdef ASSERT
3460   if (TraceOptimizeFill) {
3461     if (msg != NULL) {
3462       tty->print_cr("no fill intrinsic: %s", msg);
3463       if (msg_node != NULL) msg_node->dump();
3464     } else {
3465       tty->print_cr("fill intrinsic for:");
3466     }
3467     store->dump();
3468     if (Verbose) {
3469       lpt->_body.dump();
3470     }
3471   }
3472 #endif
3473 
3474   return msg == NULL;
3475 }
3476 
3477 
3478 
3479 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
3480   // Only for counted inner loops
3481   if (!lpt->is_counted() || !lpt->is_inner()) {
3482     return false;
3483   }
3484 
3485   // Must have constant stride
3486   CountedLoopNode* head = lpt->_head->as_CountedLoop();
3487   if (!head->is_valid_counted_loop() || !head->is_normal_loop()) {
3488     return false;
3489   }
3490 
3491   head->verify_strip_mined(1);
3492 
3493   // Check that the body only contains a store of a loop invariant
3494   // value that is indexed by the loop phi.
3495   Node* store = NULL;
3496   Node* store_value = NULL;
3497   Node* shift = NULL;
3498   Node* offset = NULL;
3499   if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
3500     return false;
3501   }
3502 
3503   Node* exit = head->loopexit()->proj_out_or_null(0);
3504   if (exit == NULL) {
3505     return false;
3506   }
3507 
3508 #ifndef PRODUCT
3509   if (TraceLoopOpts) {
3510     tty->print("ArrayFill    ");
3511     lpt->dump_head();
3512   }
3513 #endif
3514 
3515   // Now replace the whole loop body by a call to a fill routine that
3516   // covers the same region as the loop.
3517   Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
3518 
3519   // Build an expression for the beginning of the copy region
3520   Node* index = head->init_trip();
3521 #ifdef _LP64
3522   index = new ConvI2LNode(index);
3523   _igvn.register_new_node_with_optimizer(index);
3524 #endif
3525   if (shift != NULL) {
3526     // byte arrays don't require a shift but others do.
3527     index = new LShiftXNode(index, shift->in(2));
3528     _igvn.register_new_node_with_optimizer(index);
3529   }
3530   index = new AddPNode(base, base, index);
3531   _igvn.register_new_node_with_optimizer(index);
3532   Node* from = new AddPNode(base, index, offset);
3533   _igvn.register_new_node_with_optimizer(from);
3534   // Compute the number of elements to copy
3535   Node* len = new SubINode(head->limit(), head->init_trip());
3536   _igvn.register_new_node_with_optimizer(len);
3537 
3538   BasicType t = store->as_Mem()->memory_type();
3539   bool aligned = false;
3540   if (offset != NULL && head->init_trip()->is_Con()) {
3541     int element_size = type2aelembytes(t);
3542     aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
3543   }
3544 
3545   // Build a call to the fill routine
3546   const char* fill_name;
3547   address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
3548   assert(fill != NULL, "what?");
3549 
3550   // Convert float/double to int/long for fill routines
3551   if (t == T_FLOAT) {
3552     store_value = new MoveF2INode(store_value);
3553     _igvn.register_new_node_with_optimizer(store_value);
3554   } else if (t == T_DOUBLE) {
3555     store_value = new MoveD2LNode(store_value);
3556     _igvn.register_new_node_with_optimizer(store_value);
3557   }
3558 
3559   Node* mem_phi = store->in(MemNode::Memory);
3560   Node* result_ctrl;
3561   Node* result_mem;
3562   const TypeFunc* call_type = OptoRuntime::array_fill_Type();
3563   CallLeafNode *call = new CallLeafNoFPNode(call_type, fill,
3564                                             fill_name, TypeAryPtr::get_array_body_type(t));
3565   uint cnt = 0;
3566   call->init_req(TypeFunc::Parms + cnt++, from);
3567   call->init_req(TypeFunc::Parms + cnt++, store_value);
3568 #ifdef _LP64
3569   len = new ConvI2LNode(len);
3570   _igvn.register_new_node_with_optimizer(len);
3571 #endif
3572   call->init_req(TypeFunc::Parms + cnt++, len);
3573 #ifdef _LP64
3574   call->init_req(TypeFunc::Parms + cnt++, C->top());
3575 #endif
3576   call->init_req(TypeFunc::Control,   head->init_control());
3577   call->init_req(TypeFunc::I_O,       C->top());       // Does no I/O.
3578   call->init_req(TypeFunc::Memory,    mem_phi->in(LoopNode::EntryControl));
3579   call->init_req(TypeFunc::ReturnAdr, C->start()->proj_out_or_null(TypeFunc::ReturnAdr));
3580   call->init_req(TypeFunc::FramePtr,  C->start()->proj_out_or_null(TypeFunc::FramePtr));
3581   _igvn.register_new_node_with_optimizer(call);
3582   result_ctrl = new ProjNode(call,TypeFunc::Control);
3583   _igvn.register_new_node_with_optimizer(result_ctrl);
3584   result_mem = new ProjNode(call,TypeFunc::Memory);
3585   _igvn.register_new_node_with_optimizer(result_mem);
3586 
3587 /* Disable following optimization until proper fix (add missing checks).
3588 
3589   // If this fill is tightly coupled to an allocation and overwrites
3590   // the whole body, allow it to take over the zeroing.
3591   AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
3592   if (alloc != NULL && alloc->is_AllocateArray()) {
3593     Node* length = alloc->as_AllocateArray()->Ideal_length();
3594     if (head->limit() == length &&
3595         head->init_trip() == _igvn.intcon(0)) {
3596       if (TraceOptimizeFill) {
3597         tty->print_cr("Eliminated zeroing in allocation");
3598       }
3599       alloc->maybe_set_complete(&_igvn);
3600     } else {
3601 #ifdef ASSERT
3602       if (TraceOptimizeFill) {
3603         tty->print_cr("filling array but bounds don't match");
3604         alloc->dump();
3605         head->init_trip()->dump();
3606         head->limit()->dump();
3607         length->dump();
3608       }
3609 #endif
3610     }
3611   }
3612 */
3613 
3614   if (head->is_strip_mined()) {
3615     // Inner strip mined loop goes away so get rid of outer strip
3616     // mined loop
3617     Node* outer_sfpt = head->outer_safepoint();
3618     Node* in = outer_sfpt->in(0);
3619     Node* outer_out = head->outer_loop_exit();
3620     lazy_replace(outer_out, in);
3621     _igvn.replace_input_of(outer_sfpt, 0, C->top());
3622   }
3623 
3624   // Redirect the old control and memory edges that are outside the loop.
3625   // Sometimes the memory phi of the head is used as the outgoing
3626   // state of the loop.  It's safe in this case to replace it with the
3627   // result_mem.
3628   _igvn.replace_node(store->in(MemNode::Memory), result_mem);
3629   lazy_replace(exit, result_ctrl);
3630   _igvn.replace_node(store, result_mem);
3631   // Any uses the increment outside of the loop become the loop limit.
3632   _igvn.replace_node(head->incr(), head->limit());
3633 
3634   // Disconnect the head from the loop.
3635   for (uint i = 0; i < lpt->_body.size(); i++) {
3636     Node* n = lpt->_body.at(i);
3637     _igvn.replace_node(n, C->top());
3638   }
3639 
3640   return true;
3641 }