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0
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1 /* Branch prediction routines for the GNU compiler.
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2 Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008
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3 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 /* References:
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22
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23 [1] "Branch Prediction for Free"
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24 Ball and Larus; PLDI '93.
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25 [2] "Static Branch Frequency and Program Profile Analysis"
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26 Wu and Larus; MICRO-27.
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27 [3] "Corpus-based Static Branch Prediction"
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28 Calder, Grunwald, Lindsay, Martin, Mozer, and Zorn; PLDI '95. */
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29
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30
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31 #include "config.h"
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32 #include "system.h"
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33 #include "coretypes.h"
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34 #include "tm.h"
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35 #include "tree.h"
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36 #include "rtl.h"
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37 #include "tm_p.h"
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38 #include "hard-reg-set.h"
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39 #include "basic-block.h"
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40 #include "insn-config.h"
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41 #include "regs.h"
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42 #include "flags.h"
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43 #include "output.h"
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44 #include "function.h"
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45 #include "except.h"
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46 #include "toplev.h"
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47 #include "recog.h"
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48 #include "expr.h"
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49 #include "predict.h"
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50 #include "coverage.h"
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51 #include "sreal.h"
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52 #include "params.h"
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53 #include "target.h"
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54 #include "cfgloop.h"
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55 #include "tree-flow.h"
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56 #include "ggc.h"
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57 #include "tree-dump.h"
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58 #include "tree-pass.h"
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59 #include "timevar.h"
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60 #include "tree-scalar-evolution.h"
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61 #include "cfgloop.h"
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62 #include "pointer-set.h"
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63
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64 /* real constants: 0, 1, 1-1/REG_BR_PROB_BASE, REG_BR_PROB_BASE,
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65 1/REG_BR_PROB_BASE, 0.5, BB_FREQ_MAX. */
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66 static sreal real_zero, real_one, real_almost_one, real_br_prob_base,
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67 real_inv_br_prob_base, real_one_half, real_bb_freq_max;
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68
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69 /* Random guesstimation given names.
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70 PROV_VERY_UNLIKELY should be small enough so basic block predicted
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71 by it gets bellow HOT_BB_FREQUENCY_FRANCTION. */
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72 #define PROB_VERY_UNLIKELY (REG_BR_PROB_BASE / 2000 - 1)
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73 #define PROB_EVEN (REG_BR_PROB_BASE / 2)
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74 #define PROB_VERY_LIKELY (REG_BR_PROB_BASE - PROB_VERY_UNLIKELY)
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75 #define PROB_ALWAYS (REG_BR_PROB_BASE)
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76
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77 static void combine_predictions_for_insn (rtx, basic_block);
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78 static void dump_prediction (FILE *, enum br_predictor, int, basic_block, int);
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79 static void predict_paths_leading_to (basic_block, enum br_predictor, enum prediction);
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80 static void compute_function_frequency (void);
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81 static void choose_function_section (void);
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82 static bool can_predict_insn_p (const_rtx);
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83
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84 /* Information we hold about each branch predictor.
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85 Filled using information from predict.def. */
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86
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87 struct predictor_info
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88 {
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89 const char *const name; /* Name used in the debugging dumps. */
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90 const int hitrate; /* Expected hitrate used by
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91 predict_insn_def call. */
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92 const int flags;
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93 };
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94
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95 /* Use given predictor without Dempster-Shaffer theory if it matches
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96 using first_match heuristics. */
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97 #define PRED_FLAG_FIRST_MATCH 1
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98
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99 /* Recompute hitrate in percent to our representation. */
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100
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101 #define HITRATE(VAL) ((int) ((VAL) * REG_BR_PROB_BASE + 50) / 100)
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102
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103 #define DEF_PREDICTOR(ENUM, NAME, HITRATE, FLAGS) {NAME, HITRATE, FLAGS},
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104 static const struct predictor_info predictor_info[]= {
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105 #include "predict.def"
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106
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107 /* Upper bound on predictors. */
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108 {NULL, 0, 0}
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109 };
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110 #undef DEF_PREDICTOR
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111
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112 /* Return TRUE if frequency FREQ is considered to be hot. */
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113
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114 static inline bool
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115 maybe_hot_frequency_p (int freq)
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116 {
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117 if (!profile_info || !flag_branch_probabilities)
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118 {
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119 if (cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED)
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120 return false;
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121 if (cfun->function_frequency == FUNCTION_FREQUENCY_HOT)
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122 return true;
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123 }
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124 if (profile_status == PROFILE_ABSENT)
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125 return true;
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126 if (freq < BB_FREQ_MAX / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION))
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127 return false;
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128 return true;
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129 }
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130
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131 /* Return TRUE if frequency FREQ is considered to be hot. */
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132
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133 static inline bool
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134 maybe_hot_count_p (gcov_type count)
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135 {
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136 if (profile_status != PROFILE_READ)
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137 return true;
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138 /* Code executed at most once is not hot. */
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139 if (profile_info->runs >= count)
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140 return false;
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141 return (count
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142 > profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION));
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143 }
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144
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145 /* Return true in case BB can be CPU intensive and should be optimized
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146 for maximal performance. */
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147
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148 bool
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149 maybe_hot_bb_p (const_basic_block bb)
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150 {
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151 if (profile_status == PROFILE_READ)
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152 return maybe_hot_count_p (bb->count);
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153 return maybe_hot_frequency_p (bb->frequency);
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154 }
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155
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156 /* Return true if the call can be hot. */
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157
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158 bool
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159 cgraph_maybe_hot_edge_p (struct cgraph_edge *edge)
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160 {
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161 if (profile_info && flag_branch_probabilities
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162 && (edge->count
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163 <= profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION)))
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164 return false;
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165 if (lookup_attribute ("cold", DECL_ATTRIBUTES (edge->callee->decl))
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166 || lookup_attribute ("cold", DECL_ATTRIBUTES (edge->caller->decl)))
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167 return false;
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168 if (lookup_attribute ("hot", DECL_ATTRIBUTES (edge->caller->decl)))
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169 return true;
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170 if (flag_guess_branch_prob
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171 && edge->frequency < (CGRAPH_FREQ_MAX
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172 / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION)))
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173 return false;
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174 return true;
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175 }
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176
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177 /* Return true in case BB can be CPU intensive and should be optimized
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178 for maximal performance. */
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179
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180 bool
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181 maybe_hot_edge_p (edge e)
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182 {
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183 if (profile_status == PROFILE_READ)
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184 return maybe_hot_count_p (e->count);
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185 return maybe_hot_frequency_p (EDGE_FREQUENCY (e));
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186 }
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187
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188 /* Return true in case BB is probably never executed. */
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189 bool
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190 probably_never_executed_bb_p (const_basic_block bb)
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191 {
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192 if (profile_info && flag_branch_probabilities)
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193 return ((bb->count + profile_info->runs / 2) / profile_info->runs) == 0;
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194 if ((!profile_info || !flag_branch_probabilities)
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195 && cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED)
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196 return true;
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197 return false;
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198 }
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199
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200 /* Return true when current function should always be optimized for size. */
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201
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202 bool
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203 optimize_function_for_size_p (struct function *fun)
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204 {
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205 return (optimize_size
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206 || (fun && (fun->function_frequency
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207 == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED)));
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208 }
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209
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210 /* Return true when current function should always be optimized for speed. */
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211
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212 bool
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213 optimize_function_for_speed_p (struct function *fun)
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214 {
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215 return !optimize_function_for_size_p (fun);
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216 }
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217
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218 /* Return TRUE when BB should be optimized for size. */
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219
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220 bool
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221 optimize_bb_for_size_p (const_basic_block bb)
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222 {
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223 return optimize_function_for_size_p (cfun) || !maybe_hot_bb_p (bb);
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224 }
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225
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226 /* Return TRUE when BB should be optimized for speed. */
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227
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228 bool
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229 optimize_bb_for_speed_p (const_basic_block bb)
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230 {
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231 return !optimize_bb_for_size_p (bb);
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232 }
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233
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234 /* Return TRUE when BB should be optimized for size. */
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235
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236 bool
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237 optimize_edge_for_size_p (edge e)
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238 {
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239 return optimize_function_for_size_p (cfun) || !maybe_hot_edge_p (e);
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240 }
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241
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242 /* Return TRUE when BB should be optimized for speed. */
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243
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244 bool
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245 optimize_edge_for_speed_p (edge e)
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246 {
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247 return !optimize_edge_for_size_p (e);
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248 }
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249
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250 /* Return TRUE when BB should be optimized for size. */
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251
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252 bool
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253 optimize_insn_for_size_p (void)
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254 {
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255 return optimize_function_for_size_p (cfun) || !crtl->maybe_hot_insn_p;
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256 }
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257
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258 /* Return TRUE when BB should be optimized for speed. */
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259
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260 bool
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261 optimize_insn_for_speed_p (void)
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262 {
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263 return !optimize_insn_for_size_p ();
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264 }
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265
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266 /* Return TRUE when LOOP should be optimized for size. */
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267
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268 bool
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269 optimize_loop_for_size_p (struct loop *loop)
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270 {
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271 return optimize_bb_for_size_p (loop->header);
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272 }
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273
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274 /* Return TRUE when LOOP should be optimized for speed. */
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275
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276 bool
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277 optimize_loop_for_speed_p (struct loop *loop)
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278 {
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279 return optimize_bb_for_speed_p (loop->header);
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280 }
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281
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282 /* Return TRUE when LOOP nest should be optimized for speed. */
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283
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284 bool
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285 optimize_loop_nest_for_speed_p (struct loop *loop)
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286 {
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287 struct loop *l = loop;
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288 if (optimize_loop_for_speed_p (loop))
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289 return true;
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290 l = loop->inner;
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291 while (l && l != loop)
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292 {
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293 if (optimize_loop_for_speed_p (l))
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294 return true;
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295 if (l->inner)
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296 l = l->inner;
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297 else if (l->next)
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298 l = l->next;
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299 else
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300 {
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301 while (l != loop && !l->next)
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302 l = loop_outer (l);
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303 if (l != loop)
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304 l = l->next;
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305 }
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306 }
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307 return false;
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308 }
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309
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310 /* Return TRUE when LOOP nest should be optimized for size. */
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311
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312 bool
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313 optimize_loop_nest_for_size_p (struct loop *loop)
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314 {
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315 return !optimize_loop_nest_for_speed_p (loop);
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316 }
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317
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318 /* Return true when edge E is likely to be well predictable by branch
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319 predictor. */
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320
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321 bool
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322 predictable_edge_p (edge e)
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323 {
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324 if (profile_status == PROFILE_ABSENT)
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325 return false;
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326 if ((e->probability
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327 <= PARAM_VALUE (PARAM_PREDICTABLE_BRANCH_OUTCOME) * REG_BR_PROB_BASE / 100)
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328 || (REG_BR_PROB_BASE - e->probability
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329 <= PARAM_VALUE (PARAM_PREDICTABLE_BRANCH_OUTCOME) * REG_BR_PROB_BASE / 100))
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330 return true;
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331 return false;
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332 }
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333
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334
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335 /* Set RTL expansion for BB profile. */
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336
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337 void
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338 rtl_profile_for_bb (basic_block bb)
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339 {
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340 crtl->maybe_hot_insn_p = maybe_hot_bb_p (bb);
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341 }
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342
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343 /* Set RTL expansion for edge profile. */
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344
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345 void
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346 rtl_profile_for_edge (edge e)
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347 {
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348 crtl->maybe_hot_insn_p = maybe_hot_edge_p (e);
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349 }
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350
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351 /* Set RTL expansion to default mode (i.e. when profile info is not known). */
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352 void
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353 default_rtl_profile (void)
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354 {
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355 crtl->maybe_hot_insn_p = true;
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356 }
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357
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358 /* Return true if the one of outgoing edges is already predicted by
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359 PREDICTOR. */
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360
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361 bool
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362 rtl_predicted_by_p (const_basic_block bb, enum br_predictor predictor)
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363 {
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364 rtx note;
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365 if (!INSN_P (BB_END (bb)))
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366 return false;
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367 for (note = REG_NOTES (BB_END (bb)); note; note = XEXP (note, 1))
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368 if (REG_NOTE_KIND (note) == REG_BR_PRED
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369 && INTVAL (XEXP (XEXP (note, 0), 0)) == (int)predictor)
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370 return true;
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371 return false;
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372 }
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373
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374 /* This map contains for a basic block the list of predictions for the
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375 outgoing edges. */
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376
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377 static struct pointer_map_t *bb_predictions;
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378
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379 /* Return true if the one of outgoing edges is already predicted by
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380 PREDICTOR. */
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381
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382 bool
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383 gimple_predicted_by_p (const_basic_block bb, enum br_predictor predictor)
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384 {
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385 struct edge_prediction *i;
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386 void **preds = pointer_map_contains (bb_predictions, bb);
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387
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388 if (!preds)
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389 return false;
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390
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391 for (i = (struct edge_prediction *) *preds; i; i = i->ep_next)
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392 if (i->ep_predictor == predictor)
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393 return true;
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394 return false;
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395 }
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396
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397 /* Return true when the probability of edge is reliable.
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398
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399 The profile guessing code is good at predicting branch outcome (ie.
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400 taken/not taken), that is predicted right slightly over 75% of time.
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401 It is however notoriously poor on predicting the probability itself.
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402 In general the profile appear a lot flatter (with probabilities closer
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403 to 50%) than the reality so it is bad idea to use it to drive optimization
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404 such as those disabling dynamic branch prediction for well predictable
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405 branches.
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406
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407 There are two exceptions - edges leading to noreturn edges and edges
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408 predicted by number of iterations heuristics are predicted well. This macro
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409 should be able to distinguish those, but at the moment it simply check for
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410 noreturn heuristic that is only one giving probability over 99% or bellow
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411 1%. In future we might want to propagate reliability information across the
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412 CFG if we find this information useful on multiple places. */
|
|
|
413 static bool
|
|
|
414 probability_reliable_p (int prob)
|
|
|
415 {
|
|
|
416 return (profile_status == PROFILE_READ
|
|
|
417 || (profile_status == PROFILE_GUESSED
|
|
|
418 && (prob <= HITRATE (1) || prob >= HITRATE (99))));
|
|
|
419 }
|
|
|
420
|
|
|
421 /* Same predicate as above, working on edges. */
|
|
|
422 bool
|
|
|
423 edge_probability_reliable_p (const_edge e)
|
|
|
424 {
|
|
|
425 return probability_reliable_p (e->probability);
|
|
|
426 }
|
|
|
427
|
|
|
428 /* Same predicate as edge_probability_reliable_p, working on notes. */
|
|
|
429 bool
|
|
|
430 br_prob_note_reliable_p (const_rtx note)
|
|
|
431 {
|
|
|
432 gcc_assert (REG_NOTE_KIND (note) == REG_BR_PROB);
|
|
|
433 return probability_reliable_p (INTVAL (XEXP (note, 0)));
|
|
|
434 }
|
|
|
435
|
|
|
436 static void
|
|
|
437 predict_insn (rtx insn, enum br_predictor predictor, int probability)
|
|
|
438 {
|
|
|
439 gcc_assert (any_condjump_p (insn));
|
|
|
440 if (!flag_guess_branch_prob)
|
|
|
441 return;
|
|
|
442
|
|
|
443 add_reg_note (insn, REG_BR_PRED,
|
|
|
444 gen_rtx_CONCAT (VOIDmode,
|
|
|
445 GEN_INT ((int) predictor),
|
|
|
446 GEN_INT ((int) probability)));
|
|
|
447 }
|
|
|
448
|
|
|
449 /* Predict insn by given predictor. */
|
|
|
450
|
|
|
451 void
|
|
|
452 predict_insn_def (rtx insn, enum br_predictor predictor,
|
|
|
453 enum prediction taken)
|
|
|
454 {
|
|
|
455 int probability = predictor_info[(int) predictor].hitrate;
|
|
|
456
|
|
|
457 if (taken != TAKEN)
|
|
|
458 probability = REG_BR_PROB_BASE - probability;
|
|
|
459
|
|
|
460 predict_insn (insn, predictor, probability);
|
|
|
461 }
|
|
|
462
|
|
|
463 /* Predict edge E with given probability if possible. */
|
|
|
464
|
|
|
465 void
|
|
|
466 rtl_predict_edge (edge e, enum br_predictor predictor, int probability)
|
|
|
467 {
|
|
|
468 rtx last_insn;
|
|
|
469 last_insn = BB_END (e->src);
|
|
|
470
|
|
|
471 /* We can store the branch prediction information only about
|
|
|
472 conditional jumps. */
|
|
|
473 if (!any_condjump_p (last_insn))
|
|
|
474 return;
|
|
|
475
|
|
|
476 /* We always store probability of branching. */
|
|
|
477 if (e->flags & EDGE_FALLTHRU)
|
|
|
478 probability = REG_BR_PROB_BASE - probability;
|
|
|
479
|
|
|
480 predict_insn (last_insn, predictor, probability);
|
|
|
481 }
|
|
|
482
|
|
|
483 /* Predict edge E with the given PROBABILITY. */
|
|
|
484 void
|
|
|
485 gimple_predict_edge (edge e, enum br_predictor predictor, int probability)
|
|
|
486 {
|
|
|
487 gcc_assert (profile_status != PROFILE_GUESSED);
|
|
|
488 if ((e->src != ENTRY_BLOCK_PTR && EDGE_COUNT (e->src->succs) > 1)
|
|
|
489 && flag_guess_branch_prob && optimize)
|
|
|
490 {
|
|
|
491 struct edge_prediction *i = XNEW (struct edge_prediction);
|
|
|
492 void **preds = pointer_map_insert (bb_predictions, e->src);
|
|
|
493
|
|
|
494 i->ep_next = (struct edge_prediction *) *preds;
|
|
|
495 *preds = i;
|
|
|
496 i->ep_probability = probability;
|
|
|
497 i->ep_predictor = predictor;
|
|
|
498 i->ep_edge = e;
|
|
|
499 }
|
|
|
500 }
|
|
|
501
|
|
|
502 /* Remove all predictions on given basic block that are attached
|
|
|
503 to edge E. */
|
|
|
504 void
|
|
|
505 remove_predictions_associated_with_edge (edge e)
|
|
|
506 {
|
|
|
507 void **preds;
|
|
|
508
|
|
|
509 if (!bb_predictions)
|
|
|
510 return;
|
|
|
511
|
|
|
512 preds = pointer_map_contains (bb_predictions, e->src);
|
|
|
513
|
|
|
514 if (preds)
|
|
|
515 {
|
|
|
516 struct edge_prediction **prediction = (struct edge_prediction **) preds;
|
|
|
517 struct edge_prediction *next;
|
|
|
518
|
|
|
519 while (*prediction)
|
|
|
520 {
|
|
|
521 if ((*prediction)->ep_edge == e)
|
|
|
522 {
|
|
|
523 next = (*prediction)->ep_next;
|
|
|
524 free (*prediction);
|
|
|
525 *prediction = next;
|
|
|
526 }
|
|
|
527 else
|
|
|
528 prediction = &((*prediction)->ep_next);
|
|
|
529 }
|
|
|
530 }
|
|
|
531 }
|
|
|
532
|
|
|
533 /* Clears the list of predictions stored for BB. */
|
|
|
534
|
|
|
535 static void
|
|
|
536 clear_bb_predictions (basic_block bb)
|
|
|
537 {
|
|
|
538 void **preds = pointer_map_contains (bb_predictions, bb);
|
|
|
539 struct edge_prediction *pred, *next;
|
|
|
540
|
|
|
541 if (!preds)
|
|
|
542 return;
|
|
|
543
|
|
|
544 for (pred = (struct edge_prediction *) *preds; pred; pred = next)
|
|
|
545 {
|
|
|
546 next = pred->ep_next;
|
|
|
547 free (pred);
|
|
|
548 }
|
|
|
549 *preds = NULL;
|
|
|
550 }
|
|
|
551
|
|
|
552 /* Return true when we can store prediction on insn INSN.
|
|
|
553 At the moment we represent predictions only on conditional
|
|
|
554 jumps, not at computed jump or other complicated cases. */
|
|
|
555 static bool
|
|
|
556 can_predict_insn_p (const_rtx insn)
|
|
|
557 {
|
|
|
558 return (JUMP_P (insn)
|
|
|
559 && any_condjump_p (insn)
|
|
|
560 && EDGE_COUNT (BLOCK_FOR_INSN (insn)->succs) >= 2);
|
|
|
561 }
|
|
|
562
|
|
|
563 /* Predict edge E by given predictor if possible. */
|
|
|
564
|
|
|
565 void
|
|
|
566 predict_edge_def (edge e, enum br_predictor predictor,
|
|
|
567 enum prediction taken)
|
|
|
568 {
|
|
|
569 int probability = predictor_info[(int) predictor].hitrate;
|
|
|
570
|
|
|
571 if (taken != TAKEN)
|
|
|
572 probability = REG_BR_PROB_BASE - probability;
|
|
|
573
|
|
|
574 predict_edge (e, predictor, probability);
|
|
|
575 }
|
|
|
576
|
|
|
577 /* Invert all branch predictions or probability notes in the INSN. This needs
|
|
|
578 to be done each time we invert the condition used by the jump. */
|
|
|
579
|
|
|
580 void
|
|
|
581 invert_br_probabilities (rtx insn)
|
|
|
582 {
|
|
|
583 rtx note;
|
|
|
584
|
|
|
585 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
|
|
|
586 if (REG_NOTE_KIND (note) == REG_BR_PROB)
|
|
|
587 XEXP (note, 0) = GEN_INT (REG_BR_PROB_BASE - INTVAL (XEXP (note, 0)));
|
|
|
588 else if (REG_NOTE_KIND (note) == REG_BR_PRED)
|
|
|
589 XEXP (XEXP (note, 0), 1)
|
|
|
590 = GEN_INT (REG_BR_PROB_BASE - INTVAL (XEXP (XEXP (note, 0), 1)));
|
|
|
591 }
|
|
|
592
|
|
|
593 /* Dump information about the branch prediction to the output file. */
|
|
|
594
|
|
|
595 static void
|
|
|
596 dump_prediction (FILE *file, enum br_predictor predictor, int probability,
|
|
|
597 basic_block bb, int used)
|
|
|
598 {
|
|
|
599 edge e;
|
|
|
600 edge_iterator ei;
|
|
|
601
|
|
|
602 if (!file)
|
|
|
603 return;
|
|
|
604
|
|
|
605 FOR_EACH_EDGE (e, ei, bb->succs)
|
|
|
606 if (! (e->flags & EDGE_FALLTHRU))
|
|
|
607 break;
|
|
|
608
|
|
|
609 fprintf (file, " %s heuristics%s: %.1f%%",
|
|
|
610 predictor_info[predictor].name,
|
|
|
611 used ? "" : " (ignored)", probability * 100.0 / REG_BR_PROB_BASE);
|
|
|
612
|
|
|
613 if (bb->count)
|
|
|
614 {
|
|
|
615 fprintf (file, " exec ");
|
|
|
616 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, bb->count);
|
|
|
617 if (e)
|
|
|
618 {
|
|
|
619 fprintf (file, " hit ");
|
|
|
620 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, e->count);
|
|
|
621 fprintf (file, " (%.1f%%)", e->count * 100.0 / bb->count);
|
|
|
622 }
|
|
|
623 }
|
|
|
624
|
|
|
625 fprintf (file, "\n");
|
|
|
626 }
|
|
|
627
|
|
|
628 /* We can not predict the probabilities of outgoing edges of bb. Set them
|
|
|
629 evenly and hope for the best. */
|
|
|
630 static void
|
|
|
631 set_even_probabilities (basic_block bb)
|
|
|
632 {
|
|
|
633 int nedges = 0;
|
|
|
634 edge e;
|
|
|
635 edge_iterator ei;
|
|
|
636
|
|
|
637 FOR_EACH_EDGE (e, ei, bb->succs)
|
|
|
638 if (!(e->flags & (EDGE_EH | EDGE_FAKE)))
|
|
|
639 nedges ++;
|
|
|
640 FOR_EACH_EDGE (e, ei, bb->succs)
|
|
|
641 if (!(e->flags & (EDGE_EH | EDGE_FAKE)))
|
|
|
642 e->probability = (REG_BR_PROB_BASE + nedges / 2) / nedges;
|
|
|
643 else
|
|
|
644 e->probability = 0;
|
|
|
645 }
|
|
|
646
|
|
|
647 /* Combine all REG_BR_PRED notes into single probability and attach REG_BR_PROB
|
|
|
648 note if not already present. Remove now useless REG_BR_PRED notes. */
|
|
|
649
|
|
|
650 static void
|
|
|
651 combine_predictions_for_insn (rtx insn, basic_block bb)
|
|
|
652 {
|
|
|
653 rtx prob_note;
|
|
|
654 rtx *pnote;
|
|
|
655 rtx note;
|
|
|
656 int best_probability = PROB_EVEN;
|
|
|
657 int best_predictor = END_PREDICTORS;
|
|
|
658 int combined_probability = REG_BR_PROB_BASE / 2;
|
|
|
659 int d;
|
|
|
660 bool first_match = false;
|
|
|
661 bool found = false;
|
|
|
662
|
|
|
663 if (!can_predict_insn_p (insn))
|
|
|
664 {
|
|
|
665 set_even_probabilities (bb);
|
|
|
666 return;
|
|
|
667 }
|
|
|
668
|
|
|
669 prob_note = find_reg_note (insn, REG_BR_PROB, 0);
|
|
|
670 pnote = ®_NOTES (insn);
|
|
|
671 if (dump_file)
|
|
|
672 fprintf (dump_file, "Predictions for insn %i bb %i\n", INSN_UID (insn),
|
|
|
673 bb->index);
|
|
|
674
|
|
|
675 /* We implement "first match" heuristics and use probability guessed
|
|
|
676 by predictor with smallest index. */
|
|
|
677 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
|
|
|
678 if (REG_NOTE_KIND (note) == REG_BR_PRED)
|
|
|
679 {
|
|
|
680 int predictor = INTVAL (XEXP (XEXP (note, 0), 0));
|
|
|
681 int probability = INTVAL (XEXP (XEXP (note, 0), 1));
|
|
|
682
|
|
|
683 found = true;
|
|
|
684 if (best_predictor > predictor)
|
|
|
685 best_probability = probability, best_predictor = predictor;
|
|
|
686
|
|
|
687 d = (combined_probability * probability
|
|
|
688 + (REG_BR_PROB_BASE - combined_probability)
|
|
|
689 * (REG_BR_PROB_BASE - probability));
|
|
|
690
|
|
|
691 /* Use FP math to avoid overflows of 32bit integers. */
|
|
|
692 if (d == 0)
|
|
|
693 /* If one probability is 0% and one 100%, avoid division by zero. */
|
|
|
694 combined_probability = REG_BR_PROB_BASE / 2;
|
|
|
695 else
|
|
|
696 combined_probability = (((double) combined_probability) * probability
|
|
|
697 * REG_BR_PROB_BASE / d + 0.5);
|
|
|
698 }
|
|
|
699
|
|
|
700 /* Decide which heuristic to use. In case we didn't match anything,
|
|
|
701 use no_prediction heuristic, in case we did match, use either
|
|
|
702 first match or Dempster-Shaffer theory depending on the flags. */
|
|
|
703
|
|
|
704 if (predictor_info [best_predictor].flags & PRED_FLAG_FIRST_MATCH)
|
|
|
705 first_match = true;
|
|
|
706
|
|
|
707 if (!found)
|
|
|
708 dump_prediction (dump_file, PRED_NO_PREDICTION,
|
|
|
709 combined_probability, bb, true);
|
|
|
710 else
|
|
|
711 {
|
|
|
712 dump_prediction (dump_file, PRED_DS_THEORY, combined_probability,
|
|
|
713 bb, !first_match);
|
|
|
714 dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability,
|
|
|
715 bb, first_match);
|
|
|
716 }
|
|
|
717
|
|
|
718 if (first_match)
|
|
|
719 combined_probability = best_probability;
|
|
|
720 dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb, true);
|
|
|
721
|
|
|
722 while (*pnote)
|
|
|
723 {
|
|
|
724 if (REG_NOTE_KIND (*pnote) == REG_BR_PRED)
|
|
|
725 {
|
|
|
726 int predictor = INTVAL (XEXP (XEXP (*pnote, 0), 0));
|
|
|
727 int probability = INTVAL (XEXP (XEXP (*pnote, 0), 1));
|
|
|
728
|
|
|
729 dump_prediction (dump_file, predictor, probability, bb,
|
|
|
730 !first_match || best_predictor == predictor);
|
|
|
731 *pnote = XEXP (*pnote, 1);
|
|
|
732 }
|
|
|
733 else
|
|
|
734 pnote = &XEXP (*pnote, 1);
|
|
|
735 }
|
|
|
736
|
|
|
737 if (!prob_note)
|
|
|
738 {
|
|
|
739 add_reg_note (insn, REG_BR_PROB, GEN_INT (combined_probability));
|
|
|
740
|
|
|
741 /* Save the prediction into CFG in case we are seeing non-degenerated
|
|
|
742 conditional jump. */
|
|
|
743 if (!single_succ_p (bb))
|
|
|
744 {
|
|
|
745 BRANCH_EDGE (bb)->probability = combined_probability;
|
|
|
746 FALLTHRU_EDGE (bb)->probability
|
|
|
747 = REG_BR_PROB_BASE - combined_probability;
|
|
|
748 }
|
|
|
749 }
|
|
|
750 else if (!single_succ_p (bb))
|
|
|
751 {
|
|
|
752 int prob = INTVAL (XEXP (prob_note, 0));
|
|
|
753
|
|
|
754 BRANCH_EDGE (bb)->probability = prob;
|
|
|
755 FALLTHRU_EDGE (bb)->probability = REG_BR_PROB_BASE - prob;
|
|
|
756 }
|
|
|
757 else
|
|
|
758 single_succ_edge (bb)->probability = REG_BR_PROB_BASE;
|
|
|
759 }
|
|
|
760
|
|
|
761 /* Combine predictions into single probability and store them into CFG.
|
|
|
762 Remove now useless prediction entries. */
|
|
|
763
|
|
|
764 static void
|
|
|
765 combine_predictions_for_bb (basic_block bb)
|
|
|
766 {
|
|
|
767 int best_probability = PROB_EVEN;
|
|
|
768 int best_predictor = END_PREDICTORS;
|
|
|
769 int combined_probability = REG_BR_PROB_BASE / 2;
|
|
|
770 int d;
|
|
|
771 bool first_match = false;
|
|
|
772 bool found = false;
|
|
|
773 struct edge_prediction *pred;
|
|
|
774 int nedges = 0;
|
|
|
775 edge e, first = NULL, second = NULL;
|
|
|
776 edge_iterator ei;
|
|
|
777 void **preds;
|
|
|
778
|
|
|
779 FOR_EACH_EDGE (e, ei, bb->succs)
|
|
|
780 if (!(e->flags & (EDGE_EH | EDGE_FAKE)))
|
|
|
781 {
|
|
|
782 nedges ++;
|
|
|
783 if (first && !second)
|
|
|
784 second = e;
|
|
|
785 if (!first)
|
|
|
786 first = e;
|
|
|
787 }
|
|
|
788
|
|
|
789 /* When there is no successor or only one choice, prediction is easy.
|
|
|
790
|
|
|
791 We are lazy for now and predict only basic blocks with two outgoing
|
|
|
792 edges. It is possible to predict generic case too, but we have to
|
|
|
793 ignore first match heuristics and do more involved combining. Implement
|
|
|
794 this later. */
|
|
|
795 if (nedges != 2)
|
|
|
796 {
|
|
|
797 if (!bb->count)
|
|
|
798 set_even_probabilities (bb);
|
|
|
799 clear_bb_predictions (bb);
|
|
|
800 if (dump_file)
|
|
|
801 fprintf (dump_file, "%i edges in bb %i predicted to even probabilities\n",
|
|
|
802 nedges, bb->index);
|
|
|
803 return;
|
|
|
804 }
|
|
|
805
|
|
|
806 if (dump_file)
|
|
|
807 fprintf (dump_file, "Predictions for bb %i\n", bb->index);
|
|
|
808
|
|
|
809 preds = pointer_map_contains (bb_predictions, bb);
|
|
|
810 if (preds)
|
|
|
811 {
|
|
|
812 /* We implement "first match" heuristics and use probability guessed
|
|
|
813 by predictor with smallest index. */
|
|
|
814 for (pred = (struct edge_prediction *) *preds; pred; pred = pred->ep_next)
|
|
|
815 {
|
|
|
816 int predictor = pred->ep_predictor;
|
|
|
817 int probability = pred->ep_probability;
|
|
|
818
|
|
|
819 if (pred->ep_edge != first)
|
|
|
820 probability = REG_BR_PROB_BASE - probability;
|
|
|
821
|
|
|
822 found = true;
|
|
|
823 /* First match heuristics would be widly confused if we predicted
|
|
|
824 both directions. */
|
|
|
825 if (best_predictor > predictor)
|
|
|
826 {
|
|
|
827 struct edge_prediction *pred2;
|
|
|
828 int prob = probability;
|
|
|
829
|
|
|
830 for (pred2 = (struct edge_prediction *) *preds; pred2; pred2 = pred2->ep_next)
|
|
|
831 if (pred2 != pred && pred2->ep_predictor == pred->ep_predictor)
|
|
|
832 {
|
|
|
833 int probability2 = pred->ep_probability;
|
|
|
834
|
|
|
835 if (pred2->ep_edge != first)
|
|
|
836 probability2 = REG_BR_PROB_BASE - probability2;
|
|
|
837
|
|
|
838 if ((probability < REG_BR_PROB_BASE / 2) !=
|
|
|
839 (probability2 < REG_BR_PROB_BASE / 2))
|
|
|
840 break;
|
|
|
841
|
|
|
842 /* If the same predictor later gave better result, go for it! */
|
|
|
843 if ((probability >= REG_BR_PROB_BASE / 2 && (probability2 > probability))
|
|
|
844 || (probability <= REG_BR_PROB_BASE / 2 && (probability2 < probability)))
|
|
|
845 prob = probability2;
|
|
|
846 }
|
|
|
847 if (!pred2)
|
|
|
848 best_probability = prob, best_predictor = predictor;
|
|
|
849 }
|
|
|
850
|
|
|
851 d = (combined_probability * probability
|
|
|
852 + (REG_BR_PROB_BASE - combined_probability)
|
|
|
853 * (REG_BR_PROB_BASE - probability));
|
|
|
854
|
|
|
855 /* Use FP math to avoid overflows of 32bit integers. */
|
|
|
856 if (d == 0)
|
|
|
857 /* If one probability is 0% and one 100%, avoid division by zero. */
|
|
|
858 combined_probability = REG_BR_PROB_BASE / 2;
|
|
|
859 else
|
|
|
860 combined_probability = (((double) combined_probability)
|
|
|
861 * probability
|
|
|
862 * REG_BR_PROB_BASE / d + 0.5);
|
|
|
863 }
|
|
|
864 }
|
|
|
865
|
|
|
866 /* Decide which heuristic to use. In case we didn't match anything,
|
|
|
867 use no_prediction heuristic, in case we did match, use either
|
|
|
868 first match or Dempster-Shaffer theory depending on the flags. */
|
|
|
869
|
|
|
870 if (predictor_info [best_predictor].flags & PRED_FLAG_FIRST_MATCH)
|
|
|
871 first_match = true;
|
|
|
872
|
|
|
873 if (!found)
|
|
|
874 dump_prediction (dump_file, PRED_NO_PREDICTION, combined_probability, bb, true);
|
|
|
875 else
|
|
|
876 {
|
|
|
877 dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, bb,
|
|
|
878 !first_match);
|
|
|
879 dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, bb,
|
|
|
880 first_match);
|
|
|
881 }
|
|
|
882
|
|
|
883 if (first_match)
|
|
|
884 combined_probability = best_probability;
|
|
|
885 dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb, true);
|
|
|
886
|
|
|
887 if (preds)
|
|
|
888 {
|
|
|
889 for (pred = (struct edge_prediction *) *preds; pred; pred = pred->ep_next)
|
|
|
890 {
|
|
|
891 int predictor = pred->ep_predictor;
|
|
|
892 int probability = pred->ep_probability;
|
|
|
893
|
|
|
894 if (pred->ep_edge != EDGE_SUCC (bb, 0))
|
|
|
895 probability = REG_BR_PROB_BASE - probability;
|
|
|
896 dump_prediction (dump_file, predictor, probability, bb,
|
|
|
897 !first_match || best_predictor == predictor);
|
|
|
898 }
|
|
|
899 }
|
|
|
900 clear_bb_predictions (bb);
|
|
|
901
|
|
|
902 if (!bb->count)
|
|
|
903 {
|
|
|
904 first->probability = combined_probability;
|
|
|
905 second->probability = REG_BR_PROB_BASE - combined_probability;
|
|
|
906 }
|
|
|
907 }
|
|
|
908
|
|
|
909 /* Predict edge probabilities by exploiting loop structure. */
|
|
|
910
|
|
|
911 static void
|
|
|
912 predict_loops (void)
|
|
|
913 {
|
|
|
914 loop_iterator li;
|
|
|
915 struct loop *loop;
|
|
|
916
|
|
|
917 scev_initialize ();
|
|
|
918
|
|
|
919 /* Try to predict out blocks in a loop that are not part of a
|
|
|
920 natural loop. */
|
|
|
921 FOR_EACH_LOOP (li, loop, 0)
|
|
|
922 {
|
|
|
923 basic_block bb, *bbs;
|
|
|
924 unsigned j, n_exits;
|
|
|
925 VEC (edge, heap) *exits;
|
|
|
926 struct tree_niter_desc niter_desc;
|
|
|
927 edge ex;
|
|
|
928
|
|
|
929 exits = get_loop_exit_edges (loop);
|
|
|
930 n_exits = VEC_length (edge, exits);
|
|
|
931
|
|
|
932 for (j = 0; VEC_iterate (edge, exits, j, ex); j++)
|
|
|
933 {
|
|
|
934 tree niter = NULL;
|
|
|
935 HOST_WIDE_INT nitercst;
|
|
|
936 int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS);
|
|
|
937 int probability;
|
|
|
938 enum br_predictor predictor;
|
|
|
939
|
|
|
940 if (number_of_iterations_exit (loop, ex, &niter_desc, false))
|
|
|
941 niter = niter_desc.niter;
|
|
|
942 if (!niter || TREE_CODE (niter_desc.niter) != INTEGER_CST)
|
|
|
943 niter = loop_niter_by_eval (loop, ex);
|
|
|
944
|
|
|
945 if (TREE_CODE (niter) == INTEGER_CST)
|
|
|
946 {
|
|
|
947 if (host_integerp (niter, 1)
|
|
|
948 && compare_tree_int (niter, max-1) == -1)
|
|
|
949 nitercst = tree_low_cst (niter, 1) + 1;
|
|
|
950 else
|
|
|
951 nitercst = max;
|
|
|
952 predictor = PRED_LOOP_ITERATIONS;
|
|
|
953 }
|
|
|
954 /* If we have just one exit and we can derive some information about
|
|
|
955 the number of iterations of the loop from the statements inside
|
|
|
956 the loop, use it to predict this exit. */
|
|
|
957 else if (n_exits == 1)
|
|
|
958 {
|
|
|
959 nitercst = estimated_loop_iterations_int (loop, false);
|
|
|
960 if (nitercst < 0)
|
|
|
961 continue;
|
|
|
962 if (nitercst > max)
|
|
|
963 nitercst = max;
|
|
|
964
|
|
|
965 predictor = PRED_LOOP_ITERATIONS_GUESSED;
|
|
|
966 }
|
|
|
967 else
|
|
|
968 continue;
|
|
|
969
|
|
|
970 probability = ((REG_BR_PROB_BASE + nitercst / 2) / nitercst);
|
|
|
971 predict_edge (ex, predictor, probability);
|
|
|
972 }
|
|
|
973 VEC_free (edge, heap, exits);
|
|
|
974
|
|
|
975 bbs = get_loop_body (loop);
|
|
|
976
|
|
|
977 for (j = 0; j < loop->num_nodes; j++)
|
|
|
978 {
|
|
|
979 int header_found = 0;
|
|
|
980 edge e;
|
|
|
981 edge_iterator ei;
|
|
|
982
|
|
|
983 bb = bbs[j];
|
|
|
984
|
|
|
985 /* Bypass loop heuristics on continue statement. These
|
|
|
986 statements construct loops via "non-loop" constructs
|
|
|
987 in the source language and are better to be handled
|
|
|
988 separately. */
|
|
|
989 if (predicted_by_p (bb, PRED_CONTINUE))
|
|
|
990 continue;
|
|
|
991
|
|
|
992 /* Loop branch heuristics - predict an edge back to a
|
|
|
993 loop's head as taken. */
|
|
|
994 if (bb == loop->latch)
|
|
|
995 {
|
|
|
996 e = find_edge (loop->latch, loop->header);
|
|
|
997 if (e)
|
|
|
998 {
|
|
|
999 header_found = 1;
|
|
|
1000 predict_edge_def (e, PRED_LOOP_BRANCH, TAKEN);
|
|
|
1001 }
|
|
|
1002 }
|
|
|
1003
|
|
|
1004 /* Loop exit heuristics - predict an edge exiting the loop if the
|
|
|
1005 conditional has no loop header successors as not taken. */
|
|
|
1006 if (!header_found
|
|
|
1007 /* If we already used more reliable loop exit predictors, do not
|
|
|
1008 bother with PRED_LOOP_EXIT. */
|
|
|
1009 && !predicted_by_p (bb, PRED_LOOP_ITERATIONS_GUESSED)
|
|
|
1010 && !predicted_by_p (bb, PRED_LOOP_ITERATIONS))
|
|
|
1011 {
|
|
|
1012 /* For loop with many exits we don't want to predict all exits
|
|
|
1013 with the pretty large probability, because if all exits are
|
|
|
1014 considered in row, the loop would be predicted to iterate
|
|
|
1015 almost never. The code to divide probability by number of
|
|
|
1016 exits is very rough. It should compute the number of exits
|
|
|
1017 taken in each patch through function (not the overall number
|
|
|
1018 of exits that might be a lot higher for loops with wide switch
|
|
|
1019 statements in them) and compute n-th square root.
|
|
|
1020
|
|
|
1021 We limit the minimal probability by 2% to avoid
|
|
|
1022 EDGE_PROBABILITY_RELIABLE from trusting the branch prediction
|
|
|
1023 as this was causing regression in perl benchmark containing such
|
|
|
1024 a wide loop. */
|
|
|
1025
|
|
|
1026 int probability = ((REG_BR_PROB_BASE
|
|
|
1027 - predictor_info [(int) PRED_LOOP_EXIT].hitrate)
|
|
|
1028 / n_exits);
|
|
|
1029 if (probability < HITRATE (2))
|
|
|
1030 probability = HITRATE (2);
|
|
|
1031 FOR_EACH_EDGE (e, ei, bb->succs)
|
|
|
1032 if (e->dest->index < NUM_FIXED_BLOCKS
|
|
|
1033 || !flow_bb_inside_loop_p (loop, e->dest))
|
|
|
1034 predict_edge (e, PRED_LOOP_EXIT, probability);
|
|
|
1035 }
|
|
|
1036 }
|
|
|
1037
|
|
|
1038 /* Free basic blocks from get_loop_body. */
|
|
|
1039 free (bbs);
|
|
|
1040 }
|
|
|
1041
|
|
|
1042 scev_finalize ();
|
|
|
1043 }
|
|
|
1044
|
|
|
1045 /* Attempt to predict probabilities of BB outgoing edges using local
|
|
|
1046 properties. */
|
|
|
1047 static void
|
|
|
1048 bb_estimate_probability_locally (basic_block bb)
|
|
|
1049 {
|
|
|
1050 rtx last_insn = BB_END (bb);
|
|
|
1051 rtx cond;
|
|
|
1052
|
|
|
1053 if (! can_predict_insn_p (last_insn))
|
|
|
1054 return;
|
|
|
1055 cond = get_condition (last_insn, NULL, false, false);
|
|
|
1056 if (! cond)
|
|
|
1057 return;
|
|
|
1058
|
|
|
1059 /* Try "pointer heuristic."
|
|
|
1060 A comparison ptr == 0 is predicted as false.
|
|
|
1061 Similarly, a comparison ptr1 == ptr2 is predicted as false. */
|
|
|
1062 if (COMPARISON_P (cond)
|
|
|
1063 && ((REG_P (XEXP (cond, 0)) && REG_POINTER (XEXP (cond, 0)))
|
|
|
1064 || (REG_P (XEXP (cond, 1)) && REG_POINTER (XEXP (cond, 1)))))
|
|
|
1065 {
|
|
|
1066 if (GET_CODE (cond) == EQ)
|
|
|
1067 predict_insn_def (last_insn, PRED_POINTER, NOT_TAKEN);
|
|
|
1068 else if (GET_CODE (cond) == NE)
|
|
|
1069 predict_insn_def (last_insn, PRED_POINTER, TAKEN);
|
|
|
1070 }
|
|
|
1071 else
|
|
|
1072
|
|
|
1073 /* Try "opcode heuristic."
|
|
|
1074 EQ tests are usually false and NE tests are usually true. Also,
|
|
|
1075 most quantities are positive, so we can make the appropriate guesses
|
|
|
1076 about signed comparisons against zero. */
|
|
|
1077 switch (GET_CODE (cond))
|
|
|
1078 {
|
|
|
1079 case CONST_INT:
|
|
|
1080 /* Unconditional branch. */
|
|
|
1081 predict_insn_def (last_insn, PRED_UNCONDITIONAL,
|
|
|
1082 cond == const0_rtx ? NOT_TAKEN : TAKEN);
|
|
|
1083 break;
|
|
|
1084
|
|
|
1085 case EQ:
|
|
|
1086 case UNEQ:
|
|
|
1087 /* Floating point comparisons appears to behave in a very
|
|
|
1088 unpredictable way because of special role of = tests in
|
|
|
1089 FP code. */
|
|
|
1090 if (FLOAT_MODE_P (GET_MODE (XEXP (cond, 0))))
|
|
|
1091 ;
|
|
|
1092 /* Comparisons with 0 are often used for booleans and there is
|
|
|
1093 nothing useful to predict about them. */
|
|
|
1094 else if (XEXP (cond, 1) == const0_rtx
|
|
|
1095 || XEXP (cond, 0) == const0_rtx)
|
|
|
1096 ;
|
|
|
1097 else
|
|
|
1098 predict_insn_def (last_insn, PRED_OPCODE_NONEQUAL, NOT_TAKEN);
|
|
|
1099 break;
|
|
|
1100
|
|
|
1101 case NE:
|
|
|
1102 case LTGT:
|
|
|
1103 /* Floating point comparisons appears to behave in a very
|
|
|
1104 unpredictable way because of special role of = tests in
|
|
|
1105 FP code. */
|
|
|
1106 if (FLOAT_MODE_P (GET_MODE (XEXP (cond, 0))))
|
|
|
1107 ;
|
|
|
1108 /* Comparisons with 0 are often used for booleans and there is
|
|
|
1109 nothing useful to predict about them. */
|
|
|
1110 else if (XEXP (cond, 1) == const0_rtx
|
|
|
1111 || XEXP (cond, 0) == const0_rtx)
|
|
|
1112 ;
|
|
|
1113 else
|
|
|
1114 predict_insn_def (last_insn, PRED_OPCODE_NONEQUAL, TAKEN);
|
|
|
1115 break;
|
|
|
1116
|
|
|
1117 case ORDERED:
|
|
|
1118 predict_insn_def (last_insn, PRED_FPOPCODE, TAKEN);
|
|
|
1119 break;
|
|
|
1120
|
|
|
1121 case UNORDERED:
|
|
|
1122 predict_insn_def (last_insn, PRED_FPOPCODE, NOT_TAKEN);
|
|
|
1123 break;
|
|
|
1124
|
|
|
1125 case LE:
|
|
|
1126 case LT:
|
|
|
1127 if (XEXP (cond, 1) == const0_rtx || XEXP (cond, 1) == const1_rtx
|
|
|
1128 || XEXP (cond, 1) == constm1_rtx)
|
|
|
1129 predict_insn_def (last_insn, PRED_OPCODE_POSITIVE, NOT_TAKEN);
|
|
|
1130 break;
|
|
|
1131
|
|
|
1132 case GE:
|
|
|
1133 case GT:
|
|
|
1134 if (XEXP (cond, 1) == const0_rtx || XEXP (cond, 1) == const1_rtx
|
|
|
1135 || XEXP (cond, 1) == constm1_rtx)
|
|
|
1136 predict_insn_def (last_insn, PRED_OPCODE_POSITIVE, TAKEN);
|
|
|
1137 break;
|
|
|
1138
|
|
|
1139 default:
|
|
|
1140 break;
|
|
|
1141 }
|
|
|
1142 }
|
|
|
1143
|
|
|
1144 /* Set edge->probability for each successor edge of BB. */
|
|
|
1145 void
|
|
|
1146 guess_outgoing_edge_probabilities (basic_block bb)
|
|
|
1147 {
|
|
|
1148 bb_estimate_probability_locally (bb);
|
|
|
1149 combine_predictions_for_insn (BB_END (bb), bb);
|
|
|
1150 }
|
|
|
1151
|
|
|
1152 static tree expr_expected_value (tree, bitmap);
|
|
|
1153
|
|
|
1154 /* Helper function for expr_expected_value. */
|
|
|
1155
|
|
|
1156 static tree
|
|
|
1157 expr_expected_value_1 (tree type, tree op0, enum tree_code code, tree op1, bitmap visited)
|
|
|
1158 {
|
|
|
1159 gimple def;
|
|
|
1160
|
|
|
1161 if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS)
|
|
|
1162 {
|
|
|
1163 if (TREE_CONSTANT (op0))
|
|
|
1164 return op0;
|
|
|
1165
|
|
|
1166 if (code != SSA_NAME)
|
|
|
1167 return NULL_TREE;
|
|
|
1168
|
|
|
1169 def = SSA_NAME_DEF_STMT (op0);
|
|
|
1170
|
|
|
1171 /* If we were already here, break the infinite cycle. */
|
|
|
1172 if (bitmap_bit_p (visited, SSA_NAME_VERSION (op0)))
|
|
|
1173 return NULL;
|
|
|
1174 bitmap_set_bit (visited, SSA_NAME_VERSION (op0));
|
|
|
1175
|
|
|
1176 if (gimple_code (def) == GIMPLE_PHI)
|
|
|
1177 {
|
|
|
1178 /* All the arguments of the PHI node must have the same constant
|
|
|
1179 length. */
|
|
|
1180 int i, n = gimple_phi_num_args (def);
|
|
|
1181 tree val = NULL, new_val;
|
|
|
1182
|
|
|
1183 for (i = 0; i < n; i++)
|
|
|
1184 {
|
|
|
1185 tree arg = PHI_ARG_DEF (def, i);
|
|
|
1186
|
|
|
1187 /* If this PHI has itself as an argument, we cannot
|
|
|
1188 determine the string length of this argument. However,
|
|
|
1189 if we can find an expected constant value for the other
|
|
|
1190 PHI args then we can still be sure that this is
|
|
|
1191 likely a constant. So be optimistic and just
|
|
|
1192 continue with the next argument. */
|
|
|
1193 if (arg == PHI_RESULT (def))
|
|
|
1194 continue;
|
|
|
1195
|
|
|
1196 new_val = expr_expected_value (arg, visited);
|
|
|
1197 if (!new_val)
|
|
|
1198 return NULL;
|
|
|
1199 if (!val)
|
|
|
1200 val = new_val;
|
|
|
1201 else if (!operand_equal_p (val, new_val, false))
|
|
|
1202 return NULL;
|
|
|
1203 }
|
|
|
1204 return val;
|
|
|
1205 }
|
|
|
1206 if (is_gimple_assign (def))
|
|
|
1207 {
|
|
|
1208 if (gimple_assign_lhs (def) != op0)
|
|
|
1209 return NULL;
|
|
|
1210
|
|
|
1211 return expr_expected_value_1 (TREE_TYPE (gimple_assign_lhs (def)),
|
|
|
1212 gimple_assign_rhs1 (def),
|
|
|
1213 gimple_assign_rhs_code (def),
|
|
|
1214 gimple_assign_rhs2 (def),
|
|
|
1215 visited);
|
|
|
1216 }
|
|
|
1217
|
|
|
1218 if (is_gimple_call (def))
|
|
|
1219 {
|
|
|
1220 tree decl = gimple_call_fndecl (def);
|
|
|
1221 if (!decl)
|
|
|
1222 return NULL;
|
|
|
1223 if (DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL
|
|
|
1224 && DECL_FUNCTION_CODE (decl) == BUILT_IN_EXPECT)
|
|
|
1225 {
|
|
|
1226 tree val;
|
|
|
1227
|
|
|
1228 if (gimple_call_num_args (def) != 2)
|
|
|
1229 return NULL;
|
|
|
1230 val = gimple_call_arg (def, 0);
|
|
|
1231 if (TREE_CONSTANT (val))
|
|
|
1232 return val;
|
|
|
1233 return gimple_call_arg (def, 1);
|
|
|
1234 }
|
|
|
1235 }
|
|
|
1236
|
|
|
1237 return NULL;
|
|
|
1238 }
|
|
|
1239
|
|
|
1240 if (get_gimple_rhs_class (code) == GIMPLE_BINARY_RHS)
|
|
|
1241 {
|
|
|
1242 tree res;
|
|
|
1243 op0 = expr_expected_value (op0, visited);
|
|
|
1244 if (!op0)
|
|
|
1245 return NULL;
|
|
|
1246 op1 = expr_expected_value (op1, visited);
|
|
|
1247 if (!op1)
|
|
|
1248 return NULL;
|
|
|
1249 res = fold_build2 (code, type, op0, op1);
|
|
|
1250 if (TREE_CONSTANT (res))
|
|
|
1251 return res;
|
|
|
1252 return NULL;
|
|
|
1253 }
|
|
|
1254 if (get_gimple_rhs_class (code) == GIMPLE_UNARY_RHS)
|
|
|
1255 {
|
|
|
1256 tree res;
|
|
|
1257 op0 = expr_expected_value (op0, visited);
|
|
|
1258 if (!op0)
|
|
|
1259 return NULL;
|
|
|
1260 res = fold_build1 (code, type, op0);
|
|
|
1261 if (TREE_CONSTANT (res))
|
|
|
1262 return res;
|
|
|
1263 return NULL;
|
|
|
1264 }
|
|
|
1265 return NULL;
|
|
|
1266 }
|
|
|
1267
|
|
|
1268 /* Return constant EXPR will likely have at execution time, NULL if unknown.
|
|
|
1269 The function is used by builtin_expect branch predictor so the evidence
|
|
|
1270 must come from this construct and additional possible constant folding.
|
|
|
1271
|
|
|
1272 We may want to implement more involved value guess (such as value range
|
|
|
1273 propagation based prediction), but such tricks shall go to new
|
|
|
1274 implementation. */
|
|
|
1275
|
|
|
1276 static tree
|
|
|
1277 expr_expected_value (tree expr, bitmap visited)
|
|
|
1278 {
|
|
|
1279 enum tree_code code;
|
|
|
1280 tree op0, op1;
|
|
|
1281
|
|
|
1282 if (TREE_CONSTANT (expr))
|
|
|
1283 return expr;
|
|
|
1284
|
|
|
1285 extract_ops_from_tree (expr, &code, &op0, &op1);
|
|
|
1286 return expr_expected_value_1 (TREE_TYPE (expr),
|
|
|
1287 op0, code, op1, visited);
|
|
|
1288 }
|
|
|
1289
|
|
|
1290
|
|
|
1291 /* Get rid of all builtin_expect calls and GIMPLE_PREDICT statements
|
|
|
1292 we no longer need. */
|
|
|
1293 static unsigned int
|
|
|
1294 strip_predict_hints (void)
|
|
|
1295 {
|
|
|
1296 basic_block bb;
|
|
|
1297 gimple ass_stmt;
|
|
|
1298 tree var;
|
|
|
1299
|
|
|
1300 FOR_EACH_BB (bb)
|
|
|
1301 {
|
|
|
1302 gimple_stmt_iterator bi;
|
|
|
1303 for (bi = gsi_start_bb (bb); !gsi_end_p (bi);)
|
|
|
1304 {
|
|
|
1305 gimple stmt = gsi_stmt (bi);
|
|
|
1306
|
|
|
1307 if (gimple_code (stmt) == GIMPLE_PREDICT)
|
|
|
1308 {
|
|
|
1309 gsi_remove (&bi, true);
|
|
|
1310 continue;
|
|
|
1311 }
|
|
|
1312 else if (gimple_code (stmt) == GIMPLE_CALL)
|
|
|
1313 {
|
|
|
1314 tree fndecl = gimple_call_fndecl (stmt);
|
|
|
1315
|
|
|
1316 if (fndecl
|
|
|
1317 && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL
|
|
|
1318 && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_EXPECT
|
|
|
1319 && gimple_call_num_args (stmt) == 2)
|
|
|
1320 {
|
|
|
1321 var = gimple_call_lhs (stmt);
|
|
|
1322 ass_stmt = gimple_build_assign (var, gimple_call_arg (stmt, 0));
|
|
|
1323
|
|
|
1324 gsi_replace (&bi, ass_stmt, true);
|
|
|
1325 }
|
|
|
1326 }
|
|
|
1327 gsi_next (&bi);
|
|
|
1328 }
|
|
|
1329 }
|
|
|
1330 return 0;
|
|
|
1331 }
|
|
|
1332
|
|
|
1333 /* Predict using opcode of the last statement in basic block. */
|
|
|
1334 static void
|
|
|
1335 tree_predict_by_opcode (basic_block bb)
|
|
|
1336 {
|
|
|
1337 gimple stmt = last_stmt (bb);
|
|
|
1338 edge then_edge;
|
|
|
1339 tree op0, op1;
|
|
|
1340 tree type;
|
|
|
1341 tree val;
|
|
|
1342 enum tree_code cmp;
|
|
|
1343 bitmap visited;
|
|
|
1344 edge_iterator ei;
|
|
|
1345
|
|
|
1346 if (!stmt || gimple_code (stmt) != GIMPLE_COND)
|
|
|
1347 return;
|
|
|
1348 FOR_EACH_EDGE (then_edge, ei, bb->succs)
|
|
|
1349 if (then_edge->flags & EDGE_TRUE_VALUE)
|
|
|
1350 break;
|
|
|
1351 op0 = gimple_cond_lhs (stmt);
|
|
|
1352 op1 = gimple_cond_rhs (stmt);
|
|
|
1353 cmp = gimple_cond_code (stmt);
|
|
|
1354 type = TREE_TYPE (op0);
|
|
|
1355 visited = BITMAP_ALLOC (NULL);
|
|
|
1356 val = expr_expected_value_1 (boolean_type_node, op0, cmp, op1, visited);
|
|
|
1357 BITMAP_FREE (visited);
|
|
|
1358 if (val)
|
|
|
1359 {
|
|
|
1360 if (integer_zerop (val))
|
|
|
1361 predict_edge_def (then_edge, PRED_BUILTIN_EXPECT, NOT_TAKEN);
|
|
|
1362 else
|
|
|
1363 predict_edge_def (then_edge, PRED_BUILTIN_EXPECT, TAKEN);
|
|
|
1364 return;
|
|
|
1365 }
|
|
|
1366 /* Try "pointer heuristic."
|
|
|
1367 A comparison ptr == 0 is predicted as false.
|
|
|
1368 Similarly, a comparison ptr1 == ptr2 is predicted as false. */
|
|
|
1369 if (POINTER_TYPE_P (type))
|
|
|
1370 {
|
|
|
1371 if (cmp == EQ_EXPR)
|
|
|
1372 predict_edge_def (then_edge, PRED_TREE_POINTER, NOT_TAKEN);
|
|
|
1373 else if (cmp == NE_EXPR)
|
|
|
1374 predict_edge_def (then_edge, PRED_TREE_POINTER, TAKEN);
|
|
|
1375 }
|
|
|
1376 else
|
|
|
1377
|
|
|
1378 /* Try "opcode heuristic."
|
|
|
1379 EQ tests are usually false and NE tests are usually true. Also,
|
|
|
1380 most quantities are positive, so we can make the appropriate guesses
|
|
|
1381 about signed comparisons against zero. */
|
|
|
1382 switch (cmp)
|
|
|
1383 {
|
|
|
1384 case EQ_EXPR:
|
|
|
1385 case UNEQ_EXPR:
|
|
|
1386 /* Floating point comparisons appears to behave in a very
|
|
|
1387 unpredictable way because of special role of = tests in
|
|
|
1388 FP code. */
|
|
|
1389 if (FLOAT_TYPE_P (type))
|
|
|
1390 ;
|
|
|
1391 /* Comparisons with 0 are often used for booleans and there is
|
|
|
1392 nothing useful to predict about them. */
|
|
|
1393 else if (integer_zerop (op0) || integer_zerop (op1))
|
|
|
1394 ;
|
|
|
1395 else
|
|
|
1396 predict_edge_def (then_edge, PRED_TREE_OPCODE_NONEQUAL, NOT_TAKEN);
|
|
|
1397 break;
|
|
|
1398
|
|
|
1399 case NE_EXPR:
|
|
|
1400 case LTGT_EXPR:
|
|
|
1401 /* Floating point comparisons appears to behave in a very
|
|
|
1402 unpredictable way because of special role of = tests in
|
|
|
1403 FP code. */
|
|
|
1404 if (FLOAT_TYPE_P (type))
|
|
|
1405 ;
|
|
|
1406 /* Comparisons with 0 are often used for booleans and there is
|
|
|
1407 nothing useful to predict about them. */
|
|
|
1408 else if (integer_zerop (op0)
|
|
|
1409 || integer_zerop (op1))
|
|
|
1410 ;
|
|
|
1411 else
|
|
|
1412 predict_edge_def (then_edge, PRED_TREE_OPCODE_NONEQUAL, TAKEN);
|
|
|
1413 break;
|
|
|
1414
|
|
|
1415 case ORDERED_EXPR:
|
|
|
1416 predict_edge_def (then_edge, PRED_TREE_FPOPCODE, TAKEN);
|
|
|
1417 break;
|
|
|
1418
|
|
|
1419 case UNORDERED_EXPR:
|
|
|
1420 predict_edge_def (then_edge, PRED_TREE_FPOPCODE, NOT_TAKEN);
|
|
|
1421 break;
|
|
|
1422
|
|
|
1423 case LE_EXPR:
|
|
|
1424 case LT_EXPR:
|
|
|
1425 if (integer_zerop (op1)
|
|
|
1426 || integer_onep (op1)
|
|
|
1427 || integer_all_onesp (op1)
|
|
|
1428 || real_zerop (op1)
|
|
|
1429 || real_onep (op1)
|
|
|
1430 || real_minus_onep (op1))
|
|
|
1431 predict_edge_def (then_edge, PRED_TREE_OPCODE_POSITIVE, NOT_TAKEN);
|
|
|
1432 break;
|
|
|
1433
|
|
|
1434 case GE_EXPR:
|
|
|
1435 case GT_EXPR:
|
|
|
1436 if (integer_zerop (op1)
|
|
|
1437 || integer_onep (op1)
|
|
|
1438 || integer_all_onesp (op1)
|
|
|
1439 || real_zerop (op1)
|
|
|
1440 || real_onep (op1)
|
|
|
1441 || real_minus_onep (op1))
|
|
|
1442 predict_edge_def (then_edge, PRED_TREE_OPCODE_POSITIVE, TAKEN);
|
|
|
1443 break;
|
|
|
1444
|
|
|
1445 default:
|
|
|
1446 break;
|
|
|
1447 }
|
|
|
1448 }
|
|
|
1449
|
|
|
1450 /* Try to guess whether the value of return means error code. */
|
|
|
1451
|
|
|
1452 static enum br_predictor
|
|
|
1453 return_prediction (tree val, enum prediction *prediction)
|
|
|
1454 {
|
|
|
1455 /* VOID. */
|
|
|
1456 if (!val)
|
|
|
1457 return PRED_NO_PREDICTION;
|
|
|
1458 /* Different heuristics for pointers and scalars. */
|
|
|
1459 if (POINTER_TYPE_P (TREE_TYPE (val)))
|
|
|
1460 {
|
|
|
1461 /* NULL is usually not returned. */
|
|
|
1462 if (integer_zerop (val))
|
|
|
1463 {
|
|
|
1464 *prediction = NOT_TAKEN;
|
|
|
1465 return PRED_NULL_RETURN;
|
|
|
1466 }
|
|
|
1467 }
|
|
|
1468 else if (INTEGRAL_TYPE_P (TREE_TYPE (val)))
|
|
|
1469 {
|
|
|
1470 /* Negative return values are often used to indicate
|
|
|
1471 errors. */
|
|
|
1472 if (TREE_CODE (val) == INTEGER_CST
|
|
|
1473 && tree_int_cst_sgn (val) < 0)
|
|
|
1474 {
|
|
|
1475 *prediction = NOT_TAKEN;
|
|
|
1476 return PRED_NEGATIVE_RETURN;
|
|
|
1477 }
|
|
|
1478 /* Constant return values seems to be commonly taken.
|
|
|
1479 Zero/one often represent booleans so exclude them from the
|
|
|
1480 heuristics. */
|
|
|
1481 if (TREE_CONSTANT (val)
|
|
|
1482 && (!integer_zerop (val) && !integer_onep (val)))
|
|
|
1483 {
|
|
|
1484 *prediction = TAKEN;
|
|
|
1485 return PRED_CONST_RETURN;
|
|
|
1486 }
|
|
|
1487 }
|
|
|
1488 return PRED_NO_PREDICTION;
|
|
|
1489 }
|
|
|
1490
|
|
|
1491 /* Find the basic block with return expression and look up for possible
|
|
|
1492 return value trying to apply RETURN_PREDICTION heuristics. */
|
|
|
1493 static void
|
|
|
1494 apply_return_prediction (void)
|
|
|
1495 {
|
|
|
1496 gimple return_stmt = NULL;
|
|
|
1497 tree return_val;
|
|
|
1498 edge e;
|
|
|
1499 gimple phi;
|
|
|
1500 int phi_num_args, i;
|
|
|
1501 enum br_predictor pred;
|
|
|
1502 enum prediction direction;
|
|
|
1503 edge_iterator ei;
|
|
|
1504
|
|
|
1505 FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
|
|
|
1506 {
|
|
|
1507 return_stmt = last_stmt (e->src);
|
|
|
1508 if (return_stmt
|
|
|
1509 && gimple_code (return_stmt) == GIMPLE_RETURN)
|
|
|
1510 break;
|
|
|
1511 }
|
|
|
1512 if (!e)
|
|
|
1513 return;
|
|
|
1514 return_val = gimple_return_retval (return_stmt);
|
|
|
1515 if (!return_val)
|
|
|
1516 return;
|
|
|
1517 if (TREE_CODE (return_val) != SSA_NAME
|
|
|
1518 || !SSA_NAME_DEF_STMT (return_val)
|
|
|
1519 || gimple_code (SSA_NAME_DEF_STMT (return_val)) != GIMPLE_PHI)
|
|
|
1520 return;
|
|
|
1521 phi = SSA_NAME_DEF_STMT (return_val);
|
|
|
1522 phi_num_args = gimple_phi_num_args (phi);
|
|
|
1523 pred = return_prediction (PHI_ARG_DEF (phi, 0), &direction);
|
|
|
1524
|
|
|
1525 /* Avoid the degenerate case where all return values form the function
|
|
|
1526 belongs to same category (ie they are all positive constants)
|
|
|
1527 so we can hardly say something about them. */
|
|
|
1528 for (i = 1; i < phi_num_args; i++)
|
|
|
1529 if (pred != return_prediction (PHI_ARG_DEF (phi, i), &direction))
|
|
|
1530 break;
|
|
|
1531 if (i != phi_num_args)
|
|
|
1532 for (i = 0; i < phi_num_args; i++)
|
|
|
1533 {
|
|
|
1534 pred = return_prediction (PHI_ARG_DEF (phi, i), &direction);
|
|
|
1535 if (pred != PRED_NO_PREDICTION)
|
|
|
1536 predict_paths_leading_to (gimple_phi_arg_edge (phi, i)->src, pred,
|
|
|
1537 direction);
|
|
|
1538 }
|
|
|
1539 }
|
|
|
1540
|
|
|
1541 /* Look for basic block that contains unlikely to happen events
|
|
|
1542 (such as noreturn calls) and mark all paths leading to execution
|
|
|
1543 of this basic blocks as unlikely. */
|
|
|
1544
|
|
|
1545 static void
|
|
|
1546 tree_bb_level_predictions (void)
|
|
|
1547 {
|
|
|
1548 basic_block bb;
|
|
|
1549 bool has_return_edges = false;
|
|
|
1550 edge e;
|
|
|
1551 edge_iterator ei;
|
|
|
1552
|
|
|
1553 FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
|
|
|
1554 if (!(e->flags & (EDGE_ABNORMAL | EDGE_FAKE | EDGE_EH)))
|
|
|
1555 {
|
|
|
1556 has_return_edges = true;
|
|
|
1557 break;
|
|
|
1558 }
|
|
|
1559
|
|
|
1560 apply_return_prediction ();
|
|
|
1561
|
|
|
1562 FOR_EACH_BB (bb)
|
|
|
1563 {
|
|
|
1564 gimple_stmt_iterator gsi;
|
|
|
1565
|
|
|
1566 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
|
|
|
1567 {
|
|
|
1568 gimple stmt = gsi_stmt (gsi);
|
|
|
1569 tree decl;
|
|
|
1570
|
|
|
1571 if (is_gimple_call (stmt))
|
|
|
1572 {
|
|
|
1573 if ((gimple_call_flags (stmt) & ECF_NORETURN)
|
|
|
1574 && has_return_edges)
|
|
|
1575 predict_paths_leading_to (bb, PRED_NORETURN,
|
|
|
1576 NOT_TAKEN);
|
|
|
1577 decl = gimple_call_fndecl (stmt);
|
|
|
1578 if (decl
|
|
|
1579 && lookup_attribute ("cold",
|
|
|
1580 DECL_ATTRIBUTES (decl)))
|
|
|
1581 predict_paths_leading_to (bb, PRED_COLD_FUNCTION,
|
|
|
1582 NOT_TAKEN);
|
|
|
1583 }
|
|
|
1584 else if (gimple_code (stmt) == GIMPLE_PREDICT)
|
|
|
1585 {
|
|
|
1586 predict_paths_leading_to (bb, gimple_predict_predictor (stmt),
|
|
|
1587 gimple_predict_outcome (stmt));
|
|
|
1588 /* Keep GIMPLE_PREDICT around so early inlining will propagate
|
|
|
1589 hints to callers. */
|
|
|
1590 }
|
|
|
1591 }
|
|
|
1592 }
|
|
|
1593 }
|
|
|
1594
|
|
|
1595 #ifdef ENABLE_CHECKING
|
|
|
1596
|
|
|
1597 /* Callback for pointer_map_traverse, asserts that the pointer map is
|
|
|
1598 empty. */
|
|
|
1599
|
|
|
1600 static bool
|
|
|
1601 assert_is_empty (const void *key ATTRIBUTE_UNUSED, void **value,
|
|
|
1602 void *data ATTRIBUTE_UNUSED)
|
|
|
1603 {
|
|
|
1604 gcc_assert (!*value);
|
|
|
1605 return false;
|
|
|
1606 }
|
|
|
1607 #endif
|
|
|
1608
|
|
|
1609 /* Predict branch probabilities and estimate profile of the tree CFG. */
|
|
|
1610 static unsigned int
|
|
|
1611 tree_estimate_probability (void)
|
|
|
1612 {
|
|
|
1613 basic_block bb;
|
|
|
1614
|
|
|
1615 loop_optimizer_init (0);
|
|
|
1616 if (dump_file && (dump_flags & TDF_DETAILS))
|
|
|
1617 flow_loops_dump (dump_file, NULL, 0);
|
|
|
1618
|
|
|
1619 add_noreturn_fake_exit_edges ();
|
|
|
1620 connect_infinite_loops_to_exit ();
|
|
|
1621 /* We use loop_niter_by_eval, which requires that the loops have
|
|
|
1622 preheaders. */
|
|
|
1623 create_preheaders (CP_SIMPLE_PREHEADERS);
|
|
|
1624 calculate_dominance_info (CDI_POST_DOMINATORS);
|
|
|
1625
|
|
|
1626 bb_predictions = pointer_map_create ();
|
|
|
1627 tree_bb_level_predictions ();
|
|
|
1628
|
|
|
1629 mark_irreducible_loops ();
|
|
|
1630 record_loop_exits ();
|
|
|
1631 if (number_of_loops () > 1)
|
|
|
1632 predict_loops ();
|
|
|
1633
|
|
|
1634 FOR_EACH_BB (bb)
|
|
|
1635 {
|
|
|
1636 edge e;
|
|
|
1637 edge_iterator ei;
|
|
|
1638 gimple last;
|
|
|
1639
|
|
|
1640 FOR_EACH_EDGE (e, ei, bb->succs)
|
|
|
1641 {
|
|
|
1642 /* Predict early returns to be probable, as we've already taken
|
|
|
1643 care for error returns and other cases are often used for
|
|
|
1644 fast paths through function.
|
|
|
1645
|
|
|
1646 Since we've already removed the return statements, we are
|
|
|
1647 looking for CFG like:
|
|
|
1648
|
|
|
1649 if (conditional)
|
|
|
1650 {
|
|
|
1651 ..
|
|
|
1652 goto return_block
|
|
|
1653 }
|
|
|
1654 some other blocks
|
|
|
1655 return_block:
|
|
|
1656 return_stmt. */
|
|
|
1657 if (e->dest != bb->next_bb
|
|
|
1658 && e->dest != EXIT_BLOCK_PTR
|
|
|
1659 && single_succ_p (e->dest)
|
|
|
1660 && single_succ_edge (e->dest)->dest == EXIT_BLOCK_PTR
|
|
|
1661 && (last = last_stmt (e->dest)) != NULL
|
|
|
1662 && gimple_code (last) == GIMPLE_RETURN)
|
|
|
1663 {
|
|
|
1664 edge e1;
|
|
|
1665 edge_iterator ei1;
|
|
|
1666
|
|
|
1667 if (single_succ_p (bb))
|
|
|
1668 {
|
|
|
1669 FOR_EACH_EDGE (e1, ei1, bb->preds)
|
|
|
1670 if (!predicted_by_p (e1->src, PRED_NULL_RETURN)
|
|
|
1671 && !predicted_by_p (e1->src, PRED_CONST_RETURN)
|
|
|
1672 && !predicted_by_p (e1->src, PRED_NEGATIVE_RETURN))
|
|
|
1673 predict_edge_def (e1, PRED_TREE_EARLY_RETURN, NOT_TAKEN);
|
|
|
1674 }
|
|
|
1675 else
|
|
|
1676 if (!predicted_by_p (e->src, PRED_NULL_RETURN)
|
|
|
1677 && !predicted_by_p (e->src, PRED_CONST_RETURN)
|
|
|
1678 && !predicted_by_p (e->src, PRED_NEGATIVE_RETURN))
|
|
|
1679 predict_edge_def (e, PRED_TREE_EARLY_RETURN, NOT_TAKEN);
|
|
|
1680 }
|
|
|
1681
|
|
|
1682 /* Look for block we are guarding (ie we dominate it,
|
|
|
1683 but it doesn't postdominate us). */
|
|
|
1684 if (e->dest != EXIT_BLOCK_PTR && e->dest != bb
|
|
|
1685 && dominated_by_p (CDI_DOMINATORS, e->dest, e->src)
|
|
|
1686 && !dominated_by_p (CDI_POST_DOMINATORS, e->src, e->dest))
|
|
|
1687 {
|
|
|
1688 gimple_stmt_iterator bi;
|
|
|
1689
|
|
|
1690 /* The call heuristic claims that a guarded function call
|
|
|
1691 is improbable. This is because such calls are often used
|
|
|
1692 to signal exceptional situations such as printing error
|
|
|
1693 messages. */
|
|
|
1694 for (bi = gsi_start_bb (e->dest); !gsi_end_p (bi);
|
|
|
1695 gsi_next (&bi))
|
|
|
1696 {
|
|
|
1697 gimple stmt = gsi_stmt (bi);
|
|
|
1698 if (is_gimple_call (stmt)
|
|
|
1699 /* Constant and pure calls are hardly used to signalize
|
|
|
1700 something exceptional. */
|
|
|
1701 && gimple_has_side_effects (stmt))
|
|
|
1702 {
|
|
|
1703 predict_edge_def (e, PRED_CALL, NOT_TAKEN);
|
|
|
1704 break;
|
|
|
1705 }
|
|
|
1706 }
|
|
|
1707 }
|
|
|
1708 }
|
|
|
1709 tree_predict_by_opcode (bb);
|
|
|
1710 }
|
|
|
1711 FOR_EACH_BB (bb)
|
|
|
1712 combine_predictions_for_bb (bb);
|
|
|
1713
|
|
|
1714 #ifdef ENABLE_CHECKING
|
|
|
1715 pointer_map_traverse (bb_predictions, assert_is_empty, NULL);
|
|
|
1716 #endif
|
|
|
1717 pointer_map_destroy (bb_predictions);
|
|
|
1718 bb_predictions = NULL;
|
|
|
1719
|
|
|
1720 estimate_bb_frequencies ();
|
|
|
1721 free_dominance_info (CDI_POST_DOMINATORS);
|
|
|
1722 remove_fake_exit_edges ();
|
|
|
1723 loop_optimizer_finalize ();
|
|
|
1724 if (dump_file && (dump_flags & TDF_DETAILS))
|
|
|
1725 gimple_dump_cfg (dump_file, dump_flags);
|
|
|
1726 if (profile_status == PROFILE_ABSENT)
|
|
|
1727 profile_status = PROFILE_GUESSED;
|
|
|
1728 return 0;
|
|
|
1729 }
|
|
|
1730
|
|
|
1731 /* Predict edges to successors of CUR whose sources are not postdominated by
|
|
|
1732 BB by PRED and recurse to all postdominators. */
|
|
|
1733
|
|
|
1734 static void
|
|
|
1735 predict_paths_for_bb (basic_block cur, basic_block bb,
|
|
|
1736 enum br_predictor pred,
|
|
|
1737 enum prediction taken)
|
|
|
1738 {
|
|
|
1739 edge e;
|
|
|
1740 edge_iterator ei;
|
|
|
1741 basic_block son;
|
|
|
1742
|
|
|
1743 /* We are looking for all edges forming edge cut induced by
|
|
|
1744 set of all blocks postdominated by BB. */
|
|
|
1745 FOR_EACH_EDGE (e, ei, cur->preds)
|
|
|
1746 if (e->src->index >= NUM_FIXED_BLOCKS
|
|
|
1747 && !dominated_by_p (CDI_POST_DOMINATORS, e->src, bb))
|
|
|
1748 {
|
|
|
1749 gcc_assert (bb == cur || dominated_by_p (CDI_POST_DOMINATORS, cur, bb));
|
|
|
1750 predict_edge_def (e, pred, taken);
|
|
|
1751 }
|
|
|
1752 for (son = first_dom_son (CDI_POST_DOMINATORS, cur);
|
|
|
1753 son;
|
|
|
1754 son = next_dom_son (CDI_POST_DOMINATORS, son))
|
|
|
1755 predict_paths_for_bb (son, bb, pred, taken);
|
|
|
1756 }
|
|
|
1757
|
|
|
1758 /* Sets branch probabilities according to PREDiction and
|
|
|
1759 FLAGS. */
|
|
|
1760
|
|
|
1761 static void
|
|
|
1762 predict_paths_leading_to (basic_block bb, enum br_predictor pred,
|
|
|
1763 enum prediction taken)
|
|
|
1764 {
|
|
|
1765 predict_paths_for_bb (bb, bb, pred, taken);
|
|
|
1766 }
|
|
|
1767
|
|
|
1768 /* This is used to carry information about basic blocks. It is
|
|
|
1769 attached to the AUX field of the standard CFG block. */
|
|
|
1770
|
|
|
1771 typedef struct block_info_def
|
|
|
1772 {
|
|
|
1773 /* Estimated frequency of execution of basic_block. */
|
|
|
1774 sreal frequency;
|
|
|
1775
|
|
|
1776 /* To keep queue of basic blocks to process. */
|
|
|
1777 basic_block next;
|
|
|
1778
|
|
|
1779 /* Number of predecessors we need to visit first. */
|
|
|
1780 int npredecessors;
|
|
|
1781 } *block_info;
|
|
|
1782
|
|
|
1783 /* Similar information for edges. */
|
|
|
1784 typedef struct edge_info_def
|
|
|
1785 {
|
|
|
1786 /* In case edge is a loopback edge, the probability edge will be reached
|
|
|
1787 in case header is. Estimated number of iterations of the loop can be
|
|
|
1788 then computed as 1 / (1 - back_edge_prob). */
|
|
|
1789 sreal back_edge_prob;
|
|
|
1790 /* True if the edge is a loopback edge in the natural loop. */
|
|
|
1791 unsigned int back_edge:1;
|
|
|
1792 } *edge_info;
|
|
|
1793
|
|
|
1794 #define BLOCK_INFO(B) ((block_info) (B)->aux)
|
|
|
1795 #define EDGE_INFO(E) ((edge_info) (E)->aux)
|
|
|
1796
|
|
|
1797 /* Helper function for estimate_bb_frequencies.
|
|
|
1798 Propagate the frequencies in blocks marked in
|
|
|
1799 TOVISIT, starting in HEAD. */
|
|
|
1800
|
|
|
1801 static void
|
|
|
1802 propagate_freq (basic_block head, bitmap tovisit)
|
|
|
1803 {
|
|
|
1804 basic_block bb;
|
|
|
1805 basic_block last;
|
|
|
1806 unsigned i;
|
|
|
1807 edge e;
|
|
|
1808 basic_block nextbb;
|
|
|
1809 bitmap_iterator bi;
|
|
|
1810
|
|
|
1811 /* For each basic block we need to visit count number of his predecessors
|
|
|
1812 we need to visit first. */
|
|
|
1813 EXECUTE_IF_SET_IN_BITMAP (tovisit, 0, i, bi)
|
|
|
1814 {
|
|
|
1815 edge_iterator ei;
|
|
|
1816 int count = 0;
|
|
|
1817
|
|
|
1818 /* The outermost "loop" includes the exit block, which we can not
|
|
|
1819 look up via BASIC_BLOCK. Detect this and use EXIT_BLOCK_PTR
|
|
|
1820 directly. Do the same for the entry block. */
|
|
|
1821 bb = BASIC_BLOCK (i);
|
|
|
1822
|
|
|
1823 FOR_EACH_EDGE (e, ei, bb->preds)
|
|
|
1824 {
|
|
|
1825 bool visit = bitmap_bit_p (tovisit, e->src->index);
|
|
|
1826
|
|
|
1827 if (visit && !(e->flags & EDGE_DFS_BACK))
|
|
|
1828 count++;
|
|
|
1829 else if (visit && dump_file && !EDGE_INFO (e)->back_edge)
|
|
|
1830 fprintf (dump_file,
|
|
|
1831 "Irreducible region hit, ignoring edge to %i->%i\n",
|
|
|
1832 e->src->index, bb->index);
|
|
|
1833 }
|
|
|
1834 BLOCK_INFO (bb)->npredecessors = count;
|
|
|
1835 }
|
|
|
1836
|
|
|
1837 memcpy (&BLOCK_INFO (head)->frequency, &real_one, sizeof (real_one));
|
|
|
1838 last = head;
|
|
|
1839 for (bb = head; bb; bb = nextbb)
|
|
|
1840 {
|
|
|
1841 edge_iterator ei;
|
|
|
1842 sreal cyclic_probability, frequency;
|
|
|
1843
|
|
|
1844 memcpy (&cyclic_probability, &real_zero, sizeof (real_zero));
|
|
|
1845 memcpy (&frequency, &real_zero, sizeof (real_zero));
|
|
|
1846
|
|
|
1847 nextbb = BLOCK_INFO (bb)->next;
|
|
|
1848 BLOCK_INFO (bb)->next = NULL;
|
|
|
1849
|
|
|
1850 /* Compute frequency of basic block. */
|
|
|
1851 if (bb != head)
|
|
|
1852 {
|
|
|
1853 #ifdef ENABLE_CHECKING
|
|
|
1854 FOR_EACH_EDGE (e, ei, bb->preds)
|
|
|
1855 gcc_assert (!bitmap_bit_p (tovisit, e->src->index)
|
|
|
1856 || (e->flags & EDGE_DFS_BACK));
|
|
|
1857 #endif
|
|
|
1858
|
|
|
1859 FOR_EACH_EDGE (e, ei, bb->preds)
|
|
|
1860 if (EDGE_INFO (e)->back_edge)
|
|
|
1861 {
|
|
|
1862 sreal_add (&cyclic_probability, &cyclic_probability,
|
|
|
1863 &EDGE_INFO (e)->back_edge_prob);
|
|
|
1864 }
|
|
|
1865 else if (!(e->flags & EDGE_DFS_BACK))
|
|
|
1866 {
|
|
|
1867 sreal tmp;
|
|
|
1868
|
|
|
1869 /* frequency += (e->probability
|
|
|
1870 * BLOCK_INFO (e->src)->frequency /
|
|
|
1871 REG_BR_PROB_BASE); */
|
|
|
1872
|
|
|
1873 sreal_init (&tmp, e->probability, 0);
|
|
|
1874 sreal_mul (&tmp, &tmp, &BLOCK_INFO (e->src)->frequency);
|
|
|
1875 sreal_mul (&tmp, &tmp, &real_inv_br_prob_base);
|
|
|
1876 sreal_add (&frequency, &frequency, &tmp);
|
|
|
1877 }
|
|
|
1878
|
|
|
1879 if (sreal_compare (&cyclic_probability, &real_zero) == 0)
|
|
|
1880 {
|
|
|
1881 memcpy (&BLOCK_INFO (bb)->frequency, &frequency,
|
|
|
1882 sizeof (frequency));
|
|
|
1883 }
|
|
|
1884 else
|
|
|
1885 {
|
|
|
1886 if (sreal_compare (&cyclic_probability, &real_almost_one) > 0)
|
|
|
1887 {
|
|
|
1888 memcpy (&cyclic_probability, &real_almost_one,
|
|
|
1889 sizeof (real_almost_one));
|
|
|
1890 }
|
|
|
1891
|
|
|
1892 /* BLOCK_INFO (bb)->frequency = frequency
|
|
|
1893 / (1 - cyclic_probability) */
|
|
|
1894
|
|
|
1895 sreal_sub (&cyclic_probability, &real_one, &cyclic_probability);
|
|
|
1896 sreal_div (&BLOCK_INFO (bb)->frequency,
|
|
|
1897 &frequency, &cyclic_probability);
|
|
|
1898 }
|
|
|
1899 }
|
|
|
1900
|
|
|
1901 bitmap_clear_bit (tovisit, bb->index);
|
|
|
1902
|
|
|
1903 e = find_edge (bb, head);
|
|
|
1904 if (e)
|
|
|
1905 {
|
|
|
1906 sreal tmp;
|
|
|
1907
|
|
|
1908 /* EDGE_INFO (e)->back_edge_prob
|
|
|
1909 = ((e->probability * BLOCK_INFO (bb)->frequency)
|
|
|
1910 / REG_BR_PROB_BASE); */
|
|
|
1911
|
|
|
1912 sreal_init (&tmp, e->probability, 0);
|
|
|
1913 sreal_mul (&tmp, &tmp, &BLOCK_INFO (bb)->frequency);
|
|
|
1914 sreal_mul (&EDGE_INFO (e)->back_edge_prob,
|
|
|
1915 &tmp, &real_inv_br_prob_base);
|
|
|
1916 }
|
|
|
1917
|
|
|
1918 /* Propagate to successor blocks. */
|
|
|
1919 FOR_EACH_EDGE (e, ei, bb->succs)
|
|
|
1920 if (!(e->flags & EDGE_DFS_BACK)
|
|
|
1921 && BLOCK_INFO (e->dest)->npredecessors)
|
|
|
1922 {
|
|
|
1923 BLOCK_INFO (e->dest)->npredecessors--;
|
|
|
1924 if (!BLOCK_INFO (e->dest)->npredecessors)
|
|
|
1925 {
|
|
|
1926 if (!nextbb)
|
|
|
1927 nextbb = e->dest;
|
|
|
1928 else
|
|
|
1929 BLOCK_INFO (last)->next = e->dest;
|
|
|
1930
|
|
|
1931 last = e->dest;
|
|
|
1932 }
|
|
|
1933 }
|
|
|
1934 }
|
|
|
1935 }
|
|
|
1936
|
|
|
1937 /* Estimate probabilities of loopback edges in loops at same nest level. */
|
|
|
1938
|
|
|
1939 static void
|
|
|
1940 estimate_loops_at_level (struct loop *first_loop)
|
|
|
1941 {
|
|
|
1942 struct loop *loop;
|
|
|
1943
|
|
|
1944 for (loop = first_loop; loop; loop = loop->next)
|
|
|
1945 {
|
|
|
1946 edge e;
|
|
|
1947 basic_block *bbs;
|
|
|
1948 unsigned i;
|
|
|
1949 bitmap tovisit = BITMAP_ALLOC (NULL);
|
|
|
1950
|
|
|
1951 estimate_loops_at_level (loop->inner);
|
|
|
1952
|
|
|
1953 /* Find current loop back edge and mark it. */
|
|
|
1954 e = loop_latch_edge (loop);
|
|
|
1955 EDGE_INFO (e)->back_edge = 1;
|
|
|
1956
|
|
|
1957 bbs = get_loop_body (loop);
|
|
|
1958 for (i = 0; i < loop->num_nodes; i++)
|
|
|
1959 bitmap_set_bit (tovisit, bbs[i]->index);
|
|
|
1960 free (bbs);
|
|
|
1961 propagate_freq (loop->header, tovisit);
|
|
|
1962 BITMAP_FREE (tovisit);
|
|
|
1963 }
|
|
|
1964 }
|
|
|
1965
|
|
|
1966 /* Propagates frequencies through structure of loops. */
|
|
|
1967
|
|
|
1968 static void
|
|
|
1969 estimate_loops (void)
|
|
|
1970 {
|
|
|
1971 bitmap tovisit = BITMAP_ALLOC (NULL);
|
|
|
1972 basic_block bb;
|
|
|
1973
|
|
|
1974 /* Start by estimating the frequencies in the loops. */
|
|
|
1975 if (number_of_loops () > 1)
|
|
|
1976 estimate_loops_at_level (current_loops->tree_root->inner);
|
|
|
1977
|
|
|
1978 /* Now propagate the frequencies through all the blocks. */
|
|
|
1979 FOR_ALL_BB (bb)
|
|
|
1980 {
|
|
|
1981 bitmap_set_bit (tovisit, bb->index);
|
|
|
1982 }
|
|
|
1983 propagate_freq (ENTRY_BLOCK_PTR, tovisit);
|
|
|
1984 BITMAP_FREE (tovisit);
|
|
|
1985 }
|
|
|
1986
|
|
|
1987 /* Convert counts measured by profile driven feedback to frequencies.
|
|
|
1988 Return nonzero iff there was any nonzero execution count. */
|
|
|
1989
|
|
|
1990 int
|
|
|
1991 counts_to_freqs (void)
|
|
|
1992 {
|
|
|
1993 gcov_type count_max, true_count_max = 0;
|
|
|
1994 basic_block bb;
|
|
|
1995
|
|
|
1996 FOR_EACH_BB (bb)
|
|
|
1997 true_count_max = MAX (bb->count, true_count_max);
|
|
|
1998
|
|
|
1999 count_max = MAX (true_count_max, 1);
|
|
|
2000 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
|
|
|
2001 bb->frequency = (bb->count * BB_FREQ_MAX + count_max / 2) / count_max;
|
|
|
2002
|
|
|
2003 return true_count_max;
|
|
|
2004 }
|
|
|
2005
|
|
|
2006 /* Return true if function is likely to be expensive, so there is no point to
|
|
|
2007 optimize performance of prologue, epilogue or do inlining at the expense
|
|
|
2008 of code size growth. THRESHOLD is the limit of number of instructions
|
|
|
2009 function can execute at average to be still considered not expensive. */
|
|
|
2010
|
|
|
2011 bool
|
|
|
2012 expensive_function_p (int threshold)
|
|
|
2013 {
|
|
|
2014 unsigned int sum = 0;
|
|
|
2015 basic_block bb;
|
|
|
2016 unsigned int limit;
|
|
|
2017
|
|
|
2018 /* We can not compute accurately for large thresholds due to scaled
|
|
|
2019 frequencies. */
|
|
|
2020 gcc_assert (threshold <= BB_FREQ_MAX);
|
|
|
2021
|
|
|
2022 /* Frequencies are out of range. This either means that function contains
|
|
|
2023 internal loop executing more than BB_FREQ_MAX times or profile feedback
|
|
|
2024 is available and function has not been executed at all. */
|
|
|
2025 if (ENTRY_BLOCK_PTR->frequency == 0)
|
|
|
2026 return true;
|
|
|
2027
|
|
|
2028 /* Maximally BB_FREQ_MAX^2 so overflow won't happen. */
|
|
|
2029 limit = ENTRY_BLOCK_PTR->frequency * threshold;
|
|
|
2030 FOR_EACH_BB (bb)
|
|
|
2031 {
|
|
|
2032 rtx insn;
|
|
|
2033
|
|
|
2034 for (insn = BB_HEAD (bb); insn != NEXT_INSN (BB_END (bb));
|
|
|
2035 insn = NEXT_INSN (insn))
|
|
|
2036 if (active_insn_p (insn))
|
|
|
2037 {
|
|
|
2038 sum += bb->frequency;
|
|
|
2039 if (sum > limit)
|
|
|
2040 return true;
|
|
|
2041 }
|
|
|
2042 }
|
|
|
2043
|
|
|
2044 return false;
|
|
|
2045 }
|
|
|
2046
|
|
|
2047 /* Estimate basic blocks frequency by given branch probabilities. */
|
|
|
2048
|
|
|
2049 void
|
|
|
2050 estimate_bb_frequencies (void)
|
|
|
2051 {
|
|
|
2052 basic_block bb;
|
|
|
2053 sreal freq_max;
|
|
|
2054
|
|
|
2055 if (profile_status != PROFILE_READ || !counts_to_freqs ())
|
|
|
2056 {
|
|
|
2057 static int real_values_initialized = 0;
|
|
|
2058
|
|
|
2059 if (!real_values_initialized)
|
|
|
2060 {
|
|
|
2061 real_values_initialized = 1;
|
|
|
2062 sreal_init (&real_zero, 0, 0);
|
|
|
2063 sreal_init (&real_one, 1, 0);
|
|
|
2064 sreal_init (&real_br_prob_base, REG_BR_PROB_BASE, 0);
|
|
|
2065 sreal_init (&real_bb_freq_max, BB_FREQ_MAX, 0);
|
|
|
2066 sreal_init (&real_one_half, 1, -1);
|
|
|
2067 sreal_div (&real_inv_br_prob_base, &real_one, &real_br_prob_base);
|
|
|
2068 sreal_sub (&real_almost_one, &real_one, &real_inv_br_prob_base);
|
|
|
2069 }
|
|
|
2070
|
|
|
2071 mark_dfs_back_edges ();
|
|
|
2072
|
|
|
2073 single_succ_edge (ENTRY_BLOCK_PTR)->probability = REG_BR_PROB_BASE;
|
|
|
2074
|
|
|
2075 /* Set up block info for each basic block. */
|
|
|
2076 alloc_aux_for_blocks (sizeof (struct block_info_def));
|
|
|
2077 alloc_aux_for_edges (sizeof (struct edge_info_def));
|
|
|
2078 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
|
|
|
2079 {
|
|
|
2080 edge e;
|
|
|
2081 edge_iterator ei;
|
|
|
2082
|
|
|
2083 FOR_EACH_EDGE (e, ei, bb->succs)
|
|
|
2084 {
|
|
|
2085 sreal_init (&EDGE_INFO (e)->back_edge_prob, e->probability, 0);
|
|
|
2086 sreal_mul (&EDGE_INFO (e)->back_edge_prob,
|
|
|
2087 &EDGE_INFO (e)->back_edge_prob,
|
|
|
2088 &real_inv_br_prob_base);
|
|
|
2089 }
|
|
|
2090 }
|
|
|
2091
|
|
|
2092 /* First compute probabilities locally for each loop from innermost
|
|
|
2093 to outermost to examine probabilities for back edges. */
|
|
|
2094 estimate_loops ();
|
|
|
2095
|
|
|
2096 memcpy (&freq_max, &real_zero, sizeof (real_zero));
|
|
|
2097 FOR_EACH_BB (bb)
|
|
|
2098 if (sreal_compare (&freq_max, &BLOCK_INFO (bb)->frequency) < 0)
|
|
|
2099 memcpy (&freq_max, &BLOCK_INFO (bb)->frequency, sizeof (freq_max));
|
|
|
2100
|
|
|
2101 sreal_div (&freq_max, &real_bb_freq_max, &freq_max);
|
|
|
2102 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
|
|
|
2103 {
|
|
|
2104 sreal tmp;
|
|
|
2105
|
|
|
2106 sreal_mul (&tmp, &BLOCK_INFO (bb)->frequency, &freq_max);
|
|
|
2107 sreal_add (&tmp, &tmp, &real_one_half);
|
|
|
2108 bb->frequency = sreal_to_int (&tmp);
|
|
|
2109 }
|
|
|
2110
|
|
|
2111 free_aux_for_blocks ();
|
|
|
2112 free_aux_for_edges ();
|
|
|
2113 }
|
|
|
2114 compute_function_frequency ();
|
|
|
2115 if (flag_reorder_functions)
|
|
|
2116 choose_function_section ();
|
|
|
2117 }
|
|
|
2118
|
|
|
2119 /* Decide whether function is hot, cold or unlikely executed. */
|
|
|
2120 static void
|
|
|
2121 compute_function_frequency (void)
|
|
|
2122 {
|
|
|
2123 basic_block bb;
|
|
|
2124
|
|
|
2125 if (!profile_info || !flag_branch_probabilities)
|
|
|
2126 {
|
|
|
2127 if (lookup_attribute ("cold", DECL_ATTRIBUTES (current_function_decl))
|
|
|
2128 != NULL)
|
|
|
2129 cfun->function_frequency = FUNCTION_FREQUENCY_UNLIKELY_EXECUTED;
|
|
|
2130 else if (lookup_attribute ("hot", DECL_ATTRIBUTES (current_function_decl))
|
|
|
2131 != NULL)
|
|
|
2132 cfun->function_frequency = FUNCTION_FREQUENCY_HOT;
|
|
|
2133 return;
|
|
|
2134 }
|
|
|
2135 cfun->function_frequency = FUNCTION_FREQUENCY_UNLIKELY_EXECUTED;
|
|
|
2136 FOR_EACH_BB (bb)
|
|
|
2137 {
|
|
|
2138 if (maybe_hot_bb_p (bb))
|
|
|
2139 {
|
|
|
2140 cfun->function_frequency = FUNCTION_FREQUENCY_HOT;
|
|
|
2141 return;
|
|
|
2142 }
|
|
|
2143 if (!probably_never_executed_bb_p (bb))
|
|
|
2144 cfun->function_frequency = FUNCTION_FREQUENCY_NORMAL;
|
|
|
2145 }
|
|
|
2146 }
|
|
|
2147
|
|
|
2148 /* Choose appropriate section for the function. */
|
|
|
2149 static void
|
|
|
2150 choose_function_section (void)
|
|
|
2151 {
|
|
|
2152 if (DECL_SECTION_NAME (current_function_decl)
|
|
|
2153 || !targetm.have_named_sections
|
|
|
2154 /* Theoretically we can split the gnu.linkonce text section too,
|
|
|
2155 but this requires more work as the frequency needs to match
|
|
|
2156 for all generated objects so we need to merge the frequency
|
|
|
2157 of all instances. For now just never set frequency for these. */
|
|
|
2158 || DECL_ONE_ONLY (current_function_decl))
|
|
|
2159 return;
|
|
|
2160
|
|
|
2161 /* If we are doing the partitioning optimization, let the optimization
|
|
|
2162 choose the correct section into which to put things. */
|
|
|
2163
|
|
|
2164 if (flag_reorder_blocks_and_partition)
|
|
|
2165 return;
|
|
|
2166
|
|
|
2167 if (cfun->function_frequency == FUNCTION_FREQUENCY_HOT)
|
|
|
2168 DECL_SECTION_NAME (current_function_decl) =
|
|
|
2169 build_string (strlen (HOT_TEXT_SECTION_NAME), HOT_TEXT_SECTION_NAME);
|
|
|
2170 if (cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED)
|
|
|
2171 DECL_SECTION_NAME (current_function_decl) =
|
|
|
2172 build_string (strlen (UNLIKELY_EXECUTED_TEXT_SECTION_NAME),
|
|
|
2173 UNLIKELY_EXECUTED_TEXT_SECTION_NAME);
|
|
|
2174 }
|
|
|
2175
|
|
|
2176 static bool
|
|
|
2177 gate_estimate_probability (void)
|
|
|
2178 {
|
|
|
2179 return flag_guess_branch_prob;
|
|
|
2180 }
|
|
|
2181
|
|
|
2182 /* Build PREDICT_EXPR. */
|
|
|
2183 tree
|
|
|
2184 build_predict_expr (enum br_predictor predictor, enum prediction taken)
|
|
|
2185 {
|
|
|
2186 tree t = build1 (PREDICT_EXPR, void_type_node,
|
|
|
2187 build_int_cst (NULL, predictor));
|
|
|
2188 PREDICT_EXPR_OUTCOME (t) = taken;
|
|
|
2189 return t;
|
|
|
2190 }
|
|
|
2191
|
|
|
2192 const char *
|
|
|
2193 predictor_name (enum br_predictor predictor)
|
|
|
2194 {
|
|
|
2195 return predictor_info[predictor].name;
|
|
|
2196 }
|
|
|
2197
|
|
|
2198 struct gimple_opt_pass pass_profile =
|
|
|
2199 {
|
|
|
2200 {
|
|
|
2201 GIMPLE_PASS,
|
|
|
2202 "profile", /* name */
|
|
|
2203 gate_estimate_probability, /* gate */
|
|
|
2204 tree_estimate_probability, /* execute */
|
|
|
2205 NULL, /* sub */
|
|
|
2206 NULL, /* next */
|
|
|
2207 0, /* static_pass_number */
|
|
|
2208 TV_BRANCH_PROB, /* tv_id */
|
|
|
2209 PROP_cfg, /* properties_required */
|
|
|
2210 0, /* properties_provided */
|
|
|
2211 0, /* properties_destroyed */
|
|
|
2212 0, /* todo_flags_start */
|
|
|
2213 TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */
|
|
|
2214 }
|
|
|
2215 };
|
|
|
2216
|
|
|
2217 struct gimple_opt_pass pass_strip_predict_hints =
|
|
|
2218 {
|
|
|
2219 {
|
|
|
2220 GIMPLE_PASS,
|
|
|
2221 NULL, /* name */
|
|
|
2222 NULL, /* gate */
|
|
|
2223 strip_predict_hints, /* execute */
|
|
|
2224 NULL, /* sub */
|
|
|
2225 NULL, /* next */
|
|
|
2226 0, /* static_pass_number */
|
|
|
2227 TV_BRANCH_PROB, /* tv_id */
|
|
|
2228 PROP_cfg, /* properties_required */
|
|
|
2229 0, /* properties_provided */
|
|
|
2230 0, /* properties_destroyed */
|
|
|
2231 0, /* todo_flags_start */
|
|
|
2232 TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */
|
|
|
2233 }
|
|
|
2234 };
|
