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1 /*
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2 * Copyright 1999-2006 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 #include "incls/_precompiled.incl"
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26 #include "incls/_split_if.cpp.incl"
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27
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28
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29 //------------------------------split_thru_region------------------------------
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30 // Split Node 'n' through merge point.
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31 Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) {
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32 uint wins = 0;
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33 assert( n->is_CFG(), "" );
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34 assert( region->is_Region(), "" );
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35 Node *r = new (C, region->req()) RegionNode( region->req() );
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36 IdealLoopTree *loop = get_loop( n );
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37 for( uint i = 1; i < region->req(); i++ ) {
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38 Node *x = n->clone();
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39 Node *in0 = n->in(0);
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40 if( in0->in(0) == region ) x->set_req( 0, in0->in(i) );
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41 for( uint j = 1; j < n->req(); j++ ) {
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42 Node *in = n->in(j);
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43 if( get_ctrl(in) == region )
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44 x->set_req( j, in->in(i) );
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45 }
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46 _igvn.register_new_node_with_optimizer(x);
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47 set_loop(x, loop);
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48 set_idom(x, x->in(0), dom_depth(x->in(0))+1);
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49 r->init_req(i, x);
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50 }
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51
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52 // Record region
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53 r->set_req(0,region); // Not a TRUE RegionNode
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54 _igvn.register_new_node_with_optimizer(r);
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55 set_loop(r, loop);
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56 if( !loop->_child )
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57 loop->_body.push(r);
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58 return r;
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59 }
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60
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61 //------------------------------split_up---------------------------------------
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62 // Split block-local op up through the phis to empty the current block
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63 bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
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64 if( n->is_CFG() ) {
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65 assert( n->in(0) != blk1, "Lousy candidate for split-if" );
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66 return false;
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67 }
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68 if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 )
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69 return false; // Not block local
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70 if( n->is_Phi() ) return false; // Local PHIs are expected
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71
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72 // Recursively split-up inputs
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73 for (uint i = 1; i < n->req(); i++) {
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74 if( split_up( n->in(i), blk1, blk2 ) ) {
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75 // Got split recursively and self went dead?
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76 if (n->outcnt() == 0)
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77 _igvn.remove_dead_node(n);
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78 return true;
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79 }
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80 }
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81
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82 // Check for needing to clone-up a compare. Can't do that, it forces
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83 // another (nested) split-if transform. Instead, clone it "down".
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84 if( n->is_Cmp() ) {
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85 assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
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86 // Check for simple Cmp/Bool/CMove which we can clone-up. Cmp/Bool/CMove
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87 // sequence can have no other users and it must all reside in the split-if
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88 // block. Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
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89 // private, per-use versions of the Cmp and Bool are made. These sink to
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90 // the CMove block. If the CMove is in the split-if block, then in the
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91 // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
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92 Node *bol, *cmov;
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93 if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
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94 (bol = n->unique_out()->as_Bool()) &&
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95 (get_ctrl(bol) == blk1 ||
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96 get_ctrl(bol) == blk2) &&
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97 bol->outcnt() == 1 &&
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98 bol->unique_out()->is_CMove() &&
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99 (cmov = bol->unique_out()->as_CMove()) &&
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100 (get_ctrl(cmov) == blk1 ||
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101 get_ctrl(cmov) == blk2) ) ) {
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102
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103 // Must clone down
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104 #ifndef PRODUCT
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105 if( PrintOpto && VerifyLoopOptimizations ) {
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106 tty->print("Cloning down: ");
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107 n->dump();
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108 }
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109 #endif
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110 // Clone down any block-local BoolNode uses of this CmpNode
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111 for (DUIterator i = n->outs(); n->has_out(i); i++) {
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112 Node* bol = n->out(i);
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113 assert( bol->is_Bool(), "" );
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114 if (bol->outcnt() == 1) {
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115 Node* use = bol->unique_out();
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116 Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use);
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117 if (use_c == blk1 || use_c == blk2) {
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118 continue;
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119 }
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120 }
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121 if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) {
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122 // Recursively sink any BoolNode
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123 #ifndef PRODUCT
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124 if( PrintOpto && VerifyLoopOptimizations ) {
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125 tty->print("Cloning down: ");
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126 bol->dump();
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127 }
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128 #endif
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129 for (DUIterator_Last jmin, j = bol->last_outs(jmin); j >= jmin; --j) {
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130 // Uses are either IfNodes or CMoves
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131 Node* iff = bol->last_out(j);
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132 assert( iff->in(1) == bol, "" );
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133 // Get control block of either the CMove or the If input
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134 Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
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135 Node *x = bol->clone();
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136 register_new_node(x, iff_ctrl);
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137 _igvn.hash_delete(iff);
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138 iff->set_req(1, x);
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139 _igvn._worklist.push(iff);
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140 }
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141 _igvn.remove_dead_node( bol );
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142 --i;
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143 }
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144 }
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145 // Clone down this CmpNode
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146 for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
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147 Node* bol = n->last_out(j);
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148 assert( bol->in(1) == n, "" );
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149 Node *x = n->clone();
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150 register_new_node(x, get_ctrl(bol));
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151 _igvn.hash_delete(bol);
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152 bol->set_req(1, x);
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153 _igvn._worklist.push(bol);
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154 }
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155 _igvn.remove_dead_node( n );
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156
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157 return true;
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158 }
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159 }
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160
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161 // See if splitting-up a Store. Any anti-dep loads must go up as
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162 // well. An anti-dep load might be in the wrong block, because in
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163 // this particular layout/schedule we ignored anti-deps and allow
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164 // memory to be alive twice. This only works if we do the same
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165 // operations on anti-dep loads as we do their killing stores.
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166 if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
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167 // Get store's memory slice
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168 int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
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169
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170 // Get memory-phi anti-dep loads will be using
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171 Node *memphi = n->in(MemNode::Memory);
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172 assert( memphi->is_Phi(), "" );
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173 // Hoist any anti-dep load to the splitting block;
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174 // it will then "split-up".
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175 for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
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176 Node *load = memphi->fast_out(i);
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177 if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
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178 set_ctrl(load,blk1);
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179 }
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180 }
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181
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182 // Found some other Node; must clone it up
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183 #ifndef PRODUCT
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184 if( PrintOpto && VerifyLoopOptimizations ) {
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185 tty->print("Cloning up: ");
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186 n->dump();
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187 }
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188 #endif
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189
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190 // Now actually split-up this guy. One copy per control path merging.
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191 Node *phi = PhiNode::make_blank(blk1, n);
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192 for( uint j = 1; j < blk1->req(); j++ ) {
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193 Node *x = n->clone();
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194 if( n->in(0) && n->in(0) == blk1 )
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195 x->set_req( 0, blk1->in(j) );
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196 for( uint i = 1; i < n->req(); i++ ) {
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197 Node *m = n->in(i);
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198 if( get_ctrl(m) == blk1 ) {
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199 assert( m->in(0) == blk1, "" );
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200 x->set_req( i, m->in(j) );
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201 }
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202 }
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203 register_new_node( x, blk1->in(j) );
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204 phi->init_req( j, x );
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205 }
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206 // Announce phi to optimizer
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207 register_new_node(phi, blk1);
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208
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209 // Remove cloned-up value from optimizer; use phi instead
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210 _igvn.hash_delete(n);
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211 _igvn.subsume_node( n, phi );
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212
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213 // (There used to be a self-recursive call to split_up() here,
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214 // but it is not needed. All necessary forward walking is done
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215 // by do_split_if() below.)
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216
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217 return true;
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218 }
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219
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220 //------------------------------register_new_node------------------------------
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221 void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
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222 _igvn.register_new_node_with_optimizer(n);
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223 set_ctrl(n, blk);
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224 IdealLoopTree *loop = get_loop(blk);
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225 if( !loop->_child )
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226 loop->_body.push(n);
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227 }
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228
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229 //------------------------------small_cache------------------------------------
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230 struct small_cache : public Dict {
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231
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232 small_cache() : Dict( cmpkey, hashptr ) {}
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233 Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
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234 void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
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235 };
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236
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237 //------------------------------spinup-----------------------------------------
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238 // "Spin up" the dominator tree, starting at the use site and stopping when we
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239 // find the post-dominating point.
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240
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241 // We must be at the merge point which post-dominates 'new_false' and
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242 // 'new_true'. Figure out which edges into the RegionNode eventually lead up
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243 // to false and which to true. Put in a PhiNode to merge values; plug in
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244 // the appropriate false-arm or true-arm values. If some path leads to the
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245 // original IF, then insert a Phi recursively.
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246 Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
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247 if (use_blk->is_top()) // Handle dead uses
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248 return use_blk;
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249 Node *prior_n = (Node*)0xdeadbeef;
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250 Node *n = use_blk; // Get path input
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251 assert( use_blk != iff_dom, "" );
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252 // Here's the "spinup" the dominator tree loop. Do a cache-check
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253 // along the way, in case we've come this way before.
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254 while( n != iff_dom ) { // Found post-dominating point?
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255 prior_n = n;
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256 n = idom(n); // Search higher
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257 Node *s = cache->probe( prior_n ); // Check cache
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258 if( s ) return s; // Cache hit!
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259 }
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260
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261 Node *phi_post;
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262 if( prior_n == new_false || prior_n == new_true ) {
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263 phi_post = def->clone();
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264 phi_post->set_req(0, prior_n );
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265 register_new_node(phi_post, prior_n);
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266 } else {
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267 // This method handles both control uses (looking for Regions) or data
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268 // uses (looking for Phis). If looking for a control use, then we need
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269 // to insert a Region instead of a Phi; however Regions always exist
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270 // previously (the hash_find_insert below would always hit) so we can
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271 // return the existing Region.
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272 if( def->is_CFG() ) {
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273 phi_post = prior_n; // If looking for CFG, return prior
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274 } else {
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275 assert( def->is_Phi(), "" );
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276 assert( prior_n->is_Region(), "must be a post-dominating merge point" );
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277
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278 // Need a Phi here
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279 phi_post = PhiNode::make_blank(prior_n, def);
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280 // Search for both true and false on all paths till find one.
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281 for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
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282 phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
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283 Node *t = _igvn.hash_find_insert(phi_post);
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284 if( t ) { // See if we already have this one
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285 // phi_post will not be used, so kill it
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286 _igvn.remove_dead_node(phi_post);
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287 phi_post->destruct();
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288 phi_post = t;
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289 } else {
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290 register_new_node( phi_post, prior_n );
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291 }
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292 }
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293 }
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294
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295 // Update cache everywhere
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296 prior_n = (Node*)0xdeadbeef; // Reset IDOM walk
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297 n = use_blk; // Get path input
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298 // Spin-up the idom tree again, basically doing path-compression.
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299 // Insert cache entries along the way, so that if we ever hit this
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300 // point in the IDOM tree again we'll stop immediately on a cache hit.
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301 while( n != iff_dom ) { // Found post-dominating point?
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302 prior_n = n;
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303 n = idom(n); // Search higher
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304 cache->lru_insert( prior_n, phi_post ); // Fill cache
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305 } // End of while not gone high enough
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306
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307 return phi_post;
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308 }
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309
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310 //------------------------------find_use_block---------------------------------
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311 // Find the block a USE is in. Normally USE's are in the same block as the
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312 // using instruction. For Phi-USE's, the USE is in the predecessor block
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313 // along the corresponding path.
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314 Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
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315 // CFG uses are their own block
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316 if( use->is_CFG() )
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317 return use;
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318
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319 if( use->is_Phi() ) { // Phi uses in prior block
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320 // Grab the first Phi use; there may be many.
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321 // Each will be handled as a seperate iteration of
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322 // the "while( phi->outcnt() )" loop.
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323 uint j;
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324 for( j = 1; j < use->req(); j++ )
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325 if( use->in(j) == def )
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326 break;
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327 assert( j < use->req(), "def should be among use's inputs" );
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328 return use->in(0)->in(j);
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329 }
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330 // Normal (non-phi) use
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331 Node *use_blk = get_ctrl(use);
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332 // Some uses are directly attached to the old (and going away)
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333 // false and true branches.
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334 if( use_blk == old_false ) {
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335 use_blk = new_false;
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336 set_ctrl(use, new_false);
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337 }
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338 if( use_blk == old_true ) {
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339 use_blk = new_true;
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340 set_ctrl(use, new_true);
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341 }
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342
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343 if (use_blk == NULL) { // He's dead, Jim
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344 _igvn.hash_delete(use);
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345 _igvn.subsume_node(use, C->top());
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346 }
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347
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348 return use_blk;
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349 }
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350
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351 //------------------------------handle_use-------------------------------------
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352 // Handle uses of the merge point. Basically, split-if makes the merge point
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353 // go away so all uses of the merge point must go away as well. Most block
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354 // local uses have already been split-up, through the merge point. Uses from
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355 // far below the merge point can't always be split up (e.g., phi-uses are
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356 // pinned) and it makes too much stuff live. Instead we use a path-based
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357 // solution to move uses down.
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358 //
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359 // If the use is along the pre-split-CFG true branch, then the new use will
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360 // be from the post-split-CFG true merge point. Vice-versa for the false
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361 // path. Some uses will be along both paths; then we sink the use to the
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362 // post-dominating location; we may need to insert a Phi there.
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363 void PhaseIdealLoop::handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true ) {
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364
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365 Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
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366 if( !use_blk ) return; // He's dead, Jim
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367
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368 // Walk up the dominator tree until I hit either the old IfFalse, the old
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369 // IfTrue or the old If. Insert Phis where needed.
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370 Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
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371
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372 // Found where this USE goes. Re-point him.
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373 uint i;
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374 for( i = 0; i < use->req(); i++ )
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375 if( use->in(i) == def )
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376 break;
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377 assert( i < use->req(), "def should be among use's inputs" );
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378 _igvn.hash_delete(use);
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379 use->set_req(i, new_def);
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380 _igvn._worklist.push(use);
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381 }
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382
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383 //------------------------------do_split_if------------------------------------
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384 // Found an If getting its condition-code input from a Phi in the same block.
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385 // Split thru the Region.
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386 void PhaseIdealLoop::do_split_if( Node *iff ) {
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387 #ifndef PRODUCT
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388 if( PrintOpto && VerifyLoopOptimizations )
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389 tty->print_cr("Split-if");
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390 #endif
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391 C->set_major_progress();
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392 Node *region = iff->in(0);
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393 Node *region_dom = idom(region);
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394
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395 // We are going to clone this test (and the control flow with it) up through
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396 // the incoming merge point. We need to empty the current basic block.
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397 // Clone any instructions which must be in this block up through the merge
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398 // point.
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399 DUIterator i, j;
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400 bool progress = true;
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401 while (progress) {
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402 progress = false;
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403 for (i = region->outs(); region->has_out(i); i++) {
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404 Node* n = region->out(i);
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405 if( n == region ) continue;
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406 // The IF to be split is OK.
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407 if( n == iff ) continue;
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408 if( !n->is_Phi() ) { // Found pinned memory op or such
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409 if (split_up(n, region, iff)) {
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410 i = region->refresh_out_pos(i);
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411 progress = true;
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412 }
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413 continue;
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414 }
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415 assert( n->in(0) == region, "" );
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416
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417 // Recursively split up all users of a Phi
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418 for (j = n->outs(); n->has_out(j); j++) {
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419 Node* m = n->out(j);
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420 // If m is dead, throw it away, and declare progress
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421 if (_nodes[m->_idx] == NULL) {
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422 _igvn.remove_dead_node(m);
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423 // fall through
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424 }
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425 else if (m != iff && split_up(m, region, iff)) {
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426 // fall through
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427 } else {
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428 continue;
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429 }
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430 // Something unpredictable changed.
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431 // Tell the iterators to refresh themselves, and rerun the loop.
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432 i = region->refresh_out_pos(i);
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433 j = region->refresh_out_pos(j);
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434 progress = true;
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435 }
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436 }
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437 }
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438
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439 // Now we have no instructions in the block containing the IF.
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440 // Split the IF.
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441 Node *new_iff = split_thru_region( iff, region );
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442
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443 // Replace both uses of 'new_iff' with Regions merging True/False
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444 // paths. This makes 'new_iff' go dead.
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445 Node *old_false, *old_true;
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446 Node *new_false, *new_true;
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447 for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
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448 Node *ifp = iff->last_out(j2);
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449 assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
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450 ifp->set_req(0, new_iff);
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451 Node *ifpx = split_thru_region( ifp, region );
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452
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453 // Replace 'If' projection of a Region with a Region of
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454 // 'If' projections.
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455 ifpx->set_req(0, ifpx); // A TRUE RegionNode
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456
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457 // Setup dominator info
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458 set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
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459
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460 // Check for splitting loop tails
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461 if( get_loop(iff)->tail() == ifp )
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462 get_loop(iff)->_tail = ifpx;
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463
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464 // Replace in the graph with lazy-update mechanism
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465 new_iff->set_req(0, new_iff); // hook self so it does not go dead
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466 lazy_replace_proj( ifp, ifpx );
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467 new_iff->set_req(0, region);
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468
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469 // Record bits for later xforms
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470 if( ifp->Opcode() == Op_IfFalse ) {
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471 old_false = ifp;
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472 new_false = ifpx;
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473 } else {
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474 old_true = ifp;
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475 new_true = ifpx;
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476 }
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477 }
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478 _igvn.remove_dead_node(new_iff);
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479 // Lazy replace IDOM info with the region's dominator
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480 lazy_replace( iff, region_dom );
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481
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482 // Now make the original merge point go dead, by handling all its uses.
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483 small_cache region_cache;
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484 // Preload some control flow in region-cache
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485 region_cache.lru_insert( new_false, new_false );
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486 region_cache.lru_insert( new_true , new_true );
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487 // Now handle all uses of the splitting block
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488 for (DUIterator_Last kmin, k = region->last_outs(kmin); k >= kmin; --k) {
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489 Node* phi = region->last_out(k);
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490 if( !phi->in(0) ) { // Dead phi? Remove it
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491 _igvn.remove_dead_node(phi);
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492 continue;
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493 }
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494 assert( phi->in(0) == region, "" );
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495 if( phi == region ) { // Found the self-reference
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496 phi->set_req(0, NULL);
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497 continue; // Break the self-cycle
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498 }
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499 // Expected common case: Phi hanging off of Region
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500 if( phi->is_Phi() ) {
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501 // Need a per-def cache. Phi represents a def, so make a cache
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502 small_cache phi_cache;
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503
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504 // Inspect all Phi uses to make the Phi go dead
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505 for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
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506 Node* use = phi->last_out(l);
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507 // Compute the new DEF for this USE. New DEF depends on the path
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508 // taken from the original DEF to the USE. The new DEF may be some
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509 // collection of PHI's merging values from different paths. The Phis
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510 // inserted depend only on the location of the USE. We use a
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511 // 2-element cache to handle multiple uses from the same block.
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512 handle_use( use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true );
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513 } // End of while phi has uses
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514
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515 // Because handle_use might relocate region->_out,
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516 // we must refresh the iterator.
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517 k = region->last_outs(kmin);
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518
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519 // Remove the dead Phi
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520 _igvn.remove_dead_node( phi );
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521
|
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522 } else {
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523 // Random memory op guarded by Region. Compute new DEF for USE.
|
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524 handle_use( phi, region, ®ion_cache, region_dom, new_false, new_true, old_false, old_true );
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|
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525 }
|
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526
|
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527 } // End of while merge point has phis
|
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528
|
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529 // Any leftover bits in the splitting block must not have depended on local
|
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530 // Phi inputs (these have already been split-up). Hence it's safe to hoist
|
|
|
531 // these guys to the dominating point.
|
|
|
532 lazy_replace( region, region_dom );
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|
|
533 #ifndef PRODUCT
|
|
|
534 if( VerifyLoopOptimizations ) verify();
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|
|
535 #endif
|
|
|
536 }
|
