mingw/html/lib/B/CC.html

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  13 <big><strong><span class="block">&nbsp;B::CC - Perl compiler's optimized C translation backend</span></strong></big>
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  17 <p><a name="__index__"></a></p>
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  19
  20 <ul>
  21
  22         <li><a href="#name">NAME</a></li>
  23         <li><a href="#synopsis">SYNOPSIS</a></li>
  24         <li><a href="#description">DESCRIPTION</a></li>
  25         <li><a href="#options">OPTIONS</a></li>
  26         <li><a href="#examples">EXAMPLES</a></li>
  27         <li><a href="#bugs">BUGS</a></li>
  28         <li><a href="#differences">DIFFERENCES</a></li>
  29         <ul>
  30
  31                 <li><a href="#loops">Loops</a></li>
  32                 <li><a href="#context_of___">Context of ``..''</a></li>
  33                 <li><a href="#arithmetic">Arithmetic</a></li>
  34                 <li><a href="#deprecated_features">Deprecated features</a></li>
  35         </ul>
  36
  37         <li><a href="#author">AUTHOR</a></li>
  38 </ul>
  39 <!-- INDEX END -->
  40
  41 <hr />
  42 <p>
  43 </p>
  44 <h1><a name="name">NAME</a></h1>
  45 <p>B::CC - Perl compiler's optimized C translation backend</p>
  46 <p>
  47 </p>
  48 <hr />
  49 <h1><a name="synopsis">SYNOPSIS</a></h1>
  50 <pre>
  51         perl -MO=CC[,OPTIONS] foo.pl</pre>
  52 <p>
  53 </p>
  54 <hr />
  55 <h1><a name="description">DESCRIPTION</a></h1>
  56 <p>This compiler backend takes Perl source and generates C source code
  57 corresponding to the flow of your program. In other words, this
  58 backend is somewhat a ``real'' compiler in the sense that many people
  59 think about compilers. Note however that, currently, it is a very
  60 poor compiler in that although it generates (mostly, or at least
  61 sometimes) correct code, it performs relatively few optimisations.
  62 This will change as the compiler develops. The result is that
  63 running an executable compiled with this backend may start up more
  64 quickly than running the original Perl program (a feature shared
  65 by the <strong>C</strong> compiler backend--see <em>B::C</em>) and may also execute
  66 slightly faster. This is by no means a good optimising compiler--yet.</p>
  67 <p>
  68 </p>
  69 <hr />
  70 <h1><a name="options">OPTIONS</a></h1>
  71 <p>If there are any non-option arguments, they are taken to be
  72 names of objects to be saved (probably doesn't work properly yet).
  73 Without extra arguments, it saves the main program.</p>
  74 <dl>
  75 <dt><strong><a name="item__2dofilename"><strong>-ofilename</strong></a></strong>
  76
  77 <dd>
  78 <p>Output to filename instead of STDOUT</p>
  79 </dd>
  80 </li>
  81 <dt><strong><a name="item__2dv"><strong>-v</strong></a></strong>
  82
  83 <dd>
  84 <p>Verbose compilation (currently gives a few compilation statistics).</p>
  85 </dd>
  86 </li>
  87 <dt><strong><a name="item__2d_2d"><strong>--</strong></a></strong>
  88
  89 <dd>
  90 <p>Force end of options</p>
  91 </dd>
  92 </li>
  93 <dt><strong><a name="item__2dupackname"><strong>-uPackname</strong></a></strong>
  94
  95 <dd>
  96 <p>Force apparently unused subs from package Packname to be compiled.
  97 This allows programs to use eval ``foo()'' even when sub foo is never
  98 seen to be used at compile time. The down side is that any subs which
  99 really are never used also have code generated. This option is
 100 necessary, for example, if you have a signal handler foo which you
 101 initialise with <code>$SIG{BAR} = &quot;foo&quot;</code>.  A better fix, though, is just
 102 to change it to <code>$SIG{BAR} = \&amp;foo</code>. You can have multiple <strong>-u</strong>
 103 options. The compiler tries to figure out which packages may possibly
 104 have subs in which need compiling but the current version doesn't do
 105 it very well. In particular, it is confused by nested packages (i.e.
 106 of the form <code>A::B</code>) where package <a href="file://C|\msysgit\mingw\html/pod/perlguts.html#item_a"><code>A</code></a> does not contain any subs.</p>
 107 </dd>
 108 </li>
 109 <dt><strong><a name="item__2dmmodulename"><strong>-mModulename</strong></a></strong>
 110
 111 <dd>
 112 <p>Instead of generating source for a runnable executable, generate
 113 source for an XSUB module. The boot_Modulename function (which
 114 DynaLoader can look for) does the appropriate initialisation and runs
 115 the main part of the Perl source that is being compiled.</p>
 116 </dd>
 117 </li>
 118 <dt><strong><a name="item__2dd"><strong>-D</strong></a></strong>
 119
 120 <dd>
 121 <p>Debug options (concatenated or separate flags like <code>perl -D</code>).</p>
 122 </dd>
 123 </li>
 124 <dt><strong><a name="item__2ddr"><strong>-Dr</strong></a></strong>
 125
 126 <dd>
 127 <p>Writes debugging output to STDERR just as it's about to write to the
 128 program's runtime (otherwise writes debugging info as comments in
 129 its C output).</p>
 130 </dd>
 131 </li>
 132 <dt><strong><a name="item__2ddo"><strong>-DO</strong></a></strong>
 133
 134 <dd>
 135 <p>Outputs each OP as it's compiled</p>
 136 </dd>
 137 </li>
 138 <dt><strong><a name="item__2dds"><strong>-Ds</strong></a></strong>
 139
 140 <dd>
 141 <p>Outputs the contents of the shadow stack at each OP</p>
 142 </dd>
 143 </li>
 144 <dt><strong><a name="item__2ddp"><strong>-Dp</strong></a></strong>
 145
 146 <dd>
 147 <p>Outputs the contents of the shadow pad of lexicals as it's loaded for
 148 each sub or the main program.</p>
 149 </dd>
 150 </li>
 151 <dt><strong><a name="item__2ddq"><strong>-Dq</strong></a></strong>
 152
 153 <dd>
 154 <p>Outputs the name of each fake PP function in the queue as it's about
 155 to process it.</p>
 156 </dd>
 157 </li>
 158 <dt><strong><a name="item__2ddl"><strong>-Dl</strong></a></strong>
 159
 160 <dd>
 161 <p>Output the filename and line number of each original line of Perl
 162 code as it's processed (<code>pp_nextstate</code>).</p>
 163 </dd>
 164 </li>
 165 <dt><strong><a name="item__2ddt"><strong>-Dt</strong></a></strong>
 166
 167 <dd>
 168 <p>Outputs timing information of compilation stages.</p>
 169 </dd>
 170 </li>
 171 <dt><strong><a name="item__2df"><strong>-f</strong></a></strong>
 172
 173 <dd>
 174 <p>Force optimisations on or off one at a time.</p>
 175 </dd>
 176 </li>
 177 <dt><strong><a name="item__2dffreetmps_2deach_2dbblock"><strong>-ffreetmps-each-bblock</strong></a></strong>
 178
 179 <dd>
 180 <p>Delays FREETMPS from the end of each statement to the end of the each
 181 basic block.</p>
 182 </dd>
 183 </li>
 184 <dt><strong><a name="item__2dffreetmps_2deach_2dloop"><strong>-ffreetmps-each-loop</strong></a></strong>
 185
 186 <dd>
 187 <p>Delays FREETMPS from the end of each statement to the end of the group
 188 of basic blocks forming a loop. At most one of the freetmps-each-*
 189 options can be used.</p>
 190 </dd>
 191 </li>
 192 <dt><strong><a name="item__2dfomit_2dtaint"><strong>-fomit-taint</strong></a></strong>
 193
 194 <dd>
 195 <p>Omits generating code for handling perl's tainting mechanism.</p>
 196 </dd>
 197 </li>
 198 <dt><strong><a name="item__2don"><strong>-On</strong></a></strong>
 199
 200 <dd>
 201 <p>Optimisation level (n = 0, 1, 2, ...). <strong>-O</strong> means <strong>-O1</strong>.
 202 Currently, <strong>-O1</strong> sets <strong>-ffreetmps-each-bblock</strong> and <strong>-O2</strong>
 203 sets <strong>-ffreetmps-each-loop</strong>.</p>
 204 </dd>
 205 </li>
 206 </dl>
 207 <p>
 208 </p>
 209 <hr />
 210 <h1><a name="examples">EXAMPLES</a></h1>
 211 <pre>
 212         perl -MO=CC,-O2,-ofoo.c foo.pl
 213         perl cc_harness -o foo foo.c</pre>
 214 <p>Note that <code>cc_harness</code> lives in the <code>B</code> subdirectory of your perl
 215 library directory. The utility called <code>perlcc</code> may also be used to
 216 help make use of this compiler.</p>
 217 <pre>
 218         perl -MO=CC,-mFoo,-oFoo.c Foo.pm
 219         perl cc_harness -shared -c -o Foo.so Foo.c</pre>
 220 <p>
 221 </p>
 222 <hr />
 223 <h1><a name="bugs">BUGS</a></h1>
 224 <p>Plenty. Current status: experimental.</p>
 225 <p>
 226 </p>
 227 <hr />
 228 <h1><a name="differences">DIFFERENCES</a></h1>
 229 <p>These aren't really bugs but they are constructs which are heavily
 230 tied to perl's compile-and-go implementation and with which this
 231 compiler backend cannot cope.</p>
 232 <p>
 233 </p>
 234 <h2><a name="loops">Loops</a></h2>
 235 <p>Standard perl calculates the target of ``next'', ``last'', and ``redo''
 236 at run-time. The compiler calculates the targets at compile-time.
 237 For example, the program</p>
 238 <pre>
 239     sub skip_on_odd { next NUMBER if $_[0] % 2 }
 240     NUMBER: for ($i = 0; $i &lt; 5; $i++) {
 241         skip_on_odd($i);
 242         print $i;
 243     }</pre>
 244 <p>produces the output</p>
 245 <pre>
 246     024</pre>
 247 <p>with standard perl but gives a compile-time error with the compiler.</p>
 248 <p>
 249 </p>
 250 <h2><a name="context_of___">Context of ``..''</a></h2>
 251 <p>The context (scalar or array) of the ``..'' operator determines whether
 252 it behaves as a range or a flip/flop. Standard perl delays until
 253 runtime the decision of which context it is in but the compiler needs
 254 to know the context at compile-time. For example,</p>
 255 <pre>
 256     @a = (4,6,1,0,0,1);
 257     sub range { (shift @a)..(shift @a) }
 258     print range();
 259     while (@a) { print scalar(range()) }</pre>
 260 <p>generates the output</p>
 261 <pre>
 262     456123E0</pre>
 263 <p>with standard Perl but gives a compile-time error with compiled Perl.</p>
 264 <p>
 265 </p>
 266 <h2><a name="arithmetic">Arithmetic</a></h2>
 267 <p>Compiled Perl programs use native C arithmetic much more frequently
 268 than standard perl. Operations on large numbers or on boundary
 269 cases may produce different behaviour.</p>
 270 <p>
 271 </p>
 272 <h2><a name="deprecated_features">Deprecated features</a></h2>
 273 <p>Features of standard perl such as <a href="file://C|\msysgit\mingw\html/pod/perlvar.html#item___"><code>$[</code></a> which have been deprecated
 274 in standard perl since Perl5 was released have not been implemented
 275 in the compiler.
 276
 277 </p>
 278 <p>
 279 </p>
 280 <hr />
 281 <h1><a name="author">AUTHOR</a></h1>
 282 <p>Malcolm Beattie, <code>mbeattie@sable.ox.ac.uk</code>
 283
 284 </p>
 285 <table border="0" width="100%" cellspacing="0" cellpadding="3">
 286 <tr><td class="block" style="background-color: #cccccc" valign="middle">
 287 <big><strong><span class="block">&nbsp;B::CC - Perl compiler's optimized C translation backend</span></strong></big>
 288 </td></tr>
 289 </table>
 290
 291 </body>
 292
 293 </html>