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Chris Lattner84977642007-09-21 03:54:09 +00007 <title>LLVM 2.1 Release Notes</title>
Misha Brukman500bc302003-11-22 00:38:41 +00008</head>
9<body>
Chris Lattner79c3fe12003-10-02 04:57:28 +000010
Chris Lattner84977642007-09-21 03:54:09 +000011<div class="doc_title">LLVM 2.1 Release Notes</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000012
13<ol>
Misha Brukman500bc302003-11-22 00:38:41 +000014 <li><a href="#intro">Introduction</a></li>
15 <li><a href="#whatsnew">What's New?</a></li>
Chris Lattner4b538b92004-04-30 22:17:12 +000016 <li><a href="GettingStarted.html">Installation Instructions</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +000017 <li><a href="#portability">Portability and Supported Platforms</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +000018 <li><a href="#knownproblems">Known Problems</a>
Misha Brukman500bc302003-11-22 00:38:41 +000019 <li><a href="#additionalinfo">Additional Information</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +000020</ol>
21
Chris Lattner7911ce22004-05-23 21:07:27 +000022<div class="doc_author">
Chris Lattnerc463b272005-10-29 07:07:09 +000023 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
Misha Brukman500bc302003-11-22 00:38:41 +000024</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000025
26<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +000027<div class="doc_section">
28 <a name="intro">Introduction</a>
29</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000030<!-- *********************************************************************** -->
31
Misha Brukman500bc302003-11-22 00:38:41 +000032<div class="doc_text">
33
34<p>This document contains the release notes for the LLVM compiler
Chris Lattner84977642007-09-21 03:54:09 +000035infrastructure, release 2.1. Here we describe the status of LLVM, including
Chris Lattner57a460e2007-05-23 04:39:32 +000036major improvements from the previous release and any known problems. All LLVM
Chris Lattnercaf06342007-05-09 04:58:11 +000037releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
Chris Lattner57a460e2007-05-23 04:39:32 +000038releases web site</a>.</p>
Chris Lattner19092612003-10-02 16:38:05 +000039
Chris Lattner7506b1d2004-12-07 08:04:13 +000040<p>For more information about LLVM, including information about the latest
Chris Lattnerc463b272005-10-29 07:07:09 +000041release, please check out the <a href="http://llvm.org/">main LLVM
Chris Lattner47ad72c2003-10-07 21:38:31 +000042web site</a>. If you have questions or comments, the <a
43href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
Misha Brukman500bc302003-11-22 00:38:41 +000044list</a> is a good place to send them.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +000045
Reid Spencer669ed452007-07-09 08:04:31 +000046<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattner84977642007-09-21 03:54:09 +000047main LLVM web page, this document applies to the <i>next</i> release, not the
48current one. To see the release notes for a specific releases, please see the
49<a href="http://llvm.org/releases/">releases page</a>.</p>
Misha Brukman500bc302003-11-22 00:38:41 +000050
51</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000052
53<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +000054<div class="doc_section">
55 <a name="whatsnew">What's New?</a>
56</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000057<!-- *********************************************************************** -->
58
Misha Brukman500bc302003-11-22 00:38:41 +000059<div class="doc_text">
60
Chris Lattner84977642007-09-21 03:54:09 +000061<p>This is the twelfth public release of the LLVM Compiler Infrastructure.
62It includes many features and refinements from LLVM 2.0.</p>
Chris Lattnera5099962003-12-06 20:22:41 +000063
Chris Lattner80453c92004-05-24 04:50:25 +000064</div>
65
Chris Lattnera5099962003-12-06 20:22:41 +000066<!--=========================================================================-->
Chris Lattner8a458762005-05-15 05:44:51 +000067<div class="doc_subsection">
Chris Lattner84977642007-09-21 03:54:09 +000068<a name="frontends">New Frontends</a>
Chris Lattner44c933e2006-04-18 06:18:36 +000069</div>
70
Chris Lattnerf3e5bc62007-05-14 06:56:09 +000071<div class="doc_text">
Chris Lattner60893e52007-05-18 06:33:02 +000072
Chris Lattner84977642007-09-21 03:54:09 +000073<p>LLVM 2.1 brings two new beta C front-ends. First, Duncan, Anton and Devang
Devang Patelf7a4e2a2007-09-21 18:02:24 +000074has started syncing up llvm-gcc with GCC 4.2, yielding "llvm-gcc 4.2" (creative,
Chris Lattner84977642007-09-21 03:54:09 +000075huh?). llvm-gcc 4.2 has the promise to bring much better FORTRAN and Ada
76support to LLVM as well as features like atomic builtins, OpenMP, and many other
77things. Check it out!</p>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +000078
Chris Lattner84977642007-09-21 03:54:09 +000079<p>Second, LLVM now includes its own native C and Objective-C front-end (C++ is
80in progress, but is not very far along) code named "<a
81href="http://clang.llvm.org/">clang</a>". This front-end has a number of great
82features, primarily aimed at source-level analysis and speeding up compile-time.
83At this point though, the LLVM Code Generator component is still very early in
84development, so it's mostly useful for people looking to build source-level
85analysis tools or source-to-source translators.</p>
Chris Lattner60893e52007-05-18 06:33:02 +000086
Chris Lattnerf3e5bc62007-05-14 06:56:09 +000087</div>
88
Chris Lattner84977642007-09-21 03:54:09 +000089<!--=========================================================================-->
90<div class="doc_subsection">
91<a name="optimizer">Optimizer Improvements</a>
92</div>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +000093
Chris Lattnerf3e5bc62007-05-14 06:56:09 +000094<div class="doc_text">
Chris Lattner84977642007-09-21 03:54:09 +000095
96<p>Some of the most noticable improvements this release have been in the
97optimizer, speeding it up and making it more aggressive</p>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +000098
99<ul>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000100
Owen Anderson50fd0002007-09-25 02:10:58 +0000101<li>Owen Anderson wrote the new MemoryDependenceAnalysis pass, which provides
102 a lazy, caching layer on top of alias analysis. He then used it to rewrite
103 DeadStoreElimination which resulted in significantly better compile time in
104 common cases, </li>
105<li>Owen implemented the new GVN pass, which is also based on
106 MemoryDependenceAnalysis. This pass replaces GCSE/LoadVN in the standard
107 set of passes, providing more aggressive optimization at a some-what
108 improved compile-time cost.</li>
109<li>Owen implemented GVN-PRE, a partial redundancy elimination algorithm that
110 shares some details with the new GVN pass. It is still in need of compile
111 time tuning, and is not turned on by default.</li>
Chris Lattner84977642007-09-21 03:54:09 +0000112<li>Devang merged ETForest and DomTree into a single easier to use data
113structure.</li>
114<li>Nick Lewycky improved loop trip count analysis to handle many more common
115cases.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000116
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000117</ul>
Chris Lattner84977642007-09-21 03:54:09 +0000118
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000119</div>
120
Chris Lattner84977642007-09-21 03:54:09 +0000121<!--=========================================================================-->
122<div class="doc_subsection">
123<a name="codegen">Code Generator Improvements</a>
124</div>
125
126<div class="doc_text">
127
Chris Lattner84977642007-09-21 03:54:09 +0000128<ul>
129
130<li>Dale finished up the Tail Merging optimization in the code generator,
131enabling it by default. This produces smaller code that is also faster in some
132cases.</li>
133
134<li>Dan Gohman changed the way we represent vectors before legalization,
135significantly simplifying the SelectionDAG representation for these and making
136the code generator faster for vector code.</li>
137
Chris Lattner0d767892007-09-21 17:43:52 +0000138<li>Evan remat rewrite (coalesced intervals + folding of remat'd loads) and
Chris Lattner84977642007-09-21 03:54:09 +0000139live intervals improvements.</li>
140
141<li>Dan Gohman contributed support for better alignment and volatility handling
142in the code generator, and significantly enhanced alignment analysis for SSE
143load/store instructions.</li>
144
145<li>Christopher Lamb virtual register sub-register support, better truncates and
146extends on X86.</li>
147
148<li>Duraid Madina contributed a new "bigblock" register allocator, and Roman
149Levenstein contributed several big improvements. BigBlock is optimized for code
150that uses very large basic blocks. It is slightly slower than the "local"
151allocator, but produces much better code.</li>
152
Chris Lattner0d767892007-09-21 17:43:52 +0000153<li>David Greene refactored the register allocator to split coalescing out from
154allocation, making coalescers pluggable.</li>
Chris Lattner84977642007-09-21 03:54:09 +0000155
156</ul>
157
158</div>
159
160
161<!--=========================================================================-->
162<div class="doc_subsection">
163<a name="targetspecific">Target Specific Improvements</a>
164</div>
Chris Lattner60893e52007-05-18 06:33:02 +0000165
Chris Lattner738bd302006-04-18 06:32:08 +0000166<div class="doc_text">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000167<p>New features include:
168</p>
Chris Lattner26299222006-11-18 07:51:14 +0000169
170<ul>
Chris Lattner84977642007-09-21 03:54:09 +0000171<li>Bruno Cardoso Lopes contributed initial MIPS support.</li>
172<li>Bill Wendling added SSSE3 support.</li>
173<li>New Target independent if converter, ARM uses it so far</li>
174<li>Nicholas Geoffray contributed improved linux/ppc ABI and JIT support.</li>
175<li>Dale Johannesen rewrote handling of 32-bit float values in the X86 backend
176when using the floating point stack, fixing several nasty bugs.</li>
177<li>Dan contributed rematerialization support for the X86 backend.</li>
178</ul>
179
180</div>
Chris Lattner57a460e2007-05-23 04:39:32 +0000181
Chris Lattner57a460e2007-05-23 04:39:32 +0000182
Chris Lattner84977642007-09-21 03:54:09 +0000183<!--=========================================================================-->
184<div class="doc_subsection">
185<a name="llvmgccimprovements">llvm-gcc Improvements</a>
186</div>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000187
Chris Lattner84977642007-09-21 03:54:09 +0000188<div class="doc_text">
189<p>New features include:
190</p>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000191
Chris Lattner84977642007-09-21 03:54:09 +0000192<ul>
193<li>Duncan and Anton exception handling in llvm-gcc 4.0/4.2</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000194
Chris Lattner84977642007-09-21 03:54:09 +0000195<li>Devang and Duncan: Bitfields, pragma pack</li>
Chris Lattner60893e52007-05-18 06:33:02 +0000196
Chris Lattner84977642007-09-21 03:54:09 +0000197<li>Tanya implemented support for __attribute__((noinline)) in llvm-gcc, and
198added support for generic variable annotations which are propagated into the
199LLVM IR, e.g. "<tt>int X __attribute__((annotate("myproperty")));</tt>".</li>
200
201<li>Sheng Zhou and Christopher Lamb implemented alias analysis support for
202'restrict' arguments to functions.</li>
203
204<li>Duncan contributed support for trampolines (pointers to nested functions),
205currently only supported on x86 target.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000206
Devang Patelf7a4e2a2007-09-21 18:02:24 +0000207<li> Lauro Ramos Venancio contributed support to encode alignment info in
208load and store instructions.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000209</ul>
210
Chris Lattner738bd302006-04-18 06:32:08 +0000211</div>
212
Chris Lattner84977642007-09-21 03:54:09 +0000213
214<!--=========================================================================-->
215<div class="doc_subsection">
216<a name="coreimprovements">LLVM Core Improvements</a>
217</div>
Chris Lattner26299222006-11-18 07:51:14 +0000218
Chris Lattner1c1a85c2006-04-19 04:02:47 +0000219<div class="doc_text">
Chris Lattner84977642007-09-21 03:54:09 +0000220<p>New features include:
Chris Lattner26299222006-11-18 07:51:14 +0000221</p>
222
223<ul>
Chris Lattner84977642007-09-21 03:54:09 +0000224<li>Neil Booth APFloat, foundation for long double support that will be wrapped
225up in 2.2. Dale contributed most of long double support, will be enabled in
2262.2.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000227
Chris Lattner84977642007-09-21 03:54:09 +0000228<li>LLVM now provides an LLVMBuilder class which makes it significantly easier
229to create LLVM IR instructions.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000230
Chris Lattner84977642007-09-21 03:54:09 +0000231<li>Reid contributed support for intrinsics that take arbitrary integer typed
232arguments, Dan Gohman and Chandler extended it to support FP and vectors.</li>
Chris Lattnerbfb17ab2007-05-17 21:41:31 +0000233</ul>
Chris Lattner84977642007-09-21 03:54:09 +0000234
Chris Lattnerbfb17ab2007-05-17 21:41:31 +0000235</div>
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000236
Chris Lattner84977642007-09-21 03:54:09 +0000237<!--=========================================================================-->
238<div class="doc_subsection">
239<a name="otherimprovements">Other Improvements</a>
240</div>
241
242<div class="doc_text">
243<p>New features include:
244</p>
245
246<ul>
247<li>BrainF frontend by Sterling Stein.</li>
248
249<li>David Green contributed a new --enable-expensive-checks configure option
250which enables STL checking, and fixed several bugs exposed by it.</li>
Chris Lattner84977642007-09-21 03:54:09 +0000251</ul>
252
253</div>
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000254
Chris Lattner19092612003-10-02 16:38:05 +0000255<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000256<div class="doc_section">
257 <a name="portability">Portability and Supported Platforms</a>
258</div>
Chris Lattner19092612003-10-02 16:38:05 +0000259<!-- *********************************************************************** -->
260
Misha Brukman500bc302003-11-22 00:38:41 +0000261<div class="doc_text">
262
John Criswell0b5b5e92004-12-08 20:35:47 +0000263<p>LLVM is known to work on the following platforms:</p>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000264
265<ul>
Chris Lattner57a460e2007-05-23 04:39:32 +0000266<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
Reid Spencer00812e22005-05-17 02:47:27 +0000267 (and probably other unix-like systems).</li>
Chris Lattner26299222006-11-18 07:51:14 +0000268<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
269 64-bit modes.</li>
Chris Lattner57a460e2007-05-23 04:39:32 +0000270<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
271<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
272 support is available for native builds with Visual C++).</li>
273<li>Sun UltraSPARC workstations running Solaris 8.</li>
John Criswell9321fa82005-05-13 20:28:15 +0000274<li>Alpha-based machines running Debian GNU/Linux.</li>
275<li>Itanium-based machines running Linux and HP-UX.</li>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000276</ul>
277
Brian Gaekeb0fd7612004-05-09 05:28:35 +0000278<p>The core LLVM infrastructure uses
279<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
280to the machine and operating system on which it is built. However, minor
281porting may be required to get LLVM to work on new platforms. We welcome your
282portability patches and reports of successful builds or error messages.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000283
Misha Brukman500bc302003-11-22 00:38:41 +0000284</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000285
286<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000287<div class="doc_section">
288 <a name="knownproblems">Known Problems</a>
289</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000290<!-- *********************************************************************** -->
291
Misha Brukman500bc302003-11-22 00:38:41 +0000292<div class="doc_text">
293
294<p>This section contains all known problems with the LLVM system, listed by
Chris Lattner79c3fe12003-10-02 04:57:28 +0000295component. As new problems are discovered, they will be added to these
Chris Lattner5eccca42003-12-12 21:22:16 +0000296sections. If you run into a problem, please check the <a
Chris Lattnerc463b272005-10-29 07:07:09 +0000297href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
Chris Lattner5eccca42003-12-12 21:22:16 +0000298there isn't already one.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000299
Misha Brukman500bc302003-11-22 00:38:41 +0000300</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000301
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000302<!-- ======================================================================= -->
303<div class="doc_subsection">
304 <a name="experimental">Experimental features included with this release</a>
305</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000306
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000307<div class="doc_text">
308
Misha Brukman6df9e2c2004-05-12 21:46:05 +0000309<p>The following components of this LLVM release are either untested, known to
310be broken or unreliable, or are in early development. These components should
311not be relied on, and bugs should not be filed against them, but they may be
312useful to some people. In particular, if you would like to work on one of these
Chris Lattner49e693e2006-08-09 04:08:52 +0000313components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000314
315<ul>
Bill Wendlingee143ad2007-09-25 20:45:10 +0000316<li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in a
Chris Lattner44c933e2006-04-18 06:18:36 +0000317 future release.</li>
Chris Lattner57a460e2007-05-23 04:39:32 +0000318<li>C++ EH support is disabled for this release.</li>
319<li>The MSIL backend is experimental.</li>
Chris Lattner58504a62006-02-05 06:39:36 +0000320<li>The IA64 code generator is experimental.</li>
Chris Lattnerc463b272005-10-29 07:07:09 +0000321<li>The Alpha JIT is experimental.</li>
Chris Lattner44c933e2006-04-18 06:18:36 +0000322<li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
323 <tt>-filetype</tt> llc option.</li>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000324</ul>
325
326</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000327
Misha Brukman500bc302003-11-22 00:38:41 +0000328<!-- ======================================================================= -->
329<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000330 <a name="x86-be">Known problems with the X86 back-end</a>
John Criswellc0c186d2005-11-08 21:11:33 +0000331</div>
332
333<div class="doc_text">
334
335<ul>
Chris Lattner26299222006-11-18 07:51:14 +0000336<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
Chris Lattnercaf06342007-05-09 04:58:11 +0000337 assembly that uses the X86 floating point stack</a>.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000338</ul>
339
340</div>
341
342<!-- ======================================================================= -->
343<div class="doc_subsection">
344 <a name="ppc-be">Known problems with the PowerPC back-end</a>
345</div>
346
347<div class="doc_text">
348
349<ul>
350<li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
351implement ordered FP comparisons</a>.</li>
Nicolas Geoffraye4285dc2007-05-15 09:21:28 +0000352<li>The Linux PPC32/ABI support needs testing for the interpreter and static
Chris Lattner57a460e2007-05-23 04:39:32 +0000353compilation, and lacks support for debug information.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000354</ul>
355
356</div>
357
358<!-- ======================================================================= -->
359<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000360 <a name="arm-be">Known problems with the ARM back-end</a>
361</div>
362
363<div class="doc_text">
364
365<ul>
Chris Lattner57a460e2007-05-23 04:39:32 +0000366<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
367processors, thumb program can crash or produces wrong
368results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000369<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
370</li>
Chris Lattner57a460e2007-05-23 04:39:32 +0000371<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
372programs compiled with LLVM. Please use more recent versions of QEMU.</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000373</ul>
374
375</div>
376
377<!-- ======================================================================= -->
378<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000379 <a name="sparc-be">Known problems with the SPARC back-end</a>
380</div>
381
382<div class="doc_text">
383
384<ul>
385<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
386 support the 64-bit SPARC ABI (-m64).</li>
387</ul>
388
389</div>
390
391<!-- ======================================================================= -->
392<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000393 <a name="alpha-be">Known problems with the Alpha back-end</a>
394</div>
395
396<div class="doc_text">
397
398<ul>
399
400<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
401appropriate nops inserted to ensure restartability.</li>
402
John Criswellc0c186d2005-11-08 21:11:33 +0000403</ul>
404</div>
405
Chris Lattner26299222006-11-18 07:51:14 +0000406<!-- ======================================================================= -->
407<div class="doc_subsection">
408 <a name="ia64-be">Known problems with the IA64 back-end</a>
409</div>
410
411<div class="doc_text">
412
413<ul>
414
415<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
416made where the argument is not 16-byte aligned, as required on IA64. (Strictly
417speaking this is not a bug in the IA64 back-end; it will also be encountered
418when building C++ programs using the C back-end.)</li>
419
420<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
421ABI compliant layout of v-tables</a>. In particular, it just stores function
422pointers instead of function descriptors in the vtable. This bug prevents
423mixing C++ code compiled with LLVM with C++ objects compiled by other C++
424compilers.</li>
425
426<li>There are a few ABI violations which will lead to problems when mixing LLVM
427output with code built with other compilers, particularly for floating-point
428programs.</li>
429
430<li>Defining vararg functions is not supported (but calling them is ok).</li>
431
Chris Lattnercaf06342007-05-09 04:58:11 +0000432<li>The Itanium backend has bitrotted somewhat.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000433</ul>
434
435</div>
436
437<!-- ======================================================================= -->
438<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000439 <a name="c-be">Known problems with the C back-end</a>
Chris Lattner26299222006-11-18 07:51:14 +0000440</div>
441
442<div class="doc_text">
443
444<ul>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000445<li><a href="http://llvm.org/PR802">The C backend does not support inline
446 assembly code</a>.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000447</ul>
448
449</div>
John Criswellc0c186d2005-11-08 21:11:33 +0000450
Misha Brukman500bc302003-11-22 00:38:41 +0000451
452<!-- ======================================================================= -->
453<div class="doc_subsection">
454 <a name="c-fe">Known problems with the C front-end</a>
455</div>
Chris Lattner47588f92003-10-02 05:07:23 +0000456
Chris Lattner79c3fe12003-10-02 04:57:28 +0000457<!-- _______________________________________________________________________ -->
Chris Lattnerb40efb32003-12-14 05:03:43 +0000458<div class="doc_subsubsection">Bugs</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000459
Misha Brukman500bc302003-11-22 00:38:41 +0000460<div class="doc_text">
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000461
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000462<p>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time
463Optimization</a> on most platforms "out-of-the-box". Please inquire on the
464llvmdev mailing list if you are interested.</p>
Chris Lattnerd9ea0172006-08-08 17:27:28 +0000465
Misha Brukman500bc302003-11-22 00:38:41 +0000466</div>
467
468<!-- _______________________________________________________________________ -->
469<div class="doc_subsubsection">
470 Notes
471</div>
472
473<div class="doc_text">
Misha Brukman500bc302003-11-22 00:38:41 +0000474<ul>
475
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000476<li><p>"long double" is silently transformed by the front-end into "double". There
477is no support for floating point data types of any size other than 32 and 64
478bits.</p></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000479
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000480<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
481 See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
482</li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000483
Duncan Sands32a83442007-05-18 09:04:20 +0000484<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000485 <ol>
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000486 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>: As in Algol and Pascal, lexical scoping of functions.<br>
487 Nested functions are supported, but llvm-gcc does not support non-local
488 gotos or taking the address of a nested function.</li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000489
490 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
Misha Brukman500bc302003-11-22 00:38:41 +0000491
John Criswelld000e1d2003-12-18 16:43:17 +0000492 Declaring that functions have no side effects or that they can never
Misha Brukman500bc302003-11-22 00:38:41 +0000493 return.<br>
494
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000495 <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
496 <tt>constructor</tt>, <tt>destructor</tt>,
Anton Korobeynikov9413de32006-11-18 08:04:48 +0000497 <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
Anton Korobeynikov9ec81372007-05-10 08:26:24 +0000498 <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noreturn</tt>, <tt>regparm</tt>
Anton Korobeynikov8cea37b2007-01-23 12:35:46 +0000499 <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
500 <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
Misha Brukman500bc302003-11-22 00:38:41 +0000501
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000502 <b>Ignored:</b> <tt>noinline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
503 <tt>malloc</tt>, <tt>no_instrument_function</tt></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000504 </ol>
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000505</li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000506
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000507<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000508
Chris Lattner79c3fe12003-10-02 04:57:28 +0000509 <ol>
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000510 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
511 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
512 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
513 Other built-in functions.</li>
514 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
515 Specifying attributes of variables.</li>
516 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
517 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
518 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
519 Arrays whose length is computed at run time.</li>
Chris Lattner7fe97dd2004-03-16 08:54:07 +0000520 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">Labels as Values</a>: Getting pointers to labels and computed gotos.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000521 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
522 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.</li>
Tanya Lattnerca26c3e2004-06-22 03:48:17 +0000523 <li><a href="http://gcc.gnu.org/onlinedocs/gcc-3.4.0/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000524 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
525 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
526 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
527 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
528 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
529 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
530 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.</li>
531 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000532 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.</li>
533 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
534 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html#Asm%20Labels">Asm Labels</a>: Specifying the assembler name to use for a C symbol.</li>
535 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html#Explicit%20Reg%20Vars">Explicit Reg Vars</a>: Defining variables residing in specified registers.</li>
536 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.</li>
537 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000538 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.</li>
Misha Brukmanc4b7bee2003-12-12 04:37:31 +0000539 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html#Pointer%20Arith">Pointer Arith</a>: Arithmetic on <code>void</code>-pointers and function pointers.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000540 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
John Criswelld000e1d2003-12-18 16:43:17 +0000541 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
542or arrays as values.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000543 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
Misha Brukmanc4b7bee2003-12-12 04:37:31 +0000544 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast%20to%20Union">Cast to Union</a>: Casting to union type from any member of the union.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000545 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
546 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
547 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
Tanya Lattner78537e42004-12-08 18:29:38 +0000548 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Comments.html#C_002b_002b-Comments">C++ Comments</a>: C++ comments are recognized.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000549 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
550 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Character-Escapes.html#Character%20Escapes">Character Escapes</a>: <code>\e</code> stands for the character &lt;ESC&gt;.</li>
551 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
552 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
553 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html#Alternate%20Keywords">Alternate Keywords</a>:<code>__const__</code>, <code>__asm__</code>, etc., for header files.</li>
554 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html#Incomplete%20Enums">Incomplete Enums</a>: <code>enum foo;</code>, with details to follow.</li>
555 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function%20Names">Function Names</a>: Printable strings which are the name of the current function.</li>
Chris Lattner25795bc2004-02-14 04:08:29 +0000556 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html#Return%20Address">Return Address</a>: Getting the return or frame address of a function.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000557 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.</li>
558 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
Misha Brukmane0c891c2003-11-22 01:00:11 +0000559 </ol></li>
560
561</ul>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000562
Misha Brukman500bc302003-11-22 00:38:41 +0000563<p>If you run into GCC extensions which have not been included in any of these
564lists, please let us know (also including whether or not they work).</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000565
Misha Brukman500bc302003-11-22 00:38:41 +0000566</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000567
Misha Brukman500bc302003-11-22 00:38:41 +0000568<!-- ======================================================================= -->
569<div class="doc_subsection">
570 <a name="c++-fe">Known problems with the C++ front-end</a>
571</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000572
Misha Brukman500bc302003-11-22 00:38:41 +0000573<div class="doc_text">
574
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000575<p>The C++ front-end is considered to be fully
Chris Lattner7506b1d2004-12-07 08:04:13 +0000576tested and works for a number of non-trivial programs, including LLVM
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000577itself, Qt, Mozilla, etc.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000578
Misha Brukman500bc302003-11-22 00:38:41 +0000579<ul>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000580<li>llvm-gcc4 only has partial support for <a href="http://llvm.org/PR870">C++
581Exception Handling</a>, and it is not enabled by default.</li>
582
583<!-- NO EH Support!
Chris Lattnere01fcfb2003-10-27 18:30:37 +0000584
Chris Lattner79c3fe12003-10-02 04:57:28 +0000585<li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
Chris Lattner19092612003-10-02 16:38:05 +0000586 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
Chris Lattner79c3fe12003-10-02 04:57:28 +0000587 function and in the <tt>setjmp</tt> receiver function may not be run.
John Criswelld000e1d2003-12-18 16:43:17 +0000588 Objects in intervening stack frames will be destroyed, however (which is
Misha Brukman500bc302003-11-22 00:38:41 +0000589 better than most compilers).</li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000590
Chris Lattner19092612003-10-02 16:38:05 +0000591<li>The LLVM C++ front-end follows the <a
592 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
593 This document, which is not Itanium specific, specifies a standard for name
594 mangling, class layout, v-table layout, RTTI formats, and other C++
595 representation issues. Because we use this API, code generated by the LLVM
596 compilers should be binary compatible with machine code generated by other
597 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
Chris Lattner26299222006-11-18 07:51:14 +0000598 <i>However</i>, the exception handling mechanism used by llvm-gcc3 is very
Chris Lattner19092612003-10-02 16:38:05 +0000599 different from the model used in the Itanium ABI, so <b>exceptions will not
Misha Brukman500bc302003-11-22 00:38:41 +0000600 interact correctly</b>. </li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000601-->
Misha Brukman500bc302003-11-22 00:38:41 +0000602</ul>
Chris Lattnerfcc54b32003-10-07 22:14:37 +0000603
Misha Brukman500bc302003-11-22 00:38:41 +0000604</div>
605
Misha Brukman500bc302003-11-22 00:38:41 +0000606
Chris Lattner98a493c2005-05-15 16:01:20 +0000607
Chris Lattner79c3fe12003-10-02 04:57:28 +0000608<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000609<div class="doc_section">
610 <a name="additionalinfo">Additional Information</a>
611</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000612<!-- *********************************************************************** -->
613
Misha Brukman500bc302003-11-22 00:38:41 +0000614<div class="doc_text">
615
Chris Lattner416db102005-05-16 17:13:10 +0000616<p>A wide variety of additional information is available on the <a
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000617href="http://llvm.org">LLVM web page</a>, in particular in the <a
618href="http://llvm.org/docs/">documentation</a> section. The web page also
Reid Spencer669ed452007-07-09 08:04:31 +0000619contains versions of the API documentation which is up-to-date with the
620Subversion version of the source code.
Misha Brukman109d9e82005-03-30 19:14:24 +0000621You can access versions of these documents specific to this release by going
622into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000623
Misha Brukman500bc302003-11-22 00:38:41 +0000624<p>If you have any questions or comments about LLVM, please feel free to contact
Chris Lattnerc463b272005-10-29 07:07:09 +0000625us via the <a href="http://llvm.org/docs/#maillist"> mailing
Chris Lattner5eccca42003-12-12 21:22:16 +0000626lists</a>.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000627
Misha Brukman500bc302003-11-22 00:38:41 +0000628</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000629
630<!-- *********************************************************************** -->
Chris Lattner79c3fe12003-10-02 04:57:28 +0000631
Misha Brukman500bc302003-11-22 00:38:41 +0000632<hr>
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638
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000639 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
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Misha Brukman2061e892003-11-22 01:23:39 +0000641</address>
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