Mercurial > hg > truffle
annotate src/share/vm/opto/loopUnswitch.cpp @ 17541:4aa6fa2864af
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author | asaha |
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date | Thu, 23 Jan 2014 14:50:08 -0800 |
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0 | 1 /* |
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2 * Copyright (c) 2006, 2012, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 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" | |
0 | 30 |
31 //================= Loop Unswitching ===================== | |
32 // | |
33 // orig: transformed: | |
34 // if (invariant-test) then | |
2445 | 35 // predicate predicate |
0 | 36 // loop loop |
37 // stmt1 stmt1 | |
38 // if (invariant-test) then stmt2 | |
39 // stmt2 stmt4 | |
40 // else endloop | |
41 // stmt3 else | |
2445 | 42 // endif predicate [clone] |
43 // stmt4 loop [clone] | |
44 // endloop stmt1 [clone] | |
45 // stmt3 | |
0 | 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 } | |
108 | 59 if (!_head->is_Loop()) { |
60 return false; | |
61 } | |
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62 uint nodes_left = MaxNodeLimit - phase->C->live_nodes(); |
0 | 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 | |
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115 #ifndef PRODUCT |
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116 if (TraceLoopOpts) { |
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117 tty->print("Unswitch %d ", head->unswitch_count()+1); |
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118 loop->dump_head(); |
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119 } |
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120 #endif |
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121 |
0 | 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 | |
2445 | 129 #ifdef ASSERT |
130 Node* uniqc = proj_true->unique_ctrl_out(); | |
131 Node* entry = head->in(LoopNode::EntryControl); | |
132 Node* predicate = find_predicate(entry); | |
3345 | 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 } | |
2445 | 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 | |
0 | 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 | |
605 | 158 // Hoist invariant casts out of each loop to the appropriate |
0 | 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); | |
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177 _igvn.replace_input_of(use, 1, nuse); |
0 | 178 register_new_node(nuse, invar_proj); |
179 // Same for the clone | |
180 Node* use_clone = old_new[use->_idx]; | |
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181 _igvn.replace_input_of(use_clone, 1, nuse); |
0 | 182 } |
183 } | |
184 | |
185 // Hardwire the control paths in the loops into if(true) and if(false) | |
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186 _igvn.rehash_node_delayed(unswitch_iff); |
0 | 187 short_circuit_if(unswitch_iff, proj_true); |
188 | |
189 IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If(); | |
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190 _igvn.rehash_node_delayed(unswitch_iff_clone); |
0 | 191 short_circuit_if(unswitch_iff_clone, proj_false); |
192 | |
193 // Reoptimize loops | |
194 loop->record_for_igvn(); | |
195 for(int i = loop->_body.size() - 1; i >= 0 ; i--) { | |
196 Node *n = loop->_body[i]; | |
197 Node *n_clone = old_new[n->_idx]; | |
198 _igvn._worklist.push(n_clone); | |
199 } | |
200 | |
201 #ifndef PRODUCT | |
202 if (TraceLoopUnswitching) { | |
203 tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d", | |
204 head->_idx, unswitch_iff->_idx, | |
205 old_new[head->_idx]->_idx, unswitch_iff_clone->_idx); | |
206 } | |
207 #endif | |
208 | |
209 C->set_major_progress(); | |
210 } | |
211 | |
212 //-------------------------create_slow_version_of_loop------------------------ | |
213 // Create a slow version of the loop by cloning the loop | |
214 // and inserting an if to select fast-slow versions. | |
215 // Return control projection of the entry to the fast version. | |
216 ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop, | |
217 Node_List &old_new) { | |
218 LoopNode* head = loop->_head->as_Loop(); | |
3345 | 219 bool counted_loop = head->is_CountedLoop(); |
0 | 220 Node* entry = head->in(LoopNode::EntryControl); |
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221 _igvn.rehash_node_delayed(entry); |
0 | 222 IdealLoopTree* outer_loop = loop->_parent; |
223 | |
224 Node *cont = _igvn.intcon(1); | |
225 set_ctrl(cont, C->root()); | |
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226 Node* opq = new (C) Opaque1Node(C, cont); |
0 | 227 register_node(opq, outer_loop, entry, dom_depth(entry)); |
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228 Node *bol = new (C) Conv2BNode(opq); |
0 | 229 register_node(bol, outer_loop, entry, dom_depth(entry)); |
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230 IfNode* iff = new (C) IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN); |
0 | 231 register_node(iff, outer_loop, entry, dom_depth(entry)); |
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232 ProjNode* iffast = new (C) IfTrueNode(iff); |
0 | 233 register_node(iffast, outer_loop, iff, dom_depth(iff)); |
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234 ProjNode* ifslow = new (C) IfFalseNode(iff); |
0 | 235 register_node(ifslow, outer_loop, iff, dom_depth(iff)); |
236 | |
237 // Clone the loop body. The clone becomes the fast loop. The | |
2445 | 238 // original pre-header will (illegally) have 3 control users |
239 // (old & new loops & new if). | |
0 | 240 clone_loop(loop, old_new, dom_depth(head), iff); |
241 assert(old_new[head->_idx]->is_Loop(), "" ); | |
242 | |
243 // Fast (true) control | |
3345 | 244 Node* iffast_pred = clone_loop_predicates(entry, iffast, !counted_loop); |
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245 _igvn.replace_input_of(head, LoopNode::EntryControl, iffast_pred); |
2445 | 246 set_idom(head, iffast_pred, dom_depth(head)); |
0 | 247 |
248 // Slow (false) control | |
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249 Node* ifslow_pred = clone_loop_predicates(entry, ifslow, !counted_loop); |
0 | 250 LoopNode* slow_head = old_new[head->_idx]->as_Loop(); |
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251 _igvn.replace_input_of(slow_head, LoopNode::EntryControl, ifslow_pred); |
2445 | 252 set_idom(slow_head, ifslow_pred, dom_depth(slow_head)); |
0 | 253 |
254 recompute_dom_depth(); | |
255 | |
256 return iffast; | |
257 } |