1 /* 2 * Copyright (c) 2006, 2011, 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/loopnode.hpp" 29 #include "opto/rootnode.hpp" 30 31 //================= Loop Unswitching ===================== 32 // 33 // orig: transformed: 34 // if (invariant-test) then 35 // predicate predicate 36 // loop loop 37 // stmt1 stmt1 38 // if (invariant-test) then stmt2 39 // stmt2 stmt4 40 // else endloop 41 // stmt3 else 42 // endif predicate [clone] 43 // stmt4 loop [clone] 44 // endloop stmt1 [clone] 45 // stmt3 46 // stmt4 [clone] 47 // endloop 48 // endif 49 // 50 // Note: the "else" clause may be empty 51 52 //------------------------------policy_unswitching----------------------------- 53 // Return TRUE or FALSE if the loop should be unswitched 54 // (ie. clone loop with an invariant test that does not exit the loop) 55 bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const { 56 if( !LoopUnswitching ) { 57 return false; 58 } 59 if (!_head->is_Loop()) { 60 return false; 61 } 62 uint nodes_left = MaxNodeLimit - phase->C->unique(); 63 if (2 * _body.size() > nodes_left) { 64 return false; // Too speculative if running low on nodes. 65 } 66 LoopNode* head = _head->as_Loop(); 67 if (head->unswitch_count() + 1 > head->unswitch_max()) { 68 return false; 69 } 70 return phase->find_unswitching_candidate(this) != NULL; 71 } 72 73 //------------------------------find_unswitching_candidate----------------------------- 74 // Find candidate "if" for unswitching 75 IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const { 76 77 // Find first invariant test that doesn't exit the loop 78 LoopNode *head = loop->_head->as_Loop(); 79 IfNode* unswitch_iff = NULL; 80 Node* n = head->in(LoopNode::LoopBackControl); 81 while (n != head) { 82 Node* n_dom = idom(n); 83 if (n->is_Region()) { 84 if (n_dom->is_If()) { 85 IfNode* iff = n_dom->as_If(); 86 if (iff->in(1)->is_Bool()) { 87 BoolNode* bol = iff->in(1)->as_Bool(); 88 if (bol->in(1)->is_Cmp()) { 89 // If condition is invariant and not a loop exit, 90 // then found reason to unswitch. 91 if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) { 92 unswitch_iff = iff; 93 } 94 } 95 } 96 } 97 } 98 n = n_dom; 99 } 100 return unswitch_iff; 101 } 102 103 //------------------------------do_unswitching----------------------------- 104 // Clone loop with an invariant test (that does not exit) and 105 // insert a clone of the test that selects which version to 106 // execute. 107 void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) { 108 109 // Find first invariant test that doesn't exit the loop 110 LoopNode *head = loop->_head->as_Loop(); 111 112 IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop); 113 assert(unswitch_iff != NULL, "should be at least one"); 114 115 #ifndef PRODUCT 116 if (TraceLoopOpts) { 117 tty->print("Unswitch %d ", head->unswitch_count()+1); 118 loop->dump_head(); 119 } 120 #endif 121 122 // Need to revert back to normal loop 123 if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) { 124 head->as_CountedLoop()->set_normal_loop(); 125 } 126 127 ProjNode* proj_true = create_slow_version_of_loop(loop, old_new); 128 129 #ifdef ASSERT 130 Node* uniqc = proj_true->unique_ctrl_out(); 131 Node* entry = head->in(LoopNode::EntryControl); 132 Node* predicate = find_predicate(entry); 133 if (predicate != NULL && LoopLimitCheck && UseLoopPredicate) { 134 // We may have two predicates, find first. 135 entry = find_predicate(entry->in(0)->in(0)); 136 if (entry != NULL) predicate = entry; 137 } 138 if (predicate != NULL) predicate = predicate->in(0); 139 assert(proj_true->is_IfTrue() && 140 (predicate == NULL && uniqc == head || 141 predicate != NULL && uniqc == predicate), "by construction"); 142 #endif 143 // Increment unswitch count 144 LoopNode* head_clone = old_new[head->_idx]->as_Loop(); 145 int nct = head->unswitch_count() + 1; 146 head->set_unswitch_count(nct); 147 head_clone->set_unswitch_count(nct); 148 149 // Add test to new "if" outside of loop 150 IfNode* invar_iff = proj_true->in(0)->as_If(); 151 Node* invar_iff_c = invar_iff->in(0); 152 BoolNode* bol = unswitch_iff->in(1)->as_Bool(); 153 invar_iff->set_req(1, bol); 154 invar_iff->_prob = unswitch_iff->_prob; 155 156 ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj(); 157 158 // Hoist invariant casts out of each loop to the appropriate 159 // control projection. 160 161 Node_List worklist; 162 163 for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) { 164 ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj(); 165 // Copy to a worklist for easier manipulation 166 for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) { 167 Node* use = proj->fast_out(j); 168 if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) { 169 worklist.push(use); 170 } 171 } 172 ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj(); 173 while (worklist.size() > 0) { 174 Node* use = worklist.pop(); 175 Node* nuse = use->clone(); 176 nuse->set_req(0, invar_proj); 177 _igvn.hash_delete(use); 178 use->set_req(1, nuse); 179 _igvn._worklist.push(use); 180 register_new_node(nuse, invar_proj); 181 // Same for the clone 182 Node* use_clone = old_new[use->_idx]; 183 _igvn.hash_delete(use_clone); 184 use_clone->set_req(1, nuse); 185 _igvn._worklist.push(use_clone); 186 } 187 } 188 189 // Hardwire the control paths in the loops into if(true) and if(false) 190 _igvn.hash_delete(unswitch_iff); 191 short_circuit_if(unswitch_iff, proj_true); 192 _igvn._worklist.push(unswitch_iff); 193 194 IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If(); 195 _igvn.hash_delete(unswitch_iff_clone); 196 short_circuit_if(unswitch_iff_clone, proj_false); 197 _igvn._worklist.push(unswitch_iff_clone); 198 199 // Reoptimize loops 200 loop->record_for_igvn(); 201 for(int i = loop->_body.size() - 1; i >= 0 ; i--) { 202 Node *n = loop->_body[i]; 203 Node *n_clone = old_new[n->_idx]; 204 _igvn._worklist.push(n_clone); 205 } 206 207 #ifndef PRODUCT 208 if (TraceLoopUnswitching) { 209 tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d", 210 head->_idx, unswitch_iff->_idx, 211 old_new[head->_idx]->_idx, unswitch_iff_clone->_idx); 212 } 213 #endif 214 215 C->set_major_progress(); 216 } 217 218 //-------------------------create_slow_version_of_loop------------------------ 219 // Create a slow version of the loop by cloning the loop 220 // and inserting an if to select fast-slow versions. 221 // Return control projection of the entry to the fast version. 222 ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop, 223 Node_List &old_new) { 224 LoopNode* head = loop->_head->as_Loop(); 225 bool counted_loop = head->is_CountedLoop(); 226 Node* entry = head->in(LoopNode::EntryControl); 227 _igvn.hash_delete(entry); 228 _igvn._worklist.push(entry); 229 IdealLoopTree* outer_loop = loop->_parent; 230 231 Node *cont = _igvn.intcon(1); 232 set_ctrl(cont, C->root()); 233 Node* opq = new (C, 2) Opaque1Node(C, cont); 234 register_node(opq, outer_loop, entry, dom_depth(entry)); 235 Node *bol = new (C, 2) Conv2BNode(opq); 236 register_node(bol, outer_loop, entry, dom_depth(entry)); 237 IfNode* iff = new (C, 2) IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN); 238 register_node(iff, outer_loop, entry, dom_depth(entry)); 239 ProjNode* iffast = new (C, 1) IfTrueNode(iff); 240 register_node(iffast, outer_loop, iff, dom_depth(iff)); 241 ProjNode* ifslow = new (C, 1) IfFalseNode(iff); 242 register_node(ifslow, outer_loop, iff, dom_depth(iff)); 243 244 // Clone the loop body. The clone becomes the fast loop. The 245 // original pre-header will (illegally) have 3 control users 246 // (old & new loops & new if). 247 clone_loop(loop, old_new, dom_depth(head), iff); 248 assert(old_new[head->_idx]->is_Loop(), "" ); 249 250 // Fast (true) control 251 Node* iffast_pred = clone_loop_predicates(entry, iffast, !counted_loop); 252 _igvn.hash_delete(head); 253 head->set_req(LoopNode::EntryControl, iffast_pred); 254 set_idom(head, iffast_pred, dom_depth(head)); 255 _igvn._worklist.push(head); 256 257 // Slow (false) control 258 Node* ifslow_pred = move_loop_predicates(entry, ifslow, !counted_loop); 259 LoopNode* slow_head = old_new[head->_idx]->as_Loop(); 260 _igvn.hash_delete(slow_head); 261 slow_head->set_req(LoopNode::EntryControl, ifslow_pred); 262 set_idom(slow_head, ifslow_pred, dom_depth(slow_head)); 263 _igvn._worklist.push(slow_head); 264 265 recompute_dom_depth(); 266 267 return iffast; 268 }