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1 @c Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008
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2 @c Free Software Foundation, Inc.
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3 @c This is part of the GCC manual.
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4 @c For copying conditions, see the file gcc.texi.
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5
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6 @node Options
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7 @chapter Option specification files
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8 @cindex option specification files
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9 @cindex @samp{optc-gen.awk}
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10
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11 Most GCC command-line options are described by special option
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12 definition files, the names of which conventionally end in
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13 @code{.opt}. This chapter describes the format of these files.
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14
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15 @menu
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16 * Option file format:: The general layout of the files
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17 * Option properties:: Supported option properties
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18 @end menu
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19
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20 @node Option file format
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21 @section Option file format
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22
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23 Option files are a simple list of records in which each field occupies
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24 its own line and in which the records themselves are separated by
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25 blank lines. Comments may appear on their own line anywhere within
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26 the file and are preceded by semicolons. Whitespace is allowed before
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27 the semicolon.
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28
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29 The files can contain the following types of record:
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30
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31 @itemize @bullet
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32 @item
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33 A language definition record. These records have two fields: the
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34 string @samp{Language} and the name of the language. Once a language
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35 has been declared in this way, it can be used as an option property.
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36 @xref{Option properties}.
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37
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38 @item
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39 A target specific save record to save additional information. These
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40 records have two fields: the string @samp{TargetSave}, and a
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41 declaration type to go in the @code{cl_target_option} structure.
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42
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43 @item
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44 An option definition record. These records have the following fields:
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45 @enumerate
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46 @item
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47 the name of the option, with the leading ``-'' removed
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48 @item
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49 a space-separated list of option properties (@pxref{Option properties})
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50 @item
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51 the help text to use for @option{--help} (omitted if the second field
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52 contains the @code{Undocumented} property).
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53 @end enumerate
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54
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55 By default, all options beginning with ``f'', ``W'' or ``m'' are
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56 implicitly assumed to take a ``no-'' form. This form should not be
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57 listed separately. If an option beginning with one of these letters
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58 does not have a ``no-'' form, you can use the @code{RejectNegative}
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59 property to reject it.
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60
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61 The help text is automatically line-wrapped before being displayed.
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62 Normally the name of the option is printed on the left-hand side of
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63 the output and the help text is printed on the right. However, if the
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64 help text contains a tab character, the text to the left of the tab is
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65 used instead of the option's name and the text to the right of the
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66 tab forms the help text. This allows you to elaborate on what type
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67 of argument the option takes.
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68
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69 @item
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70 A target mask record. These records have one field of the form
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71 @samp{Mask(@var{x})}. The options-processing script will automatically
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72 allocate a bit in @code{target_flags} (@pxref{Run-time Target}) for
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73 each mask name @var{x} and set the macro @code{MASK_@var{x}} to the
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74 appropriate bitmask. It will also declare a @code{TARGET_@var{x}}
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75 macro that has the value 1 when bit @code{MASK_@var{x}} is set and
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76 0 otherwise.
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77
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78 They are primarily intended to declare target masks that are not
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79 associated with user options, either because these masks represent
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80 internal switches or because the options are not available on all
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81 configurations and yet the masks always need to be defined.
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82 @end itemize
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83
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84 @node Option properties
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85 @section Option properties
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86
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87 The second field of an option record can specify the following properties:
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88
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89 @table @code
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90 @item Common
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91 The option is available for all languages and targets.
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92
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93 @item Target
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94 The option is available for all languages but is target-specific.
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95
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96 @item @var{language}
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97 The option is available when compiling for the given language.
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98
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99 It is possible to specify several different languages for the same
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100 option. Each @var{language} must have been declared by an earlier
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101 @code{Language} record. @xref{Option file format}.
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102
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103 @item RejectNegative
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104 The option does not have a ``no-'' form. All options beginning with
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105 ``f'', ``W'' or ``m'' are assumed to have a ``no-'' form unless this
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106 property is used.
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107
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108 @item Negative(@var{othername})
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109 The option will turn off another option @var{othername}, which is the
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110 the option name with the leading ``-'' removed. This chain action will
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111 propagate through the @code{Negative} property of the option to be
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112 turned off.
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113
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114 @item Joined
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115 @itemx Separate
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116 The option takes a mandatory argument. @code{Joined} indicates
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117 that the option and argument can be included in the same @code{argv}
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118 entry (as with @code{-mflush-func=@var{name}}, for example).
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119 @code{Separate} indicates that the option and argument can be
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120 separate @code{argv} entries (as with @code{-o}). An option is
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121 allowed to have both of these properties.
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122
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123 @item JoinedOrMissing
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124 The option takes an optional argument. If the argument is given,
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125 it will be part of the same @code{argv} entry as the option itself.
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126
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127 This property cannot be used alongside @code{Joined} or @code{Separate}.
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128
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129 @item UInteger
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130 The option's argument is a non-negative integer. The option parser
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131 will check and convert the argument before passing it to the relevant
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132 option handler. @code{UInteger} should also be used on options like
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133 @code{-falign-loops} where both @code{-falign-loops} and
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134 @code{-falign-loops}=@var{n} are supported to make sure the saved
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135 options are given a full integer.
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136
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137 @item Var(@var{var})
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138 The state of this option should be stored in variable @var{var}.
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139 The way that the state is stored depends on the type of option:
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140
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141 @itemize @bullet
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142 @item
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143 If the option uses the @code{Mask} or @code{InverseMask} properties,
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144 @var{var} is the integer variable that contains the mask.
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145
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146 @item
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147 If the option is a normal on/off switch, @var{var} is an integer
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148 variable that is nonzero when the option is enabled. The options
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149 parser will set the variable to 1 when the positive form of the
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150 option is used and 0 when the ``no-'' form is used.
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151
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152 @item
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153 If the option takes an argument and has the @code{UInteger} property,
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154 @var{var} is an integer variable that stores the value of the argument.
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155
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156 @item
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157 Otherwise, if the option takes an argument, @var{var} is a pointer to
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158 the argument string. The pointer will be null if the argument is optional
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159 and wasn't given.
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160 @end itemize
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161
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162 The option-processing script will usually declare @var{var} in
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163 @file{options.c} and leave it to be zero-initialized at start-up time.
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164 You can modify this behavior using @code{VarExists} and @code{Init}.
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165
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166 @item Var(@var{var}, @var{set})
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167 The option controls an integer variable @var{var} and is active when
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168 @var{var} equals @var{set}. The option parser will set @var{var} to
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169 @var{set} when the positive form of the option is used and @code{!@var{set}}
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170 when the ``no-'' form is used.
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171
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172 @var{var} is declared in the same way as for the single-argument form
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173 described above.
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174
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175 @item VarExists
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176 The variable specified by the @code{Var} property already exists.
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177 No definition should be added to @file{options.c} in response to
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178 this option record.
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179
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180 You should use this property only if the variable is declared outside
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181 @file{options.c}.
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182
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183 @item Init(@var{value})
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184 The variable specified by the @code{Var} property should be statically
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185 initialized to @var{value}.
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186
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187 @item Mask(@var{name})
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188 The option is associated with a bit in the @code{target_flags}
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189 variable (@pxref{Run-time Target}) and is active when that bit is set.
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190 You may also specify @code{Var} to select a variable other than
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191 @code{target_flags}.
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192
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193 The options-processing script will automatically allocate a unique bit
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194 for the option. If the option is attached to @samp{target_flags},
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195 the script will set the macro @code{MASK_@var{name}} to the appropriate
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196 bitmask. It will also declare a @code{TARGET_@var{name}} macro that has
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197 the value 1 when the option is active and 0 otherwise. If you use @code{Var}
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198 to attach the option to a different variable, the associated macros are
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199 called @code{OPTION_MASK_@var{name}} and @code{OPTION_@var{name}} respectively.
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200
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201 You can disable automatic bit allocation using @code{MaskExists}.
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202
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203 @item InverseMask(@var{othername})
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204 @itemx InverseMask(@var{othername}, @var{thisname})
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205 The option is the inverse of another option that has the
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206 @code{Mask(@var{othername})} property. If @var{thisname} is given,
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207 the options-processing script will declare a @code{TARGET_@var{thisname}}
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208 macro that is 1 when the option is active and 0 otherwise.
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209
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210 @item MaskExists
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211 The mask specified by the @code{Mask} property already exists.
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212 No @code{MASK} or @code{TARGET} definitions should be added to
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213 @file{options.h} in response to this option record.
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214
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215 The main purpose of this property is to support synonymous options.
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216 The first option should use @samp{Mask(@var{name})} and the others
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217 should use @samp{Mask(@var{name}) MaskExists}.
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218
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219 @item Report
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220 The state of the option should be printed by @option{-fverbose-asm}.
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221
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222 @item Undocumented
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223 The option is deliberately missing documentation and should not
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224 be included in the @option{--help} output.
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225
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226 @item Condition(@var{cond})
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227 The option should only be accepted if preprocessor condition
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228 @var{cond} is true. Note that any C declarations associated with the
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229 option will be present even if @var{cond} is false; @var{cond} simply
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230 controls whether the option is accepted and whether it is printed in
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231 the @option{--help} output.
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232
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233 @item Save
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234 Build the @code{cl_target_option} structure to hold a copy of the
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235 option, add the functions @code{cl_target_option_save} and
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236 @code{cl_target_option_restore} to save and restore the options.
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237 @end table
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