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0
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1 /*
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579
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2 * Copyright 1999-2009 Sun Microsystems, Inc. All Rights Reserved.
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0
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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/_c1_Optimizer.cpp.incl"
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27
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28 define_array(ValueSetArray, ValueSet*);
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29 define_stack(ValueSetList, ValueSetArray);
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30
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31
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32 Optimizer::Optimizer(IR* ir) {
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33 assert(ir->is_valid(), "IR must be valid");
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34 _ir = ir;
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35 }
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36
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37 class CE_Eliminator: public BlockClosure {
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38 private:
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39 IR* _hir;
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40 int _cee_count; // the number of CEs successfully eliminated
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41 int _has_substitution;
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42
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43 public:
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44 CE_Eliminator(IR* hir) : _cee_count(0), _hir(hir) {
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45 _has_substitution = false;
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46 _hir->iterate_preorder(this);
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47 if (_has_substitution) {
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48 // substituted some phis so resolve the substitution
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49 SubstitutionResolver sr(_hir);
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50 }
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51 }
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52 int cee_count() const { return _cee_count; }
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53
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54 void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
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55 int e = sux->number_of_exception_handlers();
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56 for (int i = 0; i < e; i++) {
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57 BlockBegin* xhandler = sux->exception_handler_at(i);
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58 block->add_exception_handler(xhandler);
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59
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60 assert(xhandler->is_predecessor(sux), "missing predecessor");
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61 if (sux->number_of_preds() == 0) {
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62 // sux is disconnected from graph so disconnect from exception handlers
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63 xhandler->remove_predecessor(sux);
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64 }
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65 if (!xhandler->is_predecessor(block)) {
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66 xhandler->add_predecessor(block);
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67 }
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68 }
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69 }
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70
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71 virtual void block_do(BlockBegin* block) {
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72 // 1) find conditional expression
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73 // check if block ends with an If
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74 If* if_ = block->end()->as_If();
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75 if (if_ == NULL) return;
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76
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77 // check if If works on int or object types
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78 // (we cannot handle If's working on long, float or doubles yet,
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79 // since IfOp doesn't support them - these If's show up if cmp
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80 // operations followed by If's are eliminated)
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81 ValueType* if_type = if_->x()->type();
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82 if (!if_type->is_int() && !if_type->is_object()) return;
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83
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84 BlockBegin* t_block = if_->tsux();
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85 BlockBegin* f_block = if_->fsux();
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86 Instruction* t_cur = t_block->next();
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87 Instruction* f_cur = f_block->next();
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88
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89 // one Constant may be present between BlockBegin and BlockEnd
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90 Value t_const = NULL;
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91 Value f_const = NULL;
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92 if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
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93 t_const = t_cur;
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94 t_cur = t_cur->next();
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95 }
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96 if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
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97 f_const = f_cur;
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98 f_cur = f_cur->next();
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99 }
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100
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101 // check if both branches end with a goto
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102 Goto* t_goto = t_cur->as_Goto();
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103 if (t_goto == NULL) return;
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104 Goto* f_goto = f_cur->as_Goto();
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105 if (f_goto == NULL) return;
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106
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107 // check if both gotos merge into the same block
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108 BlockBegin* sux = t_goto->default_sux();
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109 if (sux != f_goto->default_sux()) return;
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110
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111 // check if at least one word was pushed on sux_state
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112 ValueStack* sux_state = sux->state();
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113 if (sux_state->stack_size() <= if_->state()->stack_size()) return;
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114
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115 // check if phi function is present at end of successor stack and that
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116 // only this phi was pushed on the stack
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117 Value sux_phi = sux_state->stack_at(if_->state()->stack_size());
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118 if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
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119 if (sux_phi->type()->size() != sux_state->stack_size() - if_->state()->stack_size()) return;
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120
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121 // get the values that were pushed in the true- and false-branch
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122 Value t_value = t_goto->state()->stack_at(if_->state()->stack_size());
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123 Value f_value = f_goto->state()->stack_at(if_->state()->stack_size());
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124
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125 // backend does not support floats
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126 assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
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127 if (t_value->type()->is_float_kind()) return;
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128
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129 // check that successor has no other phi functions but sux_phi
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130 // this can happen when t_block or f_block contained additonal stores to local variables
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131 // that are no longer represented by explicit instructions
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132 for_each_phi_fun(sux, phi,
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133 if (phi != sux_phi) return;
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134 );
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135 // true and false blocks can't have phis
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136 for_each_phi_fun(t_block, phi, return; );
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137 for_each_phi_fun(f_block, phi, return; );
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138
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139 // 2) substitute conditional expression
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140 // with an IfOp followed by a Goto
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141 // cut if_ away and get node before
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142 Instruction* cur_end = if_->prev(block);
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143 int bci = if_->bci();
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144
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145 // append constants of true- and false-block if necessary
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146 // clone constants because original block must not be destroyed
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147 assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
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148 if (t_value == t_const) {
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149 t_value = new Constant(t_const->type());
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150 cur_end = cur_end->set_next(t_value, bci);
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151 }
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152 if (f_value == f_const) {
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153 f_value = new Constant(f_const->type());
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154 cur_end = cur_end->set_next(f_value, bci);
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155 }
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156
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157 // it is very unlikely that the condition can be statically decided
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158 // (this was checked previously by the Canonicalizer), so always
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159 // append IfOp
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160 Value result = new IfOp(if_->x(), if_->cond(), if_->y(), t_value, f_value);
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161 cur_end = cur_end->set_next(result, bci);
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162
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163 // append Goto to successor
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164 ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL;
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165 Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
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166
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167 // prepare state for Goto
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168 ValueStack* goto_state = if_->state();
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169 while (sux_state->scope() != goto_state->scope()) {
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170 goto_state = goto_state->pop_scope();
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171 assert(goto_state != NULL, "states do not match up");
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172 }
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173 goto_state = goto_state->copy();
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174 goto_state->push(result->type(), result);
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175 assert(goto_state->is_same_across_scopes(sux_state), "states must match now");
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176 goto_->set_state(goto_state);
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177
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178 // Steal the bci for the goto from the sux
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179 cur_end = cur_end->set_next(goto_, sux->bci());
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180
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181 // Adjust control flow graph
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182 BlockBegin::disconnect_edge(block, t_block);
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183 BlockBegin::disconnect_edge(block, f_block);
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184 if (t_block->number_of_preds() == 0) {
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185 BlockBegin::disconnect_edge(t_block, sux);
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186 }
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187 adjust_exception_edges(block, t_block);
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188 if (f_block->number_of_preds() == 0) {
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189 BlockBegin::disconnect_edge(f_block, sux);
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190 }
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191 adjust_exception_edges(block, f_block);
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192
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193 // update block end
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194 block->set_end(goto_);
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195
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196 // substitute the phi if possible
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197 if (sux_phi->as_Phi()->operand_count() == 1) {
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198 assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
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199 sux_phi->set_subst(result);
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200 _has_substitution = true;
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201 }
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202
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203 // 3) successfully eliminated a conditional expression
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204 _cee_count++;
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205 if (PrintCEE) {
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206 tty->print_cr("%d. CEE in B%d (B%d B%d)", cee_count(), block->block_id(), t_block->block_id(), f_block->block_id());
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207 }
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208
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209 _hir->verify();
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210 }
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211 };
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212
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213
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214 void Optimizer::eliminate_conditional_expressions() {
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215 // find conditional expressions & replace them with IfOps
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216 CE_Eliminator ce(ir());
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217 }
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218
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219
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220 class BlockMerger: public BlockClosure {
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221 private:
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222 IR* _hir;
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223 int _merge_count; // the number of block pairs successfully merged
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224
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225 public:
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226 BlockMerger(IR* hir)
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227 : _hir(hir)
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228 , _merge_count(0)
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229 {
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230 _hir->iterate_preorder(this);
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231 }
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232
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233 bool try_merge(BlockBegin* block) {
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234 BlockEnd* end = block->end();
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235 if (end->as_Goto() != NULL) {
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236 assert(end->number_of_sux() == 1, "end must have exactly one successor");
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237 // Note: It would be sufficient to check for the number of successors (= 1)
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238 // in order to decide if this block can be merged potentially. That
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239 // would then also include switch statements w/ only a default case.
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240 // However, in that case we would need to make sure the switch tag
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241 // expression is executed if it can produce observable side effects.
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242 // We should probably have the canonicalizer simplifying such switch
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243 // statements and then we are sure we don't miss these merge opportunities
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244 // here (was bug - gri 7/7/99).
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245 BlockBegin* sux = end->default_sux();
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246 if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
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247 // merge the two blocks
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248
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249 #ifdef ASSERT
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250 // verify that state at the end of block and at the beginning of sux are equal
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251 // no phi functions must be present at beginning of sux
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252 ValueStack* sux_state = sux->state();
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253 ValueStack* end_state = end->state();
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254 while (end_state->scope() != sux_state->scope()) {
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255 // match up inlining level
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256 end_state = end_state->pop_scope();
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257 }
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258 assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
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259 assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
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260
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261 int index;
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262 Value sux_value;
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263 for_each_stack_value(sux_state, index, sux_value) {
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264 assert(sux_value == end_state->stack_at(index), "stack not equal");
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265 }
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266 for_each_local_value(sux_state, index, sux_value) {
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267 assert(sux_value == end_state->local_at(index), "locals not equal");
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268 }
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269 assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
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270 #endif
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271
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272 // find instruction before end & append first instruction of sux block
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273 Instruction* prev = end->prev(block);
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274 Instruction* next = sux->next();
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275 assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
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276 prev->set_next(next, next->bci());
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277 sux->disconnect_from_graph();
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278 block->set_end(sux->end());
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279 // add exception handlers of deleted block, if any
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280 for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
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281 BlockBegin* xhandler = sux->exception_handler_at(k);
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282 block->add_exception_handler(xhandler);
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283
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284 // also substitute predecessor of exception handler
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285 assert(xhandler->is_predecessor(sux), "missing predecessor");
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286 xhandler->remove_predecessor(sux);
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287 if (!xhandler->is_predecessor(block)) {
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288 xhandler->add_predecessor(block);
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289 }
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290 }
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291
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292 // debugging output
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293 _merge_count++;
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294 if (PrintBlockElimination) {
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295 tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
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296 _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
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297 }
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298
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299 _hir->verify();
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300
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301 If* if_ = block->end()->as_If();
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302 if (if_) {
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303 IfOp* ifop = if_->x()->as_IfOp();
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304 Constant* con = if_->y()->as_Constant();
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305 bool swapped = false;
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306 if (!con || !ifop) {
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307 ifop = if_->y()->as_IfOp();
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308 con = if_->x()->as_Constant();
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309 swapped = true;
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310 }
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311 if (con && ifop) {
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312 Constant* tval = ifop->tval()->as_Constant();
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313 Constant* fval = ifop->fval()->as_Constant();
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314 if (tval && fval) {
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315 // Find the instruction before if_, starting with ifop.
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316 // When if_ and ifop are not in the same block, prev
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317 // becomes NULL In such (rare) cases it is not
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318 // profitable to perform the optimization.
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319 Value prev = ifop;
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320 while (prev != NULL && prev->next() != if_) {
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321 prev = prev->next();
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322 }
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323
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324 if (prev != NULL) {
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325 Instruction::Condition cond = if_->cond();
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326 BlockBegin* tsux = if_->tsux();
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327 BlockBegin* fsux = if_->fsux();
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328 if (swapped) {
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329 cond = Instruction::mirror(cond);
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330 }
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331
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332 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
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333 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
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334 if (tblock != fblock && !if_->is_safepoint()) {
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335 If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
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336 tblock, fblock, if_->state_before(), if_->is_safepoint());
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337 newif->set_state(if_->state()->copy());
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338
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339 assert(prev->next() == if_, "must be guaranteed by above search");
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340 prev->set_next(newif, if_->bci());
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341 block->set_end(newif);
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342
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343 _merge_count++;
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344 if (PrintBlockElimination) {
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345 tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
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346 }
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347
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348 _hir->verify();
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349 }
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350 }
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351 }
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352 }
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353 }
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354
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355 return true;
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356 }
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357 }
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358 return false;
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359 }
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360
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361 virtual void block_do(BlockBegin* block) {
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362 _hir->verify();
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363 // repeat since the same block may merge again
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364 while (try_merge(block)) {
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365 _hir->verify();
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366 }
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367 }
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368 };
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369
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370
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371 void Optimizer::eliminate_blocks() {
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372 // merge blocks if possible
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373 BlockMerger bm(ir());
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374 }
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375
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376
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377 class NullCheckEliminator;
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378 class NullCheckVisitor: public InstructionVisitor {
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379 private:
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380 NullCheckEliminator* _nce;
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381 NullCheckEliminator* nce() { return _nce; }
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382
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383 public:
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384 NullCheckVisitor() {}
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385
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386 void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
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387
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388 void do_Phi (Phi* x);
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389 void do_Local (Local* x);
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390 void do_Constant (Constant* x);
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391 void do_LoadField (LoadField* x);
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392 void do_StoreField (StoreField* x);
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393 void do_ArrayLength (ArrayLength* x);
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394 void do_LoadIndexed (LoadIndexed* x);
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395 void do_StoreIndexed (StoreIndexed* x);
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396 void do_NegateOp (NegateOp* x);
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397 void do_ArithmeticOp (ArithmeticOp* x);
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398 void do_ShiftOp (ShiftOp* x);
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399 void do_LogicOp (LogicOp* x);
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400 void do_CompareOp (CompareOp* x);
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401 void do_IfOp (IfOp* x);
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402 void do_Convert (Convert* x);
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403 void do_NullCheck (NullCheck* x);
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404 void do_Invoke (Invoke* x);
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405 void do_NewInstance (NewInstance* x);
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406 void do_NewTypeArray (NewTypeArray* x);
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407 void do_NewObjectArray (NewObjectArray* x);
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408 void do_NewMultiArray (NewMultiArray* x);
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409 void do_CheckCast (CheckCast* x);
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410 void do_InstanceOf (InstanceOf* x);
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411 void do_MonitorEnter (MonitorEnter* x);
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412 void do_MonitorExit (MonitorExit* x);
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413 void do_Intrinsic (Intrinsic* x);
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414 void do_BlockBegin (BlockBegin* x);
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415 void do_Goto (Goto* x);
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416 void do_If (If* x);
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417 void do_IfInstanceOf (IfInstanceOf* x);
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418 void do_TableSwitch (TableSwitch* x);
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419 void do_LookupSwitch (LookupSwitch* x);
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420 void do_Return (Return* x);
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421 void do_Throw (Throw* x);
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422 void do_Base (Base* x);
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423 void do_OsrEntry (OsrEntry* x);
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424 void do_ExceptionObject(ExceptionObject* x);
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425 void do_RoundFP (RoundFP* x);
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426 void do_UnsafeGetRaw (UnsafeGetRaw* x);
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427 void do_UnsafePutRaw (UnsafePutRaw* x);
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428 void do_UnsafeGetObject(UnsafeGetObject* x);
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429 void do_UnsafePutObject(UnsafePutObject* x);
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430 void do_UnsafePrefetchRead (UnsafePrefetchRead* x);
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431 void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);
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432 void do_ProfileCall (ProfileCall* x);
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433 void do_ProfileCounter (ProfileCounter* x);
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434 };
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435
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436
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437 // Because of a static contained within (for the purpose of iteration
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438 // over instructions), it is only valid to have one of these active at
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439 // a time
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440 class NullCheckEliminator {
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441 private:
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442 static NullCheckEliminator* _static_nce;
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443 static void do_value(Value* vp);
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444
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445 Optimizer* _opt;
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446
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447 ValueSet* _visitable_instructions; // Visit each instruction only once per basic block
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448 BlockList* _work_list; // Basic blocks to visit
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449
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450 bool visitable(Value x) {
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451 assert(_visitable_instructions != NULL, "check");
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452 return _visitable_instructions->contains(x);
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453 }
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454 void mark_visited(Value x) {
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455 assert(_visitable_instructions != NULL, "check");
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456 _visitable_instructions->remove(x);
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457 }
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458 void mark_visitable(Value x) {
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459 assert(_visitable_instructions != NULL, "check");
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460 _visitable_instructions->put(x);
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461 }
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462 void clear_visitable_state() {
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463 assert(_visitable_instructions != NULL, "check");
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464 _visitable_instructions->clear();
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465 }
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466
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467 ValueSet* _set; // current state, propagated to subsequent BlockBegins
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468 ValueSetList _block_states; // BlockBegin null-check states for all processed blocks
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469 NullCheckVisitor _visitor;
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470 NullCheck* _last_explicit_null_check;
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471
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472 bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); }
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473 void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); }
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474 void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); }
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475
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476 BlockList* work_list() { return _work_list; }
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477
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478 void iterate_all();
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479 void iterate_one(BlockBegin* block);
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480
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481 ValueSet* state() { return _set; }
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482 void set_state_from (ValueSet* state) { _set->set_from(state); }
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483 ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; }
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484 void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; }
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485 // Returns true if caused a change in the block's state.
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486 bool merge_state_for(BlockBegin* block,
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487 ValueSet* incoming_state);
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488
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489 public:
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490 // constructor
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491 NullCheckEliminator(Optimizer* opt)
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492 : _opt(opt)
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493 , _set(new ValueSet())
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494 , _last_explicit_null_check(NULL)
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495 , _block_states(BlockBegin::number_of_blocks(), NULL)
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496 , _work_list(new BlockList()) {
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497 _visitable_instructions = new ValueSet();
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498 _visitor.set_eliminator(this);
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499 }
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500
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501 Optimizer* opt() { return _opt; }
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502 IR* ir () { return opt()->ir(); }
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503
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504 // Process a graph
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505 void iterate(BlockBegin* root);
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506
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507 // In some situations (like NullCheck(x); getfield(x)) the debug
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508 // information from the explicit NullCheck can be used to populate
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509 // the getfield, even if the two instructions are in different
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510 // scopes; this allows implicit null checks to be used but the
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511 // correct exception information to be generated. We must clear the
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512 // last-traversed NullCheck when we reach a potentially-exception-
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513 // throwing instruction, as well as in some other cases.
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514 void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
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515 NullCheck* last_explicit_null_check() { return _last_explicit_null_check; }
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516 Value last_explicit_null_check_obj() { return (_last_explicit_null_check
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517 ? _last_explicit_null_check->obj()
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518 : NULL); }
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519 NullCheck* consume_last_explicit_null_check() {
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520 _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
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521 _last_explicit_null_check->set_can_trap(false);
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522 return _last_explicit_null_check;
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523 }
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524 void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; }
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525
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526 // Handlers for relevant instructions
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527 // (separated out from NullCheckVisitor for clarity)
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528
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529 // The basic contract is that these must leave the instruction in
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530 // the desired state; must not assume anything about the state of
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531 // the instruction. We make multiple passes over some basic blocks
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532 // and the last pass is the only one whose result is valid.
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533 void handle_AccessField (AccessField* x);
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534 void handle_ArrayLength (ArrayLength* x);
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535 void handle_LoadIndexed (LoadIndexed* x);
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536 void handle_StoreIndexed (StoreIndexed* x);
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537 void handle_NullCheck (NullCheck* x);
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538 void handle_Invoke (Invoke* x);
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539 void handle_NewInstance (NewInstance* x);
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540 void handle_NewArray (NewArray* x);
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541 void handle_AccessMonitor (AccessMonitor* x);
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542 void handle_Intrinsic (Intrinsic* x);
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543 void handle_ExceptionObject (ExceptionObject* x);
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544 void handle_Phi (Phi* x);
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545 };
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546
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547
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548 // NEEDS_CLEANUP
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549 // There may be other instructions which need to clear the last
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550 // explicit null check. Anything across which we can not hoist the
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551 // debug information for a NullCheck instruction must clear it. It
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552 // might be safer to pattern match "NullCheck ; {AccessField,
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553 // ArrayLength, LoadIndexed}" but it is more easily structured this way.
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554 // Should test to see performance hit of clearing it for all handlers
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555 // with empty bodies below. If it is negligible then we should leave
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556 // that in for safety, otherwise should think more about it.
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557 void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); }
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558 void NullCheckVisitor::do_Local (Local* x) {}
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559 void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ }
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560 void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); }
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561 void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); }
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562 void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); }
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563 void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); }
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564 void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); }
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565 void NullCheckVisitor::do_NegateOp (NegateOp* x) {}
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566 void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
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567 void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {}
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568 void NullCheckVisitor::do_LogicOp (LogicOp* x) {}
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569 void NullCheckVisitor::do_CompareOp (CompareOp* x) {}
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570 void NullCheckVisitor::do_IfOp (IfOp* x) {}
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571 void NullCheckVisitor::do_Convert (Convert* x) {}
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572 void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); }
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573 void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); }
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574 void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); }
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575 void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); }
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576 void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); }
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577 void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); }
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578 void NullCheckVisitor::do_CheckCast (CheckCast* x) {}
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579 void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {}
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580 void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); }
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581 void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); }
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582 void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->clear_last_explicit_null_check(); }
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583 void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {}
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584 void NullCheckVisitor::do_Goto (Goto* x) {}
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585 void NullCheckVisitor::do_If (If* x) {}
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586 void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {}
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587 void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {}
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588 void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {}
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589 void NullCheckVisitor::do_Return (Return* x) {}
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590 void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); }
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591 void NullCheckVisitor::do_Base (Base* x) {}
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592 void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {}
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593 void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
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594 void NullCheckVisitor::do_RoundFP (RoundFP* x) {}
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595 void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {}
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596 void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {}
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597 void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
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598 void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
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599 void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {}
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600 void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
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601 void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); }
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602 void NullCheckVisitor::do_ProfileCounter (ProfileCounter* x) {}
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603
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604
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605 NullCheckEliminator* NullCheckEliminator::_static_nce = NULL;
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606
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607
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608 void NullCheckEliminator::do_value(Value* p) {
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609 assert(*p != NULL, "should not find NULL instructions");
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610 if (_static_nce->visitable(*p)) {
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611 _static_nce->mark_visited(*p);
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612 (*p)->visit(&_static_nce->_visitor);
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613 }
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614 }
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615
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616 bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
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617 ValueSet* state = state_for(block);
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618 if (state == NULL) {
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619 state = incoming_state->copy();
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620 set_state_for(block, state);
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621 return true;
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622 } else {
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623 bool changed = state->set_intersect(incoming_state);
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624 if (PrintNullCheckElimination && changed) {
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625 tty->print_cr("Block %d's null check state changed", block->block_id());
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626 }
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627 return changed;
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628 }
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629 }
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630
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631
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632 void NullCheckEliminator::iterate_all() {
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633 while (work_list()->length() > 0) {
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634 iterate_one(work_list()->pop());
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635 }
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636 }
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637
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638
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639 void NullCheckEliminator::iterate_one(BlockBegin* block) {
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640 _static_nce = this;
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641 clear_visitable_state();
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642 // clear out an old explicit null checks
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643 set_last_explicit_null_check(NULL);
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644
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645 if (PrintNullCheckElimination) {
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646 tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
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647 block->block_id(),
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648 ir()->method()->holder()->name()->as_utf8(),
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649 ir()->method()->name()->as_utf8(),
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650 ir()->method()->signature()->as_symbol()->as_utf8());
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651 }
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652
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653 // Create new state if none present (only happens at root)
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654 if (state_for(block) == NULL) {
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655 ValueSet* tmp_state = new ValueSet();
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656 set_state_for(block, tmp_state);
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657 // Initial state is that local 0 (receiver) is non-null for
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658 // non-static methods
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659 ValueStack* stack = block->state();
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660 IRScope* scope = stack->scope();
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661 ciMethod* method = scope->method();
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662 if (!method->is_static()) {
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663 Local* local0 = stack->local_at(0)->as_Local();
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664 assert(local0 != NULL, "must be");
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665 assert(local0->type() == objectType, "invalid type of receiver");
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666
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667 if (local0 != NULL) {
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668 // Local 0 is used in this scope
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669 tmp_state->put(local0);
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670 if (PrintNullCheckElimination) {
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671 tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
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672 }
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673 }
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674 }
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675 }
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676
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677 // Must copy block's state to avoid mutating it during iteration
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678 // through the block -- otherwise "not-null" states can accidentally
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679 // propagate "up" through the block during processing of backward
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680 // branches and algorithm is incorrect (and does not converge)
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681 set_state_from(state_for(block));
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682
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683 // allow visiting of Phis belonging to this block
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684 for_each_phi_fun(block, phi,
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685 mark_visitable(phi);
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686 );
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687
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688 BlockEnd* e = block->end();
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689 assert(e != NULL, "incomplete graph");
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690 int i;
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691
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692 // Propagate the state before this block into the exception
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693 // handlers. They aren't true successors since we aren't guaranteed
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694 // to execute the whole block before executing them. Also putting
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695 // them on first seems to help reduce the amount of iteration to
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696 // reach a fixed point.
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697 for (i = 0; i < block->number_of_exception_handlers(); i++) {
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698 BlockBegin* next = block->exception_handler_at(i);
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699 if (merge_state_for(next, state())) {
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700 if (!work_list()->contains(next)) {
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701 work_list()->push(next);
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702 }
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703 }
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704 }
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705
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706 // Iterate through block, updating state.
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707 for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
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708 // Mark instructions in this block as visitable as they are seen
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709 // in the instruction list. This keeps the iteration from
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710 // visiting instructions which are references in other blocks or
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711 // visiting instructions more than once.
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712 mark_visitable(instr);
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713 if (instr->is_root() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
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714 mark_visited(instr);
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715 instr->input_values_do(&NullCheckEliminator::do_value);
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716 instr->visit(&_visitor);
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717 }
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718 }
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719
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720 // Propagate state to successors if necessary
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721 for (i = 0; i < e->number_of_sux(); i++) {
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722 BlockBegin* next = e->sux_at(i);
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723 if (merge_state_for(next, state())) {
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724 if (!work_list()->contains(next)) {
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725 work_list()->push(next);
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726 }
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727 }
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728 }
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729 }
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730
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731
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|
|
732 void NullCheckEliminator::iterate(BlockBegin* block) {
|
|
|
733 work_list()->push(block);
|
|
|
734 iterate_all();
|
|
|
735 }
|
|
|
736
|
|
|
737 void NullCheckEliminator::handle_AccessField(AccessField* x) {
|
|
|
738 if (x->is_static()) {
|
|
|
739 if (x->as_LoadField() != NULL) {
|
|
|
740 // If the field is a non-null static final object field (as is
|
|
|
741 // often the case for sun.misc.Unsafe), put this LoadField into
|
|
|
742 // the non-null map
|
|
|
743 ciField* field = x->field();
|
|
|
744 if (field->is_constant()) {
|
|
|
745 ciConstant field_val = field->constant_value();
|
|
|
746 BasicType field_type = field_val.basic_type();
|
|
|
747 if (field_type == T_OBJECT || field_type == T_ARRAY) {
|
|
|
748 ciObject* obj_val = field_val.as_object();
|
|
|
749 if (!obj_val->is_null_object()) {
|
|
|
750 if (PrintNullCheckElimination) {
|
|
|
751 tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
|
|
|
752 x->id());
|
|
|
753 }
|
|
|
754 set_put(x);
|
|
|
755 }
|
|
|
756 }
|
|
|
757 }
|
|
|
758 }
|
|
|
759 // Be conservative
|
|
|
760 clear_last_explicit_null_check();
|
|
|
761 return;
|
|
|
762 }
|
|
|
763
|
|
|
764 Value obj = x->obj();
|
|
|
765 if (set_contains(obj)) {
|
|
|
766 // Value is non-null => update AccessField
|
|
|
767 if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
|
|
|
768 x->set_explicit_null_check(consume_last_explicit_null_check());
|
|
|
769 x->set_needs_null_check(true);
|
|
|
770 if (PrintNullCheckElimination) {
|
|
|
771 tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
|
|
|
772 x->explicit_null_check()->id(), x->id(), obj->id());
|
|
|
773 }
|
|
|
774 } else {
|
|
|
775 x->set_explicit_null_check(NULL);
|
|
|
776 x->set_needs_null_check(false);
|
|
|
777 if (PrintNullCheckElimination) {
|
|
|
778 tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
|
|
|
779 }
|
|
|
780 }
|
|
|
781 } else {
|
|
|
782 set_put(obj);
|
|
|
783 if (PrintNullCheckElimination) {
|
|
|
784 tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
|
|
|
785 }
|
|
|
786 // Ensure previous passes do not cause wrong state
|
|
|
787 x->set_needs_null_check(true);
|
|
|
788 x->set_explicit_null_check(NULL);
|
|
|
789 }
|
|
|
790 clear_last_explicit_null_check();
|
|
|
791 }
|
|
|
792
|
|
|
793
|
|
|
794 void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
|
|
|
795 Value array = x->array();
|
|
|
796 if (set_contains(array)) {
|
|
|
797 // Value is non-null => update AccessArray
|
|
|
798 if (last_explicit_null_check_obj() == array) {
|
|
|
799 x->set_explicit_null_check(consume_last_explicit_null_check());
|
|
|
800 x->set_needs_null_check(true);
|
|
|
801 if (PrintNullCheckElimination) {
|
|
|
802 tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
|
|
|
803 x->explicit_null_check()->id(), x->id(), array->id());
|
|
|
804 }
|
|
|
805 } else {
|
|
|
806 x->set_explicit_null_check(NULL);
|
|
|
807 x->set_needs_null_check(false);
|
|
|
808 if (PrintNullCheckElimination) {
|
|
|
809 tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
|
|
|
810 }
|
|
|
811 }
|
|
|
812 } else {
|
|
|
813 set_put(array);
|
|
|
814 if (PrintNullCheckElimination) {
|
|
|
815 tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
|
|
|
816 }
|
|
|
817 // Ensure previous passes do not cause wrong state
|
|
|
818 x->set_needs_null_check(true);
|
|
|
819 x->set_explicit_null_check(NULL);
|
|
|
820 }
|
|
|
821 clear_last_explicit_null_check();
|
|
|
822 }
|
|
|
823
|
|
|
824
|
|
|
825 void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
|
|
|
826 Value array = x->array();
|
|
|
827 if (set_contains(array)) {
|
|
|
828 // Value is non-null => update AccessArray
|
|
|
829 if (last_explicit_null_check_obj() == array) {
|
|
|
830 x->set_explicit_null_check(consume_last_explicit_null_check());
|
|
|
831 x->set_needs_null_check(true);
|
|
|
832 if (PrintNullCheckElimination) {
|
|
|
833 tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
|
|
|
834 x->explicit_null_check()->id(), x->id(), array->id());
|
|
|
835 }
|
|
|
836 } else {
|
|
|
837 x->set_explicit_null_check(NULL);
|
|
|
838 x->set_needs_null_check(false);
|
|
|
839 if (PrintNullCheckElimination) {
|
|
|
840 tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
|
|
|
841 }
|
|
|
842 }
|
|
|
843 } else {
|
|
|
844 set_put(array);
|
|
|
845 if (PrintNullCheckElimination) {
|
|
|
846 tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
|
|
|
847 }
|
|
|
848 // Ensure previous passes do not cause wrong state
|
|
|
849 x->set_needs_null_check(true);
|
|
|
850 x->set_explicit_null_check(NULL);
|
|
|
851 }
|
|
|
852 clear_last_explicit_null_check();
|
|
|
853 }
|
|
|
854
|
|
|
855
|
|
|
856 void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
|
|
|
857 Value array = x->array();
|
|
|
858 if (set_contains(array)) {
|
|
|
859 // Value is non-null => update AccessArray
|
|
|
860 if (PrintNullCheckElimination) {
|
|
|
861 tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
|
|
|
862 }
|
|
|
863 x->set_needs_null_check(false);
|
|
|
864 } else {
|
|
|
865 set_put(array);
|
|
|
866 if (PrintNullCheckElimination) {
|
|
|
867 tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
|
|
|
868 }
|
|
|
869 // Ensure previous passes do not cause wrong state
|
|
|
870 x->set_needs_null_check(true);
|
|
|
871 }
|
|
|
872 clear_last_explicit_null_check();
|
|
|
873 }
|
|
|
874
|
|
|
875
|
|
|
876 void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
|
|
|
877 Value obj = x->obj();
|
|
|
878 if (set_contains(obj)) {
|
|
|
879 // Already proven to be non-null => this NullCheck is useless
|
|
|
880 if (PrintNullCheckElimination) {
|
|
|
881 tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
|
|
|
882 }
|
|
|
883 // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
|
|
|
884 // The code generator won't emit LIR for a NullCheck that cannot trap.
|
|
|
885 x->set_can_trap(false);
|
|
|
886 } else {
|
|
|
887 // May be null => add to map and set last explicit NullCheck
|
|
|
888 x->set_can_trap(true);
|
|
|
889 // make sure it's pinned if it can trap
|
|
|
890 x->pin(Instruction::PinExplicitNullCheck);
|
|
|
891 set_put(obj);
|
|
|
892 set_last_explicit_null_check(x);
|
|
|
893 if (PrintNullCheckElimination) {
|
|
|
894 tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
|
|
|
895 }
|
|
|
896 }
|
|
|
897 }
|
|
|
898
|
|
|
899
|
|
|
900 void NullCheckEliminator::handle_Invoke(Invoke* x) {
|
|
|
901 if (!x->has_receiver()) {
|
|
|
902 // Be conservative
|
|
|
903 clear_last_explicit_null_check();
|
|
|
904 return;
|
|
|
905 }
|
|
|
906
|
|
|
907 Value recv = x->receiver();
|
|
|
908 if (!set_contains(recv)) {
|
|
|
909 set_put(recv);
|
|
|
910 if (PrintNullCheckElimination) {
|
|
|
911 tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
|
|
|
912 }
|
|
|
913 }
|
|
|
914 clear_last_explicit_null_check();
|
|
|
915 }
|
|
|
916
|
|
|
917
|
|
|
918 void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
|
|
|
919 set_put(x);
|
|
|
920 if (PrintNullCheckElimination) {
|
|
|
921 tty->print_cr("NewInstance %d is non-null", x->id());
|
|
|
922 }
|
|
|
923 }
|
|
|
924
|
|
|
925
|
|
|
926 void NullCheckEliminator::handle_NewArray(NewArray* x) {
|
|
|
927 set_put(x);
|
|
|
928 if (PrintNullCheckElimination) {
|
|
|
929 tty->print_cr("NewArray %d is non-null", x->id());
|
|
|
930 }
|
|
|
931 }
|
|
|
932
|
|
|
933
|
|
|
934 void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
|
|
|
935 set_put(x);
|
|
|
936 if (PrintNullCheckElimination) {
|
|
|
937 tty->print_cr("ExceptionObject %d is non-null", x->id());
|
|
|
938 }
|
|
|
939 }
|
|
|
940
|
|
|
941
|
|
|
942 void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
|
|
|
943 Value obj = x->obj();
|
|
|
944 if (set_contains(obj)) {
|
|
|
945 // Value is non-null => update AccessMonitor
|
|
|
946 if (PrintNullCheckElimination) {
|
|
|
947 tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
|
|
|
948 }
|
|
|
949 x->set_needs_null_check(false);
|
|
|
950 } else {
|
|
|
951 set_put(obj);
|
|
|
952 if (PrintNullCheckElimination) {
|
|
|
953 tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
|
|
|
954 }
|
|
|
955 // Ensure previous passes do not cause wrong state
|
|
|
956 x->set_needs_null_check(true);
|
|
|
957 }
|
|
|
958 clear_last_explicit_null_check();
|
|
|
959 }
|
|
|
960
|
|
|
961
|
|
|
962 void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
|
|
|
963 if (!x->has_receiver()) {
|
|
|
964 // Be conservative
|
|
|
965 clear_last_explicit_null_check();
|
|
|
966 return;
|
|
|
967 }
|
|
|
968
|
|
|
969 Value recv = x->receiver();
|
|
|
970 if (set_contains(recv)) {
|
|
|
971 // Value is non-null => update Intrinsic
|
|
|
972 if (PrintNullCheckElimination) {
|
|
|
973 tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
|
|
|
974 }
|
|
|
975 x->set_needs_null_check(false);
|
|
|
976 } else {
|
|
|
977 set_put(recv);
|
|
|
978 if (PrintNullCheckElimination) {
|
|
|
979 tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
|
|
|
980 }
|
|
|
981 // Ensure previous passes do not cause wrong state
|
|
|
982 x->set_needs_null_check(true);
|
|
|
983 }
|
|
|
984 clear_last_explicit_null_check();
|
|
|
985 }
|
|
|
986
|
|
|
987
|
|
|
988 void NullCheckEliminator::handle_Phi(Phi* x) {
|
|
|
989 int i;
|
|
|
990 bool all_non_null = true;
|
|
|
991 if (x->is_illegal()) {
|
|
|
992 all_non_null = false;
|
|
|
993 } else {
|
|
|
994 for (i = 0; i < x->operand_count(); i++) {
|
|
|
995 Value input = x->operand_at(i);
|
|
|
996 if (!set_contains(input)) {
|
|
|
997 all_non_null = false;
|
|
|
998 }
|
|
|
999 }
|
|
|
1000 }
|
|
|
1001
|
|
|
1002 if (all_non_null) {
|
|
|
1003 // Value is non-null => update Phi
|
|
|
1004 if (PrintNullCheckElimination) {
|
|
|
1005 tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
|
|
|
1006 }
|
|
|
1007 x->set_needs_null_check(false);
|
|
|
1008 } else if (set_contains(x)) {
|
|
|
1009 set_remove(x);
|
|
|
1010 }
|
|
|
1011 }
|
|
|
1012
|
|
|
1013
|
|
|
1014 void Optimizer::eliminate_null_checks() {
|
|
|
1015 ResourceMark rm;
|
|
|
1016
|
|
|
1017 NullCheckEliminator nce(this);
|
|
|
1018
|
|
|
1019 if (PrintNullCheckElimination) {
|
|
|
1020 tty->print_cr("Starting null check elimination for method %s::%s%s",
|
|
|
1021 ir()->method()->holder()->name()->as_utf8(),
|
|
|
1022 ir()->method()->name()->as_utf8(),
|
|
|
1023 ir()->method()->signature()->as_symbol()->as_utf8());
|
|
|
1024 }
|
|
|
1025
|
|
|
1026 // Apply to graph
|
|
|
1027 nce.iterate(ir()->start());
|
|
|
1028
|
|
|
1029 // walk over the graph looking for exception
|
|
|
1030 // handlers and iterate over them as well
|
|
|
1031 int nblocks = BlockBegin::number_of_blocks();
|
|
|
1032 BlockList blocks(nblocks);
|
|
|
1033 boolArray visited_block(nblocks, false);
|
|
|
1034
|
|
|
1035 blocks.push(ir()->start());
|
|
|
1036 visited_block[ir()->start()->block_id()] = true;
|
|
|
1037 for (int i = 0; i < blocks.length(); i++) {
|
|
|
1038 BlockBegin* b = blocks[i];
|
|
|
1039 // exception handlers need to be treated as additional roots
|
|
|
1040 for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
|
|
|
1041 BlockBegin* excp = b->exception_handler_at(e);
|
|
|
1042 int id = excp->block_id();
|
|
|
1043 if (!visited_block[id]) {
|
|
|
1044 blocks.push(excp);
|
|
|
1045 visited_block[id] = true;
|
|
|
1046 nce.iterate(excp);
|
|
|
1047 }
|
|
|
1048 }
|
|
|
1049 // traverse successors
|
|
|
1050 BlockEnd *end = b->end();
|
|
|
1051 for (int s = end->number_of_sux(); s-- > 0; ) {
|
|
|
1052 BlockBegin* next = end->sux_at(s);
|
|
|
1053 int id = next->block_id();
|
|
|
1054 if (!visited_block[id]) {
|
|
|
1055 blocks.push(next);
|
|
|
1056 visited_block[id] = true;
|
|
|
1057 }
|
|
|
1058 }
|
|
|
1059 }
|
|
|
1060
|
|
|
1061
|
|
|
1062 if (PrintNullCheckElimination) {
|
|
|
1063 tty->print_cr("Done with null check elimination for method %s::%s%s",
|
|
|
1064 ir()->method()->holder()->name()->as_utf8(),
|
|
|
1065 ir()->method()->name()->as_utf8(),
|
|
|
1066 ir()->method()->signature()->as_symbol()->as_utf8());
|
|
|
1067 }
|
|
|
1068 }
|
