1 /*
   2  * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "compiler/compileLog.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "opto/addnode.hpp"
  29 #include "opto/callnode.hpp"
  30 #include "opto/castnode.hpp"
  31 #include "opto/connode.hpp"
  32 #include "opto/convertnode.hpp"
  33 #include "opto/divnode.hpp"
  34 #include "opto/loopnode.hpp"
  35 #include "opto/mulnode.hpp"
  36 #include "opto/movenode.hpp"
  37 #include "opto/opaquenode.hpp"
  38 #include "opto/rootnode.hpp"
  39 #include "opto/runtime.hpp"
  40 #include "opto/subnode.hpp"
  41 #include "opto/superword.hpp"
  42 #include "opto/vectornode.hpp"
  43 
  44 //------------------------------is_loop_exit-----------------------------------
  45 // Given an IfNode, return the loop-exiting projection or NULL if both
  46 // arms remain in the loop.
  47 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
  48   if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
  49   PhaseIdealLoop *phase = _phase;
  50   // Test is an IfNode, has 2 projections.  If BOTH are in the loop
  51   // we need loop unswitching instead of peeling.
  52   if( !is_member(phase->get_loop( iff->raw_out(0) )) )
  53     return iff->raw_out(0);
  54   if( !is_member(phase->get_loop( iff->raw_out(1) )) )
  55     return iff->raw_out(1);
  56   return NULL;
  57 }
  58 
  59 
  60 //=============================================================================
  61 
  62 
  63 //------------------------------record_for_igvn----------------------------
  64 // Put loop body on igvn work list
  65 void IdealLoopTree::record_for_igvn() {
  66   for( uint i = 0; i < _body.size(); i++ ) {
  67     Node *n = _body.at(i);
  68     _phase->_igvn._worklist.push(n);
  69   }
  70 }
  71 
  72 //------------------------------compute_exact_trip_count-----------------------
  73 // Compute loop exact trip count if possible. Do not recalculate trip count for
  74 // split loops (pre-main-post) which have their limits and inits behind Opaque node.
  75 void IdealLoopTree::compute_exact_trip_count( PhaseIdealLoop *phase ) {
  76   if (!_head->as_Loop()->is_valid_counted_loop()) {
  77     return;
  78   }
  79   CountedLoopNode* cl = _head->as_CountedLoop();
  80   // Trip count may become nonexact for iteration split loops since
  81   // RCE modifies limits. Note, _trip_count value is not reset since
  82   // it is used to limit unrolling of main loop.
  83   cl->set_nonexact_trip_count();
  84 
  85   // Loop's test should be part of loop.
  86   if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
  87     return; // Infinite loop
  88 
  89 #ifdef ASSERT
  90   BoolTest::mask bt = cl->loopexit()->test_trip();
  91   assert(bt == BoolTest::lt || bt == BoolTest::gt ||
  92          bt == BoolTest::ne, "canonical test is expected");
  93 #endif
  94 
  95   Node* init_n = cl->init_trip();
  96   Node* limit_n = cl->limit();
  97   if (init_n  != NULL &&  init_n->is_Con() &&
  98       limit_n != NULL && limit_n->is_Con()) {
  99     // Use longs to avoid integer overflow.
 100     int stride_con  = cl->stride_con();
 101     jlong init_con   = cl->init_trip()->get_int();
 102     jlong limit_con  = cl->limit()->get_int();
 103     int stride_m    = stride_con - (stride_con > 0 ? 1 : -1);
 104     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
 105     if (trip_count > 0 && (julong)trip_count < (julong)max_juint) {
 106       // Set exact trip count.
 107       cl->set_exact_trip_count((uint)trip_count);
 108     }
 109   }
 110 }
 111 
 112 //------------------------------compute_profile_trip_cnt----------------------------
 113 // Compute loop trip count from profile data as
 114 //    (backedge_count + loop_exit_count) / loop_exit_count
 115 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
 116   if (!_head->is_CountedLoop()) {
 117     return;
 118   }
 119   CountedLoopNode* head = _head->as_CountedLoop();
 120   if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
 121     return; // Already computed
 122   }
 123   float trip_cnt = (float)max_jint; // default is big
 124 
 125   Node* back = head->in(LoopNode::LoopBackControl);
 126   while (back != head) {
 127     if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
 128         back->in(0) &&
 129         back->in(0)->is_If() &&
 130         back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
 131         back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
 132       break;
 133     }
 134     back = phase->idom(back);
 135   }
 136   if (back != head) {
 137     assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
 138            back->in(0), "if-projection exists");
 139     IfNode* back_if = back->in(0)->as_If();
 140     float loop_back_cnt = back_if->_fcnt * back_if->_prob;
 141 
 142     // Now compute a loop exit count
 143     float loop_exit_cnt = 0.0f;
 144     for( uint i = 0; i < _body.size(); i++ ) {
 145       Node *n = _body[i];
 146       if( n->is_If() ) {
 147         IfNode *iff = n->as_If();
 148         if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
 149           Node *exit = is_loop_exit(iff);
 150           if( exit ) {
 151             float exit_prob = iff->_prob;
 152             if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
 153             if (exit_prob > PROB_MIN) {
 154               float exit_cnt = iff->_fcnt * exit_prob;
 155               loop_exit_cnt += exit_cnt;
 156             }
 157           }
 158         }
 159       }
 160     }
 161     if (loop_exit_cnt > 0.0f) {
 162       trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
 163     } else {
 164       // No exit count so use
 165       trip_cnt = loop_back_cnt;
 166     }
 167   }
 168 #ifndef PRODUCT
 169   if (TraceProfileTripCount) {
 170     tty->print_cr("compute_profile_trip_cnt  lp: %d cnt: %f\n", head->_idx, trip_cnt);
 171   }
 172 #endif
 173   head->set_profile_trip_cnt(trip_cnt);
 174 }
 175 
 176 //---------------------is_invariant_addition-----------------------------
 177 // Return nonzero index of invariant operand for an Add or Sub
 178 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
 179 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
 180   int op = n->Opcode();
 181   if (op == Op_AddI || op == Op_SubI) {
 182     bool in1_invar = this->is_invariant(n->in(1));
 183     bool in2_invar = this->is_invariant(n->in(2));
 184     if (in1_invar && !in2_invar) return 1;
 185     if (!in1_invar && in2_invar) return 2;
 186   }
 187   return 0;
 188 }
 189 
 190 //---------------------reassociate_add_sub-----------------------------
 191 // Reassociate invariant add and subtract expressions:
 192 //
 193 // inv1 + (x + inv2)  =>  ( inv1 + inv2) + x
 194 // (x + inv2) + inv1  =>  ( inv1 + inv2) + x
 195 // inv1 + (x - inv2)  =>  ( inv1 - inv2) + x
 196 // inv1 - (inv2 - x)  =>  ( inv1 - inv2) + x
 197 // (x + inv2) - inv1  =>  (-inv1 + inv2) + x
 198 // (x - inv2) + inv1  =>  ( inv1 - inv2) + x
 199 // (x - inv2) - inv1  =>  (-inv1 - inv2) + x
 200 // inv1 + (inv2 - x)  =>  ( inv1 + inv2) - x
 201 // inv1 - (x - inv2)  =>  ( inv1 + inv2) - x
 202 // (inv2 - x) + inv1  =>  ( inv1 + inv2) - x
 203 // (inv2 - x) - inv1  =>  (-inv1 + inv2) - x
 204 // inv1 - (x + inv2)  =>  ( inv1 - inv2) - x
 205 //
 206 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
 207   if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
 208   if (is_invariant(n1)) return NULL;
 209   int inv1_idx = is_invariant_addition(n1, phase);
 210   if (!inv1_idx) return NULL;
 211   // Don't mess with add of constant (igvn moves them to expression tree root.)
 212   if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
 213   Node* inv1 = n1->in(inv1_idx);
 214   Node* n2 = n1->in(3 - inv1_idx);
 215   int inv2_idx = is_invariant_addition(n2, phase);
 216   if (!inv2_idx) return NULL;
 217   Node* x    = n2->in(3 - inv2_idx);
 218   Node* inv2 = n2->in(inv2_idx);
 219 
 220   bool neg_x    = n2->is_Sub() && inv2_idx == 1;
 221   bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
 222   bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
 223   if (n1->is_Sub() && inv1_idx == 1) {
 224     neg_x    = !neg_x;
 225     neg_inv2 = !neg_inv2;
 226   }
 227   Node* inv1_c = phase->get_ctrl(inv1);
 228   Node* inv2_c = phase->get_ctrl(inv2);
 229   Node* n_inv1;
 230   if (neg_inv1) {
 231     Node *zero = phase->_igvn.intcon(0);
 232     phase->set_ctrl(zero, phase->C->root());
 233     n_inv1 = new SubINode(zero, inv1);
 234     phase->register_new_node(n_inv1, inv1_c);
 235   } else {
 236     n_inv1 = inv1;
 237   }
 238   Node* inv;
 239   if (neg_inv2) {
 240     inv = new SubINode(n_inv1, inv2);
 241   } else {
 242     inv = new AddINode(n_inv1, inv2);
 243   }
 244   phase->register_new_node(inv, phase->get_early_ctrl(inv));
 245 
 246   Node* addx;
 247   if (neg_x) {
 248     addx = new SubINode(inv, x);
 249   } else {
 250     addx = new AddINode(x, inv);
 251   }
 252   phase->register_new_node(addx, phase->get_ctrl(x));
 253   phase->_igvn.replace_node(n1, addx);
 254   assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
 255   _body.yank(n1);
 256   return addx;
 257 }
 258 
 259 //---------------------reassociate_invariants-----------------------------
 260 // Reassociate invariant expressions:
 261 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
 262   for (int i = _body.size() - 1; i >= 0; i--) {
 263     Node *n = _body.at(i);
 264     for (int j = 0; j < 5; j++) {
 265       Node* nn = reassociate_add_sub(n, phase);
 266       if (nn == NULL) break;
 267       n = nn; // again
 268     };
 269   }
 270 }
 271 
 272 //------------------------------policy_peeling---------------------------------
 273 // Return TRUE or FALSE if the loop should be peeled or not.  Peel if we can
 274 // make some loop-invariant test (usually a null-check) happen before the loop.
 275 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
 276   Node *test = ((IdealLoopTree*)this)->tail();
 277   int  body_size = ((IdealLoopTree*)this)->_body.size();
 278   // Peeling does loop cloning which can result in O(N^2) node construction
 279   if( body_size > 255 /* Prevent overflow for large body_size */
 280       || (body_size * body_size + phase->C->live_nodes()) > phase->C->max_node_limit() ) {
 281     return false;           // too large to safely clone
 282   }
 283 
 284   // check for vectorized loops, any peeling done was already applied
 285   if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) return false;
 286 
 287   while( test != _head ) {      // Scan till run off top of loop
 288     if( test->is_If() ) {       // Test?
 289       Node *ctrl = phase->get_ctrl(test->in(1));
 290       if (ctrl->is_top())
 291         return false;           // Found dead test on live IF?  No peeling!
 292       // Standard IF only has one input value to check for loop invariance
 293       assert(test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd || test->Opcode() == Op_RangeCheck, "Check this code when new subtype is added");
 294       // Condition is not a member of this loop?
 295       if( !is_member(phase->get_loop(ctrl)) &&
 296           is_loop_exit(test) )
 297         return true;            // Found reason to peel!
 298     }
 299     // Walk up dominators to loop _head looking for test which is
 300     // executed on every path thru loop.
 301     test = phase->idom(test);
 302   }
 303   return false;
 304 }
 305 
 306 //------------------------------peeled_dom_test_elim---------------------------
 307 // If we got the effect of peeling, either by actually peeling or by making
 308 // a pre-loop which must execute at least once, we can remove all
 309 // loop-invariant dominated tests in the main body.
 310 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
 311   bool progress = true;
 312   while( progress ) {
 313     progress = false;           // Reset for next iteration
 314     Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
 315     Node *test = prev->in(0);
 316     while( test != loop->_head ) { // Scan till run off top of loop
 317 
 318       int p_op = prev->Opcode();
 319       if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
 320           test->is_If() &&      // Test?
 321           !test->in(1)->is_Con() && // And not already obvious?
 322           // Condition is not a member of this loop?
 323           !loop->is_member(get_loop(get_ctrl(test->in(1))))){
 324         // Walk loop body looking for instances of this test
 325         for( uint i = 0; i < loop->_body.size(); i++ ) {
 326           Node *n = loop->_body.at(i);
 327           if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
 328             // IfNode was dominated by version in peeled loop body
 329             progress = true;
 330             dominated_by( old_new[prev->_idx], n );
 331           }
 332         }
 333       }
 334       prev = test;
 335       test = idom(test);
 336     } // End of scan tests in loop
 337 
 338   } // End of while( progress )
 339 }
 340 
 341 //------------------------------do_peeling-------------------------------------
 342 // Peel the first iteration of the given loop.
 343 // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 344 //         The pre-loop illegally has 2 control users (old & new loops).
 345 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 346 //         Do this by making the old-loop fall-in edges act as if they came
 347 //         around the loopback from the prior iteration (follow the old-loop
 348 //         backedges) and then map to the new peeled iteration.  This leaves
 349 //         the pre-loop with only 1 user (the new peeled iteration), but the
 350 //         peeled-loop backedge has 2 users.
 351 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 352 //         extra backedge user.
 353 //
 354 //                   orig
 355 //
 356 //                  stmt1
 357 //                    |
 358 //                    v
 359 //              loop predicate
 360 //                    |
 361 //                    v
 362 //                   loop<----+
 363 //                     |      |
 364 //                   stmt2    |
 365 //                     |      |
 366 //                     v      |
 367 //                    if      ^
 368 //                   / \      |
 369 //                  /   \     |
 370 //                 v     v    |
 371 //               false true   |
 372 //               /       \    |
 373 //              /         ----+
 374 //             |
 375 //             v
 376 //           exit
 377 //
 378 //
 379 //            after clone loop
 380 //
 381 //                   stmt1
 382 //                     |
 383 //                     v
 384 //               loop predicate
 385 //                 /       \
 386 //        clone   /         \   orig
 387 //               /           \
 388 //              /             \
 389 //             v               v
 390 //   +---->loop clone          loop<----+
 391 //   |      |                    |      |
 392 //   |    stmt2 clone          stmt2    |
 393 //   |      |                    |      |
 394 //   |      v                    v      |
 395 //   ^      if clone            If      ^
 396 //   |      / \                / \      |
 397 //   |     /   \              /   \     |
 398 //   |    v     v            v     v    |
 399 //   |    true  false      false true   |
 400 //   |    /         \      /       \    |
 401 //   +----           \    /         ----+
 402 //                    \  /
 403 //                    1v v2
 404 //                  region
 405 //                     |
 406 //                     v
 407 //                   exit
 408 //
 409 //
 410 //         after peel and predicate move
 411 //
 412 //                   stmt1
 413 //                    /
 414 //                   /
 415 //        clone     /            orig
 416 //                 /
 417 //                /              +----------+
 418 //               /               |          |
 419 //              /          loop predicate   |
 420 //             /                 |          |
 421 //            v                  v          |
 422 //   TOP-->loop clone          loop<----+   |
 423 //          |                    |      |   |
 424 //        stmt2 clone          stmt2    |   |
 425 //          |                    |      |   ^
 426 //          v                    v      |   |
 427 //          if clone            If      ^   |
 428 //          / \                / \      |   |
 429 //         /   \              /   \     |   |
 430 //        v     v            v     v    |   |
 431 //      true   false      false  true   |   |
 432 //        |         \      /       \    |   |
 433 //        |          \    /         ----+   ^
 434 //        |           \  /                  |
 435 //        |           1v v2                 |
 436 //        v         region                  |
 437 //        |            |                    |
 438 //        |            v                    |
 439 //        |          exit                   |
 440 //        |                                 |
 441 //        +--------------->-----------------+
 442 //
 443 //
 444 //              final graph
 445 //
 446 //                  stmt1
 447 //                    |
 448 //                    v
 449 //                  stmt2 clone
 450 //                    |
 451 //                    v
 452 //                   if clone
 453 //                  / |
 454 //                 /  |
 455 //                v   v
 456 //            false  true
 457 //             |      |
 458 //             |      v
 459 //             | loop predicate
 460 //             |      |
 461 //             |      v
 462 //             |     loop<----+
 463 //             |      |       |
 464 //             |    stmt2     |
 465 //             |      |       |
 466 //             |      v       |
 467 //             v      if      ^
 468 //             |     /  \     |
 469 //             |    /    \    |
 470 //             |   v     v    |
 471 //             | false  true  |
 472 //             |  |        \  |
 473 //             v  v         --+
 474 //            region
 475 //              |
 476 //              v
 477 //             exit
 478 //
 479 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
 480 
 481   C->set_major_progress();
 482   // Peeling a 'main' loop in a pre/main/post situation obfuscates the
 483   // 'pre' loop from the main and the 'pre' can no longer have its
 484   // iterations adjusted.  Therefore, we need to declare this loop as
 485   // no longer a 'main' loop; it will need new pre and post loops before
 486   // we can do further RCE.
 487 #ifndef PRODUCT
 488   if (TraceLoopOpts) {
 489     tty->print("Peel         ");
 490     loop->dump_head();
 491   }
 492 #endif
 493   Node* head = loop->_head;
 494   bool counted_loop = head->is_CountedLoop();
 495   if (counted_loop) {
 496     CountedLoopNode *cl = head->as_CountedLoop();
 497     assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
 498     cl->set_trip_count(cl->trip_count() - 1);
 499     if (cl->is_main_loop()) {
 500       cl->set_normal_loop();
 501 #ifndef PRODUCT
 502       if (PrintOpto && VerifyLoopOptimizations) {
 503         tty->print("Peeling a 'main' loop; resetting to 'normal' ");
 504         loop->dump_head();
 505       }
 506 #endif
 507     }
 508   }
 509   Node* entry = head->in(LoopNode::EntryControl);
 510 
 511   // Step 1: Clone the loop body.  The clone becomes the peeled iteration.
 512   //         The pre-loop illegally has 2 control users (old & new loops).
 513   clone_loop( loop, old_new, dom_depth(head) );
 514 
 515   // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
 516   //         Do this by making the old-loop fall-in edges act as if they came
 517   //         around the loopback from the prior iteration (follow the old-loop
 518   //         backedges) and then map to the new peeled iteration.  This leaves
 519   //         the pre-loop with only 1 user (the new peeled iteration), but the
 520   //         peeled-loop backedge has 2 users.
 521   Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx];
 522   _igvn.hash_delete(head);
 523   head->set_req(LoopNode::EntryControl, new_entry);
 524   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
 525     Node* old = head->fast_out(j);
 526     if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
 527       Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
 528       if (!new_exit_value )     // Backedge value is ALSO loop invariant?
 529         // Then loop body backedge value remains the same.
 530         new_exit_value = old->in(LoopNode::LoopBackControl);
 531       _igvn.hash_delete(old);
 532       old->set_req(LoopNode::EntryControl, new_exit_value);
 533     }
 534   }
 535 
 536 
 537   // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
 538   //         extra backedge user.
 539   Node* new_head = old_new[head->_idx];
 540   _igvn.hash_delete(new_head);
 541   new_head->set_req(LoopNode::LoopBackControl, C->top());
 542   for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
 543     Node* use = new_head->fast_out(j2);
 544     if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
 545       _igvn.hash_delete(use);
 546       use->set_req(LoopNode::LoopBackControl, C->top());
 547     }
 548   }
 549 
 550 
 551   // Step 4: Correct dom-depth info.  Set to loop-head depth.
 552   int dd = dom_depth(head);
 553   set_idom(head, head->in(1), dd);
 554   for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
 555     Node *old = loop->_body.at(j3);
 556     Node *nnn = old_new[old->_idx];
 557     if (!has_ctrl(nnn))
 558       set_idom(nnn, idom(nnn), dd-1);
 559   }
 560 
 561   // Now force out all loop-invariant dominating tests.  The optimizer
 562   // finds some, but we _know_ they are all useless.
 563   peeled_dom_test_elim(loop,old_new);
 564 
 565   loop->record_for_igvn();
 566 }
 567 
 568 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop
 569 
 570 //------------------------------policy_maximally_unroll------------------------
 571 // Calculate exact loop trip count and return true if loop can be maximally
 572 // unrolled.
 573 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
 574   CountedLoopNode *cl = _head->as_CountedLoop();
 575   assert(cl->is_normal_loop(), "");
 576   if (!cl->is_valid_counted_loop())
 577     return false; // Malformed counted loop
 578 
 579   if (!cl->has_exact_trip_count()) {
 580     // Trip count is not exact.
 581     return false;
 582   }
 583 
 584   uint trip_count = cl->trip_count();
 585   // Note, max_juint is used to indicate unknown trip count.
 586   assert(trip_count > 1, "one iteration loop should be optimized out already");
 587   assert(trip_count < max_juint, "exact trip_count should be less than max_uint.");
 588 
 589   // Real policy: if we maximally unroll, does it get too big?
 590   // Allow the unrolled mess to get larger than standard loop
 591   // size.  After all, it will no longer be a loop.
 592   uint body_size    = _body.size();
 593   uint unroll_limit = (uint)LoopUnrollLimit * 4;
 594   assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
 595   if (trip_count > unroll_limit || body_size > unroll_limit) {
 596     return false;
 597   }
 598 
 599   // Fully unroll a loop with few iterations regardless next
 600   // conditions since following loop optimizations will split
 601   // such loop anyway (pre-main-post).
 602   if (trip_count <= 3)
 603     return true;
 604 
 605   // Take into account that after unroll conjoined heads and tails will fold,
 606   // otherwise policy_unroll() may allow more unrolling than max unrolling.
 607   uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count;
 608   uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE;
 609   if (body_size != tst_body_size) // Check for int overflow
 610     return false;
 611   if (new_body_size > unroll_limit ||
 612       // Unrolling can result in a large amount of node construction
 613       new_body_size >= phase->C->max_node_limit() - phase->C->live_nodes()) {
 614     return false;
 615   }
 616 
 617   // Do not unroll a loop with String intrinsics code.
 618   // String intrinsics are large and have loops.
 619   for (uint k = 0; k < _body.size(); k++) {
 620     Node* n = _body.at(k);
 621     switch (n->Opcode()) {
 622       case Op_StrComp:
 623       case Op_StrEquals:
 624       case Op_StrIndexOf:
 625       case Op_StrIndexOfChar:
 626       case Op_EncodeISOArray:
 627       case Op_AryEq:
 628       case Op_HasNegatives: {
 629         return false;
 630       }
 631 #if INCLUDE_RTM_OPT
 632       case Op_FastLock:
 633       case Op_FastUnlock: {
 634         // Don't unroll RTM locking code because it is large.
 635         if (UseRTMLocking) {
 636           return false;
 637         }
 638       }
 639 #endif
 640     } // switch
 641   }
 642 
 643   return true; // Do maximally unroll
 644 }
 645 
 646 
 647 //------------------------------policy_unroll----------------------------------
 648 // Return TRUE or FALSE if the loop should be unrolled or not.  Unroll if
 649 // the loop is a CountedLoop and the body is small enough.
 650 bool IdealLoopTree::policy_unroll(PhaseIdealLoop *phase) {
 651 
 652   CountedLoopNode *cl = _head->as_CountedLoop();
 653   assert(cl->is_normal_loop() || cl->is_main_loop(), "");
 654 
 655   if (!cl->is_valid_counted_loop())
 656     return false; // Malformed counted loop
 657 
 658   // Protect against over-unrolling.
 659   // After split at least one iteration will be executed in pre-loop.
 660   if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false;
 661 
 662   _local_loop_unroll_limit = LoopUnrollLimit;
 663   _local_loop_unroll_factor = 4;
 664   int future_unroll_ct = cl->unrolled_count() * 2;
 665   if (!cl->do_unroll_only()) {
 666     if (future_unroll_ct > LoopMaxUnroll) return false;
 667   } else {
 668     // obey user constraints on vector mapped loops with additional unrolling applied
 669     int unroll_constraint = (cl->slp_max_unroll()) ? cl->slp_max_unroll() : 1;
 670     if ((future_unroll_ct / unroll_constraint) > LoopMaxUnroll) return false;
 671   }
 672 
 673   // Check for initial stride being a small enough constant
 674   if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false;
 675 
 676   // Don't unroll if the next round of unrolling would push us
 677   // over the expected trip count of the loop.  One is subtracted
 678   // from the expected trip count because the pre-loop normally
 679   // executes 1 iteration.
 680   if (UnrollLimitForProfileCheck > 0 &&
 681       cl->profile_trip_cnt() != COUNT_UNKNOWN &&
 682       future_unroll_ct        > UnrollLimitForProfileCheck &&
 683       (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
 684     return false;
 685   }
 686 
 687   // When unroll count is greater than LoopUnrollMin, don't unroll if:
 688   //   the residual iterations are more than 10% of the trip count
 689   //   and rounds of "unroll,optimize" are not making significant progress
 690   //   Progress defined as current size less than 20% larger than previous size.
 691   if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
 692       future_unroll_ct > LoopUnrollMin &&
 693       (future_unroll_ct - 1) * (100 / LoopPercentProfileLimit) > cl->profile_trip_cnt() &&
 694       1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
 695     return false;
 696   }
 697 
 698   Node *init_n = cl->init_trip();
 699   Node *limit_n = cl->limit();
 700   int stride_con = cl->stride_con();
 701   // Non-constant bounds.
 702   // Protect against over-unrolling when init or/and limit are not constant
 703   // (so that trip_count's init value is maxint) but iv range is known.
 704   if (init_n   == NULL || !init_n->is_Con()  ||
 705       limit_n  == NULL || !limit_n->is_Con()) {
 706     Node* phi = cl->phi();
 707     if (phi != NULL) {
 708       assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
 709       const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
 710       int next_stride = stride_con * 2; // stride after this unroll
 711       if (next_stride > 0) {
 712         if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
 713             iv_type->_lo + next_stride >  iv_type->_hi) {
 714           return false;  // over-unrolling
 715         }
 716       } else if (next_stride < 0) {
 717         if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
 718             iv_type->_hi + next_stride <  iv_type->_lo) {
 719           return false;  // over-unrolling
 720         }
 721       }
 722     }
 723   }
 724 
 725   // After unroll limit will be adjusted: new_limit = limit-stride.
 726   // Bailout if adjustment overflow.
 727   const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
 728   if (stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi) ||
 729       stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo))
 730     return false;  // overflow
 731 
 732   // Adjust body_size to determine if we unroll or not
 733   uint body_size = _body.size();
 734   // Key test to unroll loop in CRC32 java code
 735   int xors_in_loop = 0;
 736   // Also count ModL, DivL and MulL which expand mightly
 737   for (uint k = 0; k < _body.size(); k++) {
 738     Node* n = _body.at(k);
 739     switch (n->Opcode()) {
 740       case Op_XorI: xors_in_loop++; break; // CRC32 java code
 741       case Op_ModL: body_size += 30; break;
 742       case Op_DivL: body_size += 30; break;
 743       case Op_MulL: body_size += 10; break;
 744       case Op_StrComp:
 745       case Op_StrEquals:
 746       case Op_StrIndexOf:
 747       case Op_StrIndexOfChar:
 748       case Op_EncodeISOArray:
 749       case Op_AryEq:
 750       case Op_HasNegatives: {
 751         // Do not unroll a loop with String intrinsics code.
 752         // String intrinsics are large and have loops.
 753         return false;
 754       }
 755 #if INCLUDE_RTM_OPT
 756       case Op_FastLock:
 757       case Op_FastUnlock: {
 758         // Don't unroll RTM locking code because it is large.
 759         if (UseRTMLocking) {
 760           return false;
 761         }
 762       }
 763 #endif
 764     } // switch
 765   }
 766 
 767   if (UseSuperWord) {
 768     if (!cl->is_reduction_loop()) {
 769       phase->mark_reductions(this);
 770     }
 771 
 772     // Only attempt slp analysis when user controls do not prohibit it
 773     if (LoopMaxUnroll > _local_loop_unroll_factor) {
 774       // Once policy_slp_analysis succeeds, mark the loop with the
 775       // maximal unroll factor so that we minimize analysis passes
 776       if (future_unroll_ct >= _local_loop_unroll_factor) {
 777         policy_unroll_slp_analysis(cl, phase, future_unroll_ct);
 778       }
 779     }
 780   }
 781 
 782   int slp_max_unroll_factor = cl->slp_max_unroll();
 783   if (cl->has_passed_slp()) {
 784     if (slp_max_unroll_factor >= future_unroll_ct) return true;
 785     // Normal case: loop too big
 786     return false;
 787   }
 788 
 789   // Check for being too big
 790   if (body_size > (uint)_local_loop_unroll_limit) {
 791     if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
 792     // Normal case: loop too big
 793     return false;
 794   }
 795 
 796   if (cl->do_unroll_only()) {
 797     if (TraceSuperWordLoopUnrollAnalysis) {
 798       tty->print_cr("policy_unroll passed vector loop(vlen=%d,factor = %d)\n", slp_max_unroll_factor, future_unroll_ct);
 799     }
 800   }
 801 
 802   // Unroll once!  (Each trip will soon do double iterations)
 803   return true;
 804 }
 805 
 806 void IdealLoopTree::policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct) {
 807   // Enable this functionality target by target as needed
 808   if (SuperWordLoopUnrollAnalysis) {
 809     if (!cl->was_slp_analyzed()) {
 810       SuperWord sw(phase);
 811       sw.transform_loop(this, false);
 812 
 813       // If the loop is slp canonical analyze it
 814       if (sw.early_return() == false) {
 815         sw.unrolling_analysis(_local_loop_unroll_factor);
 816       }
 817     }
 818 
 819     if (cl->has_passed_slp()) {
 820       int slp_max_unroll_factor = cl->slp_max_unroll();
 821       if (slp_max_unroll_factor >= future_unroll_ct) {
 822         int new_limit = cl->node_count_before_unroll() * slp_max_unroll_factor;
 823         if (new_limit > LoopUnrollLimit) {
 824           if (TraceSuperWordLoopUnrollAnalysis) {
 825             tty->print_cr("slp analysis unroll=%d, default limit=%d\n", new_limit, _local_loop_unroll_limit);
 826           }
 827           _local_loop_unroll_limit = new_limit;
 828         }
 829       }
 830     }
 831   }
 832 }
 833 
 834 //------------------------------policy_align-----------------------------------
 835 // Return TRUE or FALSE if the loop should be cache-line aligned.  Gather the
 836 // expression that does the alignment.  Note that only one array base can be
 837 // aligned in a loop (unless the VM guarantees mutual alignment).  Note that
 838 // if we vectorize short memory ops into longer memory ops, we may want to
 839 // increase alignment.
 840 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
 841   return false;
 842 }
 843 
 844 //------------------------------policy_range_check-----------------------------
 845 // Return TRUE or FALSE if the loop should be range-check-eliminated.
 846 // Actually we do iteration-splitting, a more powerful form of RCE.
 847 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
 848   if (!RangeCheckElimination) return false;
 849 
 850   CountedLoopNode *cl = _head->as_CountedLoop();
 851   // If we unrolled with no intention of doing RCE and we later
 852   // changed our minds, we got no pre-loop.  Either we need to
 853   // make a new pre-loop, or we gotta disallow RCE.
 854   if (cl->is_main_no_pre_loop()) return false; // Disallowed for now.
 855   Node *trip_counter = cl->phi();
 856 
 857   // check for vectorized loops, some opts are no longer needed
 858   if (cl->do_unroll_only()) return false;
 859 
 860   // Check loop body for tests of trip-counter plus loop-invariant vs
 861   // loop-invariant.
 862   for (uint i = 0; i < _body.size(); i++) {
 863     Node *iff = _body[i];
 864     if (iff->Opcode() == Op_If ||
 865         iff->Opcode() == Op_RangeCheck) { // Test?
 866 
 867       // Comparing trip+off vs limit
 868       Node *bol = iff->in(1);
 869       if (bol->req() != 2) continue; // dead constant test
 870       if (!bol->is_Bool()) {
 871         assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
 872         continue;
 873       }
 874       if (bol->as_Bool()->_test._test == BoolTest::ne)
 875         continue; // not RC
 876 
 877       Node *cmp = bol->in(1);
 878       Node *rc_exp = cmp->in(1);
 879       Node *limit = cmp->in(2);
 880 
 881       Node *limit_c = phase->get_ctrl(limit);
 882       if( limit_c == phase->C->top() )
 883         return false;           // Found dead test on live IF?  No RCE!
 884       if( is_member(phase->get_loop(limit_c) ) ) {
 885         // Compare might have operands swapped; commute them
 886         rc_exp = cmp->in(2);
 887         limit  = cmp->in(1);
 888         limit_c = phase->get_ctrl(limit);
 889         if( is_member(phase->get_loop(limit_c) ) )
 890           continue;             // Both inputs are loop varying; cannot RCE
 891       }
 892 
 893       if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
 894         continue;
 895       }
 896       // Yeah!  Found a test like 'trip+off vs limit'
 897       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
 898       // we need loop unswitching instead of iteration splitting.
 899       if( is_loop_exit(iff) )
 900         return true;            // Found reason to split iterations
 901     } // End of is IF
 902   }
 903 
 904   return false;
 905 }
 906 
 907 //------------------------------policy_peel_only-------------------------------
 908 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned.  Useful
 909 // for unrolling loops with NO array accesses.
 910 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
 911   // check for vectorized loops, any peeling done was already applied
 912   if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) return false;
 913 
 914   for( uint i = 0; i < _body.size(); i++ )
 915     if( _body[i]->is_Mem() )
 916       return false;
 917 
 918   // No memory accesses at all!
 919   return true;
 920 }
 921 
 922 //------------------------------clone_up_backedge_goo--------------------------
 923 // If Node n lives in the back_ctrl block and cannot float, we clone a private
 924 // version of n in preheader_ctrl block and return that, otherwise return n.
 925 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) {
 926   if( get_ctrl(n) != back_ctrl ) return n;
 927 
 928   // Only visit once
 929   if (visited.test_set(n->_idx)) {
 930     Node *x = clones.find(n->_idx);
 931     if (x != NULL)
 932       return x;
 933     return n;
 934   }
 935 
 936   Node *x = NULL;               // If required, a clone of 'n'
 937   // Check for 'n' being pinned in the backedge.
 938   if( n->in(0) && n->in(0) == back_ctrl ) {
 939     assert(clones.find(n->_idx) == NULL, "dead loop");
 940     x = n->clone();             // Clone a copy of 'n' to preheader
 941     clones.push(x, n->_idx);
 942     x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
 943   }
 944 
 945   // Recursive fixup any other input edges into x.
 946   // If there are no changes we can just return 'n', otherwise
 947   // we need to clone a private copy and change it.
 948   for( uint i = 1; i < n->req(); i++ ) {
 949     Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones );
 950     if( g != n->in(i) ) {
 951       if( !x ) {
 952         assert(clones.find(n->_idx) == NULL, "dead loop");
 953         x = n->clone();
 954         clones.push(x, n->_idx);
 955       }
 956       x->set_req(i, g);
 957     }
 958   }
 959   if( x ) {                     // x can legally float to pre-header location
 960     register_new_node( x, preheader_ctrl );
 961     return x;
 962   } else {                      // raise n to cover LCA of uses
 963     set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
 964   }
 965   return n;
 966 }
 967 
 968 bool PhaseIdealLoop::cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop) {
 969   Node* castii = new CastIINode(incr, TypeInt::INT, true);
 970   castii->set_req(0, ctrl);
 971   register_new_node(castii, ctrl);
 972   for (DUIterator_Fast imax, i = incr->fast_outs(imax); i < imax; i++) {
 973     Node* n = incr->fast_out(i);
 974     if (n->is_Phi() && n->in(0) == loop) {
 975       int nrep = n->replace_edge(incr, castii);
 976       return true;
 977     }
 978   }
 979   return false;
 980 }
 981 
 982 //------------------------------insert_pre_post_loops--------------------------
 983 // Insert pre and post loops.  If peel_only is set, the pre-loop can not have
 984 // more iterations added.  It acts as a 'peel' only, no lower-bound RCE, no
 985 // alignment.  Useful to unroll loops that do no array accesses.
 986 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
 987 
 988 #ifndef PRODUCT
 989   if (TraceLoopOpts) {
 990     if (peel_only)
 991       tty->print("PeelMainPost ");
 992     else
 993       tty->print("PreMainPost  ");
 994     loop->dump_head();
 995   }
 996 #endif
 997   C->set_major_progress();
 998 
 999   // Find common pieces of the loop being guarded with pre & post loops
1000   CountedLoopNode *main_head = loop->_head->as_CountedLoop();
1001   assert( main_head->is_normal_loop(), "" );
1002   CountedLoopEndNode *main_end = main_head->loopexit();
1003   guarantee(main_end != NULL, "no loop exit node");
1004   assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
1005   uint dd_main_head = dom_depth(main_head);
1006   uint max = main_head->outcnt();
1007 
1008   Node *pre_header= main_head->in(LoopNode::EntryControl);
1009   Node *init      = main_head->init_trip();
1010   Node *incr      = main_end ->incr();
1011   Node *limit     = main_end ->limit();
1012   Node *stride    = main_end ->stride();
1013   Node *cmp       = main_end ->cmp_node();
1014   BoolTest::mask b_test = main_end->test_trip();
1015 
1016   // Need only 1 user of 'bol' because I will be hacking the loop bounds.
1017   Node *bol = main_end->in(CountedLoopEndNode::TestValue);
1018   if( bol->outcnt() != 1 ) {
1019     bol = bol->clone();
1020     register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
1021     _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, bol);
1022   }
1023   // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
1024   if( cmp->outcnt() != 1 ) {
1025     cmp = cmp->clone();
1026     register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
1027     _igvn.replace_input_of(bol, 1, cmp);
1028   }
1029 
1030   //------------------------------
1031   // Step A: Create Post-Loop.
1032   Node* main_exit = main_end->proj_out(false);
1033   assert( main_exit->Opcode() == Op_IfFalse, "" );
1034   int dd_main_exit = dom_depth(main_exit);
1035 
1036   // Step A1: Clone the loop body.  The clone becomes the post-loop.  The main
1037   // loop pre-header illegally has 2 control users (old & new loops).
1038   clone_loop( loop, old_new, dd_main_exit );
1039   assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
1040   CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
1041   post_head->set_post_loop(main_head);
1042 
1043   // Reduce the post-loop trip count.
1044   CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
1045   post_end->_prob = PROB_FAIR;
1046 
1047   // Build the main-loop normal exit.
1048   IfFalseNode *new_main_exit = new IfFalseNode(main_end);
1049   _igvn.register_new_node_with_optimizer( new_main_exit );
1050   set_idom(new_main_exit, main_end, dd_main_exit );
1051   set_loop(new_main_exit, loop->_parent);
1052 
1053   // Step A2: Build a zero-trip guard for the post-loop.  After leaving the
1054   // main-loop, the post-loop may not execute at all.  We 'opaque' the incr
1055   // (the main-loop trip-counter exit value) because we will be changing
1056   // the exit value (via unrolling) so we cannot constant-fold away the zero
1057   // trip guard until all unrolling is done.
1058   Node *zer_opaq = new Opaque1Node(C, incr);
1059   Node *zer_cmp  = new CmpINode( zer_opaq, limit );
1060   Node *zer_bol  = new BoolNode( zer_cmp, b_test );
1061   register_new_node( zer_opaq, new_main_exit );
1062   register_new_node( zer_cmp , new_main_exit );
1063   register_new_node( zer_bol , new_main_exit );
1064 
1065   // Build the IfNode
1066   IfNode *zer_iff = new IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
1067   _igvn.register_new_node_with_optimizer( zer_iff );
1068   set_idom(zer_iff, new_main_exit, dd_main_exit);
1069   set_loop(zer_iff, loop->_parent);
1070 
1071   // Plug in the false-path, taken if we need to skip post-loop
1072   _igvn.replace_input_of(main_exit, 0, zer_iff);
1073   set_idom(main_exit, zer_iff, dd_main_exit);
1074   set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
1075   // Make the true-path, must enter the post loop
1076   Node *zer_taken = new IfTrueNode( zer_iff );
1077   _igvn.register_new_node_with_optimizer( zer_taken );
1078   set_idom(zer_taken, zer_iff, dd_main_exit);
1079   set_loop(zer_taken, loop->_parent);
1080   // Plug in the true path
1081   _igvn.hash_delete( post_head );
1082   post_head->set_req(LoopNode::EntryControl, zer_taken);
1083   set_idom(post_head, zer_taken, dd_main_exit);
1084 
1085   Arena *a = Thread::current()->resource_area();
1086   VectorSet visited(a);
1087   Node_Stack clones(a, main_head->back_control()->outcnt());
1088   // Step A3: Make the fall-in values to the post-loop come from the
1089   // fall-out values of the main-loop.
1090   for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
1091     Node* main_phi = main_head->fast_out(i);
1092     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
1093       Node *post_phi = old_new[main_phi->_idx];
1094       Node *fallmain  = clone_up_backedge_goo(main_head->back_control(),
1095                                               post_head->init_control(),
1096                                               main_phi->in(LoopNode::LoopBackControl),
1097                                               visited, clones);
1098       _igvn.hash_delete(post_phi);
1099       post_phi->set_req( LoopNode::EntryControl, fallmain );
1100     }
1101   }
1102 
1103   // Update local caches for next stanza
1104   main_exit = new_main_exit;
1105 
1106 
1107   //------------------------------
1108   // Step B: Create Pre-Loop.
1109 
1110   // Step B1: Clone the loop body.  The clone becomes the pre-loop.  The main
1111   // loop pre-header illegally has 2 control users (old & new loops).
1112   clone_loop( loop, old_new, dd_main_head );
1113   CountedLoopNode*    pre_head = old_new[main_head->_idx]->as_CountedLoop();
1114   CountedLoopEndNode* pre_end  = old_new[main_end ->_idx]->as_CountedLoopEnd();
1115   pre_head->set_pre_loop(main_head);
1116   Node *pre_incr = old_new[incr->_idx];
1117 
1118   // Reduce the pre-loop trip count.
1119   pre_end->_prob = PROB_FAIR;
1120 
1121   // Find the pre-loop normal exit.
1122   Node* pre_exit = pre_end->proj_out(false);
1123   assert( pre_exit->Opcode() == Op_IfFalse, "" );
1124   IfFalseNode *new_pre_exit = new IfFalseNode(pre_end);
1125   _igvn.register_new_node_with_optimizer( new_pre_exit );
1126   set_idom(new_pre_exit, pre_end, dd_main_head);
1127   set_loop(new_pre_exit, loop->_parent);
1128 
1129   // Step B2: Build a zero-trip guard for the main-loop.  After leaving the
1130   // pre-loop, the main-loop may not execute at all.  Later in life this
1131   // zero-trip guard will become the minimum-trip guard when we unroll
1132   // the main-loop.
1133   Node *min_opaq = new Opaque1Node(C, limit);
1134   Node *min_cmp  = new CmpINode( pre_incr, min_opaq );
1135   Node *min_bol  = new BoolNode( min_cmp, b_test );
1136   register_new_node( min_opaq, new_pre_exit );
1137   register_new_node( min_cmp , new_pre_exit );
1138   register_new_node( min_bol , new_pre_exit );
1139 
1140   // Build the IfNode (assume the main-loop is executed always).
1141   IfNode *min_iff = new IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
1142   _igvn.register_new_node_with_optimizer( min_iff );
1143   set_idom(min_iff, new_pre_exit, dd_main_head);
1144   set_loop(min_iff, loop->_parent);
1145 
1146   // Plug in the false-path, taken if we need to skip main-loop
1147   _igvn.hash_delete( pre_exit );
1148   pre_exit->set_req(0, min_iff);
1149   set_idom(pre_exit, min_iff, dd_main_head);
1150   set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
1151   // Make the true-path, must enter the main loop
1152   Node *min_taken = new IfTrueNode( min_iff );
1153   _igvn.register_new_node_with_optimizer( min_taken );
1154   set_idom(min_taken, min_iff, dd_main_head);
1155   set_loop(min_taken, loop->_parent);
1156   // Plug in the true path
1157   _igvn.hash_delete( main_head );
1158   main_head->set_req(LoopNode::EntryControl, min_taken);
1159   set_idom(main_head, min_taken, dd_main_head);
1160 
1161   visited.Clear();
1162   clones.clear();
1163   // Step B3: Make the fall-in values to the main-loop come from the
1164   // fall-out values of the pre-loop.
1165   for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
1166     Node* main_phi = main_head->fast_out(i2);
1167     if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
1168       Node *pre_phi = old_new[main_phi->_idx];
1169       Node *fallpre  = clone_up_backedge_goo(pre_head->back_control(),
1170                                              main_head->init_control(),
1171                                              pre_phi->in(LoopNode::LoopBackControl),
1172                                              visited, clones);
1173       _igvn.hash_delete(main_phi);
1174       main_phi->set_req( LoopNode::EntryControl, fallpre );
1175     }
1176   }
1177 
1178   // Nodes inside the loop may be control dependent on a predicate
1179   // that was moved before the preloop. If the back branch of the main
1180   // or post loops becomes dead, those nodes won't be dependent on the
1181   // test that guards that loop nest anymore which could lead to an
1182   // incorrect array access because it executes independently of the
1183   // test that was guarding the loop nest. We add a special CastII on
1184   // the if branch that enters the loop, between the input induction
1185   // variable value and the induction variable Phi to preserve correct
1186   // dependencies.
1187 
1188   // CastII for the post loop:
1189   bool inserted = cast_incr_before_loop(zer_opaq->in(1), zer_taken, post_head);
1190   assert(inserted, "no castII inserted");
1191 
1192   // CastII for the main loop:
1193   inserted = cast_incr_before_loop(pre_incr, min_taken, main_head);
1194   assert(inserted, "no castII inserted");
1195 
1196   // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1197   // RCE and alignment may change this later.
1198   Node *cmp_end = pre_end->cmp_node();
1199   assert( cmp_end->in(2) == limit, "" );
1200   Node *pre_limit = new AddINode( init, stride );
1201 
1202   // Save the original loop limit in this Opaque1 node for
1203   // use by range check elimination.
1204   Node *pre_opaq  = new Opaque1Node(C, pre_limit, limit);
1205 
1206   register_new_node( pre_limit, pre_head->in(0) );
1207   register_new_node( pre_opaq , pre_head->in(0) );
1208 
1209   // Since no other users of pre-loop compare, I can hack limit directly
1210   assert( cmp_end->outcnt() == 1, "no other users" );
1211   _igvn.hash_delete(cmp_end);
1212   cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
1213 
1214   // Special case for not-equal loop bounds:
1215   // Change pre loop test, main loop test, and the
1216   // main loop guard test to use lt or gt depending on stride
1217   // direction:
1218   // positive stride use <
1219   // negative stride use >
1220   //
1221   // not-equal test is kept for post loop to handle case
1222   // when init > limit when stride > 0 (and reverse).
1223 
1224   if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
1225 
1226     BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
1227     // Modify pre loop end condition
1228     Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1229     BoolNode* new_bol0 = new BoolNode(pre_bol->in(1), new_test);
1230     register_new_node( new_bol0, pre_head->in(0) );
1231     _igvn.replace_input_of(pre_end, CountedLoopEndNode::TestValue, new_bol0);
1232     // Modify main loop guard condition
1233     assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
1234     BoolNode* new_bol1 = new BoolNode(min_bol->in(1), new_test);
1235     register_new_node( new_bol1, new_pre_exit );
1236     _igvn.hash_delete(min_iff);
1237     min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
1238     // Modify main loop end condition
1239     BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1240     BoolNode* new_bol2 = new BoolNode(main_bol->in(1), new_test);
1241     register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
1242     _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, new_bol2);
1243   }
1244 
1245   // Flag main loop
1246   main_head->set_main_loop();
1247   if( peel_only ) main_head->set_main_no_pre_loop();
1248 
1249   // Subtract a trip count for the pre-loop.
1250   main_head->set_trip_count(main_head->trip_count() - 1);
1251 
1252   // It's difficult to be precise about the trip-counts
1253   // for the pre/post loops.  They are usually very short,
1254   // so guess that 4 trips is a reasonable value.
1255   post_head->set_profile_trip_cnt(4.0);
1256   pre_head->set_profile_trip_cnt(4.0);
1257 
1258   // Now force out all loop-invariant dominating tests.  The optimizer
1259   // finds some, but we _know_ they are all useless.
1260   peeled_dom_test_elim(loop,old_new);
1261   loop->record_for_igvn();
1262 }
1263 
1264 //------------------------------insert_vector_post_loop------------------------
1265 // Insert a copy of the atomic unrolled vectorized main loop as a post loop,
1266 // unroll_policy has already informed us that more unrolling is about to happen to
1267 // the main loop.  The resultant post loop will serve as a vectorized drain loop.
1268 void PhaseIdealLoop::insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new) {
1269   if (!loop->_head->is_CountedLoop()) return;
1270 
1271   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1272 
1273   // only process vectorized main loops
1274   if (!cl->is_vectorized_loop() || !cl->is_main_loop()) return;
1275 
1276   int slp_max_unroll_factor = cl->slp_max_unroll();
1277   int cur_unroll = cl->unrolled_count();
1278 
1279   if (slp_max_unroll_factor == 0) return;
1280 
1281   // only process atomic unroll vector loops (not super unrolled after vectorization)
1282   if (cur_unroll != slp_max_unroll_factor) return;
1283 
1284   // we only ever process this one time
1285   if (cl->has_atomic_post_loop()) return;
1286 
1287 #ifndef PRODUCT
1288   if (TraceLoopOpts) {
1289     tty->print("PostVector  ");
1290     loop->dump_head();
1291   }
1292 #endif
1293   C->set_major_progress();
1294 
1295   // Find common pieces of the loop being guarded with pre & post loops
1296   CountedLoopNode *main_head = loop->_head->as_CountedLoop();
1297   CountedLoopEndNode *main_end = main_head->loopexit();
1298   guarantee(main_end != NULL, "no loop exit node");
1299   // diagnostic to show loop end is not properly formed
1300   assert(main_end->outcnt() == 2, "1 true, 1 false path only");
1301   uint dd_main_head = dom_depth(main_head);
1302   uint max = main_head->outcnt();
1303 
1304   // mark this loop as processed
1305   main_head->mark_has_atomic_post_loop();
1306 
1307   Node *pre_header = main_head->in(LoopNode::EntryControl);
1308   Node *init = main_head->init_trip();
1309   Node *incr = main_end->incr();
1310   Node *limit = main_end->limit();
1311   Node *stride = main_end->stride();
1312   Node *cmp = main_end->cmp_node();
1313   BoolTest::mask b_test = main_end->test_trip();
1314 
1315   //------------------------------
1316   // Step A: Create a new post-Loop.
1317   Node* main_exit = main_end->proj_out(false);
1318   assert(main_exit->Opcode() == Op_IfFalse, "");
1319   int dd_main_exit = dom_depth(main_exit);
1320 
1321   // Step A1: Clone the loop body of main.  The clone becomes the vector post-loop.
1322   // The main loop pre-header illegally has 2 control users (old & new loops).
1323   clone_loop(loop, old_new, dd_main_exit);
1324   assert(old_new[main_end->_idx]->Opcode() == Op_CountedLoopEnd, "");
1325   CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
1326   post_head->set_normal_loop();
1327   post_head->set_post_loop(main_head);
1328 
1329   // Reduce the post-loop trip count.
1330   CountedLoopEndNode* post_end = old_new[main_end->_idx]->as_CountedLoopEnd();
1331   post_end->_prob = PROB_FAIR;
1332 
1333   // Build the main-loop normal exit.
1334   IfFalseNode *new_main_exit = new IfFalseNode(main_end);
1335   _igvn.register_new_node_with_optimizer(new_main_exit);
1336   set_idom(new_main_exit, main_end, dd_main_exit);
1337   set_loop(new_main_exit, loop->_parent);
1338 
1339   // Step A2: Build a zero-trip guard for the vector post-loop.  After leaving the
1340   // main-loop, the vector post-loop may not execute at all.  We 'opaque' the incr
1341   // (the vectorized main-loop trip-counter exit value) because we will be changing
1342   // the exit value (via additional unrolling) so we cannot constant-fold away the zero
1343   // trip guard until all unrolling is done.
1344   Node *zer_opaq = new Opaque1Node(C, incr);
1345   Node *zer_cmp = new CmpINode(zer_opaq, limit);
1346   Node *zer_bol = new BoolNode(zer_cmp, b_test);
1347   register_new_node(zer_opaq, new_main_exit);
1348   register_new_node(zer_cmp, new_main_exit);
1349   register_new_node(zer_bol, new_main_exit);
1350 
1351   // Build the IfNode
1352   IfNode *zer_iff = new IfNode(new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN);
1353   _igvn.register_new_node_with_optimizer(zer_iff);
1354   set_idom(zer_iff, new_main_exit, dd_main_exit);
1355   set_loop(zer_iff, loop->_parent);
1356 
1357   // Plug in the false-path, taken if we need to skip vector post-loop
1358   _igvn.replace_input_of(main_exit, 0, zer_iff);
1359   set_idom(main_exit, zer_iff, dd_main_exit);
1360   set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
1361   // Make the true-path, must enter the vector post loop
1362   Node *zer_taken = new IfTrueNode(zer_iff);
1363   _igvn.register_new_node_with_optimizer(zer_taken);
1364   set_idom(zer_taken, zer_iff, dd_main_exit);
1365   set_loop(zer_taken, loop->_parent);
1366   // Plug in the true path
1367   _igvn.hash_delete(post_head);
1368   post_head->set_req(LoopNode::EntryControl, zer_taken);
1369   set_idom(post_head, zer_taken, dd_main_exit);
1370 
1371   Arena *a = Thread::current()->resource_area();
1372   VectorSet visited(a);
1373   Node_Stack clones(a, main_head->back_control()->outcnt());
1374   // Step A3: Make the fall-in values to the vector post-loop come from the
1375   // fall-out values of the main-loop.
1376   for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
1377     Node* main_phi = main_head->fast_out(i);
1378     if (main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0) {
1379       Node *cur_phi = old_new[main_phi->_idx];
1380       Node *fallnew = clone_up_backedge_goo(main_head->back_control(),
1381                                             post_head->init_control(),
1382                                             main_phi->in(LoopNode::LoopBackControl),
1383                                             visited, clones);
1384       _igvn.hash_delete(cur_phi);
1385       cur_phi->set_req(LoopNode::EntryControl, fallnew);
1386     }
1387   }
1388 
1389   // CastII for the new post loop:
1390   bool inserted = cast_incr_before_loop(zer_opaq->in(1), zer_taken, post_head);
1391   assert(inserted, "no castII inserted");
1392 
1393   // It's difficult to be precise about the trip-counts
1394   // for post loops.  They are usually very short,
1395   // so guess that unit vector trips is a reasonable value.
1396   post_head->set_profile_trip_cnt((float)slp_max_unroll_factor);
1397 
1398   // Now force out all loop-invariant dominating tests.  The optimizer
1399   // finds some, but we _know_ they are all useless.
1400   peeled_dom_test_elim(loop, old_new);
1401   loop->record_for_igvn();
1402 }
1403 
1404 //------------------------------is_invariant-----------------------------
1405 // Return true if n is invariant
1406 bool IdealLoopTree::is_invariant(Node* n) const {
1407   Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
1408   if (n_c->is_top()) return false;
1409   return !is_member(_phase->get_loop(n_c));
1410 }
1411 
1412 
1413 //------------------------------do_unroll--------------------------------------
1414 // Unroll the loop body one step - make each trip do 2 iterations.
1415 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
1416   assert(LoopUnrollLimit, "");
1417   CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
1418   CountedLoopEndNode *loop_end = loop_head->loopexit();
1419   assert(loop_end, "");
1420 #ifndef PRODUCT
1421   if (PrintOpto && VerifyLoopOptimizations) {
1422     tty->print("Unrolling ");
1423     loop->dump_head();
1424   } else if (TraceLoopOpts) {
1425     if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
1426       tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
1427     } else {
1428       tty->print("Unroll %d     ", loop_head->unrolled_count()*2);
1429     }
1430     loop->dump_head();
1431   }
1432 
1433   if (C->do_vector_loop() && (PrintOpto && VerifyLoopOptimizations || TraceLoopOpts)) {
1434     Arena* arena = Thread::current()->resource_area();
1435     Node_Stack stack(arena, C->live_nodes() >> 2);
1436     Node_List rpo_list;
1437     VectorSet visited(arena);
1438     visited.set(loop_head->_idx);
1439     rpo( loop_head, stack, visited, rpo_list );
1440     dump(loop, rpo_list.size(), rpo_list );
1441   }
1442 #endif
1443 
1444   // Remember loop node count before unrolling to detect
1445   // if rounds of unroll,optimize are making progress
1446   loop_head->set_node_count_before_unroll(loop->_body.size());
1447 
1448   Node *ctrl  = loop_head->in(LoopNode::EntryControl);
1449   Node *limit = loop_head->limit();
1450   Node *init  = loop_head->init_trip();
1451   Node *stride = loop_head->stride();
1452 
1453   Node *opaq = NULL;
1454   if (adjust_min_trip) {       // If not maximally unrolling, need adjustment
1455     // Search for zero-trip guard.
1456 
1457     // Check the shape of the graph at the loop entry. If an inappropriate
1458     // graph shape is encountered, the compiler bails out loop unrolling;
1459     // compilation of the method will still succeed.
1460     if (!is_canonical_main_loop_entry(loop_head)) {
1461       return;
1462     }
1463     opaq = ctrl->in(0)->in(1)->in(1)->in(2);
1464     // Zero-trip test uses an 'opaque' node which is not shared.
1465     assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
1466   }
1467 
1468   C->set_major_progress();
1469 
1470   Node* new_limit = NULL;
1471   int stride_con = stride->get_int();
1472   int stride_p = (stride_con > 0) ? stride_con : -stride_con;
1473   uint old_trip_count = loop_head->trip_count();
1474   // Verify that unroll policy result is still valid.
1475   assert(old_trip_count > 1 &&
1476       (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity");
1477 
1478   // Adjust loop limit to keep valid iterations number after unroll.
1479   // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
1480   // which may overflow.
1481   if (!adjust_min_trip) {
1482     assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
1483         "odd trip count for maximally unroll");
1484     // Don't need to adjust limit for maximally unroll since trip count is even.
1485   } else if (loop_head->has_exact_trip_count() && init->is_Con()) {
1486     // Loop's limit is constant. Loop's init could be constant when pre-loop
1487     // become peeled iteration.
1488     jlong init_con = init->get_int();
1489     // We can keep old loop limit if iterations count stays the same:
1490     //   old_trip_count == new_trip_count * 2
1491     // Note: since old_trip_count >= 2 then new_trip_count >= 1
1492     // so we also don't need to adjust zero trip test.
1493     jlong limit_con  = limit->get_int();
1494     // (stride_con*2) not overflow since stride_con <= 8.
1495     int new_stride_con = stride_con * 2;
1496     int stride_m    = new_stride_con - (stride_con > 0 ? 1 : -1);
1497     jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con;
1498     // New trip count should satisfy next conditions.
1499     assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
1500     uint new_trip_count = (uint)trip_count;
1501     adjust_min_trip = (old_trip_count != new_trip_count*2);
1502   }
1503 
1504   if (adjust_min_trip) {
1505     // Step 2: Adjust the trip limit if it is called for.
1506     // The adjustment amount is -stride. Need to make sure if the
1507     // adjustment underflows or overflows, then the main loop is skipped.
1508     Node* cmp = loop_end->cmp_node();
1509     assert(cmp->in(2) == limit, "sanity");
1510     assert(opaq != NULL && opaq->in(1) == limit, "sanity");
1511 
1512     // Verify that policy_unroll result is still valid.
1513     const TypeInt* limit_type = _igvn.type(limit)->is_int();
1514     assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) ||
1515         stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity");
1516 
1517     if (limit->is_Con()) {
1518       // The check in policy_unroll and the assert above guarantee
1519       // no underflow if limit is constant.
1520       new_limit = _igvn.intcon(limit->get_int() - stride_con);
1521       set_ctrl(new_limit, C->root());
1522     } else {
1523       // Limit is not constant.
1524       if (loop_head->unrolled_count() == 1) { // only for first unroll
1525         // Separate limit by Opaque node in case it is an incremented
1526         // variable from previous loop to avoid using pre-incremented
1527         // value which could increase register pressure.
1528         // Otherwise reorg_offsets() optimization will create a separate
1529         // Opaque node for each use of trip-counter and as result
1530         // zero trip guard limit will be different from loop limit.
1531         assert(has_ctrl(opaq), "should have it");
1532         Node* opaq_ctrl = get_ctrl(opaq);
1533         limit = new Opaque2Node( C, limit );
1534         register_new_node( limit, opaq_ctrl );
1535       }
1536       if (stride_con > 0 && (java_subtract(limit_type->_lo, stride_con) < limit_type->_lo) ||
1537           stride_con < 0 && (java_subtract(limit_type->_hi, stride_con) > limit_type->_hi)) {
1538         // No underflow.
1539         new_limit = new SubINode(limit, stride);
1540       } else {
1541         // (limit - stride) may underflow.
1542         // Clamp the adjustment value with MININT or MAXINT:
1543         //
1544         //   new_limit = limit-stride
1545         //   if (stride > 0)
1546         //     new_limit = (limit < new_limit) ? MININT : new_limit;
1547         //   else
1548         //     new_limit = (limit > new_limit) ? MAXINT : new_limit;
1549         //
1550         BoolTest::mask bt = loop_end->test_trip();
1551         assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
1552         Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint);
1553         set_ctrl(adj_max, C->root());
1554         Node* old_limit = NULL;
1555         Node* adj_limit = NULL;
1556         Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL;
1557         if (loop_head->unrolled_count() > 1 &&
1558             limit->is_CMove() && limit->Opcode() == Op_CMoveI &&
1559             limit->in(CMoveNode::IfTrue) == adj_max &&
1560             bol->as_Bool()->_test._test == bt &&
1561             bol->in(1)->Opcode() == Op_CmpI &&
1562             bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) {
1563           // Loop was unrolled before.
1564           // Optimize the limit to avoid nested CMove:
1565           // use original limit as old limit.
1566           old_limit = bol->in(1)->in(1);
1567           // Adjust previous adjusted limit.
1568           adj_limit = limit->in(CMoveNode::IfFalse);
1569           adj_limit = new SubINode(adj_limit, stride);
1570         } else {
1571           old_limit = limit;
1572           adj_limit = new SubINode(limit, stride);
1573         }
1574         assert(old_limit != NULL && adj_limit != NULL, "");
1575         register_new_node( adj_limit, ctrl ); // adjust amount
1576         Node* adj_cmp = new CmpINode(old_limit, adj_limit);
1577         register_new_node( adj_cmp, ctrl );
1578         Node* adj_bool = new BoolNode(adj_cmp, bt);
1579         register_new_node( adj_bool, ctrl );
1580         new_limit = new CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT);
1581       }
1582       register_new_node(new_limit, ctrl);
1583     }
1584     assert(new_limit != NULL, "");
1585     // Replace in loop test.
1586     assert(loop_end->in(1)->in(1) == cmp, "sanity");
1587     if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
1588       // Don't need to create new test since only one user.
1589       _igvn.hash_delete(cmp);
1590       cmp->set_req(2, new_limit);
1591     } else {
1592       // Create new test since it is shared.
1593       Node* ctrl2 = loop_end->in(0);
1594       Node* cmp2  = cmp->clone();
1595       cmp2->set_req(2, new_limit);
1596       register_new_node(cmp2, ctrl2);
1597       Node* bol2 = loop_end->in(1)->clone();
1598       bol2->set_req(1, cmp2);
1599       register_new_node(bol2, ctrl2);
1600       _igvn.replace_input_of(loop_end, 1, bol2);
1601     }
1602     // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1603     // Make it a 1-trip test (means at least 2 trips).
1604 
1605     // Guard test uses an 'opaque' node which is not shared.  Hence I
1606     // can edit it's inputs directly.  Hammer in the new limit for the
1607     // minimum-trip guard.
1608     assert(opaq->outcnt() == 1, "");
1609     _igvn.replace_input_of(opaq, 1, new_limit);
1610   }
1611 
1612   // Adjust max trip count. The trip count is intentionally rounded
1613   // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1614   // the main, unrolled, part of the loop will never execute as it is protected
1615   // by the min-trip test.  See bug 4834191 for a case where we over-unrolled
1616   // and later determined that part of the unrolled loop was dead.
1617   loop_head->set_trip_count(old_trip_count / 2);
1618 
1619   // Double the count of original iterations in the unrolled loop body.
1620   loop_head->double_unrolled_count();
1621 
1622   // ---------
1623   // Step 4: Clone the loop body.  Move it inside the loop.  This loop body
1624   // represents the odd iterations; since the loop trips an even number of
1625   // times its backedge is never taken.  Kill the backedge.
1626   uint dd = dom_depth(loop_head);
1627   clone_loop( loop, old_new, dd );
1628 
1629   // Make backedges of the clone equal to backedges of the original.
1630   // Make the fall-in from the original come from the fall-out of the clone.
1631   for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1632     Node* phi = loop_head->fast_out(j);
1633     if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1634       Node *newphi = old_new[phi->_idx];
1635       _igvn.hash_delete( phi );
1636       _igvn.hash_delete( newphi );
1637 
1638       phi   ->set_req(LoopNode::   EntryControl, newphi->in(LoopNode::LoopBackControl));
1639       newphi->set_req(LoopNode::LoopBackControl, phi   ->in(LoopNode::LoopBackControl));
1640       phi   ->set_req(LoopNode::LoopBackControl, C->top());
1641     }
1642   }
1643   Node *clone_head = old_new[loop_head->_idx];
1644   _igvn.hash_delete( clone_head );
1645   loop_head ->set_req(LoopNode::   EntryControl, clone_head->in(LoopNode::LoopBackControl));
1646   clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1647   loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1648   loop->_head = clone_head;     // New loop header
1649 
1650   set_idom(loop_head,  loop_head ->in(LoopNode::EntryControl), dd);
1651   set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1652 
1653   // Kill the clone's backedge
1654   Node *newcle = old_new[loop_end->_idx];
1655   _igvn.hash_delete( newcle );
1656   Node *one = _igvn.intcon(1);
1657   set_ctrl(one, C->root());
1658   newcle->set_req(1, one);
1659   // Force clone into same loop body
1660   uint max = loop->_body.size();
1661   for( uint k = 0; k < max; k++ ) {
1662     Node *old = loop->_body.at(k);
1663     Node *nnn = old_new[old->_idx];
1664     loop->_body.push(nnn);
1665     if (!has_ctrl(old))
1666       set_loop(nnn, loop);
1667   }
1668 
1669   loop->record_for_igvn();
1670 
1671 #ifndef PRODUCT
1672   if (C->do_vector_loop() && (PrintOpto && VerifyLoopOptimizations || TraceLoopOpts)) {
1673     tty->print("\nnew loop after unroll\n");       loop->dump_head();
1674     for (uint i = 0; i < loop->_body.size(); i++) {
1675       loop->_body.at(i)->dump();
1676     }
1677     if(C->clone_map().is_debug()) {
1678       tty->print("\nCloneMap\n");
1679       Dict* dict = C->clone_map().dict();
1680       DictI i(dict);
1681       tty->print_cr("Dict@%p[%d] = ", dict, dict->Size());
1682       for (int ii = 0; i.test(); ++i, ++ii) {
1683         NodeCloneInfo cl((uint64_t)dict->operator[]((void*)i._key));
1684         tty->print("%d->%d:%d,", (int)(intptr_t)i._key, cl.idx(), cl.gen());
1685         if (ii % 10 == 9) {
1686           tty->print_cr(" ");
1687         }
1688       }
1689       tty->print_cr(" ");
1690     }
1691   }
1692 #endif
1693 
1694 }
1695 
1696 //------------------------------do_maximally_unroll----------------------------
1697 
1698 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1699   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1700   assert(cl->has_exact_trip_count(), "trip count is not exact");
1701   assert(cl->trip_count() > 0, "");
1702 #ifndef PRODUCT
1703   if (TraceLoopOpts) {
1704     tty->print("MaxUnroll  %d ", cl->trip_count());
1705     loop->dump_head();
1706   }
1707 #endif
1708 
1709   // If loop is tripping an odd number of times, peel odd iteration
1710   if ((cl->trip_count() & 1) == 1) {
1711     do_peeling(loop, old_new);
1712   }
1713 
1714   // Now its tripping an even number of times remaining.  Double loop body.
1715   // Do not adjust pre-guards; they are not needed and do not exist.
1716   if (cl->trip_count() > 0) {
1717     assert((cl->trip_count() & 1) == 0, "missed peeling");
1718     do_unroll(loop, old_new, false);
1719   }
1720 }
1721 
1722 void PhaseIdealLoop::mark_reductions(IdealLoopTree *loop) {
1723   if (SuperWordReductions == false) return;
1724 
1725   CountedLoopNode* loop_head = loop->_head->as_CountedLoop();
1726   if (loop_head->unrolled_count() > 1) {
1727     return;
1728   }
1729 
1730   Node* trip_phi = loop_head->phi();
1731   for (DUIterator_Fast imax, i = loop_head->fast_outs(imax); i < imax; i++) {
1732     Node* phi = loop_head->fast_out(i);
1733     if (phi->is_Phi() && phi->outcnt() > 0 && phi != trip_phi) {
1734       // For definitions which are loop inclusive and not tripcounts.
1735       Node* def_node = phi->in(LoopNode::LoopBackControl);
1736 
1737       if (def_node != NULL) {
1738         Node* n_ctrl = get_ctrl(def_node);
1739         if (n_ctrl != NULL && loop->is_member(get_loop(n_ctrl))) {
1740           // Now test it to see if it fits the standard pattern for a reduction operator.
1741           int opc = def_node->Opcode();
1742           if (opc != ReductionNode::opcode(opc, def_node->bottom_type()->basic_type())) {
1743             if (!def_node->is_reduction()) { // Not marked yet
1744               // To be a reduction, the arithmetic node must have the phi as input and provide a def to it
1745               bool ok = false;
1746               for (unsigned j = 1; j < def_node->req(); j++) {
1747                 Node* in = def_node->in(j);
1748                 if (in == phi) {
1749                   ok = true;
1750                   break;
1751                 }
1752               }
1753 
1754               // do nothing if we did not match the initial criteria
1755               if (ok == false) {
1756                 continue;
1757               }
1758 
1759               // The result of the reduction must not be used in the loop
1760               for (DUIterator_Fast imax, i = def_node->fast_outs(imax); i < imax && ok; i++) {
1761                 Node* u = def_node->fast_out(i);
1762                 if (has_ctrl(u) && !loop->is_member(get_loop(get_ctrl(u)))) {
1763                   continue;
1764                 }
1765                 if (u == phi) {
1766                   continue;
1767                 }
1768                 ok = false;
1769               }
1770 
1771               // iff the uses conform
1772               if (ok) {
1773                 def_node->add_flag(Node::Flag_is_reduction);
1774                 loop_head->mark_has_reductions();
1775               }
1776             }
1777           }
1778         }
1779       }
1780     }
1781   }
1782 }
1783 
1784 //------------------------------dominates_backedge---------------------------------
1785 // Returns true if ctrl is executed on every complete iteration
1786 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1787   assert(ctrl->is_CFG(), "must be control");
1788   Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1789   return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1790 }
1791 
1792 //------------------------------adjust_limit-----------------------------------
1793 // Helper function for add_constraint().
1794 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) {
1795   // Compute "I :: (limit-offset)/scale"
1796   Node *con = new SubINode(rc_limit, offset);
1797   register_new_node(con, pre_ctrl);
1798   Node *X = new DivINode(0, con, scale);
1799   register_new_node(X, pre_ctrl);
1800 
1801   // Adjust loop limit
1802   loop_limit = (stride_con > 0)
1803                ? (Node*)(new MinINode(loop_limit, X))
1804                : (Node*)(new MaxINode(loop_limit, X));
1805   register_new_node(loop_limit, pre_ctrl);
1806   return loop_limit;
1807 }
1808 
1809 //------------------------------add_constraint---------------------------------
1810 // Constrain the main loop iterations so the conditions:
1811 //    low_limit <= scale_con * I + offset  <  upper_limit
1812 // always holds true.  That is, either increase the number of iterations in
1813 // the pre-loop or the post-loop until the condition holds true in the main
1814 // loop.  Stride, scale, offset and limit are all loop invariant.  Further,
1815 // stride and scale are constants (offset and limit often are).
1816 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 ) {
1817   // For positive stride, the pre-loop limit always uses a MAX function
1818   // and the main loop a MIN function.  For negative stride these are
1819   // reversed.
1820 
1821   // Also for positive stride*scale the affine function is increasing, so the
1822   // pre-loop must check for underflow and the post-loop for overflow.
1823   // Negative stride*scale reverses this; pre-loop checks for overflow and
1824   // post-loop for underflow.
1825 
1826   Node *scale = _igvn.intcon(scale_con);
1827   set_ctrl(scale, C->root());
1828 
1829   if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
1830     // The overflow limit: scale*I+offset < upper_limit
1831     // For main-loop compute
1832     //   ( if (scale > 0) /* and stride > 0 */
1833     //       I < (upper_limit-offset)/scale
1834     //     else /* scale < 0 and stride < 0 */
1835     //       I > (upper_limit-offset)/scale
1836     //   )
1837     //
1838     // (upper_limit-offset) may overflow or underflow.
1839     // But it is fine since main loop will either have
1840     // less iterations or will be skipped in such case.
1841     *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl);
1842 
1843     // The underflow limit: low_limit <= scale*I+offset.
1844     // For pre-loop compute
1845     //   NOT(scale*I+offset >= low_limit)
1846     //   scale*I+offset < low_limit
1847     //   ( if (scale > 0) /* and stride > 0 */
1848     //       I < (low_limit-offset)/scale
1849     //     else /* scale < 0 and stride < 0 */
1850     //       I > (low_limit-offset)/scale
1851     //   )
1852 
1853     if (low_limit->get_int() == -max_jint) {
1854       // We need this guard when scale*pre_limit+offset >= limit
1855       // due to underflow. So we need execute pre-loop until
1856       // scale*I+offset >= min_int. But (min_int-offset) will
1857       // underflow when offset > 0 and X will be > original_limit
1858       // when stride > 0. To avoid it we replace positive offset with 0.
1859       //
1860       // Also (min_int+1 == -max_int) is used instead of min_int here
1861       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1862       Node* shift = _igvn.intcon(31);
1863       set_ctrl(shift, C->root());
1864       Node* sign = new RShiftINode(offset, shift);
1865       register_new_node(sign, pre_ctrl);
1866       offset = new AndINode(offset, sign);
1867       register_new_node(offset, pre_ctrl);
1868     } else {
1869       assert(low_limit->get_int() == 0, "wrong low limit for range check");
1870       // The only problem we have here when offset == min_int
1871       // since (0-min_int) == min_int. It may be fine for stride > 0
1872       // but for stride < 0 X will be < original_limit. To avoid it
1873       // max(pre_limit, original_limit) is used in do_range_check().
1874     }
1875     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1876     *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl);
1877 
1878   } else { // stride_con*scale_con < 0
1879     // For negative stride*scale pre-loop checks for overflow and
1880     // post-loop for underflow.
1881     //
1882     // The overflow limit: scale*I+offset < upper_limit
1883     // For pre-loop compute
1884     //   NOT(scale*I+offset < upper_limit)
1885     //   scale*I+offset >= upper_limit
1886     //   scale*I+offset+1 > upper_limit
1887     //   ( if (scale < 0) /* and stride > 0 */
1888     //       I < (upper_limit-(offset+1))/scale
1889     //     else /* scale > 0 and stride < 0 */
1890     //       I > (upper_limit-(offset+1))/scale
1891     //   )
1892     //
1893     // (upper_limit-offset-1) may underflow or overflow.
1894     // To avoid it min(pre_limit, original_limit) is used
1895     // in do_range_check() for stride > 0 and max() for < 0.
1896     Node *one  = _igvn.intcon(1);
1897     set_ctrl(one, C->root());
1898 
1899     Node *plus_one = new AddINode(offset, one);
1900     register_new_node( plus_one, pre_ctrl );
1901     // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1902     *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl);
1903 
1904     if (low_limit->get_int() == -max_jint) {
1905       // We need this guard when scale*main_limit+offset >= limit
1906       // due to underflow. So we need execute main-loop while
1907       // scale*I+offset+1 > min_int. But (min_int-offset-1) will
1908       // underflow when (offset+1) > 0 and X will be < main_limit
1909       // when scale < 0 (and stride > 0). To avoid it we replace
1910       // positive (offset+1) with 0.
1911       //
1912       // Also (min_int+1 == -max_int) is used instead of min_int here
1913       // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1914       Node* shift = _igvn.intcon(31);
1915       set_ctrl(shift, C->root());
1916       Node* sign = new RShiftINode(plus_one, shift);
1917       register_new_node(sign, pre_ctrl);
1918       plus_one = new AndINode(plus_one, sign);
1919       register_new_node(plus_one, pre_ctrl);
1920     } else {
1921       assert(low_limit->get_int() == 0, "wrong low limit for range check");
1922       // The only problem we have here when offset == max_int
1923       // since (max_int+1) == min_int and (0-min_int) == min_int.
1924       // But it is fine since main loop will either have
1925       // less iterations or will be skipped in such case.
1926     }
1927     // The underflow limit: low_limit <= scale*I+offset.
1928     // For main-loop compute
1929     //   scale*I+offset+1 > low_limit
1930     //   ( if (scale < 0) /* and stride > 0 */
1931     //       I < (low_limit-(offset+1))/scale
1932     //     else /* scale > 0 and stride < 0 */
1933     //       I > (low_limit-(offset+1))/scale
1934     //   )
1935 
1936     *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl);
1937   }
1938 }
1939 
1940 
1941 //------------------------------is_scaled_iv---------------------------------
1942 // Return true if exp is a constant times an induction var
1943 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1944   if (exp == iv) {
1945     if (p_scale != NULL) {
1946       *p_scale = 1;
1947     }
1948     return true;
1949   }
1950   int opc = exp->Opcode();
1951   if (opc == Op_MulI) {
1952     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1953       if (p_scale != NULL) {
1954         *p_scale = exp->in(2)->get_int();
1955       }
1956       return true;
1957     }
1958     if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1959       if (p_scale != NULL) {
1960         *p_scale = exp->in(1)->get_int();
1961       }
1962       return true;
1963     }
1964   } else if (opc == Op_LShiftI) {
1965     if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1966       if (p_scale != NULL) {
1967         *p_scale = 1 << exp->in(2)->get_int();
1968       }
1969       return true;
1970     }
1971   }
1972   return false;
1973 }
1974 
1975 //-----------------------------is_scaled_iv_plus_offset------------------------------
1976 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1977 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1978   if (is_scaled_iv(exp, iv, p_scale)) {
1979     if (p_offset != NULL) {
1980       Node *zero = _igvn.intcon(0);
1981       set_ctrl(zero, C->root());
1982       *p_offset = zero;
1983     }
1984     return true;
1985   }
1986   int opc = exp->Opcode();
1987   if (opc == Op_AddI) {
1988     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1989       if (p_offset != NULL) {
1990         *p_offset = exp->in(2);
1991       }
1992       return true;
1993     }
1994     if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1995       if (p_offset != NULL) {
1996         *p_offset = exp->in(1);
1997       }
1998       return true;
1999     }
2000     if (exp->in(2)->is_Con()) {
2001       Node* offset2 = NULL;
2002       if (depth < 2 &&
2003           is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
2004                                    p_offset != NULL ? &offset2 : NULL, depth+1)) {
2005         if (p_offset != NULL) {
2006           Node *ctrl_off2 = get_ctrl(offset2);
2007           Node* offset = new AddINode(offset2, exp->in(2));
2008           register_new_node(offset, ctrl_off2);
2009           *p_offset = offset;
2010         }
2011         return true;
2012       }
2013     }
2014   } else if (opc == Op_SubI) {
2015     if (is_scaled_iv(exp->in(1), iv, p_scale)) {
2016       if (p_offset != NULL) {
2017         Node *zero = _igvn.intcon(0);
2018         set_ctrl(zero, C->root());
2019         Node *ctrl_off = get_ctrl(exp->in(2));
2020         Node* offset = new SubINode(zero, exp->in(2));
2021         register_new_node(offset, ctrl_off);
2022         *p_offset = offset;
2023       }
2024       return true;
2025     }
2026     if (is_scaled_iv(exp->in(2), iv, p_scale)) {
2027       if (p_offset != NULL) {
2028         *p_scale *= -1;
2029         *p_offset = exp->in(1);
2030       }
2031       return true;
2032     }
2033   }
2034   return false;
2035 }
2036 
2037 //------------------------------do_range_check---------------------------------
2038 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
2039 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
2040 #ifndef PRODUCT
2041   if (PrintOpto && VerifyLoopOptimizations) {
2042     tty->print("Range Check Elimination ");
2043     loop->dump_head();
2044   } else if (TraceLoopOpts) {
2045     tty->print("RangeCheck   ");
2046     loop->dump_head();
2047   }
2048 #endif
2049   assert(RangeCheckElimination, "");
2050   CountedLoopNode *cl = loop->_head->as_CountedLoop();
2051 
2052   // protect against stride not being a constant
2053   if (!cl->stride_is_con())
2054     return;
2055 
2056   // Find the trip counter; we are iteration splitting based on it
2057   Node *trip_counter = cl->phi();
2058   // Find the main loop limit; we will trim it's iterations
2059   // to not ever trip end tests
2060   Node *main_limit = cl->limit();
2061 
2062   // Check graph shape. Cannot optimize a loop if zero-trip
2063   // Opaque1 node is optimized away and then another round
2064   // of loop opts attempted.
2065   if (!is_canonical_main_loop_entry(cl)) {
2066     return;
2067   }
2068 
2069   // Need to find the main-loop zero-trip guard
2070   Node *ctrl  = cl->in(LoopNode::EntryControl);
2071   Node *iffm = ctrl->in(0);
2072   Node *opqzm = iffm->in(1)->in(1)->in(2);
2073   assert(opqzm->in(1) == main_limit, "do not understand situation");
2074 
2075   // Find the pre-loop limit; we will expand its iterations to
2076   // not ever trip low tests.
2077   Node *p_f = iffm->in(0);
2078   // pre loop may have been optimized out
2079   if (p_f->Opcode() != Op_IfFalse) {
2080     return;
2081   }
2082   CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
2083   assert(pre_end->loopnode()->is_pre_loop(), "");
2084   Node *pre_opaq1 = pre_end->limit();
2085   // Occasionally it's possible for a pre-loop Opaque1 node to be
2086   // optimized away and then another round of loop opts attempted.
2087   // We can not optimize this particular loop in that case.
2088   if (pre_opaq1->Opcode() != Op_Opaque1)
2089     return;
2090   Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
2091   Node *pre_limit = pre_opaq->in(1);
2092 
2093   // Where do we put new limit calculations
2094   Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
2095 
2096   // Ensure the original loop limit is available from the
2097   // pre-loop Opaque1 node.
2098   Node *orig_limit = pre_opaq->original_loop_limit();
2099   if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
2100     return;
2101 
2102   // Must know if its a count-up or count-down loop
2103 
2104   int stride_con = cl->stride_con();
2105   Node *zero = _igvn.intcon(0);
2106   Node *one  = _igvn.intcon(1);
2107   // Use symmetrical int range [-max_jint,max_jint]
2108   Node *mini = _igvn.intcon(-max_jint);
2109   set_ctrl(zero, C->root());
2110   set_ctrl(one,  C->root());
2111   set_ctrl(mini, C->root());
2112 
2113   // Range checks that do not dominate the loop backedge (ie.
2114   // conditionally executed) can lengthen the pre loop limit beyond
2115   // the original loop limit. To prevent this, the pre limit is
2116   // (for stride > 0) MINed with the original loop limit (MAXed
2117   // stride < 0) when some range_check (rc) is conditionally
2118   // executed.
2119   bool conditional_rc = false;
2120 
2121   // Check loop body for tests of trip-counter plus loop-invariant vs
2122   // loop-invariant.
2123   for( uint i = 0; i < loop->_body.size(); i++ ) {
2124     Node *iff = loop->_body[i];
2125     if (iff->Opcode() == Op_If ||
2126         iff->Opcode() == Op_RangeCheck) { // Test?
2127       // Test is an IfNode, has 2 projections.  If BOTH are in the loop
2128       // we need loop unswitching instead of iteration splitting.
2129       Node *exit = loop->is_loop_exit(iff);
2130       if( !exit ) continue;
2131       int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
2132 
2133       // Get boolean condition to test
2134       Node *i1 = iff->in(1);
2135       if( !i1->is_Bool() ) continue;
2136       BoolNode *bol = i1->as_Bool();
2137       BoolTest b_test = bol->_test;
2138       // Flip sense of test if exit condition is flipped
2139       if( flip )
2140         b_test = b_test.negate();
2141 
2142       // Get compare
2143       Node *cmp = bol->in(1);
2144 
2145       // Look for trip_counter + offset vs limit
2146       Node *rc_exp = cmp->in(1);
2147       Node *limit  = cmp->in(2);
2148       jint scale_con= 1;        // Assume trip counter not scaled
2149 
2150       Node *limit_c = get_ctrl(limit);
2151       if( loop->is_member(get_loop(limit_c) ) ) {
2152         // Compare might have operands swapped; commute them
2153         b_test = b_test.commute();
2154         rc_exp = cmp->in(2);
2155         limit  = cmp->in(1);
2156         limit_c = get_ctrl(limit);
2157         if( loop->is_member(get_loop(limit_c) ) )
2158           continue;             // Both inputs are loop varying; cannot RCE
2159       }
2160       // Here we know 'limit' is loop invariant
2161 
2162       // 'limit' maybe pinned below the zero trip test (probably from a
2163       // previous round of rce), in which case, it can't be used in the
2164       // zero trip test expression which must occur before the zero test's if.
2165       if( limit_c == ctrl ) {
2166         continue;  // Don't rce this check but continue looking for other candidates.
2167       }
2168 
2169       // Check for scaled induction variable plus an offset
2170       Node *offset = NULL;
2171 
2172       if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
2173         continue;
2174       }
2175 
2176       Node *offset_c = get_ctrl(offset);
2177       if( loop->is_member( get_loop(offset_c) ) )
2178         continue;               // Offset is not really loop invariant
2179       // Here we know 'offset' is loop invariant.
2180 
2181       // As above for the 'limit', the 'offset' maybe pinned below the
2182       // zero trip test.
2183       if( offset_c == ctrl ) {
2184         continue; // Don't rce this check but continue looking for other candidates.
2185       }
2186 #ifdef ASSERT
2187       if (TraceRangeLimitCheck) {
2188         tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
2189         bol->dump(2);
2190       }
2191 #endif
2192       // At this point we have the expression as:
2193       //   scale_con * trip_counter + offset :: limit
2194       // where scale_con, offset and limit are loop invariant.  Trip_counter
2195       // monotonically increases by stride_con, a constant.  Both (or either)
2196       // stride_con and scale_con can be negative which will flip about the
2197       // sense of the test.
2198 
2199       // Adjust pre and main loop limits to guard the correct iteration set
2200       if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
2201         if( b_test._test == BoolTest::lt ) { // Range checks always use lt
2202           // The underflow and overflow limits: 0 <= scale*I+offset < limit
2203           add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit );
2204           if (!conditional_rc) {
2205             // (0-offset)/scale could be outside of loop iterations range.
2206             conditional_rc = !loop->dominates_backedge(iff);
2207           }
2208         } else {
2209           if (PrintOpto) {
2210             tty->print_cr("missed RCE opportunity");
2211           }
2212           continue;             // In release mode, ignore it
2213         }
2214       } else {                  // Otherwise work on normal compares
2215         switch( b_test._test ) {
2216         case BoolTest::gt:
2217           // Fall into GE case
2218         case BoolTest::ge:
2219           // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
2220           scale_con = -scale_con;
2221           offset = new SubINode( zero, offset );
2222           register_new_node( offset, pre_ctrl );
2223           limit  = new SubINode( zero, limit  );
2224           register_new_node( limit, pre_ctrl );
2225           // Fall into LE case
2226         case BoolTest::le:
2227           if (b_test._test != BoolTest::gt) {
2228             // Convert X <= Y to X < Y+1
2229             limit = new AddINode( limit, one );
2230             register_new_node( limit, pre_ctrl );
2231           }
2232           // Fall into LT case
2233         case BoolTest::lt:
2234           // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
2235           // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
2236           // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
2237           add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit );
2238           if (!conditional_rc) {
2239             // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range.
2240             // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could
2241             // still be outside of loop range.
2242             conditional_rc = !loop->dominates_backedge(iff);
2243           }
2244           break;
2245         default:
2246           if (PrintOpto) {
2247             tty->print_cr("missed RCE opportunity");
2248           }
2249           continue;             // Unhandled case
2250         }
2251       }
2252 
2253       // Kill the eliminated test
2254       C->set_major_progress();
2255       Node *kill_con = _igvn.intcon( 1-flip );
2256       set_ctrl(kill_con, C->root());
2257       _igvn.replace_input_of(iff, 1, kill_con);
2258       // Find surviving projection
2259       assert(iff->is_If(), "");
2260       ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
2261       // Find loads off the surviving projection; remove their control edge
2262       for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
2263         Node* cd = dp->fast_out(i); // Control-dependent node
2264         if (cd->is_Load() && cd->depends_only_on_test()) {   // Loads can now float around in the loop
2265           // Allow the load to float around in the loop, or before it
2266           // but NOT before the pre-loop.
2267           _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL
2268           --i;
2269           --imax;
2270         }
2271       }
2272 
2273     } // End of is IF
2274 
2275   }
2276 
2277   // Update loop limits
2278   if (conditional_rc) {
2279     pre_limit = (stride_con > 0) ? (Node*)new MinINode(pre_limit, orig_limit)
2280                                  : (Node*)new MaxINode(pre_limit, orig_limit);
2281     register_new_node(pre_limit, pre_ctrl);
2282   }
2283   _igvn.replace_input_of(pre_opaq, 1, pre_limit);
2284 
2285   // Note:: we are making the main loop limit no longer precise;
2286   // need to round up based on stride.
2287   cl->set_nonexact_trip_count();
2288   Node *main_cle = cl->loopexit();
2289   Node *main_bol = main_cle->in(1);
2290   // Hacking loop bounds; need private copies of exit test
2291   if( main_bol->outcnt() > 1 ) {// BoolNode shared?
2292     main_bol = main_bol->clone();// Clone a private BoolNode
2293     register_new_node( main_bol, main_cle->in(0) );
2294     _igvn.replace_input_of(main_cle, 1, main_bol);
2295   }
2296   Node *main_cmp = main_bol->in(1);
2297   if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
2298     main_cmp = main_cmp->clone();// Clone a private CmpNode
2299     register_new_node( main_cmp, main_cle->in(0) );
2300     _igvn.replace_input_of(main_bol, 1, main_cmp);
2301   }
2302   // Hack the now-private loop bounds
2303   _igvn.replace_input_of(main_cmp, 2, main_limit);
2304   // The OpaqueNode is unshared by design
2305   assert( opqzm->outcnt() == 1, "cannot hack shared node" );
2306   _igvn.replace_input_of(opqzm, 1, main_limit);
2307 }
2308 
2309 //------------------------------DCE_loop_body----------------------------------
2310 // Remove simplistic dead code from loop body
2311 void IdealLoopTree::DCE_loop_body() {
2312   for( uint i = 0; i < _body.size(); i++ )
2313     if( _body.at(i)->outcnt() == 0 )
2314       _body.map( i--, _body.pop() );
2315 }
2316 
2317 
2318 //------------------------------adjust_loop_exit_prob--------------------------
2319 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
2320 // Replace with a 1-in-10 exit guess.
2321 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
2322   Node *test = tail();
2323   while( test != _head ) {
2324     uint top = test->Opcode();
2325     if( top == Op_IfTrue || top == Op_IfFalse ) {
2326       int test_con = ((ProjNode*)test)->_con;
2327       assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
2328       IfNode *iff = test->in(0)->as_If();
2329       if( iff->outcnt() == 2 ) {        // Ignore dead tests
2330         Node *bol = iff->in(1);
2331         if( bol && bol->req() > 1 && bol->in(1) &&
2332             ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
2333              (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
2334              (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
2335              (bol->in(1)->Opcode() == Op_CompareAndExchangeI ) ||
2336              (bol->in(1)->Opcode() == Op_CompareAndExchangeL ) ||
2337              (bol->in(1)->Opcode() == Op_CompareAndExchangeP ) ||
2338              (bol->in(1)->Opcode() == Op_CompareAndExchangeN ) ||
2339              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapI ) ||
2340              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapL ) ||
2341              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapP ) ||
2342              (bol->in(1)->Opcode() == Op_WeakCompareAndSwapN ) ||
2343              (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
2344              (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
2345              (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
2346              (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
2347           return;               // Allocation loops RARELY take backedge
2348         // Find the OTHER exit path from the IF
2349         Node* ex = iff->proj_out(1-test_con);
2350         float p = iff->_prob;
2351         if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
2352           if( top == Op_IfTrue ) {
2353             if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
2354               iff->_prob = PROB_STATIC_FREQUENT;
2355             }
2356           } else {
2357             if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
2358               iff->_prob = PROB_STATIC_INFREQUENT;
2359             }
2360           }
2361         }
2362       }
2363     }
2364     test = phase->idom(test);
2365   }
2366 }
2367 
2368 #ifdef ASSERT
2369 static CountedLoopNode* locate_pre_from_main(CountedLoopNode *cl) {
2370   Node *ctrl  = cl->in(LoopNode::EntryControl);
2371   assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
2372   Node *iffm = ctrl->in(0);
2373   assert(iffm->Opcode() == Op_If, "");
2374   Node *p_f = iffm->in(0);
2375   assert(p_f->Opcode() == Op_IfFalse, "");
2376   CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
2377   assert(pre_end->loopnode()->is_pre_loop(), "");
2378   return pre_end->loopnode();
2379 }
2380 #endif
2381 
2382 // Remove the main and post loops and make the pre loop execute all
2383 // iterations. Useful when the pre loop is found empty.
2384 void IdealLoopTree::remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase) {
2385   CountedLoopEndNode* pre_end = cl->loopexit();
2386   Node* pre_cmp = pre_end->cmp_node();
2387   if (pre_cmp->in(2)->Opcode() != Op_Opaque1) {
2388     // Only safe to remove the main loop if the compiler optimized it
2389     // out based on an unknown number of iterations
2390     return;
2391   }
2392 
2393   // Can we find the main loop?
2394   if (_next == NULL) {
2395     return;
2396   }
2397 
2398   Node* next_head = _next->_head;
2399   if (!next_head->is_CountedLoop()) {
2400     return;
2401   }
2402 
2403   CountedLoopNode* main_head = next_head->as_CountedLoop();
2404   if (!main_head->is_main_loop()) {
2405     return;
2406   }
2407 
2408   assert(locate_pre_from_main(main_head) == cl, "bad main loop");
2409   Node* main_iff = main_head->in(LoopNode::EntryControl)->in(0);
2410 
2411   // Remove the Opaque1Node of the pre loop and make it execute all iterations
2412   phase->_igvn.replace_input_of(pre_cmp, 2, pre_cmp->in(2)->in(2));
2413   // Remove the Opaque1Node of the main loop so it can be optimized out
2414   Node* main_cmp = main_iff->in(1)->in(1);
2415   assert(main_cmp->in(2)->Opcode() == Op_Opaque1, "main loop has no opaque node?");
2416   phase->_igvn.replace_input_of(main_cmp, 2, main_cmp->in(2)->in(1));
2417 }
2418 
2419 //------------------------------policy_do_remove_empty_loop--------------------
2420 // Micro-benchmark spamming.  Policy is to always remove empty loops.
2421 // The 'DO' part is to replace the trip counter with the value it will
2422 // have on the last iteration.  This will break the loop.
2423 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
2424   // Minimum size must be empty loop
2425   if (_body.size() > EMPTY_LOOP_SIZE)
2426     return false;
2427 
2428   if (!_head->is_CountedLoop())
2429     return false;     // Dead loop
2430   CountedLoopNode *cl = _head->as_CountedLoop();
2431   if (!cl->is_valid_counted_loop())
2432     return false; // Malformed loop
2433   if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
2434     return false;             // Infinite loop
2435 
2436   if (cl->is_pre_loop()) {
2437     // If the loop we are removing is a pre-loop then the main and
2438     // post loop can be removed as well
2439     remove_main_post_loops(cl, phase);
2440   }
2441 
2442 #ifdef ASSERT
2443   // Ensure only one phi which is the iv.
2444   Node* iv = NULL;
2445   for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
2446     Node* n = cl->fast_out(i);
2447     if (n->Opcode() == Op_Phi) {
2448       assert(iv == NULL, "Too many phis" );
2449       iv = n;
2450     }
2451   }
2452   assert(iv == cl->phi(), "Wrong phi" );
2453 #endif
2454 
2455   // main and post loops have explicitly created zero trip guard
2456   bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
2457   if (needs_guard) {
2458     // Skip guard if values not overlap.
2459     const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
2460     const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
2461     int  stride_con = cl->stride_con();
2462     if (stride_con > 0) {
2463       needs_guard = (init_t->_hi >= limit_t->_lo);
2464     } else {
2465       needs_guard = (init_t->_lo <= limit_t->_hi);
2466     }
2467   }
2468   if (needs_guard) {
2469     // Check for an obvious zero trip guard.
2470     Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl));
2471     if (inctrl->Opcode() == Op_IfTrue || inctrl->Opcode() == Op_IfFalse) {
2472       bool maybe_swapped = (inctrl->Opcode() == Op_IfFalse);
2473       // The test should look like just the backedge of a CountedLoop
2474       Node* iff = inctrl->in(0);
2475       if (iff->is_If()) {
2476         Node* bol = iff->in(1);
2477         if (bol->is_Bool()) {
2478           BoolTest test = bol->as_Bool()->_test;
2479           if (maybe_swapped) {
2480             test._test = test.commute();
2481             test._test = test.negate();
2482           }
2483           if (test._test == cl->loopexit()->test_trip()) {
2484             Node* cmp = bol->in(1);
2485             int init_idx = maybe_swapped ? 2 : 1;
2486             int limit_idx = maybe_swapped ? 1 : 2;
2487             if (cmp->is_Cmp() && cmp->in(init_idx) == cl->init_trip() && cmp->in(limit_idx) == cl->limit()) {
2488               needs_guard = false;
2489             }
2490           }
2491         }
2492       }
2493     }
2494   }
2495 
2496 #ifndef PRODUCT
2497   if (PrintOpto) {
2498     tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
2499     this->dump_head();
2500   } else if (TraceLoopOpts) {
2501     tty->print("Empty with%s zero trip guard   ", needs_guard ? "out" : "");
2502     this->dump_head();
2503   }
2504 #endif
2505 
2506   if (needs_guard) {
2507     // Peel the loop to ensure there's a zero trip guard
2508     Node_List old_new;
2509     phase->do_peeling(this, old_new);
2510   }
2511 
2512   // Replace the phi at loop head with the final value of the last
2513   // iteration.  Then the CountedLoopEnd will collapse (backedge never
2514   // taken) and all loop-invariant uses of the exit values will be correct.
2515   Node *phi = cl->phi();
2516   Node *exact_limit = phase->exact_limit(this);
2517   if (exact_limit != cl->limit()) {
2518     // We also need to replace the original limit to collapse loop exit.
2519     Node* cmp = cl->loopexit()->cmp_node();
2520     assert(cl->limit() == cmp->in(2), "sanity");
2521     phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
2522     phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist
2523   }
2524   // Note: the final value after increment should not overflow since
2525   // counted loop has limit check predicate.
2526   Node *final = new SubINode( exact_limit, cl->stride() );
2527   phase->register_new_node(final,cl->in(LoopNode::EntryControl));
2528   phase->_igvn.replace_node(phi,final);
2529   phase->C->set_major_progress();
2530   return true;
2531 }
2532 
2533 //------------------------------policy_do_one_iteration_loop-------------------
2534 // Convert one iteration loop into normal code.
2535 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) {
2536   if (!_head->as_Loop()->is_valid_counted_loop())
2537     return false; // Only for counted loop
2538 
2539   CountedLoopNode *cl = _head->as_CountedLoop();
2540   if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
2541     return false;
2542   }
2543 
2544 #ifndef PRODUCT
2545   if(TraceLoopOpts) {
2546     tty->print("OneIteration ");
2547     this->dump_head();
2548   }
2549 #endif
2550 
2551   Node *init_n = cl->init_trip();
2552 #ifdef ASSERT
2553   // Loop boundaries should be constant since trip count is exact.
2554   assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration");
2555 #endif
2556   // Replace the phi at loop head with the value of the init_trip.
2557   // Then the CountedLoopEnd will collapse (backedge will not be taken)
2558   // and all loop-invariant uses of the exit values will be correct.
2559   phase->_igvn.replace_node(cl->phi(), cl->init_trip());
2560   phase->C->set_major_progress();
2561   return true;
2562 }
2563 
2564 //=============================================================================
2565 //------------------------------iteration_split_impl---------------------------
2566 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
2567   // Compute exact loop trip count if possible.
2568   compute_exact_trip_count(phase);
2569 
2570   // Convert one iteration loop into normal code.
2571   if (policy_do_one_iteration_loop(phase))
2572     return true;
2573 
2574   // Check and remove empty loops (spam micro-benchmarks)
2575   if (policy_do_remove_empty_loop(phase))
2576     return true;  // Here we removed an empty loop
2577 
2578   bool should_peel = policy_peeling(phase); // Should we peel?
2579 
2580   bool should_unswitch = policy_unswitching(phase);
2581 
2582   // Non-counted loops may be peeled; exactly 1 iteration is peeled.
2583   // This removes loop-invariant tests (usually null checks).
2584   if (!_head->is_CountedLoop()) { // Non-counted loop
2585     if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
2586       // Partial peel succeeded so terminate this round of loop opts
2587       return false;
2588     }
2589     if (should_peel) {            // Should we peel?
2590       if (PrintOpto) { tty->print_cr("should_peel"); }
2591       phase->do_peeling(this,old_new);
2592     } else if (should_unswitch) {
2593       phase->do_unswitching(this, old_new);
2594     }
2595     return true;
2596   }
2597   CountedLoopNode *cl = _head->as_CountedLoop();
2598 
2599   if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops
2600 
2601   // Do nothing special to pre- and post- loops
2602   if (cl->is_pre_loop() || cl->is_post_loop()) return true;
2603 
2604   // Compute loop trip count from profile data
2605   compute_profile_trip_cnt(phase);
2606 
2607   // Before attempting fancy unrolling, RCE or alignment, see if we want
2608   // to completely unroll this loop or do loop unswitching.
2609   if (cl->is_normal_loop()) {
2610     if (should_unswitch) {
2611       phase->do_unswitching(this, old_new);
2612       return true;
2613     }
2614     bool should_maximally_unroll =  policy_maximally_unroll(phase);
2615     if (should_maximally_unroll) {
2616       // Here we did some unrolling and peeling.  Eventually we will
2617       // completely unroll this loop and it will no longer be a loop.
2618       phase->do_maximally_unroll(this,old_new);
2619       return true;
2620     }
2621   }
2622 
2623   // Skip next optimizations if running low on nodes. Note that
2624   // policy_unswitching and policy_maximally_unroll have this check.
2625   int nodes_left = phase->C->max_node_limit() - phase->C->live_nodes();
2626   if ((int)(2 * _body.size()) > nodes_left) {
2627     return true;
2628   }
2629 
2630   // Counted loops may be peeled, may need some iterations run up
2631   // front for RCE, and may want to align loop refs to a cache
2632   // line.  Thus we clone a full loop up front whose trip count is
2633   // at least 1 (if peeling), but may be several more.
2634 
2635   // The main loop will start cache-line aligned with at least 1
2636   // iteration of the unrolled body (zero-trip test required) and
2637   // will have some range checks removed.
2638 
2639   // A post-loop will finish any odd iterations (leftover after
2640   // unrolling), plus any needed for RCE purposes.
2641 
2642   bool should_unroll = policy_unroll(phase);
2643 
2644   bool should_rce = policy_range_check(phase);
2645 
2646   bool should_align = policy_align(phase);
2647 
2648   // If not RCE'ing (iteration splitting) or Aligning, then we do not
2649   // need a pre-loop.  We may still need to peel an initial iteration but
2650   // we will not be needing an unknown number of pre-iterations.
2651   //
2652   // Basically, if may_rce_align reports FALSE first time through,
2653   // we will not be able to later do RCE or Aligning on this loop.
2654   bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
2655 
2656   // If we have any of these conditions (RCE, alignment, unrolling) met, then
2657   // we switch to the pre-/main-/post-loop model.  This model also covers
2658   // peeling.
2659   if (should_rce || should_align || should_unroll) {
2660     if (cl->is_normal_loop())  // Convert to 'pre/main/post' loops
2661       phase->insert_pre_post_loops(this,old_new, !may_rce_align);
2662 
2663     // Adjust the pre- and main-loop limits to let the pre and post loops run
2664     // with full checks, but the main-loop with no checks.  Remove said
2665     // checks from the main body.
2666     if (should_rce)
2667       phase->do_range_check(this,old_new);
2668 
2669     // Double loop body for unrolling.  Adjust the minimum-trip test (will do
2670     // twice as many iterations as before) and the main body limit (only do
2671     // an even number of trips).  If we are peeling, we might enable some RCE
2672     // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
2673     // peeling.
2674     if (should_unroll && !should_peel) {
2675       if (SuperWordLoopUnrollAnalysis) {
2676         phase->insert_vector_post_loop(this, old_new);
2677       }
2678       phase->do_unroll(this, old_new, true);
2679     }
2680 
2681     // Adjust the pre-loop limits to align the main body
2682     // iterations.
2683     if (should_align)
2684       Unimplemented();
2685 
2686   } else {                      // Else we have an unchanged counted loop
2687     if (should_peel)           // Might want to peel but do nothing else
2688       phase->do_peeling(this,old_new);
2689   }
2690   return true;
2691 }
2692 
2693 
2694 //=============================================================================
2695 //------------------------------iteration_split--------------------------------
2696 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
2697   // Recursively iteration split nested loops
2698   if (_child && !_child->iteration_split(phase, old_new))
2699     return false;
2700 
2701   // Clean out prior deadwood
2702   DCE_loop_body();
2703 
2704 
2705   // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
2706   // Replace with a 1-in-10 exit guess.
2707   if (_parent /*not the root loop*/ &&
2708       !_irreducible &&
2709       // Also ignore the occasional dead backedge
2710       !tail()->is_top()) {
2711     adjust_loop_exit_prob(phase);
2712   }
2713 
2714   // Gate unrolling, RCE and peeling efforts.
2715   if (!_child &&                // If not an inner loop, do not split
2716       !_irreducible &&
2717       _allow_optimizations &&
2718       !tail()->is_top()) {     // Also ignore the occasional dead backedge
2719     if (!_has_call) {
2720         if (!iteration_split_impl(phase, old_new)) {
2721           return false;
2722         }
2723     } else if (policy_unswitching(phase)) {
2724       phase->do_unswitching(this, old_new);
2725     }
2726   }
2727 
2728   // Minor offset re-organization to remove loop-fallout uses of
2729   // trip counter when there was no major reshaping.
2730   phase->reorg_offsets(this);
2731 
2732   if (_next && !_next->iteration_split(phase, old_new))
2733     return false;
2734   return true;
2735 }
2736 
2737 
2738 //=============================================================================
2739 // Process all the loops in the loop tree and replace any fill
2740 // patterns with an intrinsic version.
2741 bool PhaseIdealLoop::do_intrinsify_fill() {
2742   bool changed = false;
2743   for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2744     IdealLoopTree* lpt = iter.current();
2745     changed |= intrinsify_fill(lpt);
2746   }
2747   return changed;
2748 }
2749 
2750 
2751 // Examine an inner loop looking for a a single store of an invariant
2752 // value in a unit stride loop,
2753 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
2754                                      Node*& shift, Node*& con) {
2755   const char* msg = NULL;
2756   Node* msg_node = NULL;
2757 
2758   store_value = NULL;
2759   con = NULL;
2760   shift = NULL;
2761 
2762   // Process the loop looking for stores.  If there are multiple
2763   // stores or extra control flow give at this point.
2764   CountedLoopNode* head = lpt->_head->as_CountedLoop();
2765   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2766     Node* n = lpt->_body.at(i);
2767     if (n->outcnt() == 0) continue; // Ignore dead
2768     if (n->is_Store()) {
2769       if (store != NULL) {
2770         msg = "multiple stores";
2771         break;
2772       }
2773       int opc = n->Opcode();
2774       if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass || opc == Op_StoreCM) {
2775         msg = "oop fills not handled";
2776         break;
2777       }
2778       Node* value = n->in(MemNode::ValueIn);
2779       if (!lpt->is_invariant(value)) {
2780         msg  = "variant store value";
2781       } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
2782         msg = "not array address";
2783       }
2784       store = n;
2785       store_value = value;
2786     } else if (n->is_If() && n != head->loopexit()) {
2787       msg = "extra control flow";
2788       msg_node = n;
2789     }
2790   }
2791 
2792   if (store == NULL) {
2793     // No store in loop
2794     return false;
2795   }
2796 
2797   if (msg == NULL && head->stride_con() != 1) {
2798     // could handle negative strides too
2799     if (head->stride_con() < 0) {
2800       msg = "negative stride";
2801     } else {
2802       msg = "non-unit stride";
2803     }
2804   }
2805 
2806   if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
2807     msg = "can't handle store address";
2808     msg_node = store->in(MemNode::Address);
2809   }
2810 
2811   if (msg == NULL &&
2812       (!store->in(MemNode::Memory)->is_Phi() ||
2813        store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
2814     msg = "store memory isn't proper phi";
2815     msg_node = store->in(MemNode::Memory);
2816   }
2817 
2818   // Make sure there is an appropriate fill routine
2819   BasicType t = store->as_Mem()->memory_type();
2820   const char* fill_name;
2821   if (msg == NULL &&
2822       StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
2823     msg = "unsupported store";
2824     msg_node = store;
2825   }
2826 
2827   if (msg != NULL) {
2828 #ifndef PRODUCT
2829     if (TraceOptimizeFill) {
2830       tty->print_cr("not fill intrinsic candidate: %s", msg);
2831       if (msg_node != NULL) msg_node->dump();
2832     }
2833 #endif
2834     return false;
2835   }
2836 
2837   // Make sure the address expression can be handled.  It should be
2838   // head->phi * elsize + con.  head->phi might have a ConvI2L(CastII()).
2839   Node* elements[4];
2840   Node* cast = NULL;
2841   Node* conv = NULL;
2842   bool found_index = false;
2843   int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
2844   for (int e = 0; e < count; e++) {
2845     Node* n = elements[e];
2846     if (n->is_Con() && con == NULL) {
2847       con = n;
2848     } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
2849       Node* value = n->in(1);
2850 #ifdef _LP64
2851       if (value->Opcode() == Op_ConvI2L) {
2852         conv = value;
2853         value = value->in(1);
2854       }
2855       if (value->Opcode() == Op_CastII &&
2856           value->as_CastII()->has_range_check()) {
2857         // Skip range check dependent CastII nodes
2858         cast = value;
2859         value = value->in(1);
2860       }
2861 #endif
2862       if (value != head->phi()) {
2863         msg = "unhandled shift in address";
2864       } else {
2865         if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) {
2866           msg = "scale doesn't match";
2867         } else {
2868           found_index = true;
2869           shift = n;
2870         }
2871       }
2872     } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
2873       conv = n;
2874       n = n->in(1);
2875       if (n->Opcode() == Op_CastII &&
2876           n->as_CastII()->has_range_check()) {
2877         // Skip range check dependent CastII nodes
2878         cast = n;
2879         n = n->in(1);
2880       }
2881       if (n == head->phi()) {
2882         found_index = true;
2883       } else {
2884         msg = "unhandled input to ConvI2L";
2885       }
2886     } else if (n == head->phi()) {
2887       // no shift, check below for allowed cases
2888       found_index = true;
2889     } else {
2890       msg = "unhandled node in address";
2891       msg_node = n;
2892     }
2893   }
2894 
2895   if (count == -1) {
2896     msg = "malformed address expression";
2897     msg_node = store;
2898   }
2899 
2900   if (!found_index) {
2901     msg = "missing use of index";
2902   }
2903 
2904   // byte sized items won't have a shift
2905   if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
2906     msg = "can't find shift";
2907     msg_node = store;
2908   }
2909 
2910   if (msg != NULL) {
2911 #ifndef PRODUCT
2912     if (TraceOptimizeFill) {
2913       tty->print_cr("not fill intrinsic: %s", msg);
2914       if (msg_node != NULL) msg_node->dump();
2915     }
2916 #endif
2917     return false;
2918   }
2919 
2920   // No make sure all the other nodes in the loop can be handled
2921   VectorSet ok(Thread::current()->resource_area());
2922 
2923   // store related values are ok
2924   ok.set(store->_idx);
2925   ok.set(store->in(MemNode::Memory)->_idx);
2926 
2927   CountedLoopEndNode* loop_exit = head->loopexit();
2928   guarantee(loop_exit != NULL, "no loop exit node");
2929 
2930   // Loop structure is ok
2931   ok.set(head->_idx);
2932   ok.set(loop_exit->_idx);
2933   ok.set(head->phi()->_idx);
2934   ok.set(head->incr()->_idx);
2935   ok.set(loop_exit->cmp_node()->_idx);
2936   ok.set(loop_exit->in(1)->_idx);
2937 
2938   // Address elements are ok
2939   if (con)   ok.set(con->_idx);
2940   if (shift) ok.set(shift->_idx);
2941   if (cast)  ok.set(cast->_idx);
2942   if (conv)  ok.set(conv->_idx);
2943 
2944   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2945     Node* n = lpt->_body.at(i);
2946     if (n->outcnt() == 0) continue; // Ignore dead
2947     if (ok.test(n->_idx)) continue;
2948     // Backedge projection is ok
2949     if (n->is_IfTrue() && n->in(0) == loop_exit) continue;
2950     if (!n->is_AddP()) {
2951       msg = "unhandled node";
2952       msg_node = n;
2953       break;
2954     }
2955   }
2956 
2957   // Make sure no unexpected values are used outside the loop
2958   for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2959     Node* n = lpt->_body.at(i);
2960     // These values can be replaced with other nodes if they are used
2961     // outside the loop.
2962     if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue;
2963     for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
2964       Node* use = iter.get();
2965       if (!lpt->_body.contains(use)) {
2966         msg = "node is used outside loop";
2967         // lpt->_body.dump();
2968         msg_node = n;
2969         break;
2970       }
2971     }
2972   }
2973 
2974 #ifdef ASSERT
2975   if (TraceOptimizeFill) {
2976     if (msg != NULL) {
2977       tty->print_cr("no fill intrinsic: %s", msg);
2978       if (msg_node != NULL) msg_node->dump();
2979     } else {
2980       tty->print_cr("fill intrinsic for:");
2981     }
2982     store->dump();
2983     if (Verbose) {
2984       lpt->_body.dump();
2985     }
2986   }
2987 #endif
2988 
2989   return msg == NULL;
2990 }
2991 
2992 
2993 
2994 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
2995   // Only for counted inner loops
2996   if (!lpt->is_counted() || !lpt->is_inner()) {
2997     return false;
2998   }
2999 
3000   // Must have constant stride
3001   CountedLoopNode* head = lpt->_head->as_CountedLoop();
3002   if (!head->is_valid_counted_loop() || !head->is_normal_loop()) {
3003     return false;
3004   }
3005 
3006   // Check that the body only contains a store of a loop invariant
3007   // value that is indexed by the loop phi.
3008   Node* store = NULL;
3009   Node* store_value = NULL;
3010   Node* shift = NULL;
3011   Node* offset = NULL;
3012   if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
3013     return false;
3014   }
3015 
3016 #ifndef PRODUCT
3017   if (TraceLoopOpts) {
3018     tty->print("ArrayFill    ");
3019     lpt->dump_head();
3020   }
3021 #endif
3022 
3023   // Now replace the whole loop body by a call to a fill routine that
3024   // covers the same region as the loop.
3025   Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
3026 
3027   // Build an expression for the beginning of the copy region
3028   Node* index = head->init_trip();
3029 #ifdef _LP64
3030   index = new ConvI2LNode(index);
3031   _igvn.register_new_node_with_optimizer(index);
3032 #endif
3033   if (shift != NULL) {
3034     // byte arrays don't require a shift but others do.
3035     index = new LShiftXNode(index, shift->in(2));
3036     _igvn.register_new_node_with_optimizer(index);
3037   }
3038   index = new AddPNode(base, base, index);
3039   _igvn.register_new_node_with_optimizer(index);
3040   Node* from = new AddPNode(base, index, offset);
3041   _igvn.register_new_node_with_optimizer(from);
3042   // Compute the number of elements to copy
3043   Node* len = new SubINode(head->limit(), head->init_trip());
3044   _igvn.register_new_node_with_optimizer(len);
3045 
3046   BasicType t = store->as_Mem()->memory_type();
3047   bool aligned = false;
3048   if (offset != NULL && head->init_trip()->is_Con()) {
3049     int element_size = type2aelembytes(t);
3050     aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
3051   }
3052 
3053   // Build a call to the fill routine
3054   const char* fill_name;
3055   address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
3056   assert(fill != NULL, "what?");
3057 
3058   // Convert float/double to int/long for fill routines
3059   if (t == T_FLOAT) {
3060     store_value = new MoveF2INode(store_value);
3061     _igvn.register_new_node_with_optimizer(store_value);
3062   } else if (t == T_DOUBLE) {
3063     store_value = new MoveD2LNode(store_value);
3064     _igvn.register_new_node_with_optimizer(store_value);
3065   }
3066 
3067   Node* mem_phi = store->in(MemNode::Memory);
3068   Node* result_ctrl;
3069   Node* result_mem;
3070   const TypeFunc* call_type = OptoRuntime::array_fill_Type();
3071   CallLeafNode *call = new CallLeafNoFPNode(call_type, fill,
3072                                             fill_name, TypeAryPtr::get_array_body_type(t));
3073   uint cnt = 0;
3074   call->init_req(TypeFunc::Parms + cnt++, from);
3075   call->init_req(TypeFunc::Parms + cnt++, store_value);
3076 #ifdef _LP64
3077   len = new ConvI2LNode(len);
3078   _igvn.register_new_node_with_optimizer(len);
3079 #endif
3080   call->init_req(TypeFunc::Parms + cnt++, len);
3081 #ifdef _LP64
3082   call->init_req(TypeFunc::Parms + cnt++, C->top());
3083 #endif
3084   call->init_req(TypeFunc::Control,   head->init_control());
3085   call->init_req(TypeFunc::I_O,       C->top());       // Does no I/O.
3086   call->init_req(TypeFunc::Memory,    mem_phi->in(LoopNode::EntryControl));
3087   call->init_req(TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr));
3088   call->init_req(TypeFunc::FramePtr,  C->start()->proj_out(TypeFunc::FramePtr));
3089   _igvn.register_new_node_with_optimizer(call);
3090   result_ctrl = new ProjNode(call,TypeFunc::Control);
3091   _igvn.register_new_node_with_optimizer(result_ctrl);
3092   result_mem = new ProjNode(call,TypeFunc::Memory);
3093   _igvn.register_new_node_with_optimizer(result_mem);
3094 
3095 /* Disable following optimization until proper fix (add missing checks).
3096 
3097   // If this fill is tightly coupled to an allocation and overwrites
3098   // the whole body, allow it to take over the zeroing.
3099   AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
3100   if (alloc != NULL && alloc->is_AllocateArray()) {
3101     Node* length = alloc->as_AllocateArray()->Ideal_length();
3102     if (head->limit() == length &&
3103         head->init_trip() == _igvn.intcon(0)) {
3104       if (TraceOptimizeFill) {
3105         tty->print_cr("Eliminated zeroing in allocation");
3106       }
3107       alloc->maybe_set_complete(&_igvn);
3108     } else {
3109 #ifdef ASSERT
3110       if (TraceOptimizeFill) {
3111         tty->print_cr("filling array but bounds don't match");
3112         alloc->dump();
3113         head->init_trip()->dump();
3114         head->limit()->dump();
3115         length->dump();
3116       }
3117 #endif
3118     }
3119   }
3120 */
3121 
3122   // Redirect the old control and memory edges that are outside the loop.
3123   Node* exit = head->loopexit()->proj_out(0);
3124   // Sometimes the memory phi of the head is used as the outgoing
3125   // state of the loop.  It's safe in this case to replace it with the
3126   // result_mem.
3127   _igvn.replace_node(store->in(MemNode::Memory), result_mem);
3128   lazy_replace(exit, result_ctrl);
3129   _igvn.replace_node(store, result_mem);
3130   // Any uses the increment outside of the loop become the loop limit.
3131   _igvn.replace_node(head->incr(), head->limit());
3132 
3133   // Disconnect the head from the loop.
3134   for (uint i = 0; i < lpt->_body.size(); i++) {
3135     Node* n = lpt->_body.at(i);
3136     _igvn.replace_node(n, C->top());
3137   }
3138 
3139   return true;
3140 }