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1 .. Copyright (C) 2014-2018 Free Software Foundation, Inc.
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2 Originally contributed by David Malcolm <dmalcolm@redhat.com>
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3
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4 This is free software: you can redistribute it and/or modify it
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5 under the terms of the GNU General Public License as published by
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6 the Free Software Foundation, either version 3 of the License, or
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7 (at your option) any later version.
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8
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9 This program is distributed in the hope that it will be useful, but
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10 WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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12 General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public License
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15 along with this program. If not, see
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16 <http://www.gnu.org/licenses/>.
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17
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18 .. default-domain:: cpp
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19
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20 Creating and using functions
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21 ============================
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22
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23 Params
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24 ------
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25 .. class:: gccjit::param
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26
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27 A `gccjit::param` represents a parameter to a function.
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28
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29 .. function:: gccjit::param \
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30 gccjit::context::new_param (gccjit::type type,\
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31 const char *name, \
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32 gccjit::location loc)
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33
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34 In preparation for creating a function, create a new parameter of the
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35 given type and name.
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36
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37 :class:`gccjit::param` is a subclass of :class:`gccjit::lvalue` (and thus
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38 of :class:`gccjit::rvalue` and :class:`gccjit::object`). It is a thin
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39 wrapper around the C API's :c:type:`gcc_jit_param *`.
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40
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41 Functions
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42 ---------
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43
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44 .. class:: gccjit::function
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45
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46 A `gccjit::function` represents a function - either one that we're
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47 creating ourselves, or one that we're referencing.
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48
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49 .. function:: gccjit::function \
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50 gccjit::context::new_function (enum gcc_jit_function_kind,\
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51 gccjit::type return_type, \
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52 const char *name, \
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53 std::vector<param> ¶ms, \
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54 int is_variadic, \
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55 gccjit::location loc)
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56
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57 Create a gcc_jit_function with the given name and parameters.
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58
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59 Parameters "is_variadic" and "loc" are optional.
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60
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61 This is a wrapper around the C API's :c:func:`gcc_jit_context_new_function`.
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62
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63 .. function:: gccjit::function \
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64 gccjit::context::get_builtin_function (const char *name)
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65
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66 This is a wrapper around the C API's
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67 :c:func:`gcc_jit_context_get_builtin_function`.
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68
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69 .. function:: gccjit::param \
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70 gccjit::function::get_param (int index) const
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71
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72 Get the param of the given index (0-based).
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73
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74 .. function:: void \
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75 gccjit::function::dump_to_dot (const char *path)
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76
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77 Emit the function in graphviz format to the given path.
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78
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79 .. function:: gccjit::lvalue \
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80 gccjit::function::new_local (gccjit::type type,\
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81 const char *name, \
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82 gccjit::location loc)
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83
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84 Create a new local variable within the function, of the given type and
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85 name.
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86
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87 Blocks
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88 ------
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89 .. class:: gccjit::block
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90
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91 A `gccjit::block` represents a basic block within a function i.e. a
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92 sequence of statements with a single entry point and a single exit
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93 point.
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94
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95 :class:`gccjit::block` is a subclass of :class:`gccjit::object`.
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96
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97 The first basic block that you create within a function will
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98 be the entrypoint.
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99
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100 Each basic block that you create within a function must be
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101 terminated, either with a conditional, a jump, a return, or
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102 a switch.
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103
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104 It's legal to have multiple basic blocks that return within
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105 one function.
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106
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107 .. function:: gccjit::block \
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108 gccjit::function::new_block (const char *name)
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109
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110 Create a basic block of the given name. The name may be NULL, but
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111 providing meaningful names is often helpful when debugging: it may
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112 show up in dumps of the internal representation, and in error
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113 messages.
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114
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115 Statements
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116 ----------
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117
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118 .. function:: void\
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119 gccjit::block::add_eval (gccjit::rvalue rvalue, \
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120 gccjit::location loc)
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121
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122 Add evaluation of an rvalue, discarding the result
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123 (e.g. a function call that "returns" void).
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124
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125 This is equivalent to this C code:
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126
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127 .. code-block:: c
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128
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129 (void)expression;
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130
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131 .. function:: void\
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132 gccjit::block::add_assignment (gccjit::lvalue lvalue, \
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133 gccjit::rvalue rvalue, \
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134 gccjit::location loc)
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135
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136 Add evaluation of an rvalue, assigning the result to the given
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137 lvalue.
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138
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139 This is roughly equivalent to this C code:
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140
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141 .. code-block:: c
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142
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143 lvalue = rvalue;
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144
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145 .. function:: void\
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146 gccjit::block::add_assignment_op (gccjit::lvalue lvalue, \
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147 enum gcc_jit_binary_op, \
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148 gccjit::rvalue rvalue, \
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149 gccjit::location loc)
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150
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151 Add evaluation of an rvalue, using the result to modify an
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152 lvalue.
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153
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154 This is analogous to "+=" and friends:
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155
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156 .. code-block:: c
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157
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158 lvalue += rvalue;
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159 lvalue *= rvalue;
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160 lvalue /= rvalue;
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161
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162 etc. For example:
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163
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164 .. code-block:: c
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165
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166 /* "i++" */
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167 loop_body.add_assignment_op (
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168 i,
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169 GCC_JIT_BINARY_OP_PLUS,
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170 ctxt.one (int_type));
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171
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172 .. function:: void\
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173 gccjit::block::add_comment (const char *text, \
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174 gccjit::location loc)
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175
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176 Add a no-op textual comment to the internal representation of the
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177 code. It will be optimized away, but will be visible in the dumps
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178 seen via :c:macro:`GCC_JIT_BOOL_OPTION_DUMP_INITIAL_TREE`
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179 and :c:macro:`GCC_JIT_BOOL_OPTION_DUMP_INITIAL_GIMPLE`,
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180 and thus may be of use when debugging how your project's internal
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181 representation gets converted to the libgccjit IR.
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182
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183 Parameter "loc" is optional.
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184
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185 .. function:: void\
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186 gccjit::block::end_with_conditional (gccjit::rvalue boolval,\
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187 gccjit::block on_true,\
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188 gccjit::block on_false, \
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189 gccjit::location loc)
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190
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191 Terminate a block by adding evaluation of an rvalue, branching on the
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192 result to the appropriate successor block.
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193
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194 This is roughly equivalent to this C code:
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195
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196 .. code-block:: c
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197
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198 if (boolval)
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199 goto on_true;
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200 else
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201 goto on_false;
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202
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203 block, boolval, on_true, and on_false must be non-NULL.
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204
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205 .. function:: void\
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206 gccjit::block::end_with_jump (gccjit::block target, \
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207 gccjit::location loc)
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208
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209 Terminate a block by adding a jump to the given target block.
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210
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211 This is roughly equivalent to this C code:
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212
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213 .. code-block:: c
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214
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215 goto target;
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216
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217 .. function:: void\
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218 gccjit::block::end_with_return (gccjit::rvalue rvalue, \
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219 gccjit::location loc)
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220
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221 Terminate a block.
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222
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223 Both params are optional.
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224
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225 An rvalue must be provided for a function returning non-void, and
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226 must not be provided by a function "returning" `void`.
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227
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228 If an rvalue is provided, the block is terminated by evaluating the
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229 rvalue and returning the value.
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230
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231 This is roughly equivalent to this C code:
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232
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233 .. code-block:: c
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234
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235 return expression;
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236
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237 If an rvalue is not provided, the block is terminated by adding a
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238 valueless return, for use within a function with "void" return type.
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239
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240 This is equivalent to this C code:
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241
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242 .. code-block:: c
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243
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244 return;
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245
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246 .. function:: void\
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247 gccjit::block::end_with_switch (gccjit::rvalue expr,\
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248 gccjit::block default_block,\
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249 std::vector <gccjit::case_> cases,\
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250 gccjit::location loc)
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251
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252 Terminate a block by adding evalation of an rvalue, then performing
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253 a multiway branch.
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254
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255 This is roughly equivalent to this C code:
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256
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257 .. code-block:: c
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258
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259 switch (expr)
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260 {
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261 default:
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262 goto default_block;
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263
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264 case C0.min_value ... C0.max_value:
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265 goto C0.dest_block;
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266
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267 case C1.min_value ... C1.max_value:
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268 goto C1.dest_block;
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269
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270 ...etc...
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271
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272 case C[N - 1].min_value ... C[N - 1].max_value:
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273 goto C[N - 1].dest_block;
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274 }
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275
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276 ``expr`` must be of the same integer type as all of the ``min_value``
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277 and ``max_value`` within the cases.
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278
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279 The ranges of the cases must not overlap (or have duplicate
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280 values).
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281
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282 The API entrypoints relating to switch statements and cases:
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283
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284 * :func:`gccjit::block::end_with_switch`
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285
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286 * :func:`gccjit::context::new_case`
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287
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288 were added in :ref:`LIBGCCJIT_ABI_3`; you can test for their presence
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289 using
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290
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291 .. code-block:: c
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292
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293 #ifdef LIBGCCJIT_HAVE_SWITCH_STATEMENTS
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294
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295 .. class:: gccjit::case_
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296
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297 A `gccjit::case_` represents a case within a switch statement, and
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298 is created within a particular :class:`gccjit::context` using
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299 :func:`gccjit::context::new_case`. It is a subclass of
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300 :class:`gccjit::object`.
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301
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302 Each case expresses a multivalued range of integer values. You
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303 can express single-valued cases by passing in the same value for
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304 both `min_value` and `max_value`.
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305
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306 .. function:: gccjit::case_ *\
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307 gccjit::context::new_case (gccjit::rvalue min_value,\
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308 gccjit::rvalue max_value,\
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309 gccjit::block dest_block)
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310
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311 Create a new gccjit::case for use in a switch statement.
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312 `min_value` and `max_value` must be constants of an integer type,
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313 which must match that of the expression of the switch statement.
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314
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315 `dest_block` must be within the same function as the switch
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316 statement.
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317
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318 Here's an example of creating a switch statement:
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319
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320 .. literalinclude:: ../../../../testsuite/jit.dg/test-switch.cc
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321 :start-after: /* Quote from here in docs/cp/topics/functions.rst. */
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322 :end-before: /* Quote up to here in docs/cp/topics/functions.rst. */
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323 :language: c++
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