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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Specification for LLVM system code</title>
<title>Getting Started with LLVM System</title>
</head>
<body>
<h1>Specification for LLVM system</h1>
<h1><a name="index">Index</a></h1>
<h1>Getting Started with the LLVM System</h1>
<ul>
<li><a href="#cvs">Checkout LLVM from CVS</a>
<li><a href="#compilerun">Compile and Run</a>
<li><a href="#quickstart">Getting started with LLVM</a>
<ol>
<li><a href="#cvs">Checkout LLVM from CVS</a>
<li><a href="#environment">Set up your environment</a>
<li><a href="#compile">Compiling the Source Code</a>
</ol>
<li><a href="#layout">Program layout</a>
<ol>
<li><a href="#d&d">Depend and Debug directories</a></li>
<li><a href="#cvsdir">CVS directories</a>
<li><a href="#dd">Depend, Debug, &amp; Release directories</a></li>
<li><a href="#include">llvm/include</a>
<li><a href="#lib">llvm/lib</a>
<li><a href="#test">llvm/test</a>
<li><a href="#tools">llvm/tools</a>
</ol>
<li> <a href="#tutorial"> simple example for using tools</li>
<li><a href="#tutorial">An example using the LLVM tool chain</a>
<li><a href="#links">Links</a>
</ul>
<h2><a name="tools">Checkout LLVM from CVS</a></h2>
<p>
<dl>
<dt>cvs root directory:<dd> /home/vadve/vadve/Research/DynOpt/CVSRepository<br>
<dt>project name:<dd> llvm
</dl>
For those who are not familar with cvs, there are two steps you should do:<br>
<ol>
<li>
set CVSROOT. Add the following line into the .cshrc file in your home directory if you are using tcsh or csh:<br>
<i>setenv CVSROOT /home/vadve/vadve/Research/DynOpt/CVSRepository</i>
</li>
<li>
check out. Go to the directory you want to store LLVM, type <br>
<i>cvs checkout llvm</i>
</li>
</ol>
note: the c front-end implementation is not in cvs. If you want to use it, you can use excutable in Chris Lattner's directory<br>
<dd><i>/home/vadve/lattner/cvs/gcc_install/bin/gcc</i><br>
a brief usage of this gcc and other tools are introduced later. To read it now, click <a href="#tutorial">here</a>.
<h2><a name="compilerun">Compile and Run</a></h2>
There is a makefile in each directory. You can simple type <i>gmake</i> in the <b>~/llvm</b> directory to compile all the files or you can type <i>gmake</i> in the certain directory to compile all files and subdirectories in that directory.<br>
You might want to add the the following directory into your path:<br>
<dd><i>llvm/tools/Debug</i><br>
so you can run tools in any directory. If you are using csh or tcsh, add <br>
<dd><i>setenv PATH llvm/tools/Debug:${PATH}</i><br>
at the end of the file .cshrc in your home directory.
</dl>
<h2><a name="layout">Program Layout</a></h2>
Many useful infomation can be obtained from the LLVM doxygen tree available at <a href="http://llvm.cs.uiuc.edu/doxygen/"><i>http://llvm.cs.uiuc.edu/doxygen/ </i><br></a>
The following is a brief introduction to code layout:
<h3><a name="d&d">Depend and Debug directories</a></h3>
Most directories contain these two directories. The depend directory contains dependance files which will be used during complilation. The debug directory contains object files, library files or executables after compilation.
<h3><a name="include">llvm/include</a></h3>
This directory contains common head files supporting the LLVM library. Specific head files which are only used by certain directory are place in that directory instead of here.
<h3><a name="lib">llvm/lib</a></h3>
This directory contains most important files of LLVM system. <br>
<dl compact>
<dt>llvm/lib/transforms/<dd> This directory contains files and directories for transforming one representation to another representation.
<dt>llvm/lib/Target/<dd> This directory contains files and directories for target machine. The files under llvm/lib/Target describe the common property for any target machine. The directory llvm/lib/Target/Sparc describe the sparc machine specification. <br>
<dt>llvm/lib/Analysis/<dd> This directory contains files and directories for doing all kinds of data and control analysis.
<dt>llvm/lib/AsmParser/<dd> This directory contains files and directories for parsing the llvm assemly files.
<dt>llvm/lib/ByteCode/<dd> This directory contains files and directories for reading and write LLVM bytecode.
<dt>llvm/lib/CWrite/<dd> This directory contains files and directories for writing c files as output.
<dt>llvm/lib/CodeGen/<dd> This directory contains files and directories for instruction selection, instruction scheduling and register allocation.
<dt>llvm/lib/Reoptimizer<dd> This directory contains files and directories for all kinds of optimizations, e.g. dead code elimination, Loop Invariant Code Motion, etc.
<dt>llvm/lib/Support/<dd> This directory contains some files and directories supporting the library, e.g. commandline processor and statistic reporter.
<dt>llvm/lib/VMCore/<dd> This directory contains files and directories for implementing the virtual machine instruction set.
</dl>
<h3><a name="test">llvm/test</a></h3>
This directory contains llvm assembly and other files to test the llvm library.
<h3><a name="tools">llvm/tools</a></h3>
<p> The <b>tools</b> directory contains many tools. You can always get help by typing <i>command_name --help </i>. The following is a brief introduction to each tool.
<dl compact>
<dt><i>analyze</i><dd> ???
<dt><i>as</i><dd>llvm .ll -> .bc assembler
<br>The assembler transfroms the human readable assembly to llvm bytecode.
<dt><i>dis</i><dd>llvm .bc -> .ll disassembler
<br>The disassembler transfroms the llvm bytecode to human readable assembly.
<dt><i>extract</i><dd> ???
<dt><i>gccas</i><dd>llvm .ll -> .bc assembler
<br>The assembler transfroms the human readable assembly to llvm bytecode.
<dt><i>gccld</i><dd>many llvm bytecode -> llvm bytecode + optimizations
<br> gccld links many llvm bytecode files into one bytecode file and does some optimization.
<dt><i>link</i><dd>many llvm bytecode -> llvm bytecode
<br> <i>link</i> takes many llvm bytecode files and link them into one llvm bytecode file.
<dt><i>llc</i><dd>llvm bytecode -> SPARC assembly
<br> <i>llc</i> takes a llvm bytecode file and output a SPARC assembly file.
<dt><i>lli</i><dd>llvm interpreter
<br><i>lli</i> reads a llvm bytecode file and execute it.
<dt><i>opt</i><dd>llvm .bc -> .bc modular optimizer
<br> <i>opt</i> reads llvm bytecode and do certain optimization, then output llvm bytecode .
</dl>
<h2><a name="tutorial">tutorial for using tools</h2>
<ul>
<li>create a simple c file:<br>
<pre>
hello.c
int main() {
printf("hello world\n");
return 0;
}
</pre>
</li>
<li>compile the c file into a llvm bytecode file<br>
<i>% alias llvmgcc /home/vadve/lattner/cvs/gcc_install/bin/gcc</i><br>
<i>% llvmgcc hello.c </i><br>
there will be two output files: <b>a.out</b> and <b>a.out.bc</b>. The file <b>a.out</b> is a shell script and <b>a.out.bc</b> is the llvm bytecode. You can run a.out to excute or directly call the interpreter: <br>
% <i>lli a.out.bc</i><br>
<li> dissembler and assembler <br>
read llvm bytecode and output human readable llvm assembly<br>
%<i>dis a.out.bc -o hello.ll</i><br>
read human readable llvm assembly code and output llvm bytecode<br>
%<i>as hello.ll -o hello.bc</i>
</li>
<li> compile to sparc assembly<br>
<i>%llc hello.bc -o hello.s</i>
</li>
</ul>
<h2><a name="links">Links</a></h2>
<ul>
<li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
<li><a href="http://tank.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
</ul>
<hr>
If you have any question, please send an email to <a href="mailto:lattner@uiuc.edu">Lattner Chris Arthur</a> or <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>. <p>
<!--=====================================================================-->
<h2><a name="quickstart">Getting Started with LLVM</a></h2>
<!--=====================================================================-->
<p>This guide is meant to get you up and running with LLVM as quickly as
possible. Once you get the basic system running you can choose an area to
dive into and learn more about. If you get stuck or something is missing
from this document, please email <a
href="mailto:sabre@nondot.org">Chris</a>.</p>
<!------------------------------------------------------------------------->
<h3><a name="tools">Checkout LLVM from CVS</a></h3>
<!------------------------------------------------------------------------->
<p>First step is to get the actual source code. To do this, all you need to
do is check it out from CVS. From your home directory, just enter:</p>
<p><tt>cvs -d /home/vadve/vadve/Research/DynOpt/CVSRepository checkout llvm</tt></p>
<p>This will create an '<tt>llvm</tt>' directory in your home directory and fully
populate it with the source code for LLVM.</p>
<!------------------------------------------------------------------------->
<h3><a name="tools">Set up your environment</a></h3>
<!------------------------------------------------------------------------->
<p>Now that you have the source code available, you should set up your
environment to be able to use the LLVM tools (once compiled) with as little
hassle as possible. To do this, we recommend that you add the following
lines to your <tt>.cshrc</tt> (or the corresponding lines to your
<tt>.profile</tt> if you use a bourne shell derivative):
<pre>
# Make the C frontend easy to use...
alias llvmgcc /home/vadve/lattner/cvs/gcc_install/bin/gcc
# Make the LLVM tools easy to use...
setenv PATH ~/llvm/tools/Debug:${PATH}
</pre>
<p>The C compiler is not included in the CVS tree you just checked out, so
we just point to the cannonical location, and access it with the
<tt>llvmgcc</tt> command. The rest of the <a href="#tools">LLVM tools</a>
will be built into the llvm/tools/Debug directory inside of the sourcebase.
Adding them to your path will make it much easier to use them.</p>
<!------------------------------------------------------------------------->
<h3><a name="compile">Compiling the Source Code</a></h3>
<!------------------------------------------------------------------------->
<p>Every directory in the LLVM source tree includes a Makefile to build it,
and any subdirectories that it contains. These makefiles require that you
use <tt>gmake</tt>, instead of <tt>make</tt> to build them, but can
otherwise be used freely. To build the entire LLVM system, just enter the
top level <tt>llvm</tt> directory and type <tt>gmake</tt>. A few minutes
later you will hopefully have a freshly compiled toolchain waiting for you
in <tt>llvm/tools/Debug</tt>. If you want to look at the libraries that
were compiled, look in <tt>llvm/lib/Debug</tt>.</p>
<!--=====================================================================-->
<h2><a name="layout">Program Layout</a></h2>
<!--=====================================================================-->
<p>One useful source of infomation about the LLVM sourcebase is the LLVM
doxygen documentation, available at <tt><a
href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>. The
following is a brief introduction to code layout:</p>
<!------------------------------------------------------------------------->
<h3><a name="cvsdir">CVS directories</a></h3>
<!------------------------------------------------------------------------->
Every directory checked out of CVS will contain a CVS directory, for the
most part these can just be ignored.
<!------------------------------------------------------------------------->
<h3><a name="ddr">Depend, Debug, &amp; Release directories</a></h3>
<!------------------------------------------------------------------------->
Most source directories contain two directories, Depend and Debug. The
Depend directory contains automatically generated dependance files which are
used during compilation to make sure that source files get rebuilt if a
header file they use is modified. The Debug directory holds the object
files, library files and executables that are used for building a debug
enabled build. The Release directory is created to hold the same files when
the <tt>ENABLE_OPTIMIZED=1</tt> flag is passed to <tt>gmake</tt>, causing an
optimized built to be performed.
<!------------------------------------------------------------------------->
<h3><a name="include">llvm/include</a></h3>
<!------------------------------------------------------------------------->
This directory contains public header files exported from the LLVM
library. The two main subdirectories of this directory are:
<ol>
<li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
specific header files. This directory also has subdirectories for
different portions of llvm: <tt>Analysis</tt>, <tt>CodeGen</tt>,
<tt>Reoptimizer</tt>, <tt>Target</tt>, <tt>Transforms</tt>, etc...
<li><tt>llvm/include/Support</tt> - This directory contains generic
support libraries that are independant of LLVM, but are used by LLVM.
For example, some C++ STL utilities and a Command Line option processing
library.
</ol>
<!------------------------------------------------------------------------->
<h3><a name="lib">llvm/lib</a></h3>
<!------------------------------------------------------------------------->
This directory contains most source files of LLVM system. In LLVM almost all
code exists in libraries, making it very easy to share code among the
different <a href="#tools">tools</a>.<p>
<dl compact>
<dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
source files that implement core classes like Instruction and BasicBlock.
<dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
for the LLVM assembly language parser library.
<dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
and write LLVM bytecode.
<dt><tt>llvm/lib/CWrite/</tt><dd> This directory implements the LLVM to C
converter.
<dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
different program analyses, such as Dominator Information, Call Graphs,
Induction Variables, Interval Identification, Natural Loop Identification,
etc...
<dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
code for the LLVM to LLVM program transformations, such as Aggressive Dead
Code Elimination, Sparse Conditional Constant Propogation, Inlining, Loop
Invarient Code Motion, Dead Global Elimination, Pool Allocation, and many
others...
<dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
describe various target architectures for code generation. For example,
the llvm/lib/Target/Sparc directory holds the Sparc machine
description.<br>
<dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
of the code generator: Instruction Selector, Instruction Scheduling, and
Register Allocation.
<dt><tt>llvm/lib/Reoptimizer/</tt><dd> This directory holds code related
to the runtime reoptimizer framework that is currently under development.
<dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
that corresponds to the header files located in
<tt>llvm/include/Support/</tt>.
</dl>
<!------------------------------------------------------------------------->
<h3><a name="test">llvm/test</a></h3>
<!------------------------------------------------------------------------->
<p>This directory contains regression tests and source code that is used to
test the LLVM infrastructure...</p>
<!------------------------------------------------------------------------->
<h3><a name="tools">llvm/tools</a></h3>
<!------------------------------------------------------------------------->
<p>The <b>tools</b> directory contains the executables built out of the
libraries above, which form the main part of the user interface. You can
always get help for a tool by typing <tt>tool_name --help</tt>. The
following is a brief introduction to the most important tools.</p>
<dl compact>
<dt><tt><b>as</b></tt><dd>The assembler transforms the human readable
llvm assembly to llvm bytecode.<p>
<dt><tt><b>dis</b></tt><dd>The disassembler transforms the llvm bytecode
to human readable llvm assembly. Additionally it can convert LLVM
bytecode to C, which is enabled with the <tt>-c</tt> option.<p>
<dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
can directly execute LLVM bytecode (although very slowly...). In addition
to a simple intepreter, <tt>lli</tt> is also has debugger and tracing
modes (entered by specifying <tt>-debug</tt> or <tt>-trace</tt> on the
command line, respectively).<p>
<dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler,
which translates LLVM bytecode to a SPARC assembly file.<p>
<dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</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>llvmgcc</tt> tool is currently not included in the LLVM cvs tree
because it is quite large and not very interesting.<p>
<ol>
<dt><tt><b>gccas</b></tt><dd> This took is invoked by the
<tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
tool actually assembles its input, performs a variety of optimizations,
and outputs LLVM bytecode. Thus when you invoke <tt>llvmgcc -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 "wierd"
assembler.<p>
<dt><tt><b>gccld</b></tt><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.<p>
</ol>
<dt><tt><b>opt</b></tt><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.<p>
<dt><tt><b>analyze</b></tt><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.<p>
</dl>
<!--=====================================================================-->
<h2><a name="tutorial">An example using the LLVM tool chain</h2>
<!--=====================================================================-->
<ol>
<li>First, create a simple C file, name it 'hello.c':
<pre>
#include &lt;stdio.h&gt;
int main() {
printf("hello world\n");
return 0;
}
</pre>
<li>Next, compile the C file into a LLVM bytecode file:<p>
<tt>% llvmgcc hello.c -o hello</tt><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.<p>
<li>Run the program. To make sure the program ran, execute one of the
following commands:<p>
<tt>% ./hello</tt><p>
or<p>
<tt>% lli hello.bc</tt><p>
<li>Use the <tt>dis</tt> utility to take a look at the LLVM assembly
code:<p>
<tt>% dis < hello.bc | less</tt><p>
<li>Compile the program to native Sparc assembly using the code
generator:<p>
<tt>% llc hello.bc -o hello.s</tt><p>
<li>Assemble the native sparc assemble file into a program:<p>
<tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt><p>
<li>Execute the native sparc program:<p>
<tt>% ./hello.sparc</tt><p>
</ol>
<!--=====================================================================-->
<h2><a name="links">Links</a></h2>
<!--=====================================================================-->
<p>This document is just an <b>introduction</b> to how to use LLVM to do
some simple things... there are many more interesting and complicated things
that you can do that aren't documented here (but we'll gladly accept a patch
if you want to write something up!). For more information about LLVM, check
out:</p>
<ul>
<li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
<li><a href="http://tank.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
</ul>
<hr>
If you have any questions or run into any snags (or you have any
additions...), please send an email to <a
href="mailto:sabre@nondot.org">Chris Lattner</a> or <a
href="mailto:gshi1@uiuc.edu">Guochun Shi</a>. <p>
<!-- Created: Mon Jul 1 02:29:02 CDT 2002 -->
<!-- hhmts start -->
Last modified: Wed Jul 17 17:55:16 CDT 2002
Last modified: Wed Jul 24 14:43:12 CDT 2002
<!-- hhmts end -->
</body>
</html>