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gerrit-public.fairphone.software / toolchain / llvm-project / 5baa413833f9f0932159d60f64adb97fc08c39a3 / . / llvm / docs / ReleaseNotes.html
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Anton Korobeynikovf7c5a6e2008-06-08 10:23:46 +0000[diff] [blame]1
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]2<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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4<html>
5<head>
Reid Spencere4190fa2004-11-18 18:38:58 +0000[diff] [blame]6 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]7 <link rel="stylesheet" href="llvm.css" type="text/css">
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]8 <title>LLVM 2.3 Release Notes</title>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]9</head>
10<body>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]11
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]12<div class="doc_title">LLVM 2.3 Release Notes</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]13
14<ol>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]15 <li><a href="#intro">Introduction</a></li>
Chris Lattnerc75fd522008-06-08 21:58:17 +0000[diff] [blame]16 <li><a href="#changes">Major Changes and Sub-project Status</a></li>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]17 <li><a href="#whatsnew">What's New?</a></li>
Chris Lattner77a51732004-04-30 22:17:12 +0000[diff] [blame]18 <li><a href="GettingStarted.html">Installation Instructions</a></li>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]19 <li><a href="#portability">Portability and Supported Platforms</a></li>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]20 <li><a href="#knownproblems">Known Problems</a>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]21 <li><a href="#additionalinfo">Additional Information</a></li>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]22</ol>
23
Chris Lattner020e1fc2004-05-23 21:07:27 +0000[diff] [blame]24<div class="doc_author">
Chris Lattnera69595e2005-10-29 07:07:09 +0000[diff] [blame]25 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]26</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]27
Chris Lattner6cb64032008-06-05 08:02:49 +0000[diff] [blame]28<!-- Done through Week-of-Mon-20080324.txt -->
29
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]30<!-- *********************************************************************** -->
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]31<div class="doc_section">
32 <a name="intro">Introduction</a>
33</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]34<!-- *********************************************************************** -->
35
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]36<div class="doc_text">
37
38<p>This document contains the release notes for the LLVM compiler
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]39infrastructure, release 2.3. Here we describe the status of LLVM, including
Chris Lattnerbee7b322007-05-23 04:39:32 +0000[diff] [blame]40major improvements from the previous release and any known problems. All LLVM
Chris Lattner98a33492007-05-09 04:58:11 +0000[diff] [blame]41releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
Chris Lattnerbee7b322007-05-23 04:39:32 +0000[diff] [blame]42releases web site</a>.</p>
Chris Lattner62495762003-10-02 16:38:05 +0000[diff] [blame]43
Chris Lattnerb5bb5972004-12-07 08:04:13 +0000[diff] [blame]44<p>For more information about LLVM, including information about the latest
Chris Lattnera69595e2005-10-29 07:07:09 +0000[diff] [blame]45release, please check out the <a href="http://llvm.org/">main LLVM
Chris Lattnere7525b52003-10-07 21:38:31 +0000[diff] [blame]46web site</a>. If you have questions or comments, the <a
47href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]48list</a> is a good place to send them.</p>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]49
Reid Spencerc7f87f22007-07-09 08:04:31 +0000[diff] [blame]50<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattner0a1fd102007-09-21 03:54:09 +0000[diff] [blame]51main LLVM web page, this document applies to the <i>next</i> release, not the
52current one. To see the release notes for a specific releases, please see the
53<a href="http://llvm.org/releases/">releases page</a>.</p>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]54
55</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]56
57<!-- *********************************************************************** -->
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]58<div class="doc_section">
Chris Lattnerc75fd522008-06-08 21:58:17 +0000[diff] [blame]59 <a name="changes">Major Changes and Sub-project Status</a>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]60</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]61<!-- *********************************************************************** -->
62
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]63<div class="doc_text">
64
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]65<p>This is the fourteenth public release of the LLVM Compiler Infrastructure.
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]66It includes a large number of features and refinements from LLVM 2.2.</p>
Chris Lattnerba7bd472003-12-06 20:22:41 +0000[diff] [blame]67
Chris Lattner21a90402004-05-24 04:50:25 +0000[diff] [blame]68</div>
69
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]70<!-- Unfinished features in 2.3:
Chris Lattner2b8a52e2008-02-10 07:46:44 +0000[diff] [blame]71 Machine LICM
72 Machine Sinking
73 LegalizeDAGTypes
74 -->
75
Chris Lattnerba7bd472003-12-06 20:22:41 +0000[diff] [blame]76<!--=========================================================================-->
Chris Lattner406bddf2005-05-15 05:44:51 +0000[diff] [blame]77<div class="doc_subsection">
Chris Lattner6cb64032008-06-05 08:02:49 +0000[diff] [blame]78<a name="changes">Major Changes in LLVM 2.3</a>
Chris Lattnera2735862008-02-10 07:04:35 +0000[diff] [blame]79</div>
80
81<div class="doc_text">
82
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]83<p>LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with
84 llvm-gcc 4.2.</p>
Chris Lattnercdc44ed2008-02-06 18:00:06 +0000[diff] [blame]85
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]86<p>LLVM 2.3 no longer includes the <tt>llvm-upgrade</tt> tool. It was useful
87 for upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a
88 previous LLVM release to do this. One nice impact of this is that the LLVM
89 regression test suite no longer depends on llvm-upgrade, which makes it run
90 faster.</p>
91
92<p>The <tt>llvm2cpp</tt> tool has been folded into llc, use
Chris Lattnerb076b002008-06-08 21:19:07 +0000[diff] [blame]93 <tt>llc -march=cpp</tt> instead of <tt>llvm2cpp</tt>.</p>
94
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]95<p>LLVM API Changes:</p>
Chris Lattner6cb64032008-06-05 08:02:49 +0000[diff] [blame]96
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]97<ul>
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]98<li>Several core LLVM IR classes have migrated to use the
99 '<tt>FOOCLASS::Create(...)</tt>' pattern instead of '<tt>new
100 FOOCLASS(...)</tt>' (e.g. where FOOCLASS=<tt>BasicBlock</tt>). We hope to
101 standardize on <tt>FOOCLASS::Create</tt> for all IR classes in the future,
102 but not all of them have been moved over yet.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]103<li>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to
Dan Gohmanaa4a9462008-06-08 22:57:59 +0000[diff] [blame]104 <a href="http://llvm.org/doxygen/classllvm_1_1IRBuilder.html">IRBuilder</a>.
105 </li>
106<li>MRegisterInfo was renamed to
107 <a href="http://llvm.org/doxygen/classllvm_1_1TargetRegisterInfo.html">
108 TargetRegisterInfo</a>.</li>
109<li>The MappedFile class is gone, please use
110 <a href="http://llvm.org/doxygen/classllvm_1_1MemoryBuffer.html">
111 MemoryBuffer</a> instead.</li>
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]112<li>The '<tt>-enable-eh</tt>' flag to llc has been removed. Now code should
113 encode whether it is safe to omit unwind information for a function by
114 tagging the Function object with the '<tt>nounwind</tt>' attribute.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]115
116</ul>
Chris Lattnercdc44ed2008-02-06 18:00:06 +0000[diff] [blame]117</div>
118
119<!--=========================================================================-->
120<div class="doc_subsection">
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]121<a name="otherprojects">Other LLVM Sub-Projects</a>
122</div>
123
124<div class="doc_text">
Chris Lattnerc75fd522008-06-08 21:58:17 +0000[diff] [blame]125<p>
126The core LLVM 2.3 distribution currently consists of code from the core LLVM
127repository (which roughly contains the LLVM optimizer, code generators and
128supporting tools) and the llvm-gcc repository. In addition to this code, the
129LLVM Project includes other sub-projects that are in development. The two which
130are the most actively developed are the new <a href="#vmkit">vmkit Project</a>
131and the <a href="#clang">Clang Project</a>.
132</p>
133</div>
134
135<!--=========================================================================-->
136<div class="doc_subsubsection">
137<a name="vmkit">vmkit</a>
138</div>
139
140<div class="doc_text">
141<p>
142The "vmkit" project is a new addition to the LLVM family. It is an
143implementation of a JVM and a CLI Virtual Machines (Microsoft .NET is an
144implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
145
146<p>The JVM, called JnJVM, executes real-world applications such as Apache
147projects (e.g. Felix and Tomcat) and the SpecJVM98 benchmark. It uses the GNU
148Classpath project for the base classes. The CLI implementation, called N3, is
149its in early stages but can execute simple applications and the "pnetmark"
150benchmark. It uses the pnetlib project as its core library.</p>
151
152<p>The 'vmkit' VMs compare in performance with industrial and top open-source
153VMs on scientific applications. Besides the JIT, the VMs use many features of
154the LLVM framework, including the standard set of optimizations, atomic
155operations, custom function provider and memory manager for JITed methods, and
156specific virtual machine optimizations. vmkit is not an official part of LLVM
1572.3 release. It is publicly available under the LLVM license and can be
158downloaded from:
159</p>
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]160
161<p>
Chris Lattnerc75fd522008-06-08 21:58:17 +0000[diff] [blame]162<tt>svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit</tt>
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]163</p>
164
165</div>
166
167<!--=========================================================================-->
Chris Lattnerc75fd522008-06-08 21:58:17 +0000[diff] [blame]168<div class="doc_subsubsection">
169<a name="clang">Clang</a>
170</div>
171
172<div class="doc_text">
173
174<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
175a set of new 'LLVM native' front-end technologies for the LLVM optimizer
176and code generator. Clang is continuing to make major strides forward in all
177areas. Its C and Objective-C parsing support is very solid, and the code
178generation support is far enough along to build many C applications. While not
179yet production quality, it is progressing very nicely. In addition, C++
180front-end work has started to make significant progress.</p>
181
182<p>At this point, Clang is most useful if you are interested in source-to-source
183transformations (such as refactoring) and other source-level tools for C and
184Objective-C. Clang now also includes tools for turning C code into pretty HTML,
185and includes a new <a href="http://clang.llvm.org/StaticAnalysis.html">static
Chris Lattnerc57ba6c2008-06-08 23:40:40 +0000[diff] [blame]186analysis tool</a> in development. This tool focuses on automatically finding
Chris Lattnerc75fd522008-06-08 21:58:17 +0000[diff] [blame]187bugs in C and Objective-C code.</p>
188
189</div>
190
191
192<!-- *********************************************************************** -->
193<div class="doc_section">
194 <a name="whatsnew">What's New?</a>
195</div>
196<!-- *********************************************************************** -->
197
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]198<div class="doc_text">
199
200<p>LLVM 2.3 includes a huge number of bug fixes, performance tweaks and minor
201improvements. Some of the major improvements and new features are listed in
202this section.
203</p>
204</div>
205
Chris Lattnerc75fd522008-06-08 21:58:17 +0000[diff] [blame]206<!--=========================================================================-->
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]207<div class="doc_subsection">
Chris Lattnercdc44ed2008-02-06 18:00:06 +0000[diff] [blame]208<a name="majorfeatures">Major New Features</a>
209</div>
210
211<div class="doc_text">
212
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]213<p>LLVM 2.3 includes several major new capabilities:</p>
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]214
215<ul>
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]216<li><p>The biggest change in LLVM 2.3 is Multiple Return Value (MRV) support.
217 MRVs allow LLVM IR to directly represent functions that return multiple
218 values without having to pass them "by reference" in the LLVM IR. This
219 allows a front-end to generate more efficient code, as MRVs are generally
220 returned in registers if a target supports them. See the <a
221 href="LangRef.html#i_getresult">LLVM IR Reference</a> for more details.</p>
222
223 <p>MRVs are fully supported in the LLVM IR, but are not yet fully supported in
224 on all targets. However, it is generally safe to return up to 2 values from
225 a function: most targets should be able to handle at least that. MRV
226 support is a critical requirement for X86-64 ABI support, as X86-64 requires
227 the ability to return multiple registers from functions, and we use MRVs to
228 accomplish this in a direct way.</p></li>
Chris Lattner618a99f2008-06-05 06:57:39 +0000[diff] [blame]229
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]230<li><p>LLVM 2.3 includes a complete reimplementation of the "<tt>llvmc</tt>"
231 tool. It is designed to overcome several problems with the original
232 <tt>llvmc</tt> and to provide a superset of the features of the
233 '<tt>gcc</tt>' driver.</p>
Chris Lattner618a99f2008-06-05 06:57:39 +0000[diff] [blame]234
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]235<p>The main features of <tt>llvmc2</tt> are:
236 <ul>
237 <li>Extended handling of command line options and smart rules for
238 dispatching them to different tools.</li>
239 <li>Flexible (and extensible) rules for defining different tools.</li>
240 <li>The different intermediate steps performed by tools are represented
241 as edges in the abstract graph.</li>
242 <li>The 'language' for driver behavior definition is tablegen and thus
243 it's relatively easy to add new features.</li>
244 <li>The definition of driver is transformed into set of C++ classes, thus
245 no runtime interpretation is needed.</li>
246 </ul></p>
247 </li>
Chris Lattner618a99f2008-06-05 06:57:39 +0000[diff] [blame]248
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]249<li><p>LLVM 2.3 includes a completely rewritten interface for <a
250 href="LinkTimeOptimization.html">Link Time Optimization</a>. This interface
251 is written in C, which allows for easier integration with C code bases, and
252 incorporates improvements we learned about from the first incarnation of the
253 interface.</p></li>
Chris Lattner618a99f2008-06-05 06:57:39 +0000[diff] [blame]254
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]255<li><p>The <a href="tutorial/LangImpl1.html">Kaleidoscope tutorial</a> now
256 includes a "port" of the tutorial that <a
257 href="tutorial/OCamlLangImpl1.html">uses the Ocaml bindings</a> to implement
258 the Kaleidoscope language.</p></li>
Chris Lattner618a99f2008-06-05 06:57:39 +0000[diff] [blame]259
Chris Lattner458e79f2008-02-10 08:18:42 +0000[diff] [blame]260</ul>
261
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]262</div>
263
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]264
265<!--=========================================================================-->
266<div class="doc_subsection">
Chris Lattner625a3d82008-06-08 21:34:41 +0000[diff] [blame]267<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]268</div>
269
270<div class="doc_text">
271
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]272<p>LLVM 2.3 fully supports the llvm-gcc 4.2 front-end, and includes support
273for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]274
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]275<p>
276<ul>
277<li>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C
278front-end. Objective-C now works very well on Mac OS/X.</li>
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]279
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]280<li>Fortran EQUIVALENCEs are now supported by the gfortran front-end.</li>
Chris Lattnerc75fd522008-06-08 21:58:17 +0000[diff] [blame]281
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]282<li>llvm-gcc 4.2 includes many other fixes which improve conformance with the
283relevant parts of the GCC testsuite.</li>
284
285</ul></p>
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]286
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]287</div>
288
289
Chris Lattner0a1fd102007-09-21 03:54:09 +0000[diff] [blame]290<!--=========================================================================-->
291<div class="doc_subsection">
Chris Lattnerdd6acc02008-02-10 08:17:19 +0000[diff] [blame]292<a name="coreimprovements">LLVM Core Improvements</a>
293</div>
294
295<div class="doc_text">
296<p>New features include:
297</p>
298
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]299<ul>
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]300<li>LLVM IR now directly represents "common" linkage, instead of representing it
301as a form of weak linkage.</li>
302
303<li>LLVM IR now has support for atomic operations, and this functionality can
304be accessed through the llvm-gcc "__sync_synchronize",
305"__sync_val_compare_and_swap", and related builtins. Support for atomics are
306available in the Alpha, X86, X86-64, and PowerPC backends.</li>
307
308<li>The C and Ocaml bindings have extended to cover pass managers, several
309transformation passes, iteration over the LLVM IR, target data, and parameter
310attribute lists.</li>
Chris Lattnerdd6acc02008-02-10 08:17:19 +0000[diff] [blame]311</ul>
312
313</div>
314
315<!--=========================================================================-->
316<div class="doc_subsection">
Chris Lattner2b8a52e2008-02-10 07:46:44 +0000[diff] [blame]317<a name="optimizer">Optimizer Improvements</a>
318</div>
319
320<div class="doc_text">
321
Chris Lattnerdd6acc02008-02-10 08:17:19 +0000[diff] [blame]322<p>In addition to a huge array of bug fixes and minor performance tweaks, the
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]323LLVM 2.3 optimizers support a few major enhancements:</p>
Chris Lattner2b8a52e2008-02-10 07:46:44 +0000[diff] [blame]324
325<ul>
326
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]327<li><p>Loop index set splitting on by default.
328This transformation hoists conditions from loop bodies and reduces a loop's
329iteration space to improve performance. For example,</p>
330
Devang Patel33aac002008-06-05 21:44:00 +0000[diff] [blame]331<pre>
Chris Lattner94fd4472008-06-08 20:25:30 +0000[diff] [blame]332for (i = LB; i &lt; UB; ++i)
333 if (i &lt;= NV)
Devang Patel33aac002008-06-05 21:44:00 +0000[diff] [blame]334 LOOP_BODY
335</pre>
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]336
337<p>is transformed into:</p>
338
Devang Patel33aac002008-06-05 21:44:00 +0000[diff] [blame]339<pre>
340NUB = min(NV+1, UB)
Chris Lattner94fd4472008-06-08 20:25:30 +0000[diff] [blame]341for (i = LB; i &lt; NUB; ++i)
Devang Patel33aac002008-06-05 21:44:00 +0000[diff] [blame]342 LOOP_BODY
343</pre>
344</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]345
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]346<li>LLVM now includes a new <tt>memcpy</tt> optimization pass which removes
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]347dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and performs
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]348return slot optimization. The LLVM optimizer now notices long sequences of
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]349consecutive stores and merges them into <tt>memcpy</tt>'s where profitable.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]350
Gabor Greif80ae8a72008-06-05 18:39:01 +0000[diff] [blame]351<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
352<tt>memset</tt> is now more aggressive.</li>
Owen Andersonf7647e42008-06-06 16:23:15 +0000[diff] [blame]353
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]354<li>The Aggressive Dead Code Elimination (ADCE) optimization has been rewritten
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]355to make it both faster and safer in the presence of code containing infinite
356loops. Some of its prior functionality has been factored out into the loop
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]357deletion pass, which <em>is</em> safe for infinite loops. The new ADCE pass is
358no longer based on control dependence, making it run faster.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]359
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]360<li>The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm
361 functions for C-based languages, has been rewritten to be a FunctionPass
362 instead a ModulePass. This allows it to be run more often and to be
363 included at -O1 in llvm-gcc. It was also extended to include more
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]364 optimizations and several corner case bugs were fixed.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]365
Duncan Sands0bc15262008-06-08 19:38:43 +0000[diff] [blame]366<li>LLVM now includes a simple 'Jump Threading' pass, which attempts to simplify
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]367 conditional branches using information about predecessor blocks, simplifying
Chris Lattnerb076b002008-06-08 21:19:07 +0000[diff] [blame]368 the control flow graph. This pass is pretty basic at this point, but
369 catches some important cases and provides a foundation to build on.</li>
370
371<li>Several corner case bugs which could lead to deleting volatile memory
372 accesses have been fixed.</li>
Chris Lattnerb7bc2aa2008-06-08 22:59:35 +0000[diff] [blame]373
374<li>Several optimizations have been sped up, leading to faster code generation
375 with the same code quality.</li>
376
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]377</ul>
378
379</div>
380
381<!--=========================================================================-->
382<div class="doc_subsection">
383<a name="codegen">Code Generator Improvements</a>
384</div>
385
386<div class="doc_text">
387
388<p>We put a significant amount of work into the code generator infrastructure,
389which allows us to implement more aggressive algorithms and make it run
390faster:</p>
391
392<ul>
Dan Gohman8709a8062008-06-08 22:49:27 +0000[diff] [blame]393<li>The code generator now has support for carrying information about memory
394 references throughout the entire code generation process, via the
395 <a href="http://llvm.org/doxygen/classllvm_1_1MachineMemOperand.html">
396 MachineMemOperand</a> class. In the future this will be used to improve
397 both pre-pass and post-pass scheduling, and to improve compiler-debugging
398 output.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]399
Dan Gohmanaa4a9462008-06-08 22:57:59 +0000[diff] [blame]400<li>The target-independent code generator infrastructure now uses LLVM's
401 <a href="http://llvm.org/doxygen/classllvm_1_1APInt.html">APInt</a>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]402 class to handle integer values, which allows it to support integer types
Chris Lattnered716052008-06-08 23:06:47 +0000[diff] [blame]403 larger than 64 bits (for example i128). Note that support for such types is
404 also dependent on target-specific support. Use of APInt is also a step
405 toward support for non-power-of-2 integer sizes.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]406
Chris Lattnerb076b002008-06-08 21:19:07 +0000[diff] [blame]407<li>LLVM 2.3 includes several compile time speedups for code with large basic
Dan Gohmane7067242008-06-08 22:44:43 +0000[diff] [blame]408 blocks, particularly in the instruction selection phase, register
409 allocation, scheduling, and tail merging/jump threading.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]410
Chris Lattnered716052008-06-08 23:06:47 +0000[diff] [blame]411<li>LLVM 2.3 includes several improvements which make llc's
412 <tt>--view-sunit-dags</tt> visualization of scheduling dependency graphs
413 easier to understand.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]414
415<li>The code generator allows targets to write patterns that generate subreg
416 references directly in .td files now.</li>
417
418<li><tt>memcpy</tt> lowering in the backend is more aggressive, particularly for
419 <tt>memcpy</tt> calls introduced by the code generator when handling
420 pass-by-value structure argument copies.</li>
Chris Lattnerb076b002008-06-08 21:19:07 +0000[diff] [blame]421
422<li>Inline assembly with multiple register results now returns those results
423 directly in the appropriate registers, rather than going through memory.
424 Inline assembly that uses constraints like "ir" with immediates now use the
425 'i' form when possible instead of always loading the value in a register.
426 This saves an instruction and reduces register use.</li>
427
Chris Lattner5baa4132008-06-09 04:00:08 +0000[diff] [blame^]428<li>Added support for PIC/GOT style <a
429 href="CodeGenerator.html#tailcallopt">tail calls</a> on X86/32 and initial
430 support for tail calls on PowerPC 32 (it may also work on PowerPC 64 but is
431 not thoroughly tested).</li>
Chris Lattner0a1fd102007-09-21 03:54:09 +0000[diff] [blame]432</ul>
433
434</div>
435
436
437<!--=========================================================================-->
438<div class="doc_subsection">
Chris Lattner6cb64032008-06-05 08:02:49 +0000[diff] [blame]439<a name="x86specific">X86/X86-64 Specific Improvements</a>
Chris Lattner0a1fd102007-09-21 03:54:09 +0000[diff] [blame]440</div>
Chris Lattner727c3742007-05-18 06:33:02 +0000[diff] [blame]441
Chris Lattner89e761c2006-04-18 06:32:08 +0000[diff] [blame]442<div class="doc_text">
Chris Lattnerdd6acc02008-02-10 08:17:19 +0000[diff] [blame]443<p>New target-specific features include:
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]444</p>
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]445
446<ul>
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]447<li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the
Gabor Greif80ae8a72008-06-05 18:39:01 +0000[diff] [blame]448 area of passing and returning structures by value. llvm-gcc compiled code
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]449 now interoperates very well on X86-64 systems with other compilers.</li>
450
Duncan Sands0bc15262008-06-08 19:38:43 +0000[diff] [blame]451<li>Support for Win64 was added. This includes code generation itself, JIT
Chris Lattnered716052008-06-08 23:06:47 +0000[diff] [blame]452 support, and necessary changes to llvm-gcc.</li>
Anton Korobeynikov486c7d32008-06-08 10:24:13 +0000[diff] [blame]453
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]454<li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]455 the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins. Various
456 generic vector operations (insert/extract/shuffle) are much more efficient
457 when SSE 4.1 is enabled. The JIT automatically takes advantage of these
458 instructions, but llvm-gcc must be explicitly told to use them, e.g. with
459 <tt>-march=penryn</tt>.</li>
Anton Korobeynikov486c7d32008-06-08 10:24:13 +0000[diff] [blame]460
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]461<li>The X86 backend now does a number of optimizations that aim to avoid
462 converting numbers back and forth from SSE registers to the X87 floating
Chris Lattnered716052008-06-08 23:06:47 +0000[diff] [blame]463 point stack. This is important because most X86 ABIs require return values
464 to be on the X87 Floating Point stack, but most CPUs prefer computation in
465 the SSE units.</li>
Anton Korobeynikov486c7d32008-06-08 10:24:13 +0000[diff] [blame]466
Chris Lattner618a99f2008-06-05 06:57:39 +0000[diff] [blame]467<li>The X86 backend supports stack realignment, which is particularly useful for
Chris Lattnered716052008-06-08 23:06:47 +0000[diff] [blame]468 vector code on OS's without 16-byte aligned stacks, such as Linux and
469 Windows.</li>
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]470
471<li>The X86 backend now supports the "sseregparm" options in GCC, which allow
472 functions to be tagged as passing floating point values in SSE
473 registers.</li>
474
475<li>Trampolines (taking the address of a nested function) now work on
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]476 Linux/X86-64.</li>
Anton Korobeynikov486c7d32008-06-08 10:24:13 +0000[diff] [blame]477
Chris Lattner6cb64032008-06-05 08:02:49 +0000[diff] [blame]478<li><tt>__builtin_prefetch</tt> is now compiled into the appropriate prefetch
479 instructions instead of being ignored.</li>
Chris Lattnerb7112222008-06-05 06:25:56 +0000[diff] [blame]480
Chris Lattnered716052008-06-08 23:06:47 +0000[diff] [blame]481<li>128-bit integers are now supported on X86-64 targets. This can be used
482 through <tt>__attribute__((TImode))</tt> in llvm-gcc.</li>
Dan Gohmanb0ec18b2008-06-05 16:15:39 +0000[diff] [blame]483
Chris Lattnered716052008-06-08 23:06:47 +0000[diff] [blame]484<li>The register allocator can now rematerialize PIC-base computations, which is
485 an important optimization for register use.</li>
Chris Lattner7795ea92008-06-08 02:45:07 +0000[diff] [blame]486
Chris Lattnerb076b002008-06-08 21:19:07 +0000[diff] [blame]487<li>The "t" and "f" inline assembly constraints for the X87 floating point stack
488 now work. However, the "u" constraint is still not fully supported.</li>
489
Chris Lattner8ce1ba42007-05-17 21:41:31 +0000[diff] [blame]490</ul>
Chris Lattner0a1fd102007-09-21 03:54:09 +0000[diff] [blame]491
Chris Lattner8ce1ba42007-05-17 21:41:31 +0000[diff] [blame]492</div>
Chris Lattner72a269f2006-03-03 00:34:26 +0000[diff] [blame]493
Chris Lattner0a1fd102007-09-21 03:54:09 +0000[diff] [blame]494<!--=========================================================================-->
495<div class="doc_subsection">
Chris Lattner6cb64032008-06-05 08:02:49 +0000[diff] [blame]496<a name="targetspecific">Other Target Specific Improvements</a>
497</div>
498
499<div class="doc_text">
500<p>New target-specific features include:
501</p>
502
503<ul>
Gabor Greif80ae8a72008-06-05 18:39:01 +0000[diff] [blame]504<li>The LLVM C backend now supports vector code.</li>
Chris Lattnered716052008-06-08 23:06:47 +0000[diff] [blame]505<li>The Cell SPU backend includes a number of improvements. It generates better
506 code and its stability/completeness is improving.</li>
Chris Lattner6cb64032008-06-05 08:02:49 +0000[diff] [blame]507</ul>
508
509</div>
510
511
512
513<!--=========================================================================-->
514<div class="doc_subsection">
Chris Lattner0a1fd102007-09-21 03:54:09 +0000[diff] [blame]515<a name="otherimprovements">Other Improvements</a>
516</div>
517
518<div class="doc_text">
519<p>New features include:
520</p>
521
522<ul>
Chris Lattner618a99f2008-06-05 06:57:39 +0000[diff] [blame]523<li>LLVM now builds with GCC 4.3.</li>
Chris Lattnerb076b002008-06-08 21:19:07 +0000[diff] [blame]524<li>Bugpoint now supports running custom scripts (with the <tt>-run-custom</tt>
525 option) to determine how to execute the command and whether it is making
526 forward process.</li>
Chris Lattner0a1fd102007-09-21 03:54:09 +0000[diff] [blame]527</ul>
528
529</div>
Chris Lattner72a269f2006-03-03 00:34:26 +0000[diff] [blame]530
Chris Lattner62495762003-10-02 16:38:05 +0000[diff] [blame]531<!-- *********************************************************************** -->
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]532<div class="doc_section">
533 <a name="portability">Portability and Supported Platforms</a>
534</div>
Chris Lattner62495762003-10-02 16:38:05 +0000[diff] [blame]535<!-- *********************************************************************** -->
536
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]537<div class="doc_text">
538
John Criswell64307722004-12-08 20:35:47 +0000[diff] [blame]539<p>LLVM is known to work on the following platforms:</p>
Chris Lattner2c7b0872004-06-01 18:22:41 +0000[diff] [blame]540
541<ul>
Gabor Greif80ae8a72008-06-05 18:39:01 +0000[diff] [blame]542<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Reid Spencer9803b402005-05-17 02:47:27 +0000[diff] [blame]543 (and probably other unix-like systems).</li>
Chris Lattner7422bce2008-02-06 06:30:34 +0000[diff] [blame]544<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]545 64-bit modes.</li>
Chris Lattnercdc44ed2008-02-06 18:00:06 +0000[diff] [blame]546<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Chris Lattnerbee7b322007-05-23 04:39:32 +0000[diff] [blame]547<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
548 support is available for native builds with Visual C++).</li>
Gabor Greif80ae8a72008-06-05 18:39:01 +0000[diff] [blame]549<li>Sun UltraSPARC workstations running Solaris 10.</li>
John Criswelld5234922005-05-13 20:28:15 +0000[diff] [blame]550<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif80ae8a72008-06-05 18:39:01 +0000[diff] [blame]551<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Chris Lattner2c7b0872004-06-01 18:22:41 +0000[diff] [blame]552</ul>
553
Chris Lattner618a99f2008-06-05 06:57:39 +0000[diff] [blame]554<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Brian Gaekee3e557e2004-05-09 05:28:35 +0000[diff] [blame]555to the machine and operating system on which it is built. However, minor
556porting may be required to get LLVM to work on new platforms. We welcome your
557portability patches and reports of successful builds or error messages.</p>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]558
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]559</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]560
561<!-- *********************************************************************** -->
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]562<div class="doc_section">
563 <a name="knownproblems">Known Problems</a>
564</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]565<!-- *********************************************************************** -->
566
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]567<div class="doc_text">
568
569<p>This section contains all known problems with the LLVM system, listed by
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]570component. As new problems are discovered, they will be added to these
Chris Lattnerb84f3322003-12-12 21:22:16 +0000[diff] [blame]571sections. If you run into a problem, please check the <a
Chris Lattnera69595e2005-10-29 07:07:09 +0000[diff] [blame]572href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
Chris Lattnerb84f3322003-12-12 21:22:16 +0000[diff] [blame]573there isn't already one.</p>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]574
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]575</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]576
Chris Lattnerb911de42004-03-14 02:03:02 +0000[diff] [blame]577<!-- ======================================================================= -->
578<div class="doc_subsection">
579 <a name="experimental">Experimental features included with this release</a>
580</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]581
Chris Lattnerb911de42004-03-14 02:03:02 +0000[diff] [blame]582<div class="doc_text">
583
Misha Brukmanfa50a222004-05-12 21:46:05 +0000[diff] [blame]584<p>The following components of this LLVM release are either untested, known to
585be broken or unreliable, or are in early development. These components should
586not be relied on, and bugs should not be filed against them, but they may be
587useful to some people. In particular, if you would like to work on one of these
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]588components, please contact us on the <a
589href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Chris Lattnerb911de42004-03-14 02:03:02 +0000[diff] [blame]590
591<ul>
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]592<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]593<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
Chris Lattner7422bce2008-02-06 06:30:34 +0000[diff] [blame]594 value for this option.</li>
Chris Lattnerb911de42004-03-14 02:03:02 +0000[diff] [blame]595</ul>
596
597</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]598
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]599<!-- ======================================================================= -->
600<div class="doc_subsection">
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]601 <a name="x86-be">Known problems with the X86 back-end</a>
John Criswell3bdbd302005-11-08 21:11:33 +0000[diff] [blame]602</div>
603
604<div class="doc_text">
605
606<ul>
Anton Korobeynikov486c7d32008-06-08 10:24:13 +0000[diff] [blame]607 <li>The X86 backend does not yet support
608 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
609 floating point stack</a>. It supports the 'f' and 't' constraints, but not
610 'u'.</li>
Chris Lattnerb076b002008-06-08 21:19:07 +0000[diff] [blame]611 <li>The X86 backend generates inefficient floating point code when configured
612 to generate code for systems that don't have SSE2.</li>
Duncan Sands0bc15262008-06-08 19:38:43 +0000[diff] [blame]613 <li>Win64 code generation wasn't widely tested. Everything should work, but we
Anton Korobeynikov486c7d32008-06-08 10:24:13 +0000[diff] [blame]614 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
615 currently due
616 to <a href="http://llvm.org/PR2255">several</a>
Chris Lattner54d12102008-06-08 23:12:47 +0000[diff] [blame]617 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
618 'u' inline assembly constraint and X87 floating point inline assembly.</li>
Dan Gohman721b3722008-06-08 23:05:11 +0000[diff] [blame]619 <li>The X86-64 backend does not yet support position-independent code (PIC)
620 generation on Linux targets.</li>
621 <li>The X86-64 backend does not yet support the LLVM IR instruction
622 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
623 argument constructs on X86-64 by lowering them manually.</li>
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]624</ul>
625
626</div>
627
628<!-- ======================================================================= -->
629<div class="doc_subsection">
630 <a name="ppc-be">Known problems with the PowerPC back-end</a>
631</div>
632
633<div class="doc_text">
634
635<ul>
Nicolas Geoffray77d99502007-05-15 09:21:28 +0000[diff] [blame]636<li>The Linux PPC32/ABI support needs testing for the interpreter and static
Chris Lattnerbee7b322007-05-23 04:39:32 +0000[diff] [blame]637compilation, and lacks support for debug information.</li>
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]638</ul>
639
640</div>
641
642<!-- ======================================================================= -->
643<div class="doc_subsection">
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]644 <a name="arm-be">Known problems with the ARM back-end</a>
645</div>
646
647<div class="doc_text">
648
649<ul>
Chris Lattnerbee7b322007-05-23 04:39:32 +0000[diff] [blame]650<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sands47fc0a22007-09-26 15:59:54 +0000[diff] [blame]651processors, thumb programs can crash or produce wrong
Chris Lattnerbee7b322007-05-23 04:39:32 +0000[diff] [blame]652results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]653<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
654</li>
Chris Lattnerb076b002008-06-08 21:19:07 +0000[diff] [blame]655<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
656 execute
Chris Lattnerbee7b322007-05-23 04:39:32 +0000[diff] [blame]657programs compiled with LLVM. Please use more recent versions of QEMU.</li>
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]658</ul>
659
660</div>
661
662<!-- ======================================================================= -->
663<div class="doc_subsection">
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]664 <a name="sparc-be">Known problems with the SPARC back-end</a>
665</div>
666
667<div class="doc_text">
668
669<ul>
670<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
671 support the 64-bit SPARC ABI (-m64).</li>
672</ul>
673
674</div>
675
676<!-- ======================================================================= -->
677<div class="doc_subsection">
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]678 <a name="alpha-be">Known problems with the Alpha back-end</a>
679</div>
680
681<div class="doc_text">
682
683<ul>
684
685<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
686appropriate nops inserted to ensure restartability.</li>
687
John Criswell3bdbd302005-11-08 21:11:33 +0000[diff] [blame]688</ul>
689</div>
690
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]691<!-- ======================================================================= -->
692<div class="doc_subsection">
693 <a name="ia64-be">Known problems with the IA64 back-end</a>
694</div>
695
696<div class="doc_text">
697
698<ul>
Chris Lattner54d12102008-06-08 23:12:47 +0000[diff] [blame]699<li>The Itanium backend is highly experimental, and has a number of known
700 issues. We are looking for a maintainer for the Itanium backend. If you
701 are interested, please contact the llvmdev mailing list.</li>
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]702</ul>
703
704</div>
705
706<!-- ======================================================================= -->
707<div class="doc_subsection">
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]708 <a name="c-be">Known problems with the C back-end</a>
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]709</div>
710
711<div class="doc_text">
712
713<ul>
Chris Lattnera1a4c9a2008-06-05 06:35:40 +0000[diff] [blame]714<li><a href="http://llvm.org/PR802">The C backend has only basic support for
715 inline assembly code</a>.</li>
Chris Lattner8e061162007-09-26 06:01:35 +0000[diff] [blame]716<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
717 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]718 C++ code compiled with llc or native compilers.</li>
Duncan Sandse09506a2008-02-10 13:40:55 +0000[diff] [blame]719<li>The C backend does not support all exception handling constructs.</li>
Chris Lattnerb81f10e2006-11-18 07:51:14 +0000[diff] [blame]720</ul>
721
722</div>
John Criswell3bdbd302005-11-08 21:11:33 +0000[diff] [blame]723
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]724
725<!-- ======================================================================= -->
726<div class="doc_subsection">
Chris Lattnera1a4c9a2008-06-05 06:35:40 +0000[diff] [blame]727 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]728</div>
Chris Lattner178f3db2003-10-02 05:07:23 +0000[diff] [blame]729
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]730<div class="doc_text">
Chris Lattner72a269f2006-03-03 00:34:26 +0000[diff] [blame]731
Chris Lattnercdc44ed2008-02-06 18:00:06 +0000[diff] [blame]732<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
733Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]734llvmdev mailing list if you are interested.</p>
Chris Lattner44124232006-08-08 17:27:28 +0000[diff] [blame]735
Chris Lattnera1a4c9a2008-06-05 06:35:40 +0000[diff] [blame]736<p>The only major language feature of GCC not supported by llvm-gcc is
737 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
738 are only supported on some targets. For example, trampolines are only
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]739 supported on some targets (these are used when you take the address of a
740 nested function).</p>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]741
Chris Lattnera1a4c9a2008-06-05 06:35:40 +0000[diff] [blame]742<p>If you run into GCC extensions which are not supported, please let us know.
743</p>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]744
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]745</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]746
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]747<!-- ======================================================================= -->
748<div class="doc_subsection">
Chris Lattnera1a4c9a2008-06-05 06:35:40 +0000[diff] [blame]749 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]750</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]751
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]752<div class="doc_text">
753
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]754<p>The C++ front-end is considered to be fully
Chris Lattnerb5bb5972004-12-07 08:04:13 +0000[diff] [blame]755tested and works for a number of non-trivial programs, including LLVM
Chris Lattner97beb512007-05-14 06:56:09 +0000[diff] [blame]756itself, Qt, Mozilla, etc.</p>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]757
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]758<ul>
Chris Lattnera1a4c9a2008-06-05 06:35:40 +0000[diff] [blame]759<li>Exception handling works well on the X86 and PowerPC targets, including
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]760X86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is
761supported on X86-64 linux, but that is disabled by default in this release.</li>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]762</ul>
Chris Lattner46ecf612003-10-07 22:14:37 +0000[diff] [blame]763
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]764</div>
765
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]766
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]767<!-- ======================================================================= -->
768<div class="doc_subsection">
Chris Lattnera1a4c9a2008-06-05 06:35:40 +0000[diff] [blame]769 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]770</div>
771
772<div class="doc_text">
773The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
774technology and problems should be expected.
775<ul>
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]776<li>The Ada front-end currently only builds on X86-32. This is mainly due
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]777to lack of trampoline support (pointers to nested functions) on other platforms,
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]778however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]779which does support trampolines.</li>
780<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
781Workaround: configure with --disable-bootstrap.</li>
782<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
Duncan Sands56448462008-06-08 20:18:35 +0000[diff] [blame]783fail (c380004 also fails with gcc-4.2 mainline). When built at -O3, the
784<a href="http://llvm.org/PR2421">cxg2021</a> ACATS test also fails.</li>
785<li>Some gcc specific Ada tests continue to crash the compiler. The testsuite
786reports most tests as having failed even though they pass.</li>
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]787<li>The -E binder option (exception backtraces)
788<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
789crashing if an exception is raised. Workaround: do not use -E.</li>
790<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
791or finish at a non-byte offset</a> in a record. Workaround: do not pack records
792or use representation clauses that result in a field of a non-discrete type
793starting or finishing in the middle of a byte.</li>
Chris Lattnerb076b002008-06-08 21:19:07 +0000[diff] [blame]794<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
795'main' as generated by the Ada binder to be invalid</a>.
796Workaround: hand edit the file to use pointers for <tt>argv</tt> and
797<tt>envp</tt> rather than integers.</li>
798<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
799ignored</a>.</li>
Chris Lattnere38ac152008-02-12 06:29:45 +0000[diff] [blame]800</ul>
801</div>
802
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]803<!-- *********************************************************************** -->
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]804<div class="doc_section">
805 <a name="additionalinfo">Additional Information</a>
806</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]807<!-- *********************************************************************** -->
808
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]809<div class="doc_text">
810
Chris Lattnercb5596d2005-05-16 17:13:10 +0000[diff] [blame]811<p>A wide variety of additional information is available on the <a
Chris Lattnere0c1df42007-05-18 00:44:29 +0000[diff] [blame]812href="http://llvm.org">LLVM web page</a>, in particular in the <a
813href="http://llvm.org/docs/">documentation</a> section. The web page also
Reid Spencerc7f87f22007-07-09 08:04:31 +0000[diff] [blame]814contains versions of the API documentation which is up-to-date with the
815Subversion version of the source code.
Misha Brukman96158092005-03-30 19:14:24 +0000[diff] [blame]816You can access versions of these documents specific to this release by going
817into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]818
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]819<p>If you have any questions or comments about LLVM, please feel free to contact
Chris Lattnera69595e2005-10-29 07:07:09 +0000[diff] [blame]820us via the <a href="http://llvm.org/docs/#maillist"> mailing
Chris Lattnerb84f3322003-12-12 21:22:16 +0000[diff] [blame]821lists</a>.</p>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]822
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]823</div>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]824
825<!-- *********************************************************************** -->
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]826
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]827<hr>
Misha Brukman68aab3b2003-11-22 01:23:39 +0000[diff] [blame]828<address>
Misha Brukman8834af92003-12-21 22:53:21 +0000[diff] [blame]829 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman68aab3b2003-11-22 01:23:39 +0000[diff] [blame]830 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
831 <a href="http://validator.w3.org/check/referer"><img
Chris Lattner458e79f2008-02-10 08:18:42 +0000[diff] [blame]832 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
Misha Brukman68aab3b2003-11-22 01:23:39 +0000[diff] [blame]833
Chris Lattnere0c1df42007-05-18 00:44:29 +0000[diff] [blame]834 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]835 Last modified: $Date$
Misha Brukman68aab3b2003-11-22 01:23:39 +0000[diff] [blame]836</address>
Chris Lattner3d482502003-10-02 04:57:28 +0000[diff] [blame]837
Misha Brukman80731b92003-11-22 00:38:41 +0000[diff] [blame]838</body>
839</html>