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Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]8 <title>LLVM 2.3 Release Notes</title>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]9</head>
10<body>
11
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]12<div class="doc_title">LLVM 2.3 Release Notes</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]13
14<ol>
15 <li><a href="#intro">Introduction</a></li>
16 <li><a href="#whatsnew">What's New?</a></li>
17 <li><a href="GettingStarted.html">Installation Instructions</a></li>
18 <li><a href="#portability">Portability and Supported Platforms</a></li>
19 <li><a href="#knownproblems">Known Problems</a>
20 <li><a href="#additionalinfo">Additional Information</a></li>
21</ol>
22
23<div class="doc_author">
24 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
25</div>
26
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]27<!-- Done through Week-of-Mon-20080324.txt -->
28
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]29<!-- *********************************************************************** -->
30<div class="doc_section">
31 <a name="intro">Introduction</a>
32</div>
33<!-- *********************************************************************** -->
34
35<div class="doc_text">
36
37<p>This document contains the release notes for the LLVM compiler
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]38infrastructure, release 2.3. Here we describe the status of LLVM, including
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]39major improvements from the previous release and any known problems. All LLVM
40releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
41releases web site</a>.</p>
42
43<p>For more information about LLVM, including information about the latest
44release, please check out the <a href="http://llvm.org/">main LLVM
45web site</a>. If you have questions or comments, the <a
46href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
47list</a> is a good place to send them.</p>
48
49<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]50main LLVM web page, this document applies to the <i>next</i> release, not the
51current one. To see the release notes for a specific releases, please see the
52<a href="http://llvm.org/releases/">releases page</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]53
54</div>
55
56<!-- *********************************************************************** -->
57<div class="doc_section">
58 <a name="whatsnew">What's New?</a>
59</div>
60<!-- *********************************************************************** -->
61
62<div class="doc_text">
63
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]64<p>This is the fourteenth public release of the LLVM Compiler Infrastructure.
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]65It includes a large number of features and refinements from LLVM 2.2.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]66
67</div>
68
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]69<!-- Unfinished features in 2.3:
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]70 Machine LICM
71 Machine Sinking
72 LegalizeDAGTypes
73 -->
74
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]75<!--=========================================================================-->
76<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]77<a name="changes">Major Changes in LLVM 2.3</a>
Chris Lattner41bf8e92008-02-10 07:04:35 +0000[diff] [blame]78</div>
79
80<div class="doc_text">
81
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]82<p>LLVM 2.2 was the last LLVM release to support llvm-gcc 4.0 and llvm-upgrade.
83llvm-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]84upgrading 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]85LLVM release to do this. One nice impact of this is that the LLVM regression
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]86test suite no longer depends on llvm-upgrade, which makes it run faster.</p>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]87
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]88<p>LLVM API Changes:</p>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]89
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]90<ul>
91<li>Several core LLVM IR classes have migrated to use 'FOOCLASS::Create(...)'
92 instead of 'new FOOCLASS(...)' (e.g. where FOOCLASS=BasicBlock). We hope to
93 standardize on FOOCLASS::Create for all IR classes in the future, but not
94 all of them have been moved over yet.</li>
95<li>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to
96 IRBuilder.</li>
97<li>MRegisterInfo was renamed to TargetRegisterInfo.</li>
98<li>The MappedFile class is gone, please use MemoryBuffer instead.</li>
99<li>The '-enable-eh' flag to LLC has been removed. Now code should encode
100 whether it is safe to not generate unwind information for a function by
101 tagging the Function object with the 'nounwind' attribute.</li>
102
103</ul>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]104</div>
105
106<!--=========================================================================-->
107<div class="doc_subsection">
108<a name="majorfeatures">Major New Features</a>
109</div>
110
111<div class="doc_text">
112
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]113<p>LLVM 2.3 includes several major new capabilities:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]114
115<ul>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]116<li>Multiple Return Value Support</li>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]117
118
119<li><p>LLVM 2.3 includes a complete reimplementation of the "llvmc" tool. It is
120designed to overcome several problems of the original llvmc and to provide a
121superset of the features as the 'gcc' driver.</p>
122
123<p>The main features of llvmc2 is:</p>
124
125<ul>
126<li>Extended handling of command line options and smart rules for
127dispatching them to different tools.</li>
128<li>Flexible (and extensible) rules for defining different tools.</li>
129<li>The different intermediate steps performed by tools are represented
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]130as edges in the abstract graph.</li>
131<li>The 'language' for driver behaviour definition is tablegen and thus
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]132it's relatively easy to add new features.</li>
133<li>The definition of driver is transformed into set of C++ classes, thus
134no runtime interpretation is needed.</li>
135</ul>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]136</li>
137
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]138
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]139<li>Reimplemented <a href="LinkTimeOptimization.html">LTO interface</a> in
140 C.</li>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]141
142
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]143<li>kaleidoscope tutorial in ocaml.</li>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]144
Chris Lattner5ba16862008-02-10 08:18:42 +0000[diff] [blame]145</ul>
146
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]147</div>
148
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]149
150<!--=========================================================================-->
151<div class="doc_subsection">
152<a name="frontends">llvm-gcc 4.2 Improvements and Clang</a>
153</div>
154
155<div class="doc_text">
156
157<p>LLVM 2.3 fully supports llvm-gcc 4.2 front-end.</p>
158
159<p>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C
160front-end. Objective-C now works very well on Mac OS/X.</p>
161
162<p>llvm-gcc 4.2 includes many other fixes which improve conformance with the
163relevant parts of the GCC testsuite.</p>
164
165<p>The <a href="http://clang.llvm.org/">clang project</a> is an effort to build
166a set of new 'llvm native' front-end technologies for the LLVM optimizer
167and code generator. Currently, its C and Objective-C support is maturing
168nicely, and it has advanced source-to-source analysis and transformation
169capabilities. If you are interested in building source-level tools for C and
170Objective-C (and eventually C++), you should take a look. However, note that
171clang is not an official part of the LLVM 2.3 release. If you are interested in
172this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
173
174</div>
175
176
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]177<!--=========================================================================-->
178<div class="doc_subsection">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]179<a name="coreimprovements">LLVM Core Improvements</a>
180</div>
181
182<div class="doc_text">
183<p>New features include:
184</p>
185
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]186
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]187Common linkage?
188
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]189Atomic operation support, Alpha, X86, X86-64, PowerPC. "__sync_synchronize",
Anton Korobeynikov877b73b2008-06-08 10:23:46 +0000[diff] [blame]190"__sync_val_compare_and_swap", etc
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]191
192<ul>
Gordon Henriksenf9b229b2008-06-05 12:51:50 +0000[diff] [blame]193<li>The C and Ocaml bindings have received additional improvements. The
194bindings now cover pass managers, several transformation passes, iteration
195over the LLVM IR, target data, and parameter attribute lists.</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]196</ul>
197
198</div>
199
200<!--=========================================================================-->
201<div class="doc_subsection">
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]202<a name="optimizer">Optimizer Improvements</a>
203</div>
204
205<div class="doc_text">
206
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]207<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]208LLVM 2.3 optimizers support a few major enhancements:</p>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]209
210<ul>
211
Devang Patel67e46712008-06-05 21:44:00 +0000[diff] [blame]212<li>Loop index set splitting on by default.<p>
213This transformation hoists conditions from loop bodies and reduces loop's
214iteration space to improve performance. For example, <p>
215<pre>
216for (i = LB; i < UB; ++i)
217 if (i <= NV)
218 LOOP_BODY
219</pre>
220is transformed into
221<pre>
222NUB = min(NV+1, UB)
223for (i = LB; i < NUB; ++i)
224 LOOP_BODY
225</pre>
226</li>
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]227
228<li>LLVM includes a new <tt>memcpy</tt> optimization pass which optimizes out
229dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and handles the
230return slot optimization. The LLVM optimizer now notices long sequences of
231consequtive stores and merges them into <tt>memcpy</tt>s where profitable.</li>
232
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]233<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
234<tt>memset</tt> is now more aggressive.</li>
Owen Anderson7f8ea062008-06-06 16:23:15 +0000[diff] [blame]235
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]236<li>The aggressive dead code elimination (ADCE) optimization has been rewritten
237to make it both faster and safer in the presence of code containing infinite
238loops. Some of its prior functionality has been factored out into the loop
239deletion pass, which <em>is</em> safe for infinite loops.</li>
240
241<li>Several optimizations have been sped up, leading to faster code generation
242 with the same code quality.</li>
243
244<li>The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm
245 functions for C-based languages, has been rewritten to be a FunctionPass
246 instead a ModulePass. This allows it to be run more often and to be
247 included at -O1 in llvm-gcc. It was also extended to include more
248 optimizations and several corner case bugs are fixed.</li>
249
250<li>LLVM now includes a simple 'Jump Threading' pass, which attemps to simplify
251 the conditional branches with information about predecessor blocks. This
252 simplifies the control flow graph. This pass is pretty basic at this point,
253 but catches some important cases and provides a foundation to build off
254 of.</li>
255</ul>
256
257</div>
258
259<!--=========================================================================-->
260<div class="doc_subsection">
261<a name="codegen">Code Generator Improvements</a>
262</div>
263
264<div class="doc_text">
265
266<p>We put a significant amount of work into the code generator infrastructure,
267which allows us to implement more aggressive algorithms and make it run
268faster:</p>
269
270<ul>
271<li>MemOperand in the code generator: describe me!.</li>
272
273<li>The target-independent code generator infrastructure now uses LLVM's APInt
274 class to handle integer values, which allows it to support integer types
275 larger than 64 bits. Note that support for such types is also dependent on
276 target-specific support. Use of APInt is also a step toward support for
277 non-power-of-2 integer sizes.</li>
278
279<li>Several compile time speedups for code with large basic blocks.</li>
280
281<li>Several improvements which make llc's <tt>--view-sunit-dags</tt>
282 visualization of scheduling dependency graphs easier to understand.</li>
283
284<li>The code generator allows targets to write patterns that generate subreg
285 references directly in .td files now.</li>
286
287<li><tt>memcpy</tt> lowering in the backend is more aggressive, particularly for
288 <tt>memcpy</tt> calls introduced by the code generator when handling
289 pass-by-value structure argument copies.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]290</ul>
291
292</div>
293
294
295<!--=========================================================================-->
296<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]297<a name="x86specific">X86/X86-64 Specific Improvements</a>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]298</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]299
300<div class="doc_text">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]301<p>New target-specific features include:
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]302</p>
303
304<ul>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]305<li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]306 area of passing and returning structures by value. llvm-gcc compiled code
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]307 now interoperates very well on X86-64 systems with other compilers.</li>
308
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame^]309<li>Support for Win64 was added. This includes codegeneration itself, JIT
310 support and necessary changes to llvm-gcc.</li>
311
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]312<li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]313 the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins. Various
314 generic vector operations (insert/extract/shuffle) are much more efficient
315 when SSE 4.1 is enabled. The JIT automatically takes advantage of these
316 instructions, but llvm-gcc must be explicitly told to use them, e.g. with
317 <tt>-march=penryn</tt>.</li>
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame^]318
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]319<li>The X86 backend now does a number of optimizations that aim to avoid
320 converting numbers back and forth from SSE registers to the X87 floating
321 point stack.</li>
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame^]322
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]323<li>The X86 backend supports stack realignment, which is particularly useful for
324 vector code on OS's without 16-byte aligned stacks.</li>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]325
326<li>The X86 backend now supports the "sseregparm" options in GCC, which allow
327 functions to be tagged as passing floating point values in SSE
328 registers.</li>
329
330<li>Trampolines (taking the address of a nested function) now work on
331 Linux/x86-64.</li>
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame^]332
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]333<li><tt>__builtin_prefetch</tt> is now compiled into the appropriate prefetch
334 instructions instead of being ignored.</li>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]335
Dan Gohman74e1ff52008-06-05 16:15:39 +0000[diff] [blame]336<li>128-bit integers are now supported on x86-64 targets.</li>
337
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]338<li>The register allocator can now rematerialize PIC-base computations.</li>
339
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]340</ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]341
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]342</div>
343
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]344<!--=========================================================================-->
345<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]346<a name="targetspecific">Other Target Specific Improvements</a>
347</div>
348
349<div class="doc_text">
350<p>New target-specific features include:
351</p>
352
353<ul>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]354<li>The LLVM C backend now supports vector code.</li>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]355
356
357</ul>
358
359</div>
360
361
362
363<!--=========================================================================-->
364<div class="doc_subsection">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]365<a name="otherimprovements">Other Improvements</a>
366</div>
367
368<div class="doc_text">
369<p>New features include:
370</p>
371
372<ul>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]373<li>LLVM now builds with GCC 4.3.</li>
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]374<li><tt>llvm2cpp</tt> tool has been folded into llc, use
375 <tt>llc -march=cpp</tt></li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]376</ul>
377
378</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]379
380<!-- *********************************************************************** -->
381<div class="doc_section">
382 <a name="portability">Portability and Supported Platforms</a>
383</div>
384<!-- *********************************************************************** -->
385
386<div class="doc_text">
387
388<p>LLVM is known to work on the following platforms:</p>
389
390<ul>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]391<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]392 (and probably other unix-like systems).</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]393<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]394 64-bit modes.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]395<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]396<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
397 support is available for native builds with Visual C++).</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]398<li>Sun UltraSPARC workstations running Solaris 10.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]399<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]400<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]401</ul>
402
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]403<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]404to the machine and operating system on which it is built. However, minor
405porting may be required to get LLVM to work on new platforms. We welcome your
406portability patches and reports of successful builds or error messages.</p>
407
408</div>
409
410<!-- *********************************************************************** -->
411<div class="doc_section">
412 <a name="knownproblems">Known Problems</a>
413</div>
414<!-- *********************************************************************** -->
415
416<div class="doc_text">
417
418<p>This section contains all known problems with the LLVM system, listed by
419component. As new problems are discovered, they will be added to these
420sections. If you run into a problem, please check the <a
421href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
422there isn't already one.</p>
423
424</div>
425
426<!-- ======================================================================= -->
427<div class="doc_subsection">
428 <a name="experimental">Experimental features included with this release</a>
429</div>
430
431<div class="doc_text">
432
433<p>The following components of this LLVM release are either untested, known to
434be broken or unreliable, or are in early development. These components should
435not be relied on, and bugs should not be filed against them, but they may be
436useful 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]437components, please contact us on the <a
438href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]439
440<ul>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]441<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]442<li>The LLC "<tt>-filetype=asm</tt>" (the default) is the only supported
443 value for this option.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]444</ul>
445
446</div>
447
448<!-- ======================================================================= -->
449<div class="doc_subsection">
450 <a name="x86-be">Known problems with the X86 back-end</a>
451</div>
452
453<div class="doc_text">
454
455<ul>
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame^]456 <li>The X86 backend does not yet support
457 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
458 floating point stack</a>. It supports the 'f' and 't' constraints, but not
459 'u'.</li>
460 <li>The X86 backend generates inefficient floating point code when configured to
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]461 generate code for systems that don't have SSE2.</li>
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame^]462 <li>Win64 codegeneration wasn't widely tested. Everything should work, but we
463 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
464 currently due
465 to <a href="http://llvm.org/PR2255">several</a>
466 <a href="http://llvm.org/PR2257">bugs</a> in FP stackifier
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]467</ul>
468
469</div>
470
471<!-- ======================================================================= -->
472<div class="doc_subsection">
473 <a name="ppc-be">Known problems with the PowerPC back-end</a>
474</div>
475
476<div class="doc_text">
477
478<ul>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]479<li>The Linux PPC32/ABI support needs testing for the interpreter and static
480compilation, and lacks support for debug information.</li>
481</ul>
482
483</div>
484
485<!-- ======================================================================= -->
486<div class="doc_subsection">
487 <a name="arm-be">Known problems with the ARM back-end</a>
488</div>
489
490<div class="doc_text">
491
492<ul>
493<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]494processors, thumb programs can crash or produce wrong
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]495results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
496<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
497</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]498<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]499programs compiled with LLVM. Please use more recent versions of QEMU.</li>
500</ul>
501
502</div>
503
504<!-- ======================================================================= -->
505<div class="doc_subsection">
506 <a name="sparc-be">Known problems with the SPARC back-end</a>
507</div>
508
509<div class="doc_text">
510
511<ul>
512<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
513 support the 64-bit SPARC ABI (-m64).</li>
514</ul>
515
516</div>
517
518<!-- ======================================================================= -->
519<div class="doc_subsection">
520 <a name="alpha-be">Known problems with the Alpha back-end</a>
521</div>
522
523<div class="doc_text">
524
525<ul>
526
527<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
528appropriate nops inserted to ensure restartability.</li>
529
530</ul>
531</div>
532
533<!-- ======================================================================= -->
534<div class="doc_subsection">
535 <a name="ia64-be">Known problems with the IA64 back-end</a>
536</div>
537
538<div class="doc_text">
539
540<ul>
541
542<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
543made where the argument is not 16-byte aligned, as required on IA64. (Strictly
544speaking this is not a bug in the IA64 back-end; it will also be encountered
545when building C++ programs using the C back-end.)</li>
546
547<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
548ABI compliant layout of v-tables</a>. In particular, it just stores function
549pointers instead of function descriptors in the vtable. This bug prevents
550mixing C++ code compiled with LLVM with C++ objects compiled by other C++
551compilers.</li>
552
553<li>There are a few ABI violations which will lead to problems when mixing LLVM
554output with code built with other compilers, particularly for floating-point
555programs.</li>
556
557<li>Defining vararg functions is not supported (but calling them is ok).</li>
558
559<li>The Itanium backend has bitrotted somewhat.</li>
560</ul>
561
562</div>
563
564<!-- ======================================================================= -->
565<div class="doc_subsection">
566 <a name="c-be">Known problems with the C back-end</a>
567</div>
568
569<div class="doc_text">
570
571<ul>
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]572<li><a href="http://llvm.org/PR802">The C backend has only basic support for
573 inline assembly code</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]574<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
575 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
576 C++ code compiled with LLC or native compilers.</li>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]577<li>The C backend does not support all exception handling constructs.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]578</ul>
579
580</div>
581
582
583<!-- ======================================================================= -->
584<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]585 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]586</div>
587
588<!-- _______________________________________________________________________ -->
589<div class="doc_subsubsection">Bugs</div>
590
591<div class="doc_text">
592
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]593<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
594Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]595llvmdev mailing list if you are interested.</p>
596
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]597<p>The only major language feature of GCC not supported by llvm-gcc is
598 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
599 are only supported on some targets. For example, trampolines are only
600 supported on some targets, which are used when you take the address of a
601 nested function.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]602
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]603<p>If you run into GCC extensions which are not supported, please let us know.
604</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]605
606</div>
607
608<!-- ======================================================================= -->
609<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]610 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]611</div>
612
613<div class="doc_text">
614
615<p>The C++ front-end is considered to be fully
616tested and works for a number of non-trivial programs, including LLVM
617itself, Qt, Mozilla, etc.</p>
618
619<ul>
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]620<li>Exception handling works well on the X86 and PowerPC targets, including
621x86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is
622supported on x86-64 linux, but that is disabled by default in this release.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]623</ul>
624
625</div>
626
627
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]628<!-- ======================================================================= -->
629<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]630 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]631</div>
632
633<div class="doc_text">
634The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
635technology and problems should be expected.
636<ul>
637<li>The Ada front-end currently only builds on x86-32. This is mainly due
638to lack of trampoline support (pointers to nested functions) on other platforms,
639however it <a href="http://llvm.org/PR2006">also fails to build on x86-64</a>
640which does support trampolines.</li>
641<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
642Workaround: configure with --disable-bootstrap.</li>
643<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
644fail (c380004 also fails with gcc-4.2 mainline).</li>
645<li>Many gcc specific Ada tests continue to crash the compiler.</li>
646<li>The -E binder option (exception backtraces)
647<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
648crashing if an exception is raised. Workaround: do not use -E.</li>
649<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
650or finish at a non-byte offset</a> in a record. Workaround: do not pack records
651or use representation clauses that result in a field of a non-discrete type
652starting or finishing in the middle of a byte.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]653<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers 'main'
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]654as generated by the Ada binder to be invalid</a>.
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]655Workaround: 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]656integers.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]657<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]658</ul>
659</div>
660
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]661<!-- *********************************************************************** -->
662<div class="doc_section">
663 <a name="additionalinfo">Additional Information</a>
664</div>
665<!-- *********************************************************************** -->
666
667<div class="doc_text">
668
669<p>A wide variety of additional information is available on the <a
670href="http://llvm.org">LLVM web page</a>, in particular in the <a
671href="http://llvm.org/docs/">documentation</a> section. The web page also
672contains versions of the API documentation which is up-to-date with the
673Subversion version of the source code.
674You can access versions of these documents specific to this release by going
675into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
676
677<p>If you have any questions or comments about LLVM, please feel free to contact
678us via the <a href="http://llvm.org/docs/#maillist"> mailing
679lists</a>.</p>
680
681</div>
682
683<!-- *********************************************************************** -->
684
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