Mercurial > hg > truffle
comparison src/share/vm/opto/loopUnswitch.cpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
parents | |
children | a761c2d3b76a |
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1 /* | |
2 * Copyright 2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any questions. | |
22 * | |
23 */ | |
24 | |
25 #include "incls/_precompiled.incl" | |
26 #include "incls/_loopUnswitch.cpp.incl" | |
27 | |
28 //================= Loop Unswitching ===================== | |
29 // | |
30 // orig: transformed: | |
31 // if (invariant-test) then | |
32 // loop loop | |
33 // stmt1 stmt1 | |
34 // if (invariant-test) then stmt2 | |
35 // stmt2 stmt4 | |
36 // else endloop | |
37 // stmt3 else | |
38 // endif loop [clone] | |
39 // stmt4 stmt1 [clone] | |
40 // endloop stmt3 | |
41 // stmt4 [clone] | |
42 // endloop | |
43 // endif | |
44 // | |
45 // Note: the "else" clause may be empty | |
46 | |
47 //------------------------------policy_unswitching----------------------------- | |
48 // Return TRUE or FALSE if the loop should be unswitched | |
49 // (ie. clone loop with an invariant test that does not exit the loop) | |
50 bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const { | |
51 if( !LoopUnswitching ) { | |
52 return false; | |
53 } | |
54 uint nodes_left = MaxNodeLimit - phase->C->unique(); | |
55 if (2 * _body.size() > nodes_left) { | |
56 return false; // Too speculative if running low on nodes. | |
57 } | |
58 LoopNode* head = _head->as_Loop(); | |
59 if (head->unswitch_count() + 1 > head->unswitch_max()) { | |
60 return false; | |
61 } | |
62 return phase->find_unswitching_candidate(this) != NULL; | |
63 } | |
64 | |
65 //------------------------------find_unswitching_candidate----------------------------- | |
66 // Find candidate "if" for unswitching | |
67 IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const { | |
68 | |
69 // Find first invariant test that doesn't exit the loop | |
70 LoopNode *head = loop->_head->as_Loop(); | |
71 IfNode* unswitch_iff = NULL; | |
72 Node* n = head->in(LoopNode::LoopBackControl); | |
73 while (n != head) { | |
74 Node* n_dom = idom(n); | |
75 if (n->is_Region()) { | |
76 if (n_dom->is_If()) { | |
77 IfNode* iff = n_dom->as_If(); | |
78 if (iff->in(1)->is_Bool()) { | |
79 BoolNode* bol = iff->in(1)->as_Bool(); | |
80 if (bol->in(1)->is_Cmp()) { | |
81 // If condition is invariant and not a loop exit, | |
82 // then found reason to unswitch. | |
83 if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) { | |
84 unswitch_iff = iff; | |
85 } | |
86 } | |
87 } | |
88 } | |
89 } | |
90 n = n_dom; | |
91 } | |
92 return unswitch_iff; | |
93 } | |
94 | |
95 //------------------------------do_unswitching----------------------------- | |
96 // Clone loop with an invariant test (that does not exit) and | |
97 // insert a clone of the test that selects which version to | |
98 // execute. | |
99 void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) { | |
100 | |
101 // Find first invariant test that doesn't exit the loop | |
102 LoopNode *head = loop->_head->as_Loop(); | |
103 | |
104 IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop); | |
105 assert(unswitch_iff != NULL, "should be at least one"); | |
106 | |
107 // Need to revert back to normal loop | |
108 if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) { | |
109 head->as_CountedLoop()->set_normal_loop(); | |
110 } | |
111 | |
112 ProjNode* proj_true = create_slow_version_of_loop(loop, old_new); | |
113 | |
114 assert(proj_true->is_IfTrue() && proj_true->unique_ctrl_out() == head, "by construction"); | |
115 | |
116 // Increment unswitch count | |
117 LoopNode* head_clone = old_new[head->_idx]->as_Loop(); | |
118 int nct = head->unswitch_count() + 1; | |
119 head->set_unswitch_count(nct); | |
120 head_clone->set_unswitch_count(nct); | |
121 | |
122 // Add test to new "if" outside of loop | |
123 IfNode* invar_iff = proj_true->in(0)->as_If(); | |
124 Node* invar_iff_c = invar_iff->in(0); | |
125 BoolNode* bol = unswitch_iff->in(1)->as_Bool(); | |
126 invar_iff->set_req(1, bol); | |
127 invar_iff->_prob = unswitch_iff->_prob; | |
128 | |
129 ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj(); | |
130 | |
131 // Hoist invariant casts out of each loop to the appropiate | |
132 // control projection. | |
133 | |
134 Node_List worklist; | |
135 | |
136 for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) { | |
137 ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj(); | |
138 // Copy to a worklist for easier manipulation | |
139 for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) { | |
140 Node* use = proj->fast_out(j); | |
141 if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) { | |
142 worklist.push(use); | |
143 } | |
144 } | |
145 ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj(); | |
146 while (worklist.size() > 0) { | |
147 Node* use = worklist.pop(); | |
148 Node* nuse = use->clone(); | |
149 nuse->set_req(0, invar_proj); | |
150 _igvn.hash_delete(use); | |
151 use->set_req(1, nuse); | |
152 _igvn._worklist.push(use); | |
153 register_new_node(nuse, invar_proj); | |
154 // Same for the clone | |
155 Node* use_clone = old_new[use->_idx]; | |
156 _igvn.hash_delete(use_clone); | |
157 use_clone->set_req(1, nuse); | |
158 _igvn._worklist.push(use_clone); | |
159 } | |
160 } | |
161 | |
162 // Hardwire the control paths in the loops into if(true) and if(false) | |
163 _igvn.hash_delete(unswitch_iff); | |
164 short_circuit_if(unswitch_iff, proj_true); | |
165 _igvn._worklist.push(unswitch_iff); | |
166 | |
167 IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If(); | |
168 _igvn.hash_delete(unswitch_iff_clone); | |
169 short_circuit_if(unswitch_iff_clone, proj_false); | |
170 _igvn._worklist.push(unswitch_iff_clone); | |
171 | |
172 // Reoptimize loops | |
173 loop->record_for_igvn(); | |
174 for(int i = loop->_body.size() - 1; i >= 0 ; i--) { | |
175 Node *n = loop->_body[i]; | |
176 Node *n_clone = old_new[n->_idx]; | |
177 _igvn._worklist.push(n_clone); | |
178 } | |
179 | |
180 #ifndef PRODUCT | |
181 if (TraceLoopUnswitching) { | |
182 tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d", | |
183 head->_idx, unswitch_iff->_idx, | |
184 old_new[head->_idx]->_idx, unswitch_iff_clone->_idx); | |
185 } | |
186 #endif | |
187 | |
188 C->set_major_progress(); | |
189 } | |
190 | |
191 //-------------------------create_slow_version_of_loop------------------------ | |
192 // Create a slow version of the loop by cloning the loop | |
193 // and inserting an if to select fast-slow versions. | |
194 // Return control projection of the entry to the fast version. | |
195 ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop, | |
196 Node_List &old_new) { | |
197 LoopNode* head = loop->_head->as_Loop(); | |
198 Node* entry = head->in(LoopNode::EntryControl); | |
199 _igvn.hash_delete(entry); | |
200 _igvn._worklist.push(entry); | |
201 IdealLoopTree* outer_loop = loop->_parent; | |
202 | |
203 Node *cont = _igvn.intcon(1); | |
204 set_ctrl(cont, C->root()); | |
205 Node* opq = new (C, 2) Opaque1Node(cont); | |
206 register_node(opq, outer_loop, entry, dom_depth(entry)); | |
207 Node *bol = new (C, 2) Conv2BNode(opq); | |
208 register_node(bol, outer_loop, entry, dom_depth(entry)); | |
209 IfNode* iff = new (C, 2) IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN); | |
210 register_node(iff, outer_loop, entry, dom_depth(entry)); | |
211 ProjNode* iffast = new (C, 1) IfTrueNode(iff); | |
212 register_node(iffast, outer_loop, iff, dom_depth(iff)); | |
213 ProjNode* ifslow = new (C, 1) IfFalseNode(iff); | |
214 register_node(ifslow, outer_loop, iff, dom_depth(iff)); | |
215 | |
216 // Clone the loop body. The clone becomes the fast loop. The | |
217 // original pre-header will (illegally) have 2 control users (old & new loops). | |
218 clone_loop(loop, old_new, dom_depth(head), iff); | |
219 assert(old_new[head->_idx]->is_Loop(), "" ); | |
220 | |
221 // Fast (true) control | |
222 _igvn.hash_delete(head); | |
223 head->set_req(LoopNode::EntryControl, iffast); | |
224 set_idom(head, iffast, dom_depth(head)); | |
225 _igvn._worklist.push(head); | |
226 | |
227 // Slow (false) control | |
228 LoopNode* slow_head = old_new[head->_idx]->as_Loop(); | |
229 _igvn.hash_delete(slow_head); | |
230 slow_head->set_req(LoopNode::EntryControl, ifslow); | |
231 set_idom(slow_head, ifslow, dom_depth(slow_head)); | |
232 _igvn._worklist.push(slow_head); | |
233 | |
234 recompute_dom_depth(); | |
235 | |
236 return iffast; | |
237 } |