1 /* 2 * Copyright (c) 2006, 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "memory/allocation.inline.hpp" 27 #include "opto/connode.hpp" 28 #include "opto/convertnode.hpp" 29 #include "opto/loopnode.hpp" 30 #include "opto/opaquenode.hpp" 31 #include "opto/rootnode.hpp" 32 33 //================= Loop Unswitching ===================== 34 // 35 // orig: transformed: 36 // if (invariant-test) then 37 // predicate predicate 38 // loop loop 39 // stmt1 stmt1 40 // if (invariant-test) then stmt2 41 // stmt2 stmt4 42 // else endloop 43 // stmt3 else 44 // endif predicate [clone] 45 // stmt4 loop [clone] 46 // endloop stmt1 [clone] 47 // stmt3 48 // stmt4 [clone] 49 // endloop 50 // endif 51 // 52 // Note: the "else" clause may be empty 53 54 //------------------------------policy_unswitching----------------------------- 55 // Return TRUE or FALSE if the loop should be unswitched 56 // (ie. clone loop with an invariant test that does not exit the loop) 57 bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const { 58 if( !LoopUnswitching ) { 59 return false; 60 } 61 if (!_head->is_Loop()) { 62 return false; 63 } 64 65 // check for vectorized loops, any unswitching was already applied 66 if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) { 67 return false; 68 } 69 70 int nodes_left = phase->C->max_node_limit() - phase->C->live_nodes(); 71 if ((int)(2 * _body.size()) > nodes_left) { 72 return false; // Too speculative if running low on nodes. 73 } 74 LoopNode* head = _head->as_Loop(); 75 if (head->unswitch_count() + 1 > head->unswitch_max()) { 76 return false; 77 } 78 return phase->find_unswitching_candidate(this) != NULL; 79 } 80 81 //------------------------------find_unswitching_candidate----------------------------- 82 // Find candidate "if" for unswitching 83 IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const { 84 85 // Find first invariant test that doesn't exit the loop 86 LoopNode *head = loop->_head->as_Loop(); 87 IfNode* unswitch_iff = NULL; 88 Node* n = head->in(LoopNode::LoopBackControl); 89 while (n != head) { 90 Node* n_dom = idom(n); 91 if (n->is_Region()) { 92 if (n_dom->is_If()) { 93 IfNode* iff = n_dom->as_If(); 94 if (iff->in(1)->is_Bool()) { 95 BoolNode* bol = iff->in(1)->as_Bool(); 96 if (bol->in(1)->is_Cmp()) { 97 // If condition is invariant and not a loop exit, 98 // then found reason to unswitch. 99 if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) { 100 unswitch_iff = iff; 101 } 102 } 103 } 104 } 105 } 106 n = n_dom; 107 } 108 return unswitch_iff; 109 } 110 111 //------------------------------do_unswitching----------------------------- 112 // Clone loop with an invariant test (that does not exit) and 113 // insert a clone of the test that selects which version to 114 // execute. 115 void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) { 116 117 // Find first invariant test that doesn't exit the loop 118 LoopNode *head = loop->_head->as_Loop(); 119 120 IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop); 121 assert(unswitch_iff != NULL, "should be at least one"); 122 123 #ifndef PRODUCT 124 if (TraceLoopOpts) { 125 tty->print("Unswitch %d ", head->unswitch_count()+1); 126 loop->dump_head(); 127 } 128 #endif 129 130 // Need to revert back to normal loop 131 if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) { 132 head->as_CountedLoop()->set_normal_loop(); 133 } 134 135 ProjNode* proj_true = create_slow_version_of_loop(loop, old_new); 136 137 #ifdef ASSERT 138 Node* uniqc = proj_true->unique_ctrl_out(); 139 Node* entry = head->in(LoopNode::EntryControl); 140 Node* predicate = find_predicate(entry); 141 if (predicate != NULL && LoopLimitCheck && UseLoopPredicate) { 142 // We may have two predicates, find first. 143 entry = find_predicate(entry->in(0)->in(0)); 144 if (entry != NULL) predicate = entry; 145 } 146 if (predicate != NULL) predicate = predicate->in(0); 147 assert(proj_true->is_IfTrue() && 148 (predicate == NULL && uniqc == head || 149 predicate != NULL && uniqc == predicate), "by construction"); 150 #endif 151 // Increment unswitch count 152 LoopNode* head_clone = old_new[head->_idx]->as_Loop(); 153 int nct = head->unswitch_count() + 1; 154 head->set_unswitch_count(nct); 155 head_clone->set_unswitch_count(nct); 156 157 // Add test to new "if" outside of loop 158 IfNode* invar_iff = proj_true->in(0)->as_If(); 159 Node* invar_iff_c = invar_iff->in(0); 160 BoolNode* bol = unswitch_iff->in(1)->as_Bool(); 161 invar_iff->set_req(1, bol); 162 invar_iff->_prob = unswitch_iff->_prob; 163 164 ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj(); 165 166 // Hoist invariant casts out of each loop to the appropriate 167 // control projection. 168 169 Node_List worklist; 170 171 for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) { 172 ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj(); 173 // Copy to a worklist for easier manipulation 174 for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) { 175 Node* use = proj->fast_out(j); 176 if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) { 177 worklist.push(use); 178 } 179 } 180 ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj(); 181 while (worklist.size() > 0) { 182 Node* use = worklist.pop(); 183 Node* nuse = use->clone(); 184 nuse->set_req(0, invar_proj); 185 _igvn.replace_input_of(use, 1, nuse); 186 register_new_node(nuse, invar_proj); 187 // Same for the clone 188 Node* use_clone = old_new[use->_idx]; 189 _igvn.replace_input_of(use_clone, 1, nuse); 190 } 191 } 192 193 // Hardwire the control paths in the loops into if(true) and if(false) 194 _igvn.rehash_node_delayed(unswitch_iff); 195 short_circuit_if(unswitch_iff, proj_true); 196 197 IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If(); 198 _igvn.rehash_node_delayed(unswitch_iff_clone); 199 short_circuit_if(unswitch_iff_clone, proj_false); 200 201 // Reoptimize loops 202 loop->record_for_igvn(); 203 for(int i = loop->_body.size() - 1; i >= 0 ; i--) { 204 Node *n = loop->_body[i]; 205 Node *n_clone = old_new[n->_idx]; 206 _igvn._worklist.push(n_clone); 207 } 208 209 #ifndef PRODUCT 210 if (TraceLoopUnswitching) { 211 tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d", 212 head->_idx, unswitch_iff->_idx, 213 old_new[head->_idx]->_idx, unswitch_iff_clone->_idx); 214 } 215 #endif 216 217 C->set_major_progress(); 218 } 219 220 //-------------------------create_slow_version_of_loop------------------------ 221 // Create a slow version of the loop by cloning the loop 222 // and inserting an if to select fast-slow versions. 223 // Return control projection of the entry to the fast version. 224 ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop, 225 Node_List &old_new) { 226 LoopNode* head = loop->_head->as_Loop(); 227 bool counted_loop = head->is_CountedLoop(); 228 Node* entry = head->in(LoopNode::EntryControl); 229 _igvn.rehash_node_delayed(entry); 230 IdealLoopTree* outer_loop = loop->_parent; 231 232 Node *cont = _igvn.intcon(1); 233 set_ctrl(cont, C->root()); 234 Node* opq = new Opaque1Node(C, cont); 235 register_node(opq, outer_loop, entry, dom_depth(entry)); 236 Node *bol = new Conv2BNode(opq); 237 register_node(bol, outer_loop, entry, dom_depth(entry)); 238 IfNode* iff = new IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN); 239 register_node(iff, outer_loop, entry, dom_depth(entry)); 240 ProjNode* iffast = new IfTrueNode(iff); 241 register_node(iffast, outer_loop, iff, dom_depth(iff)); 242 ProjNode* ifslow = new IfFalseNode(iff); 243 register_node(ifslow, outer_loop, iff, dom_depth(iff)); 244 245 // Clone the loop body. The clone becomes the fast loop. The 246 // original pre-header will (illegally) have 3 control users 247 // (old & new loops & new if). 248 clone_loop(loop, old_new, dom_depth(head), iff); 249 assert(old_new[head->_idx]->is_Loop(), "" ); 250 251 // Fast (true) control 252 Node* iffast_pred = clone_loop_predicates(entry, iffast, !counted_loop); 253 _igvn.replace_input_of(head, LoopNode::EntryControl, iffast_pred); 254 set_idom(head, iffast_pred, dom_depth(head)); 255 256 // Slow (false) control 257 Node* ifslow_pred = clone_loop_predicates(entry, ifslow, !counted_loop); 258 LoopNode* slow_head = old_new[head->_idx]->as_Loop(); 259 _igvn.replace_input_of(slow_head, LoopNode::EntryControl, ifslow_pred); 260 set_idom(slow_head, ifslow_pred, dom_depth(slow_head)); 261 262 recompute_dom_depth(); 263 264 return iffast; 265 }