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Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]7 <title>LLVM 2.3 Release Notes</title>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]8</head>
9<body>
10
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]11<div class="doc_title">LLVM 2.3 Release Notes</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]12
13<ol>
14 <li><a href="#intro">Introduction</a></li>
15 <li><a href="#whatsnew">What's New?</a></li>
16 <li><a href="GettingStarted.html">Installation Instructions</a></li>
17 <li><a href="#portability">Portability and Supported Platforms</a></li>
18 <li><a href="#knownproblems">Known Problems</a>
19 <li><a href="#additionalinfo">Additional Information</a></li>
20</ol>
21
22<div class="doc_author">
23 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
24</div>
25
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]26<!-- Done through Week-of-Mon-20080324.txt -->
27
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]28<!-- *********************************************************************** -->
29<div class="doc_section">
30 <a name="intro">Introduction</a>
31</div>
32<!-- *********************************************************************** -->
33
34<div class="doc_text">
35
36<p>This document contains the release notes for the LLVM compiler
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]37infrastructure, release 2.3. Here we describe the status of LLVM, including
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]38major improvements from the previous release and any known problems. All LLVM
39releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
40releases web site</a>.</p>
41
42<p>For more information about LLVM, including information about the latest
43release, please check out the <a href="http://llvm.org/">main LLVM
44web site</a>. If you have questions or comments, the <a
45href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
46list</a> is a good place to send them.</p>
47
48<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]49main LLVM web page, this document applies to the <i>next</i> release, not the
50current one. To see the release notes for a specific releases, please see the
51<a href="http://llvm.org/releases/">releases page</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]52
53</div>
54
55<!-- *********************************************************************** -->
56<div class="doc_section">
57 <a name="whatsnew">What's New?</a>
58</div>
59<!-- *********************************************************************** -->
60
61<div class="doc_text">
62
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]63<p>This is the fourteenth public release of the LLVM Compiler Infrastructure.
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]64It includes a large number of features and refinements from LLVM 2.2.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]65
66</div>
67
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]68<!-- Unfinished features in 2.3:
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]69 Machine LICM
70 Machine Sinking
71 LegalizeDAGTypes
72 -->
73
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]74<!--=========================================================================-->
75<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]76<a name="changes">Major Changes in LLVM 2.3</a>
Chris Lattner41bf8e92008-02-10 07:04:35 +0000[diff] [blame]77</div>
78
79<div class="doc_text">
80
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]81<p>LLVM 2.2 was the last LLVM release to support llvm-gcc 4.0 and llvm-upgrade.
82llvm-gcc 4.0 has been replaced with llvm-gcc 4.2. llvm-upgrade was useful for
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]83upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a previous
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]84LLVM release to do this. One nice impact of this is that the LLVM regression
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]85test suite no longer depends on llvm-upgrade, which makes it run faster.</p>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]86
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]87<p>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to
88 IRBuilder.</p>
89
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]90</div>
91
92<!--=========================================================================-->
93<div class="doc_subsection">
94<a name="majorfeatures">Major New Features</a>
95</div>
96
97<div class="doc_text">
98
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]99<p>LLVM 2.3 includes several major new capabilities:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]100
101<ul>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]102<li>Multiple Return Value Support</li>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]103
104
105<li><p>LLVM 2.3 includes a complete reimplementation of the "llvmc" tool. It is
106designed to overcome several problems of the original llvmc and to provide a
107superset of the features as the 'gcc' driver.</p>
108
109<p>The main features of llvmc2 is:</p>
110
111<ul>
112<li>Extended handling of command line options and smart rules for
113dispatching them to different tools.</li>
114<li>Flexible (and extensible) rules for defining different tools.</li>
115<li>The different intermediate steps performed by tools are represented
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]116as edges in the abstract graph.</li>
117<li>The 'language' for driver behaviour definition is tablegen and thus
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]118it's relatively easy to add new features.</li>
119<li>The definition of driver is transformed into set of C++ classes, thus
120no runtime interpretation is needed.</li>
121</ul>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]122</li>
123
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]124
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]125<li>Reimplemented <a href="LinkTimeOptimization.html">LTO interface</a> in
126 C.</li>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]127
128
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]129<li>kaleidoscope tutorial in ocaml.</li>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]130
Chris Lattner5ba16862008-02-10 08:18:42 +0000[diff] [blame]131</ul>
132
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]133</div>
134
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]135
136<!--=========================================================================-->
137<div class="doc_subsection">
138<a name="frontends">llvm-gcc 4.2 Improvements and Clang</a>
139</div>
140
141<div class="doc_text">
142
143<p>LLVM 2.3 fully supports llvm-gcc 4.2 front-end.</p>
144
145<p>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C
146front-end. Objective-C now works very well on Mac OS/X.</p>
147
148<p>llvm-gcc 4.2 includes many other fixes which improve conformance with the
149relevant parts of the GCC testsuite.</p>
150
151<p>The <a href="http://clang.llvm.org/">clang project</a> is an effort to build
152a set of new 'llvm native' front-end technologies for the LLVM optimizer
153and code generator. Currently, its C and Objective-C support is maturing
154nicely, and it has advanced source-to-source analysis and transformation
155capabilities. If you are interested in building source-level tools for C and
156Objective-C (and eventually C++), you should take a look. However, note that
157clang is not an official part of the LLVM 2.3 release. If you are interested in
158this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
159
160</div>
161
162
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]163<!--=========================================================================-->
164<div class="doc_subsection">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]165<a name="coreimprovements">LLVM Core Improvements</a>
166</div>
167
168<div class="doc_text">
169<p>New features include:
170</p>
171
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]172
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]173Common linkage?
174
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]175Atomic operation support, Alpha, X86, X86-64, PowerPC. "__sync_synchronize"
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]176
177<ul>
Gordon Henriksenf9b229b2008-06-05 12:51:50 +0000[diff] [blame]178<li>The C and Ocaml bindings have received additional improvements. The
179bindings now cover pass managers, several transformation passes, iteration
180over the LLVM IR, target data, and parameter attribute lists.</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]181</ul>
182
183</div>
184
185<!--=========================================================================-->
186<div class="doc_subsection">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]187<a name="codegen">Code Generator Improvements</a>
188</div>
189
190<div class="doc_text">
191
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]192<p>We put a significant amount of work into the code generator infrastructure,
193which allows us to implement more aggressive algorithms and make it run
194faster:</p>
Chris Lattner7d2b1102007-09-26 05:44:21 +0000[diff] [blame]195
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]196<ul>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]197<li>MemOperand in the code generator: describe me!.</li>
Dan Gohmanaa3c6872008-06-05 18:45:33 +0000[diff] [blame]198<li>The target-independent code generator infrastructure now uses LLVM's APInt
199 class to handle integer values, which allows it to support integer types
200 larger than 64 bits. Note that support for such types is also dependent on
Dan Gohman7e661062008-06-05 15:43:11 +0000[diff] [blame]201 target-specific support. Use of APInt is also a step toward support for
202 non-power-of-2 integer sizes.</li>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]203<li>Several compile time speedups for code with large basic blocks.</li>
Dan Gohmane8582042008-06-05 15:46:36 +0000[diff] [blame]204<li>Several improvements which make llc's <tt>--view-sunit-dags</tt>
205 visualization of scheduling dependency graphs easier to understand.</li>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]206</ul>
207
208</div>
209
210<!--=========================================================================-->
211<div class="doc_subsection">
212<a name="optimizer">Optimizer Improvements</a>
213</div>
214
215<div class="doc_text">
216
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]217<p>In addition to a huge array of bug fixes and minor performance tweaks, the
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]218LLVM 2.3 optimizers support a few major enhancements:</p>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]219
220<ul>
221
Devang Patel67e46712008-06-05 21:44:00 +0000[diff] [blame]222<li>Loop index set splitting on by default.<p>
223This transformation hoists conditions from loop bodies and reduces loop's
224iteration space to improve performance. For example, <p>
225<pre>
226for (i = LB; i < UB; ++i)
227 if (i <= NV)
228 LOOP_BODY
229</pre>
230is transformed into
231<pre>
232NUB = min(NV+1, UB)
233for (i = LB; i < NUB; ++i)
234 LOOP_BODY
235</pre>
236</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]237<li>LLVM includes a new <tt>memcpy</tt> optimization pass which optimizes out dead
238<tt>memcpy</tt> calls, unneeded copies of aggregates, and handles the return slot
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]239optimization. The LLVM optimizer now notices long sequences of consequtive
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]240stores and merges them into <tt>memcpy</tt>s where profitable.</li>
241<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
242<tt>memset</tt> is now more aggressive.</li>
Owen Anderson7f8ea062008-06-06 16:23:15 +0000[diff] [blame^]243
244<li>The aggressive dead code elimination (ADCE) optimization has been rewritten to make
245it both faster and safer in the presence of code containing infinite loops.
246Some of its prior functionality has been factored out into the loop deletion
247pass, which <em>is</em> safe for infinite loops.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]248</ul>
249
250</div>
251
252
253<!--=========================================================================-->
254<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]255<a name="x86specific">X86/X86-64 Specific Improvements</a>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]256</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]257
258<div class="doc_text">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]259<p>New target-specific features include:
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]260</p>
261
262<ul>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]263<li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]264 area of passing and returning structures by value. llvm-gcc compiled code
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]265 now interoperates very well on X86-64 systems with other compilers.</li>
266
267<li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and
268 the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins.</li>
269
270<li>The X86 backend now does a number of optimizations that aim to avoid
271 converting numbers back and forth from SSE registers to the X87 floating
272 point stack.</li>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]273
274<li>The X86 backend supports stack realignment, which is particularly useful for
275 vector code on OS's without 16-byte aligned stacks.</li>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]276
277<li>The X86 backend now supports the "sseregparm" options in GCC, which allow
278 functions to be tagged as passing floating point values in SSE
279 registers.</li>
280
281<li>Trampolines (taking the address of a nested function) now work on
282 Linux/x86-64.</li>
283
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]284<li><tt>__builtin_prefetch</tt> is now compiled into the appropriate prefetch
285 instructions instead of being ignored.</li>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]286
Dan Gohman74e1ff52008-06-05 16:15:39 +0000[diff] [blame]287<li>128-bit integers are now supported on x86-64 targets.</li>
288
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]289</ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]290
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]291</div>
292
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]293<!--=========================================================================-->
294<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]295<a name="targetspecific">Other Target Specific Improvements</a>
296</div>
297
298<div class="doc_text">
299<p>New target-specific features include:
300</p>
301
302<ul>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]303<li>The LLVM C backend now supports vector code.</li>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]304
305
306</ul>
307
308</div>
309
310
311
312<!--=========================================================================-->
313<div class="doc_subsection">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]314<a name="otherimprovements">Other Improvements</a>
315</div>
316
317<div class="doc_text">
318<p>New features include:
319</p>
320
321<ul>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]322<li>LLVM now builds with GCC 4.3.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]323<li>llvm2cpp tool has been folded into llc, use <tt>llc -march=cpp</tt></li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]324</ul>
325
326</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]327
328<!-- *********************************************************************** -->
329<div class="doc_section">
330 <a name="portability">Portability and Supported Platforms</a>
331</div>
332<!-- *********************************************************************** -->
333
334<div class="doc_text">
335
336<p>LLVM is known to work on the following platforms:</p>
337
338<ul>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]339<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]340 (and probably other unix-like systems).</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]341<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]342 64-bit modes.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]343<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]344<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
345 support is available for native builds with Visual C++).</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]346<li>Sun UltraSPARC workstations running Solaris 10.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]347<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]348<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]349</ul>
350
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]351<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]352to the machine and operating system on which it is built. However, minor
353porting may be required to get LLVM to work on new platforms. We welcome your
354portability patches and reports of successful builds or error messages.</p>
355
356</div>
357
358<!-- *********************************************************************** -->
359<div class="doc_section">
360 <a name="knownproblems">Known Problems</a>
361</div>
362<!-- *********************************************************************** -->
363
364<div class="doc_text">
365
366<p>This section contains all known problems with the LLVM system, listed by
367component. As new problems are discovered, they will be added to these
368sections. If you run into a problem, please check the <a
369href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
370there isn't already one.</p>
371
372</div>
373
374<!-- ======================================================================= -->
375<div class="doc_subsection">
376 <a name="experimental">Experimental features included with this release</a>
377</div>
378
379<div class="doc_text">
380
381<p>The following components of this LLVM release are either untested, known to
382be broken or unreliable, or are in early development. These components should
383not be relied on, and bugs should not be filed against them, but they may be
384useful to some people. In particular, if you would like to work on one of these
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]385components, please contact us on the <a
386href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]387
388<ul>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]389<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]390<li>The LLC "<tt>-filetype=asm</tt>" (the default) is the only supported
391 value for this option.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]392</ul>
393
394</div>
395
396<!-- ======================================================================= -->
397<div class="doc_subsection">
398 <a name="x86-be">Known problems with the X86 back-end</a>
399</div>
400
401<div class="doc_text">
402
403<ul>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]404<li>The X86 backend does not yet support all <a
405 href="http://llvm.org/PR879">inline assembly that uses the X86 floating
406 point stack</a>. It supports the 'f' and 't' constraints, but not 'u'.</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]407<li>The X86 backend generates inefficient floating point code when configured to
408 generate code for systems that don't have SSE2.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]409</ul>
410
411</div>
412
413<!-- ======================================================================= -->
414<div class="doc_subsection">
415 <a name="ppc-be">Known problems with the PowerPC back-end</a>
416</div>
417
418<div class="doc_text">
419
420<ul>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]421<li>The Linux PPC32/ABI support needs testing for the interpreter and static
422compilation, and lacks support for debug information.</li>
423</ul>
424
425</div>
426
427<!-- ======================================================================= -->
428<div class="doc_subsection">
429 <a name="arm-be">Known problems with the ARM back-end</a>
430</div>
431
432<div class="doc_text">
433
434<ul>
435<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]436processors, thumb programs can crash or produce wrong
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]437results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
438<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
439</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]440<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly execute
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]441programs compiled with LLVM. Please use more recent versions of QEMU.</li>
442</ul>
443
444</div>
445
446<!-- ======================================================================= -->
447<div class="doc_subsection">
448 <a name="sparc-be">Known problems with the SPARC back-end</a>
449</div>
450
451<div class="doc_text">
452
453<ul>
454<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
455 support the 64-bit SPARC ABI (-m64).</li>
456</ul>
457
458</div>
459
460<!-- ======================================================================= -->
461<div class="doc_subsection">
462 <a name="alpha-be">Known problems with the Alpha back-end</a>
463</div>
464
465<div class="doc_text">
466
467<ul>
468
469<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
470appropriate nops inserted to ensure restartability.</li>
471
472</ul>
473</div>
474
475<!-- ======================================================================= -->
476<div class="doc_subsection">
477 <a name="ia64-be">Known problems with the IA64 back-end</a>
478</div>
479
480<div class="doc_text">
481
482<ul>
483
484<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
485made where the argument is not 16-byte aligned, as required on IA64. (Strictly
486speaking this is not a bug in the IA64 back-end; it will also be encountered
487when building C++ programs using the C back-end.)</li>
488
489<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
490ABI compliant layout of v-tables</a>. In particular, it just stores function
491pointers instead of function descriptors in the vtable. This bug prevents
492mixing C++ code compiled with LLVM with C++ objects compiled by other C++
493compilers.</li>
494
495<li>There are a few ABI violations which will lead to problems when mixing LLVM
496output with code built with other compilers, particularly for floating-point
497programs.</li>
498
499<li>Defining vararg functions is not supported (but calling them is ok).</li>
500
501<li>The Itanium backend has bitrotted somewhat.</li>
502</ul>
503
504</div>
505
506<!-- ======================================================================= -->
507<div class="doc_subsection">
508 <a name="c-be">Known problems with the C back-end</a>
509</div>
510
511<div class="doc_text">
512
513<ul>
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]514<li><a href="http://llvm.org/PR802">The C backend has only basic support for
515 inline assembly code</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]516<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
517 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
518 C++ code compiled with LLC or native compilers.</li>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]519<li>The C backend does not support all exception handling constructs.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]520</ul>
521
522</div>
523
524
525<!-- ======================================================================= -->
526<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]527 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]528</div>
529
530<!-- _______________________________________________________________________ -->
531<div class="doc_subsubsection">Bugs</div>
532
533<div class="doc_text">
534
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]535<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
536Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]537llvmdev mailing list if you are interested.</p>
538
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]539<p>The only major language feature of GCC not supported by llvm-gcc is
540 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
541 are only supported on some targets. For example, trampolines are only
542 supported on some targets, which are used when you take the address of a
543 nested function.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]544
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]545<p>If you run into GCC extensions which are not supported, please let us know.
546</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]547
548</div>
549
550<!-- ======================================================================= -->
551<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]552 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]553</div>
554
555<div class="doc_text">
556
557<p>The C++ front-end is considered to be fully
558tested and works for a number of non-trivial programs, including LLVM
559itself, Qt, Mozilla, etc.</p>
560
561<ul>
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]562<li>Exception handling works well on the X86 and PowerPC targets, including
563x86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is
564supported on x86-64 linux, but that is disabled by default in this release.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]565</ul>
566
567</div>
568
569
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]570<!-- ======================================================================= -->
571<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]572 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]573</div>
574
575<div class="doc_text">
576The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
577technology and problems should be expected.
578<ul>
579<li>The Ada front-end currently only builds on x86-32. This is mainly due
580to lack of trampoline support (pointers to nested functions) on other platforms,
581however it <a href="http://llvm.org/PR2006">also fails to build on x86-64</a>
582which does support trampolines.</li>
583<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
584Workaround: configure with --disable-bootstrap.</li>
585<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
586fail (c380004 also fails with gcc-4.2 mainline).</li>
587<li>Many gcc specific Ada tests continue to crash the compiler.</li>
588<li>The -E binder option (exception backtraces)
589<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
590crashing if an exception is raised. Workaround: do not use -E.</li>
591<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
592or finish at a non-byte offset</a> in a record. Workaround: do not pack records
593or use representation clauses that result in a field of a non-discrete type
594starting or finishing in the middle of a byte.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]595<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers 'main'
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]596as generated by the Ada binder to be invalid</a>.
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]597Workaround: hand edit the file to use pointers for <tt>argv</tt> and <tt>envp</tt> rather than
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]598integers.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]599<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is ignored</a>.</li>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]600</ul>
601</div>
602
603<!-- ======================================================================= -->
604<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]605 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]606</div>
607
608<div class="doc_text">
609
610<ul>
611<li>The llvm-gcc 4.2 gfortran front-end supports a broad range of Fortran code, but does
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]612<a href="http://llvm.org/PR1971">not support <tt>EQUIVALENCE</tt> yet</a>.</li>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]613</ul>
614</div>
615
616
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]617
618<!-- *********************************************************************** -->
619<div class="doc_section">
620 <a name="additionalinfo">Additional Information</a>
621</div>
622<!-- *********************************************************************** -->
623
624<div class="doc_text">
625
626<p>A wide variety of additional information is available on the <a
627href="http://llvm.org">LLVM web page</a>, in particular in the <a
628href="http://llvm.org/docs/">documentation</a> section. The web page also
629contains versions of the API documentation which is up-to-date with the
630Subversion version of the source code.
631You can access versions of these documents specific to this release by going
632into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
633
634<p>If you have any questions or comments about LLVM, please feel free to contact
635us via the <a href="http://llvm.org/docs/#maillist"> mailing
636lists</a>.</p>
637
638</div>
639
640<!-- *********************************************************************** -->
641
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