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1 .. Copyright (C) 2014-2020 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:: c
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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 .. type:: gcc_jit_param
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26
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27 A `gcc_jit_param` represents a parameter to a function.
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28
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29 .. function:: gcc_jit_param *\
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30 gcc_jit_context_new_param (gcc_jit_context *ctxt,\
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31 gcc_jit_location *loc,\
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32 gcc_jit_type *type,\
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33 const char *name)
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34
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35 In preparation for creating a function, create a new parameter of the
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36 given type and name.
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37
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38 The parameter ``name`` must be non-NULL. The call takes a copy of the
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39 underlying string, so it is valid to pass in a pointer to an on-stack
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40 buffer.
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41
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42 Parameters are lvalues, and thus are also rvalues (and objects), so the
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43 following upcasts are available:
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44
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45 .. function:: gcc_jit_lvalue *\
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46 gcc_jit_param_as_lvalue (gcc_jit_param *param)
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47
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48 Upcasting from param to lvalue.
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49
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50 .. function:: gcc_jit_rvalue *\
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51 gcc_jit_param_as_rvalue (gcc_jit_param *param)
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52
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53 Upcasting from param to rvalue.
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54
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55 .. function:: gcc_jit_object *\
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56 gcc_jit_param_as_object (gcc_jit_param *param)
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57
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58 Upcasting from param to object.
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59
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60
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61 Functions
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62 ---------
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63
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64 .. type:: gcc_jit_function
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65
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66 A `gcc_jit_function` represents a function - either one that we're
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67 creating ourselves, or one that we're referencing.
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68
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69 .. function:: gcc_jit_function *\
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70 gcc_jit_context_new_function (gcc_jit_context *ctxt,\
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71 gcc_jit_location *loc,\
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72 enum gcc_jit_function_kind kind,\
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73 gcc_jit_type *return_type,\
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74 const char *name,\
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75 int num_params,\
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76 gcc_jit_param **params,\
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77 int is_variadic)
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78
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79 Create a gcc_jit_function with the given name and parameters.
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80
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81 .. type:: enum gcc_jit_function_kind
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82
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83 This enum controls the kind of function created, and has the following
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84 values:
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85
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86 .. macro:: GCC_JIT_FUNCTION_EXPORTED
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87
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88 Function is defined by the client code and visible
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89 by name outside of the JIT.
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90
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91 This value is required if you want to extract machine code
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92 for this function from a :type:`gcc_jit_result` via
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93 :func:`gcc_jit_result_get_code`.
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94
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95 .. macro:: GCC_JIT_FUNCTION_INTERNAL
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96
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97 Function is defined by the client code, but is invisible
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98 outside of the JIT. Analogous to a "static" function.
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99
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100 .. macro:: GCC_JIT_FUNCTION_IMPORTED
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101
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102 Function is not defined by the client code; we're merely
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103 referring to it. Analogous to using an "extern" function from a
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104 header file.
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105
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106 .. macro:: GCC_JIT_FUNCTION_ALWAYS_INLINE
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107
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108 Function is only ever inlined into other functions, and is
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109 invisible outside of the JIT.
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110
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111 Analogous to prefixing with ``inline`` and adding
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112 ``__attribute__((always_inline))``
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113
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114 Inlining will only occur when the optimization level is
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115 above 0; when optimization is off, this is essentially the
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116 same as GCC_JIT_FUNCTION_INTERNAL.
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117
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118 The parameter ``name`` must be non-NULL. The call takes a copy of the
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119 underlying string, so it is valid to pass in a pointer to an on-stack
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120 buffer.
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121
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122 .. function:: gcc_jit_function *\
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123 gcc_jit_context_get_builtin_function (gcc_jit_context *ctxt,\
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124 const char *name)
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125
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126 .. function:: gcc_jit_object *\
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127 gcc_jit_function_as_object (gcc_jit_function *func)
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128
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129 Upcasting from function to object.
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130
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131 .. function:: gcc_jit_param *\
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132 gcc_jit_function_get_param (gcc_jit_function *func, int index)
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133
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134 Get the param of the given index (0-based).
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135
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136 .. function:: void \
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137 gcc_jit_function_dump_to_dot (gcc_jit_function *func,\
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138 const char *path)
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139
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140 Emit the function in graphviz format to the given path.
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141
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142 .. function:: gcc_jit_lvalue *\
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143 gcc_jit_function_new_local (gcc_jit_function *func,\
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144 gcc_jit_location *loc,\
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145 gcc_jit_type *type,\
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146 const char *name)
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147
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148 Create a new local variable within the function, of the given type and
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149 name.
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150
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151 The parameter ``name`` must be non-NULL. The call takes a copy of the
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152 underlying string, so it is valid to pass in a pointer to an on-stack
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153 buffer.
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154
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155 Blocks
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156 ------
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157 .. type:: gcc_jit_block
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158
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159 A `gcc_jit_block` represents a basic block within a function i.e. a
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160 sequence of statements with a single entry point and a single exit
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161 point.
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162
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163 The first basic block that you create within a function will
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164 be the entrypoint.
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165
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166 Each basic block that you create within a function must be
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167 terminated, either with a conditional, a jump, a return, or a
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168 switch.
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169
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170 It's legal to have multiple basic blocks that return within
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171 one function.
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172
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173 .. function:: gcc_jit_block *\
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174 gcc_jit_function_new_block (gcc_jit_function *func,\
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175 const char *name)
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176
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177 Create a basic block of the given name. The name may be NULL, but
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178 providing meaningful names is often helpful when debugging: it may
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179 show up in dumps of the internal representation, and in error
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180 messages. It is copied, so the input buffer does not need to outlive
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181 the call; you can pass in a pointer to an on-stack buffer, e.g.:
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182
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183 .. code-block:: c
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184
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185 for (pc = 0; pc < fn->fn_num_ops; pc++)
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186 {
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187 char buf[16];
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188 sprintf (buf, "instr%i", pc);
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189 state.op_blocks[pc] = gcc_jit_function_new_block (state.fn, buf);
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190 }
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191
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192 .. function:: gcc_jit_object *\
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193 gcc_jit_block_as_object (gcc_jit_block *block)
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194
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195 Upcast from block to object.
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196
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197 .. function:: gcc_jit_function *\
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198 gcc_jit_block_get_function (gcc_jit_block *block)
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199
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200 Which function is this block within?
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201
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202
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203 Statements
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204 ----------
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205
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206 .. function:: void\
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207 gcc_jit_block_add_eval (gcc_jit_block *block,\
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208 gcc_jit_location *loc,\
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209 gcc_jit_rvalue *rvalue)
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210
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211 Add evaluation of an rvalue, discarding the result
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212 (e.g. a function call that "returns" void).
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213
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214 This is equivalent to this C code:
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215
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216 .. code-block:: c
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217
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218 (void)expression;
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219
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220 .. function:: void\
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221 gcc_jit_block_add_assignment (gcc_jit_block *block,\
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222 gcc_jit_location *loc,\
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223 gcc_jit_lvalue *lvalue,\
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224 gcc_jit_rvalue *rvalue)
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225
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226 Add evaluation of an rvalue, assigning the result to the given
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227 lvalue.
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228
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229 This is roughly equivalent to this C code:
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230
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231 .. code-block:: c
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232
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233 lvalue = rvalue;
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234
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235 .. function:: void\
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236 gcc_jit_block_add_assignment_op (gcc_jit_block *block,\
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237 gcc_jit_location *loc,\
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238 gcc_jit_lvalue *lvalue,\
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239 enum gcc_jit_binary_op op,\
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240 gcc_jit_rvalue *rvalue)
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241
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242 Add evaluation of an rvalue, using the result to modify an
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243 lvalue.
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244
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245 This is analogous to "+=" and friends:
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246
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247 .. code-block:: c
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248
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249 lvalue += rvalue;
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250 lvalue *= rvalue;
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251 lvalue /= rvalue;
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252
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253 etc. For example:
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254
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255 .. code-block:: c
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256
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257 /* "i++" */
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258 gcc_jit_block_add_assignment_op (
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259 loop_body, NULL,
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260 i,
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261 GCC_JIT_BINARY_OP_PLUS,
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262 gcc_jit_context_one (ctxt, int_type));
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263
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264 .. function:: void\
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265 gcc_jit_block_add_comment (gcc_jit_block *block,\
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266 gcc_jit_location *loc,\
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267 const char *text)
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268
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269 Add a no-op textual comment to the internal representation of the
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270 code. It will be optimized away, but will be visible in the dumps
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271 seen via :macro:`GCC_JIT_BOOL_OPTION_DUMP_INITIAL_TREE`
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272 and :macro:`GCC_JIT_BOOL_OPTION_DUMP_INITIAL_GIMPLE`,
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273 and thus may be of use when debugging how your project's internal
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274 representation gets converted to the libgccjit IR.
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275
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276 The parameter ``text`` must be non-NULL. It is copied, so the input
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277 buffer does not need to outlive the call. For example:
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278
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279 .. code-block:: c
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280
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281 char buf[100];
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282 snprintf (buf, sizeof (buf),
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283 "op%i: %s",
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284 pc, opcode_names[op->op_opcode]);
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285 gcc_jit_block_add_comment (block, loc, buf);
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286
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287 .. function:: void\
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288 gcc_jit_block_end_with_conditional (gcc_jit_block *block,\
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289 gcc_jit_location *loc,\
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290 gcc_jit_rvalue *boolval,\
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291 gcc_jit_block *on_true,\
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292 gcc_jit_block *on_false)
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293
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294 Terminate a block by adding evaluation of an rvalue, branching on the
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295 result to the appropriate successor block.
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296
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297 This is roughly equivalent to this C code:
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298
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299 .. code-block:: c
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300
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301 if (boolval)
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302 goto on_true;
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303 else
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304 goto on_false;
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305
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306 block, boolval, on_true, and on_false must be non-NULL.
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307
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308 .. function:: void\
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309 gcc_jit_block_end_with_jump (gcc_jit_block *block,\
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310 gcc_jit_location *loc,\
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311 gcc_jit_block *target)
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312
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313
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314 Terminate a block by adding a jump to the given target block.
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315
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316 This is roughly equivalent to this C code:
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317
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318 .. code-block:: c
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319
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320 goto target;
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321
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322 .. function:: void\
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323 gcc_jit_block_end_with_return (gcc_jit_block *block,\
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324 gcc_jit_location *loc,\
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325 gcc_jit_rvalue *rvalue)
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326
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327
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328 Terminate a block by adding evaluation of an rvalue, returning the value.
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329
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330 This is roughly equivalent to this C code:
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331
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332 .. code-block:: c
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333
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334 return expression;
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335
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336 .. function:: void\
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337 gcc_jit_block_end_with_void_return (gcc_jit_block *block,\
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338 gcc_jit_location *loc)
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339
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340
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341 Terminate a block by adding a valueless return, for use within a function
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342 with "void" return type.
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343
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344 This is equivalent to this C code:
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345
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346 .. code-block:: c
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347
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348 return;
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349
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350 .. function:: void\
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351 gcc_jit_block_end_with_switch (gcc_jit_block *block,\
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352 gcc_jit_location *loc,\
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353 gcc_jit_rvalue *expr,\
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354 gcc_jit_block *default_block,\
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355 int num_cases,\
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356 gcc_jit_case **cases)
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357
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358 Terminate a block by adding evalation of an rvalue, then performing
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359 a multiway branch.
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360
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361 This is roughly equivalent to this C code:
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362
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363 .. code-block:: c
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364
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365 switch (expr)
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366 {
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367 default:
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368 goto default_block;
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369
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370 case C0.min_value ... C0.max_value:
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371 goto C0.dest_block;
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372
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373 case C1.min_value ... C1.max_value:
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374 goto C1.dest_block;
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375
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376 ...etc...
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377
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378 case C[N - 1].min_value ... C[N - 1].max_value:
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379 goto C[N - 1].dest_block;
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380 }
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381
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382 ``block``, ``expr``, ``default_block`` and ``cases`` must all be
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383 non-NULL.
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384
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385 ``expr`` must be of the same integer type as all of the ``min_value``
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386 and ``max_value`` within the cases.
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387
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388 ``num_cases`` must be >= 0.
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389
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390 The ranges of the cases must not overlap (or have duplicate
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391 values).
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392
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393 The API entrypoints relating to switch statements and cases:
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394
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395 * :c:func:`gcc_jit_block_end_with_switch`
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396
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397 * :c:func:`gcc_jit_case_as_object`
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398
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399 * :c:func:`gcc_jit_context_new_case`
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400
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401 were added in :ref:`LIBGCCJIT_ABI_3`; you can test for their presence
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402 using
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403
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404 .. code-block:: c
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405
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406 #ifdef LIBGCCJIT_HAVE_SWITCH_STATEMENTS
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407
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408 .. type:: gcc_jit_case
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409
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410 A `gcc_jit_case` represents a case within a switch statement, and
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411 is created within a particular :c:type:`gcc_jit_context` using
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412 :c:func:`gcc_jit_context_new_case`.
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413
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414 Each case expresses a multivalued range of integer values. You
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415 can express single-valued cases by passing in the same value for
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416 both `min_value` and `max_value`.
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417
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418 .. function:: gcc_jit_case *\
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419 gcc_jit_context_new_case (gcc_jit_context *ctxt,\
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420 gcc_jit_rvalue *min_value,\
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421 gcc_jit_rvalue *max_value,\
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422 gcc_jit_block *dest_block)
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423
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424 Create a new gcc_jit_case instance for use in a switch statement.
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425 `min_value` and `max_value` must be constants of an integer type,
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426 which must match that of the expression of the switch statement.
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427
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428 `dest_block` must be within the same function as the switch
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429 statement.
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430
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431 .. function:: gcc_jit_object *\
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432 gcc_jit_case_as_object (gcc_jit_case *case_)
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433
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434 Upcast from a case to an object.
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435
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436 Here's an example of creating a switch statement:
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437
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438 .. literalinclude:: ../../../testsuite/jit.dg/test-switch.c
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439 :start-after: /* Quote from here in docs/topics/functions.rst. */
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440 :end-before: /* Quote up to here in docs/topics/functions.rst. */
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441 :language: c
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