1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/opto/loopUnswitch.cpp Sat Dec 01 00:00:00 2007 +0000
1.3 @@ -0,0 +1,237 @@
1.4 +/*
1.5 + * Copyright 2006 Sun Microsystems, Inc. All Rights Reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
1.23 + * CA 95054 USA or visit www.sun.com if you need additional information or
1.24 + * have any questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#include "incls/_precompiled.incl"
1.29 +#include "incls/_loopUnswitch.cpp.incl"
1.30 +
1.31 +//================= Loop Unswitching =====================
1.32 +//
1.33 +// orig: transformed:
1.34 +// if (invariant-test) then
1.35 +// loop loop
1.36 +// stmt1 stmt1
1.37 +// if (invariant-test) then stmt2
1.38 +// stmt2 stmt4
1.39 +// else endloop
1.40 +// stmt3 else
1.41 +// endif loop [clone]
1.42 +// stmt4 stmt1 [clone]
1.43 +// endloop stmt3
1.44 +// stmt4 [clone]
1.45 +// endloop
1.46 +// endif
1.47 +//
1.48 +// Note: the "else" clause may be empty
1.49 +
1.50 +//------------------------------policy_unswitching-----------------------------
1.51 +// Return TRUE or FALSE if the loop should be unswitched
1.52 +// (ie. clone loop with an invariant test that does not exit the loop)
1.53 +bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const {
1.54 + if( !LoopUnswitching ) {
1.55 + return false;
1.56 + }
1.57 + uint nodes_left = MaxNodeLimit - phase->C->unique();
1.58 + if (2 * _body.size() > nodes_left) {
1.59 + return false; // Too speculative if running low on nodes.
1.60 + }
1.61 + LoopNode* head = _head->as_Loop();
1.62 + if (head->unswitch_count() + 1 > head->unswitch_max()) {
1.63 + return false;
1.64 + }
1.65 + return phase->find_unswitching_candidate(this) != NULL;
1.66 +}
1.67 +
1.68 +//------------------------------find_unswitching_candidate-----------------------------
1.69 +// Find candidate "if" for unswitching
1.70 +IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const {
1.71 +
1.72 + // Find first invariant test that doesn't exit the loop
1.73 + LoopNode *head = loop->_head->as_Loop();
1.74 + IfNode* unswitch_iff = NULL;
1.75 + Node* n = head->in(LoopNode::LoopBackControl);
1.76 + while (n != head) {
1.77 + Node* n_dom = idom(n);
1.78 + if (n->is_Region()) {
1.79 + if (n_dom->is_If()) {
1.80 + IfNode* iff = n_dom->as_If();
1.81 + if (iff->in(1)->is_Bool()) {
1.82 + BoolNode* bol = iff->in(1)->as_Bool();
1.83 + if (bol->in(1)->is_Cmp()) {
1.84 + // If condition is invariant and not a loop exit,
1.85 + // then found reason to unswitch.
1.86 + if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) {
1.87 + unswitch_iff = iff;
1.88 + }
1.89 + }
1.90 + }
1.91 + }
1.92 + }
1.93 + n = n_dom;
1.94 + }
1.95 + return unswitch_iff;
1.96 +}
1.97 +
1.98 +//------------------------------do_unswitching-----------------------------
1.99 +// Clone loop with an invariant test (that does not exit) and
1.100 +// insert a clone of the test that selects which version to
1.101 +// execute.
1.102 +void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) {
1.103 +
1.104 + // Find first invariant test that doesn't exit the loop
1.105 + LoopNode *head = loop->_head->as_Loop();
1.106 +
1.107 + IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop);
1.108 + assert(unswitch_iff != NULL, "should be at least one");
1.109 +
1.110 + // Need to revert back to normal loop
1.111 + if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) {
1.112 + head->as_CountedLoop()->set_normal_loop();
1.113 + }
1.114 +
1.115 + ProjNode* proj_true = create_slow_version_of_loop(loop, old_new);
1.116 +
1.117 + assert(proj_true->is_IfTrue() && proj_true->unique_ctrl_out() == head, "by construction");
1.118 +
1.119 + // Increment unswitch count
1.120 + LoopNode* head_clone = old_new[head->_idx]->as_Loop();
1.121 + int nct = head->unswitch_count() + 1;
1.122 + head->set_unswitch_count(nct);
1.123 + head_clone->set_unswitch_count(nct);
1.124 +
1.125 + // Add test to new "if" outside of loop
1.126 + IfNode* invar_iff = proj_true->in(0)->as_If();
1.127 + Node* invar_iff_c = invar_iff->in(0);
1.128 + BoolNode* bol = unswitch_iff->in(1)->as_Bool();
1.129 + invar_iff->set_req(1, bol);
1.130 + invar_iff->_prob = unswitch_iff->_prob;
1.131 +
1.132 + ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj();
1.133 +
1.134 + // Hoist invariant casts out of each loop to the appropiate
1.135 + // control projection.
1.136 +
1.137 + Node_List worklist;
1.138 +
1.139 + for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) {
1.140 + ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj();
1.141 + // Copy to a worklist for easier manipulation
1.142 + for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) {
1.143 + Node* use = proj->fast_out(j);
1.144 + if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) {
1.145 + worklist.push(use);
1.146 + }
1.147 + }
1.148 + ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj();
1.149 + while (worklist.size() > 0) {
1.150 + Node* use = worklist.pop();
1.151 + Node* nuse = use->clone();
1.152 + nuse->set_req(0, invar_proj);
1.153 + _igvn.hash_delete(use);
1.154 + use->set_req(1, nuse);
1.155 + _igvn._worklist.push(use);
1.156 + register_new_node(nuse, invar_proj);
1.157 + // Same for the clone
1.158 + Node* use_clone = old_new[use->_idx];
1.159 + _igvn.hash_delete(use_clone);
1.160 + use_clone->set_req(1, nuse);
1.161 + _igvn._worklist.push(use_clone);
1.162 + }
1.163 + }
1.164 +
1.165 + // Hardwire the control paths in the loops into if(true) and if(false)
1.166 + _igvn.hash_delete(unswitch_iff);
1.167 + short_circuit_if(unswitch_iff, proj_true);
1.168 + _igvn._worklist.push(unswitch_iff);
1.169 +
1.170 + IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If();
1.171 + _igvn.hash_delete(unswitch_iff_clone);
1.172 + short_circuit_if(unswitch_iff_clone, proj_false);
1.173 + _igvn._worklist.push(unswitch_iff_clone);
1.174 +
1.175 + // Reoptimize loops
1.176 + loop->record_for_igvn();
1.177 + for(int i = loop->_body.size() - 1; i >= 0 ; i--) {
1.178 + Node *n = loop->_body[i];
1.179 + Node *n_clone = old_new[n->_idx];
1.180 + _igvn._worklist.push(n_clone);
1.181 + }
1.182 +
1.183 +#ifndef PRODUCT
1.184 + if (TraceLoopUnswitching) {
1.185 + tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d",
1.186 + head->_idx, unswitch_iff->_idx,
1.187 + old_new[head->_idx]->_idx, unswitch_iff_clone->_idx);
1.188 + }
1.189 +#endif
1.190 +
1.191 + C->set_major_progress();
1.192 +}
1.193 +
1.194 +//-------------------------create_slow_version_of_loop------------------------
1.195 +// Create a slow version of the loop by cloning the loop
1.196 +// and inserting an if to select fast-slow versions.
1.197 +// Return control projection of the entry to the fast version.
1.198 +ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop,
1.199 + Node_List &old_new) {
1.200 + LoopNode* head = loop->_head->as_Loop();
1.201 + Node* entry = head->in(LoopNode::EntryControl);
1.202 + _igvn.hash_delete(entry);
1.203 + _igvn._worklist.push(entry);
1.204 + IdealLoopTree* outer_loop = loop->_parent;
1.205 +
1.206 + Node *cont = _igvn.intcon(1);
1.207 + set_ctrl(cont, C->root());
1.208 + Node* opq = new (C, 2) Opaque1Node(cont);
1.209 + register_node(opq, outer_loop, entry, dom_depth(entry));
1.210 + Node *bol = new (C, 2) Conv2BNode(opq);
1.211 + register_node(bol, outer_loop, entry, dom_depth(entry));
1.212 + IfNode* iff = new (C, 2) IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN);
1.213 + register_node(iff, outer_loop, entry, dom_depth(entry));
1.214 + ProjNode* iffast = new (C, 1) IfTrueNode(iff);
1.215 + register_node(iffast, outer_loop, iff, dom_depth(iff));
1.216 + ProjNode* ifslow = new (C, 1) IfFalseNode(iff);
1.217 + register_node(ifslow, outer_loop, iff, dom_depth(iff));
1.218 +
1.219 + // Clone the loop body. The clone becomes the fast loop. The
1.220 + // original pre-header will (illegally) have 2 control users (old & new loops).
1.221 + clone_loop(loop, old_new, dom_depth(head), iff);
1.222 + assert(old_new[head->_idx]->is_Loop(), "" );
1.223 +
1.224 + // Fast (true) control
1.225 + _igvn.hash_delete(head);
1.226 + head->set_req(LoopNode::EntryControl, iffast);
1.227 + set_idom(head, iffast, dom_depth(head));
1.228 + _igvn._worklist.push(head);
1.229 +
1.230 + // Slow (false) control
1.231 + LoopNode* slow_head = old_new[head->_idx]->as_Loop();
1.232 + _igvn.hash_delete(slow_head);
1.233 + slow_head->set_req(LoopNode::EntryControl, ifslow);
1.234 + set_idom(slow_head, ifslow, dom_depth(slow_head));
1.235 + _igvn._worklist.push(slow_head);
1.236 +
1.237 + recompute_dom_depth();
1.238 +
1.239 + return iffast;
1.240 +}
