1 /*
   2  * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "compiler/compileLog.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "opto/addnode.hpp"
  29 #include "opto/callnode.hpp"
  30 #include "opto/connode.hpp"
  31 #include "opto/divnode.hpp"
  32 #include "opto/loopnode.hpp"
  33 #include "opto/mulnode.hpp"
  34 #include "opto/rootnode.hpp"
  35 #include "opto/runtime.hpp"
  36 #include "opto/subnode.hpp"
  37 
  38 //------------------------------is_loop_exit-----------------------------------
  39 // Given an IfNode, return the loop-exiting projection or NULL if both
  40 // arms remain in the loop.
  41 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
  42   if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
  43   PhaseIdealLoop *phase = _phase;
  44   // Test is an IfNode, has 2 projections.  If BOTH are in the loop
  45   // we need loop unswitching instead of peeling.
  46   if( !is_member(phase->get_loop( iff->raw_out(0) )) )
  47     return iff->raw_out(0);
  48   if( !is_member(phase->get_loop( iff->raw_out(1) )) )
  49     return iff->raw_out(1);
  50   return NULL;
  51 }
  52 
  53 
  54 //=============================================================================
  55 
  56 
  57 //------------------------------record_for_igvn----------------------------
  58 // Put loop body on igvn work list
  59 void IdealLoopTree::record_for_igvn() {
  60   for( uint i = 0; i < _body.size(); i++ ) {
  61     Node *n = _body.at(i);
  62     _phase->_igvn._worklist.push(n);
  63   }
  64 }
  65 
  66 //------------------------------compute_exact_trip_count-----------------------
  67 // Compute loop exact trip count if possible. Do not recalculate trip count for
  68 // split loops (pre-main-post) which have their limits and inits behind Opaque node.
  69 void IdealLoopTree::compute_exact_trip_count( PhaseIdealLoop *phase ) {
  70   if (!_head->as_Loop()->is_valid_counted_loop()) {
  71     return;
  72   }
  73   CountedLoopNode* cl = _head->as_CountedLoop();
  74   // Trip count may become nonexact for iteration split loops since
  75   // RCE modifies limits. Note, _trip_count value is not reset since
  76   // it is used to limit unrolling of main loop.
  77   cl->set_nonexact_trip_count();
  78 
  79   // Loop's test should be part of loop.
  80   if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
  81     return; // Infinite loop
  82 
  83 #ifdef ASSERT
  84   BoolTest::mask bt = cl->loopexit()->test_trip();
  85   assert(bt == BoolTest::lt || bt == BoolTest::gt ||
  86          bt == BoolTest::ne, "canonical test is expected");
  87 #endif
  88 
  89   Node* init_n = cl->init_trip();
  90   Node* limit_n = cl->limit();
  91   if (init_n  != NULL &&  init_n->is_Con() &&
  92       limit_n != NULL && limit_n->is_Con()) {
  93     // Use longs to avoid integer overflow.
  94     int stride_con  = cl->stride_con();
  95     jlong init_con   = cl->init_trip()->get_int();
  96     jlong limit_con  = cl->limit()->get_int();
  97     int stride_m    = stride_con - (stride_con > 0 ? 1 : -1);
  98     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
  99     if (trip_count > 0 && (julong)trip_count < (julong)max_juint) {
 100       // Set exact trip count.
 101       cl->set_exact_trip_count((uint)trip_count);
 102     }
 103   }
 104 }
 105 
 106 //------------------------------compute_profile_trip_cnt----------------------------
 107 // Compute loop trip count from profile data as
 108 //    (backedge_count + loop_exit_count) / loop_exit_count
 109 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
 110   if (!_head->is_CountedLoop()) {
 111     return;
 112   }
 113   CountedLoopNode* head = _head->as_CountedLoop();
 114   if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
 115     return; // Already computed
 116   }
 117   float trip_cnt = (float)max_jint; // default is big
 118 
 119   Node* back = head->in(LoopNode::LoopBackControl);
 120   while (back != head) {
 121     if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
 122         back->in(0) &&
 123         back->in(0)->is_If() &&
 124         back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
 125         back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
 126       break;
 127     }
 128     back = phase->idom(back);
 129   }
 130   if (back != head) {
 131     assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
 132            back->in(0), "if-projection exists");
 133     IfNode* back_if = back->in(0)->as_If();
 134     float loop_back_cnt = back_if->_fcnt * back_if->_prob;
 135 
 136     // Now compute a loop exit count
 137     float loop_exit_cnt = 0.0f;
 138     for( uint i = 0; i < _body.size(); i++ ) {
 139       Node *n = _body[i];
 140       if( n->is_If() ) {
 141         IfNode *iff = n->as_If();
 142         if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
 143           Node *exit = is_loop_exit(iff);
 144           if( exit ) {
 145             float exit_prob = iff->_prob;
 146             if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
 147             if (exit_prob > PROB_MIN) {
 148               float exit_cnt = iff->_fcnt * exit_prob;
 149               loop_exit_cnt += exit_cnt;
 150             }
 151           }
 152         }
 153       }
 154     }
 155     if (loop_exit_cnt > 0.0f) {
 156       trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
 157     } else {
 158       // No exit count so use
 159       trip_cnt = loop_back_cnt;
 160     }
 161   }
 162 #ifndef PRODUCT
 163   if (TraceProfileTripCount) {
 164     tty->print_cr("compute_profile_trip_cnt  lp: %d cnt: %f\n", head->_idx, trip_cnt);
 165   }
 166 #endif
 167   head->set_profile_trip_cnt(trip_cnt);
 168 }
 169 
 170 //---------------------is_invariant_addition-----------------------------
 171 // Return nonzero index of invariant operand for an Add or Sub
 172 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
 173 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
 174   int op = n->Opcode();
 175   if (op == Op_AddI || op == Op_SubI) {
 176     bool in1_invar = this->is_invariant(n->in(1));
 177     bool in2_invar = this->is_invariant(n->in(2));
 178     if (in1_invar && !in2_invar) return 1;
 179     if (!in1_invar && in2_invar) return 2;
 180   }
 181   return 0;
 182 }
 183 
 184 //---------------------reassociate_add_sub-----------------------------
 185 // Reassociate invariant add and subtract expressions:
 186 //
 187 // inv1 + (x + inv2)  =>  ( inv1 + inv2) + x
 188 // (x + inv2) + inv1  =>  ( inv1 + inv2) + x
 189 // inv1 + (x - inv2)  =>  ( inv1 - inv2) + x
 190 // inv1 - (inv2 - x)  =>  ( inv1 - inv2) + x
 191 // (x + inv2) - inv1  =>  (-inv1 + inv2) + x
 192 // (x - inv2) + inv1  =>  ( inv1 - inv2) + x
 193 // (x - inv2) - inv1  =>  (-inv1 - inv2) + x
 194 // inv1 + (inv2 - x)  =>  ( inv1 + inv2) - x
 195 // inv1 - (x - inv2)  =>  ( inv1 + inv2) - x
 196 // (inv2 - x) + inv1  =>  ( inv1 + inv2) - x
 197 // (inv2 - x) - inv1  =>  (-inv1 + inv2) - x
 198 // inv1 - (x + inv2)  =>  ( inv1 - inv2) - x
 199 //
 200 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
 201   if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
 202   if (is_invariant(n1)) return NULL;
 203   int inv1_idx = is_invariant_addition(n1, phase);
 204   if (!inv1_idx) return NULL;
 205   // Don't mess with add of constant (igvn moves them to expression tree root.)
 206   if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
 207   Node* inv1 = n1->in(inv1_idx);
 208   Node* n2 = n1->in(3 - inv1_idx);
 209   int inv2_idx = is_invariant_addition(n2, phase);
 210   if (!inv2_idx) return NULL;
 211   Node* x    = n2->in(3 - inv2_idx);
 212   Node* inv2 = n2->in(inv2_idx);
 213 
 214   bool neg_x    = n2->is_Sub() && inv2_idx == 1;
 215   bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
 216   bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
 217   if (n1->is_Sub() && inv1_idx == 1) {
 218     neg_x    = !neg_x;
 219     neg_inv2 = !neg_inv2;
 220   }
 221   Node* inv1_c = phase->get_ctrl(inv1);
 222   Node* inv2_c = phase->get_ctrl(inv2);
 223   Node* n_inv1;
 224   if (neg_inv1) {
 225     Node *zero = phase->_igvn.intcon(0);
 226     phase->set_ctrl(zero, phase->C->root());
 227     n_inv1 = new (phase->C) SubINode(zero, inv1);
 228     phase->register_new_node(n_inv1, inv1_c);
 229   } else {
 230     n_inv1 = inv1;
 231   }
 232   Node* inv;
 233   if (neg_inv2) {
 234     inv = new (phase->C) SubINode(n_inv1, inv2);
 235   } else {
 236     inv = new (phase->C) AddINode(n_inv1, inv2);
 237   }
 238   phase->register_new_node(inv, phase->get_early_ctrl(inv));
 239 
 240   Node* addx;
 241   if (neg_x) {
 242     addx = new (phase->C) SubINode(inv, x);
 243   } else {
 244     addx = new (phase->C) AddINode(x, inv);
 245   }
 246   phase->register_new_node(addx, phase->get_ctrl(x));
 247   phase->_igvn.replace_node(n1, addx);
 248   assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
 249   _body.yank(n1);
 250   return addx;
 251 }
 252 
 253 //---------------------reassociate_invariants-----------------------------
 254 // Reassociate invariant expressions:
 255 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
 256   for (int i = _body.size() - 1; i >= 0; i--) {
 257     Node *n = _body.at(i);
 258     for (int j = 0; j < 5; j++) {
 259       Node* nn = reassociate_add_sub(n, phase);
 260       if (nn == NULL) break;
 261       n = nn; // again
 262     };
 263   }
 264 }
 265 
 266 //------------------------------policy_peeling---------------------------------
 267 // Return TRUE or FALSE if the loop should be peeled or not.  Peel if we can
 268 // make some loop-invariant test (usually a null-check) happen before the loop.
 269 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
 270   Node *test = ((IdealLoopTree*)this)->tail();
 271   int  body_size = ((IdealLoopTree*)this)->_body.size();
 272   int  live_node_count = phase->C->live_nodes();
 273   // Peeling does loop cloning which can result in O(N^2) node construction
 274   if( body_size > 255 /* Prevent overflow for large body_size */
 275       || (body_size * body_size + live_node_count > MaxNodeLimit) ) {
 276     return false;           // too large to safely clone
 277   }
 278   while( test != _head ) {      // Scan till run off top of loop
 279     if( test->is_If() ) {       // Test?
 280       Node *ctrl = phase->get_ctrl(test->in(1));
 281       if (ctrl->is_top())
 282         return false;           // Found dead test on live IF?  No peeling!
 283       // Standard IF only has one input value to check for loop invariance
 284       assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
 285       // Condition is not a member of this loop?
 286       if( !is_member(phase->get_loop(ctrl)) &&
 287           is_loop_exit(test) )
 288         return true;            // Found reason to peel!
 289     }
 290     // Walk up dominators to loop _head looking for test which is
 291     // executed on every path thru loop.
 292     test = phase->idom(test);
 293   }
 294   return false;
 295 }
 296 
 297 //------------------------------peeled_dom_test_elim---------------------------
 298 // If we got the effect of peeling, either by actually peeling or by making
 299 // a pre-loop which must execute at least once, we can remove all
 300 // loop-invariant dominated tests in the main body.
 301 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
 302   bool progress = true;
 303   while( progress ) {
 304     progress = false;           // Reset for next iteration
 305     Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
 306     Node *test = prev->in(0);
 307     while( test != loop->_head ) { // Scan till run off top of loop
 308 
 309       int p_op = prev->Opcode();
 310       if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
 311           test->is_If() &&      // Test?
 312           !test->in(1)->is_Con() && // And not already obvious?
 313           // Condition is not a member of this loop?
 314           !loop->is_member(get_loop(get_ctrl(test->in(1))))){
 315         // Walk loop body looking for instances of this test
 316         for( uint i = 0; i < loop->_body.size(); i++ ) {
 317           Node *n = loop->_body.at(i);
 318           if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
 319             // IfNode was dominated by version in peeled loop body
 320             progress = true;
 321             dominated_by( old_new[prev->_idx], n );
 322           }
 323         }
 324       }
 325       prev = test;
 326       test = idom(test);
 327     } // End of scan tests in loop
 328 
 329   } // End of while( progress )
 330 }
 331 
 332 //------------------------------do_peeling-------------------------------------
 333 // Peel the first iteration of the given loop.
 334 // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 335 //         The pre-loop illegally has 2 control users (old & new loops).
 336 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 337 //         Do this by making the old-loop fall-in edges act as if they came
 338 //         around the loopback from the prior iteration (follow the old-loop
 339 //         backedges) and then map to the new peeled iteration.  This leaves
 340 //         the pre-loop with only 1 user (the new peeled iteration), but the
 341 //         peeled-loop backedge has 2 users.
 342 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 343 //         extra backedge user.
 344 //
 345 //                   orig
 346 //
 347 //                  stmt1
 348 //                    |
 349 //                    v
 350 //              loop predicate
 351 //                    |
 352 //                    v
 353 //                   loop<----+
 354 //                     |      |
 355 //                   stmt2    |
 356 //                     |      |
 357 //                     v      |
 358 //                    if      ^
 359 //                   / \      |
 360 //                  /   \     |
 361 //                 v     v    |
 362 //               false true   |
 363 //               /       \    |
 364 //              /         ----+
 365 //             |
 366 //             v
 367 //           exit
 368 //
 369 //
 370 //            after clone loop
 371 //
 372 //                   stmt1
 373 //                     |
 374 //                     v
 375 //               loop predicate
 376 //                 /       \
 377 //        clone   /         \   orig
 378 //               /           \
 379 //              /             \
 380 //             v               v
 381 //   +---->loop clone          loop<----+
 382 //   |      |                    |      |
 383 //   |    stmt2 clone          stmt2    |
 384 //   |      |                    |      |
 385 //   |      v                    v      |
 386 //   ^      if clone            If      ^
 387 //   |      / \                / \      |
 388 //   |     /   \              /   \     |
 389 //   |    v     v            v     v    |
 390 //   |    true  false      false true   |
 391 //   |    /         \      /       \    |
 392 //   +----           \    /         ----+
 393 //                    \  /
 394 //                    1v v2
 395 //                  region
 396 //                     |
 397 //                     v
 398 //                   exit
 399 //
 400 //
 401 //         after peel and predicate move
 402 //
 403 //                   stmt1
 404 //                    /
 405 //                   /
 406 //        clone     /            orig
 407 //                 /
 408 //                /              +----------+
 409 //               /               |          |
 410 //              /          loop predicate   |
 411 //             /                 |          |
 412 //            v                  v          |
 413 //   TOP-->loop clone          loop<----+   |
 414 //          |                    |      |   |
 415 //        stmt2 clone          stmt2    |   |
 416 //          |                    |      |   ^
 417 //          v                    v      |   |
 418 //          if clone            If      ^   |
 419 //          / \                / \      |   |
 420 //         /   \              /   \     |   |
 421 //        v     v            v     v    |   |
 422 //      true   false      false  true   |   |
 423 //        |         \      /       \    |   |
 424 //        |          \    /         ----+   ^
 425 //        |           \  /                  |
 426 //        |           1v v2                 |
 427 //        v         region                  |
 428 //        |            |                    |
 429 //        |            v                    |
 430 //        |          exit                   |
 431 //        |                                 |
 432 //        +--------------->-----------------+
 433 //
 434 //
 435 //              final graph
 436 //
 437 //                  stmt1
 438 //                    |
 439 //                    v
 440 //                  stmt2 clone
 441 //                    |
 442 //                    v
 443 //                   if clone
 444 //                  / |
 445 //                 /  |
 446 //                v   v
 447 //            false  true
 448 //             |      |
 449 //             |      v
 450 //             | loop predicate
 451 //             |      |
 452 //             |      v
 453 //             |     loop<----+
 454 //             |      |       |
 455 //             |    stmt2     |
 456 //             |      |       |
 457 //             |      v       |
 458 //             v      if      ^
 459 //             |     /  \     |
 460 //             |    /    \    |
 461 //             |   v     v    |
 462 //             | false  true  |
 463 //             |  |        \  |
 464 //             v  v         --+
 465 //            region
 466 //              |
 467 //              v
 468 //             exit
 469 //
 470 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
 471 
 472   C->set_major_progress();
 473   // Peeling a 'main' loop in a pre/main/post situation obfuscates the
 474   // 'pre' loop from the main and the 'pre' can no longer have it's
 475   // iterations adjusted.  Therefore, we need to declare this loop as
 476   // no longer a 'main' loop; it will need new pre and post loops before
 477   // we can do further RCE.
 478 #ifndef PRODUCT
 479   if (TraceLoopOpts) {
 480     tty->print("Peel         ");
 481     loop->dump_head();
 482   }
 483 #endif
 484   Node* head = loop->_head;
 485   bool counted_loop = head->is_CountedLoop();
 486   if (counted_loop) {
 487     CountedLoopNode *cl = head->as_CountedLoop();
 488     assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
 489     cl->set_trip_count(cl->trip_count() - 1);
 490     if (cl->is_main_loop()) {
 491       cl->set_normal_loop();
 492 #ifndef PRODUCT
 493       if (PrintOpto && VerifyLoopOptimizations) {
 494         tty->print("Peeling a 'main' loop; resetting to 'normal' ");
 495         loop->dump_head();
 496       }
 497 #endif
 498     }
 499   }
 500   Node* entry = head->in(LoopNode::EntryControl);
 501 
 502   // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 503   //         The pre-loop illegally has 2 control users (old & new loops).
 504   clone_loop( loop, old_new, dom_depth(head) );
 505 
 506   // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 507   //         Do this by making the old-loop fall-in edges act as if they came
 508   //         around the loopback from the prior iteration (follow the old-loop
 509   //         backedges) and then map to the new peeled iteration.  This leaves
 510   //         the pre-loop with only 1 user (the new peeled iteration), but the
 511   //         peeled-loop backedge has 2 users.
 512   Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx];
 513   _igvn.hash_delete(head);
 514   head->set_req(LoopNode::EntryControl, new_entry);
 515   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
 516     Node* old = head->fast_out(j);
 517     if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
 518       Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
 519       if (!new_exit_value )     // Backedge value is ALSO loop invariant?
 520         // Then loop body backedge value remains the same.
 521         new_exit_value = old->in(LoopNode::LoopBackControl);
 522       _igvn.hash_delete(old);
 523       old->set_req(LoopNode::EntryControl, new_exit_value);
 524     }
 525   }
 526 
 527 
 528   // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 529   //         extra backedge user.
 530   Node* new_head = old_new[head->_idx];
 531   _igvn.hash_delete(new_head);
 532   new_head->set_req(LoopNode::LoopBackControl, C->top());
 533   for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
 534     Node* use = new_head->fast_out(j2);
 535     if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
 536       _igvn.hash_delete(use);
 537       use->set_req(LoopNode::LoopBackControl, C->top());
 538     }
 539   }
 540 
 541 
 542   // Step 4: Correct dom-depth info.  Set to loop-head depth.
 543   int dd = dom_depth(head);
 544   set_idom(head, head->in(1), dd);
 545   for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
 546     Node *old = loop->_body.at(j3);
 547     Node *nnn = old_new[old->_idx];
 548     if (!has_ctrl(nnn))
 549       set_idom(nnn, idom(nnn), dd-1);
 550   }
 551 
 552   // Now force out all loop-invariant dominating tests.  The optimizer
 553   // finds some, but we _know_ they are all useless.
 554   peeled_dom_test_elim(loop,old_new);
 555 
 556   loop->record_for_igvn();
 557 }
 558 
 559 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop
 560 
 561 //------------------------------policy_maximally_unroll------------------------
 562 // Calculate exact loop trip count and return true if loop can be maximally
 563 // unrolled.
 564 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
 565   CountedLoopNode *cl = _head->as_CountedLoop();
 566   assert(cl->is_normal_loop(), "");
 567   if (!cl->is_valid_counted_loop())
 568     return false; // Malformed counted loop
 569 
 570   if (!cl->has_exact_trip_count()) {
 571     // Trip count is not exact.
 572     return false;
 573   }
 574 
 575   uint trip_count = cl->trip_count();
 576   // Note, max_juint is used to indicate unknown trip count.
 577   assert(trip_count > 1, "one iteration loop should be optimized out already");
 578   assert(trip_count < max_juint, "exact trip_count should be less than max_uint.");
 579 
 580   // Real policy: if we maximally unroll, does it get too big?
 581   // Allow the unrolled mess to get larger than standard loop
 582   // size.  After all, it will no longer be a loop.
 583   uint body_size    = _body.size();
 584   uint unroll_limit = (uint)LoopUnrollLimit * 4;
 585   assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
 586   if (trip_count > unroll_limit || body_size > unroll_limit) {
 587     return false;
 588   }
 589 
 590   // Fully unroll a loop with few iterations regardless next
 591   // conditions since following loop optimizations will split
 592   // such loop anyway (pre-main-post).
 593   if (trip_count <= 3)
 594     return true;
 595 
 596   // Take into account that after unroll conjoined heads and tails will fold,
 597   // otherwise policy_unroll() may allow more unrolling than max unrolling.
 598   uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count;
 599   uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE;
 600   if (body_size != tst_body_size) // Check for int overflow
 601     return false;
 602   if (new_body_size > unroll_limit ||
 603       // Unrolling can result in a large amount of node construction
 604       new_body_size >= MaxNodeLimit - (uint) phase->C->live_nodes()) {
 605     return false;
 606   }
 607 
 608   // Do not unroll a loop with String intrinsics code.
 609   // String intrinsics are large and have loops.
 610   for (uint k = 0; k < _body.size(); k++) {
 611     Node* n = _body.at(k);
 612     switch (n->Opcode()) {
 613       case Op_StrComp:
 614       case Op_StrEquals:
 615       case Op_StrIndexOf:
 616       case Op_EncodeISOArray:
 617       case Op_AryEq: {
 618         return false;
 619       }
 620 #if INCLUDE_RTM_OPT
 621       case Op_FastLock:
 622       case Op_FastUnlock: {
 623         // Don't unroll RTM locking code because it is large.
 624         if (UseRTMLocking) {
 625           return false;
 626         }
 627       }
 628 #endif
 629     } // switch
 630   }
 631 
 632   return true; // Do maximally unroll
 633 }
 634 
 635 
 636 //------------------------------policy_unroll----------------------------------
 637 // Return TRUE or FALSE if the loop should be unrolled or not.  Unroll if
 638 // the loop is a CountedLoop and the body is small enough.
 639 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
 640 
 641   CountedLoopNode *cl = _head->as_CountedLoop();
 642   assert(cl->is_normal_loop() || cl->is_main_loop(), "");
 643 
 644   if (!cl->is_valid_counted_loop())
 645     return false; // Malformed counted loop
 646 
 647   // Protect against over-unrolling.
 648   // After split at least one iteration will be executed in pre-loop.
 649   if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false;
 650 
 651   int future_unroll_ct = cl->unrolled_count() * 2;
 652   if (future_unroll_ct > LoopMaxUnroll) return false;
 653 
 654   // Check for initial stride being a small enough constant
 655   if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false;
 656 
 657   // Don't unroll if the next round of unrolling would push us
 658   // over the expected trip count of the loop.  One is subtracted
 659   // from the expected trip count because the pre-loop normally
 660   // executes 1 iteration.
 661   if (UnrollLimitForProfileCheck > 0 &&
 662       cl->profile_trip_cnt() != COUNT_UNKNOWN &&
 663       future_unroll_ct        > UnrollLimitForProfileCheck &&
 664       (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
 665     return false;
 666   }
 667 
 668   // When unroll count is greater than LoopUnrollMin, don't unroll if:
 669   //   the residual iterations are more than 10% of the trip count
 670   //   and rounds of "unroll,optimize" are not making significant progress
 671   //   Progress defined as current size less than 20% larger than previous size.
 672   if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
 673       future_unroll_ct > LoopUnrollMin &&
 674       (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() &&
 675       1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
 676     return false;
 677   }
 678 
 679   Node *init_n = cl->init_trip();
 680   Node *limit_n = cl->limit();
 681   int stride_con = cl->stride_con();
 682   // Non-constant bounds.
 683   // Protect against over-unrolling when init or/and limit are not constant
 684   // (so that trip_count's init value is maxint) but iv range is known.
 685   if (init_n   == NULL || !init_n->is_Con()  ||
 686       limit_n  == NULL || !limit_n->is_Con()) {
 687     Node* phi = cl->phi();
 688     if (phi != NULL) {
 689       assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
 690       const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
 691       int next_stride = stride_con * 2; // stride after this unroll
 692       if (next_stride > 0) {
 693         if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
 694             iv_type->_lo + next_stride >  iv_type->_hi) {
 695           return false;  // over-unrolling
 696         }
 697       } else if (next_stride < 0) {
 698         if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
 699             iv_type->_hi + next_stride <  iv_type->_lo) {
 700           return false;  // over-unrolling
 701         }
 702       }
 703     }
 704   }
 705 
 706   // After unroll limit will be adjusted: new_limit = limit-stride.
 707   // Bailout if adjustment overflow.
 708   const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
 709   if (stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi) ||
 710       stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo))
 711     return false;  // overflow
 712 
 713   // Adjust body_size to determine if we unroll or not
 714   uint body_size = _body.size();
 715   // Key test to unroll loop in CRC32 java code
 716   int xors_in_loop = 0;
 717   // Also count ModL, DivL and MulL which expand mightly
 718   for (uint k = 0; k < _body.size(); k++) {
 719     Node* n = _body.at(k);
 720     switch (n->Opcode()) {
 721       case Op_XorI: xors_in_loop++; break; // CRC32 java code
 722       case Op_ModL: body_size += 30; break;
 723       case Op_DivL: body_size += 30; break;
 724       case Op_MulL: body_size += 10; break;
 725       case Op_StrComp:
 726       case Op_StrEquals:
 727       case Op_StrIndexOf:
 728       case Op_EncodeISOArray:
 729       case Op_AryEq: {
 730         // Do not unroll a loop with String intrinsics code.
 731         // String intrinsics are large and have loops.
 732         return false;
 733       }
 734 #if INCLUDE_RTM_OPT
 735       case Op_FastLock:
 736       case Op_FastUnlock: {
 737         // Don't unroll RTM locking code because it is large.
 738         if (UseRTMLocking) {
 739           return false;
 740         }
 741       }
 742 #endif
 743     } // switch
 744   }
 745 
 746   // Check for being too big
 747   if (body_size > (uint)LoopUnrollLimit) {
 748     if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
 749     // Normal case: loop too big
 750     return false;
 751   }
 752 
 753   // Unroll once!  (Each trip will soon do double iterations)
 754   return true;
 755 }
 756 
 757 //------------------------------policy_align-----------------------------------
 758 // Return TRUE or FALSE if the loop should be cache-line aligned.  Gather the
 759 // expression that does the alignment.  Note that only one array base can be
 760 // aligned in a loop (unless the VM guarantees mutual alignment).  Note that
 761 // if we vectorize short memory ops into longer memory ops, we may want to
 762 // increase alignment.
 763 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
 764   return false;
 765 }
 766 
 767 //------------------------------policy_range_check-----------------------------
 768 // Return TRUE or FALSE if the loop should be range-check-eliminated.
 769 // Actually we do iteration-splitting, a more powerful form of RCE.
 770 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
 771   if (!RangeCheckElimination) return false;
 772 
 773   CountedLoopNode *cl = _head->as_CountedLoop();
 774   // If we unrolled with no intention of doing RCE and we later
 775   // changed our minds, we got no pre-loop.  Either we need to
 776   // make a new pre-loop, or we gotta disallow RCE.
 777   if (cl->is_main_no_pre_loop()) return false; // Disallowed for now.
 778   Node *trip_counter = cl->phi();
 779 
 780   // Check loop body for tests of trip-counter plus loop-invariant vs
 781   // loop-invariant.
 782   for (uint i = 0; i < _body.size(); i++) {
 783     Node *iff = _body[i];
 784     if (iff->Opcode() == Op_If) { // Test?
 785 
 786       // Comparing trip+off vs limit
 787       Node *bol = iff->in(1);
 788       if (bol->req() != 2) continue; // dead constant test
 789       if (!bol->is_Bool()) {
 790         assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
 791         continue;
 792       }
 793       if (bol->as_Bool()->_test._test == BoolTest::ne)
 794         continue; // not RC
 795 
 796       Node *cmp = bol->in(1);
 797       Node *rc_exp = cmp->in(1);
 798       Node *limit = cmp->in(2);
 799 
 800       Node *limit_c = phase->get_ctrl(limit);
 801       if( limit_c == phase->C->top() )
 802         return false;           // Found dead test on live IF?  No RCE!
 803       if( is_member(phase->get_loop(limit_c) ) ) {
 804         // Compare might have operands swapped; commute them
 805         rc_exp = cmp->in(2);
 806         limit  = cmp->in(1);
 807         limit_c = phase->get_ctrl(limit);
 808         if( is_member(phase->get_loop(limit_c) ) )
 809           continue;             // Both inputs are loop varying; cannot RCE
 810       }
 811 
 812       if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
 813         continue;
 814       }
 815       // Yeah!  Found a test like 'trip+off vs limit'
 816       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
 817       // we need loop unswitching instead of iteration splitting.
 818       if( is_loop_exit(iff) )
 819         return true;            // Found reason to split iterations
 820     } // End of is IF
 821   }
 822 
 823   return false;
 824 }
 825 
 826 //------------------------------policy_peel_only-------------------------------
 827 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned.  Useful
 828 // for unrolling loops with NO array accesses.
 829 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
 830 
 831   for( uint i = 0; i < _body.size(); i++ )
 832     if( _body[i]->is_Mem() )
 833       return false;
 834 
 835   // No memory accesses at all!
 836   return true;
 837 }
 838 
 839 //------------------------------clone_up_backedge_goo--------------------------
 840 // If Node n lives in the back_ctrl block and cannot float, we clone a private
 841 // version of n in preheader_ctrl block and return that, otherwise return n.
 842 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) {
 843   if( get_ctrl(n) != back_ctrl ) return n;
 844 
 845   // Only visit once
 846   if (visited.test_set(n->_idx)) {
 847     Node *x = clones.find(n->_idx);
 848     if (x != NULL)
 849       return x;
 850     return n;
 851   }
 852 
 853   Node *x = NULL;               // If required, a clone of 'n'
 854   // Check for 'n' being pinned in the backedge.
 855   if( n->in(0) && n->in(0) == back_ctrl ) {
 856     assert(clones.find(n->_idx) == NULL, "dead loop");
 857     x = n->clone();             // Clone a copy of 'n' to preheader
 858     clones.push(x, n->_idx);
 859     x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
 860   }
 861 
 862   // Recursive fixup any other input edges into x.
 863   // If there are no changes we can just return 'n', otherwise
 864   // we need to clone a private copy and change it.
 865   for( uint i = 1; i < n->req(); i++ ) {
 866     Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones );
 867     if( g != n->in(i) ) {
 868       if( !x ) {
 869         assert(clones.find(n->_idx) == NULL, "dead loop");
 870         x = n->clone();
 871         clones.push(x, n->_idx);
 872       }
 873       x->set_req(i, g);
 874     }
 875   }
 876   if( x ) {                     // x can legally float to pre-header location
 877     register_new_node( x, preheader_ctrl );
 878     return x;
 879   } else {                      // raise n to cover LCA of uses
 880     set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
 881   }
 882   return n;
 883 }
 884 
 885 //------------------------------insert_pre_post_loops--------------------------
 886 // Insert pre and post loops.  If peel_only is set, the pre-loop can not have
 887 // more iterations added.  It acts as a 'peel' only, no lower-bound RCE, no
 888 // alignment.  Useful to unroll loops that do no array accesses.
 889 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
 890 
 891 #ifndef PRODUCT
 892   if (TraceLoopOpts) {
 893     if (peel_only)
 894       tty->print("PeelMainPost ");
 895     else
 896       tty->print("PreMainPost  ");
 897     loop->dump_head();
 898   }
 899 #endif
 900   C->set_major_progress();
 901 
 902   // Find common pieces of the loop being guarded with pre & post loops
 903   CountedLoopNode *main_head = loop->_head->as_CountedLoop();
 904   assert( main_head->is_normal_loop(), "" );
 905   CountedLoopEndNode *main_end = main_head->loopexit();
 906   guarantee(main_end != NULL, "no loop exit node");
 907   assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
 908   uint dd_main_head = dom_depth(main_head);
 909   uint max = main_head->outcnt();
 910 
 911   Node *pre_header= main_head->in(LoopNode::EntryControl);
 912   Node *init      = main_head->init_trip();
 913   Node *incr      = main_end ->incr();
 914   Node *limit     = main_end ->limit();
 915   Node *stride    = main_end ->stride();
 916   Node *cmp       = main_end ->cmp_node();
 917   BoolTest::mask b_test = main_end->test_trip();
 918 
 919   // Need only 1 user of 'bol' because I will be hacking the loop bounds.
 920   Node *bol = main_end->in(CountedLoopEndNode::TestValue);
 921   if( bol->outcnt() != 1 ) {
 922     bol = bol->clone();
 923     register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
 924     _igvn.hash_delete(main_end);
 925     main_end->set_req(CountedLoopEndNode::TestValue, bol);
 926   }
 927   // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
 928   if( cmp->outcnt() != 1 ) {
 929     cmp = cmp->clone();
 930     register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
 931     _igvn.hash_delete(bol);
 932     bol->set_req(1, cmp);
 933   }
 934 
 935   //------------------------------
 936   // Step A: Create Post-Loop.
 937   Node* main_exit = main_end->proj_out(false);
 938   assert( main_exit->Opcode() == Op_IfFalse, "" );
 939   int dd_main_exit = dom_depth(main_exit);
 940 
 941   // Step A1: Clone the loop body.  The clone becomes the post-loop.  The main
 942   // loop pre-header illegally has 2 control users (old & new loops).
 943   clone_loop( loop, old_new, dd_main_exit );
 944   assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
 945   CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
 946   post_head->set_post_loop(main_head);
 947 
 948   // Reduce the post-loop trip count.
 949   CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
 950   post_end->_prob = PROB_FAIR;
 951 
 952   // Build the main-loop normal exit.
 953   IfFalseNode *new_main_exit = new (C) IfFalseNode(main_end);
 954   _igvn.register_new_node_with_optimizer( new_main_exit );
 955   set_idom(new_main_exit, main_end, dd_main_exit );
 956   set_loop(new_main_exit, loop->_parent);
 957 
 958   // Step A2: Build a zero-trip guard for the post-loop.  After leaving the
 959   // main-loop, the post-loop may not execute at all.  We 'opaque' the incr
 960   // (the main-loop trip-counter exit value) because we will be changing
 961   // the exit value (via unrolling) so we cannot constant-fold away the zero
 962   // trip guard until all unrolling is done.
 963   Node *zer_opaq = new (C) Opaque1Node(C, incr);
 964   Node *zer_cmp  = new (C) CmpINode( zer_opaq, limit );
 965   Node *zer_bol  = new (C) BoolNode( zer_cmp, b_test );
 966   register_new_node( zer_opaq, new_main_exit );
 967   register_new_node( zer_cmp , new_main_exit );
 968   register_new_node( zer_bol , new_main_exit );
 969 
 970   // Build the IfNode
 971   IfNode *zer_iff = new (C) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
 972   _igvn.register_new_node_with_optimizer( zer_iff );
 973   set_idom(zer_iff, new_main_exit, dd_main_exit);
 974   set_loop(zer_iff, loop->_parent);
 975 
 976   // Plug in the false-path, taken if we need to skip post-loop
 977   _igvn.replace_input_of(main_exit, 0, zer_iff);
 978   set_idom(main_exit, zer_iff, dd_main_exit);
 979   set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
 980   // Make the true-path, must enter the post loop
 981   Node *zer_taken = new (C) IfTrueNode( zer_iff );
 982   _igvn.register_new_node_with_optimizer( zer_taken );
 983   set_idom(zer_taken, zer_iff, dd_main_exit);
 984   set_loop(zer_taken, loop->_parent);
 985   // Plug in the true path
 986   _igvn.hash_delete( post_head );
 987   post_head->set_req(LoopNode::EntryControl, zer_taken);
 988   set_idom(post_head, zer_taken, dd_main_exit);
 989 
 990   Arena *a = Thread::current()->resource_area();
 991   VectorSet visited(a);
 992   Node_Stack clones(a, main_head->back_control()->outcnt());
 993   // Step A3: Make the fall-in values to the post-loop come from the
 994   // fall-out values of the main-loop.
 995   for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
 996     Node* main_phi = main_head->fast_out(i);
 997     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
 998       Node *post_phi = old_new[main_phi->_idx];
 999       Node *fallmain  = clone_up_backedge_goo(main_head->back_control(),
1000                                               post_head->init_control(),
1001                                               main_phi->in(LoopNode::LoopBackControl),
1002                                               visited, clones);
1003       _igvn.hash_delete(post_phi);
1004       post_phi->set_req( LoopNode::EntryControl, fallmain );
1005     }
1006   }
1007 
1008   // Update local caches for next stanza
1009   main_exit = new_main_exit;
1010 
1011 
1012   //------------------------------
1013   // Step B: Create Pre-Loop.
1014 
1015   // Step B1: Clone the loop body.  The clone becomes the pre-loop.  The main
1016   // loop pre-header illegally has 2 control users (old & new loops).
1017   clone_loop( loop, old_new, dd_main_head );
1018   CountedLoopNode*    pre_head = old_new[main_head->_idx]->as_CountedLoop();
1019   CountedLoopEndNode* pre_end  = old_new[main_end ->_idx]->as_CountedLoopEnd();
1020   pre_head->set_pre_loop(main_head);
1021   Node *pre_incr = old_new[incr->_idx];
1022 
1023   // Reduce the pre-loop trip count.
1024   pre_end->_prob = PROB_FAIR;
1025 
1026   // Find the pre-loop normal exit.
1027   Node* pre_exit = pre_end->proj_out(false);
1028   assert( pre_exit->Opcode() == Op_IfFalse, "" );
1029   IfFalseNode *new_pre_exit = new (C) IfFalseNode(pre_end);
1030   _igvn.register_new_node_with_optimizer( new_pre_exit );
1031   set_idom(new_pre_exit, pre_end, dd_main_head);
1032   set_loop(new_pre_exit, loop->_parent);
1033 
1034   // Step B2: Build a zero-trip guard for the main-loop.  After leaving the
1035   // pre-loop, the main-loop may not execute at all.  Later in life this
1036   // zero-trip guard will become the minimum-trip guard when we unroll
1037   // the main-loop.
1038   Node *min_opaq = new (C) Opaque1Node(C, limit);
1039   Node *min_cmp  = new (C) CmpINode( pre_incr, min_opaq );
1040   Node *min_bol  = new (C) BoolNode( min_cmp, b_test );
1041   register_new_node( min_opaq, new_pre_exit );
1042   register_new_node( min_cmp , new_pre_exit );
1043   register_new_node( min_bol , new_pre_exit );
1044 
1045   // Build the IfNode (assume the main-loop is executed always).
1046   IfNode *min_iff = new (C) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
1047   _igvn.register_new_node_with_optimizer( min_iff );
1048   set_idom(min_iff, new_pre_exit, dd_main_head);
1049   set_loop(min_iff, loop->_parent);
1050 
1051   // Plug in the false-path, taken if we need to skip main-loop
1052   _igvn.hash_delete( pre_exit );
1053   pre_exit->set_req(0, min_iff);
1054   set_idom(pre_exit, min_iff, dd_main_head);
1055   set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
1056   // Make the true-path, must enter the main loop
1057   Node *min_taken = new (C) IfTrueNode( min_iff );
1058   _igvn.register_new_node_with_optimizer( min_taken );
1059   set_idom(min_taken, min_iff, dd_main_head);
1060   set_loop(min_taken, loop->_parent);
1061   // Plug in the true path
1062   _igvn.hash_delete( main_head );
1063   main_head->set_req(LoopNode::EntryControl, min_taken);
1064   set_idom(main_head, min_taken, dd_main_head);
1065 
1066   visited.Clear();
1067   clones.clear();
1068   // Step B3: Make the fall-in values to the main-loop come from the
1069   // fall-out values of the pre-loop.
1070   for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
1071     Node* main_phi = main_head->fast_out(i2);
1072     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
1073       Node *pre_phi = old_new[main_phi->_idx];
1074       Node *fallpre  = clone_up_backedge_goo(pre_head->back_control(),
1075                                              main_head->init_control(),
1076                                              pre_phi->in(LoopNode::LoopBackControl),
1077                                              visited, clones);
1078       _igvn.hash_delete(main_phi);
1079       main_phi->set_req( LoopNode::EntryControl, fallpre );
1080     }
1081   }
1082 
1083   // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1084   // RCE and alignment may change this later.
1085   Node *cmp_end = pre_end->cmp_node();
1086   assert( cmp_end->in(2) == limit, "" );
1087   Node *pre_limit = new (C) AddINode( init, stride );
1088 
1089   // Save the original loop limit in this Opaque1 node for
1090   // use by range check elimination.
1091   Node *pre_opaq  = new (C) Opaque1Node(C, pre_limit, limit);
1092 
1093   register_new_node( pre_limit, pre_head->in(0) );
1094   register_new_node( pre_opaq , pre_head->in(0) );
1095 
1096   // Since no other users of pre-loop compare, I can hack limit directly
1097   assert( cmp_end->outcnt() == 1, "no other users" );
1098   _igvn.hash_delete(cmp_end);
1099   cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
1100 
1101   // Special case for not-equal loop bounds:
1102   // Change pre loop test, main loop test, and the
1103   // main loop guard test to use lt or gt depending on stride
1104   // direction:
1105   // positive stride use <
1106   // negative stride use >
1107   //
1108   // not-equal test is kept for post loop to handle case
1109   // when init > limit when stride > 0 (and reverse).
1110 
1111   if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
1112 
1113     BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
1114     // Modify pre loop end condition
1115     Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1116     BoolNode* new_bol0 = new (C) BoolNode(pre_bol->in(1), new_test);
1117     register_new_node( new_bol0, pre_head->in(0) );
1118     _igvn.hash_delete(pre_end);
1119     pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0);
1120     // Modify main loop guard condition
1121     assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
1122     BoolNode* new_bol1 = new (C) BoolNode(min_bol->in(1), new_test);
1123     register_new_node( new_bol1, new_pre_exit );
1124     _igvn.hash_delete(min_iff);
1125     min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
1126     // Modify main loop end condition
1127     BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1128     BoolNode* new_bol2 = new (C) BoolNode(main_bol->in(1), new_test);
1129     register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
1130     _igvn.hash_delete(main_end);
1131     main_end->set_req(CountedLoopEndNode::TestValue, new_bol2);
1132   }
1133 
1134   // Flag main loop
1135   main_head->set_main_loop();
1136   if( peel_only ) main_head->set_main_no_pre_loop();
1137 
1138   // Subtract a trip count for the pre-loop.
1139   main_head->set_trip_count(main_head->trip_count() - 1);
1140 
1141   // It's difficult to be precise about the trip-counts
1142   // for the pre/post loops.  They are usually very short,
1143   // so guess that 4 trips is a reasonable value.
1144   post_head->set_profile_trip_cnt(4.0);
1145   pre_head->set_profile_trip_cnt(4.0);
1146 
1147   // Now force out all loop-invariant dominating tests.  The optimizer
1148   // finds some, but we _know_ they are all useless.
1149   peeled_dom_test_elim(loop,old_new);
1150 }
1151 
1152 //------------------------------is_invariant-----------------------------
1153 // Return true if n is invariant
1154 bool IdealLoopTree::is_invariant(Node* n) const {
1155   Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
1156   if (n_c->is_top()) return false;
1157   return !is_member(_phase->get_loop(n_c));
1158 }
1159 
1160 
1161 //------------------------------do_unroll--------------------------------------
1162 // Unroll the loop body one step - make each trip do 2 iterations.
1163 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
1164   assert(LoopUnrollLimit, "");
1165   CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
1166   CountedLoopEndNode *loop_end = loop_head->loopexit();
1167   assert(loop_end, "");
1168 #ifndef PRODUCT
1169   if (PrintOpto && VerifyLoopOptimizations) {
1170     tty->print("Unrolling ");
1171     loop->dump_head();
1172   } else if (TraceLoopOpts) {
1173     if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
1174       tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
1175     } else {
1176       tty->print("Unroll %d     ", loop_head->unrolled_count()*2);
1177     }
1178     loop->dump_head();
1179   }
1180 #endif
1181 
1182   // Remember loop node count before unrolling to detect
1183   // if rounds of unroll,optimize are making progress
1184   loop_head->set_node_count_before_unroll(loop->_body.size());
1185 
1186   Node *ctrl  = loop_head->in(LoopNode::EntryControl);
1187   Node *limit = loop_head->limit();
1188   Node *init  = loop_head->init_trip();
1189   Node *stride = loop_head->stride();
1190 
1191   Node *opaq = NULL;
1192   if (adjust_min_trip) {       // If not maximally unrolling, need adjustment
1193     // Search for zero-trip guard.
1194     assert( loop_head->is_main_loop(), "" );
1195     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
1196     Node *iff = ctrl->in(0);
1197     assert( iff->Opcode() == Op_If, "" );
1198     Node *bol = iff->in(1);
1199     assert( bol->Opcode() == Op_Bool, "" );
1200     Node *cmp = bol->in(1);
1201     assert( cmp->Opcode() == Op_CmpI, "" );
1202     opaq = cmp->in(2);
1203     // Occasionally it's possible for a zero-trip guard Opaque1 node to be
1204     // optimized away and then another round of loop opts attempted.
1205     // We can not optimize this particular loop in that case.
1206     if (opaq->Opcode() != Op_Opaque1)
1207       return; // Cannot find zero-trip guard!  Bail out!
1208     // Zero-trip test uses an 'opaque' node which is not shared.
1209     assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
1210   }
1211 
1212   C->set_major_progress();
1213 
1214   Node* new_limit = NULL;
1215   if (UnrollLimitCheck) {
1216     int stride_con = stride->get_int();
1217     int stride_p = (stride_con > 0) ? stride_con : -stride_con;
1218     uint old_trip_count = loop_head->trip_count();
1219     // Verify that unroll policy result is still valid.
1220     assert(old_trip_count > 1 &&
1221            (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity");
1222 
1223     // Adjust loop limit to keep valid iterations number after unroll.
1224     // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
1225     // which may overflow.
1226     if (!adjust_min_trip) {
1227       assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
1228              "odd trip count for maximally unroll");
1229       // Don't need to adjust limit for maximally unroll since trip count is even.
1230     } else if (loop_head->has_exact_trip_count() && init->is_Con()) {
1231       // Loop's limit is constant. Loop's init could be constant when pre-loop
1232       // become peeled iteration.
1233       jlong init_con = init->get_int();
1234       // We can keep old loop limit if iterations count stays the same:
1235       //   old_trip_count == new_trip_count * 2
1236       // Note: since old_trip_count >= 2 then new_trip_count >= 1
1237       // so we also don't need to adjust zero trip test.
1238       jlong limit_con  = limit->get_int();
1239       // (stride_con*2) not overflow since stride_con <= 8.
1240       int new_stride_con = stride_con * 2;
1241       int stride_m    = new_stride_con - (stride_con > 0 ? 1 : -1);
1242       jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con;
1243       // New trip count should satisfy next conditions.
1244       assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
1245       uint new_trip_count = (uint)trip_count;
1246       adjust_min_trip = (old_trip_count != new_trip_count*2);
1247     }
1248 
1249     if (adjust_min_trip) {
1250       // Step 2: Adjust the trip limit if it is called for.
1251       // The adjustment amount is -stride. Need to make sure if the
1252       // adjustment underflows or overflows, then the main loop is skipped.
1253       Node* cmp = loop_end->cmp_node();
1254       assert(cmp->in(2) == limit, "sanity");
1255       assert(opaq != NULL && opaq->in(1) == limit, "sanity");
1256 
1257       // Verify that policy_unroll result is still valid.
1258       const TypeInt* limit_type = _igvn.type(limit)->is_int();
1259       assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) ||
1260              stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity");
1261 
1262       if (limit->is_Con()) {
1263         // The check in policy_unroll and the assert above guarantee
1264         // no underflow if limit is constant.
1265         new_limit = _igvn.intcon(limit->get_int() - stride_con);
1266         set_ctrl(new_limit, C->root());
1267       } else {
1268         // Limit is not constant.
1269         if (loop_head->unrolled_count() == 1) { // only for first unroll
1270           // Separate limit by Opaque node in case it is an incremented
1271           // variable from previous loop to avoid using pre-incremented
1272           // value which could increase register pressure.
1273           // Otherwise reorg_offsets() optimization will create a separate
1274           // Opaque node for each use of trip-counter and as result
1275           // zero trip guard limit will be different from loop limit.
1276           assert(has_ctrl(opaq), "should have it");
1277           Node* opaq_ctrl = get_ctrl(opaq);
1278           limit = new (C) Opaque2Node( C, limit );
1279           register_new_node( limit, opaq_ctrl );
1280         }
1281         if (stride_con > 0 && ((limit_type->_lo - stride_con) < limit_type->_lo) ||
1282                    stride_con < 0 && ((limit_type->_hi - stride_con) > limit_type->_hi)) {
1283           // No underflow.
1284           new_limit = new (C) SubINode(limit, stride);
1285         } else {
1286           // (limit - stride) may underflow.
1287           // Clamp the adjustment value with MININT or MAXINT:
1288           //
1289           //   new_limit = limit-stride
1290           //   if (stride > 0)
1291           //     new_limit = (limit < new_limit) ? MININT : new_limit;
1292           //   else
1293           //     new_limit = (limit > new_limit) ? MAXINT : new_limit;
1294           //
1295           BoolTest::mask bt = loop_end->test_trip();
1296           assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
1297           Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint);
1298           set_ctrl(adj_max, C->root());
1299           Node* old_limit = NULL;
1300           Node* adj_limit = NULL;
1301           Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL;
1302           if (loop_head->unrolled_count() > 1 &&
1303               limit->is_CMove() && limit->Opcode() == Op_CMoveI &&
1304               limit->in(CMoveNode::IfTrue) == adj_max &&
1305               bol->as_Bool()->_test._test == bt &&
1306               bol->in(1)->Opcode() == Op_CmpI &&
1307               bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) {
1308             // Loop was unrolled before.
1309             // Optimize the limit to avoid nested CMove:
1310             // use original limit as old limit.
1311             old_limit = bol->in(1)->in(1);
1312             // Adjust previous adjusted limit.
1313             adj_limit = limit->in(CMoveNode::IfFalse);
1314             adj_limit = new (C) SubINode(adj_limit, stride);
1315           } else {
1316             old_limit = limit;
1317             adj_limit = new (C) SubINode(limit, stride);
1318           }
1319           assert(old_limit != NULL && adj_limit != NULL, "");
1320           register_new_node( adj_limit, ctrl ); // adjust amount
1321           Node* adj_cmp = new (C) CmpINode(old_limit, adj_limit);
1322           register_new_node( adj_cmp, ctrl );
1323           Node* adj_bool = new (C) BoolNode(adj_cmp, bt);
1324           register_new_node( adj_bool, ctrl );
1325           new_limit = new (C) CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT);
1326         }
1327         register_new_node(new_limit, ctrl);
1328       }
1329       assert(new_limit != NULL, "");
1330       // Replace in loop test.
1331       assert(loop_end->in(1)->in(1) == cmp, "sanity");
1332       if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
1333         // Don't need to create new test since only one user.
1334         _igvn.hash_delete(cmp);
1335         cmp->set_req(2, new_limit);
1336       } else {
1337         // Create new test since it is shared.
1338         Node* ctrl2 = loop_end->in(0);
1339         Node* cmp2  = cmp->clone();
1340         cmp2->set_req(2, new_limit);
1341         register_new_node(cmp2, ctrl2);
1342         Node* bol2 = loop_end->in(1)->clone();
1343         bol2->set_req(1, cmp2);
1344         register_new_node(bol2, ctrl2);
1345         _igvn.hash_delete(loop_end);
1346         loop_end->set_req(1, bol2);
1347       }
1348       // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1349       // Make it a 1-trip test (means at least 2 trips).
1350 
1351       // Guard test uses an 'opaque' node which is not shared.  Hence I
1352       // can edit it's inputs directly.  Hammer in the new limit for the
1353       // minimum-trip guard.
1354       assert(opaq->outcnt() == 1, "");
1355       _igvn.hash_delete(opaq);
1356       opaq->set_req(1, new_limit);
1357     }
1358 
1359     // Adjust max trip count. The trip count is intentionally rounded
1360     // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1361     // the main, unrolled, part of the loop will never execute as it is protected
1362     // by the min-trip test.  See bug 4834191 for a case where we over-unrolled
1363     // and later determined that part of the unrolled loop was dead.
1364     loop_head->set_trip_count(old_trip_count / 2);
1365 
1366     // Double the count of original iterations in the unrolled loop body.
1367     loop_head->double_unrolled_count();
1368 
1369   } else { // LoopLimitCheck
1370 
1371     // Adjust max trip count. The trip count is intentionally rounded
1372     // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1373     // the main, unrolled, part of the loop will never execute as it is protected
1374     // by the min-trip test.  See bug 4834191 for a case where we over-unrolled
1375     // and later determined that part of the unrolled loop was dead.
1376     loop_head->set_trip_count(loop_head->trip_count() / 2);
1377 
1378     // Double the count of original iterations in the unrolled loop body.
1379     loop_head->double_unrolled_count();
1380 
1381     // -----------
1382     // Step 2: Cut back the trip counter for an unroll amount of 2.
1383     // Loop will normally trip (limit - init)/stride_con.  Since it's a
1384     // CountedLoop this is exact (stride divides limit-init exactly).
1385     // We are going to double the loop body, so we want to knock off any
1386     // odd iteration: (trip_cnt & ~1).  Then back compute a new limit.
1387     Node *span = new (C) SubINode( limit, init );
1388     register_new_node( span, ctrl );
1389     Node *trip = new (C) DivINode( 0, span, stride );
1390     register_new_node( trip, ctrl );
1391     Node *mtwo = _igvn.intcon(-2);
1392     set_ctrl(mtwo, C->root());
1393     Node *rond = new (C) AndINode( trip, mtwo );
1394     register_new_node( rond, ctrl );
1395     Node *spn2 = new (C) MulINode( rond, stride );
1396     register_new_node( spn2, ctrl );
1397     new_limit = new (C) AddINode( spn2, init );
1398     register_new_node( new_limit, ctrl );
1399 
1400     // Hammer in the new limit
1401     Node *ctrl2 = loop_end->in(0);
1402     Node *cmp2 = new (C) CmpINode( loop_head->incr(), new_limit );
1403     register_new_node( cmp2, ctrl2 );
1404     Node *bol2 = new (C) BoolNode( cmp2, loop_end->test_trip() );
1405     register_new_node( bol2, ctrl2 );
1406     _igvn.hash_delete(loop_end);
1407     loop_end->set_req(CountedLoopEndNode::TestValue, bol2);
1408 
1409     // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1410     // Make it a 1-trip test (means at least 2 trips).
1411     if( adjust_min_trip ) {
1412       assert( new_limit != NULL, "" );
1413       // Guard test uses an 'opaque' node which is not shared.  Hence I
1414       // can edit it's inputs directly.  Hammer in the new limit for the
1415       // minimum-trip guard.
1416       assert( opaq->outcnt() == 1, "" );
1417       _igvn.hash_delete(opaq);
1418       opaq->set_req(1, new_limit);
1419     }
1420   } // LoopLimitCheck
1421 
1422   // ---------
1423   // Step 4: Clone the loop body.  Move it inside the loop.  This loop body
1424   // represents the odd iterations; since the loop trips an even number of
1425   // times its backedge is never taken.  Kill the backedge.
1426   uint dd = dom_depth(loop_head);
1427   clone_loop( loop, old_new, dd );
1428 
1429   // Make backedges of the clone equal to backedges of the original.
1430   // Make the fall-in from the original come from the fall-out of the clone.
1431   for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1432     Node* phi = loop_head->fast_out(j);
1433     if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1434       Node *newphi = old_new[phi->_idx];
1435       _igvn.hash_delete( phi );
1436       _igvn.hash_delete( newphi );
1437 
1438       phi   ->set_req(LoopNode::   EntryControl, newphi->in(LoopNode::LoopBackControl));
1439       newphi->set_req(LoopNode::LoopBackControl, phi   ->in(LoopNode::LoopBackControl));
1440       phi   ->set_req(LoopNode::LoopBackControl, C->top());
1441     }
1442   }
1443   Node *clone_head = old_new[loop_head->_idx];
1444   _igvn.hash_delete( clone_head );
1445   loop_head ->set_req(LoopNode::   EntryControl, clone_head->in(LoopNode::LoopBackControl));
1446   clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1447   loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1448   loop->_head = clone_head;     // New loop header
1449 
1450   set_idom(loop_head,  loop_head ->in(LoopNode::EntryControl), dd);
1451   set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1452 
1453   // Kill the clone's backedge
1454   Node *newcle = old_new[loop_end->_idx];
1455   _igvn.hash_delete( newcle );
1456   Node *one = _igvn.intcon(1);
1457   set_ctrl(one, C->root());
1458   newcle->set_req(1, one);
1459   // Force clone into same loop body
1460   uint max = loop->_body.size();
1461   for( uint k = 0; k < max; k++ ) {
1462     Node *old = loop->_body.at(k);
1463     Node *nnn = old_new[old->_idx];
1464     loop->_body.push(nnn);
1465     if (!has_ctrl(old))
1466       set_loop(nnn, loop);
1467   }
1468 
1469   loop->record_for_igvn();
1470 }
1471 
1472 //------------------------------do_maximally_unroll----------------------------
1473 
1474 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1475   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1476   assert(cl->has_exact_trip_count(), "trip count is not exact");
1477   assert(cl->trip_count() > 0, "");
1478 #ifndef PRODUCT
1479   if (TraceLoopOpts) {
1480     tty->print("MaxUnroll  %d ", cl->trip_count());
1481     loop->dump_head();
1482   }
1483 #endif
1484 
1485   // If loop is tripping an odd number of times, peel odd iteration
1486   if ((cl->trip_count() & 1) == 1) {
1487     do_peeling(loop, old_new);
1488   }
1489 
1490   // Now its tripping an even number of times remaining.  Double loop body.
1491   // Do not adjust pre-guards; they are not needed and do not exist.
1492   if (cl->trip_count() > 0) {
1493     assert((cl->trip_count() & 1) == 0, "missed peeling");
1494     do_unroll(loop, old_new, false);
1495   }
1496 }
1497 
1498 //------------------------------dominates_backedge---------------------------------
1499 // Returns true if ctrl is executed on every complete iteration
1500 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1501   assert(ctrl->is_CFG(), "must be control");
1502   Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1503   return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1504 }
1505 
1506 //------------------------------adjust_limit-----------------------------------
1507 // Helper function for add_constraint().
1508 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) {
1509   // Compute "I :: (limit-offset)/scale"
1510   Node *con = new (C) SubINode(rc_limit, offset);
1511   register_new_node(con, pre_ctrl);
1512   Node *X = new (C) DivINode(0, con, scale);
1513   register_new_node(X, pre_ctrl);
1514 
1515   // Adjust loop limit
1516   loop_limit = (stride_con > 0)
1517                ? (Node*)(new (C) MinINode(loop_limit, X))
1518                : (Node*)(new (C) MaxINode(loop_limit, X));
1519   register_new_node(loop_limit, pre_ctrl);
1520   return loop_limit;
1521 }
1522 
1523 //------------------------------add_constraint---------------------------------
1524 // Constrain the main loop iterations so the conditions:
1525 //    low_limit <= scale_con * I + offset  <  upper_limit
1526 // always holds true.  That is, either increase the number of iterations in
1527 // the pre-loop or the post-loop until the condition holds true in the main
1528 // loop.  Stride, scale, offset and limit are all loop invariant.  Further,
1529 // stride and scale are constants (offset and limit often are).
1530 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 ) {
1531   // For positive stride, the pre-loop limit always uses a MAX function
1532   // and the main loop a MIN function.  For negative stride these are
1533   // reversed.
1534 
1535   // Also for positive stride*scale the affine function is increasing, so the
1536   // pre-loop must check for underflow and the post-loop for overflow.
1537   // Negative stride*scale reverses this; pre-loop checks for overflow and
1538   // post-loop for underflow.
1539 
1540   Node *scale = _igvn.intcon(scale_con);
1541   set_ctrl(scale, C->root());
1542 
1543   if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
1544     // The overflow limit: scale*I+offset < upper_limit
1545     // For main-loop compute
1546     //   ( if (scale > 0) /* and stride > 0 */
1547     //       I < (upper_limit-offset)/scale
1548     //     else /* scale < 0 and stride < 0 */
1549     //       I > (upper_limit-offset)/scale
1550     //   )
1551     //
1552     // (upper_limit-offset) may overflow or underflow.
1553     // But it is fine since main loop will either have
1554     // less iterations or will be skipped in such case.
1555     *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl);
1556 
1557     // The underflow limit: low_limit <= scale*I+offset.
1558     // For pre-loop compute
1559     //   NOT(scale*I+offset >= low_limit)
1560     //   scale*I+offset < low_limit
1561     //   ( if (scale > 0) /* and stride > 0 */
1562     //       I < (low_limit-offset)/scale
1563     //     else /* scale < 0 and stride < 0 */
1564     //       I > (low_limit-offset)/scale
1565     //   )
1566 
1567     if (low_limit->get_int() == -max_jint) {
1568       if (!RangeLimitCheck) return;
1569       // We need this guard when scale*pre_limit+offset >= limit
1570       // due to underflow. So we need execute pre-loop until
1571       // scale*I+offset >= min_int. But (min_int-offset) will
1572       // underflow when offset > 0 and X will be > original_limit
1573       // when stride > 0. To avoid it we replace positive offset with 0.
1574       //
1575       // Also (min_int+1 == -max_int) is used instead of min_int here
1576       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1577       Node* shift = _igvn.intcon(31);
1578       set_ctrl(shift, C->root());
1579       Node* sign = new (C) RShiftINode(offset, shift);
1580       register_new_node(sign, pre_ctrl);
1581       offset = new (C) AndINode(offset, sign);
1582       register_new_node(offset, pre_ctrl);
1583     } else {
1584       assert(low_limit->get_int() == 0, "wrong low limit for range check");
1585       // The only problem we have here when offset == min_int
1586       // since (0-min_int) == min_int. It may be fine for stride > 0
1587       // but for stride < 0 X will be < original_limit. To avoid it
1588       // max(pre_limit, original_limit) is used in do_range_check().
1589     }
1590     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1591     *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl);
1592 
1593   } else { // stride_con*scale_con < 0
1594     // For negative stride*scale pre-loop checks for overflow and
1595     // post-loop for underflow.
1596     //
1597     // The overflow limit: scale*I+offset < upper_limit
1598     // For pre-loop compute
1599     //   NOT(scale*I+offset < upper_limit)
1600     //   scale*I+offset >= upper_limit
1601     //   scale*I+offset+1 > upper_limit
1602     //   ( if (scale < 0) /* and stride > 0 */
1603     //       I < (upper_limit-(offset+1))/scale
1604     //     else /* scale > 0 and stride < 0 */
1605     //       I > (upper_limit-(offset+1))/scale
1606     //   )
1607     //
1608     // (upper_limit-offset-1) may underflow or overflow.
1609     // To avoid it min(pre_limit, original_limit) is used
1610     // in do_range_check() for stride > 0 and max() for < 0.
1611     Node *one  = _igvn.intcon(1);
1612     set_ctrl(one, C->root());
1613 
1614     Node *plus_one = new (C) AddINode(offset, one);
1615     register_new_node( plus_one, pre_ctrl );
1616     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1617     *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl);
1618 
1619     if (low_limit->get_int() == -max_jint) {
1620       if (!RangeLimitCheck) return;
1621       // We need this guard when scale*main_limit+offset >= limit
1622       // due to underflow. So we need execute main-loop while
1623       // scale*I+offset+1 > min_int. But (min_int-offset-1) will
1624       // underflow when (offset+1) > 0 and X will be < main_limit
1625       // when scale < 0 (and stride > 0). To avoid it we replace
1626       // positive (offset+1) with 0.
1627       //
1628       // Also (min_int+1 == -max_int) is used instead of min_int here
1629       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1630       Node* shift = _igvn.intcon(31);
1631       set_ctrl(shift, C->root());
1632       Node* sign = new (C) RShiftINode(plus_one, shift);
1633       register_new_node(sign, pre_ctrl);
1634       plus_one = new (C) AndINode(plus_one, sign);
1635       register_new_node(plus_one, pre_ctrl);
1636     } else {
1637       assert(low_limit->get_int() == 0, "wrong low limit for range check");
1638       // The only problem we have here when offset == max_int
1639       // since (max_int+1) == min_int and (0-min_int) == min_int.
1640       // But it is fine since main loop will either have
1641       // less iterations or will be skipped in such case.
1642     }
1643     // The underflow limit: low_limit <= scale*I+offset.
1644     // For main-loop compute
1645     //   scale*I+offset+1 > low_limit
1646     //   ( if (scale < 0) /* and stride > 0 */
1647     //       I < (low_limit-(offset+1))/scale
1648     //     else /* scale > 0 and stride < 0 */
1649     //       I > (low_limit-(offset+1))/scale
1650     //   )
1651 
1652     *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl);
1653   }
1654 }
1655 
1656 
1657 //------------------------------is_scaled_iv---------------------------------
1658 // Return true if exp is a constant times an induction var
1659 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1660   if (exp == iv) {
1661     if (p_scale != NULL) {
1662       *p_scale = 1;
1663     }
1664     return true;
1665   }
1666   int opc = exp->Opcode();
1667   if (opc == Op_MulI) {
1668     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1669       if (p_scale != NULL) {
1670         *p_scale = exp->in(2)->get_int();
1671       }
1672       return true;
1673     }
1674     if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1675       if (p_scale != NULL) {
1676         *p_scale = exp->in(1)->get_int();
1677       }
1678       return true;
1679     }
1680   } else if (opc == Op_LShiftI) {
1681     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1682       if (p_scale != NULL) {
1683         *p_scale = 1 << exp->in(2)->get_int();
1684       }
1685       return true;
1686     }
1687   }
1688   return false;
1689 }
1690 
1691 //-----------------------------is_scaled_iv_plus_offset------------------------------
1692 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1693 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1694   if (is_scaled_iv(exp, iv, p_scale)) {
1695     if (p_offset != NULL) {
1696       Node *zero = _igvn.intcon(0);
1697       set_ctrl(zero, C->root());
1698       *p_offset = zero;
1699     }
1700     return true;
1701   }
1702   int opc = exp->Opcode();
1703   if (opc == Op_AddI) {
1704     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1705       if (p_offset != NULL) {
1706         *p_offset = exp->in(2);
1707       }
1708       return true;
1709     }
1710     if (exp->in(2)->is_Con()) {
1711       Node* offset2 = NULL;
1712       if (depth < 2 &&
1713           is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
1714                                    p_offset != NULL ? &offset2 : NULL, depth+1)) {
1715         if (p_offset != NULL) {
1716           Node *ctrl_off2 = get_ctrl(offset2);
1717           Node* offset = new (C) AddINode(offset2, exp->in(2));
1718           register_new_node(offset, ctrl_off2);
1719           *p_offset = offset;
1720         }
1721         return true;
1722       }
1723     }
1724   } else if (opc == Op_SubI) {
1725     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1726       if (p_offset != NULL) {
1727         Node *zero = _igvn.intcon(0);
1728         set_ctrl(zero, C->root());
1729         Node *ctrl_off = get_ctrl(exp->in(2));
1730         Node* offset = new (C) SubINode(zero, exp->in(2));
1731         register_new_node(offset, ctrl_off);
1732         *p_offset = offset;
1733       }
1734       return true;
1735     }
1736     if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1737       if (p_offset != NULL) {
1738         *p_scale *= -1;
1739         *p_offset = exp->in(1);
1740       }
1741       return true;
1742     }
1743   }
1744   return false;
1745 }
1746 
1747 //------------------------------do_range_check---------------------------------
1748 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1749 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
1750 #ifndef PRODUCT
1751   if (PrintOpto && VerifyLoopOptimizations) {
1752     tty->print("Range Check Elimination ");
1753     loop->dump_head();
1754   } else if (TraceLoopOpts) {
1755     tty->print("RangeCheck   ");
1756     loop->dump_head();
1757   }
1758 #endif
1759   assert(RangeCheckElimination, "");
1760   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1761   assert(cl->is_main_loop(), "");
1762 
1763   // protect against stride not being a constant
1764   if (!cl->stride_is_con())
1765     return;
1766 
1767   // Find the trip counter; we are iteration splitting based on it
1768   Node *trip_counter = cl->phi();
1769   // Find the main loop limit; we will trim it's iterations
1770   // to not ever trip end tests
1771   Node *main_limit = cl->limit();
1772 
1773   // Need to find the main-loop zero-trip guard
1774   Node *ctrl  = cl->in(LoopNode::EntryControl);
1775   assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
1776   Node *iffm = ctrl->in(0);
1777   assert(iffm->Opcode() == Op_If, "");
1778   Node *bolzm = iffm->in(1);
1779   assert(bolzm->Opcode() == Op_Bool, "");
1780   Node *cmpzm = bolzm->in(1);
1781   assert(cmpzm->is_Cmp(), "");
1782   Node *opqzm = cmpzm->in(2);
1783   // Can not optimize a loop if zero-trip Opaque1 node is optimized
1784   // away and then another round of loop opts attempted.
1785   if (opqzm->Opcode() != Op_Opaque1)
1786     return;
1787   assert(opqzm->in(1) == main_limit, "do not understand situation");
1788 
1789   // Find the pre-loop limit; we will expand it's iterations to
1790   // not ever trip low tests.
1791   Node *p_f = iffm->in(0);
1792   assert(p_f->Opcode() == Op_IfFalse, "");
1793   CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
1794   assert(pre_end->loopnode()->is_pre_loop(), "");
1795   Node *pre_opaq1 = pre_end->limit();
1796   // Occasionally it's possible for a pre-loop Opaque1 node to be
1797   // optimized away and then another round of loop opts attempted.
1798   // We can not optimize this particular loop in that case.
1799   if (pre_opaq1->Opcode() != Op_Opaque1)
1800     return;
1801   Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
1802   Node *pre_limit = pre_opaq->in(1);
1803 
1804   // Where do we put new limit calculations
1805   Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
1806 
1807   // Ensure the original loop limit is available from the
1808   // pre-loop Opaque1 node.
1809   Node *orig_limit = pre_opaq->original_loop_limit();
1810   if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
1811     return;
1812 
1813   // Must know if its a count-up or count-down loop
1814 
1815   int stride_con = cl->stride_con();
1816   Node *zero = _igvn.intcon(0);
1817   Node *one  = _igvn.intcon(1);
1818   // Use symmetrical int range [-max_jint,max_jint]
1819   Node *mini = _igvn.intcon(-max_jint);
1820   set_ctrl(zero, C->root());
1821   set_ctrl(one,  C->root());
1822   set_ctrl(mini, C->root());
1823 
1824   // Range checks that do not dominate the loop backedge (ie.
1825   // conditionally executed) can lengthen the pre loop limit beyond
1826   // the original loop limit. To prevent this, the pre limit is
1827   // (for stride > 0) MINed with the original loop limit (MAXed
1828   // stride < 0) when some range_check (rc) is conditionally
1829   // executed.
1830   bool conditional_rc = false;
1831 
1832   // Check loop body for tests of trip-counter plus loop-invariant vs
1833   // loop-invariant.
1834   for( uint i = 0; i < loop->_body.size(); i++ ) {
1835     Node *iff = loop->_body[i];
1836     if( iff->Opcode() == Op_If ) { // Test?
1837 
1838       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
1839       // we need loop unswitching instead of iteration splitting.
1840       Node *exit = loop->is_loop_exit(iff);
1841       if( !exit ) continue;
1842       int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
1843 
1844       // Get boolean condition to test
1845       Node *i1 = iff->in(1);
1846       if( !i1->is_Bool() ) continue;
1847       BoolNode *bol = i1->as_Bool();
1848       BoolTest b_test = bol->_test;
1849       // Flip sense of test if exit condition is flipped
1850       if( flip )
1851         b_test = b_test.negate();
1852 
1853       // Get compare
1854       Node *cmp = bol->in(1);
1855 
1856       // Look for trip_counter + offset vs limit
1857       Node *rc_exp = cmp->in(1);
1858       Node *limit  = cmp->in(2);
1859       jint scale_con= 1;        // Assume trip counter not scaled
1860 
1861       Node *limit_c = get_ctrl(limit);
1862       if( loop->is_member(get_loop(limit_c) ) ) {
1863         // Compare might have operands swapped; commute them
1864         b_test = b_test.commute();
1865         rc_exp = cmp->in(2);
1866         limit  = cmp->in(1);
1867         limit_c = get_ctrl(limit);
1868         if( loop->is_member(get_loop(limit_c) ) )
1869           continue;             // Both inputs are loop varying; cannot RCE
1870       }
1871       // Here we know 'limit' is loop invariant
1872 
1873       // 'limit' maybe pinned below the zero trip test (probably from a
1874       // previous round of rce), in which case, it can't be used in the
1875       // zero trip test expression which must occur before the zero test's if.
1876       if( limit_c == ctrl ) {
1877         continue;  // Don't rce this check but continue looking for other candidates.
1878       }
1879 
1880       // Check for scaled induction variable plus an offset
1881       Node *offset = NULL;
1882 
1883       if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
1884         continue;
1885       }
1886 
1887       Node *offset_c = get_ctrl(offset);
1888       if( loop->is_member( get_loop(offset_c) ) )
1889         continue;               // Offset is not really loop invariant
1890       // Here we know 'offset' is loop invariant.
1891 
1892       // As above for the 'limit', the 'offset' maybe pinned below the
1893       // zero trip test.
1894       if( offset_c == ctrl ) {
1895         continue; // Don't rce this check but continue looking for other candidates.
1896       }
1897 #ifdef ASSERT
1898       if (TraceRangeLimitCheck) {
1899         tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
1900         bol->dump(2);
1901       }
1902 #endif
1903       // At this point we have the expression as:
1904       //   scale_con * trip_counter + offset :: limit
1905       // where scale_con, offset and limit are loop invariant.  Trip_counter
1906       // monotonically increases by stride_con, a constant.  Both (or either)
1907       // stride_con and scale_con can be negative which will flip about the
1908       // sense of the test.
1909 
1910       // Adjust pre and main loop limits to guard the correct iteration set
1911       if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
1912         if( b_test._test == BoolTest::lt ) { // Range checks always use lt
1913           // The underflow and overflow limits: 0 <= scale*I+offset < limit
1914           add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit );
1915           if (!conditional_rc) {
1916             // (0-offset)/scale could be outside of loop iterations range.
1917             conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1918           }
1919         } else {
1920 #ifndef PRODUCT
1921           if( PrintOpto )
1922             tty->print_cr("missed RCE opportunity");
1923 #endif
1924           continue;             // In release mode, ignore it
1925         }
1926       } else {                  // Otherwise work on normal compares
1927         switch( b_test._test ) {
1928         case BoolTest::gt:
1929           // Fall into GE case
1930         case BoolTest::ge:
1931           // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
1932           scale_con = -scale_con;
1933           offset = new (C) SubINode( zero, offset );
1934           register_new_node( offset, pre_ctrl );
1935           limit  = new (C) SubINode( zero, limit  );
1936           register_new_node( limit, pre_ctrl );
1937           // Fall into LE case
1938         case BoolTest::le:
1939           if (b_test._test != BoolTest::gt) {
1940             // Convert X <= Y to X < Y+1
1941             limit = new (C) AddINode( limit, one );
1942             register_new_node( limit, pre_ctrl );
1943           }
1944           // Fall into LT case
1945         case BoolTest::lt:
1946           // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
1947           // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
1948           // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
1949           add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit );
1950           if (!conditional_rc) {
1951             // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range.
1952             // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could
1953             // still be outside of loop range.
1954             conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1955           }
1956           break;
1957         default:
1958 #ifndef PRODUCT
1959           if( PrintOpto )
1960             tty->print_cr("missed RCE opportunity");
1961 #endif
1962           continue;             // Unhandled case
1963         }
1964       }
1965 
1966       // Kill the eliminated test
1967       C->set_major_progress();
1968       Node *kill_con = _igvn.intcon( 1-flip );
1969       set_ctrl(kill_con, C->root());
1970       _igvn.replace_input_of(iff, 1, kill_con);
1971       // Find surviving projection
1972       assert(iff->is_If(), "");
1973       ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
1974       // Find loads off the surviving projection; remove their control edge
1975       for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
1976         Node* cd = dp->fast_out(i); // Control-dependent node
1977         if (cd->is_Load() && cd->depends_only_on_test()) {   // Loads can now float around in the loop
1978           // Allow the load to float around in the loop, or before it
1979           // but NOT before the pre-loop.
1980           _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL
1981           --i;
1982           --imax;
1983         }
1984       }
1985 
1986     } // End of is IF
1987 
1988   }
1989 
1990   // Update loop limits
1991   if (conditional_rc) {
1992     pre_limit = (stride_con > 0) ? (Node*)new (C) MinINode(pre_limit, orig_limit)
1993                                  : (Node*)new (C) MaxINode(pre_limit, orig_limit);
1994     register_new_node(pre_limit, pre_ctrl);
1995   }
1996   _igvn.hash_delete(pre_opaq);
1997   pre_opaq->set_req(1, pre_limit);
1998 
1999   // Note:: we are making the main loop limit no longer precise;
2000   // need to round up based on stride.
2001   cl->set_nonexact_trip_count();
2002   if (!LoopLimitCheck && stride_con != 1 && stride_con != -1) { // Cutout for common case
2003     // "Standard" round-up logic:  ([main_limit-init+(y-1)]/y)*y+init
2004     // Hopefully, compiler will optimize for powers of 2.
2005     Node *ctrl = get_ctrl(main_limit);
2006     Node *stride = cl->stride();
2007     Node *init = cl->init_trip();
2008     Node *span = new (C) SubINode(main_limit,init);
2009     register_new_node(span,ctrl);
2010     Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
2011     Node *add = new (C) AddINode(span,rndup);
2012     register_new_node(add,ctrl);
2013     Node *div = new (C) DivINode(0,add,stride);
2014     register_new_node(div,ctrl);
2015     Node *mul = new (C) MulINode(div,stride);
2016     register_new_node(mul,ctrl);
2017     Node *newlim = new (C) AddINode(mul,init);
2018     register_new_node(newlim,ctrl);
2019     main_limit = newlim;
2020   }
2021 
2022   Node *main_cle = cl->loopexit();
2023   Node *main_bol = main_cle->in(1);
2024   // Hacking loop bounds; need private copies of exit test
2025   if( main_bol->outcnt() > 1 ) {// BoolNode shared?
2026     _igvn.hash_delete(main_cle);
2027     main_bol = main_bol->clone();// Clone a private BoolNode
2028     register_new_node( main_bol, main_cle->in(0) );
2029     main_cle->set_req(1,main_bol);
2030   }
2031   Node *main_cmp = main_bol->in(1);
2032   if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
2033     _igvn.hash_delete(main_bol);
2034     main_cmp = main_cmp->clone();// Clone a private CmpNode
2035     register_new_node( main_cmp, main_cle->in(0) );
2036     main_bol->set_req(1,main_cmp);
2037   }
2038   // Hack the now-private loop bounds
2039   _igvn.replace_input_of(main_cmp, 2, main_limit);
2040   // The OpaqueNode is unshared by design
2041   assert( opqzm->outcnt() == 1, "cannot hack shared node" );
2042   _igvn.replace_input_of(opqzm, 1, main_limit);
2043 }
2044 
2045 //------------------------------DCE_loop_body----------------------------------
2046 // Remove simplistic dead code from loop body
2047 void IdealLoopTree::DCE_loop_body() {
2048   for( uint i = 0; i < _body.size(); i++ )
2049     if( _body.at(i)->outcnt() == 0 )
2050       _body.map( i--, _body.pop() );
2051 }
2052 
2053 
2054 //------------------------------adjust_loop_exit_prob--------------------------
2055 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
2056 // Replace with a 1-in-10 exit guess.
2057 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
2058   Node *test = tail();
2059   while( test != _head ) {
2060     uint top = test->Opcode();
2061     if( top == Op_IfTrue || top == Op_IfFalse ) {
2062       int test_con = ((ProjNode*)test)->_con;
2063       assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
2064       IfNode *iff = test->in(0)->as_If();
2065       if( iff->outcnt() == 2 ) {        // Ignore dead tests
2066         Node *bol = iff->in(1);
2067         if( bol && bol->req() > 1 && bol->in(1) &&
2068             ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
2069              (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
2070              (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
2071              (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
2072              (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
2073              (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
2074              (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
2075           return;               // Allocation loops RARELY take backedge
2076         // Find the OTHER exit path from the IF
2077         Node* ex = iff->proj_out(1-test_con);
2078         float p = iff->_prob;
2079         if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
2080           if( top == Op_IfTrue ) {
2081             if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
2082               iff->_prob = PROB_STATIC_FREQUENT;
2083             }
2084           } else {
2085             if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
2086               iff->_prob = PROB_STATIC_INFREQUENT;
2087             }
2088           }
2089         }
2090       }
2091     }
2092     test = phase->idom(test);
2093   }
2094 }
2095 
2096 
2097 //------------------------------policy_do_remove_empty_loop--------------------
2098 // Micro-benchmark spamming.  Policy is to always remove empty loops.
2099 // The 'DO' part is to replace the trip counter with the value it will
2100 // have on the last iteration.  This will break the loop.
2101 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
2102   // Minimum size must be empty loop
2103   if (_body.size() > EMPTY_LOOP_SIZE)
2104     return false;
2105 
2106   if (!_head->is_CountedLoop())
2107     return false;     // Dead loop
2108   CountedLoopNode *cl = _head->as_CountedLoop();
2109   if (!cl->is_valid_counted_loop())
2110     return false; // Malformed loop
2111   if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
2112     return false;             // Infinite loop
2113 
2114 #ifdef ASSERT
2115   // Ensure only one phi which is the iv.
2116   Node* iv = NULL;
2117   for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
2118     Node* n = cl->fast_out(i);
2119     if (n->Opcode() == Op_Phi) {
2120       assert(iv == NULL, "Too many phis" );
2121       iv = n;
2122     }
2123   }
2124   assert(iv == cl->phi(), "Wrong phi" );
2125 #endif
2126 
2127   // main and post loops have explicitly created zero trip guard
2128   bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
2129   if (needs_guard) {
2130     // Skip guard if values not overlap.
2131     const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
2132     const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
2133     int  stride_con = cl->stride_con();
2134     if (stride_con > 0) {
2135       needs_guard = (init_t->_hi >= limit_t->_lo);
2136     } else {
2137       needs_guard = (init_t->_lo <= limit_t->_hi);
2138     }
2139   }
2140   if (needs_guard) {
2141     // Check for an obvious zero trip guard.
2142     Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl));
2143     if (inctrl->Opcode() == Op_IfTrue) {
2144       // The test should look like just the backedge of a CountedLoop
2145       Node* iff = inctrl->in(0);
2146       if (iff->is_If()) {
2147         Node* bol = iff->in(1);
2148         if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) {
2149           Node* cmp = bol->in(1);
2150           if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) {
2151             needs_guard = false;
2152           }
2153         }
2154       }
2155     }
2156   }
2157 
2158 #ifndef PRODUCT
2159   if (PrintOpto) {
2160     tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
2161     this->dump_head();
2162   } else if (TraceLoopOpts) {
2163     tty->print("Empty with%s zero trip guard   ", needs_guard ? "out" : "");
2164     this->dump_head();
2165   }
2166 #endif
2167 
2168   if (needs_guard) {
2169     // Peel the loop to ensure there's a zero trip guard
2170     Node_List old_new;
2171     phase->do_peeling(this, old_new);
2172   }
2173 
2174   // Replace the phi at loop head with the final value of the last
2175   // iteration.  Then the CountedLoopEnd will collapse (backedge never
2176   // taken) and all loop-invariant uses of the exit values will be correct.
2177   Node *phi = cl->phi();
2178   Node *exact_limit = phase->exact_limit(this);
2179   if (exact_limit != cl->limit()) {
2180     // We also need to replace the original limit to collapse loop exit.
2181     Node* cmp = cl->loopexit()->cmp_node();
2182     assert(cl->limit() == cmp->in(2), "sanity");
2183     phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
2184     phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist
2185   }
2186   // Note: the final value after increment should not overflow since
2187   // counted loop has limit check predicate.
2188   Node *final = new (phase->C) SubINode( exact_limit, cl->stride() );
2189   phase->register_new_node(final,cl->in(LoopNode::EntryControl));
2190   phase->_igvn.replace_node(phi,final);
2191   phase->C->set_major_progress();
2192   return true;
2193 }
2194 
2195 //------------------------------policy_do_one_iteration_loop-------------------
2196 // Convert one iteration loop into normal code.
2197 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) {
2198   if (!_head->as_Loop()->is_valid_counted_loop())
2199     return false; // Only for counted loop
2200 
2201   CountedLoopNode *cl = _head->as_CountedLoop();
2202   if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
2203     return false;
2204   }
2205 
2206 #ifndef PRODUCT
2207   if(TraceLoopOpts) {
2208     tty->print("OneIteration ");
2209     this->dump_head();
2210   }
2211 #endif
2212 
2213   Node *init_n = cl->init_trip();
2214 #ifdef ASSERT
2215   // Loop boundaries should be constant since trip count is exact.
2216   assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration");
2217 #endif
2218   // Replace the phi at loop head with the value of the init_trip.
2219   // Then the CountedLoopEnd will collapse (backedge will not be taken)
2220   // and all loop-invariant uses of the exit values will be correct.
2221   phase->_igvn.replace_node(cl->phi(), cl->init_trip());
2222   phase->C->set_major_progress();
2223   return true;
2224 }
2225 
2226 //=============================================================================
2227 //------------------------------iteration_split_impl---------------------------
2228 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
2229   // Compute exact loop trip count if possible.
2230   compute_exact_trip_count(phase);
2231 
2232   // Convert one iteration loop into normal code.
2233   if (policy_do_one_iteration_loop(phase))
2234     return true;
2235 
2236   // Check and remove empty loops (spam micro-benchmarks)
2237   if (policy_do_remove_empty_loop(phase))
2238     return true;  // Here we removed an empty loop
2239 
2240   bool should_peel = policy_peeling(phase); // Should we peel?
2241 
2242   bool should_unswitch = policy_unswitching(phase);
2243 
2244   // Non-counted loops may be peeled; exactly 1 iteration is peeled.
2245   // This removes loop-invariant tests (usually null checks).
2246   if (!_head->is_CountedLoop()) { // Non-counted loop
2247     if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
2248       // Partial peel succeeded so terminate this round of loop opts
2249       return false;
2250     }
2251     if (should_peel) {            // Should we peel?
2252 #ifndef PRODUCT
2253       if (PrintOpto) tty->print_cr("should_peel");
2254 #endif
2255       phase->do_peeling(this,old_new);
2256     } else if (should_unswitch) {
2257       phase->do_unswitching(this, old_new);
2258     }
2259     return true;
2260   }
2261   CountedLoopNode *cl = _head->as_CountedLoop();
2262 
2263   if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops
2264 
2265   // Do nothing special to pre- and post- loops
2266   if (cl->is_pre_loop() || cl->is_post_loop()) return true;
2267 
2268   // Compute loop trip count from profile data
2269   compute_profile_trip_cnt(phase);
2270 
2271   // Before attempting fancy unrolling, RCE or alignment, see if we want
2272   // to completely unroll this loop or do loop unswitching.
2273   if (cl->is_normal_loop()) {
2274     if (should_unswitch) {
2275       phase->do_unswitching(this, old_new);
2276       return true;
2277     }
2278     bool should_maximally_unroll =  policy_maximally_unroll(phase);
2279     if (should_maximally_unroll) {
2280       // Here we did some unrolling and peeling.  Eventually we will
2281       // completely unroll this loop and it will no longer be a loop.
2282       phase->do_maximally_unroll(this,old_new);
2283       return true;
2284     }
2285   }
2286 
2287   // Skip next optimizations if running low on nodes. Note that
2288   // policy_unswitching and policy_maximally_unroll have this check.
2289   uint nodes_left = MaxNodeLimit - (uint) phase->C->live_nodes();
2290   if ((2 * _body.size()) > nodes_left) {
2291     return true;
2292   }
2293 
2294   // Counted loops may be peeled, may need some iterations run up
2295   // front for RCE, and may want to align loop refs to a cache
2296   // line.  Thus we clone a full loop up front whose trip count is
2297   // at least 1 (if peeling), but may be several more.
2298 
2299   // The main loop will start cache-line aligned with at least 1
2300   // iteration of the unrolled body (zero-trip test required) and
2301   // will have some range checks removed.
2302 
2303   // A post-loop will finish any odd iterations (leftover after
2304   // unrolling), plus any needed for RCE purposes.
2305 
2306   bool should_unroll = policy_unroll(phase);
2307 
2308   bool should_rce = policy_range_check(phase);
2309 
2310   bool should_align = policy_align(phase);
2311 
2312   // If not RCE'ing (iteration splitting) or Aligning, then we do not
2313   // need a pre-loop.  We may still need to peel an initial iteration but
2314   // we will not be needing an unknown number of pre-iterations.
2315   //
2316   // Basically, if may_rce_align reports FALSE first time through,
2317   // we will not be able to later do RCE or Aligning on this loop.
2318   bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
2319 
2320   // If we have any of these conditions (RCE, alignment, unrolling) met, then
2321   // we switch to the pre-/main-/post-loop model.  This model also covers
2322   // peeling.
2323   if (should_rce || should_align || should_unroll) {
2324     if (cl->is_normal_loop())  // Convert to 'pre/main/post' loops
2325       phase->insert_pre_post_loops(this,old_new, !may_rce_align);
2326 
2327     // Adjust the pre- and main-loop limits to let the pre and post loops run
2328     // with full checks, but the main-loop with no checks.  Remove said
2329     // checks from the main body.
2330     if (should_rce)
2331       phase->do_range_check(this,old_new);
2332 
2333     // Double loop body for unrolling.  Adjust the minimum-trip test (will do
2334     // twice as many iterations as before) and the main body limit (only do
2335     // an even number of trips).  If we are peeling, we might enable some RCE
2336     // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
2337     // peeling.
2338     if (should_unroll && !should_peel)
2339       phase->do_unroll(this,old_new, true);
2340 
2341     // Adjust the pre-loop limits to align the main body
2342     // iterations.
2343     if (should_align)
2344       Unimplemented();
2345 
2346   } else {                      // Else we have an unchanged counted loop
2347     if (should_peel)           // Might want to peel but do nothing else
2348       phase->do_peeling(this,old_new);
2349   }
2350   return true;
2351 }
2352 
2353 
2354 //=============================================================================
2355 //------------------------------iteration_split--------------------------------
2356 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
2357   // Recursively iteration split nested loops
2358   if (_child && !_child->iteration_split(phase, old_new))
2359     return false;
2360 
2361   // Clean out prior deadwood
2362   DCE_loop_body();
2363 
2364 
2365   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
2366   // Replace with a 1-in-10 exit guess.
2367   if (_parent /*not the root loop*/ &&
2368       !_irreducible &&
2369       // Also ignore the occasional dead backedge
2370       !tail()->is_top()) {
2371     adjust_loop_exit_prob(phase);
2372   }
2373 
2374   // Gate unrolling, RCE and peeling efforts.
2375   if (!_child &&                // If not an inner loop, do not split
2376       !_irreducible &&
2377       _allow_optimizations &&
2378       !tail()->is_top()) {     // Also ignore the occasional dead backedge
2379     if (!_has_call) {
2380         if (!iteration_split_impl(phase, old_new)) {
2381           return false;
2382         }
2383     } else if (policy_unswitching(phase)) {
2384       phase->do_unswitching(this, old_new);
2385     }
2386   }
2387 
2388   // Minor offset re-organization to remove loop-fallout uses of
2389   // trip counter when there was no major reshaping.
2390   phase->reorg_offsets(this);
2391 
2392   if (_next && !_next->iteration_split(phase, old_new))
2393     return false;
2394   return true;
2395 }
2396 
2397 
2398 //=============================================================================
2399 // Process all the loops in the loop tree and replace any fill
2400 // patterns with an intrisc version.
2401 bool PhaseIdealLoop::do_intrinsify_fill() {
2402   bool changed = false;
2403   for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2404     IdealLoopTree* lpt = iter.current();
2405     changed |= intrinsify_fill(lpt);
2406   }
2407   return changed;
2408 }
2409 
2410 
2411 // Examine an inner loop looking for a a single store of an invariant
2412 // value in a unit stride loop,
2413 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
2414                                      Node*& shift, Node*& con) {
2415   const char* msg = NULL;
2416   Node* msg_node = NULL;
2417 
2418   store_value = NULL;
2419   con = NULL;
2420   shift = NULL;
2421 
2422   // Process the loop looking for stores.  If there are multiple
2423   // stores or extra control flow give at this point.
2424   CountedLoopNode* head = lpt->_head->as_CountedLoop();
2425   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2426     Node* n = lpt->_body.at(i);
2427     if (n->outcnt() == 0) continue; // Ignore dead
2428     if (n->is_Store()) {
2429       if (store != NULL) {
2430         msg = "multiple stores";
2431         break;
2432       }
2433       int opc = n->Opcode();
2434       if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass || opc == Op_StoreCM) {
2435         msg = "oop fills not handled";
2436         break;
2437       }
2438       Node* value = n->in(MemNode::ValueIn);
2439       if (!lpt->is_invariant(value)) {
2440         msg  = "variant store value";
2441       } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
2442         msg = "not array address";
2443       }
2444       store = n;
2445       store_value = value;
2446     } else if (n->is_If() && n != head->loopexit()) {
2447       msg = "extra control flow";
2448       msg_node = n;
2449     }
2450   }
2451 
2452   if (store == NULL) {
2453     // No store in loop
2454     return false;
2455   }
2456 
2457   if (msg == NULL && head->stride_con() != 1) {
2458     // could handle negative strides too
2459     if (head->stride_con() < 0) {
2460       msg = "negative stride";
2461     } else {
2462       msg = "non-unit stride";
2463     }
2464   }
2465 
2466   if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
2467     msg = "can't handle store address";
2468     msg_node = store->in(MemNode::Address);
2469   }
2470 
2471   if (msg == NULL &&
2472       (!store->in(MemNode::Memory)->is_Phi() ||
2473        store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
2474     msg = "store memory isn't proper phi";
2475     msg_node = store->in(MemNode::Memory);
2476   }
2477 
2478   // Make sure there is an appropriate fill routine
2479   BasicType t = store->as_Mem()->memory_type();
2480   const char* fill_name;
2481   if (msg == NULL &&
2482       StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
2483     msg = "unsupported store";
2484     msg_node = store;
2485   }
2486 
2487   if (msg != NULL) {
2488 #ifndef PRODUCT
2489     if (TraceOptimizeFill) {
2490       tty->print_cr("not fill intrinsic candidate: %s", msg);
2491       if (msg_node != NULL) msg_node->dump();
2492     }
2493 #endif
2494     return false;
2495   }
2496 
2497   // Make sure the address expression can be handled.  It should be
2498   // head->phi * elsize + con.  head->phi might have a ConvI2L.
2499   Node* elements[4];
2500   Node* conv = NULL;
2501   bool found_index = false;
2502   int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
2503   for (int e = 0; e < count; e++) {
2504     Node* n = elements[e];
2505     if (n->is_Con() && con == NULL) {
2506       con = n;
2507     } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
2508       Node* value = n->in(1);
2509 #ifdef _LP64
2510       if (value->Opcode() == Op_ConvI2L) {
2511         conv = value;
2512         value = value->in(1);
2513       }
2514 #endif
2515       if (value != head->phi()) {
2516         msg = "unhandled shift in address";
2517       } else {
2518         if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) {
2519           msg = "scale doesn't match";
2520         } else {
2521           found_index = true;
2522           shift = n;
2523         }
2524       }
2525     } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
2526       if (n->in(1) == head->phi()) {
2527         found_index = true;
2528         conv = n;
2529       } else {
2530         msg = "unhandled input to ConvI2L";
2531       }
2532     } else if (n == head->phi()) {
2533       // no shift, check below for allowed cases
2534       found_index = true;
2535     } else {
2536       msg = "unhandled node in address";
2537       msg_node = n;
2538     }
2539   }
2540 
2541   if (count == -1) {
2542     msg = "malformed address expression";
2543     msg_node = store;
2544   }
2545 
2546   if (!found_index) {
2547     msg = "missing use of index";
2548   }
2549 
2550   // byte sized items won't have a shift
2551   if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
2552     msg = "can't find shift";
2553     msg_node = store;
2554   }
2555 
2556   if (msg != NULL) {
2557 #ifndef PRODUCT
2558     if (TraceOptimizeFill) {
2559       tty->print_cr("not fill intrinsic: %s", msg);
2560       if (msg_node != NULL) msg_node->dump();
2561     }
2562 #endif
2563     return false;
2564   }
2565 
2566   // No make sure all the other nodes in the loop can be handled
2567   VectorSet ok(Thread::current()->resource_area());
2568 
2569   // store related values are ok
2570   ok.set(store->_idx);
2571   ok.set(store->in(MemNode::Memory)->_idx);
2572 
2573   CountedLoopEndNode* loop_exit = head->loopexit();
2574   guarantee(loop_exit != NULL, "no loop exit node");
2575 
2576   // Loop structure is ok
2577   ok.set(head->_idx);
2578   ok.set(loop_exit->_idx);
2579   ok.set(head->phi()->_idx);
2580   ok.set(head->incr()->_idx);
2581   ok.set(loop_exit->cmp_node()->_idx);
2582   ok.set(loop_exit->in(1)->_idx);
2583 
2584   // Address elements are ok
2585   if (con)   ok.set(con->_idx);
2586   if (shift) ok.set(shift->_idx);
2587   if (conv)  ok.set(conv->_idx);
2588 
2589   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2590     Node* n = lpt->_body.at(i);
2591     if (n->outcnt() == 0) continue; // Ignore dead
2592     if (ok.test(n->_idx)) continue;
2593     // Backedge projection is ok
2594     if (n->is_IfTrue() && n->in(0) == loop_exit) continue;
2595     if (!n->is_AddP()) {
2596       msg = "unhandled node";
2597       msg_node = n;
2598       break;
2599     }
2600   }
2601 
2602   // Make sure no unexpected values are used outside the loop
2603   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2604     Node* n = lpt->_body.at(i);
2605     // These values can be replaced with other nodes if they are used
2606     // outside the loop.
2607     if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue;
2608     for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
2609       Node* use = iter.get();
2610       if (!lpt->_body.contains(use)) {
2611         msg = "node is used outside loop";
2612         // lpt->_body.dump();
2613         msg_node = n;
2614         break;
2615       }
2616     }
2617   }
2618 
2619 #ifdef ASSERT
2620   if (TraceOptimizeFill) {
2621     if (msg != NULL) {
2622       tty->print_cr("no fill intrinsic: %s", msg);
2623       if (msg_node != NULL) msg_node->dump();
2624     } else {
2625       tty->print_cr("fill intrinsic for:");
2626     }
2627     store->dump();
2628     if (Verbose) {
2629       lpt->_body.dump();
2630     }
2631   }
2632 #endif
2633 
2634   return msg == NULL;
2635 }
2636 
2637 
2638 
2639 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
2640   // Only for counted inner loops
2641   if (!lpt->is_counted() || !lpt->is_inner()) {
2642     return false;
2643   }
2644 
2645   // Must have constant stride
2646   CountedLoopNode* head = lpt->_head->as_CountedLoop();
2647   if (!head->is_valid_counted_loop() || !head->is_normal_loop()) {
2648     return false;
2649   }
2650 
2651   // Check that the body only contains a store of a loop invariant
2652   // value that is indexed by the loop phi.
2653   Node* store = NULL;
2654   Node* store_value = NULL;
2655   Node* shift = NULL;
2656   Node* offset = NULL;
2657   if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
2658     return false;
2659   }
2660 
2661 #ifndef PRODUCT
2662   if (TraceLoopOpts) {
2663     tty->print("ArrayFill    ");
2664     lpt->dump_head();
2665   }
2666 #endif
2667 
2668   // Now replace the whole loop body by a call to a fill routine that
2669   // covers the same region as the loop.
2670   Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
2671 
2672   // Build an expression for the beginning of the copy region
2673   Node* index = head->init_trip();
2674 #ifdef _LP64
2675   index = new (C) ConvI2LNode(index);
2676   _igvn.register_new_node_with_optimizer(index);
2677 #endif
2678   if (shift != NULL) {
2679     // byte arrays don't require a shift but others do.
2680     index = new (C) LShiftXNode(index, shift->in(2));
2681     _igvn.register_new_node_with_optimizer(index);
2682   }
2683   index = new (C) AddPNode(base, base, index);
2684   _igvn.register_new_node_with_optimizer(index);
2685   Node* from = new (C) AddPNode(base, index, offset);
2686   _igvn.register_new_node_with_optimizer(from);
2687   // Compute the number of elements to copy
2688   Node* len = new (C) SubINode(head->limit(), head->init_trip());
2689   _igvn.register_new_node_with_optimizer(len);
2690 
2691   BasicType t = store->as_Mem()->memory_type();
2692   bool aligned = false;
2693   if (offset != NULL && head->init_trip()->is_Con()) {
2694     int element_size = type2aelembytes(t);
2695     aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
2696   }
2697 
2698   // Build a call to the fill routine
2699   const char* fill_name;
2700   address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
2701   assert(fill != NULL, "what?");
2702 
2703   // Convert float/double to int/long for fill routines
2704   if (t == T_FLOAT) {
2705     store_value = new (C) MoveF2INode(store_value);
2706     _igvn.register_new_node_with_optimizer(store_value);
2707   } else if (t == T_DOUBLE) {
2708     store_value = new (C) MoveD2LNode(store_value);
2709     _igvn.register_new_node_with_optimizer(store_value);
2710   }
2711 
2712   Node* mem_phi = store->in(MemNode::Memory);
2713   Node* result_ctrl;
2714   Node* result_mem;
2715   const TypeFunc* call_type = OptoRuntime::array_fill_Type();
2716   CallLeafNode *call = new (C) CallLeafNoFPNode(call_type, fill,
2717                                                 fill_name, TypeAryPtr::get_array_body_type(t));
2718   call->init_req(TypeFunc::Parms+0, from);
2719   call->init_req(TypeFunc::Parms+1, store_value);
2720 #ifdef _LP64
2721   len = new (C) ConvI2LNode(len);
2722   _igvn.register_new_node_with_optimizer(len);
2723 #endif
2724   call->init_req(TypeFunc::Parms+2, len);
2725 #ifdef _LP64
2726   call->init_req(TypeFunc::Parms+3, C->top());
2727 #endif
2728   call->init_req( TypeFunc::Control, head->init_control());
2729   call->init_req( TypeFunc::I_O    , C->top() )        ;   // does no i/o
2730   call->init_req( TypeFunc::Memory ,  mem_phi->in(LoopNode::EntryControl) );
2731   call->init_req( TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr) );
2732   call->init_req( TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr) );
2733   _igvn.register_new_node_with_optimizer(call);
2734   result_ctrl = new (C) ProjNode(call,TypeFunc::Control);
2735   _igvn.register_new_node_with_optimizer(result_ctrl);
2736   result_mem = new (C) ProjNode(call,TypeFunc::Memory);
2737   _igvn.register_new_node_with_optimizer(result_mem);
2738 
2739 /* Disable following optimization until proper fix (add missing checks).
2740 
2741   // If this fill is tightly coupled to an allocation and overwrites
2742   // the whole body, allow it to take over the zeroing.
2743   AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
2744   if (alloc != NULL && alloc->is_AllocateArray()) {
2745     Node* length = alloc->as_AllocateArray()->Ideal_length();
2746     if (head->limit() == length &&
2747         head->init_trip() == _igvn.intcon(0)) {
2748       if (TraceOptimizeFill) {
2749         tty->print_cr("Eliminated zeroing in allocation");
2750       }
2751       alloc->maybe_set_complete(&_igvn);
2752     } else {
2753 #ifdef ASSERT
2754       if (TraceOptimizeFill) {
2755         tty->print_cr("filling array but bounds don't match");
2756         alloc->dump();
2757         head->init_trip()->dump();
2758         head->limit()->dump();
2759         length->dump();
2760       }
2761 #endif
2762     }
2763   }
2764 */
2765 
2766   // Redirect the old control and memory edges that are outside the loop.
2767   Node* exit = head->loopexit()->proj_out(0);
2768   // Sometimes the memory phi of the head is used as the outgoing
2769   // state of the loop.  It's safe in this case to replace it with the
2770   // result_mem.
2771   _igvn.replace_node(store->in(MemNode::Memory), result_mem);
2772   _igvn.replace_node(exit, result_ctrl);
2773   _igvn.replace_node(store, result_mem);
2774   // Any uses the increment outside of the loop become the loop limit.
2775   _igvn.replace_node(head->incr(), head->limit());
2776 
2777   // Disconnect the head from the loop.
2778   for (uint i = 0; i < lpt->_body.size(); i++) {
2779     Node* n = lpt->_body.at(i);
2780     _igvn.replace_node(n, C->top());
2781   }
2782 
2783   return true;
2784 }