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 int nodes_left = phase->C->max_node_limit() - phase->C->live_nodes(); 65 if ((int)(2 * _body.size()) > nodes_left) { 66 return false; // Too speculative if running low on nodes. 67 } 68 LoopNode* head = _head->as_Loop(); 69 if (head->unswitch_count() + 1 > head->unswitch_max()) { 70 return false; 71 } 72 return phase->find_unswitching_candidate(this) != NULL; 73 } 74 75 //------------------------------find_unswitching_candidate----------------------------- 76 // Find candidate "if" for unswitching 77 IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const { 78 79 // Find first invariant test that doesn't exit the loop 80 LoopNode *head = loop->_head->as_Loop(); 81 IfNode* unswitch_iff = NULL; 82 Node* n = head->in(LoopNode::LoopBackControl); 83 while (n != head) { 84 Node* n_dom = idom(n); 85 if (n->is_Region()) { 86 if (n_dom->is_If()) { 87 IfNode* iff = n_dom->as_If(); 88 if (iff->in(1)->is_Bool()) { 89 BoolNode* bol = iff->in(1)->as_Bool(); 90 if (bol->in(1)->is_Cmp()) { 91 // If condition is invariant and not a loop exit, 92 // then found reason to unswitch. 93 if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) { 94 unswitch_iff = iff; 95 } 96 } 97 } 98 } 99 } 100 n = n_dom; 101 } 102 return unswitch_iff; 103 } 104 105 //------------------------------do_unswitching----------------------------- 106 // Clone loop with an invariant test (that does not exit) and 107 // insert a clone of the test that selects which version to 108 // execute. 109 void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) { 110 111 // Find first invariant test that doesn't exit the loop 112 LoopNode *head = loop->_head->as_Loop(); 113 114 IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop); 115 assert(unswitch_iff != NULL, "should be at least one"); 116 117 #ifndef PRODUCT 118 if (TraceLoopOpts) { 119 tty->print("Unswitch %d ", head->unswitch_count()+1); 120 loop->dump_head(); 121 } 122 #endif 123 124 // Need to revert back to normal loop 125 if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) { 126 head->as_CountedLoop()->set_normal_loop(); 127 } 128 129 ProjNode* proj_true = create_slow_version_of_loop(loop, old_new); 130 131 #ifdef ASSERT 132 Node* uniqc = proj_true->unique_ctrl_out(); 133 Node* entry = head->in(LoopNode::EntryControl); 134 Node* predicate = find_predicate(entry); 135 if (predicate != NULL && LoopLimitCheck && UseLoopPredicate) { 136 // We may have two predicates, find first. 137 entry = find_predicate(entry->in(0)->in(0)); 138 if (entry != NULL) predicate = entry; 139 } 140 if (predicate != NULL) predicate = predicate->in(0); 141 assert(proj_true->is_IfTrue() && 142 (predicate == NULL && uniqc == head || 143 predicate != NULL && uniqc == predicate), "by construction"); 144 #endif 145 // Increment unswitch count 146 LoopNode* head_clone = old_new[head->_idx]->as_Loop(); 147 int nct = head->unswitch_count() + 1; 148 head->set_unswitch_count(nct); 149 head_clone->set_unswitch_count(nct); 150 151 // Add test to new "if" outside of loop 152 IfNode* invar_iff = proj_true->in(0)->as_If(); 153 Node* invar_iff_c = invar_iff->in(0); 154 BoolNode* bol = unswitch_iff->in(1)->as_Bool(); 155 invar_iff->set_req(1, bol); 156 invar_iff->_prob = unswitch_iff->_prob; 157 158 ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj(); 159 160 // Hoist invariant casts out of each loop to the appropriate 161 // control projection. 162 163 Node_List worklist; 164 165 for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) { 166 ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj(); 167 // Copy to a worklist for easier manipulation 168 for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) { 169 Node* use = proj->fast_out(j); 170 if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) { 171 worklist.push(use); 172 } 173 } 174 ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj(); 175 while (worklist.size() > 0) { 176 Node* use = worklist.pop(); 177 Node* nuse = use->clone(); 178 nuse->set_req(0, invar_proj); 179 _igvn.replace_input_of(use, 1, nuse); 180 register_new_node(nuse, invar_proj); 181 // Same for the clone 182 Node* use_clone = old_new[use->_idx]; 183 _igvn.replace_input_of(use_clone, 1, nuse); 184 } 185 } 186 187 // Hardwire the control paths in the loops into if(true) and if(false) 188 _igvn.rehash_node_delayed(unswitch_iff); 189 short_circuit_if(unswitch_iff, proj_true); 190 191 IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If(); 192 _igvn.rehash_node_delayed(unswitch_iff_clone); 193 short_circuit_if(unswitch_iff_clone, proj_false); 194 195 // Reoptimize loops 196 loop->record_for_igvn(); 197 for(int i = loop->_body.size() - 1; i >= 0 ; i--) { 198 Node *n = loop->_body[i]; 199 Node *n_clone = old_new[n->_idx]; 200 _igvn._worklist.push(n_clone); 201 } 202 203 #ifndef PRODUCT 204 if (TraceLoopUnswitching) { 205 tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d", 206 head->_idx, unswitch_iff->_idx, 207 old_new[head->_idx]->_idx, unswitch_iff_clone->_idx); 208 } 209 #endif 210 211 C->set_major_progress(); 212 } 213 214 //-------------------------create_slow_version_of_loop------------------------ 215 // Create a slow version of the loop by cloning the loop 216 // and inserting an if to select fast-slow versions. 217 // Return control projection of the entry to the fast version. 218 ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop, 219 Node_List &old_new) { 220 LoopNode* head = loop->_head->as_Loop(); 221 bool counted_loop = head->is_CountedLoop(); 222 Node* entry = head->in(LoopNode::EntryControl); 223 _igvn.rehash_node_delayed(entry); 224 IdealLoopTree* outer_loop = loop->_parent; 225 226 Node *cont = _igvn.intcon(1); 227 set_ctrl(cont, C->root()); 228 Node* opq = new Opaque1Node(C, cont); 229 register_node(opq, outer_loop, entry, dom_depth(entry)); 230 Node *bol = new Conv2BNode(opq); 231 register_node(bol, outer_loop, entry, dom_depth(entry)); 232 IfNode* iff = new IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN); 233 register_node(iff, outer_loop, entry, dom_depth(entry)); 234 ProjNode* iffast = new IfTrueNode(iff); 235 register_node(iffast, outer_loop, iff, dom_depth(iff)); 236 ProjNode* ifslow = new IfFalseNode(iff); 237 register_node(ifslow, outer_loop, iff, dom_depth(iff)); 238 239 // Clone the loop body. The clone becomes the fast loop. The 240 // original pre-header will (illegally) have 3 control users 241 // (old & new loops & new if). 242 clone_loop(loop, old_new, dom_depth(head), iff); 243 assert(old_new[head->_idx]->is_Loop(), "" ); 244 245 // Fast (true) control 246 Node* iffast_pred = clone_loop_predicates(entry, iffast, !counted_loop); 247 _igvn.replace_input_of(head, LoopNode::EntryControl, iffast_pred); 248 set_idom(head, iffast_pred, dom_depth(head)); 249 250 // Slow (false) control 251 Node* ifslow_pred = clone_loop_predicates(entry, ifslow, !counted_loop); 252 LoopNode* slow_head = old_new[head->_idx]->as_Loop(); 253 _igvn.replace_input_of(slow_head, LoopNode::EntryControl, ifslow_pred); 254 set_idom(slow_head, ifslow_pred, dom_depth(slow_head)); 255 256 recompute_dom_depth(); 257 258 return iffast; 259 }