<li><a href="#installcf">Install the GCC Front End</a>
<li><a href="#config">Local LLVM Configuration</a>
<li><a href="#compile">Compiling the LLVM Suite Source Code</a>
+ <li><a href="#cross-compile">Cross-Compiling LLVM</a>
<li><a href="#objfiles">The Location of LLVM Object Files</a>
<li><a href="#optionalconfig">Optional Configuration Items</a>
</ol></li>
</ol></li>
<li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
+ <ol>
+ <li><a href="#tutorial4">Example with llvm-gcc4</a></li>
+ </ol>
<li><a href="#problems">Common Problems</a>
<li><a href="#links">Links</a>
</ul>
<p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
contains all of the tools, libraries, and header files needed to use the low
level virtual machine. It contains an assembler, disassembler, bytecode
-analyzer, and bytecode optimizer. It also contains a test suite that can be
+analyzer and bytecode optimizer. It also contains a test suite that can be
used to test the LLVM tools and the GCC front end.</p>
<p>The second piece is the GCC front end. This component provides a version of
GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
-end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
+end uses the GCC parser to convert code to LLVM. Once
compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
from the LLVM suite.</p>
<li>Install the GCC front end if you intend to compile C or C++:
<ol>
<li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt></li>
- <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
+ <li><tt>gunzip --stdout llvm-gcc.<i>platform</i>.tar.gz | tar -xvf -</tt>
</li>
- <li><tt>cd cfrontend/<i>platform</i><br>
+ <li><tt>cd llvm-gcc3.4/<i>platform</i> (llvm-gcc3.4 only)<br>
./fixheaders</tt></li>
- <li>Add the cfrontend's "bin" directory to your PATH variable.</li>
+ <li>Add llvm-gcc's "bin" directory to your PATH variable.</li>
</ol></li>
<li>Get the LLVM Source Code
<ol>
<li><tt>gmake -k |& tee gnumake.out
# this is csh or tcsh syntax</tt></li>
- <li>If you get an "internal compiler error (ICE)" see <a href="#brokengcc">below</a>.</li>
+ <li>If you get an "internal compiler error (ICE)" or test failures, see
+ <a href="#brokengcc">below</a>.</li>
</ol>
</ol>
<p>LLVM is known to work on the following platforms:</p>
-<table cellpadding="3">
+<table cellpadding="3" summary="Known LLVM platforms">
<tr>
<th>OS</th>
<th>Arch</th>
<td>PowerPC</td>
<td>GCC</td>
</tr>
+<tr>
+ <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
+ <td>x86</td>
+ <td>GCC</td>
+
+</tr>
<tr>
<td>Cygwin/Win32</td>
- <td>x86<sup><a href="#pf_1">1</a></sup></td>
+ <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a></sup></td>
<td>GCC 3.4.X, binutils 2.15</td>
</tr>
<tr>
<td>MinGW/Win32</td>
- <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a></sup></td>
+ <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,<a href="#pf_8">8</a></sup></td>
<td>GCC 3.4.X, binutils 2.15</td>
</tr>
<tr>
<p>LLVM has partial support for the following platforms:</p>
-<table>
+<table summary="LLVM partial platform support">
<tr>
<th>OS</th>
<th>Arch</th>
<li><a name="pf_3">No native code generation</a></li>
<li><a name="pf_4">Build is not complete: one or more tools don't link</a></li>
<li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
-<li><a name="pf_6">The port is done using the MSYS shell.
+<li><a name="pf_6">The port is done using the MSYS shell.</a>
<a href="http://www.mingw.org/MinGWiki/">Download</a> and install
-bison (excl. M4.exe) and flex in that order. Build binutils-2.15 from source,
-if necessary.</li>
+bison (excl. M4.exe) and flex in that order. Build binutils-2.15 from source,
+if necessary. Bison & flex can be also grabbed from GNUWin32 sf.net
+project.</li>
<li><a name="pf_7">Native code generation exists but is not complete.</a></li>
+<li><a name="pf_8">Binutils</a> up to post-2.17 has bug in bfd/cofflink.c
+ preventing LLVM from building correctly. Several workarounds have been
+ introduced into LLVM build system, but the bug can occur anytime in the
+ future. We highly recommend that you rebuild your current binutils with the
+ patch from <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=2659">
+ Binutils bugzilla</a>, if it wasn't already applied.</li>
</ol>
</div>
is the usual name for the software package that LLVM depends on. The Version
column provides "known to work" versions of the package. The Notes column
describes how LLVM uses the package and provides other details.</p>
- <table>
+ <table summary="Packages required to compile LLVM">
<tr><th>Package</th><th>Version</th><th>Notes</th></tr>
<tr>
<p><b>Notes:</b></p>
<div class="doc_notes">
<ol>
- <li><a name="sf3">Only the C and C++ languages are needed so there's no
+ <li><a name="sf1">Only the C and C++ languages are needed so there's no
need to build the other languages for LLVM's purposes.</a> See
<a href="#brokengcc">below</a> for specific version info.</li>
<li><a name="sf2">You only need CVS if you intend to build from the
<p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
bugs in the compiler. In particular, several versions of GCC crash when trying
-to compile LLVM. We routinely use GCC 3.3.3 and GCC 3.4.0 and have had success
-with them (however, see below). Other versions of GCC will probably
-work as well. GCC versions listed
+to compile LLVM. We routinely use GCC 3.3.3, 3.4.0, and Apple 4.0.1
+successfully with them (however, see below). Other versions of GCC will
+probably work as well. GCC versions listed
here are known to not work. If you are using one of these versions, please try
to upgrade your GCC to something more recent. If you run into a problem with a
version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
possibly others) does not compile LLVM correctly (it appears that exception
handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
to a newer version of GCC.</p>
+<p><b>GCC 3.4.x</b> on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1056">
+ miscompiles portions of LLVM</a>.</p>
<p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
miscompile LLVM.</p>
+<p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
+ default with ENABLE_OPTIMIZED=1. To work around this, build with
+ "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
+<p><b>GCC 4.1.1</b>: GCC fails to build LLVM with template concept check errors
+ compiling some files. At the time of this writing, GCC mainline (4.2)
+ did not share the problem.</p>
+<p><b>GCC 4.1.1 on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1063">
+ miscompiles portions of LLVM</a> when compiling llvm itself into 64-bit
+ code. LLVM will appear to mostly work but will be buggy, e.g. failing
+ portions of its testsuite.</p>
+<p><b>GCC 4.1.2 on OpenSUSE</b>: Seg faults during libstdc++ build and on x86_64
+platforms compiling md5.c gets a mangled constant.</p>
+<p><b>GNU ld 2.16.X</b>. Some 2.16.X versions of the ld linker will produce very
+long warning messages complaining that some ".gnu.linkonce.t.*" symbol was
+defined in a discarded section. You can safely ignore these messages as they are
+erroneous and the linkage is correct. These messages disappear using ld
+2.17.</p>
</div>
<dt>SRC_ROOT
<dd>
This is the top level directory of the LLVM source tree.
- <p>
+ <br><br>
<dt>OBJ_ROOT
<dd>
This is the top level directory of the LLVM object tree (i.e. the
tree where object files and compiled programs will be placed. It
can be the same as SRC_ROOT).
- <p>
+ <br><br>
<dt>LLVMGCCDIR
<dd>
This is where the LLVM GCC Front End is installed.
<p>
For the pre-built GCC front end binaries, the LLVMGCCDIR is
- <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
+ <tt>llvm-gcc/<i>platform</i>/llvm-gcc</tt>.
</dl>
</div>
<dt><tt>llvm-test-x.y.tar.gz</tt></dt>
<dd>Source release for the LLVM test suite.</dd>
- <dt><tt>cfrontend-x.y.source.tar.gz</tt></dt>
- <dd>Source release of the GCC front end.<br/></dd>
-
- <dt><tt>cfrontend-x.y.sparc-sun-solaris2.8.tar.gz</tt></dt>
- <dd>Binary release of the GCC front end for Solaris/Sparc.
- <br/></dd>
+ <dt><tt>llvm-gcc4-x.y.source.tar.gz</tt></dt>
+ <dd>Source release of the llvm-gcc4 front end. See README.LLVM in the root
+ directory for build instructions.<br/></dd>
- <dt><tt>cfrontend-x.y.i686-redhat-linux-gnu.tar.gz</tt></dt>
- <dd>Binary release of the GCC front end for Linux/x86.<br/></dd>
+ <dt><tt>llvm-gcc4-x.y-platform.tar.gz</tt></dt>
+ <dd>Binary release of the llvm-gcc4 front end for a specific platform.<br/></dd>
- <dt><tt>cfrontend-x.y.i386-unknown-freebsd5.1.tar.gz</tt></dt>
- <dd>Binary release of the GCC front end for FreeBSD/x86.<br/></dd>
-
- <dt><tt>cfrontend-x.y.powerpc-apple-darwin7.8.0.tar.gz</tt></dt>
- <dd>Binary release of the GCC front end for MacOS X/PPC.<br/></dd>
</dl>
+<p>It is also possible to download the sources of the llvm-gcc4 front end from a
+read-only subversion mirror at
+svn://anonsvn.opensource.apple.com/svn/llvm/trunk. </p>
+
</div>
<!-- ======================================================================= -->
<ul>
<li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
- <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
+ <li><tt>cvs -d :pserver:anon@llvm.org:/var/cvs/llvm login</tt>
<li>Hit the return key when prompted for the password.
- <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
+ <li><tt>cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co
llvm</tt>
</ul>
labels:</p>
<ul>
+<li>Release 1.9: <b>RELEASE_19</b></li>
+<li>Release 1.8: <b>RELEASE_18</b></li>
+<li>Release 1.7: <b>RELEASE_17</b></li>
<li>Release 1.6: <b>RELEASE_16</b></li>
<li>Release 1.5: <b>RELEASE_15</b></li>
<li>Release 1.4: <b>RELEASE_14</b></li>
you get it from the CVS repository:</p>
<pre>
cd llvm/projects
- cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-test
+ cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co llvm-test
</pre>
<p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
configured by the LLVM configure script as well as automatically updated when
you run <tt>cvs update</tt>.</p>
-<p>If you would like to get the GCC front end source code, you can also get it
-from the CVS repository:</p>
-
-<pre>
- cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-gcc
-</pre>
-
-<p>Please note that you must follow <a href="CFEBuildInstrs.html">these
-instructions</a> to successfully build the LLVM GCC front-end.</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsubsection">
- <a name="mirrors">LLVM CVS Mirrors</a>
-</div>
-
-<div class="doc_text">
+<p>If you would like to get the GCC front end source code, you can also get it
+and build it yourself. Please follow <a href="CFEBuildInstrs.html">these
+instructions</a> to successfully get and build the LLVM GCC front-end.</p>
-<p>If the main CVS server is overloaded or inaccessible, you can try one of
-these user-hosted mirrors:</p>
-
-<ul>
-<li><a href="http://llvm.x10sys.com/">Mirror hosted by eXtensible Systems
-Inc.</a></li>
-</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_text">
-<p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
-GCC front end from the binary distribution. It is used for building the
-bytecode libraries later used by the GCC front end for linking programs, and its
-location must be specified when the LLVM suite is configured.</p>
+<p>Before configuring and compiling the LLVM suite, you can optionally extract the
+LLVM GCC front end from the binary distribution. It is used for running the
+llvm-test testsuite and for compiling C/C++ programs. Note that you can optionally
+<a href="CFEBuildInstrs.html">build llvm-gcc yourself</a> after building the
+main LLVM repository.</p>
<p>To install the GCC front end, do the following:</p>
<ol>
<li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
- <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
+ <li><tt>gunzip --stdout llvmgcc-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
-</tt></li>
</ol>
-<p>Next, you will need to fix your system header files:</p>
-
-<p><tt>cd cfrontend/<i>platform</i><br>
- ./fixheaders</tt></p>
+<p>Once the binary is uncompressed, you should add a symlink for llvm-gcc and
+llvm-g++ to some directory in your path. When you configure LLVM, it will
+automatically detect llvm-gcc's presence (if it is in your path) enabling its
+use in llvm-test. Note that you can always build or install llvm-gcc at any
+pointer after building the main LLVM repository: just reconfigure llvm and
+llvm-test will pick it up.
+</p>
<p>The binary versions of the GCC front end may not suit all of your needs. For
example, the binary distribution may include an old version of a system header
<p>In cases like these, you may want to try <a
href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
-not for the faint of heart, so be forewarned.</p>
+much easier now than it was in the past.</p>
</div>
<p>The following environment variables are used by the <tt>configure</tt>
script to configure the build system:</p>
-<table>
+<table summary="LLVM configure script environment variables">
<tr><th>Variable</th><th>Purpose</th></tr>
<tr>
<td>CC</td>
dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
option, the LLVM configure script will search for the tcl 8.4 and 8.3
releases.
- <p></p>
+ <br><br>
</dd>
<dt><i>--enable-optimized</i></dt>
<dd>
Enables optimized compilation by default (debugging symbols are removed
and GCC optimization flags are enabled). The default is to use an
unoptimized build (also known as a debug build).
- <p></p>
+ <br><br>
</dd>
<dt><i>--enable-debug-runtime</i></dt>
<dd>
available
on all platforms. The default is dependent on platform, so it is best
to explicitly enable it if you want it.
- <p></p>
+ <br><br>
</dd>
<dt><i>--enable-targets=</i><tt>target-option</tt></dt>
<dd>Controls which targets will be built and linked into llc. The default
separated list of target names that you want available in llc. The target
names use all lower case. The current set of targets is: <br/>
<tt>alpha, ia64, powerpc, skeleton, sparc, x86</tt>.
- <p></p></dd>
+ <br><br></dd>
<dt><i>--enable-doxygen</i></dt>
<dd>Look for the doxygen program and enable construction of doxygen based
documentation from the source code. This is disabled by default because
generating the documentation can take a long time and producess 100s of
megabytes of output.</dd>
+ <dt><i>--with-udis86</i></dt>
+ <dd>LLVM can use external disassembler library for various purposes (now it's
+ used only for examining code produced by JIT). This option will enable usage
+ of <a href="http://udis86.sourceforge.net/">udis86</a> x86 (both 32 and 64
+ bits) disassembler library.</dd>
</dl>
<p>To configure LLVM, follow these steps:</p>
<li>Change directory into the object root directory:
<br>
<tt>cd <i>OBJ_ROOT</i></tt>
- <p>
+ <br><br>
<li>Run the <tt>configure</tt> script located in the LLVM source tree:
<br>
<tt><i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</tt>
- <p>
+ <br><br>
</ol>
</div>
<tt>--enable-optimized</tt> option was used during configuration). The
build system will compile the tools and libraries with debugging
information.
- <p>
+ <br><br>
<dt>Release (Optimized) Builds
<dd>
<tt>gmake</tt> command line. For these builds, the build system will
compile the tools and libraries with GCC optimizations enabled and strip
debugging information from the libraries and executables it generates.
- <p>
+ <br><br>
<dt>Profile Builds
<dd>
<dd>
Removes all files generated by the build. This includes object files,
generated C/C++ files, libraries, and executables.
- <p>
+ <br><br>
<dt><tt>gmake dist-clean</tt>
<dd>
Removes everything that <tt>gmake clean</tt> does, but also removes files
generated by <tt>configure</tt>. It attempts to return the source tree to the
original state in which it was shipped.
- <p>
+ <br><br>
<dt><tt>gmake install</tt>
<dd>
hierarchy
under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
defaults to <tt>/usr/local</tt>.
- <p>
-
+ <br><br>
+
<dt><tt>gmake -C runtime install-bytecode</tt>
<dd>
Assuming you built LLVM into $OBJDIR, when this command is run, it will
install bytecode libraries into the GCC front end's bytecode library
directory. If you need to update your bytecode libraries,
this is the target to use once you've built them.
- <p>
+ <br><br>
</dl>
<p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
<dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
<dd>
Perform a Release (Optimized) build.
- <p>
+ <br><br>
<dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
<dd>
Perform a Release (Optimized) build without assertions enabled.
- <p>
+ <br><br>
<dt><tt>gmake ENABLE_PROFILING=1</tt>
<dd>
Perform a Profiling build.
- <p>
+ <br><br>
<dt><tt>gmake VERBOSE=1</tt>
<dd>
Print what <tt>gmake</tt> is doing on standard output.
- <p>
+ <br><br>
<dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
<dd>Ask each tool invoked by the makefiles to print out what it is doing on
the standard output. This also implies <tt>VERBOSE=1</tt>.
- <p></dd>
+ <br><br></dd>
</dl>
<p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="cross-compile">Cross-Compiling LLVM</a>
+</div>
+
+<div class="doc_text">
+ <p>It is possible to cross-compile LLVM. That is, you can create LLVM
+ executables and libraries for a platform different than the one one which you
+ are compiling. To do this, a few additional steps are
+ required. <sup><a href="#ccn_1">1</a></sup> To cross-compile LLVM, use
+ these instructions:</p>
+ <ol>
+ <li>Configure and build LLVM as a native compiler. You will need
+ just <tt>TableGen</tt> from that build.
+ <ul>
+ <li>If you have <tt>$LLVM_OBJ_ROOT=$LLVM_SRC_ROOT</tt> just execute
+ <tt>make -C utils/TableGen</tt> after configuring.</li>
+ <li>Otherwise you will need to monitor building process and terminate
+ it just after <tt>TableGen</tt> was built.</li>
+ </ul>
+ </li>
+ <li>Copy the TableGen binary to somewhere safe (out of your build tree).
+ </li>
+ <li>Configure LLVM to build with a cross-compiler. To do this, supply the
+ configure script with <tt>--build</tt> and <tt>--host</tt> options that
+ are different. The values of these options must be legal target triples
+ that your GCC compiler supports.</li>
+ <li>Put the saved <tt>TableGen</tt> executable into the
+ into <tt>$LLVM_OBJ_ROOT/{BUILD_TYPE}/bin</tt> directory (e.g. into
+ <tt>.../Release/bin</tt> for a Release build).</li>
+ <li>Build LLVM as usual.</li>
+ </ol>
+ <p>The result of such a build will produce executables that are not executable
+ on your build host (--build option) but can be executed on your compile host
+ (--host option).</p>
+ <p><b>Notes:</b></p>
+ <div class="doc_notes">
+ <ol>
+ <li><a name="ccn_1">Cross-compiling</a> was tested only with Linux as
+ build platform and Windows as host using mingw32 cross-compiler. Other
+ combinations have not been tested.</li>
+ </ol>
+ </div>
+</div>
+
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="objfiles">The Location of LLVM Object Files</a>
<dt>Libraries
<dd><tt><i>OBJ_ROOT</i>/Debug/lib</tt>
</dl>
- <p>
+ <br><br>
<dt>Release Builds
<dd>
<dt>Libraries
<dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
</dl>
- <p>
+ <br><br>
<dt>Profile Builds
<dd>
<dt><tt><b>llvm/lib/Target/</b></tt></dt>
<dd> This directory contains files that describe various target architectures
- for code generation. For example, the <tt>llvm/lib/Target/SparcV9</tt>
- directory holds the Sparc machine description while
+ for code generation. For example, the <tt>llvm/lib/Target/X86</tt>
+ directory holds the X86 machine description while
<tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
<dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
<dl>
- <dt><tt><b>analyze</b></tt></dt>
- <dd><tt>analyze</tt> is used to run a specific
- analysis on an input LLVM bytecode file and print out the results. It is
- primarily useful for debugging analyses, or familiarizing yourself with
- what an analysis does.</dd>
<dt><tt><b>bugpoint</b></tt></dt>
<dd><tt>bugpoint</tt> is used to debug
LLVM assembly.</dd>
<dt><tt><b>llvm-ld</b></tt></dt>
- <dd><tt>llvm-ld</tt> is very similar to gccld and provides a general purpose
- and extensible linker for LLVM. This is the linker invoked by <tt>llvmc</tt>.
- It allows optimization modules to be loaded so that language specific
- optimizations can be applied at link time. This tool is considered
- experimental.</dd>
+ <dd><tt>llvm-ld</tt> is a general purpose and extensible linker for LLVM.
+ This is the linker invoked by <tt>llvmc</tt>. It performsn standard link time
+ optimizations and allows optimization modules to be loaded and run so that
+ language specific optimizations can be applied at link time.</dd>
<dt><tt><b>llvm-link</b></tt></dt>
<dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
the -march=c option).</dd>
<dt><tt><b>llvm-gcc</b></tt></dt>
- <dd><tt>llvm-gcc</tt> is a GCC-based C frontend
- that has been retargeted to emit LLVM code as the machine code output. It
- works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
- -o</tt> options that are typically used. The source code for the
- <tt>llvm-gcc</tt> tool is available as a separate CVS module.
- <blockquote>
- <dl>
- <dt><tt><b>gccas</b></tt></dt>
- <dd>This tool is invoked by the <tt>llvm-gcc</tt> frontend as the
- "assembler" part of the compiler. This tool actually assembles LLVM
- assembly to LLVM bytecode, performs a variety of optimizations, and
- outputs LLVM bytecode. Thus when you invoke
- <tt>llvm-gcc -c x.c -o x.o</tt>, you are causing <tt>gccas</tt> to be
- run, which writes the <tt>x.o</tt> file (which is an LLVM bytecode file
- that can be disassembled or manipulated just like any other bytecode
- file). The command line interface to <tt>gccas</tt> is designed to be
- as close as possible to the <b>system</b> `<tt>as</tt>' utility so that
- the gcc frontend itself did not have to be modified to interface to
- a "weird" assembler.</dd>
-
- <dt><tt><b>gccld</b></tt></dt>
- <dd><tt>gccld</tt> links together several LLVM bytecode files into one
- bytecode file and does some optimization. It is the linker invoked by
- the GCC frontend when multiple .o files need to be linked together.
- Like <tt>gccas</tt>, the command line interface of <tt>gccld</tt> is
- designed to match the system linker, to aid interfacing with the GCC
- frontend.</dd>
- </dl>
- </blockquote>
- </dd>
+ <dd><tt>llvm-gcc</tt> is a GCC-based C frontend that has been retargeted to
+ use LLVM as its backend instead of GCC's RTL backend. It can also emit LLVM
+ byte code or assembly (with the <tt>-emit-llvm</tt> option) instead of the
+ usual machine code output. It works just like any other GCC compiler,
+ taking the typical <tt>-c, -S, -E, -o</tt> options that are typically used.
+ Additionally, the the source code for <tt>llvm-gcc</tt> is available as a
+ separate CVS module.</dd>
<dt><tt><b>opt</b></tt></dt>
- <dd><tt>opt</tt> reads LLVM bytecode, applies a
- series of LLVM to LLVM transformations (which are specified on the command
- line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
- command is a good way to get a list of the program transformations
- available in LLVM.</dd>
+ <dd><tt>opt</tt> reads LLVM bytecode, applies a series of LLVM to LLVM
+ transformations (which are specified on the command line), and then outputs
+ the resultant bytecode. The '<tt>opt --help</tt>' command is a good way to
+ get a list of the program transformations available in LLVM.<br/>
+ <dd><tt>opt</tt> can also be used to run a specific analysis on an input
+ LLVM bytecode file and print out the results. It is primarily useful for
+ debugging analyses, or familiarizing yourself with what an analysis does.</dd>
</dl>
</div>
are code generators for parts of LLVM infrastructure.</p>
<dl>
- <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
- generator -- it builds trees on which it then performs pattern-matching to
- select instructions according to the patterns the user has specified. Burg
- is currently used in the Sparc V9 backend.<p>
-
<dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
that finds differences between code that LLC generates and code that LLI
generates. This is a useful tool if you are debugging one of them,
assuming that the other generates correct output. For the full user
- manual, run <tt>`perldoc codegen-diff'</tt>.<p>
+ manual, run <tt>`perldoc codegen-diff'</tt>.<br><br>
<dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
update your CVS tree, but produce a much cleaner and more organized output
together all the new and updated files and modified files in separate
sections, so you can see at a glance what has changed. If you are at the
top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
- preferred way of updating the tree.<p>
+ preferred way of updating the tree.<br><br>
<dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
syntax-highlighting files which will work with Emacs and XEmacs editors,
providing syntax highlighting support for LLVM assembly files and TableGen
description files. For information on how to use the syntax files, consult
- the <tt>README</tt> file in that directory.<p>
+ the <tt>README</tt> file in that directory.<br><br>
<dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
and outputs all non-generated source files, which is useful if one wishes
to do a lot of development across directories and does not want to
individually find each file. One way to use it is to run, for example:
<tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
- tree.<p>
-
+ tree.<br><br>
+
<dt><tt><b>llvmgrep</b></tt></dt>
<dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
<tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
simply running <tt>makellvm llc</tt> will make a build of the current
directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
- causing a re-linking of LLC.<p>
+ causing a re-linking of LLC.<br><br>
<dt><tt><b>NightlyTest.pl</b></tt> and
<tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
cron script to generate nightly status reports of the functionality of
tools, and the results can be seen by following the appropriate link on
- the <a href="http://llvm.org/">LLVM homepage</a>.<p>
+ the <a href="http://llvm.org/">LLVM homepage</a>.<br><br>
<dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
the tool used to generate register descriptions, instruction set
descriptions, and even assemblers from common TableGen description
- files.<p>
+ files.<br><br>
<dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
syntax-highlighting files which will work with the VIM editor, providing
syntax highlighting support for LLVM assembly files and TableGen
description files. For information on how to use the syntax files, consult
- the <tt>README</tt> file in that directory.<p>
+ the <tt>README</tt> file in that directory.<br><br>
</dl>
</div>
<!-- *********************************************************************** -->
+<div class="doc_text">
+<p>This section gives an example of using LLVM. llvm-gcc3 is now obsolete,
+so we only include instructiosn for llvm-gcc4.
+</p>
+
+<p><b>Note:</b> The <i>gcc4</i> frontend's invocation is <b><i>considerably different</i></b>
+from the previous <i>gcc3</i> frontend. In particular, the <i>gcc4</i> frontend <b><i>does not</i></b>
+create bytecode by default: <i>gcc4</i> produces native code. As the example below illustrates,
+the '--emit-llvm' flag is needed to produce LLVM bytecode output. For <i>makefiles</i> and
+<i>configure</i> scripts, the CFLAGS variable needs '--emit-llvm' to produce bytecode
+output.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="tutorial4">Example with llvm-gcc4</a></div>
+
<div class="doc_text">
<ol>
}
</pre></li>
- <li><p>Next, compile the C file into a LLVM bytecode file:</p>
+ <li><p>Next, compile the C file into a native executable:</p>
+
<p><tt>% llvm-gcc hello.c -o hello</tt></p>
- <p>Note that you should have already built the tools and they have to be
- in your path, at least <tt>gccas</tt> and <tt>gccld</tt>.</p>
+ <p>Note that llvm-gcc works just like GCC by default. The standard -S and
+ -c arguments work as usual (producing a native .s or .o file,
+ respectively). </p>
+
+ <li><p>Next, compile the C file into a LLVM bytecode file:</p>
+ <p><tt>% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc</tt></p>
+
+ <p>The -emit-llvm option can be used with the -S or -c options to emit an
+ LLVM ".ll" or ".bc" file (respectively) for the code. This allows you
+ to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
+ the bytecode file.</p>
- <p>This will create two result files: <tt>hello</tt> and
- <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
- corresponds the the compiled program and the library facilities that it
- required. <tt>hello</tt> is a simple shell script that runs the bytecode
- file with <tt>lli</tt>, making the result directly executable. Note that
- all LLVM optimizations are enabled by default, so there is no need for a
- "-O3" switch.</p></li>
+ <p>Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
+ </p></li>
- <li><p>Run the program. To make sure the program ran, execute one of the
- following commands:</p>
+ <li><p>Run the program in both forms. To run the program, use:</p>
<p><tt>% ./hello</tt></p>
- <p>or</p>
+ <p>and</p>
+
+ <p><tt>% lli hello.bc</tt></p>
- <p><tt>% lli hello.bc</tt></p></li>
+ <p>The second examples shows how to invoke the LLVM JIT, <a
+ href="CommandGuide/html/lli.html">lli</a>.</p></li>
<li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
code:</p>
- <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
+ <p><tt>% llvm-dis < hello.bc | less</tt><br><br></li>
<li><p>Compile the program to native assembly using the LLC code
generator:</p>
<li><p>Execute the native code program:</p>
- <p><tt>% ./hello.native</tt></p></li>
+ <p><tt>% ./hello.native</tt></p>
+
+ <p>Note that using llvm-gcc to compile directly to native code (i.e. when
+ the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
+ </li>
</ol>
</div>
+
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="problems">Common Problems</a>
projects / oota-llvm.git / blobdiff