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| <title>The LLVM Compiler Driver (llvmc)</title> | |
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| <meta name="author" content="Reid Spencer"> | |
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| content="A description of the use and design of the LLVM Compiler Driver."> | |
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| <div class="doc_title">The LLVM Compiler Driver (llvmc)</div> | |
| <p class="doc_warning">NOTE: This document is a work in progress!</p> | |
| <ol> | |
| <li><a href="#abstract">Abstract</a></li> | |
| <li><a href="#introduction">Introduction</a> | |
| <ol> | |
| <li><a href="#purpose">Purpose</a></li> | |
| <li><a href="#operation">Operation</a></li> | |
| <li><a href="#phases">Phases</a></li> | |
| <li><a href="#actions">Actions</a></li> | |
| </ol> | |
| </li> | |
| <li><a href="#configuration">Configuration</a> | |
| <ol> | |
| <li><a href="#overview">Overview</a></li> | |
| <li><a href="#filetypes">Configuration Files</a></li> | |
| <li><a href="#syntax">Syntax</a></li> | |
| <li><a href="#substitutions">Substitutions</a></li> | |
| <li><a href="#sample">Sample Config File</a></li> | |
| </ol> | |
| <li><a href="#glossary">Glossary</a> | |
| </ol> | |
| <div class="doc_author"> | |
| <p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a> | |
| </p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="abstract">Abstract</a></div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>This document describes the requirements, design, and configuration of the | |
| LLVM compiler driver, <tt>llvmc</tt>. The compiler driver knows about LLVM's | |
| tool set and can be configured to know about a variety of compilers for | |
| source languages. It uses this knowledge to execute the tools necessary | |
| to accomplish general compilation, optimization, and linking tasks. The main | |
| purpose of <tt>llvmc</tt> is to provide a simple and consistent interface to | |
| all compilation tasks. This reduces the burden on the end user who can just | |
| learn to use <tt>llvmc</tt> instead of the entire LLVM tool set and all the | |
| source language compilers compatible with LLVM.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> <a name="introduction">Introduction</a></div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>The <tt>llvmc</tt> <a href="#def_tool">tool</a> is a configurable compiler | |
| <a href="#def_driver">driver</a>. As such, it isn't a compiler, optimizer, | |
| or a linker itself but it drives (invokes) other software that perform those | |
| tasks. If you are familiar with the GNU Compiler Collection's <tt>gcc</tt> | |
| tool, <tt>llvmc</tt> is very similar.</p> | |
| <p>The following introductory sections will help you understand why this tool | |
| is necessary and what it does.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="purpose">Purpose</a></div> | |
| <div class="doc_text"> | |
| <p><tt>llvmc</tt> was invented to make compilation of user programs with | |
| LLVM-based tools easier. To accomplish this, <tt>llvmc</tt> strives to:</p> | |
| <ul> | |
| <li>Be the single point of access to most of the LLVM tool set.</li> | |
| <li>Hide the complexities of the LLVM tools through a single interface.</li> | |
| <li>Provide a consistent interface for compiling all languages.</li> | |
| </ul> | |
| <p>Additionally, <tt>llvmc</tt> makes it easier to write a compiler for use | |
| with LLVM, because it:</p> | |
| <ul> | |
| <li>Makes integration of existing non-LLVM tools simple.</li> | |
| <li>Extends the capabilities of minimal compiler tools by optimizing their | |
| output.</li> | |
| <li>Reduces the number of interfaces a compiler writer must know about | |
| before a working compiler can be completed (essentially only the VMCore | |
| interfaces need to be understood).</li> | |
| <li>Supports source language translator invocation via both dynamically | |
| loadable shared objects and invocation of an executable.</li> | |
| </ul> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="operation">Operation</a></div> | |
| <div class="doc_text"> | |
| <p>At a high level, <tt>llvmc</tt> operation is very simple. The basic action | |
| taken by <tt>llvmc</tt> is to simply invoke some tool or set of tools to fill | |
| the user's request for compilation. Every execution of <tt>llvmc</tt>takes the | |
| following sequence of steps:</p> | |
| <dl> | |
| <dt><b>Collect Command Line Options</b></dt> | |
| <dd>The command line options provide the marching orders to <tt>llvmc</tt> | |
| on what actions it should perform. This is the request the user is making | |
| of <tt>llvmc</tt> and it is interpreted first. See the <tt>llvmc</tt> | |
| <a href="CommandGuide/html/llvmc.html">manual page</a> for details on the | |
| options.</dd> | |
| <dt><b>Read Configuration Files</b></dt> | |
| <dd>Based on the options and the suffixes of the filenames presented, a set | |
| of configuration files are read to configure the actions <tt>llvmc</tt> will | |
| take. Configuration files are provided by either LLVM or the | |
| compiler tools that <tt>llvmc</tt> invokes. These files determine what | |
| actions <tt>llvmc</tt> will take in response to the user's request. See | |
| the section on <a href="#configuration">configuration</a> for more details. | |
| </dd> | |
| <dt><b>Determine Phases To Execute</b></dt> | |
| <dd>Based on the command line options and configuration files, | |
| <tt>llvmc</tt> determines the compilation <a href="#phases">phases</a> that | |
| must be executed by the user's request. This is the primary work of | |
| <tt>llvmc</tt>.</dd> | |
| <dt><b>Determine Actions To Execute</b></dt> | |
| <dd>Each <a href="#phases">phase</a> to be executed can result in the | |
| invocation of one or more <a href="#actions">actions</a>. An action is | |
| either a whole program or a function in a dynamically linked shared library. | |
| In this step, <tt>llvmc</tt> determines the sequence of actions that must be | |
| executed. Actions will always be executed in a deterministic order.</dd> | |
| <dt><b>Execute Actions</b></dt> | |
| <dd>The <a href="#actions">actions</a> necessary to support the user's | |
| original request are executed sequentially and deterministically. All | |
| actions result in either the invocation of a whole program to perform the | |
| action or the loading of a dynamically linkable shared library and invocation | |
| of a standard interface function within that library.</dd> | |
| <dt><b>Termination</b></dt> | |
| <dd>If any action fails (returns a non-zero result code), <tt>llvmc</tt> | |
| also fails and returns the result code from the failing action. If | |
| everything succeeds, <tt>llvmc</tt> will return a zero result code.</dd> | |
| </dl> | |
| <p><tt>llvmc</tt>'s operation must be simple, regular and predictable. | |
| Developers need to be able to rely on it to take a consistent approach to | |
| compilation. For example, the invocation:</p> | |
| <code> | |
| llvmc -O2 x.c y.c z.c -o xyz</code> | |
| <p>must produce <i>exactly</i> the same results as:</p> | |
| <pre><tt> | |
| llvmc -O2 x.c -o x.o | |
| llvmc -O2 y.c -o y.o | |
| llvmc -O2 z.c -o z.o | |
| llvmc -O2 x.o y.o z.o -o xyz</tt></pre> | |
| <p>To accomplish this, <tt>llvmc</tt> uses a very simple goal oriented | |
| procedure to do its work. The overall goal is to produce a functioning | |
| executable. To accomplish this, <tt>llvmc</tt> always attempts to execute a | |
| series of compilation <a href="#def_phase">phases</a> in the same sequence. | |
| However, the user's options to <tt>llvmc</tt> can cause the sequence of phases | |
| to start in the middle or finish early.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="phases"></a>Phases </div> | |
| <div class="doc_text"> | |
| <p><tt>llvmc</tt> breaks every compilation task into the following five | |
| distinct phases:</p> | |
| <dl><dt><b>Preprocessing</b></dt><dd>Not all languages support preprocessing; | |
| but for those that do, this phase can be invoked. This phase is for | |
| languages that provide combining, filtering, or otherwise altering with the | |
| source language input before the translator parses it. Although C and C++ | |
| are the most common users of this phase, other languages may provide their | |
| own preprocessor (whether its the C pre-processor or not).</dd> | |
| </dl> | |
| <dl><dt><b>Translation</b></dt><dd>The translation phase converts the source | |
| language input into something that LLVM can interpret and use for | |
| downstream phases. The translation is essentially from "non-LLVM form" to | |
| "LLVM form".</dd> | |
| </dl> | |
| <dl><dt><b>Optimization</b></dt><dd>Once an LLVM Module has been obtained from | |
| the translation phase, the program enters the optimization phase. This phase | |
| attempts to optimize all of the input provided on the command line according | |
| to the options provided.</dd> | |
| </dl> | |
| <dl><dt><b>Linking</b></dt><dd>The inputs are combined to form a complete | |
| program.</dd> | |
| </dl> | |
| <p>The following table shows the inputs, outputs, and command line options | |
| applicable to each phase.</p> | |
| <table> | |
| <tr> | |
| <th style="width: 10%">Phase</th> | |
| <th style="width: 25%">Inputs</th> | |
| <th style="width: 25%">Outputs</th> | |
| <th style="width: 40%">Options</th> | |
| </tr> | |
| <tr><td><b>Preprocessing</b></td> | |
| <td class="td_left"><ul><li>Source Language File</li></ul></td> | |
| <td class="td_left"><ul><li>Source Language File</li></ul></td> | |
| <td class="td_left"><dl> | |
| <dt><tt>-E</tt></dt> | |
| <dd>Stops the compilation after preprocessing</dd> | |
| </dl></td> | |
| </tr> | |
| <tr> | |
| <td><b>Translation</b></td> | |
| <td class="td_left"><ul> | |
| <li>Source Language File</li> | |
| </ul></td> | |
| <td class="td_left"><ul> | |
| <li>LLVM Assembly</li> | |
| <li>LLVM Bytecode</li> | |
| <li>LLVM C++ IR</li> | |
| </ul></td> | |
| <td class="td_left"><dl> | |
| <dt><tt>-c</tt></dt> | |
| <dd>Stops the compilation after translation so that optimization and | |
| linking are not done.</dd> | |
| <dt><tt>-S</tt></dt> | |
| <dd>Stops the compilation before object code is written so that only | |
| assembly code remains.</dd> | |
| </dl></td> | |
| </tr> | |
| <tr> | |
| <td><b>Optimization</b></td> | |
| <td class="td_left"><ul> | |
| <li>LLVM Assembly</li> | |
| <li>LLVM Bytecode</li> | |
| </ul></td> | |
| <td class="td_left"><ul> | |
| <li>LLVM Bytecode</li> | |
| </ul></td> | |
| <td class="td_left"><dl> | |
| <dt><tt>-Ox</tt> | |
| <dd>This group of options controls the amount of optimization | |
| performed.</dd> | |
| </dl></td> | |
| </tr> | |
| <tr> | |
| <td><b>Linking</b></td> | |
| <td class="td_left"><ul> | |
| <li>LLVM Bytecode</li> | |
| <li>Native Object Code</li> | |
| <li>LLVM Library</li> | |
| <li>Native Library</li> | |
| </ul></td> | |
| <td class="td_left"><ul> | |
| <li>LLVM Bytecode Executable</li> | |
| <li>Native Executable</li> | |
| </ul></td> | |
| <td class="td_left"><dl> | |
| <dt><tt>-L</tt></dt><dd>Specifies a path for library search.</dd> | |
| <dt><tt>-l</tt></dt><dd>Specifies a library to link in.</dd> | |
| </dl></td> | |
| </tr> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="actions"></a>Actions</div> | |
| <div class="doc_text"> | |
| <p>An action, with regard to <tt>llvmc</tt> is a basic operation that it takes | |
| in order to fulfill the user's request. Each phase of compilation will invoke | |
| zero or more actions in order to accomplish that phase.</p> | |
| <p>Actions come in two forms:</p> | |
| <ul> | |
| <li>Invokable Executables</li> | |
| <li>Functions in a shared library</li> | |
| </ul> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"><a name="configuration">Configuration</a></div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>This section of the document describes the configuration files used by | |
| <tt>llvmc</tt>. Configuration information is relatively static for a | |
| given release of LLVM and a compiler tool. However, the details may | |
| change from release to release of either. Users are encouraged to simply use | |
| the various options of the <tt>llvmc</tt> command and ignore the configuration | |
| of the tool. These configuration files are for compiler writers and LLVM | |
| developers. Those wishing to simply use <tt>llvmc</tt> don't need to understand | |
| this section but it may be instructive on how the tool works.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="overview"></a>Overview</div> | |
| <div class="doc_text"> | |
| <p><tt>llvmc</tt> is highly configurable both on the command line and in | |
| configuration files. The options it understands are generic, consistent and | |
| simple by design. Furthermore, the <tt>llvmc</tt> options apply to the | |
| compilation of any LLVM enabled programming language. To be enabled as a | |
| supported source language compiler, a compiler writer must provide a | |
| configuration file that tells <tt>llvmc</tt> how to invoke the compiler | |
| and what its capabilities are. The purpose of the configuration files then | |
| is to allow compiler writers to specify to <tt>llvmc</tt> how the compiler | |
| should be invoked. Users may but are not advised to alter the compiler's | |
| <tt>llvmc</tt> configuration.</p> | |
| <p>Because <tt>llvmc</tt> just invokes other programs, it must deal with the | |
| available command line options for those programs regardless of whether they | |
| were written for LLVM or not. Furthermore, not all compiler tools will | |
| have the same capabilities. Some compiler tools will simply generate LLVM assembly | |
| code, others will be able to generate fully optimized byte code. In general, | |
| <tt>llvmc</tt> doesn't make any assumptions about the capabilities or command | |
| line options of a sub-tool. It simply uses the details found in the | |
| configuration files and leaves it to the compiler writer to specify the | |
| configuration correctly.</p> | |
| <p>This approach means that new compiler tools can be up and working very | |
| quickly. As a first cut, a tool can simply compile its source to raw | |
| (unoptimized) bytecode or LLVM assembly and <tt>llvmc</tt> can be configured | |
| to pick up the slack (translate LLVM assembly to bytecode, optimize the | |
| bytecode, generate native assembly, link, etc.). In fact, the compiler tools | |
| need not use any LLVM libraries, and it could be written in any language | |
| (instead of C++). The configuration data will allow the full range of | |
| optimization, assembly, and linking capabilities that LLVM provides to be added | |
| to these kinds of tools. Enabling the rapid development of front-ends is one | |
| of the primary goals of <tt>llvmc</tt>.</p> | |
| <p>As a compiler tool matures, it may utilize the LLVM libraries and tools | |
| to more efficiently produce optimized bytecode directly in a single compilation | |
| and optimization program. In these cases, multiple tools would not be needed | |
| and the configuration data for the compiler would change.</p> | |
| <p>Configuring <tt>llvmc</tt> to the needs and capabilities of a source language | |
| compiler is relatively straight-forward. A compiler writer must provide a | |
| definition of what to do for each of the five compilation phases for each of | |
| the optimization levels. The specification consists simply of prototypical | |
| command lines into which <tt>llvmc</tt> can substitute command line | |
| arguments and file names. Note that any given phase can be completely blank if | |
| the source language's compiler combines multiple phases into a single program. | |
| For example, quite often pre-processing, translation, and optimization are | |
| combined into a single program. The specification for such a compiler would have | |
| blank entries for pre-processing and translation but a full command line for | |
| optimization.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="filetypes">Configuration Files</a></div> | |
| <div class="doc_subsubsection"><a name="filecontents">File Contents</a></div> | |
| <div class="doc_text"> | |
| <p>Each configuration file provides the details for a single source language | |
| that is to be compiled. This configuration information tells <tt>llvmc</tt> | |
| how to invoke the language's pre-processor, translator, optimizer, assembler | |
| and linker. Note that a given source language needn't provide all these tools | |
| as many of them exist in llvm currently.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsubsection"><a name="dirsearch">Directory Search</a></div> | |
| <div class="doc_text"> | |
| <p><tt>llvmc</tt> always looks for files of a specific name. It uses the | |
| first file with the name its looking for by searching directories in the | |
| following order:<br/> | |
| <ol> | |
| <li>Any directory specified by the <tt>-config-dir</tt> option will be | |
| checked first.</li> | |
| <li>If the environment variable LLVM_CONFIG_DIR is set, and it contains | |
| the name of a valid directory, that directory will be searched next.</li> | |
| <li>If the user's home directory (typically <tt>/home/user</tt> contains | |
| a sub-directory named <tt>.llvm</tt> and that directory contains a | |
| sub-directory named <tt>etc</tt> then that directory will be tried | |
| next.</li> | |
| <li>If the LLVM installation directory (typically <tt>/usr/local/llvm</tt> | |
| contains a sub-directory named <tt>etc</tt> then that directory will be | |
| tried last.</li> | |
| <li>A standard "system" directory will be searched next. This is typically | |
| <tt>/etc/llvm</tt> on UNIX™ and <tt>C:\WINNT</tt> on Microsoft | |
| Windows™.</li> | |
| <li>If the configuration file sought still can't be found, <tt>llvmc</tt> | |
| will print an error message and exit.</li> | |
| </ol> | |
| <p>The first file found in this search will be used. Other files with the | |
| same name will be ignored even if they exist in one of the subsequent search | |
| locations.</p> | |
| </div> | |
| <div class="doc_subsubsection"><a name="filenames">File Names</a></div> | |
| <div class="doc_text"> | |
| <p>In the directories searched, each configuration file is given a specific | |
| name to foster faster lookup (so llvmc doesn't have to do directory searches). | |
| The name of a given language specific configuration file is simply the same | |
| as the suffix used to identify files containing source in that language. | |
| For example, a configuration file for C++ source might be named | |
| <tt>cpp</tt>, <tt>C</tt>, or <tt>cxx</tt>. For languages that support multiple | |
| file suffixes, multiple (probably identical) files (or symbolic links) will | |
| need to be provided.</p> | |
| </div> | |
| <div class="doc_subsubsection"><a name="whatgetsread">What Gets Read</a></div> | |
| <div class="doc_text"> | |
| <p>Which configuration files are read depends on the command line options and | |
| the suffixes of the file names provided on <tt>llvmc</tt>'s command line. Note | |
| that the <tt>-x LANGUAGE</tt> option alters the language that <tt>llvmc</tt> | |
| uses for the subsequent files on the command line. Only the configuration | |
| files actually needed to complete <tt>llvmc</tt>'s task are read. Other | |
| language specific files will be ignored.</p> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="syntax"></a>Syntax</div> | |
| <div class="doc_text"> | |
| <p>The syntax of the configuration files is very simple and somewhat | |
| compatible with Java's property files. Here are the syntax rules:</p> | |
| <ul> | |
| <li>The file encoding is ASCII.</li> | |
| <li>The file is line oriented. There should be one configuration definition | |
| per line. Lines are terminated by the newline (0x0A) and/or carriage return | |
| characters (0x0D)</li> | |
| <li>A backslash (<tt>\</tt>) before a newline causes the newline to be | |
| ignored. This is useful for line continuation of long definitions. A | |
| backslash anywhere else is recognized as a backslash.</li> | |
| <li>A configuration item consists of a name, an <tt>=</tt> and a value.</li> | |
| <li>A name consists of a sequence of identifiers separated by period.</li> | |
| <li>An identifier consists of specific keywords made up of only lower case | |
| and upper case letters (e.g. <tt>lang.name</tt>).</li> | |
| <li>Values come in four flavors: booleans, integers, commands and | |
| strings.</li> | |
| <li>Valid "false" boolean values are <tt>false False FALSE no No NO | |
| off Off</tt> and <tt>OFF</tt>.</li> | |
| <li>Valid "true" boolean values are <tt>true True TRUE yes Yes YES | |
| on On</tt> and <tt>ON</tt>.</li> | |
| <li>Integers are simply sequences of digits.</li> | |
| <li>Commands start with a program name and are followed by a sequence of | |
| words that are passed to that program as command line arguments. Program | |
| arguments that begin and end with the <tt>%</tt> sign will have their value | |
| substituted. Program names beginning with <tt>/</tt> are considered to be | |
| absolute. Otherwise the <tt>PATH</tt> will be applied to find the program to | |
| execute.</li> | |
| <li>Strings are composed of multiple sequences of characters from the | |
| character class <tt>[-A-Za-z0-9_:%+/\\|,]</tt> separated by white | |
| space.</li> | |
| <li>White space on a line is folded. Multiple blanks or tabs will be | |
| reduced to a single blank.</li> | |
| <li>White space before the configuration item's name is ignored.</li> | |
| <li>White space on either side of the <tt>=</tt> is ignored.</li> | |
| <li>White space in a string value is used to separate the individual | |
| components of the string value but otherwise ignored.</li> | |
| <li>Comments are introduced by the <tt>#</tt> character. Everything after a | |
| <tt>#</tt> and before the end of line is ignored.</li> | |
| </ul> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="items">Configuration Items</a></div> | |
| <div class="doc_text"> | |
| <p>The table below provides definitions of the allowed configuration items | |
| that may appear in a configuration file. Every item has a default value and | |
| does not need to appear in the configuration file. Missing items will have the | |
| default value. Each identifier may appear as all lower case, first letter | |
| capitalized or all upper case.</p> | |
| <table> | |
| <tbody> | |
| <tr> | |
| <th>Name</th> | |
| <th>Value Type</th> | |
| <th>Description</th> | |
| <th>Default</th> | |
| </tr> | |
| <tr><td colspan="4"><h4>LLVMC ITEMS</h4></td></tr> | |
| <tr> | |
| <td><b>version</b></td> | |
| <td>string</td> | |
| <td class="td_left">Provides the version string for the contents of this | |
| configuration file. What is accepted as a legal configuration file | |
| will change over time and this item tells <tt>llvmc</tt> which version | |
| should be expected.</td> | |
| <td><i>b</i></td> | |
| </tr> | |
| <tr><td colspan="4"><h4>LANG ITEMS</h4></td></tr> | |
| <tr> | |
| <td><b>lang.name</b></td> | |
| <td>string</td> | |
| <td class="td_left">Provides the common name for a language definition. | |
| For example "C++", "Pascal", "FORTRAN", etc.</td> | |
| <td><i>blank</i></td> | |
| </tr> | |
| <tr> | |
| <td><b>lang.opt1</b></td> | |
| <td>string</td> | |
| <td class="td_left">Specifies the parameters to give the optimizer when | |
| <tt>-O1</tt> is specified on the <tt>llvmc</tt> command line.</td> | |
| <td><tt>-simplifycfg -instcombine -mem2reg</tt></td> | |
| </tr> | |
| <tr> | |
| <td><b>lang.opt2</b></td> | |
| <td>string</td> | |
| <td class="td_left">Specifies the parameters to give the optimizer when | |
| <tt>-O2</tt> is specified on the <tt>llvmc</tt> command line.</td> | |
| <td><i>TBD</i></td> | |
| </tr> | |
| <tr> | |
| <td><b>lang.opt3</b></td> | |
| <td>string</td> | |
| <td class="td_left">Specifies the parameters to give the optimizer when | |
| <tt>-O3</tt> is specified on the <tt>llvmc</tt> command line.</td> | |
| <td><i>TBD</i></td> | |
| </tr> | |
| <tr> | |
| <td><b>lang.opt4</b></td> | |
| <td>string</td> | |
| <td class="td_left">Specifies the parameters to give the optimizer when | |
| <tt>-O4</tt> is specified on the <tt>llvmc</tt> command line.</td> | |
| <td><i>TBD</i></td> | |
| </tr> | |
| <tr> | |
| <td><b>lang.opt5</b></td> | |
| <td>string</td> | |
| <td class="td_left">Specifies the parameters to give the optimizer when | |
| <tt>-O5</tt> is specified on the <tt>llvmc</tt> command line.</td> | |
| <td><i>TBD</i></td> | |
| </tr> | |
| <tr><td colspan="4"><h4>PREPROCESSOR ITEMS</h4></td></tr> | |
| <tr> | |
| <td><b>preprocessor.command</b></td> | |
| <td>command</td> | |
| <td class="td_left">This provides the command prototype that will be used | |
| to run the preprocessor. This is generally only used with the | |
| <tt>-E</tt> option.</td> | |
| <td><blank></td> | |
| </tr> | |
| <tr> | |
| <td><b>preprocessor.required</b></td> | |
| <td>boolean</td> | |
| <td class="td_left">This item specifies whether the pre-processing phase | |
| is required by the language. If the value is true, then the | |
| <tt>preprocessor.command</tt> value must not be blank. With this option, | |
| <tt>llvmc</tt> will always run the preprocessor as it assumes that the | |
| translation and optimization phases don't know how to pre-process their | |
| input.</td> | |
| <td>false</td> | |
| </tr> | |
| <tr><td colspan="4"><h4>TRANSLATOR ITEMS</h4></td></tr> | |
| <tr> | |
| <td><b>translator.command</b></td> | |
| <td>command</td> | |
| <td class="td_left">This provides the command prototype that will be used | |
| to run the translator. Valid substitutions are <tt>%in%</tt> for the | |
| input file and <tt>%out%</tt> for the output file.</td> | |
| <td><blank></td> | |
| </tr> | |
| <tr> | |
| <td><b>translator.output</b></td> | |
| <td><tt>bytecode</tt> or <tt>assembly</tt></td> | |
| <td class="td_left">This item specifies the kind of output the language's | |
| translator generates.</td> | |
| <td><tt>bytecode</tt></td> | |
| </tr> | |
| <tr> | |
| <td><b>translator.preprocesses</b></td> | |
| <td>boolean</td> | |
| <td class="td_left">Indicates that the translator also preprocesses. If | |
| this is true, then <tt>llvmc</tt> will skip the pre-processing phase | |
| whenever the final phase is not pre-processing.</td> | |
| <td><tt>false</tt></td> | |
| </tr> | |
| <tr><td colspan="4"><h4>OPTIMIZER ITEMS</h4></td></tr> | |
| <tr> | |
| <td><b>optimizer.command</b></td> | |
| <td>command</td> | |
| <td class="td_left">This provides the command prototype that will be used | |
| to run the optimizer. Valid substitutions are <tt>%in%</tt> for the | |
| input file and <tt>%out%</tt> for the output file.</td> | |
| <td><blank></td> | |
| </tr> | |
| <tr> | |
| <td><b>optimizer.output</b></td> | |
| <td><tt>bytecode</tt> or <tt>assembly</tt></td> | |
| <td class="td_left">This item specifies the kind of output the language's | |
| optimizer generates. Valid values are "assembly" and "bytecode"</td> | |
| <td><tt>bytecode</tt></td> | |
| </tr> | |
| <tr> | |
| <td><b>optimizer.preprocesses</b></td> | |
| <td>boolean</td> | |
| <td class="td_left">Indicates that the optimizer also preprocesses. If | |
| this is true, then <tt>llvmc</tt> will skip the pre-processing phase | |
| whenever the final phase is optimization or later.</td> | |
| <td><tt>false</tt></td> | |
| </tr> | |
| <tr> | |
| <td><b>optimizer.translates</b></td> | |
| <td>boolean</td> | |
| <td class="td_left">Indicates that the optimizer also translates. If | |
| this is true, then <tt>llvmc</tt> will skip the translation phase | |
| whenever the final phase is optimization or later.</td> | |
| <td><tt>false</tt></td> | |
| </tr> | |
| <tr><td colspan="4"><h4>ASSEMBLER ITEMS</h4></td></tr> | |
| <tr> | |
| <td><b>assembler.command</b></td> | |
| <td>command</td> | |
| <td class="td_left">This provides the command prototype that will be used | |
| to run the assembler. Valid substitutions are <tt>%in%</tt> for the | |
| input file and <tt>%out%</tt> for the output file.</td> | |
| <td><blank></td> | |
| </tr> | |
| </tbody> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="substitutions">Substitutions</a></div> | |
| <div class="doc_text"> | |
| <p>On any configuration item that ends in <tt>command</tt>, you must | |
| specify substitution tokens. Substitution tokens begin and end with a percent | |
| sign (<tt>%</tt>) and are replaced by the corresponding text. Any substitution | |
| token may be given on any <tt>command</tt> line but some are more useful than | |
| others. In particular each command <em>should</em> have both an <tt>%in%</tt> | |
| and an <tt>%out%</tt> substitution. The table below provides definitions of | |
| each of the allowed substitution tokens.</p> | |
| <table> | |
| <tbody> | |
| <tr> | |
| <th>Substitution Token</th> | |
| <th>Replacement Description</th> | |
| </tr> | |
| <tr> | |
| <td><tt>%args%</tt></td> | |
| <td class="td_left">Replaced with all the tool-specific arguments given | |
| to <tt>llvmc</tt> via the <tt>-T</tt> set of options. This just allows | |
| you to place these arguments in the correct place on the command line. | |
| If the <tt>%args%</tt> option does not appear on your command line, | |
| then you are explicitly disallowing the <tt>-T</tt> option for your | |
| tool. | |
| </td> | |
| <tr> | |
| <td><tt>%force%</tt></td> | |
| <td class="td_left">Replaced with the <tt>-f</tt> option if it was | |
| specified on the <tt>llvmc</tt> command line. This is intended to tell | |
| the compiler tool to force the overwrite of output files. | |
| </td> | |
| </tr> | |
| <tr> | |
| <td><tt>%in%</tt></td> | |
| <td class="td_left">Replaced with the full path of the input file. You | |
| needn't worry about the cascading of file names. <tt>llvmc</tt> will | |
| create temporary files and ensure that the output of one phase is the | |
| input to the next phase.</td> | |
| </tr> | |
| <tr> | |
| <td><tt>%opt%</tt></td> | |
| <td class="td_left">Replaced with the optimization options for the | |
| tool. If the tool understands the <tt>-O</tt> options then that will | |
| be passed. Otherwise, the <tt>lang.optN</tt> series of configuration | |
| items will specify which arguments are to be given.</td> | |
| </tr> | |
| <tr> | |
| <td><tt>%out%</tt></td> | |
| <td class="td_left">Replaced with the full path of the output file. | |
| Note that this is not necessarily the output file specified with the | |
| <tt>-o</tt> option on <tt>llvmc</tt>'s command line. It might be a | |
| temporary file that will be passed to a subsequent phase's input. | |
| </td> | |
| </tr> | |
| <tr> | |
| <td><tt>%stats%</tt></td> | |
| <td class="td_left">If your command accepts the <tt>-stats</tt> option, | |
| use this substitution token. If the user requested <tt>-stats</tt> | |
| from the <tt>llvmc</tt> command line then this token will be replaced | |
| with <tt>-stats</tt>, otherwise it will be ignored. | |
| </td> | |
| </tr> | |
| <tr> | |
| <td><tt>%target%</tt></td> | |
| <td class="td_left">Replaced with the name of the target "machine" for | |
| which code should be generated. The value used here is taken from the | |
| <tt>llvmc</tt> option <tt>-march</tt>. | |
| </td> | |
| </tr> | |
| <tr> | |
| <td><tt>%time%</tt></td> | |
| <td class="td_left">If your command accepts the <tt>-time-passes</tt> | |
| option, use this substitution token. If the user requested | |
| <tt>-time-passes</tt> from the <tt>llvmc</tt> command line then this | |
| token will be replaced with <tt>-time-passes</tt>, otherwise it will | |
| be ignored. | |
| </td> | |
| </tr> | |
| </tbody> | |
| </table> | |
| </div> | |
| <!-- _______________________________________________________________________ --> | |
| <div class="doc_subsection"><a name="sample">Sample Config File</a></div> | |
| <div class="doc_text"> | |
| <p>Since an example is always instructive, here's how the Stacker language | |
| configuration file looks.</p> | |
| <pre><tt> | |
| # Stacker Configuration File For llvmc | |
| ########################################################## | |
| # Language definitions | |
| ########################################################## | |
| lang.name=Stacker | |
| lang.opt1=-simplifycfg -instcombine -mem2reg | |
| lang.opt2=-simplifycfg -instcombine -mem2reg -load-vn \ | |
| -gcse -dse -scalarrepl -sccp | |
| lang.opt3=-simplifycfg -instcombine -mem2reg -load-vn \ | |
| -gcse -dse -scalarrepl -sccp -branch-combine -adce \ | |
| -globaldce -inline -licm | |
| lang.opt4=-simplifycfg -instcombine -mem2reg -load-vn \ | |
| -gcse -dse -scalarrepl -sccp -ipconstprop \ | |
| -branch-combine -adce -globaldce -inline -licm | |
| lang.opt5=-simplifycfg -instcombine -mem2reg --load-vn \ | |
| -gcse -dse scalarrepl -sccp -ipconstprop \ | |
| -branch-combine -adce -globaldce -inline -licm \ | |
| -block-placement | |
| ########################################################## | |
| # Pre-processor definitions | |
| ########################################################## | |
| # Stacker doesn't have a preprocessor but the following | |
| # allows the -E option to be supported | |
| preprocessor.command=cp %in% %out% | |
| preprocessor.required=false | |
| ########################################################## | |
| # Translator definitions | |
| ########################################################## | |
| # To compile stacker source, we just run the stacker | |
| # compiler with a default stack size of 2048 entries. | |
| translator.command=stkrc -s 2048 %in% -o %out% %time% \ | |
| %stats% %force% %args% | |
| # stkrc doesn't preprocess but we set this to true so | |
| # that we don't run the cp command by default. | |
| translator.preprocesses=true | |
| # The translator is required to run. | |
| translator.required=true | |
| # stkrc doesn't handle the -On options | |
| translator.output=bytecode | |
| ########################################################## | |
| # Optimizer definitions | |
| ########################################################## | |
| # For optimization, we use the LLVM "opt" program | |
| optimizer.command=opt %in% -o %out% %opt% %time% %stats% \ | |
| %force% %args% | |
| optimizer.required = true | |
| # opt doesn't translate | |
| optimizer.translates = no | |
| # opt doesn't preprocess | |
| optimizer.preprocesses=no | |
| # opt produces bytecode | |
| optimizer.output = bc | |
| ########################################################## | |
| # Assembler definitions | |
| ########################################################## | |
| assembler.command=llc %in% -o %out% %target% %time% %stats% | |
| </tt></pre> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"><a name="glossary">Glossary</a></div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>This document uses precise terms in reference to the various artifacts and | |
| concepts related to compilation. The terms used throughout this document are | |
| defined below.</p> | |
| <dl> | |
| <dt><a name="def_assembly"><b>assembly</b></a></dt> | |
| <dd>A compilation <a href="#def_phase">phase</a> in which LLVM bytecode or | |
| LLVM assembly code is assembled to a native code format (either target | |
| specific aseembly language or the platform's native object file format). | |
| </dd> | |
| <dt><a name="def_compiler"><b>compiler</b></a></dt> | |
| <dd>Refers to any program that can be invoked by <tt>llvmc</tt> to accomplish | |
| the work of one or more compilation <a href="#def_phase">phases</a>.</dd> | |
| <dt><a name="def_driver"><b>driver</b></a></dt> | |
| <dd>Refers to <tt>llvmc</tt> itself.</dd> | |
| <dt><a name="def_linking"><b>linking</b></a></dt> | |
| <dd>A compilation <a href="#def_phase">phase</a> in which LLVM bytecode files | |
| and (optionally) native system libraries are combined to form a complete | |
| executable program.</dd> | |
| <dt><a name="def_optimization"><b>optimization</b></a></dt> | |
| <dd>A compilation <a href="#def_phase">phase</a> in which LLVM bytecode is | |
| optimized.</dd> | |
| <dt><a name="def_phase"><b>phase</b></a></dt> | |
| <dd>Refers to any one of the five compilation phases that that | |
| <tt>llvmc</tt> supports. The five phases are: | |
| <a href="#def_preprocessing">preprocessing</a>, | |
| <a href="#def_translation">translation</a>, | |
| <a href="#def_optimization">optimization</a>, | |
| <a href="#def_assembly">assembly</a>, | |
| <a href="#def_linking">linking</a>.</dd> | |
| <dt><a name="def_sourcelanguage"><b>source language</b></a></dt> | |
| <dd>Any common programming language (e.g. C, C++, Java, Stacker, ML, | |
| FORTRAN). These languages are distinguished from any of the lower level | |
| languages (such as LLVM or native assembly), by the fact that a | |
| <a href="#def_translation">translation</a> <a href="#def_phase">phase</a> | |
| is required before LLVM can be applied.</dd> | |
| <dt><a name="def_tool"><b>tool</b></a></dt> | |
| <dd>Refers to any program in the LLVM tool set.</dd> | |
| <dt><a name="def_translation"><b>translation</b></a></dt> | |
| <dd>A compilation <a href="#def_phase">phase</a> in which | |
| <a href="#def_sourcelanguage">source language</a> code is translated into | |
| either LLVM assembly language or LLVM bytecode.</dd> | |
| </dl> | |
| </div> | |
| <!-- *********************************************************************** --> | |
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