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* Changed names of libraries to reflect new naming scheme
* Added some more introductory material
* Added a rule of thumb.


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<title>Object Files: Understanding The Result Of LLVM Compilation</title>
<title>Using The LLVM Libraries</title>
<link rel="stylesheet" href="llvm.css" type="text/css">
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<body>
<div class="doc_title">
Object Files: Understanding The Result Of LLVM Compilation
</div>
<div class="doc_title">Using The LLVM Libraries</div>
<ol>
<li><a href="#abstract">Abstract</a></li>
<li><a href="#introduction">Introduction</a></li>
<li><a href="#files">File Contents</a></li>
<li><a href="#descriptions">Library Descriptions</a></li>
<li><a href="#rot">Linkage Rules Of Thumb</a>
<ol>
<li><a href="#always">Always Link vmcore.o, support.a</a>
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<!-- ======================================================================= -->
<div class="doc_section"><a name="abstract">Abstract</a></div>
<div class="doc_text">
<p>This document describes the contents of the many objects files and libraries
that are produced by compiling LLVM. To make use of LLVM this information is
needed in order to understand what files should be linked into your program.
<p>Amongst other things, LLVM is a toolkit for building compilers, linkers,
runtime executives, virtual machines, and other program execution related
tools. In addition to the LLVM tool set, the functionality of LLVM is
available through a set of libraries. To use LLVM as a toolkit for
constructing tools, a developer needs to understand what is contained in the
various libraries, what they depend on, and how to use them. This document
describes the contents of the libraries and how and when to use them.
</p>
</div>
<!-- ======================================================================= -->
<div class="doc_section"> <a name="introduction">Introduction</a></div>
<div class="doc_text">
<p>If you're writing a compiler, virtual machine, or any other utility for
LLVM, you'll need to figure out which of the many .a (archive) and .o
(object) files you will need to link with to be successful. An
understanding of the contents of these files and their inter-relationships
will be useful in coming up with an optimal specification for the objects
and libraries to link with.
</p>
<p>The purpose of this document is to hopefully reduce some of the trial and
error that the author experienced in using LLVM.
</p>
<p>If you're writing a compiler, virtual machine, or any other utility based
on LLVM, you'll need to figure out which of the many libraries files you will
need to link with to be successful. An understanding of the contents of these
files and their inter-relationships will be useful in coming up with an optimal
specification for the libraries to link with. The purpose of this document is
to reduce some of the trial and error that the author experienced in using
LLVM.</p>
<p>LLVM produces two types of libraries: archives (ending in <tt>.a</tt>) and
objects (ending in <tt>.o</tt>). However, both are libraries. Libraries ending
in <tt>.o</tt> are known as re-linked libraries because they contain all the
compilation units of the library linked together as a single <tt>.o</tt> file.
Furthermore, many of the libraries have <em>both</em> forms of library. The
re-linked libraries are used whenever you want to include all symbols from the
library. The archive libraries are used whenever you want to only resolve
outstanding symbols at that point in the link without including everything in
the library. </p>
<p>When linking your tools, you will use the <tt>LLVMLIBS</tt> make variable.
(see the <a href="MakefileGuide.html#LLVMLIBS">Makefile Guide</a> for
details). This variable specifies which LLVM libraries to link into your tool
and the order in which they will be linked. You specify re-linked libraries by
naming the library without a suffix. You specify archive libraries by naming
the library with a <tt>.a</tt> suffix but without the <tt>lib</tt> prefix. The
order in which the libraries appear in the <tt>LLVMLIBS</tt> variable
definition is the order in which they will be linked. Getting this order
correct for your tool can sometimes be challenging.
</div>
<!-- ======================================================================= -->
<div class="doc_section"><a name="files"></a>File Contents</div>
<div class="doc_section"><a name="descriptions"></a>Library Descriptions</div>
<div class="doc_text">
<p>The table below provides a summary of the basic contents of each file.</p>
<table class="doc_table"
style="width:80%; text-align: left; border: 2px solid gray; border-collapse: collapse;">
<tr class="doc_table">
<td colspan="2" class="doc_section">Summary Of LLVM Library And Object Files
</td>
</tr>
<tr class="doc_table">
<td><h2><u>Library</u></h2></td>
<td><h2><u>Description</u></h2></td>
</tr>
<tr class="doc_table">
<td>libipo.a</td>
<td>
An archive of all interprocedural optimizations.
</td>
</tr>
<tr class="doc_table">
<td>libscalaropts.a</td>
<td>
An archive of all scalar optimizations.
</td>
</tr>
<tr class="doc_table">
<td>libtransforms.a</td>
<td>Uncategorized transformations.</td>
</tr>
<tr class="doc_table">
<td>libtarget.a</td>
<td>An archive containing generic code generator support.</td>
</tr>
<tr class="doc_table">
<td>libanalysis.a</td>
<td>An archive containing intraprocedural analyses.</td>
</tr>
<tr class="doc_table">
<td>libdatastructure.a</td>
<td>An archive containing Data Structure Analysis.</td>
</tr>
<tr class="doc_table">
<td>libinstrument.a</td>
<td>Intraprocedural instrumentation and utilities.</td>
</tr>
<tr class="doc_table">
<td>libsparcv9regalloc.a</td>
<td>SparcV9 graph-coloring register allocator.</td>
</tr>
<tr class="doc_table">
<td>libipa.a</td>
<td>An archive containing interprocedural analyses</td>
</tr>
<tr class="doc_table">
<td>libtransformutils.a</td>
<td>Utility functions for transformations.</td>
</tr>
<tr class="doc_table">
<td>libsupport.a</td>
<td>General support utilities</td>
</tr>
<tr class="doc_table">
<td><h2><u>Object File</u></h2></td>
<td><h2><u>Description</u></h2></td>
</tr>
<tr class="doc_table">
<td>support.o</td>
<td>General support utilities</td>
</tr>
<tr class="doc_table">
<td>asmparser.o</td>
<td>Assembler Parser</td>
</tr>
<tr class="doc_table">
<td>bcreader.o</td>
<td>Bytecode Reader</td>
</tr>
<tr class="doc_table">
<td>bcwriter.o</td>
<td>Bytecode Writer</td>
</tr>
<tr class="doc_table">
<td>sched.o</td>
<td>SparcV9 instruction scheduler</td>
</tr>
<tr class="doc_table">
<td>selectiondag.o</td>
<td>Aggressive instruction selector for Directed Acyclic Graphs</td>
</tr>
<tr class="doc_table">
<td>transformutils.o</td>
<td>Utilities for code transformations</td>
</tr>
<tr class="doc_table">
<td>ipa.o</td>
<td>Interprocedural Analyses</td>
</tr>
<tr class="doc_table">
<td>sparcv9select.o</td>
<td>SparcV9 instruction selector</td>
</tr>
<tr class="doc_table">
<td>cwriter.o</td>
<td>"C" Code Writer</td>
</tr>
<tr class="doc_table">
<td>profpaths.o</td>
<td>Path profiling instrumentation</td>
</tr>
<tr class="doc_table">
<td>sparcv9regalloc.o</td>
<td>SparcV9 graph-coloring register allocator</td>
</tr>
<tr class="doc_table">
<td>instrument.o</td>
<td>Intraprocedural instrumentation and utilities.</td>
</tr>
<tr class="doc_table">
<td>datastructure.o</td>
<td>Data Structure Analysis</td>
</tr>
<tr class="doc_table">
<td>codegen.o</td>
<td>Native code generation</td>
</tr>
<tr class="doc_table">
<td>sparcv9livevar.o</td>
<td>SparcV9 Live Variable Analysis</td>
</tr>
<tr class="doc_table">
<td>vmcore.o</td>
<td>Virtual Machine Core</td>
</tr>
<tr class="doc_table">
<td>lli-interpreter.o</td>
<td>Interpreter for LLVM ByteCode</td>
</tr>
<tr class="doc_table">
<td>lli-jit.o</td>
<td>
Just-In-Time Compiler For LLVM ByteCode
</td>
</tr>
<tr class="doc_table">
<td>executionengine.o</td>
<td>Engine for LLI</td>
</tr>
<tr class="doc_table">
<td>debugger.o</td>
<td>Source Level Debugging Support</td>
</tr>
<tr class="doc_table">
<td>analysis.o</td>
<td>General framework for Analysis</td>
</tr>
<tr class="doc_table">
<td>sparcv9.o</td>
<td>SparcV9 backend</td>
</tr>
<tr class="doc_table">
<td>target.o</td>
<td>Generic backend support</td>
</tr>
<tr class="doc_table">
<td>transforms.o</td>
<td>Uncategorized transformations.</td>
</tr>
<tr class="doc_table">
<td>x86.o</td>
<td>Intel x86 backend</td>
</tr>
<tr class="doc_table">
<td>powerpc.o</td>
<td>PowerPC backend</td>
</tr>
<tr class="doc_table">
<td>scalaropts.o</td>
<td>Optimizations For Scalars</td>
</tr>
<tr class="doc_table">
<td>ipo.o</td>
<td>Interprocedural Optimizations</td>
</tr>
<tr class="doc_table">
<td>trace.o</td>
<td>Support For Tracing/Debugging?</td>
</tr>
<tr class="doc_table">
<td>profile_rt.o</td>
<td>Runtime Library For Profiler</td>
</tr>
<tr class="doc_table">
<td>sample.o</td>
<td>Sample Program ?</td>
</tr>
<tr class="doc_table">
<td>stkr_compiler.o</td>
<td>Stacker Language Compiler Library</td>
</tr>
<tr class="doc_table">
<td>stkr_runtime.o</td>
<td>Stacker Language Runtime Library</td>
</tr>
<p>The table below categorizes each library
<table style="text-align:left">
<tr><th>Library</th><th>Forms</th><th>Description</th></tr>
<tr><th colspan=3">Core Libraries</th></tr>
<tr><td>LLVMAsmParser</td><td><tt>.o</tt></td><td>LLVM Assembly Parsing</td></tr>
<tr><td>LLVMBCReader</td><td><tt>.o</tt></td><td>LLVM Bytecode Reading</td></tr>
<tr><td>LLVMBCWriter</td><td><tt>.o</tt></td><td>LLVM Bytecode Writing</td></tr>
<tr><td>LLVMDebugger</td><td><tt>.o</tt></td><td>Source Level Debugging Support</td></tr>
<tr><td>LLVMSupport</td><td><tt>.a .o</tt></td><td>General support utilities</td></tr>
<tr><td>LLVMSystem</td><td><tt>.a .o</tt></td><td>Operating system abstraction</td></tr>
<tr><td>LLVMCore</td><td><tt>.o</tt></td><td>LLVM Core IR</td></tr>
<tr><th colspan=3">Analysis Libraries</th></tr>
<tr><td>LLVMAnalysis</td><td><tt>.a .o</tt></td><td>Various analysis passes.</td></tr>
<tr><td>LLVMDataStructure</td><td><tt>.a .o</tt></td><td>Data structure analysis passes.</td></tr>
<tr><td>LLVMipa</td><td><tt>.a .o</tt></td><td>Inter-procedural analysis passes.</td></tr>
<tr><th colspan=3">Transformation Libraries</th>
<tr><td>LLVMInstrumentation</td><td><tt>.a .o</tt></td><td>Instrumentation passes.</td></tr>
<tr><td>LLVMipo</td><td><tt>.a .o</tt></td><td>All inter-procedural optimization passes.</td></tr>
<tr><td>LLVMScalarOpts</td><td><tt>.a .o</tt></td><td>All scalar optimization passes.</td></tr>
<tr><td>LLVMTransforms</td><td><tt>.a .o</tt></td><td>Uncategorized transformation passes.</td></tr>
<tr><td>LLVMTransformUtils</td><td><tt>.a .o</tt></td><td>Transformation utilities.</td></tr>
<tr><td>LLVMProfilePaths</td><td><tt>.o</tt></td><td>Profile paths for instrumentation.</td></tr>
<tr><th colspan=3">Code Generation Libraries </th></tr>
<tr><td>LLVMCodeGen</td><td><tt>.o</tt></td><td>Native code generation infrastructure</td></tr>
<tr><th colspan=3">Target Libraries</th></tr>
<tr><td>LLVMCBackend</td><td><tt>.o</tt></td><td>'C' language code generator.</td></tr>
<tr><td>LLVMPowerPC</td><td><tt>.o</tt></td><td>PowerPC code generation backend</td></tr>
<tr><td>LLVMSelectionDAG</td><td><tt>.o</tt></td><td>Aggressive instruction selector for Directed Acyclic Graphs.</td></tr>
<tr><td>LLVMSkeleton</td><td><tt>.a .o</tt></td><td>Skeleton for a code generation backend.</td></tr>
<tr><td>LLVMSparcV9</td><td><tt>.o</tt></td><td>Code generation for SparcV9.</td></tr>
<tr><td>LLVMSparcV9RegAlloc</td><td><tt>.a .o</tt></td><td>Graph-coloring register allocator for SparcV9.</td></tr>
<tr><td>LLVMSparcV9InstrSched</td><td><tt>.o</tt></td><td>Instruction scheduling for SparcV9.</td></tr>
<tr><td>LLVMSparcV9LiveVar</td><td><tt>.o</tt></td><td>Live variable analysis SparcV9.</td></tr>
<tr><td>LLVMSparcV9ModuloSched</td><td><tt>.o</tt></td><td>Modulo scheduling for SparcV9.</td></tr>
<tr><td>LLVMTarget</td><td><tt>.a .o</tt></td><td>Generic code generation utilities.</td></tr>
<tr><td>LLVMX86</td><td><tt>.o</tt></td><td>Intel x86 code generation backend</td></tr>
<tr><th colspan=3">Runtime Libraries</th></tr>
<tr><td>LLVMInterpreter</td><td><tt>.o</tt></td><td>Bytecode Interpreter</td></tr>
<tr><td>LLVMJIT</td><td><tt>.o</tt></td><td>Bytecode JIT Compiler</td></tr>
<tr><td>LLVMExecutionEngine</td><td><tt>.o</tt></td><td>Virtual machine engine</td></tr>
<tr><td>LLVMexecve</td><td><tt>.o</tt></td><td>execve(2) replacement for llee</td></tr>
</table>
</div>
<p></p>
<!-- ======================================================================= -->
<div class="doc_section"><a name="rot">Linkage Rules Of Thumb</a></div>
<div class="doc_text">
@ -267,16 +124,21 @@ needed in order to understand what files should be linked into your program.
should link into your programs.</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection"><a name="always">Always Link vmcore.o support.a</a>
</div>
<div class="doc_subsection"><a name="always">Always Link LLVMCore LLVMSupport
LLVMSystem</a></div>
<div class="doc_text">
<p>No matter what you do with LLVM, you'll always need to link with vmcore.o
and support.a.</p>
<p>No matter what you do with LLVM, the last three entries in your linke line
should always be: <tt>LLVMCore LLVMSupport.a LLVMSystem.a</tt>.</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection"><a name="Placeholder">Placeholder</a></div>
<div class="doc_subsection"><a name="onlyone">Never link both archive and
re-linked library</a></div>
<div class="doc_text">
<p>Need more rules of thumb here.</p>
<p>There is never any point to linking both the re-linked (<tt>.o</tt>) and
the archive (<tt>.a</tt>) versions of a library. Since the re-linked version
includes the entire library, the archive version will not resolve any symbols.
You could even end up with link error is you place the archive version before
the re-linked version on the linker's command line.</p>
</div>
<!-- ======================================================================= -->
<hr>