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Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]7 <title>LLVM 2.4 Release Notes</title>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]8</head>
9<body>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]10
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]11<div class="doc_title">LLVM 2.4 Release Notes</div>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]12
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]13<ol>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]14 <li><a href="#intro">Introduction</a></li>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]15 <li><a href="#subproj">Sub-project Status Update</a></li>
16 <li><a href="#whatsnew">What's New in LLVM?</a></li>
Chris Lattner4b538b92004-04-30 22:17:12 +0000[diff] [blame]17 <li><a href="GettingStarted.html">Installation Instructions</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]18 <li><a href="#portability">Portability and Supported Platforms</a></li>
Dan Gohman44aa9212008-10-14 16:23:02 +0000[diff] [blame]19 <li><a href="#knownproblems">Known Problems</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]20 <li><a href="#additionalinfo">Additional Information</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]21</ol>
22
Chris Lattner7911ce22004-05-23 21:07:27 +0000[diff] [blame]23<div class="doc_author">
Dan Gohman44aa9212008-10-14 16:23:02 +0000[diff] [blame]24 <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]25</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]26
27<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]28<div class="doc_section">
29 <a name="intro">Introduction</a>
30</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]31<!-- *********************************************************************** -->
32
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]33<div class="doc_text">
34
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]35<p>This document contains the release notes for the LLVM Compiler
36Infrastructure, release 2.4. Here we describe the status of LLVM, including
37major improvements from the previous release and significant known problems.
38All LLVM releases may be downloaded from the <a
39href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]40
Chris Lattner7506b1d2004-12-07 08:04:13 +0000[diff] [blame]41<p>For more information about LLVM, including information about the latest
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]42release, please check out the <a href="http://llvm.org/">main LLVM
Chris Lattner47ad72c2003-10-07 21:38:31 +0000[diff] [blame]43web site</a>. If you have questions or comments, the <a
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]44href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
45List</a> is a good place to send them.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]46
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]47<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]48main LLVM web page, this document applies to the <i>next</i> release, not the
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]49current one. To see the release notes for a specific release, please see the
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]50<a href="http://llvm.org/releases/">releases page</a>.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]51
52</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]53
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]54<!-- Unfinished features in 2.4:
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]55 Machine LICM
56 Machine Sinking
57 LegalizeDAGTypes
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]58 llc -enable-value-prop, propagation of value info (sign/zero ext info) from
59 one MBB to another
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]60 -->
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]61
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]62 <!-- for announcement email:
63 mention dev mtg
Chris Lattnercdb0e4c2008-10-12 22:57:58 +0000[diff] [blame]64 Xcode 3.1 and 3.1.1.
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]65 -->
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]66
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]67<!-- *********************************************************************** -->
68<div class="doc_section">
69 <a name="subproj">Sub-project Status Update</a>
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]70</div>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]71<!-- *********************************************************************** -->
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]72
73<div class="doc_text">
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]74<p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]75The LLVM 2.4 distribution currently consists of code from the core LLVM
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000[diff] [blame]76repository (which roughly includes the LLVM optimizers, code generators and
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]77supporting tools) and the llvm-gcc repository. In addition to this code, the
78LLVM Project includes other sub-projects that are in development. The two which
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]79are the most actively developed are the <a href="#clang">Clang Project</a> and
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]80the <a href="#vmkit">VMKit Project</a>.
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]81</p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]82
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]83</div>
84
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]85
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]86<!--=========================================================================-->
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]87<div class="doc_subsection">
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000[diff] [blame]88<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]89</div>
90
91<div class="doc_text">
92
93<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
94a set of new 'LLVM native' front-end technologies for the LLVM optimizer
95and code generator. Clang is continuing to make major strides forward in all
96areas. Its C and Objective-C parsing support is very solid, and the code
97generation support is far enough along to build many C applications. While not
98yet production quality, it is progressing very nicely. In addition, C++
99front-end work has started to make significant progress.</p>
100
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]101<p>Clang, in conjunction with the <tt>ccc</tt> driver, is now usable as a
102replacement for gcc for building some small- to medium-sized C applications.
Daniel Dunbar13739432008-10-14 23:25:09 +0000[diff] [blame]103Additionally, Clang now has code generation support for Objective-C on Mac OS X
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]104platform. Major highlights include:</p>
105
Daniel Dunbar13739432008-10-14 23:25:09 +0000[diff] [blame]106<ul>
107 <li> Clang/ccc pass almost all of the LLVM test suite on Mac OS X and Linux
108on the 32-bit x86 architecture. This includes significant C
109applications such as <a href="http://www.sqlite.org">sqlite3</a>,
110<a href="http://www.lua.org">lua</a>, and
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]111<a href="http://www.clamav.net">Clam AntiVirus</a>. </li>
Daniel Dunbar13739432008-10-14 23:25:09 +0000[diff] [blame]112
113 <li> Clang can build the majority of Objective-C examples shipped with the
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]114Mac OS X Developer Tools. </li>
Daniel Dunbar13739432008-10-14 23:25:09 +0000[diff] [blame]115</ul>
116
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]117<p>Clang code generation still needs considerable testing and development,
118however. Some areas under active development include:</p>
119
Daniel Dunbar13739432008-10-14 23:25:09 +0000[diff] [blame]120<ul>
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]121 <li> Improved support for C and Objective-C features, for example
122 variable-length arrays, va_arg, exception handling (Obj-C), and garbage
123 collection (Obj-C). </li>
124 <li> ABI compatibility, especially for platforms other than 32-bit
125 x86. </li>
Daniel Dunbar13739432008-10-14 23:25:09 +0000[diff] [blame]126</ul>
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]127
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000[diff] [blame]128</div>
129
130<!--=========================================================================-->
131<div class="doc_subsection">
132<a name="clangsa">Clang Static Analyzer</a>
133</div>
134
135<div class="doc_text">
136
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]137<p>The Clang project also includes an early stage static source code analysis
138tool for <a href="http://clang.llvm.org/StaticAnalysis.html">automatically
139finding bugs</a> in C and Objective-C programs. The tool performs a growing set
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]140of checks to find bugs that occur on a specific path within a program. Examples
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]141of bugs the tool finds include logic errors such as null dereferences,
142violations of various API rules, dead code, and potential memory leaks in
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]143Objective-C programs. Since its inception, public feedback on the tool has been
144extremely positive, and conservative estimates put the number of real bugs it
145has found in industrial-quality software on the order of thousands.</p>
Chris Lattnercc042612008-10-14 00:52:49 +0000[diff] [blame]146
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]147<p>The tool also provides a simple web GUI to inspect potential bugs found by
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]148the tool. While still early in development, the GUI illustrates some of the key
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]149features of Clang: accurate source location information, which is used by the
150GUI to highlight specific code expressions that relate to a bug (including those
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]151that span multiple lines); and built-in knowledge of macros, which is used to
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]152perform inline expansion of macros within the GUI itself.</p>
153
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]154<p>The set of checks performed by the static analyzer is gradually expanding,
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]155and future plans for the tool include full source-level inter-procedural
156analysis and deeper checks such as buffer overrun detection. There are many
157opportunities to extend and enhance the static analyzer, and anyone interested
158in working on this project is encouraged to get involved!</p>
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]159
160</div>
161
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]162<!--=========================================================================-->
163<div class="doc_subsection">
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]164<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]165</div>
166
167<div class="doc_text">
168<p>
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]169The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]170a JVM and a CLI Virtual Machines (Microsoft .NET is an
171implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
172
Nicolas Geoffray56d313d2008-10-15 20:25:04 +0000[diff] [blame]173<p>Following LLVM 2.4, VMKit has its first release 0.24 that you can find on its
174<a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
175bug fixes, cleanup and new features. The major changes are:</p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]176
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]177<ul>
178
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]179<li> Support for generics in the .Net virtual machine.</li>
180<li> Initial support for the Mono class libraries. </li>
Gabor Greif804ffb62008-10-15 10:29:51 +0000[diff] [blame]181<li> Support for MacOSX/x86, following LLVM's support for exceptions in
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]182JIT on MacOSX/x86. </li>
183<li> A new vmkit driver: a program to run java or .net applications. The driver
184supports llvm command line arguments including the new "-fast" option. </li>
Gabor Greif804ffb62008-10-15 10:29:51 +0000[diff] [blame]185<li> A new memory allocation scheme in the JVM that makes unloading a
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]186class loader very fast. </li>
187<li> VMKit now follows the LLVM Makefile machinery. </li>
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]188
189</ul>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]190</div>
191
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]192
193<!-- *********************************************************************** -->
194<div class="doc_section">
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]195 <a name="whatsnew">What's New in LLVM?</a>
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]196</div>
197<!-- *********************************************************************** -->
198
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]199<div class="doc_text">
200
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]201<p>This release includes a huge number of bug fixes, performance tweaks, and
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]202minor improvements. Some of the major improvements and new features are listed
203in this section.
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]204</p>
205</div>
206
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]207<!--=========================================================================-->
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]208<div class="doc_subsection">
Chris Lattner252b83d2008-02-06 18:00:06 +0000[diff] [blame]209<a name="majorfeatures">Major New Features</a>
210</div>
211
212<div class="doc_text">
213
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]214<p>LLVM 2.4 includes several major new capabilities:</p>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]215
216<ul>
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]217<li><p>The most visible end-user change in LLVM 2.4 is that it includes many
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]218optimizations and changes to make -O0 compile times much faster. You should see
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]219improvements in speed on the order of 30% (or more) than in LLVM 2.3. There are
220many pieces to this change described in more detail below. The speedups and new
221components can also be used for JIT compilers that want fast
222compilation.</p></li>
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]223
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]224<li><p>The biggest change to the LLVM IR is that Multiple Return Values (which
225were introduced in LLVM 2.3) have been generalized to full support for "First
226Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using
227structs and arrays as values in a function. This capability is mostly useful
228for front-end authors, who prefer to treat things like complex numbers, simple
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]229tuples, dope vectors, etc., as Value*'s instead of as a tuple of Value*'s or as
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]230memory values. Bitcode files from LLVM 2.3 will automatically migrate to the
231general representation.</p></li>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]232
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]233<li><p>LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]234target only has support for 8 bit registers, and a number of other crazy
235constraints. While the port is still in early development stages, it shows some
236interesting things you can do with LLVM.</p></li>
Chris Lattnerbc5786b2008-06-05 06:57:39 +0000[diff] [blame]237
Chris Lattner8170c102008-02-10 08:18:42 +0000[diff] [blame]238</ul>
239
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]240</div>
241
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]242
243<!--=========================================================================-->
244<div class="doc_subsection">
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]245<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]246</div>
247
248<div class="doc_text">
249
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]250<p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
251front-ends and driver with the LLVM optimizer and code generator. It currently
252includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]253
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]254<ul>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]255<li>LLVM 2.4 supports the full set of atomic <tt>__sync_*</tt> builtins. LLVM
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]2562.3 only supported those used by OpenMP, but 2.4 supports them all. Note that
257while llvm-gcc supports all of these builtins, not all targets do. X86 support
258them all in both 32-bit and 64-bit mode and PowerPC supports them all except for
259the 64-bit operations when in 32-bit mode.</li>
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]260
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]261<li>llvm-gcc now supports an <tt>-flimited-precision</tt> option, which tells
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]262the compiler that it is okay to use low-precision approximations of certain libm
263functions (like <tt>exp</tt>, <tt>log</tt>, etc). This allows you to get high
264performance if you only need (say) 12-bits of precision.</li>
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]265
266<li>llvm-gcc now supports a C language extension known as "<a
Gabor Greif86af90d2008-10-17 14:43:58 +0000[diff] [blame]267href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks</a>".
268This feature is similar to nested functions and closures, but does not
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]269require stack trampolines (with most ABIs), and supports returning closures
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]270from functions that define them. Note that actually <em>using</em> Blocks
271requires a small runtime that is not included with llvm-gcc.</li>
272
273<li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support
274transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and
275later) this allows the use of LTO with other optimization levels like -Os.
276Previously, LTO could only be used with -O4, which implied optimizations in
277-O3 that can increase code size.</li>
Gabor Greifa3bd11d2008-06-09 06:06:18 +0000[diff] [blame]278</ul>
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]279
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]280</div>
281
282
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]283<!--=========================================================================-->
284<div class="doc_subsection">
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]285<a name="coreimprovements">LLVM Core Improvements</a>
286</div>
287
288<div class="doc_text">
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]289<p>New features include:</p>
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]290
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]291<ul>
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]292<li>A major change to the <tt>Use</tt> class landed, which shrank it by 25%. Since
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]293this is a pervasive part of the LLVM, it ended up reducing the memory use of
294LLVM IR in general by 15% for most programs.</li>
295
296<li>Values with no names are now pretty printed by <tt>llvm-dis</tt> more
297nicely. They now print as "<tt>%3 = add i32 %A, 4</tt>" instead of
298"<tt>add i32 %A, 4 ; &lt;i32&gt;:3</tt>", which makes it much easier to read.
299</li>
300
301<li>LLVM 2.4 includes some changes for better vector support. First, the shift
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]302operations (<tt>shl</tt>, <tt>ashr</tt>, and <tt>lshr</tt>) now all support
303vectors and do an element-by-element shift (shifts of the whole vector can be
304accomplished by bitcasting the vector to &lt;1 x i128&gt;, for example). Second,
305there is initial support in development for vector comparisons with the
306<tt><a href="LangRef.html#i_fcmp">fcmp</a>/<a href="LangRef.html#i_icmp">icmp</a></tt>
Chris Lattnercc042612008-10-14 00:52:49 +0000[diff] [blame]307instructions. These instructions compare two vectors and return a vector of
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]308<tt>i1</tt>'s for each result. Note that there is very little codegen support
309available for any of these IR features though.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]310
311<li>A new <tt>DebugInfoBuilder</tt> class is available, which makes it much
312easier for front-ends to create debug info descriptors, similar to the way that
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]313<tt>IRBuilder</tt> makes it easier to create LLVM IR.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]314
Dan Gohman1bbddce2008-10-14 16:13:59 +0000[diff] [blame]315<li>The <tt>IRBuilder</tt> class is now parameterized by a class responsible
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]316for constant folding. The default <tt>ConstantFolder</tt> class does target independent
317constant folding. The <tt>NoFolder</tt> class does no constant folding at all, which is
318useful when learning how LLVM works. The <tt>TargetFolder</tt> class folds the most,
Duncan Sands9ba23792008-10-14 07:06:37 +0000[diff] [blame]319doing target dependent constant folding.</li>
320
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]321<li>LLVM now supports "function attributes", which allow us to separate return
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]322value attributes from function attributes. LLVM now supports attributes on a
323function itself, a return value, and its parameters. New supported function
Bill Wendling741748a2008-10-27 09:27:33 +0000[diff] [blame]324attributes include <tt>noinline/alwaysinline</tt> and the <tt>opt-size</tt> flag,
325which says the function should be optimized for code size.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]326
Chris Lattnercce6d4b2008-10-12 18:30:33 +0000[diff] [blame]327<li>LLVM IR now directly represents "common" linkage, instead of
328 representing it as a form of weak linkage.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]329
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]330</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]331
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]332</div>
333
334<!--=========================================================================-->
335<div class="doc_subsection">
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]336<a name="optimizer">Optimizer Improvements</a>
337</div>
338
339<div class="doc_text">
340
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]341<p>In addition to a huge array of bug fixes and minor performance tweaks, this
342release includes a few major enhancements and additions to the optimizers:</p>
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]343
344<ul>
345
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]346<li>The Global Value Numbering (GVN) pass now does local Partial Redundancy
347Elimination (PRE) to eliminate some partially redundant expressions in cases
348where doing so won't grow code size.</li>
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]349
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]350<li>LLVM 2.4 includes a new loop deletion pass (which removes output-free
351provably-finite loops) and a rewritten Aggressive Dead Code Elimination (ADCE)
352pass that no longer uses control dependence information. These changes speed up
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]353the optimizer and also prevent it from deleting output-free infinite
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]354loops.</li>
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]355
Duncan Sands1050d732008-10-13 18:42:43 +0000[diff] [blame]356<li>The new AddReadAttrs pass works out which functions are read-only or
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]357read-none (these correspond to 'pure' and 'const' in GCC) and marks them
Duncan Sands1050d732008-10-13 18:42:43 +0000[diff] [blame]358with the appropriate attribute.</li>
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]359
360<li>LLVM 2.4 now includes a new SparsePropagation framework, which makes it
361trivial to build lattice-based dataflow solvers that operate over LLVM IR. Using
362this interface means that you just define objects to represent your lattice
363values and the transfer functions that operate on them. It handles the
364mechanics of worklist processing, liveness tracking, handling PHI nodes,
365etc.</li>
366
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]367<li>The Loop Strength Reduction and induction variable optimization passes have
368several improvements to avoid inserting MAX expressions, to optimize simple
369floating point induction variables and to analyze trip counts of more
370loops.</li>
371
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]372<li>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were
373pulled out of the Instruction Combining pass and put into a new
374<tt>ValueTracking.h</tt> header, where they can be reused by other passes.</li>
375
376<li>The tail duplication pass has been removed from the standard optimizer
377sequence used by llvm-gcc. This pass still exists, but the benefits it once
378provided are now achieved by other passes.</li>
379
Chris Lattner0b832202008-06-08 02:45:07 +0000[diff] [blame]380</ul>
381
382</div>
383
384<!--=========================================================================-->
385<div class="doc_subsection">
386<a name="codegen">Code Generator Improvements</a>
387</div>
388
389<div class="doc_text">
390
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]391<p>We have put a significant amount of work into the code generator infrastructure,
Chris Lattner0b832202008-06-08 02:45:07 +0000[diff] [blame]392which allows us to implement more aggressive algorithms and make it run
393faster:</p>
394
395<ul>
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]396<li>The target-independent code generator supports (and the X86 backend
397 currently implements) a new interface for "fast" instruction selection. This
398 interface is optimized to produce code as quickly as possible, sacrificing
399 code quality to do it. This is used by default at -O0 or when using
400 "llc -fast" on X86. It is straight-forward to add support for
401 other targets if faster -O0 compilation is desired.</li>
402
403<li>In addition to the new 'fast' instruction selection path, many existing
404 pieces of the code generator have been optimized in significant ways.
405 SelectionDAG's are now pool allocated and use better algorithms in many
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]406 places, the ".s" file printers now use <tt>raw_ostream</tt> to emit text much faster,
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]407 etc. The end result of these improvements is that the compiler also takes
408 substantially less time to generate code that is just as good (and often
409 better) than before.</li>
410
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]411<li>Each target has been split to separate the ".s" file printing logic from the
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]412 rest of the target. This enables JIT compilers that don't link in the
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]413 (somewhat large) code and data tables used for printing a ".s" file.</li>
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]414
415<li>The code generator now includes a "stack slot coloring" pass, which packs
416 together individual spilled values into common stack slots. This reduces
417 the size of stack frames with many spills, which tends to increase L1 cache
418 effectiveness.</li>
419
420<li>Various pieces of the register allocator (e.g. the coalescer and two-address
421 operation elimination pass) now know how to rematerialize trivial operations
422 to avoid copies and include several other optimizations.</li>
423
424<li>The <a href="CodeGenerator.html#selectiondag_process">graphs</a> produced by
425 the <tt>llc -view-*-dags</tt> options are now significantly prettier and
426 easier to read.</li>
427
428<li>LLVM 2.4 includes a new register allocator based on Partitioned Boolean
429 Quadratic Programming (PBQP). This register allocator is still in
430 development, but is very simple and clean.</li>
Chris Lattner0b832202008-06-08 02:45:07 +0000[diff] [blame]431
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]432</ul>
433
434</div>
435
436
437<!--=========================================================================-->
438<div class="doc_subsection">
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]439<a name="targetspecific">Target Specific Improvements</a>
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]440</div>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]441
Chris Lattner738bd302006-04-18 06:32:08 +0000[diff] [blame]442<div class="doc_text">
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]443<p>New target-specific features include:
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]444</p>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]445
446<ul>
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]447<li>Exception handling is supported by default on Linux/x86-64.</li>
Duncan Sandsbbf379a2008-10-13 17:32:15 +0000[diff] [blame]448<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li>
Gabor Greif6f038f42008-10-27 10:17:24 +0000[diff] [blame]449<li><tt>@llvm.frameaddress</tt> now supports getting the frame address of stack frames
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]450 &gt; 0 on x86/x86-64.</li>
Bruno Cardoso Lopesb7e1a4f2008-10-25 14:56:26 +0000[diff] [blame]451<li>MIPS has improved a lot since last release, the most important changes
452 are: Little endian support, floating point support, allegrex core and
453 intrinsics support. O32 ABI is improved but isn't complete. The EABI
454 was implemented and is fully supported. We also have support for small
455 sections and gp_rel relocation for its access, a threshold in bytes can be
456 specified through command line.</li>
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]457<li>The PowerPC backend now supports trampolines.</li>
Chris Lattner77d29b12008-06-05 08:02:49 +0000[diff] [blame]458</ul>
Chris Lattner77d29b12008-06-05 08:02:49 +0000[diff] [blame]459
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]460</div>
Chris Lattner77d29b12008-06-05 08:02:49 +0000[diff] [blame]461
462
463<!--=========================================================================-->
464<div class="doc_subsection">
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]465<a name="otherimprovements">Other Improvements</a>
466</div>
467
468<div class="doc_text">
469<p>New features include:
470</p>
471
472<ul>
Mikhail Glushenkov49feb452008-10-13 02:46:01 +0000[diff] [blame]473<li><tt>llvmc2</tt> (the generic compiler driver) gained plugin
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]474 support. It is now easier to experiment with <tt>llvmc2</tt> and
475 build your own tools based on it.</li>
476
477<li>LLVM 2.4 includes a number of new generic algorithms and data structures,
Dan Gohmanbd9f9af2008-10-14 15:14:55 +0000[diff] [blame]478 include a scoped hash table, 'immutable' data structures, a simple
479 free-list manager, and a <tt>raw_ostream</tt> class.
480 The <tt>raw_ostream</tt> class and
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]481 <tt>format</tt> allow for efficient file output, and various pieces of LLVM
482 have switched over to use it. The eventual goal is to eliminate
483 std::ostream in favor of it.</li>
484
Tanya Lattnera7ec7062008-11-04 18:40:27 +0000[diff] [blame^]485<li><p>LLVM 2.4 includes an optional build system based on CMake. It
486 still is on its early stages but can be useful for Visual C++
487 userswho can not use the Visual Studio IDE.</p></li>
488
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]489</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]490
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]491</div>
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000[diff] [blame]492
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]493<!--=========================================================================-->
494<div class="doc_subsection">
495<a name="changes">Major Changes and Removed Features</a>
496</div>
497
498<div class="doc_text">
499
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]500<p>If you're already an LLVM user or developer with out-of-tree changes based
501on LLVM 2.3, this section lists some "gotchas" that you may run into upgrading
502from the previous release.</p>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]503
504<ul>
505
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]506<li>The LLVM IR generated by llvm-gcc no longer names all instructions. This
507 makes it run faster, but may be more confusing to some people. If you
508 prefer to have names, the '<tt>opt -instnamer</tt>' pass will add names to
509 all instructions.</li>
510
511<li>The LoadVN and GCSE passes have been removed from the tree. They are
512 obsolete and have been replaced with the GVN and MemoryDependence passes.
513 </li>
514</ul>
515
516
517<p>In addition, many APIs have changed in this release. Some of the major LLVM
518API changes are:</p>
519
520<ul>
521
Devang Patelb34dd132008-10-14 20:03:43 +0000[diff] [blame]522<li>Now, function attributes and return value attributes are managed
Gabor Greif3bd3a262008-10-15 10:47:24 +0000[diff] [blame]523separately. Interface exported by <tt>ParameterAttributes.h</tt> header is now
Devang Patelb34dd132008-10-14 20:03:43 +0000[diff] [blame]524experted by <tt>Attributes.h</tt> header. The new attributes interface changes are:
525<ul>
526<li><tt>getParamAttrs</tt> method is now replaced by
527<tt>getParamAttributes</tt>, <tt>getRetAttributes</tt> and
528<tt>getFnAttributes</tt> methods.</li>
529<li> Return value attributes are stored at index 0. Function attributes are
530stored at index ~0U. Parameter attributes are stored at index that matches
531parameter number.</li>
532<li> <tt>ParamAttr</tt> namespace is now renamed as <tt>Attribute</tt>.</li>
Gabor Greif804ffb62008-10-15 10:29:51 +0000[diff] [blame]533<li> The name of the class that manages reference count of opaque
Devang Patelb34dd132008-10-14 20:03:43 +0000[diff] [blame]534attributes is changed from <tt>PAListPtr</tt> to <tt>AttrListPtr</tt>.</li>
535<li> <tt>ParamAttrsWithIndex</tt> is now renamed as <tt>AttributeWithIndex</tt>.
536</li>
537</ul>
538</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]539
540<li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and
541<tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be
542converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]543"<tt>llvm/Analysis/ValueTracking.h</tt>".</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]544
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]545<li>The APIs to create various instructions have changed from lower case
546 "create" methods to upper case "Create" methods (e.g.
547 <tt>BinaryOperator::create</tt>). LLVM 2.4 includes both cases, but the
548 lower case ones are removed in mainline, please migrate.</li>
549
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]550<li>Various header files like "<tt>llvm/ADT/iterator</tt>" were given a ".h" suffix.
551 Change your code to #include "<tt>llvm/ADT/iterator.h</tt>" instead.</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]552
Chris Lattnerf322a982008-10-27 04:39:23 +0000[diff] [blame]553<li>The <tt>getresult</tt> instruction has been removed and replaced with the
554 <tt>extractvalue</tt> instruction. This is part of support for first class
555 aggregates.</li>
556
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]557<li>In the code generator, many <tt>MachineOperand</tt> predicates were renamed to be
Chris Lattnerf1796b62008-10-14 06:37:11 +0000[diff] [blame]558 shorter (e.g. <tt>isFrameIndex()</tt> -&gt; <tt>isFI()</tt>),
559 <tt>SDOperand</tt> was renamed to <tt>SDValue</tt> (and the "<tt>Val</tt>"
560 member was changed to be the <tt>getNode()</tt> accessor), and the
561 <tt>MVT::ValueType</tt> enum has been replaced with an "<tt>MVT</tt>"
Dan Gohman9aeea5b2008-10-14 17:06:44 +0000[diff] [blame]562 struct. The <tt>getSignExtended</tt> and <tt>getValue</tt> methods in the
563 ConstantSDNode class were renamed to <tt>getSExtValue</tt> and
564 <tt>getZExtValue</tt> respectively, to be more consistent with
565 the <tt>ConstantInt</tt> class.</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]566</ul>
567
568</div>
569
570
571
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]572<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]573<div class="doc_section">
574 <a name="portability">Portability and Supported Platforms</a>
575</div>
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]576<!-- *********************************************************************** -->
577
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]578<div class="doc_text">
579
John Criswell0b5b5e92004-12-08 20:35:47 +0000[diff] [blame]580<p>LLVM is known to work on the following platforms:</p>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000[diff] [blame]581
582<ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]583<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Reid Spencer00812e22005-05-17 02:47:27 +0000[diff] [blame]584 (and probably other unix-like systems).</li>
Chris Lattner000c73b2008-02-06 06:30:34 +0000[diff] [blame]585<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]586 64-bit modes.</li>
Chris Lattner252b83d2008-02-06 18:00:06 +0000[diff] [blame]587<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]588<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
589 support is available for native builds with Visual C++).</li>
Gabor Greif96a89c72008-06-05 18:39:01 +0000[diff] [blame]590<li>Sun UltraSPARC workstations running Solaris 10.</li>
John Criswell9321fa82005-05-13 20:28:15 +0000[diff] [blame]591<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif96a89c72008-06-05 18:39:01 +0000[diff] [blame]592<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000[diff] [blame]593</ul>
594
Chris Lattnerbc5786b2008-06-05 06:57:39 +0000[diff] [blame]595<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Brian Gaekeb0fd7612004-05-09 05:28:35 +0000[diff] [blame]596to the machine and operating system on which it is built. However, minor
597porting may be required to get LLVM to work on new platforms. We welcome your
598portability patches and reports of successful builds or error messages.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]599
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]600</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]601
602<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]603<div class="doc_section">
604 <a name="knownproblems">Known Problems</a>
605</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]606<!-- *********************************************************************** -->
607
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]608<div class="doc_text">
609
610<p>This section contains all known problems with the LLVM system, listed by
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]611component. As new problems are discovered, they will be added to these
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]612sections. If you run into a problem, please check the <a
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]613href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]614there isn't already one.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]615
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]616</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]617
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]618<!-- ======================================================================= -->
619<div class="doc_subsection">
620 <a name="experimental">Experimental features included with this release</a>
621</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]622
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]623<div class="doc_text">
624
Misha Brukman6df9e2c2004-05-12 21:46:05 +0000[diff] [blame]625<p>The following components of this LLVM release are either untested, known to
626be broken or unreliable, or are in early development. These components should
627not be relied on, and bugs should not be filed against them, but they may be
628useful to some people. In particular, if you would like to work on one of these
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]629components, please contact us on the <a
630href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]631
632<ul>
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]633<li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]634<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
Chris Lattner000c73b2008-02-06 06:30:34 +0000[diff] [blame]635 value for this option.</li>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]636</ul>
637
638</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]639
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]640<!-- ======================================================================= -->
641<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]642 <a name="x86-be">Known problems with the X86 back-end</a>
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]643</div>
644
645<div class="doc_text">
646
647<ul>
Anton Korobeynikova6094be2008-06-08 10:24:13 +0000[diff] [blame]648 <li>The X86 backend does not yet support
649 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
650 floating point stack</a>. It supports the 'f' and 't' constraints, but not
651 'u'.</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000[diff] [blame]652 <li>The X86 backend generates inefficient floating point code when configured
653 to generate code for systems that don't have SSE2.</li>
Duncan Sands47eff2b2008-06-08 19:38:43 +0000[diff] [blame]654 <li>Win64 code generation wasn't widely tested. Everything should work, but we
Anton Korobeynikova6094be2008-06-08 10:24:13 +0000[diff] [blame]655 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
656 currently due
657 to <a href="http://llvm.org/PR2255">several</a>
Chris Lattner04af7cb2008-06-08 23:12:47 +0000[diff] [blame]658 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
659 'u' inline assembly constraint and X87 floating point inline assembly.</li>
Dan Gohman8207ba92008-06-08 23:05:11 +0000[diff] [blame]660 <li>The X86-64 backend does not yet support the LLVM IR instruction
661 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
662 argument constructs on X86-64 by lowering them manually.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]663</ul>
664
665</div>
666
667<!-- ======================================================================= -->
668<div class="doc_subsection">
669 <a name="ppc-be">Known problems with the PowerPC back-end</a>
670</div>
671
672<div class="doc_text">
673
674<ul>
Nicolas Geoffraye4285dc2007-05-15 09:21:28 +0000[diff] [blame]675<li>The Linux PPC32/ABI support needs testing for the interpreter and static
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]676compilation, and lacks support for debug information.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]677</ul>
678
679</div>
680
681<!-- ======================================================================= -->
682<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]683 <a name="arm-be">Known problems with the ARM back-end</a>
684</div>
685
686<div class="doc_text">
687
688<ul>
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]689<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sandsc90d68b2007-09-26 15:59:54 +0000[diff] [blame]690processors, thumb programs can crash or produce wrong
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]691results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]692<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
693</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000[diff] [blame]694<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
695 execute
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]696programs compiled with LLVM. Please use more recent versions of QEMU.</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]697</ul>
698
699</div>
700
701<!-- ======================================================================= -->
702<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]703 <a name="sparc-be">Known problems with the SPARC back-end</a>
704</div>
705
706<div class="doc_text">
707
708<ul>
709<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
710 support the 64-bit SPARC ABI (-m64).</li>
711</ul>
712
713</div>
714
715<!-- ======================================================================= -->
716<div class="doc_subsection">
Bruno Cardoso Lopesb7e1a4f2008-10-25 14:56:26 +0000[diff] [blame]717 <a name="mips-be">Known problems with the MIPS back-end</a>
718</div>
719
720<div class="doc_text">
721
722<ul>
723<li>The O32 ABI is not fully supported.</li>
724<li>64-bit MIPS targets are not supported yet.</li>
725</ul>
726
727</div>
728
729<!-- ======================================================================= -->
730<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]731 <a name="alpha-be">Known problems with the Alpha back-end</a>
732</div>
733
734<div class="doc_text">
735
736<ul>
737
738<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
739appropriate nops inserted to ensure restartability.</li>
740
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]741</ul>
742</div>
743
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]744<!-- ======================================================================= -->
745<div class="doc_subsection">
746 <a name="ia64-be">Known problems with the IA64 back-end</a>
747</div>
748
749<div class="doc_text">
750
751<ul>
Chris Lattner04af7cb2008-06-08 23:12:47 +0000[diff] [blame]752<li>The Itanium backend is highly experimental, and has a number of known
753 issues. We are looking for a maintainer for the Itanium backend. If you
Gabor Greif3bd3a262008-10-15 10:47:24 +0000[diff] [blame]754 are interested, please contact the LLVMdev mailing list.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]755</ul>
756
757</div>
758
759<!-- ======================================================================= -->
760<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]761 <a name="c-be">Known problems with the C back-end</a>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]762</div>
763
764<div class="doc_text">
765
766<ul>
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]767<li><a href="http://llvm.org/PR802">The C backend has only basic support for
768 inline assembly code</a>.</li>
Chris Lattner725a0d82007-09-26 06:01:35 +0000[diff] [blame]769<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
770 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]771 C++ code compiled with llc or native compilers.</li>
Duncan Sandsf74c0cc2008-02-10 13:40:55 +0000[diff] [blame]772<li>The C backend does not support all exception handling constructs.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]773</ul>
774
775</div>
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]776
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]777
778<!-- ======================================================================= -->
779<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]780 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]781</div>
Chris Lattner47588f92003-10-02 05:07:23 +0000[diff] [blame]782
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]783<div class="doc_text">
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000[diff] [blame]784
Chris Lattner252b83d2008-02-06 18:00:06 +0000[diff] [blame]785<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
786Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Gabor Greif3bd3a262008-10-15 10:47:24 +0000[diff] [blame]787LLVMdev mailing list if you are interested.</p>
Chris Lattnerd9ea0172006-08-08 17:27:28 +0000[diff] [blame]788
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]789<p>The only major language feature of GCC not supported by llvm-gcc is
790 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
791 are only supported on some targets. For example, trampolines are only
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]792 supported on some targets (these are used when you take the address of a
793 nested function).</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]794
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]795<p>If you run into GCC extensions which are not supported, please let us know.
796</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]797
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]798</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]799
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]800<!-- ======================================================================= -->
801<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]802 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]803</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]804
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]805<div class="doc_text">
806
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]807<p>The C++ front-end is considered to be fully
Chris Lattner7506b1d2004-12-07 08:04:13 +0000[diff] [blame]808tested and works for a number of non-trivial programs, including LLVM
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]809itself, Qt, Mozilla, etc.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]810
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]811<ul>
Anton Korobeynikov0021fc12008-10-11 18:27:16 +0000[diff] [blame]812<li>Exception handling works well on the X86 and PowerPC targets. Currently
813 only linux and darwin targets are supported (both 32 and 64 bit).</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]814</ul>
Chris Lattnerfcc54b32003-10-07 22:14:37 +0000[diff] [blame]815
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]816</div>
817
Chris Lattner1eb4df62008-10-30 03:58:13 +0000[diff] [blame]818<!-- ======================================================================= -->
819<div class="doc_subsection">
820 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
821</div>
822
823<div class="doc_text">
824<li>Fortran support generally works, but there are still several unresolved bugs
825 in Bugzilla. Please see the tools/gfortran component for details.</li>
826
827<li>The Fortran front-end currently does not build on Darwin (without tweaks)
828 due to unresolved dependencies on the C front-end.</li>
829
830</div>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]831
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]832<!-- ======================================================================= -->
833<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]834 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]835</div>
836
837<div class="doc_text">
838The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
839technology and problems should be expected.
840<ul>
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]841<li>The Ada front-end currently only builds on X86-32. This is mainly due
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]842to lack of trampoline support (pointers to nested functions) on other platforms,
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]843however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]844which does support trampolines.</li>
845<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
846Workaround: configure with --disable-bootstrap.</li>
Duncan Sands978bcee2008-10-13 17:27:23 +0000[diff] [blame]847<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
848and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
849(c380004 also fails with gcc-4.2 mainline).</li>
850<li>Some gcc specific Ada tests continue to crash the compiler.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]851<li>The -E binder option (exception backtraces)
852<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
853crashing if an exception is raised. Workaround: do not use -E.</li>
854<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
855or finish at a non-byte offset</a> in a record. Workaround: do not pack records
856or use representation clauses that result in a field of a non-discrete type
857starting or finishing in the middle of a byte.</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000[diff] [blame]858<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
859'main' as generated by the Ada binder to be invalid</a>.
860Workaround: hand edit the file to use pointers for <tt>argv</tt> and
861<tt>envp</tt> rather than integers.</li>
862<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
863ignored</a>.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]864</ul>
865</div>
866
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]867<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]868<div class="doc_section">
869 <a name="additionalinfo">Additional Information</a>
870</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]871<!-- *********************************************************************** -->
872
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]873<div class="doc_text">
874
Chris Lattner416db102005-05-16 17:13:10 +0000[diff] [blame]875<p>A wide variety of additional information is available on the <a
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000[diff] [blame]876href="http://llvm.org">LLVM web page</a>, in particular in the <a
877href="http://llvm.org/docs/">documentation</a> section. The web page also
Reid Spencer669ed452007-07-09 08:04:31 +0000[diff] [blame]878contains versions of the API documentation which is up-to-date with the
879Subversion version of the source code.
Misha Brukman109d9e82005-03-30 19:14:24 +0000[diff] [blame]880You can access versions of these documents specific to this release by going
881into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]882
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]883<p>If you have any questions or comments about LLVM, please feel free to contact
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]884us via the <a href="http://llvm.org/docs/#maillist"> mailing
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]885lists</a>.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]886
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]887</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]888
889<!-- *********************************************************************** -->
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]890
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]891<hr>
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]892<address>
Misha Brukman38847d52003-12-21 22:53:21 +0000[diff] [blame]893 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]894 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
895 <a href="http://validator.w3.org/check/referer"><img
Chris Lattner8170c102008-02-10 08:18:42 +0000[diff] [blame]896 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]897
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000[diff] [blame]898 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]899 Last modified: $Date$
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]900</address>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]901
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]902</body>
903</html>