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1 /* |
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2 * Copyright 2000-2006 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 // Portions of code courtesy of Clifford Click |
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26 |
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27 // Optimization - Graph Style |
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28 |
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29 #include "incls/_precompiled.incl" |
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30 #include "incls/_ifnode.cpp.incl" |
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31 |
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32 |
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33 extern int explicit_null_checks_elided; |
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34 |
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35 //============================================================================= |
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36 //------------------------------Value------------------------------------------ |
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37 // Return a tuple for whichever arm of the IF is reachable |
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38 const Type *IfNode::Value( PhaseTransform *phase ) const { |
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39 if( !in(0) ) return Type::TOP; |
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40 if( phase->type(in(0)) == Type::TOP ) |
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41 return Type::TOP; |
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42 const Type *t = phase->type(in(1)); |
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43 if( t == Type::TOP ) // data is undefined |
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44 return TypeTuple::IFNEITHER; // unreachable altogether |
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45 if( t == TypeInt::ZERO ) // zero, or false |
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46 return TypeTuple::IFFALSE; // only false branch is reachable |
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47 if( t == TypeInt::ONE ) // 1, or true |
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48 return TypeTuple::IFTRUE; // only true branch is reachable |
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49 assert( t == TypeInt::BOOL, "expected boolean type" ); |
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50 |
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51 return TypeTuple::IFBOTH; // No progress |
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52 } |
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53 |
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54 const RegMask &IfNode::out_RegMask() const { |
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55 return RegMask::Empty; |
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56 } |
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57 |
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58 //------------------------------split_if--------------------------------------- |
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59 // Look for places where we merge constants, then test on the merged value. |
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60 // If the IF test will be constant folded on the path with the constant, we |
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61 // win by splitting the IF to before the merge point. |
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62 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) { |
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63 // I could be a lot more general here, but I'm trying to squeeze this |
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64 // in before the Christmas '98 break so I'm gonna be kinda restrictive |
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65 // on the patterns I accept. CNC |
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66 |
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67 // Look for a compare of a constant and a merged value |
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68 Node *i1 = iff->in(1); |
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69 if( !i1->is_Bool() ) return NULL; |
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70 BoolNode *b = i1->as_Bool(); |
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71 Node *cmp = b->in(1); |
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72 if( !cmp->is_Cmp() ) return NULL; |
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73 i1 = cmp->in(1); |
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74 if( i1 == NULL || !i1->is_Phi() ) return NULL; |
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75 PhiNode *phi = i1->as_Phi(); |
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76 if( phi->is_copy() ) return NULL; |
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77 Node *con2 = cmp->in(2); |
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78 if( !con2->is_Con() ) return NULL; |
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79 // See that the merge point contains some constants |
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80 Node *con1=NULL; |
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81 uint i4; |
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82 for( i4 = 1; i4 < phi->req(); i4++ ) { |
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83 con1 = phi->in(i4); |
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84 if( !con1 ) return NULL; // Do not optimize partially collaped merges |
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85 if( con1->is_Con() ) break; // Found a constant |
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86 // Also allow null-vs-not-null checks |
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87 const TypePtr *tp = igvn->type(con1)->isa_ptr(); |
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88 if( tp && tp->_ptr == TypePtr::NotNull ) |
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89 break; |
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90 } |
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91 if( i4 >= phi->req() ) return NULL; // Found no constants |
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92 |
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93 igvn->C->set_has_split_ifs(true); // Has chance for split-if |
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94 |
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95 // Make sure that the compare can be constant folded away |
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96 Node *cmp2 = cmp->clone(); |
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97 cmp2->set_req(1,con1); |
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98 cmp2->set_req(2,con2); |
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99 const Type *t = cmp2->Value(igvn); |
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100 // This compare is dead, so whack it! |
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101 igvn->remove_dead_node(cmp2); |
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102 if( !t->singleton() ) return NULL; |
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103 |
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104 // No intervening control, like a simple Call |
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105 Node *r = iff->in(0); |
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106 if( !r->is_Region() ) return NULL; |
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107 if( phi->region() != r ) return NULL; |
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108 // No other users of the cmp/bool |
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109 if (b->outcnt() != 1 || cmp->outcnt() != 1) { |
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110 //tty->print_cr("many users of cmp/bool"); |
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111 return NULL; |
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112 } |
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113 |
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114 // Make sure we can determine where all the uses of merged values go |
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115 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) { |
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116 Node* u = r->fast_out(j); |
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117 if( u == r ) continue; |
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118 if( u == iff ) continue; |
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119 if( u->outcnt() == 0 ) continue; // use is dead & ignorable |
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120 if( !u->is_Phi() ) { |
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121 /* |
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122 if( u->is_Start() ) { |
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123 tty->print_cr("Region has inlined start use"); |
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124 } else { |
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125 tty->print_cr("Region has odd use"); |
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126 u->dump(2); |
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127 }*/ |
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128 return NULL; |
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129 } |
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130 if( u != phi ) { |
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131 // CNC - do not allow any other merged value |
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132 //tty->print_cr("Merging another value"); |
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133 //u->dump(2); |
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134 return NULL; |
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135 } |
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136 // Make sure we can account for all Phi uses |
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137 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) { |
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138 Node* v = u->fast_out(k); // User of the phi |
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139 // CNC - Allow only really simple patterns. |
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140 // In particular I disallow AddP of the Phi, a fairly common pattern |
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141 if( v == cmp ) continue; // The compare is OK |
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142 if( (v->is_ConstraintCast()) && |
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143 v->in(0)->in(0) == iff ) |
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144 continue; // CastPP/II of the IfNode is OK |
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145 // Disabled following code because I cannot tell if exactly one |
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146 // path dominates without a real dominator check. CNC 9/9/1999 |
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147 //uint vop = v->Opcode(); |
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148 //if( vop == Op_Phi ) { // Phi from another merge point might be OK |
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149 // Node *r = v->in(0); // Get controlling point |
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150 // if( !r ) return NULL; // Degraded to a copy |
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151 // // Find exactly one path in (either True or False doms, but not IFF) |
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152 // int cnt = 0; |
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153 // for( uint i = 1; i < r->req(); i++ ) |
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154 // if( r->in(i) && r->in(i)->in(0) == iff ) |
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155 // cnt++; |
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156 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi |
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157 //} |
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158 if( !v->is_Call() ) { |
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159 /* |
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160 if( v->Opcode() == Op_AddP ) { |
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161 tty->print_cr("Phi has AddP use"); |
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162 } else if( v->Opcode() == Op_CastPP ) { |
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163 tty->print_cr("Phi has CastPP use"); |
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164 } else if( v->Opcode() == Op_CastII ) { |
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165 tty->print_cr("Phi has CastII use"); |
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166 } else { |
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167 tty->print_cr("Phi has use I cant be bothered with"); |
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168 } |
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169 */ |
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170 } |
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171 return NULL; |
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172 |
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173 /* CNC - Cut out all the fancy acceptance tests |
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174 // Can we clone this use when doing the transformation? |
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175 // If all uses are from Phis at this merge or constants, then YES. |
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176 if( !v->in(0) && v != cmp ) { |
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177 tty->print_cr("Phi has free-floating use"); |
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178 v->dump(2); |
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179 return NULL; |
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180 } |
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181 for( uint l = 1; l < v->req(); l++ ) { |
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182 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) && |
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183 !v->in(l)->is_Con() ) { |
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184 tty->print_cr("Phi has use"); |
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185 v->dump(2); |
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186 return NULL; |
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187 } // End of if Phi-use input is neither Phi nor Constant |
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188 } // End of for all inputs to Phi-use |
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189 */ |
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190 } // End of for all uses of Phi |
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191 } // End of for all uses of Region |
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192 |
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193 // Only do this if the IF node is in a sane state |
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194 if (iff->outcnt() != 2) |
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195 return NULL; |
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196 |
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197 // Got a hit! Do the Mondo Hack! |
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198 // |
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199 //ABC a1c def ghi B 1 e h A C a c d f g i |
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200 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi |
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201 // cmp - 2 cmp - 2 cmp - 2 |
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202 // bool bool_c bool_x |
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203 // if if_c if_x |
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204 // T F T F T F |
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205 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t.. |
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206 // |
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207 // Split the paths coming into the merge point into 2 seperate groups of |
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208 // merges. On the left will be all the paths feeding constants into the |
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209 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi |
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210 // will fold up into a constant; this will let the Cmp fold up as well as |
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211 // all the control flow. Below the original IF we have 2 control |
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212 // dependent regions, 's' and 't'. Now we will merge the two paths |
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213 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite |
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214 // likely 2 or more) will promptly constant fold away. |
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215 PhaseGVN *phase = igvn; |
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216 |
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217 // Make a region merging constants and a region merging the rest |
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218 uint req_c = 0; |
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219 for (uint ii = 1; ii < r->req(); ii++) { |
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220 if( phi->in(ii) == con1 ) { |
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221 req_c++; |
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222 } |
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223 } |
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224 Node *region_c = new (igvn->C, req_c + 1) RegionNode(req_c + 1); |
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225 Node *phi_c = con1; |
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226 uint len = r->req(); |
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227 Node *region_x = new (igvn->C, len - req_c + 1) RegionNode(len - req_c + 1); |
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228 Node *phi_x = PhiNode::make_blank(region_x, phi); |
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229 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) { |
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230 if( phi->in(i) == con1 ) { |
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231 region_c->init_req( i_c++, r ->in(i) ); |
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232 } else { |
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233 region_x->init_req( i_x, r ->in(i) ); |
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234 phi_x ->init_req( i_x++, phi->in(i) ); |
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235 } |
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236 } |
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237 |
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238 // Register the new RegionNodes but do not transform them. Cannot |
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239 // transform until the entire Region/Phi conglerate has been hacked |
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240 // as a single huge transform. |
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241 igvn->register_new_node_with_optimizer( region_c ); |
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242 igvn->register_new_node_with_optimizer( region_x ); |
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243 phi_x = phase->transform( phi_x ); |
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244 // Prevent the untimely death of phi_x. Currently he has no uses. He is |
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245 // about to get one. If this only use goes away, then phi_x will look dead. |
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246 // However, he will be picking up some more uses down below. |
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247 Node *hook = new (igvn->C, 4) Node(4); |
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248 hook->init_req(0, phi_x); |
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249 hook->init_req(1, phi_c); |
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250 |
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251 // Make the compare |
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252 Node *cmp_c = phase->makecon(t); |
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253 Node *cmp_x = cmp->clone(); |
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254 cmp_x->set_req(1,phi_x); |
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255 cmp_x->set_req(2,con2); |
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256 cmp_x = phase->transform(cmp_x); |
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257 // Make the bool |
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258 Node *b_c = phase->transform(new (igvn->C, 2) BoolNode(cmp_c,b->_test._test)); |
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259 Node *b_x = phase->transform(new (igvn->C, 2) BoolNode(cmp_x,b->_test._test)); |
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260 // Make the IfNode |
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261 IfNode *iff_c = new (igvn->C, 2) IfNode(region_c,b_c,iff->_prob,iff->_fcnt); |
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262 igvn->set_type_bottom(iff_c); |
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263 igvn->_worklist.push(iff_c); |
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264 hook->init_req(2, iff_c); |
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265 |
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266 IfNode *iff_x = new (igvn->C, 2) IfNode(region_x,b_x,iff->_prob, iff->_fcnt); |
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267 igvn->set_type_bottom(iff_x); |
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268 igvn->_worklist.push(iff_x); |
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269 hook->init_req(3, iff_x); |
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270 |
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271 // Make the true/false arms |
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272 Node *iff_c_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_c)); |
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273 Node *iff_c_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_c)); |
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274 Node *iff_x_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_x)); |
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275 Node *iff_x_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_x)); |
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276 |
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277 // Merge the TRUE paths |
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278 Node *region_s = new (igvn->C, 3) RegionNode(3); |
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279 igvn->_worklist.push(region_s); |
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280 region_s->init_req(1, iff_c_t); |
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281 region_s->init_req(2, iff_x_t); |
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282 igvn->register_new_node_with_optimizer( region_s ); |
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283 |
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284 // Merge the FALSE paths |
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285 Node *region_f = new (igvn->C, 3) RegionNode(3); |
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286 igvn->_worklist.push(region_f); |
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287 region_f->init_req(1, iff_c_f); |
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288 region_f->init_req(2, iff_x_f); |
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289 igvn->register_new_node_with_optimizer( region_f ); |
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290 |
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291 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table. |
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292 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead |
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293 cmp->set_req(2,NULL); |
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294 // Check for all uses of the Phi and give them a new home. |
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295 // The 'cmp' got cloned, but CastPP/IIs need to be moved. |
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296 Node *phi_s = NULL; // do not construct unless needed |
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297 Node *phi_f = NULL; // do not construct unless needed |
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298 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) { |
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299 Node* v = phi->last_out(i2);// User of the phi |
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300 igvn->hash_delete(v); // Have to fixup other Phi users |
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301 igvn->_worklist.push(v); |
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302 uint vop = v->Opcode(); |
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303 Node *proj = NULL; |
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304 if( vop == Op_Phi ) { // Remote merge point |
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305 Node *r = v->in(0); |
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306 for (uint i3 = 1; i3 < r->req(); i3++) |
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307 if (r->in(i3) && r->in(i3)->in(0) == iff) { |
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308 proj = r->in(i3); |
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309 break; |
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310 } |
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311 } else if( v->is_ConstraintCast() ) { |
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312 proj = v->in(0); // Controlling projection |
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313 } else { |
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314 assert( 0, "do not know how to handle this guy" ); |
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315 } |
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316 |
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317 Node *proj_path_data, *proj_path_ctrl; |
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318 if( proj->Opcode() == Op_IfTrue ) { |
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319 if( phi_s == NULL ) { |
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320 // Only construct phi_s if needed, otherwise provides |
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321 // interfering use. |
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322 phi_s = PhiNode::make_blank(region_s,phi); |
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323 phi_s->init_req( 1, phi_c ); |
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324 phi_s->init_req( 2, phi_x ); |
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325 phi_s = phase->transform(phi_s); |
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326 } |
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327 proj_path_data = phi_s; |
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328 proj_path_ctrl = region_s; |
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329 } else { |
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330 if( phi_f == NULL ) { |
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331 // Only construct phi_f if needed, otherwise provides |
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332 // interfering use. |
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333 phi_f = PhiNode::make_blank(region_f,phi); |
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334 phi_f->init_req( 1, phi_c ); |
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335 phi_f->init_req( 2, phi_x ); |
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336 phi_f = phase->transform(phi_f); |
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337 } |
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338 proj_path_data = phi_f; |
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339 proj_path_ctrl = region_f; |
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340 } |
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341 |
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342 // Fixup 'v' for for the split |
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343 if( vop == Op_Phi ) { // Remote merge point |
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344 uint i; |
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345 for( i = 1; i < v->req(); i++ ) |
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346 if( v->in(i) == phi ) |
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347 break; |
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348 v->set_req(i, proj_path_data ); |
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349 } else if( v->is_ConstraintCast() ) { |
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350 v->set_req(0, proj_path_ctrl ); |
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351 v->set_req(1, proj_path_data ); |
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352 } else |
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353 ShouldNotReachHere(); |
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354 } |
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355 |
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356 // Now replace the original iff's True/False with region_s/region_t. |
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357 // This makes the original iff go dead. |
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358 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) { |
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359 Node* p = iff->last_out(i3); |
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360 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" ); |
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361 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f; |
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362 // Replace p with u |
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363 igvn->add_users_to_worklist(p); |
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364 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) { |
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365 Node* x = p->last_out(l); |
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366 igvn->hash_delete(x); |
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367 uint uses_found = 0; |
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368 for( uint j = 0; j < x->req(); j++ ) { |
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369 if( x->in(j) == p ) { |
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370 x->set_req(j, u); |
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371 uses_found++; |
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372 } |
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373 } |
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374 l -= uses_found; // we deleted 1 or more copies of this edge |
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375 } |
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376 igvn->remove_dead_node(p); |
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377 } |
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378 |
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379 // Force the original merge dead |
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380 igvn->hash_delete(r); |
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381 r->set_req_X(0,NULL,igvn); |
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382 |
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383 // Now remove the bogus extra edges used to keep things alive |
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384 igvn->remove_dead_node( hook ); |
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385 |
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386 // Must return either the original node (now dead) or a new node |
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387 // (Do not return a top here, since that would break the uniqueness of top.) |
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388 return new (igvn->C, 1) ConINode(TypeInt::ZERO); |
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389 } |
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390 |
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391 //------------------------------is_range_check--------------------------------- |
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392 // Return 0 if not a range check. Return 1 if a range check and set index and |
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393 // offset. Return 2 if we had to negate the test. Index is NULL if the check |
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394 // is versus a constant. |
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395 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) { |
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396 Node* b = in(1); |
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397 if (b == NULL || !b->is_Bool()) return 0; |
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398 BoolNode* bn = b->as_Bool(); |
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399 Node* cmp = bn->in(1); |
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400 if (cmp == NULL) return 0; |
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401 if (cmp->Opcode() != Op_CmpU) return 0; |
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402 |
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403 Node* l = cmp->in(1); |
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404 Node* r = cmp->in(2); |
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405 int flip_test = 1; |
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406 if (bn->_test._test == BoolTest::le) { |
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407 l = cmp->in(2); |
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408 r = cmp->in(1); |
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409 flip_test = 2; |
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410 } else if (bn->_test._test != BoolTest::lt) { |
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411 return 0; |
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412 } |
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413 if (l->is_top()) return 0; // Top input means dead test |
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414 if (r->Opcode() != Op_LoadRange) return 0; |
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415 |
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416 // We have recognized one of these forms: |
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417 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ... |
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418 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ... |
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419 |
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420 // Make sure it's a real range check by requiring an uncommon trap |
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421 // along the OOB path. Otherwise, it's possible that the user wrote |
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422 // something which optimized to look like a range check but behaves |
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423 // in some other way. |
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424 Node* iftrap = proj_out(flip_test == 2 ? true : false); |
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425 bool found_trap = false; |
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426 if (iftrap != NULL) { |
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427 Node* u = iftrap->unique_ctrl_out(); |
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428 if (u != NULL) { |
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429 // It could be a merge point (Region) for uncommon trap. |
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430 if (u->is_Region()) { |
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431 Node* c = u->unique_ctrl_out(); |
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432 if (c != NULL) { |
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433 iftrap = u; |
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434 u = c; |
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435 } |
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436 } |
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437 if (u->in(0) == iftrap && u->is_CallStaticJava()) { |
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438 int req = u->as_CallStaticJava()->uncommon_trap_request(); |
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439 if (Deoptimization::trap_request_reason(req) == |
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440 Deoptimization::Reason_range_check) { |
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441 found_trap = true; |
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442 } |
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443 } |
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444 } |
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445 } |
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446 if (!found_trap) return 0; // sorry, no cigar |
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447 |
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448 // Look for index+offset form |
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449 Node* ind = l; |
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450 jint off = 0; |
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451 if (l->is_top()) { |
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452 return 0; |
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453 } else if (l->is_Add()) { |
|
454 if ((off = l->in(1)->find_int_con(0)) != 0) { |
|
455 ind = l->in(2); |
|
456 } else if ((off = l->in(2)->find_int_con(0)) != 0) { |
|
457 ind = l->in(1); |
|
458 } |
|
459 } else if ((off = l->find_int_con(-1)) >= 0) { |
|
460 // constant offset with no variable index |
|
461 ind = NULL; |
|
462 } else { |
|
463 // variable index with no constant offset (or dead negative index) |
|
464 off = 0; |
|
465 } |
|
466 |
|
467 // Return all the values: |
|
468 index = ind; |
|
469 offset = off; |
|
470 range = r; |
|
471 return flip_test; |
|
472 } |
|
473 |
|
474 //------------------------------adjust_check----------------------------------- |
|
475 // Adjust (widen) a prior range check |
|
476 static void adjust_check(Node* proj, Node* range, Node* index, |
|
477 int flip, jint off_lo, PhaseIterGVN* igvn) { |
|
478 PhaseGVN *gvn = igvn; |
|
479 // Break apart the old check |
|
480 Node *iff = proj->in(0); |
|
481 Node *bol = iff->in(1); |
|
482 if( bol->is_top() ) return; // In case a partially dead range check appears |
|
483 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode |
|
484 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } ) |
|
485 if( !bol->is_Bool() ) return; |
|
486 |
|
487 Node *cmp = bol->in(1); |
|
488 // Compute a new check |
|
489 Node *new_add = gvn->intcon(off_lo); |
|
490 if( index ) { |
|
491 new_add = off_lo ? gvn->transform(new (gvn->C, 3) AddINode( index, new_add )) : index; |
|
492 } |
|
493 Node *new_cmp = (flip == 1) |
|
494 ? new (gvn->C, 3) CmpUNode( new_add, range ) |
|
495 : new (gvn->C, 3) CmpUNode( range, new_add ); |
|
496 new_cmp = gvn->transform(new_cmp); |
|
497 // See if no need to adjust the existing check |
|
498 if( new_cmp == cmp ) return; |
|
499 // Else, adjust existing check |
|
500 Node *new_bol = gvn->transform( new (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); |
|
501 igvn->hash_delete( iff ); |
|
502 iff->set_req_X( 1, new_bol, igvn ); |
|
503 } |
|
504 |
|
505 //------------------------------up_one_dom------------------------------------- |
|
506 // Walk up the dominator tree one step. Return NULL at root or true |
|
507 // complex merges. Skips through small diamonds. |
|
508 Node* IfNode::up_one_dom(Node *curr, bool linear_only) { |
|
509 Node *dom = curr->in(0); |
|
510 if( !dom ) // Found a Region degraded to a copy? |
|
511 return curr->nonnull_req(); // Skip thru it |
|
512 |
|
513 if( curr != dom ) // Normal walk up one step? |
|
514 return dom; |
|
515 |
|
516 // Use linear_only if we are still parsing, since we cannot |
|
517 // trust the regions to be fully filled in. |
|
518 if (linear_only) |
|
519 return NULL; |
|
520 |
|
521 // Else hit a Region. Check for a loop header |
|
522 if( dom->is_Loop() ) |
|
523 return dom->in(1); // Skip up thru loops |
|
524 |
|
525 // Check for small diamonds |
|
526 Node *din1, *din2, *din3, *din4; |
|
527 if( dom->req() == 3 && // 2-path merge point |
|
528 (din1 = dom ->in(1)) && // Left path exists |
|
529 (din2 = dom ->in(2)) && // Right path exists |
|
530 (din3 = din1->in(0)) && // Left path up one |
|
531 (din4 = din2->in(0)) ) { // Right path up one |
|
532 if( din3->is_Call() && // Handle a slow-path call on either arm |
|
533 (din3 = din3->in(0)) ) |
|
534 din3 = din3->in(0); |
|
535 if( din4->is_Call() && // Handle a slow-path call on either arm |
|
536 (din4 = din4->in(0)) ) |
|
537 din4 = din4->in(0); |
|
538 if( din3 == din4 && din3->is_If() ) |
|
539 return din3; // Skip around diamonds |
|
540 } |
|
541 |
|
542 // Give up the search at true merges |
|
543 return NULL; // Dead loop? Or hit root? |
|
544 } |
|
545 |
|
546 //------------------------------remove_useless_bool---------------------------- |
|
547 // Check for people making a useless boolean: things like |
|
548 // if( (x < y ? true : false) ) { ... } |
|
549 // Replace with if( x < y ) { ... } |
|
550 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { |
|
551 Node *i1 = iff->in(1); |
|
552 if( !i1->is_Bool() ) return NULL; |
|
553 BoolNode *bol = i1->as_Bool(); |
|
554 |
|
555 Node *cmp = bol->in(1); |
|
556 if( cmp->Opcode() != Op_CmpI ) return NULL; |
|
557 |
|
558 // Must be comparing against a bool |
|
559 const Type *cmp2_t = phase->type( cmp->in(2) ); |
|
560 if( cmp2_t != TypeInt::ZERO && |
|
561 cmp2_t != TypeInt::ONE ) |
|
562 return NULL; |
|
563 |
|
564 // Find a prior merge point merging the boolean |
|
565 i1 = cmp->in(1); |
|
566 if( !i1->is_Phi() ) return NULL; |
|
567 PhiNode *phi = i1->as_Phi(); |
|
568 if( phase->type( phi ) != TypeInt::BOOL ) |
|
569 return NULL; |
|
570 |
|
571 // Check for diamond pattern |
|
572 int true_path = phi->is_diamond_phi(); |
|
573 if( true_path == 0 ) return NULL; |
|
574 |
|
575 // phi->region->if_proj->ifnode->bool->cmp |
|
576 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); |
|
577 |
|
578 // Now get the 'sense' of the test correct so we can plug in |
|
579 // either iff2->in(1) or its complement. |
|
580 int flip = 0; |
|
581 if( bol->_test._test == BoolTest::ne ) flip = 1-flip; |
|
582 else if( bol->_test._test != BoolTest::eq ) return NULL; |
|
583 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; |
|
584 |
|
585 const Type *phi1_t = phase->type( phi->in(1) ); |
|
586 const Type *phi2_t = phase->type( phi->in(2) ); |
|
587 // Check for Phi(0,1) and flip |
|
588 if( phi1_t == TypeInt::ZERO ) { |
|
589 if( phi2_t != TypeInt::ONE ) return NULL; |
|
590 flip = 1-flip; |
|
591 } else { |
|
592 // Check for Phi(1,0) |
|
593 if( phi1_t != TypeInt::ONE ) return NULL; |
|
594 if( phi2_t != TypeInt::ZERO ) return NULL; |
|
595 } |
|
596 if( true_path == 2 ) { |
|
597 flip = 1-flip; |
|
598 } |
|
599 |
|
600 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); |
|
601 iff->set_req(1, new_bol); |
|
602 // Intervening diamond probably goes dead |
|
603 phase->C->set_major_progress(); |
|
604 return iff; |
|
605 } |
|
606 |
|
607 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); |
|
608 |
|
609 //------------------------------Ideal------------------------------------------ |
|
610 // Return a node which is more "ideal" than the current node. Strip out |
|
611 // control copies |
|
612 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { |
|
613 if (remove_dead_region(phase, can_reshape)) return this; |
|
614 // No Def-Use info? |
|
615 if (!can_reshape) return NULL; |
|
616 PhaseIterGVN *igvn = phase->is_IterGVN(); |
|
617 |
|
618 // Don't bother trying to transform a dead if |
|
619 if (in(0)->is_top()) return NULL; |
|
620 // Don't bother trying to transform an if with a dead test |
|
621 if (in(1)->is_top()) return NULL; |
|
622 // Another variation of a dead test |
|
623 if (in(1)->is_Con()) return NULL; |
|
624 // Another variation of a dead if |
|
625 if (outcnt() < 2) return NULL; |
|
626 |
|
627 // Canonicalize the test. |
|
628 Node* idt_if = idealize_test(phase, this); |
|
629 if (idt_if != NULL) return idt_if; |
|
630 |
|
631 // Try to split the IF |
|
632 Node *s = split_if(this, igvn); |
|
633 if (s != NULL) return s; |
|
634 |
|
635 // Check for people making a useless boolean: things like |
|
636 // if( (x < y ? true : false) ) { ... } |
|
637 // Replace with if( x < y ) { ... } |
|
638 Node *bol2 = remove_useless_bool(this, phase); |
|
639 if( bol2 ) return bol2; |
|
640 |
|
641 // Setup to scan up the CFG looking for a dominating test |
|
642 Node *dom = in(0); |
|
643 Node *prev_dom = this; |
|
644 |
|
645 // Check for range-check vs other kinds of tests |
|
646 Node *index1, *range1; |
|
647 jint offset1; |
|
648 int flip1 = is_range_check(range1, index1, offset1); |
|
649 if( flip1 ) { |
|
650 Node *first_prev_dom = NULL; |
|
651 |
|
652 // Try to remove extra range checks. All 'up_one_dom' gives up at merges |
|
653 // so all checks we inspect post-dominate the top-most check we find. |
|
654 // If we are going to fail the current check and we reach the top check |
|
655 // then we are guarenteed to fail, so just start interpreting there. |
|
656 // We 'expand' the top 2 range checks to include all post-dominating |
|
657 // checks. |
|
658 |
|
659 // The top 2 range checks seen |
|
660 Node *prev_chk1 = NULL; |
|
661 Node *prev_chk2 = NULL; |
|
662 // Low and high offsets seen so far |
|
663 jint off_lo = offset1; |
|
664 jint off_hi = offset1; |
|
665 |
|
666 // Scan for the top 2 checks and collect range of offsets |
|
667 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit |
|
668 if( dom->Opcode() == Op_If && // Not same opcode? |
|
669 prev_dom->in(0) == dom ) { // One path of test does dominate? |
|
670 if( dom == this ) return NULL; // dead loop |
|
671 // See if this is a range check |
|
672 Node *index2, *range2; |
|
673 jint offset2; |
|
674 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2); |
|
675 // See if this is a _matching_ range check, checking against |
|
676 // the same array bounds. |
|
677 if( flip2 == flip1 && range2 == range1 && index2 == index1 && |
|
678 dom->outcnt() == 2 ) { |
|
679 // Gather expanded bounds |
|
680 off_lo = MIN2(off_lo,offset2); |
|
681 off_hi = MAX2(off_hi,offset2); |
|
682 // Record top 2 range checks |
|
683 prev_chk2 = prev_chk1; |
|
684 prev_chk1 = prev_dom; |
|
685 // If we match the test exactly, then the top test covers |
|
686 // both our lower and upper bounds. |
|
687 if( dom->in(1) == in(1) ) |
|
688 prev_chk2 = prev_chk1; |
|
689 } |
|
690 } |
|
691 prev_dom = dom; |
|
692 dom = up_one_dom( dom ); |
|
693 if( !dom ) break; |
|
694 } |
|
695 |
|
696 |
|
697 // Attempt to widen the dominating range check to cover some later |
|
698 // ones. Since range checks "fail" by uncommon-trapping to the |
|
699 // interpreter, widening a check can make us speculative enter the |
|
700 // interpreter. If we see range-check deopt's, do not widen! |
|
701 if (!phase->C->allow_range_check_smearing()) return NULL; |
|
702 |
|
703 // Constant indices only need to check the upper bound. |
|
704 // Non-constance indices must check both low and high. |
|
705 if( index1 ) { |
|
706 // Didn't find 2 prior covering checks, so cannot remove anything. |
|
707 if( !prev_chk2 ) return NULL; |
|
708 // 'Widen' the offsets of the 1st and 2nd covering check |
|
709 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn ); |
|
710 // Do not call adjust_check twice on the same projection |
|
711 // as the first call may have transformed the BoolNode to a ConI |
|
712 if( prev_chk1 != prev_chk2 ) { |
|
713 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn ); |
|
714 } |
|
715 // Test is now covered by prior checks, dominate it out |
|
716 prev_dom = prev_chk2; |
|
717 } else { |
|
718 // Didn't find prior covering check, so cannot remove anything. |
|
719 if( !prev_chk1 ) return NULL; |
|
720 // 'Widen' the offset of the 1st and only covering check |
|
721 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn ); |
|
722 // Test is now covered by prior checks, dominate it out |
|
723 prev_dom = prev_chk1; |
|
724 } |
|
725 |
|
726 |
|
727 } else { // Scan for an equivalent test |
|
728 |
|
729 Node *cmp; |
|
730 int dist = 0; // Cutoff limit for search |
|
731 int op = Opcode(); |
|
732 if( op == Op_If && |
|
733 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { |
|
734 if( cmp->in(2) != NULL && // make sure cmp is not already dead |
|
735 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { |
|
736 dist = 64; // Limit for null-pointer scans |
|
737 } else { |
|
738 dist = 4; // Do not bother for random pointer tests |
|
739 } |
|
740 } else { |
|
741 dist = 4; // Limit for random junky scans |
|
742 } |
|
743 |
|
744 // Normal equivalent-test check. |
|
745 if( !dom ) return NULL; // Dead loop? |
|
746 |
|
747 // Search up the dominator tree for an If with an identical test |
|
748 while( dom->Opcode() != op || // Not same opcode? |
|
749 dom->in(1) != in(1) || // Not same input 1? |
|
750 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? |
|
751 prev_dom->in(0) != dom ) { // One path of test does not dominate? |
|
752 if( dist < 0 ) return NULL; |
|
753 |
|
754 dist--; |
|
755 prev_dom = dom; |
|
756 dom = up_one_dom( dom ); |
|
757 if( !dom ) return NULL; |
|
758 } |
|
759 |
|
760 // Check that we did not follow a loop back to ourselves |
|
761 if( this == dom ) |
|
762 return NULL; |
|
763 |
|
764 if( dist > 2 ) // Add to count of NULL checks elided |
|
765 explicit_null_checks_elided++; |
|
766 |
|
767 } // End of Else scan for an equivalent test |
|
768 |
|
769 // Hit! Remove this IF |
|
770 #ifndef PRODUCT |
|
771 if( TraceIterativeGVN ) { |
|
772 tty->print(" Removing IfNode: "); this->dump(); |
|
773 } |
|
774 if( VerifyOpto && !phase->allow_progress() ) { |
|
775 // Found an equivalent dominating test, |
|
776 // we can not guarantee reaching a fix-point for these during iterativeGVN |
|
777 // since intervening nodes may not change. |
|
778 return NULL; |
|
779 } |
|
780 #endif |
|
781 |
|
782 // Replace dominated IfNode |
|
783 dominated_by( prev_dom, igvn ); |
|
784 |
|
785 // Must return either the original node (now dead) or a new node |
|
786 // (Do not return a top here, since that would break the uniqueness of top.) |
|
787 return new (phase->C, 1) ConINode(TypeInt::ZERO); |
|
788 } |
|
789 |
|
790 //------------------------------dominated_by----------------------------------- |
|
791 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) { |
|
792 igvn->hash_delete(this); // Remove self to prevent spurious V-N |
|
793 Node *idom = in(0); |
|
794 // Need opcode to decide which way 'this' test goes |
|
795 int prev_op = prev_dom->Opcode(); |
|
796 Node *top = igvn->C->top(); // Shortcut to top |
|
797 |
|
798 // Now walk the current IfNode's projections. |
|
799 // Loop ends when 'this' has no more uses. |
|
800 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { |
|
801 Node *ifp = last_out(i); // Get IfTrue/IfFalse |
|
802 igvn->add_users_to_worklist(ifp); |
|
803 // Check which projection it is and set target. |
|
804 // Data-target is either the dominating projection of the same type |
|
805 // or TOP if the dominating projection is of opposite type. |
|
806 // Data-target will be used as the new control edge for the non-CFG |
|
807 // nodes like Casts and Loads. |
|
808 Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top; |
|
809 // Control-target is just the If's immediate dominator or TOP. |
|
810 Node *ctrl_target = (ifp->Opcode() == prev_op ) ? idom : top; |
|
811 |
|
812 // For each child of an IfTrue/IfFalse projection, reroute. |
|
813 // Loop ends when projection has no more uses. |
|
814 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { |
|
815 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse |
|
816 igvn->hash_delete(s); // Yank from hash table before edge hacking |
|
817 if( !s->depends_only_on_test() ) { |
|
818 // Find the control input matching this def-use edge. |
|
819 // For Regions it may not be in slot 0. |
|
820 uint l; |
|
821 for( l = 0; s->in(l) != ifp; l++ ) { } |
|
822 s->set_req(l, ctrl_target); |
|
823 } else { // Else, for control producers, |
|
824 s->set_req(0, data_target); // Move child to data-target |
|
825 } |
|
826 igvn->_worklist.push(s); // Revisit collapsed Phis |
|
827 } // End for each child of a projection |
|
828 |
|
829 igvn->remove_dead_node(ifp); |
|
830 } // End for each IfTrue/IfFalse child of If |
|
831 |
|
832 // Kill the IfNode |
|
833 igvn->remove_dead_node(this); |
|
834 } |
|
835 |
|
836 //------------------------------Identity--------------------------------------- |
|
837 // If the test is constant & we match, then we are the input Control |
|
838 Node *IfTrueNode::Identity( PhaseTransform *phase ) { |
|
839 // Can only optimize if cannot go the other way |
|
840 const TypeTuple *t = phase->type(in(0))->is_tuple(); |
|
841 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE ) |
|
842 ? in(0)->in(0) // IfNode control |
|
843 : this; // no progress |
|
844 } |
|
845 |
|
846 //------------------------------dump_spec-------------------------------------- |
|
847 #ifndef PRODUCT |
|
848 void IfNode::dump_spec(outputStream *st) const { |
|
849 st->print("P=%f, C=%f",_prob,_fcnt); |
|
850 } |
|
851 #endif |
|
852 |
|
853 //------------------------------idealize_test---------------------------------- |
|
854 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and |
|
855 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms |
|
856 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as |
|
857 // needed. |
|
858 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { |
|
859 assert(iff->in(0) != NULL, "If must be live"); |
|
860 |
|
861 if (iff->outcnt() != 2) return NULL; // Malformed projections. |
|
862 Node* old_if_f = iff->proj_out(false); |
|
863 Node* old_if_t = iff->proj_out(true); |
|
864 |
|
865 // CountedLoopEnds want the back-control test to be TRUE, irregardless of |
|
866 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition |
|
867 // happens in count-down loops |
|
868 if (iff->is_CountedLoopEnd()) return NULL; |
|
869 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests |
|
870 BoolNode *b = iff->in(1)->as_Bool(); |
|
871 BoolTest bt = b->_test; |
|
872 // Test already in good order? |
|
873 if( bt.is_canonical() ) |
|
874 return NULL; |
|
875 |
|
876 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and |
|
877 // cloning the IfNode. |
|
878 Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) ); |
|
879 if( !new_b->is_Bool() ) return NULL; |
|
880 b = new_b->as_Bool(); |
|
881 |
|
882 PhaseIterGVN *igvn = phase->is_IterGVN(); |
|
883 assert( igvn, "Test is not canonical in parser?" ); |
|
884 |
|
885 // The IF node never really changes, but it needs to be cloned |
|
886 iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt); |
|
887 |
|
888 Node *prior = igvn->hash_find_insert(iff); |
|
889 if( prior ) { |
|
890 igvn->remove_dead_node(iff); |
|
891 iff = (IfNode*)prior; |
|
892 } else { |
|
893 // Cannot call transform on it just yet |
|
894 igvn->set_type_bottom(iff); |
|
895 } |
|
896 igvn->_worklist.push(iff); |
|
897 |
|
898 // Now handle projections. Cloning not required. |
|
899 Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff )); |
|
900 Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff )); |
|
901 |
|
902 igvn->register_new_node_with_optimizer(new_if_f); |
|
903 igvn->register_new_node_with_optimizer(new_if_t); |
|
904 igvn->hash_delete(old_if_f); |
|
905 igvn->hash_delete(old_if_t); |
|
906 // Flip test, so flip trailing control |
|
907 igvn->subsume_node(old_if_f, new_if_t); |
|
908 igvn->subsume_node(old_if_t, new_if_f); |
|
909 |
|
910 // Progress |
|
911 return iff; |
|
912 } |
|
913 |
|
914 //------------------------------Identity--------------------------------------- |
|
915 // If the test is constant & we match, then we are the input Control |
|
916 Node *IfFalseNode::Identity( PhaseTransform *phase ) { |
|
917 // Can only optimize if cannot go the other way |
|
918 const TypeTuple *t = phase->type(in(0))->is_tuple(); |
|
919 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE ) |
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920 ? in(0)->in(0) // IfNode control |
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921 : this; // no progress |
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922 } |