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Copies published by the Free Software Foundation raise 21 1.11 mrg funds for GNU development. --> 22 1.14 mrg <!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ --> 23 1.14 mrg <head> 24 1.14 mrg <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 25 1.13 mrg <title>Installing GCC: Building</title> 26 1.11 mrg 27 1.13 mrg <meta name="description" content="Installing GCC: Building"> 28 1.13 mrg <meta name="keywords" content="Installing GCC: Building"> 29 1.11 mrg <meta name="resource-type" content="document"> 30 1.11 mrg <meta name="distribution" content="global"> 31 1.11 mrg <meta name="Generator" content="makeinfo"> 32 1.11 mrg <style type="text/css"> 33 1.11 mrg <!-- 34 1.11 mrg a.summary-letter {text-decoration: none} 35 1.11 mrg blockquote.indentedblock {margin-right: 0em} 36 1.14 mrg blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} 37 1.14 mrg blockquote.smallquotation {font-size: smaller} 38 1.11 mrg div.display {margin-left: 3.2em} 39 1.11 mrg div.example {margin-left: 3.2em} 40 1.14 mrg div.lisp {margin-left: 3.2em} 41 1.14 mrg div.smalldisplay {margin-left: 3.2em} 42 1.14 mrg div.smallexample {margin-left: 3.2em} 43 1.14 mrg div.smalllisp {margin-left: 3.2em} 44 1.11 mrg kbd {font-style: oblique} 45 1.11 mrg pre.display {font-family: inherit} 46 1.11 mrg pre.format {font-family: inherit} 47 1.11 mrg pre.menu-comment {font-family: serif} 48 1.11 mrg pre.menu-preformatted {font-family: serif} 49 1.14 mrg pre.smalldisplay {font-family: inherit; font-size: smaller} 50 1.14 mrg pre.smallexample {font-size: smaller} 51 1.14 mrg pre.smallformat {font-family: inherit; font-size: smaller} 52 1.14 mrg pre.smalllisp {font-size: smaller} 53 1.11 mrg span.nolinebreak {white-space: nowrap} 54 1.11 mrg span.roman {font-family: initial; font-weight: normal} 55 1.11 mrg span.sansserif {font-family: sans-serif; font-weight: normal} 56 1.11 mrg ul.no-bullet {list-style: none} 57 1.11 mrg --> 58 1.11 mrg </style> 59 1.11 mrg 60 1.11 mrg 61 1.1 mrg </head> 62 1.11 mrg 63 1.11 mrg <body lang="en"> 64 1.13 mrg <h1 class="settitle" align="center">Installing GCC: Building</h1> 65 1.11 mrg 66 1.11 mrg 67 1.11 mrg 68 1.11 mrg 69 1.11 mrg 70 1.11 mrg 71 1.11 mrg 72 1.11 mrg 73 1.11 mrg 74 1.11 mrg 75 1.11 mrg 76 1.11 mrg 77 1.11 mrg 78 1.11 mrg 79 1.11 mrg 80 1.11 mrg 81 1.11 mrg 82 1.11 mrg 83 1.11 mrg 84 1.11 mrg 85 1.14 mrg <a name="index-Installing-GCC_003a-Building"></a> 86 1.11 mrg 87 1.11 mrg <p>Now that GCC is configured, you are ready to build the compiler and 88 1.10 mrg runtime libraries. 89 1.11 mrg </p> 90 1.11 mrg <p>Some commands executed when making the compiler may fail (return a 91 1.11 mrg nonzero status) and be ignored by <code>make</code>. These failures, which 92 1.1 mrg are often due to files that were not found, are expected, and can safely 93 1.1 mrg be ignored. 94 1.11 mrg </p> 95 1.11 mrg <p>It is normal to have compiler warnings when compiling certain files. 96 1.1 mrg Unless you are a GCC developer, you can generally ignore these warnings 97 1.1 mrg unless they cause compilation to fail. Developers should attempt to fix 98 1.1 mrg any warnings encountered, however they can temporarily continue past 99 1.1 mrg warnings-as-errors by specifying the configure flag 100 1.11 mrg <samp>--disable-werror</samp>. 101 1.11 mrg </p> 102 1.11 mrg <p>On certain old systems, defining certain environment variables such as 103 1.11 mrg <code>CC</code> can interfere with the functioning of <code>make</code>. 104 1.11 mrg </p> 105 1.11 mrg <p>If you encounter seemingly strange errors when trying to build the 106 1.1 mrg compiler in a directory other than the source directory, it could be 107 1.1 mrg because you have previously configured the compiler in the source 108 1.1 mrg directory. Make sure you have done all the necessary preparations. 109 1.11 mrg </p> 110 1.11 mrg <p>If you build GCC on a BSD system using a directory stored in an old System 111 1.11 mrg V file system, problems may occur in running <code>fixincludes</code> if the 112 1.11 mrg System V file system doesn’t support symbolic links. These problems 113 1.1 mrg result in a failure to fix the declaration of <code>size_t</code> in 114 1.11 mrg <samp>sys/types.h</samp>. If you find that <code>size_t</code> is a signed type and 115 1.1 mrg that type mismatches occur, this could be the cause. 116 1.11 mrg </p> 117 1.11 mrg <p>The solution is not to use such a directory for building GCC. 118 1.11 mrg </p> 119 1.11 mrg <p>Similarly, when building from the source repository or snapshots, or if you modify 120 1.11 mrg <samp>*.l</samp> files, you need the Flex lexical analyzer generator 121 1.11 mrg installed. If you do not modify <samp>*.l</samp> files, releases contain 122 1.1 mrg the Flex-generated files and you do not need Flex installed to build 123 1.1 mrg them. There is still one Flex-based lexical analyzer (part of the 124 1.1 mrg build machinery, not of GCC itself) that is used even if you only 125 1.1 mrg build the C front end. 126 1.11 mrg </p> 127 1.11 mrg <p>When building from the source repository or snapshots, or if you modify Texinfo 128 1.1 mrg documentation, you need version 4.7 or later of Texinfo installed if you 129 1.1 mrg want Info documentation to be regenerated. Releases contain Info 130 1.1 mrg documentation pre-built for the unmodified documentation in the release. 131 1.11 mrg </p> 132 1.14 mrg <a name="Building-a-native-compiler"></a> 133 1.11 mrg <h3 class="section">Building a native compiler</h3> 134 1.1 mrg 135 1.1 mrg <p>For a native build, the default configuration is to perform 136 1.11 mrg a 3-stage bootstrap of the compiler when ‘<samp>make</samp>’ is invoked. 137 1.1 mrg This will build the entire GCC system and ensure that it compiles 138 1.11 mrg itself correctly. It can be disabled with the <samp>--disable-bootstrap</samp> 139 1.11 mrg parameter to ‘<samp>configure</samp>’, but bootstrapping is suggested because 140 1.1 mrg the compiler will be tested more completely and could also have 141 1.1 mrg better performance. 142 1.11 mrg </p> 143 1.11 mrg <p>The bootstrapping process will complete the following steps: 144 1.11 mrg </p> 145 1.11 mrg <ul> 146 1.11 mrg <li> Build tools necessary to build the compiler. 147 1.1 mrg 148 1.11 mrg </li><li> Perform a 3-stage bootstrap of the compiler. This includes building 149 1.1 mrg three times the target tools for use by the compiler such as binutils 150 1.1 mrg (bfd, binutils, gas, gprof, ld, and opcodes) if they have been 151 1.1 mrg individually linked or moved into the top level GCC source tree before 152 1.1 mrg configuring. 153 1.1 mrg 154 1.11 mrg </li><li> Perform a comparison test of the stage2 and stage3 compilers. 155 1.1 mrg 156 1.11 mrg </li><li> Build runtime libraries using the stage3 compiler from the previous step. 157 1.1 mrg 158 1.11 mrg </li></ul> 159 1.1 mrg 160 1.11 mrg <p>If you are short on disk space you might consider ‘<samp>make 161 1.11 mrg bootstrap-lean</samp>’ instead. The sequence of compilation is the 162 1.1 mrg same described above, but object files from the stage1 and 163 1.1 mrg stage2 of the 3-stage bootstrap of the compiler are deleted as 164 1.1 mrg soon as they are no longer needed. 165 1.11 mrg </p> 166 1.11 mrg <p>If you wish to use non-default GCC flags when compiling the stage2 167 1.1 mrg and stage3 compilers, set <code>BOOT_CFLAGS</code> on the command line when 168 1.11 mrg doing ‘<samp>make</samp>’. For example, if you want to save additional space 169 1.1 mrg during the bootstrap and in the final installation as well, you can 170 1.1 mrg build the compiler binaries without debugging information as in the 171 1.1 mrg following example. This will save roughly 40% of disk space both for 172 1.1 mrg the bootstrap and the final installation. (Libraries will still contain 173 1.1 mrg debugging information.) 174 1.11 mrg </p> 175 1.14 mrg <div class="smallexample"> 176 1.14 mrg <pre class="smallexample">make BOOT_CFLAGS='-O' bootstrap 177 1.11 mrg </pre></div> 178 1.1 mrg 179 1.11 mrg <p>You can place non-default optimization flags into <code>BOOT_CFLAGS</code>; they 180 1.11 mrg are less well tested here than the default of ‘<samp>-g -O2</samp>’, but should 181 1.1 mrg still work. In a few cases, you may find that you need to specify special 182 1.11 mrg flags such as <samp>-msoft-float</samp> here to complete the bootstrap; or, 183 1.1 mrg if the native compiler miscompiles the stage1 compiler, you may need 184 1.1 mrg to work around this, by choosing <code>BOOT_CFLAGS</code> to avoid the parts 185 1.11 mrg of the stage1 compiler that were miscompiled, or by using ‘<samp>make 186 1.11 mrg bootstrap4</samp>’ to increase the number of stages of bootstrap. 187 1.11 mrg </p> 188 1.11 mrg <p><code>BOOT_CFLAGS</code> does not apply to bootstrapped target libraries. 189 1.1 mrg Since these are always compiled with the compiler currently being 190 1.1 mrg bootstrapped, you can use <code>CFLAGS_FOR_TARGET</code> to modify their 191 1.11 mrg compilation flags, as for non-bootstrapped target libraries. 192 1.1 mrg Again, if the native compiler miscompiles the stage1 compiler, you may 193 1.1 mrg need to work around this by avoiding non-working parts of the stage1 194 1.1 mrg compiler. Use <code>STAGE1_TFLAGS</code> to this end. 195 1.11 mrg </p> 196 1.11 mrg <p>If you used the flag <samp>--enable-languages=…</samp> to restrict 197 1.11 mrg the compilers to be built, only those you’ve actually enabled will be 198 1.1 mrg built. This will of course only build those runtime libraries, for 199 1.1 mrg which the particular compiler has been built. Please note, 200 1.11 mrg that re-defining <code>LANGUAGES</code> when calling ‘<samp>make</samp>’ 201 1.1 mrg <strong>does not</strong> work anymore! 202 1.11 mrg </p> 203 1.11 mrg <p>If the comparison of stage2 and stage3 fails, this normally indicates 204 1.1 mrg that the stage2 compiler has compiled GCC incorrectly, and is therefore 205 1.1 mrg a potentially serious bug which you should investigate and report. (On 206 1.1 mrg a few systems, meaningful comparison of object files is impossible; they 207 1.1 mrg always appear “different”. If you encounter this problem, you will 208 1.11 mrg need to disable comparison in the <samp>Makefile</samp>.) 209 1.11 mrg </p> 210 1.11 mrg <p>If you do not want to bootstrap your compiler, you can configure with 211 1.11 mrg <samp>--disable-bootstrap</samp>. In particular cases, you may want to 212 1.1 mrg bootstrap your compiler even if the target system is not the same as 213 1.1 mrg the one you are building on: for example, you could build a 214 1.1 mrg <code>powerpc-unknown-linux-gnu</code> toolchain on a 215 1.1 mrg <code>powerpc64-unknown-linux-gnu</code> host. In this case, pass 216 1.11 mrg <samp>--enable-bootstrap</samp> to the configure script. 217 1.11 mrg </p> 218 1.11 mrg <p><code>BUILD_CONFIG</code> can be used to bring in additional customization 219 1.11 mrg to the build. It can be set to a whitespace-separated list of names. 220 1.11 mrg For each such <code>NAME</code>, top-level <samp>config/<code>NAME</code>.mk</samp> will 221 1.11 mrg be included by the top-level <samp>Makefile</samp>, bringing in any settings 222 1.1 mrg it contains. The default <code>BUILD_CONFIG</code> can be set using the 223 1.11 mrg configure option <samp>--with-build-config=<code>NAME</code>...</samp>. Some 224 1.1 mrg examples of supported build configurations are: 225 1.11 mrg </p> 226 1.11 mrg <dl compact="compact"> 227 1.14 mrg <dt>‘<samp>bootstrap-O1</samp>’</dt> 228 1.11 mrg <dd><p>Removes any <samp>-O</samp>-started option from <code>BOOT_CFLAGS</code>, and adds 229 1.11 mrg <samp>-O1</samp> to it. ‘<samp>BUILD_CONFIG=bootstrap-O1</samp>’ is equivalent to 230 1.11 mrg ‘<samp>BOOT_CFLAGS='-g -O1'</samp>’. 231 1.11 mrg </p> 232 1.11 mrg </dd> 233 1.14 mrg <dt>‘<samp>bootstrap-O3</samp>’</dt> 234 1.14 mrg <dt>‘<samp>bootstrap-Og</samp>’</dt> 235 1.11 mrg <dd><p>Analogous to <code>bootstrap-O1</code>. 236 1.11 mrg </p> 237 1.11 mrg </dd> 238 1.14 mrg <dt>‘<samp>bootstrap-lto</samp>’</dt> 239 1.11 mrg <dd><p>Enables Link-Time Optimization for host tools during bootstrapping. 240 1.11 mrg ‘<samp>BUILD_CONFIG=bootstrap-lto</samp>’ is equivalent to adding 241 1.11 mrg <samp>-flto</samp> to ‘<samp>BOOT_CFLAGS</samp>’. This option assumes that the host 242 1.5 mrg supports the linker plugin (e.g. GNU ld version 2.21 or later or GNU gold 243 1.5 mrg version 2.21 or later). 244 1.11 mrg </p> 245 1.11 mrg </dd> 246 1.14 mrg <dt>‘<samp>bootstrap-lto-noplugin</samp>’</dt> 247 1.11 mrg <dd><p>This option is similar to <code>bootstrap-lto</code>, but is intended for 248 1.11 mrg hosts that do not support the linker plugin. Without the linker plugin 249 1.11 mrg static libraries are not compiled with link-time optimizations. Since 250 1.11 mrg the GCC middle end and back end are in <samp>libbackend.a</samp> this means 251 1.5 mrg that only the front end is actually LTO optimized. 252 1.11 mrg </p> 253 1.11 mrg </dd> 254 1.14 mrg <dt>‘<samp>bootstrap-lto-lean</samp>’</dt> 255 1.12 mrg <dd><p>This option is similar to <code>bootstrap-lto</code>, but is intended for 256 1.12 mrg faster build by only using LTO in the final bootstrap stage. 257 1.12 mrg With ‘<samp>make profiledbootstrap</samp>’ the LTO frontend 258 1.12 mrg is trained only on generator files. 259 1.12 mrg </p> 260 1.12 mrg </dd> 261 1.14 mrg <dt>‘<samp>bootstrap-debug</samp>’</dt> 262 1.11 mrg <dd><p>Verifies that the compiler generates the same executable code, whether 263 1.1 mrg or not it is asked to emit debug information. To this end, this 264 1.1 mrg option builds stage2 host programs without debug information, and uses 265 1.11 mrg <samp>contrib/compare-debug</samp> to compare them with the stripped stage3 266 1.1 mrg object files. If <code>BOOT_CFLAGS</code> is overridden so as to not enable 267 1.11 mrg debug information, stage2 will have it, and stage3 won’t. This option 268 1.1 mrg is enabled by default when GCC bootstrapping is enabled, if 269 1.1 mrg <code>strip</code> can turn object files compiled with and without debug 270 1.1 mrg info into identical object files. In addition to better test 271 1.1 mrg coverage, this option makes default bootstraps faster and leaner. 272 1.11 mrg </p> 273 1.11 mrg </dd> 274 1.14 mrg <dt>‘<samp>bootstrap-debug-big</samp>’</dt> 275 1.11 mrg <dd><p>Rather than comparing stripped object files, as in 276 1.1 mrg <code>bootstrap-debug</code>, this option saves internal compiler dumps 277 1.1 mrg during stage2 and stage3 and compares them as well, which helps catch 278 1.1 mrg additional potential problems, but at a great cost in terms of disk 279 1.11 mrg space. It can be specified in addition to ‘<samp>bootstrap-debug</samp>’. 280 1.11 mrg </p> 281 1.11 mrg </dd> 282 1.14 mrg <dt>‘<samp>bootstrap-debug-lean</samp>’</dt> 283 1.11 mrg <dd><p>This option saves disk space compared with <code>bootstrap-debug-big</code>, 284 1.1 mrg but at the expense of some recompilation. Instead of saving the dumps 285 1.1 mrg of stage2 and stage3 until the final compare, it uses 286 1.11 mrg <samp>-fcompare-debug</samp> to generate, compare and remove the dumps 287 1.1 mrg during stage3, repeating the compilation that already took place in 288 1.1 mrg stage2, whose dumps were not saved. 289 1.11 mrg </p> 290 1.11 mrg </dd> 291 1.14 mrg <dt>‘<samp>bootstrap-debug-lib</samp>’</dt> 292 1.11 mrg <dd><p>This option tests executable code invariance over debug information 293 1.1 mrg generation on target libraries, just like <code>bootstrap-debug-lean</code> 294 1.1 mrg tests it on host programs. It builds stage3 libraries with 295 1.11 mrg <samp>-fcompare-debug</samp>, and it can be used along with any of the 296 1.1 mrg <code>bootstrap-debug</code> options above. 297 1.11 mrg </p> 298 1.11 mrg <p>There aren’t <code>-lean</code> or <code>-big</code> counterparts to this option 299 1.1 mrg because most libraries are only build in stage3, so bootstrap compares 300 1.1 mrg would not get significant coverage. Moreover, the few libraries built 301 1.11 mrg in stage2 are used in stage3 host programs, so we wouldn’t want to 302 1.1 mrg compile stage2 libraries with different options for comparison purposes. 303 1.11 mrg </p> 304 1.11 mrg </dd> 305 1.14 mrg <dt>‘<samp>bootstrap-debug-ckovw</samp>’</dt> 306 1.11 mrg <dd><p>Arranges for error messages to be issued if the compiler built on any 307 1.11 mrg stage is run without the option <samp>-fcompare-debug</samp>. This is 308 1.11 mrg useful to verify the full <samp>-fcompare-debug</samp> testing coverage. It 309 1.1 mrg must be used along with <code>bootstrap-debug-lean</code> and 310 1.1 mrg <code>bootstrap-debug-lib</code>. 311 1.11 mrg </p> 312 1.11 mrg </dd> 313 1.14 mrg <dt>‘<samp>bootstrap-cet</samp>’</dt> 314 1.11 mrg <dd><p>This option enables Intel CET for host tools during bootstrapping. 315 1.11 mrg ‘<samp>BUILD_CONFIG=bootstrap-cet</samp>’ is equivalent to adding 316 1.11 mrg <samp>-fcf-protection</samp> to ‘<samp>BOOT_CFLAGS</samp>’. This option 317 1.11 mrg assumes that the host supports Intel CET (e.g. GNU assembler version 318 1.11 mrg 2.30 or later). 319 1.11 mrg </p> 320 1.11 mrg </dd> 321 1.14 mrg <dt>‘<samp>bootstrap-time</samp>’</dt> 322 1.11 mrg <dd><p>Arranges for the run time of each program started by the GCC driver, 323 1.11 mrg built in any stage, to be logged to <samp>time.log</samp>, in the top level of 324 1.1 mrg the build tree. 325 1.11 mrg </p> 326 1.11 mrg </dd> 327 1.14 mrg <dt>‘<samp>bootstrap-asan</samp>’</dt> 328 1.13 mrg <dd><p>Compiles GCC itself using Address Sanitization in order to catch invalid memory 329 1.13 mrg accesses within the GCC code. 330 1.13 mrg </p> 331 1.13 mrg </dd> 332 1.15 mrg <dt>‘<samp>bootstrap-hwasan</samp>’</dt> 333 1.15 mrg <dd><p>Compiles GCC itself using HWAddress Sanitization in order to catch invalid 334 1.15 mrg memory accesses within the GCC code. This option is only available on AArch64 335 1.15 mrg systems that are running Linux kernel version 5.4 or later. 336 1.15 mrg </p> 337 1.15 mrg </dd> 338 1.11 mrg </dl> 339 1.1 mrg 340 1.14 mrg <a name="Building-a-cross-compiler"></a> 341 1.11 mrg <h3 class="section">Building a cross compiler</h3> 342 1.1 mrg 343 1.1 mrg <p>When building a cross compiler, it is not generally possible to do a 344 1.1 mrg 3-stage bootstrap of the compiler. This makes for an interesting problem 345 1.1 mrg as parts of GCC can only be built with GCC. 346 1.11 mrg </p> 347 1.11 mrg <p>To build a cross compiler, we recommend first building and installing a 348 1.1 mrg native compiler. You can then use the native GCC compiler to build the 349 1.1 mrg cross compiler. The installed native compiler needs to be GCC version 350 1.1 mrg 2.95 or later. 351 1.11 mrg </p> 352 1.11 mrg <p>Assuming you have already installed a native copy of GCC and configured 353 1.11 mrg your cross compiler, issue the command <code>make</code>, which performs the 354 1.1 mrg following steps: 355 1.11 mrg </p> 356 1.11 mrg <ul> 357 1.11 mrg <li> Build host tools necessary to build the compiler. 358 1.1 mrg 359 1.11 mrg </li><li> Build target tools for use by the compiler such as binutils (bfd, 360 1.1 mrg binutils, gas, gprof, ld, and opcodes) 361 1.1 mrg if they have been individually linked or moved into the top level GCC source 362 1.1 mrg tree before configuring. 363 1.1 mrg 364 1.11 mrg </li><li> Build the compiler (single stage only). 365 1.10 mrg 366 1.11 mrg </li><li> Build runtime libraries using the compiler from the previous step. 367 1.11 mrg </li></ul> 368 1.1 mrg 369 1.11 mrg <p>Note that if an error occurs in any step the make process will exit. 370 1.11 mrg </p> 371 1.11 mrg <p>If you are not building GNU binutils in the same source tree as GCC, 372 1.1 mrg you will need a cross-assembler and cross-linker installed before 373 1.1 mrg configuring GCC. Put them in the directory 374 1.11 mrg <samp><var>prefix</var>/<var>target</var>/bin</samp>. Here is a table of the tools 375 1.1 mrg you should put in this directory: 376 1.11 mrg </p> 377 1.11 mrg <dl compact="compact"> 378 1.14 mrg <dt><samp>as</samp></dt> 379 1.11 mrg <dd><p>This should be the cross-assembler. 380 1.11 mrg </p> 381 1.11 mrg </dd> 382 1.14 mrg <dt><samp>ld</samp></dt> 383 1.11 mrg <dd><p>This should be the cross-linker. 384 1.11 mrg </p> 385 1.11 mrg </dd> 386 1.14 mrg <dt><samp>ar</samp></dt> 387 1.11 mrg <dd><p>This should be the cross-archiver: a program which can manipulate 388 1.11 mrg archive files (linker libraries) in the target machine’s format. 389 1.11 mrg </p> 390 1.11 mrg </dd> 391 1.14 mrg <dt><samp>ranlib</samp></dt> 392 1.11 mrg <dd><p>This should be a program to construct a symbol table in an archive file. 393 1.11 mrg </p></dd> 394 1.1 mrg </dl> 395 1.1 mrg 396 1.11 mrg <p>The installation of GCC will find these programs in that directory, 397 1.1 mrg and copy or link them to the proper place to for the cross-compiler to 398 1.1 mrg find them when run later. 399 1.11 mrg </p> 400 1.11 mrg <p>The easiest way to provide these files is to build the Binutils package. 401 1.11 mrg Configure it with the same <samp>--host</samp> and <samp>--target</samp> 402 1.1 mrg options that you use for configuring GCC, then build and install 403 1.1 mrg them. They install their executables automatically into the proper 404 1.1 mrg directory. Alas, they do not support all the targets that GCC 405 1.1 mrg supports. 406 1.11 mrg </p> 407 1.11 mrg <p>If you are not building a C library in the same source tree as GCC, 408 1.1 mrg you should also provide the target libraries and headers before 409 1.1 mrg configuring GCC, specifying the directories with 410 1.11 mrg <samp>--with-sysroot</samp> or <samp>--with-headers</samp> and 411 1.11 mrg <samp>--with-libs</samp>. Many targets also require “start files” such 412 1.11 mrg as <samp>crt0.o</samp> and 413 1.11 mrg <samp>crtn.o</samp> which are linked into each executable. There may be several 414 1.11 mrg alternatives for <samp>crt0.o</samp>, for use with profiling or other 415 1.11 mrg compilation options. Check your target’s definition of 416 1.1 mrg <code>STARTFILE_SPEC</code> to find out what start files it uses. 417 1.11 mrg </p> 418 1.14 mrg <a name="Building-in-parallel"></a> 419 1.11 mrg <h3 class="section">Building in parallel</h3> 420 1.1 mrg 421 1.1 mrg <p>GNU Make 3.80 and above, which is necessary to build GCC, support 422 1.11 mrg building in parallel. To activate this, you can use ‘<samp>make -j 2</samp>’ 423 1.11 mrg instead of ‘<samp>make</samp>’. You can also specify a bigger number, and 424 1.1 mrg in most cases using a value greater than the number of processors in 425 1.1 mrg your machine will result in fewer and shorter I/O latency hits, thus 426 1.1 mrg improving overall throughput; this is especially true for slow drives 427 1.1 mrg and network filesystems. 428 1.11 mrg </p> 429 1.14 mrg <a name="Building-the-Ada-compiler"></a> 430 1.11 mrg <h3 class="section">Building the Ada compiler</h3> 431 1.1 mrg 432 1.13 mrg <p><a href="prerequisites.html#GNAT-prerequisite">GNAT prerequisites</a>. 433 1.11 mrg </p> 434 1.15 mrg <a name="Building-the-D-compiler"></a> 435 1.15 mrg <h3 class="section">Building the D compiler</h3> 436 1.15 mrg 437 1.15 mrg <p><a href="prerequisites.html#GDC-prerequisite">GDC prerequisites</a>. 438 1.15 mrg </p> 439 1.14 mrg <a name="Building-with-profile-feedback"></a> 440 1.11 mrg <h3 class="section">Building with profile feedback</h3> 441 1.1 mrg 442 1.1 mrg <p>It is possible to use profile feedback to optimize the compiler itself. This 443 1.1 mrg should result in a faster compiler binary. Experiments done on x86 using gcc 444 1.1 mrg 3.3 showed approximately 7 percent speedup on compiling C programs. To 445 1.1 mrg bootstrap the compiler with profile feedback, use <code>make profiledbootstrap</code>. 446 1.11 mrg </p> 447 1.11 mrg <p>When ‘<samp>make profiledbootstrap</samp>’ is run, it will first build a <code>stage1</code> 448 1.1 mrg compiler. This compiler is used to build a <code>stageprofile</code> compiler 449 1.1 mrg instrumented to collect execution counts of instruction and branch 450 1.11 mrg probabilities. Training run is done by building <code>stagetrain</code> 451 1.11 mrg compiler. Finally a <code>stagefeedback</code> compiler is built 452 1.11 mrg using the information collected. 453 1.11 mrg </p> 454 1.11 mrg <p>Unlike standard bootstrap, several additional restrictions apply. The 455 1.11 mrg compiler used to build <code>stage1</code> needs to support a 64-bit integral type. 456 1.8 mrg It is recommended to only use GCC for this. 457 1.11 mrg </p> 458 1.11 mrg <p>On Linux/x86_64 hosts with some restrictions (no virtualization) it is 459 1.11 mrg also possible to do autofdo build with ‘<samp>make 460 1.11 mrg autoprofiledback</samp>’. This uses Linux perf to sample branches in the 461 1.11 mrg binary and then rebuild it with feedback derived from the profile. 462 1.10 mrg Linux perf and the <code>autofdo</code> toolkit needs to be installed for 463 1.10 mrg this. 464 1.11 mrg </p> 465 1.11 mrg <p>Only the profile from the current build is used, so when an error 466 1.10 mrg occurs it is recommended to clean before restarting. Otherwise 467 1.10 mrg the code quality may be much worse. 468 1.11 mrg </p> 469 1.11 mrg <hr /> 470 1.11 mrg <p> 471 1.11 mrg <p><a href="./index.html">Return to the GCC Installation page</a> 472 1.11 mrg </p> 473 1.11 mrg 474 1.11 mrg 475 1.11 mrg 476 1.11 mrg 477 1.11 mrg 478 1.11 mrg 479 1.14 mrg <hr> 480 1.8 mrg 481 1.8 mrg 482 1.7 mrg 483 1.11 mrg </body> 484 1.11 mrg </html> 485