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131
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1 /* Tree switch conversion for GNU compiler.
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2 Copyright (C) 2017 Free Software Foundation, Inc.
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3
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4 This file is part of GCC.
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5
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6 GCC is free software; you can redistribute it and/or modify it under
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7 the terms of the GNU General Public License as published by the Free
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8 Software Foundation; either version 3, or (at your option) any later
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9 version.
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10
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11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
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13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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14 for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with GCC; see the file COPYING3. If not see
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18 <http://www.gnu.org/licenses/>. */
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19
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20 #ifndef TREE_SWITCH_CONVERSION_H
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21 #define TREE_SWITCH_CONVERSION_H
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22
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23 namespace tree_switch_conversion {
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24
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25 /* Type of cluster. */
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26
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27 enum cluster_type
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28 {
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29 SIMPLE_CASE,
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30 JUMP_TABLE,
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31 BIT_TEST
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32 };
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33
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34 #define PRINT_CASE(f,c) print_generic_expr (f, c)
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35
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36 /* Abstract base class for representing a cluster of cases.
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37
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38 Here is the inheritance hierarachy, and the enum_cluster_type
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39 values for the concrete subclasses:
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40
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41 cluster
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42 |-simple_cluster (SIMPLE_CASE)
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43 `-group_cluster
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44 |-jump_table_cluster (JUMP_TABLE)
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45 `-bit_test_cluster (BIT_TEST). */
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46
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47 struct cluster
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48 {
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49 /* Constructor. */
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50 cluster (tree case_label_expr, basic_block case_bb, profile_probability prob,
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51 profile_probability subtree_prob);
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52
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53 /* Destructor. */
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54 virtual ~cluster ()
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55 {}
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56
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57 /* Return type. */
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58 virtual cluster_type get_type () = 0;
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59
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60 /* Get low value covered by a cluster. */
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61 virtual tree get_low () = 0;
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62
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63 /* Get high value covered by a cluster. */
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64 virtual tree get_high () = 0;
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65
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66 /* Debug content of a cluster. */
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67 virtual void debug () = 0;
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68
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69 /* Dump content of a cluster. */
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70 virtual void dump (FILE *f, bool details = false) = 0;
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71
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72 /* Emit GIMPLE code to handle the cluster. */
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73 virtual void emit (tree, tree, tree, basic_block) = 0;
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74
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75 /* Return true if a cluster handles only a single case value and the
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76 value is not a range. */
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77 virtual bool is_single_value_p ()
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78 {
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79 return false;
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80 }
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81
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82 /* Return range of a cluster. If value would overflow in type of LOW,
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83 then return 0. */
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84 static unsigned HOST_WIDE_INT get_range (tree low, tree high)
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85 {
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86 tree r = fold_build2 (MINUS_EXPR, TREE_TYPE (low), high, low);
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87 if (!tree_fits_uhwi_p (r))
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88 return 0;
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89
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90 return tree_to_uhwi (r) + 1;
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91 }
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92
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93 /* Case label. */
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94 tree m_case_label_expr;
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95
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96 /* Basic block of the case. */
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97 basic_block m_case_bb;
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98
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99 /* Probability of taking this cluster. */
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100 profile_probability m_prob;
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101
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102 /* Probability of reaching subtree rooted at this node. */
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103 profile_probability m_subtree_prob;
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104
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105 protected:
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106 /* Default constructor. */
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107 cluster () {}
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108 };
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109
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110 cluster::cluster (tree case_label_expr, basic_block case_bb,
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111 profile_probability prob, profile_probability subtree_prob):
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112 m_case_label_expr (case_label_expr), m_case_bb (case_bb), m_prob (prob),
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113 m_subtree_prob (subtree_prob)
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114 {
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115 }
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116
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117 /* Subclass of cluster representing a simple contiguous range
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118 from [low..high]. */
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119
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120 struct simple_cluster: public cluster
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121 {
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122 /* Constructor. */
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123 simple_cluster (tree low, tree high, tree case_label_expr,
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124 basic_block case_bb, profile_probability prob);
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125
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126 /* Destructor. */
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127 ~simple_cluster ()
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128 {}
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129
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130 cluster_type
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131 get_type ()
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132 {
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133 return SIMPLE_CASE;
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134 }
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135
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136 tree
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137 get_low ()
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138 {
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139 return m_low;
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140 }
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141
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142 tree
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143 get_high ()
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144 {
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145 return m_high;
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146 }
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147
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148 void
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149 debug ()
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150 {
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151 dump (stderr);
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152 }
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153
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154 void
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155 dump (FILE *f, bool details ATTRIBUTE_UNUSED = false)
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156 {
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157 PRINT_CASE (f, get_low ());
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158 if (get_low () != get_high ())
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159 {
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160 fprintf (f, "-");
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161 PRINT_CASE (f, get_high ());
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162 }
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163 fprintf (f, " ");
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164 }
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165
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166 void emit (tree, tree, tree, basic_block)
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167 {
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168 gcc_unreachable ();
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169 }
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170
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171 bool is_single_value_p ()
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172 {
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173 return tree_int_cst_equal (get_low (), get_high ());
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174 }
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175
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176 /* Low value of the case. */
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177 tree m_low;
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178
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179 /* High value of the case. */
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180 tree m_high;
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181
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182 /* True if case is a range. */
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183 bool m_range_p;
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184 };
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185
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186 simple_cluster::simple_cluster (tree low, tree high, tree case_label_expr,
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187 basic_block case_bb, profile_probability prob):
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188 cluster (case_label_expr, case_bb, prob, prob),
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189 m_low (low), m_high (high)
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190 {
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191 m_range_p = m_high != NULL;
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192 if (m_high == NULL)
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193 m_high = m_low;
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194 }
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195
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196 /* Abstract subclass of jump table and bit test cluster,
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197 handling a collection of simple_cluster instances. */
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198
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199 struct group_cluster: public cluster
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200 {
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201 /* Constructor. */
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202 group_cluster (vec<cluster *> &clusters, unsigned start, unsigned end);
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203
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204 /* Destructor. */
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205 ~group_cluster ();
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206
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207 tree
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208 get_low ()
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209 {
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210 return m_cases[0]->get_low ();
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211 }
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212
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213 tree
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214 get_high ()
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215 {
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216 return m_cases[m_cases.length () - 1]->get_high ();
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217 }
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218
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219 void
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220 debug ()
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221 {
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222 dump (stderr);
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223 }
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224
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225 void dump (FILE *f, bool details = false);
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226
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227 /* List of simple clusters handled by the group. */
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228 vec<simple_cluster *> m_cases;
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229 };
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230
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231 /* Concrete subclass of group_cluster representing a collection
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232 of cases to be implemented as a jump table.
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233 The "emit" vfunc gernerates a nested switch statement which
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234 is later lowered to a jump table. */
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235
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236 struct jump_table_cluster: public group_cluster
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237 {
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238 /* Constructor. */
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239 jump_table_cluster (vec<cluster *> &clusters, unsigned start, unsigned end)
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240 : group_cluster (clusters, start, end)
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241 {}
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242
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243 cluster_type
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244 get_type ()
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245 {
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246 return JUMP_TABLE;
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247 }
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248
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249 void emit (tree index_expr, tree index_type,
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250 tree default_label_expr, basic_block default_bb);
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251
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252 /* Find jump tables of given CLUSTERS, where all members of the vector
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253 are of type simple_cluster. New clusters are returned. */
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254 static vec<cluster *> find_jump_tables (vec<cluster *> &clusters);
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255
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256 /* Return true when cluster starting at START and ending at END (inclusive)
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257 can build a jump-table. */
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258 static bool can_be_handled (const vec<cluster *> &clusters, unsigned start,
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259 unsigned end);
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260
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261 /* Return true if cluster starting at START and ending at END (inclusive)
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262 is profitable transformation. */
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263 static bool is_beneficial (const vec<cluster *> &clusters, unsigned start,
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264 unsigned end);
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265
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266 /* Return the smallest number of different values for which it is best
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267 to use a jump-table instead of a tree of conditional branches. */
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268 static inline unsigned int case_values_threshold (void);
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269
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270 /* Return whether jump table expansion is allowed. */
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271 static bool is_enabled (void);
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272
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273 /* Max growth ratio for code that is optimized for size. */
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274 static const unsigned HOST_WIDE_INT max_ratio_for_size = 3;
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275
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276 /* Max growth ratio for code that is optimized for speed. */
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277 static const unsigned HOST_WIDE_INT max_ratio_for_speed = 8;
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278 };
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279
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280 /* A GIMPLE switch statement can be expanded to a short sequence of bit-wise
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281 comparisons. "switch(x)" is converted into "if ((1 << (x-MINVAL)) & CST)"
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282 where CST and MINVAL are integer constants. This is better than a series
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283 of compare-and-banch insns in some cases, e.g. we can implement:
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284
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285 if ((x==4) || (x==6) || (x==9) || (x==11))
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286
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287 as a single bit test:
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288
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289 if ((1<<x) & ((1<<4)|(1<<6)|(1<<9)|(1<<11)))
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290
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291 This transformation is only applied if the number of case targets is small,
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292 if CST constains at least 3 bits, and "1 << x" is cheap. The bit tests are
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293 performed in "word_mode".
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294
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295 The following example shows the code the transformation generates:
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296
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297 int bar(int x)
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298 {
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299 switch (x)
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300 {
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301 case '0': case '1': case '2': case '3': case '4':
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302 case '5': case '6': case '7': case '8': case '9':
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303 case 'A': case 'B': case 'C': case 'D': case 'E':
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304 case 'F':
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305 return 1;
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306 }
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307 return 0;
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308 }
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309
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310 ==>
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311
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312 bar (int x)
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313 {
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314 tmp1 = x - 48;
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315 if (tmp1 > (70 - 48)) goto L2;
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316 tmp2 = 1 << tmp1;
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317 tmp3 = 0b11111100000001111111111;
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318 if ((tmp2 & tmp3) != 0) goto L1 ; else goto L2;
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319 L1:
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320 return 1;
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321 L2:
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322 return 0;
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323 }
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324
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325 TODO: There are still some improvements to this transformation that could
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326 be implemented:
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327
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328 * A narrower mode than word_mode could be used if that is cheaper, e.g.
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329 for x86_64 where a narrower-mode shift may result in smaller code.
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330
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331 * The compounded constant could be shifted rather than the one. The
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332 test would be either on the sign bit or on the least significant bit,
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333 depending on the direction of the shift. On some machines, the test
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334 for the branch would be free if the bit to test is already set by the
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335 shift operation.
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336
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337 This transformation was contributed by Roger Sayle, see this e-mail:
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338 http://gcc.gnu.org/ml/gcc-patches/2003-01/msg01950.html
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339 */
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340
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341 struct bit_test_cluster: public group_cluster
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342 {
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343 /* Constructor. */
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344 bit_test_cluster (vec<cluster *> &clusters, unsigned start, unsigned end,
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345 bool handles_entire_switch)
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346 :group_cluster (clusters, start, end),
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347 m_handles_entire_switch (handles_entire_switch)
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348 {}
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349
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350 cluster_type
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351 get_type ()
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352 {
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353 return BIT_TEST;
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354 }
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355
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356 /* Expand a switch statement by a short sequence of bit-wise
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357 comparisons. "switch(x)" is effectively converted into
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358 "if ((1 << (x-MINVAL)) & CST)" where CST and MINVAL are
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359 integer constants.
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360
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361 INDEX_EXPR is the value being switched on.
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362
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363 MINVAL is the lowest case value of in the case nodes,
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364 and RANGE is highest value minus MINVAL. MINVAL and RANGE
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365 are not guaranteed to be of the same type as INDEX_EXPR
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366 (the gimplifier doesn't change the type of case label values,
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367 and MINVAL and RANGE are derived from those values).
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368 MAXVAL is MINVAL + RANGE.
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369
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370 There *MUST* be max_case_bit_tests or less unique case
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371 node targets. */
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372 void emit (tree index_expr, tree index_type,
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373 tree default_label_expr, basic_block default_bb);
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374
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375 /* Find bit tests of given CLUSTERS, where all members of the vector
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376 are of type simple_cluster. New clusters are returned. */
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377 static vec<cluster *> find_bit_tests (vec<cluster *> &clusters);
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378
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379 /* Return true when RANGE of case values with UNIQ labels
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380 can build a bit test. */
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381 static bool can_be_handled (unsigned HOST_WIDE_INT range, unsigned uniq);
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382
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383 /* Return true when cluster starting at START and ending at END (inclusive)
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384 can build a bit test. */
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385 static bool can_be_handled (const vec<cluster *> &clusters, unsigned start,
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386 unsigned end);
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387
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388 /* Return true when COUNT of cases of UNIQ labels is beneficial for bit test
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389 transformation. */
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390 static bool is_beneficial (unsigned count, unsigned uniq);
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391
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392 /* Return true if cluster starting at START and ending at END (inclusive)
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393 is profitable transformation. */
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394 static bool is_beneficial (const vec<cluster *> &clusters, unsigned start,
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395 unsigned end);
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396
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397 /* Split the basic block at the statement pointed to by GSIP, and insert
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398 a branch to the target basic block of E_TRUE conditional on tree
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399 expression COND.
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400
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401 It is assumed that there is already an edge from the to-be-split
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402 basic block to E_TRUE->dest block. This edge is removed, and the
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403 profile information on the edge is re-used for the new conditional
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404 jump.
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405
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406 The CFG is updated. The dominator tree will not be valid after
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407 this transformation, but the immediate dominators are updated if
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408 UPDATE_DOMINATORS is true.
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409
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410 Returns the newly created basic block. */
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411 static basic_block hoist_edge_and_branch_if_true (gimple_stmt_iterator *gsip,
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412 tree cond,
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413 basic_block case_bb,
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414 profile_probability prob);
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415
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416 /* True when the jump table handles an entire switch statement. */
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417 bool m_handles_entire_switch;
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418
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419 /* Maximum number of different basic blocks that can be handled by
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420 a bit test. */
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421 static const int m_max_case_bit_tests = 3;
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422 };
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423
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424 /* Helper struct to find minimal clusters. */
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425
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426 struct min_cluster_item
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427 {
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428 /* Constructor. */
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429 min_cluster_item (unsigned count, unsigned start, unsigned non_jt_cases):
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430 m_count (count), m_start (start), m_non_jt_cases (non_jt_cases)
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431 {}
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432
|
|
|
433 /* Count of clusters. */
|
|
|
434 unsigned m_count;
|
|
|
435
|
|
|
436 /* Index where is cluster boundary. */
|
|
|
437 unsigned m_start;
|
|
|
438
|
|
|
439 /* Total number of cases that will not be in a jump table. */
|
|
|
440 unsigned m_non_jt_cases;
|
|
|
441 };
|
|
|
442
|
|
|
443 /* Helper struct to represent switch decision tree. */
|
|
|
444
|
|
|
445 struct case_tree_node
|
|
|
446 {
|
|
|
447 /* Empty Constructor. */
|
|
|
448 case_tree_node ();
|
|
|
449
|
|
|
450 /* Return true when it has a child. */
|
|
|
451 bool has_child ()
|
|
|
452 {
|
|
|
453 return m_left != NULL || m_right != NULL;
|
|
|
454 }
|
|
|
455
|
|
|
456 /* Left son in binary tree. */
|
|
|
457 case_tree_node *m_left;
|
|
|
458
|
|
|
459 /* Right son in binary tree; also node chain. */
|
|
|
460 case_tree_node *m_right;
|
|
|
461
|
|
|
462 /* Parent of node in binary tree. */
|
|
|
463 case_tree_node *m_parent;
|
|
|
464
|
|
|
465 /* Cluster represented by this tree node. */
|
|
|
466 cluster *m_c;
|
|
|
467 };
|
|
|
468
|
|
|
469 inline
|
|
|
470 case_tree_node::case_tree_node ():
|
|
|
471 m_left (NULL), m_right (NULL), m_parent (NULL), m_c (NULL)
|
|
|
472 {
|
|
|
473 }
|
|
|
474
|
|
|
475 unsigned int
|
|
|
476 jump_table_cluster::case_values_threshold (void)
|
|
|
477 {
|
|
|
478 unsigned int threshold = PARAM_VALUE (PARAM_CASE_VALUES_THRESHOLD);
|
|
|
479
|
|
|
480 if (threshold == 0)
|
|
|
481 threshold = targetm.case_values_threshold ();
|
|
|
482
|
|
|
483 return threshold;
|
|
|
484 }
|
|
|
485
|
|
|
486 /* Return whether jump table expansion is allowed. */
|
|
|
487 bool jump_table_cluster::is_enabled (void)
|
|
|
488 {
|
|
|
489 /* If neither casesi or tablejump is available, or flag_jump_tables
|
|
|
490 over-ruled us, we really have no choice. */
|
|
|
491 if (!targetm.have_casesi () && !targetm.have_tablejump ())
|
|
|
492 return false;
|
|
|
493 if (!flag_jump_tables)
|
|
|
494 return false;
|
|
|
495 #ifndef ASM_OUTPUT_ADDR_DIFF_ELT
|
|
|
496 if (flag_pic)
|
|
|
497 return false;
|
|
|
498 #endif
|
|
|
499
|
|
|
500 return true;
|
|
|
501 }
|
|
|
502
|
|
|
503 /* A case_bit_test represents a set of case nodes that may be
|
|
|
504 selected from using a bit-wise comparison. HI and LO hold
|
|
|
505 the integer to be tested against, TARGET_EDGE contains the
|
|
|
506 edge to the basic block to jump to upon success and BITS
|
|
|
507 counts the number of case nodes handled by this test,
|
|
|
508 typically the number of bits set in HI:LO. The LABEL field
|
|
|
509 is used to quickly identify all cases in this set without
|
|
|
510 looking at label_to_block for every case label. */
|
|
|
511
|
|
|
512 struct case_bit_test
|
|
|
513 {
|
|
|
514 wide_int mask;
|
|
|
515 basic_block target_bb;
|
|
|
516 tree label;
|
|
|
517 int bits;
|
|
|
518
|
|
|
519 /* Comparison function for qsort to order bit tests by decreasing
|
|
|
520 probability of execution. */
|
|
|
521 static int cmp (const void *p1, const void *p2);
|
|
|
522 };
|
|
|
523
|
|
|
524 struct switch_decision_tree
|
|
|
525 {
|
|
|
526 /* Constructor. */
|
|
|
527 switch_decision_tree (gswitch *swtch): m_switch (swtch), m_phi_mapping (),
|
|
|
528 m_case_bbs (), m_case_node_pool ("struct case_node pool"),
|
|
|
529 m_case_list (NULL)
|
|
|
530 {
|
|
|
531 }
|
|
|
532
|
|
|
533 /* Analyze switch statement and return true when the statement is expanded
|
|
|
534 as decision tree. */
|
|
|
535 bool analyze_switch_statement ();
|
|
|
536
|
|
|
537 /* Attempt to expand CLUSTERS as a decision tree. Return true when
|
|
|
538 expanded. */
|
|
|
539 bool try_switch_expansion (vec<cluster *> &clusters);
|
|
|
540 /* Compute the number of case labels that correspond to each outgoing edge of
|
|
|
541 switch statement. Record this information in the aux field of the edge.
|
|
|
542 */
|
|
|
543 void compute_cases_per_edge ();
|
|
|
544
|
|
|
545 /* Before switch transformation, record all SSA_NAMEs defined in switch BB
|
|
|
546 and used in a label basic block. */
|
|
|
547 void record_phi_operand_mapping ();
|
|
|
548
|
|
|
549 /* Append new operands to PHI statements that were introduced due to
|
|
|
550 addition of new edges to case labels. */
|
|
|
551 void fix_phi_operands_for_edges ();
|
|
|
552
|
|
|
553 /* Generate a decision tree, switching on INDEX_EXPR and jumping to
|
|
|
554 one of the labels in CASE_LIST or to the DEFAULT_LABEL.
|
|
|
555
|
|
|
556 We generate a binary decision tree to select the appropriate target
|
|
|
557 code. */
|
|
|
558 void emit (basic_block bb, tree index_expr,
|
|
|
559 profile_probability default_prob, tree index_type);
|
|
|
560
|
|
|
561 /* Emit step-by-step code to select a case for the value of INDEX.
|
|
|
562 The thus generated decision tree follows the form of the
|
|
|
563 case-node binary tree NODE, whose nodes represent test conditions.
|
|
|
564 DEFAULT_PROB is probability of cases leading to default BB.
|
|
|
565 INDEX_TYPE is the type of the index of the switch. */
|
|
|
566 basic_block emit_case_nodes (basic_block bb, tree index,
|
|
|
567 case_tree_node *node,
|
|
|
568 profile_probability default_prob,
|
|
|
569 tree index_type);
|
|
|
570
|
|
|
571 /* Take an ordered list of case nodes
|
|
|
572 and transform them into a near optimal binary tree,
|
|
|
573 on the assumption that any target code selection value is as
|
|
|
574 likely as any other.
|
|
|
575
|
|
|
576 The transformation is performed by splitting the ordered
|
|
|
577 list into two equal sections plus a pivot. The parts are
|
|
|
578 then attached to the pivot as left and right branches. Each
|
|
|
579 branch is then transformed recursively. */
|
|
|
580 static void balance_case_nodes (case_tree_node **head,
|
|
|
581 case_tree_node *parent);
|
|
|
582
|
|
|
583 /* Dump ROOT, a list or tree of case nodes, to file F. */
|
|
|
584 static void dump_case_nodes (FILE *f, case_tree_node *root, int indent_step,
|
|
|
585 int indent_level);
|
|
|
586
|
|
|
587 /* Add an unconditional jump to CASE_BB that happens in basic block BB. */
|
|
|
588 static void emit_jump (basic_block bb, basic_block case_bb);
|
|
|
589
|
|
|
590 /* Generate code to compare OP0 with OP1 so that the condition codes are
|
|
|
591 set and to jump to LABEL_BB if the condition is true.
|
|
|
592 COMPARISON is the GIMPLE comparison (EQ, NE, GT, etc.).
|
|
|
593 PROB is the probability of jumping to LABEL_BB. */
|
|
|
594 static basic_block emit_cmp_and_jump_insns (basic_block bb, tree op0,
|
|
|
595 tree op1, tree_code comparison,
|
|
|
596 basic_block label_bb,
|
|
|
597 profile_probability prob);
|
|
|
598
|
|
|
599 /* Generate code to jump to LABEL if OP0 and OP1 are equal in mode MODE.
|
|
|
600 PROB is the probability of jumping to LABEL_BB. */
|
|
|
601 static basic_block do_jump_if_equal (basic_block bb, tree op0, tree op1,
|
|
|
602 basic_block label_bb,
|
|
|
603 profile_probability prob);
|
|
|
604
|
|
|
605 /* Reset the aux field of all outgoing edges of switch basic block. */
|
|
|
606 static inline void reset_out_edges_aux (gswitch *swtch);
|
|
|
607
|
|
|
608 /* Switch statement. */
|
|
|
609 gswitch *m_switch;
|
|
|
610
|
|
|
611 /* Map of PHI nodes that have to be fixed after expansion. */
|
|
|
612 hash_map<tree, tree> m_phi_mapping;
|
|
|
613
|
|
|
614 /* List of basic blocks that belong to labels of the switch. */
|
|
|
615 auto_vec<basic_block> m_case_bbs;
|
|
|
616
|
|
|
617 /* Basic block with default label. */
|
|
|
618 basic_block m_default_bb;
|
|
|
619
|
|
|
620 /* A pool for case nodes. */
|
|
|
621 object_allocator<case_tree_node> m_case_node_pool;
|
|
|
622
|
|
|
623 /* Balanced tree of case nodes. */
|
|
|
624 case_tree_node *m_case_list;
|
|
|
625 };
|
|
|
626
|
|
|
627 /*
|
|
|
628 Switch initialization conversion
|
|
|
629
|
|
|
630 The following pass changes simple initializations of scalars in a switch
|
|
|
631 statement into initializations from a static array. Obviously, the values
|
|
|
632 must be constant and known at compile time and a default branch must be
|
|
|
633 provided. For example, the following code:
|
|
|
634
|
|
|
635 int a,b;
|
|
|
636
|
|
|
637 switch (argc)
|
|
|
638 {
|
|
|
639 case 1:
|
|
|
640 case 2:
|
|
|
641 a_1 = 8;
|
|
|
642 b_1 = 6;
|
|
|
643 break;
|
|
|
644 case 3:
|
|
|
645 a_2 = 9;
|
|
|
646 b_2 = 5;
|
|
|
647 break;
|
|
|
648 case 12:
|
|
|
649 a_3 = 10;
|
|
|
650 b_3 = 4;
|
|
|
651 break;
|
|
|
652 default:
|
|
|
653 a_4 = 16;
|
|
|
654 b_4 = 1;
|
|
|
655 break;
|
|
|
656 }
|
|
|
657 a_5 = PHI <a_1, a_2, a_3, a_4>
|
|
|
658 b_5 = PHI <b_1, b_2, b_3, b_4>
|
|
|
659
|
|
|
660
|
|
|
661 is changed into:
|
|
|
662
|
|
|
663 static const int = CSWTCH01[] = {6, 6, 5, 1, 1, 1, 1, 1, 1, 1, 1, 4};
|
|
|
664 static const int = CSWTCH02[] = {8, 8, 9, 16, 16, 16, 16, 16, 16, 16,
|
|
|
665 16, 16, 10};
|
|
|
666
|
|
|
667 if (((unsigned) argc) - 1 < 11)
|
|
|
668 {
|
|
|
669 a_6 = CSWTCH02[argc - 1];
|
|
|
670 b_6 = CSWTCH01[argc - 1];
|
|
|
671 }
|
|
|
672 else
|
|
|
673 {
|
|
|
674 a_7 = 16;
|
|
|
675 b_7 = 1;
|
|
|
676 }
|
|
|
677 a_5 = PHI <a_6, a_7>
|
|
|
678 b_b = PHI <b_6, b_7>
|
|
|
679
|
|
|
680 There are further constraints. Specifically, the range of values across all
|
|
|
681 case labels must not be bigger than SWITCH_CONVERSION_BRANCH_RATIO (default
|
|
|
682 eight) times the number of the actual switch branches.
|
|
|
683
|
|
|
684 This transformation was contributed by Martin Jambor, see this e-mail:
|
|
|
685 http://gcc.gnu.org/ml/gcc-patches/2008-07/msg00011.html */
|
|
|
686
|
|
|
687 /* The main structure of the pass. */
|
|
|
688 struct switch_conversion
|
|
|
689 {
|
|
|
690 /* Constructor. */
|
|
|
691 switch_conversion ();
|
|
|
692
|
|
|
693 /* Destructor. */
|
|
|
694 ~switch_conversion ();
|
|
|
695
|
|
|
696 /* The following function is invoked on every switch statement (the current
|
|
|
697 one is given in SWTCH) and runs the individual phases of switch
|
|
|
698 conversion on it one after another until one fails or the conversion
|
|
|
699 is completed. On success, NULL is in m_reason, otherwise points
|
|
|
700 to a string with the reason why the conversion failed. */
|
|
|
701 void expand (gswitch *swtch);
|
|
|
702
|
|
|
703 /* Collection information about SWTCH statement. */
|
|
|
704 void collect (gswitch *swtch);
|
|
|
705
|
|
|
706 /* Checks whether the range given by individual case statements of the switch
|
|
|
707 switch statement isn't too big and whether the number of branches actually
|
|
|
708 satisfies the size of the new array. */
|
|
|
709 bool check_range ();
|
|
|
710
|
|
|
711 /* Checks whether all but the final BB basic blocks are empty. */
|
|
|
712 bool check_all_empty_except_final ();
|
|
|
713
|
|
|
714 /* This function checks whether all required values in phi nodes in final_bb
|
|
|
715 are constants. Required values are those that correspond to a basic block
|
|
|
716 which is a part of the examined switch statement. It returns true if the
|
|
|
717 phi nodes are OK, otherwise false. */
|
|
|
718 bool check_final_bb ();
|
|
|
719
|
|
|
720 /* The following function allocates default_values, target_{in,out}_names and
|
|
|
721 constructors arrays. The last one is also populated with pointers to
|
|
|
722 vectors that will become constructors of new arrays. */
|
|
|
723 void create_temp_arrays ();
|
|
|
724
|
|
|
725 /* Populate the array of default values in the order of phi nodes.
|
|
|
726 DEFAULT_CASE is the CASE_LABEL_EXPR for the default switch branch
|
|
|
727 if the range is non-contiguous or the default case has standard
|
|
|
728 structure, otherwise it is the first non-default case instead. */
|
|
|
729 void gather_default_values (tree default_case);
|
|
|
730
|
|
|
731 /* The following function populates the vectors in the constructors array with
|
|
|
732 future contents of the static arrays. The vectors are populated in the
|
|
|
733 order of phi nodes. */
|
|
|
734 void build_constructors ();
|
|
|
735
|
|
|
736 /* If all values in the constructor vector are products of a linear function
|
|
|
737 a * x + b, then return true. When true, COEFF_A and COEFF_B and
|
|
|
738 coefficients of the linear function. Note that equal values are special
|
|
|
739 case of a linear function with a and b equal to zero. */
|
|
|
740 bool contains_linear_function_p (vec<constructor_elt, va_gc> *vec,
|
|
|
741 wide_int *coeff_a, wide_int *coeff_b);
|
|
|
742
|
|
|
743 /* Return type which should be used for array elements, either TYPE's
|
|
|
744 main variant or, for integral types, some smaller integral type
|
|
|
745 that can still hold all the constants. */
|
|
|
746 tree array_value_type (tree type, int num);
|
|
|
747
|
|
|
748 /* Create an appropriate array type and declaration and assemble a static
|
|
|
749 array variable. Also create a load statement that initializes
|
|
|
750 the variable in question with a value from the static array. SWTCH is
|
|
|
751 the switch statement being converted, NUM is the index to
|
|
|
752 arrays of constructors, default values and target SSA names
|
|
|
753 for this particular array. ARR_INDEX_TYPE is the type of the index
|
|
|
754 of the new array, PHI is the phi node of the final BB that corresponds
|
|
|
755 to the value that will be loaded from the created array. TIDX
|
|
|
756 is an ssa name of a temporary variable holding the index for loads from the
|
|
|
757 new array. */
|
|
|
758 void build_one_array (int num, tree arr_index_type,
|
|
|
759 gphi *phi, tree tidx);
|
|
|
760
|
|
|
761 /* Builds and initializes static arrays initialized with values gathered from
|
|
|
762 the switch statement. Also creates statements that load values from
|
|
|
763 them. */
|
|
|
764 void build_arrays ();
|
|
|
765
|
|
|
766 /* Generates and appropriately inserts loads of default values at the position
|
|
|
767 given by GSI. Returns the last inserted statement. */
|
|
|
768 gassign *gen_def_assigns (gimple_stmt_iterator *gsi);
|
|
|
769
|
|
|
770 /* Deletes the unused bbs and edges that now contain the switch statement and
|
|
|
771 its empty branch bbs. BBD is the now dead BB containing
|
|
|
772 the original switch statement, FINAL is the last BB of the converted
|
|
|
773 switch statement (in terms of succession). */
|
|
|
774 void prune_bbs (basic_block bbd, basic_block final, basic_block default_bb);
|
|
|
775
|
|
|
776 /* Add values to phi nodes in final_bb for the two new edges. E1F is the edge
|
|
|
777 from the basic block loading values from an array and E2F from the basic
|
|
|
778 block loading default values. BBF is the last switch basic block (see the
|
|
|
779 bbf description in the comment below). */
|
|
|
780 void fix_phi_nodes (edge e1f, edge e2f, basic_block bbf);
|
|
|
781
|
|
|
782 /* Creates a check whether the switch expression value actually falls into the
|
|
|
783 range given by all the cases. If it does not, the temporaries are loaded
|
|
|
784 with default values instead. */
|
|
|
785 void gen_inbound_check ();
|
|
|
786
|
|
|
787 /* Switch statement for which switch conversion takes place. */
|
|
|
788 gswitch *m_switch;
|
|
|
789
|
|
|
790 /* The expression used to decide the switch branch. */
|
|
|
791 tree m_index_expr;
|
|
|
792
|
|
|
793 /* The following integer constants store the minimum and maximum value
|
|
|
794 covered by the case labels. */
|
|
|
795 tree m_range_min;
|
|
|
796 tree m_range_max;
|
|
|
797
|
|
|
798 /* The difference between the above two numbers. Stored here because it
|
|
|
799 is used in all the conversion heuristics, as well as for some of the
|
|
|
800 transformation, and it is expensive to re-compute it all the time. */
|
|
|
801 tree m_range_size;
|
|
|
802
|
|
|
803 /* Basic block that contains the actual GIMPLE_SWITCH. */
|
|
|
804 basic_block m_switch_bb;
|
|
|
805
|
|
|
806 /* Basic block that is the target of the default case. */
|
|
|
807 basic_block m_default_bb;
|
|
|
808
|
|
|
809 /* The single successor block of all branches out of the GIMPLE_SWITCH,
|
|
|
810 if such a block exists. Otherwise NULL. */
|
|
|
811 basic_block m_final_bb;
|
|
|
812
|
|
|
813 /* The probability of the default edge in the replaced switch. */
|
|
|
814 profile_probability m_default_prob;
|
|
|
815
|
|
|
816 /* The count of the default edge in the replaced switch. */
|
|
|
817 profile_count m_default_count;
|
|
|
818
|
|
|
819 /* Combined count of all other (non-default) edges in the replaced switch. */
|
|
|
820 profile_count m_other_count;
|
|
|
821
|
|
|
822 /* Number of phi nodes in the final bb (that we'll be replacing). */
|
|
|
823 int m_phi_count;
|
|
|
824
|
|
|
825 /* Constructors of new static arrays. */
|
|
|
826 vec<constructor_elt, va_gc> **m_constructors;
|
|
|
827
|
|
|
828 /* Array of default values, in the same order as phi nodes. */
|
|
|
829 tree *m_default_values;
|
|
|
830
|
|
|
831 /* Array of ssa names that are initialized with a value from a new static
|
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832 array. */
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833 tree *m_target_inbound_names;
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834
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835 /* Array of ssa names that are initialized with the default value if the
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836 switch expression is out of range. */
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837 tree *m_target_outbound_names;
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838
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839 /* VOP SSA_NAME. */
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840 tree m_target_vop;
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841
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842 /* The first load statement that loads a temporary from a new static array.
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843 */
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844 gimple *m_arr_ref_first;
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845
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846 /* The last load statement that loads a temporary from a new static array. */
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847 gimple *m_arr_ref_last;
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848
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849 /* String reason why the case wasn't a good candidate that is written to the
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850 dump file, if there is one. */
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851 const char *m_reason;
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852
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853 /* True if default case is not used for any value between range_min and
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854 range_max inclusive. */
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855 bool m_contiguous_range;
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856
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857 /* True if default case does not have the required shape for other case
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858 labels. */
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859 bool m_default_case_nonstandard;
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860
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861 /* Number of uniq labels for non-default edges. */
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862 unsigned int m_uniq;
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863
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864 /* Count is number of non-default edges. */
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865 unsigned int m_count;
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866
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867 /* True if CFG has been changed. */
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868 bool m_cfg_altered;
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869 };
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870
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871 void
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872 switch_decision_tree::reset_out_edges_aux (gswitch *swtch)
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873 {
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874 basic_block bb = gimple_bb (swtch);
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875 edge e;
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876 edge_iterator ei;
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877 FOR_EACH_EDGE (e, ei, bb->succs)
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878 e->aux = (void *) 0;
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879 }
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880
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881 } // tree_switch_conversion namespace
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882
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883 #endif // TREE_SWITCH_CONVERSION_H
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