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0
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1 /* Natural loop functions
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2 Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
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3 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
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4
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5 This file is part of GCC.
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6
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7 GCC is free software; you can redistribute it and/or modify it under
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8 the terms of the GNU General Public License as published by the Free
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9 Software Foundation; either version 3, or (at your option) any later
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10 version.
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11
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12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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15 for more details.
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16
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17 You should have received a copy of the GNU General Public License
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18 along with GCC; see the file COPYING3. If not see
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19 <http://www.gnu.org/licenses/>. */
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20
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21 #ifndef GCC_CFGLOOP_H
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22 #define GCC_CFGLOOP_H
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23
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24 #include "basic-block.h"
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25 /* For rtx_code. */
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26 #include "rtl.h"
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27 #include "vecprim.h"
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28 #include "double-int.h"
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29
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30 /* Structure to hold decision about unrolling/peeling. */
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31 enum lpt_dec
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32 {
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33 LPT_NONE,
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34 LPT_PEEL_COMPLETELY,
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35 LPT_PEEL_SIMPLE,
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36 LPT_UNROLL_CONSTANT,
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37 LPT_UNROLL_RUNTIME,
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38 LPT_UNROLL_STUPID
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39 };
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40
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41 struct lpt_decision GTY (())
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42 {
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43 enum lpt_dec decision;
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44 unsigned times;
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45 };
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46
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47 /* The structure describing a bound on number of iterations of a loop. */
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48
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49 struct nb_iter_bound GTY ((chain_next ("%h.next")))
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50 {
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51 /* The statement STMT is executed at most ... */
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52 gimple stmt;
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53
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54 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
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55 The + 1 is added for the following reasons:
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56
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57 a) 0 would otherwise be unused, while we would need to care more about
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58 overflows (as MAX + 1 is sometimes produced as the estimate on number
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59 of executions of STMT).
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60 b) it is consistent with the result of number_of_iterations_exit. */
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61 double_int bound;
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62
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63 /* True if the statement will cause the loop to be leaved the (at most)
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64 BOUND + 1-st time it is executed, that is, all the statements after it
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65 are executed at most BOUND times. */
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66 bool is_exit;
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67
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68 /* The next bound in the list. */
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69 struct nb_iter_bound *next;
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70 };
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71
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72 /* Description of the loop exit. */
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73
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74 struct loop_exit GTY (())
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75 {
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76 /* The exit edge. */
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77 struct edge_def *e;
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78
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79 /* Previous and next exit in the list of the exits of the loop. */
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80 struct loop_exit *prev;
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81 struct loop_exit *next;
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82
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83 /* Next element in the list of loops from that E exits. */
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84 struct loop_exit *next_e;
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85 };
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86
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87 typedef struct loop *loop_p;
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88 DEF_VEC_P (loop_p);
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89 DEF_VEC_ALLOC_P (loop_p, heap);
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90 DEF_VEC_ALLOC_P (loop_p, gc);
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91
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92 /* An integer estimation of the number of iterations. Estimate_state
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93 describes what is the state of the estimation. */
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94 enum loop_estimation
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95 {
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96 /* Estimate was not computed yet. */
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97 EST_NOT_COMPUTED,
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98 /* Estimate is ready. */
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99 EST_AVAILABLE
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100 };
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101
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102 /* Structure to hold information for each natural loop. */
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103 struct loop GTY ((chain_next ("%h.next")))
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104 {
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105 /* Index into loops array. */
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106 int num;
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107
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108 /* Number of loop insns. */
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109 unsigned ninsns;
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110
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111 /* Basic block of loop header. */
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112 struct basic_block_def *header;
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113
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114 /* Basic block of loop latch. */
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115 struct basic_block_def *latch;
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116
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117 /* For loop unrolling/peeling decision. */
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118 struct lpt_decision lpt_decision;
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119
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120 /* Average number of executed insns per iteration. */
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121 unsigned av_ninsns;
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122
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123 /* Number of blocks contained within the loop. */
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124 unsigned num_nodes;
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125
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126 /* Superloops of the loop, starting with the outermost loop. */
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127 VEC (loop_p, gc) *superloops;
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128
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129 /* The first inner (child) loop or NULL if innermost loop. */
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130 struct loop *inner;
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131
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132 /* Link to the next (sibling) loop. */
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133 struct loop *next;
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134
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135 /* Auxiliary info specific to a pass. */
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136 PTR GTY ((skip (""))) aux;
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137
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138 /* The number of times the latch of the loop is executed.
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139 This is an INTEGER_CST or an expression containing symbolic
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140 names. Don't access this field directly:
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141 number_of_latch_executions computes and caches the computed
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142 information in this field. */
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143 tree nb_iterations;
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144
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145 /* An integer guaranteed to bound the number of iterations of the loop
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146 from above. */
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147 double_int nb_iterations_upper_bound;
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148
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149 /* An integer giving the expected number of iterations of the loop. */
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150 double_int nb_iterations_estimate;
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151
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152 bool any_upper_bound;
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153 bool any_estimate;
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154
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155 /* An integer estimation of the number of iterations. Estimate_state
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156 describes what is the state of the estimation. */
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157 enum loop_estimation estimate_state;
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158
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159 /* Upper bound on number of iterations of a loop. */
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160 struct nb_iter_bound *bounds;
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161
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162 /* Head of the cyclic list of the exits of the loop. */
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163 struct loop_exit *exits;
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164 };
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165
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166 /* Flags for state of loop structure. */
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167 enum
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168 {
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169 LOOPS_HAVE_PREHEADERS = 1,
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170 LOOPS_HAVE_SIMPLE_LATCHES = 2,
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171 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
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172 LOOPS_HAVE_RECORDED_EXITS = 8,
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173 LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
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174 LOOP_CLOSED_SSA = 32,
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175 LOOPS_NEED_FIXUP = 64,
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176 LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
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177 };
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178
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179 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
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180 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
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181 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
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182
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183 /* Structure to hold CFG information about natural loops within a function. */
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184 struct loops GTY (())
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185 {
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186 /* State of loops. */
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187 int state;
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188
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189 /* Array of the loops. */
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190 VEC (loop_p, gc) *larray;
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191
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192 /* Maps edges to the list of their descriptions as loop exits. Edges
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193 whose sources or destinations have loop_father == NULL (which may
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194 happen during the cfg manipulations) should not appear in EXITS. */
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195 htab_t GTY((param_is (struct loop_exit))) exits;
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196
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197 /* Pointer to root of loop hierarchy tree. */
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198 struct loop *tree_root;
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199 };
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200
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201 /* Loop recognition. */
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202 extern int flow_loops_find (struct loops *);
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203 extern void disambiguate_loops_with_multiple_latches (void);
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204 extern void flow_loops_free (struct loops *);
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205 extern void flow_loops_dump (FILE *,
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206 void (*)(const struct loop *, FILE *, int), int);
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207 extern void flow_loop_dump (const struct loop *, FILE *,
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208 void (*)(const struct loop *, FILE *, int), int);
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209 struct loop *alloc_loop (void);
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210 extern void flow_loop_free (struct loop *);
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211 int flow_loop_nodes_find (basic_block, struct loop *);
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212 void fix_loop_structure (bitmap changed_bbs);
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213 void mark_irreducible_loops (void);
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214 void release_recorded_exits (void);
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215 void record_loop_exits (void);
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216 void rescan_loop_exit (edge, bool, bool);
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217
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218 /* Loop data structure manipulation/querying. */
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219 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
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220 extern void flow_loop_tree_node_remove (struct loop *);
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221 extern void add_loop (struct loop *, struct loop *);
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222 extern bool flow_loop_nested_p (const struct loop *, const struct loop *);
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223 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
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224 extern struct loop * find_common_loop (struct loop *, struct loop *);
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225 struct loop *superloop_at_depth (struct loop *, unsigned);
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226 struct eni_weights_d;
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227 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
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228 extern int num_loop_insns (const struct loop *);
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229 extern int average_num_loop_insns (const struct loop *);
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230 extern unsigned get_loop_level (const struct loop *);
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231 extern bool loop_exit_edge_p (const struct loop *, const_edge);
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232 extern bool is_loop_exit (struct loop *, basic_block);
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233 extern void mark_loop_exit_edges (void);
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234
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235 /* Loops & cfg manipulation. */
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236 extern basic_block *get_loop_body (const struct loop *);
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237 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
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238 unsigned);
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239 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
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240 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
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241 extern basic_block *get_loop_body_in_custom_order (const struct loop *,
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242 int (*) (const void *, const void *));
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243
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244 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
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245 edge single_exit (const struct loop *);
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246 extern unsigned num_loop_branches (const struct loop *);
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247
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248 extern edge loop_preheader_edge (const struct loop *);
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249 extern edge loop_latch_edge (const struct loop *);
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250
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251 extern void add_bb_to_loop (basic_block, struct loop *);
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252 extern void remove_bb_from_loops (basic_block);
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253
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254 extern void cancel_loop_tree (struct loop *);
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255 extern void delete_loop (struct loop *);
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256
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257 enum
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258 {
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259 CP_SIMPLE_PREHEADERS = 1,
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260 CP_FALLTHRU_PREHEADERS = 2
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261 };
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262
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263 basic_block create_preheader (struct loop *, int);
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264 extern void create_preheaders (int);
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265 extern void force_single_succ_latches (void);
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266
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267 extern void verify_loop_structure (void);
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268
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269 /* Loop analysis. */
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270 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
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271 gcov_type expected_loop_iterations_unbounded (const struct loop *);
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272 extern unsigned expected_loop_iterations (const struct loop *);
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273 extern rtx doloop_condition_get (rtx);
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274
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275 void estimate_numbers_of_iterations_loop (struct loop *);
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276 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
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277 bool estimated_loop_iterations (struct loop *, bool, double_int *);
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278
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279 /* Loop manipulation. */
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280 extern bool can_duplicate_loop_p (const struct loop *loop);
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281
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282 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
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283 duplicate_loop_to_header_edge. */
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284 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
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285 field of newly create BB. */
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286 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
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287 a complete peeling. */
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288
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289 extern edge create_empty_if_region_on_edge (edge, tree);
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290 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
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291 tree *, struct loop *);
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292 extern struct loop * duplicate_loop (struct loop *, struct loop *);
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293 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
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294 unsigned, sbitmap, edge,
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295 VEC (edge, heap) **, int);
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296 extern struct loop *loopify (edge, edge,
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297 basic_block, edge, edge, bool,
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298 unsigned, unsigned);
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299 struct loop * loop_version (struct loop *, void *,
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300 basic_block *, unsigned, unsigned, unsigned, bool);
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301 extern bool remove_path (edge);
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302 void scale_loop_frequencies (struct loop *, int, int);
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303
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304 /* Induction variable analysis. */
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305
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306 /* The description of induction variable. The things are a bit complicated
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307 due to need to handle subregs and extends. The value of the object described
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308 by it can be obtained as follows (all computations are done in extend_mode):
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309
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310 Value in i-th iteration is
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311 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
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312
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313 If first_special is true, the value in the first iteration is
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314 delta + mult * base
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315
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316 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
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317 subreg_{mode} (base + i * step)
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318
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319 The get_iv_value function can be used to obtain these expressions.
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320
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321 ??? Add a third mode field that would specify the mode in that inner
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322 computation is done, which would enable it to be different from the
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323 outer one? */
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324
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325 struct rtx_iv
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326 {
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327 /* Its base and step (mode of base and step is supposed to be extend_mode,
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328 see the description above). */
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329 rtx base, step;
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330
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331 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
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332 enum rtx_code extend;
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333
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334 /* Operations applied in the extended mode. */
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335 rtx delta, mult;
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336
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337 /* The mode it is extended to. */
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338 enum machine_mode extend_mode;
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339
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340 /* The mode the variable iterates in. */
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341 enum machine_mode mode;
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342
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343 /* Whether the first iteration needs to be handled specially. */
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344 unsigned first_special : 1;
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345 };
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346
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347 /* The description of an exit from the loop and of the number of iterations
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348 till we take the exit. */
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349
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350 struct niter_desc
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351 {
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352 /* The edge out of the loop. */
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353 edge out_edge;
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354
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355 /* The other edge leading from the condition. */
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356 edge in_edge;
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357
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358 /* True if we are able to say anything about number of iterations of the
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359 loop. */
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360 bool simple_p;
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361
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362 /* True if the loop iterates the constant number of times. */
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363 bool const_iter;
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364
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365 /* Number of iterations if constant. */
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366 unsigned HOST_WIDEST_INT niter;
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367
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368 /* Upper bound on the number of iterations. */
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369 unsigned HOST_WIDEST_INT niter_max;
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370
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371 /* Assumptions under that the rest of the information is valid. */
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372 rtx assumptions;
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373
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374 /* Assumptions under that the loop ends before reaching the latch,
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375 even if value of niter_expr says otherwise. */
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376 rtx noloop_assumptions;
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377
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378 /* Condition under that the loop is infinite. */
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379 rtx infinite;
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380
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381 /* Whether the comparison is signed. */
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382 bool signed_p;
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383
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384 /* The mode in that niter_expr should be computed. */
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385 enum machine_mode mode;
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386
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387 /* The number of iterations of the loop. */
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388 rtx niter_expr;
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389 };
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390
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391 extern void iv_analysis_loop_init (struct loop *);
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392 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
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393 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
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394 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
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395 extern rtx get_iv_value (struct rtx_iv *, rtx);
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396 extern bool biv_p (rtx, rtx);
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397 extern void find_simple_exit (struct loop *, struct niter_desc *);
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398 extern void iv_analysis_done (void);
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399
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400 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
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401 extern void free_simple_loop_desc (struct loop *loop);
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402
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403 static inline struct niter_desc *
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404 simple_loop_desc (struct loop *loop)
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405 {
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406 return (struct niter_desc *) loop->aux;
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407 }
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408
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409 /* Accessors for the loop structures. */
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410
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411 /* Returns the loop with index NUM from current_loops. */
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412
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413 static inline struct loop *
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414 get_loop (unsigned num)
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415 {
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416 return VEC_index (loop_p, current_loops->larray, num);
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417 }
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418
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419 /* Returns the number of superloops of LOOP. */
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420
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421 static inline unsigned
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422 loop_depth (const struct loop *loop)
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423 {
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424 return VEC_length (loop_p, loop->superloops);
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425 }
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426
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427 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
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428 loop. */
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429
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430 static inline struct loop *
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431 loop_outer (const struct loop *loop)
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432 {
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433 unsigned n = VEC_length (loop_p, loop->superloops);
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434
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435 if (n == 0)
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436 return NULL;
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437
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438 return VEC_index (loop_p, loop->superloops, n - 1);
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439 }
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440
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441 /* Returns the list of loops in current_loops. */
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442
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443 static inline VEC (loop_p, gc) *
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444 get_loops (void)
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445 {
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446 if (!current_loops)
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447 return NULL;
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448
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449 return current_loops->larray;
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450 }
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451
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452 /* Returns the number of loops in current_loops (including the removed
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453 ones and the fake loop that forms the root of the loop tree). */
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454
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455 static inline unsigned
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456 number_of_loops (void)
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457 {
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458 if (!current_loops)
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459 return 0;
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460
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461 return VEC_length (loop_p, current_loops->larray);
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462 }
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463
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464 /* Returns true if state of the loops satisfies all properties
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465 described by FLAGS. */
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466
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467 static inline bool
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468 loops_state_satisfies_p (unsigned flags)
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469 {
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470 return (current_loops->state & flags) == flags;
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471 }
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472
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473 /* Sets FLAGS to the loops state. */
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474
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475 static inline void
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476 loops_state_set (unsigned flags)
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477 {
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478 current_loops->state |= flags;
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479 }
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480
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481 /* Clears FLAGS from the loops state. */
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482
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483 static inline void
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484 loops_state_clear (unsigned flags)
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485 {
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486 if (!current_loops)
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487 return;
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488 current_loops->state &= ~flags;
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489 }
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490
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491 /* Loop iterators. */
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492
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493 /* Flags for loop iteration. */
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494
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495 enum li_flags
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496 {
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497 LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */
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498 LI_FROM_INNERMOST = 2, /* Iterate over the loops in the reverse order,
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499 starting from innermost ones. */
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500 LI_ONLY_INNERMOST = 4 /* Iterate only over innermost loops. */
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501 };
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502
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503 /* The iterator for loops. */
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504
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505 typedef struct
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506 {
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507 /* The list of loops to visit. */
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508 VEC(int,heap) *to_visit;
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509
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510 /* The index of the actual loop. */
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511 unsigned idx;
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512 } loop_iterator;
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513
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514 static inline void
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515 fel_next (loop_iterator *li, loop_p *loop)
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516 {
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517 int anum;
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518
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519 while (VEC_iterate (int, li->to_visit, li->idx, anum))
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520 {
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521 li->idx++;
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522 *loop = get_loop (anum);
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523 if (*loop)
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524 return;
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525 }
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526
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527 VEC_free (int, heap, li->to_visit);
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528 *loop = NULL;
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529 }
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530
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531 static inline void
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532 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
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533 {
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534 struct loop *aloop;
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535 unsigned i;
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536 int mn;
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537
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538 li->idx = 0;
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539 if (!current_loops)
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540 {
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541 li->to_visit = NULL;
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542 *loop = NULL;
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543 return;
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544 }
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545
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546 li->to_visit = VEC_alloc (int, heap, number_of_loops ());
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547 mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
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548
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549 if (flags & LI_ONLY_INNERMOST)
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550 {
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551 for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
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552 if (aloop != NULL
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553 && aloop->inner == NULL
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554 && aloop->num >= mn)
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555 VEC_quick_push (int, li->to_visit, aloop->num);
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556 }
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557 else if (flags & LI_FROM_INNERMOST)
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558 {
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559 /* Push the loops to LI->TO_VISIT in postorder. */
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560 for (aloop = current_loops->tree_root;
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561 aloop->inner != NULL;
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562 aloop = aloop->inner)
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563 continue;
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564
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565 while (1)
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566 {
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567 if (aloop->num >= mn)
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568 VEC_quick_push (int, li->to_visit, aloop->num);
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569
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570 if (aloop->next)
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571 {
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572 for (aloop = aloop->next;
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573 aloop->inner != NULL;
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574 aloop = aloop->inner)
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575 continue;
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576 }
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577 else if (!loop_outer (aloop))
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578 break;
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579 else
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580 aloop = loop_outer (aloop);
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581 }
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582 }
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583 else
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584 {
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585 /* Push the loops to LI->TO_VISIT in preorder. */
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586 aloop = current_loops->tree_root;
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587 while (1)
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588 {
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589 if (aloop->num >= mn)
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590 VEC_quick_push (int, li->to_visit, aloop->num);
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591
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592 if (aloop->inner != NULL)
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593 aloop = aloop->inner;
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594 else
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595 {
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596 while (aloop != NULL && aloop->next == NULL)
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597 aloop = loop_outer (aloop);
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598 if (aloop == NULL)
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599 break;
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600 aloop = aloop->next;
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601 }
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602 }
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603 }
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604
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605 fel_next (li, loop);
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606 }
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607
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608 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
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609 for (fel_init (&(LI), &(LOOP), FLAGS); \
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610 (LOOP); \
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611 fel_next (&(LI), &(LOOP)))
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612
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613 #define FOR_EACH_LOOP_BREAK(LI) \
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614 { \
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615 VEC_free (int, heap, (LI)->to_visit); \
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616 break; \
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617 }
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618
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619 /* The properties of the target. */
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620
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621 extern unsigned target_avail_regs;
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622 extern unsigned target_res_regs;
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623 extern unsigned target_reg_cost [2];
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624 extern unsigned target_spill_cost [2];
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625
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626 /* Register pressure estimation for induction variable optimizations & loop
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627 invariant motion. */
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628 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
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629 extern void init_set_costs (void);
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630
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631 /* Loop optimizer initialization. */
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632 extern void loop_optimizer_init (unsigned);
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633 extern void loop_optimizer_finalize (void);
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634
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635 /* Optimization passes. */
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636 extern void unswitch_loops (void);
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637
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638 enum
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639 {
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640 UAP_PEEL = 1, /* Enables loop peeling. */
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641 UAP_UNROLL = 2, /* Enables unrolling of loops if it seems profitable. */
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642 UAP_UNROLL_ALL = 4 /* Enables unrolling of all loops. */
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643 };
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644
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645 extern void unroll_and_peel_loops (int);
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646 extern void doloop_optimize_loops (void);
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647 extern void move_loop_invariants (void);
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648
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649 #endif /* GCC_CFGLOOP_H */
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