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Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]7 <title>LLVM 2.2 Release Notes</title>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]8</head>
9<body>
10
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]11<div class="doc_title">LLVM 2.2 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 Lattner92bd6442008-02-06 18:00:48 +0000[diff] [blame]26<h1><font color="red">THIS IS A WORK IN PROGRESS FOR THE LLVM 2.2
27RELEASE</font</h1>
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 Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]38infrastructure, release 2.2. 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 Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]64<p>This is the thirteenth public release of the LLVM Compiler Infrastructure.
65It includes many features and refinements from LLVM 2.1.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]66
67</div>
68
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]69<!-- Unfinished features in 2.2:
70 Index Set Splitting not enabled by default
71 Machine LICM
72 Machine Sinking
73 LegalizeDAGTypes
74 -->
75
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]76<!--=========================================================================-->
77<div class="doc_subsection">
Chris Lattner41bf8e92008-02-10 07:04:35 +0000[diff] [blame]78<a name="deprecation">Deprecated features in LLVM 2.2</a>
79</div>
80
81<div class="doc_text">
82
83<p>This is the last LLVM release to support llvm-gcc 4.0, llvm-upgrade, and
84llvmc in its current form. llvm-gcc 4.0 has been replaced with llvm-gcc 4.2.
85llvm-upgrade is useful for upgrading llvm 1.9 files to llvm 2.x syntax, but you
86can always use an old release to do this. llvmc is currently mostly useless in
87llvm 2.2, and will be redesigned or removed in llvm 2.3.</p>
88
89</div>
90
91<!--=========================================================================-->
92<div class="doc_subsection">
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]93<a name="frontends">llvm-gcc 4.0, llvm-gcc 4.2, and clang</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]94</div>
95
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]96<div class="doc_text">
97
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]98<p>LLVM 2.2 fully supports both the llvm-gcc 4.0 and llvm-gcc 4.2 front-ends (in
99LLVM 2.1, llvm-gcc 4.2 was beta). Since LLVM 2.1, the llvm-gcc 4.2 front-end
100has made leaps and bounds and is now at least as good as 4.0 in virtually every
101area, and is better in several areas (for example, exception handling
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]102correctness, support for Ada and FORTRAN). We strongly recommend that you
103migrate from llvm-gcc 4.0 to llvm-gcc 4.2 in this release cycle because
104<b>LLVM 2.2 is the last release that will support llvm-gcc 4.0</b>: LLVM 2.3
105will only support the llvm-gcc 4.2 front-end.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]106
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]107<p>The <a href="http://clang.llvm.org/">clang project</a> is an effort to build
108a set of new 'llvm native' front-end technologies for the LLVM optimizer
109and code generator. Currently, its C and Objective-C support is maturing
110nicely, and it has advanced source-to-source analysis and transformation
111capabilities. If you are interested in building source-level tools for C and
112Objective-C (and eventually C++), you should take a look. However, note that
113clang is not an official part of the LLVM 2.2 release. If you are interested in
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]114this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]115
116</div>
117
118<!--=========================================================================-->
119<div class="doc_subsection">
120<a name="majorfeatures">Major New Features</a>
121</div>
122
123<div class="doc_text">
124
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]125<p>LLVM 2.2 includes several major new capabilities:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]126
127<ul>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]128<li>Scott Michel contributed an SPU backend, which generates code for the
129vector coprocessors on the Cell processor. (Status?)</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]130
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]131<li>llvm-gcc 4.2 has significantly improved support for the GCC Ada (GNAT) and
132FORTRAN (gfortran) frontends. Duncan has the llvm-gcc 4.2 GNAT front-end
133supporting almost all of the ACATS testsuite (except 2 tests?). The llvm-gcc
1344.2 gfortran front-end supports a broad range of FORTRAN code, but does <a
135href="http://llvm.org/PR1971">not support EQUIVALENCE yet</a>.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]136
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]137<li>Dale contributed full support for long double on x86/x86-64 (where it is 80
138bits) and on Darwin PPC/PPC64 (where it is 128 bits). In previous LLVM
139releases, llvm-gcc silently mapped long double to double.</li>
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]140
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]141<li>Gordon Henriksen rewrote most of the <a href="GarbageCollection.html"
142>Accurate Garbage Collection</a> code in the code generator, making the
143generated code more efficient and adding support for the Ocaml garbage collector
144metadata format.</li>
145
146<li>Christopher Lamb contributed support for multiple address spaces in LLVM
147IR. This is useful for supporting targets that have 'near' vs 'far' pointers,
148'RAM' vs 'ROM' pointers, or that have non-local memory that can be accessed with
149special instructions.</li>
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]150
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]151<li>LLVM now includes a new set of detailed <a
152href="tutorial/index.html">tutorials</a>, which explain how to implement a
153language with LLVM and shows how to use several important APIs.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]154
Chris Lattner5ba16862008-02-10 08:18:42 +0000[diff] [blame^]155</ul>
156
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]157</div>
158
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]159<!--=========================================================================-->
160<div class="doc_subsection">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]161<a name="coreimprovements">LLVM Core Improvements</a>
162</div>
163
164<div class="doc_text">
165<p>New features include:
166</p>
167
168<ul>
169<li>Gordon contributed support for C and Ocaml Bindings for the basic LLVM IR
170construction routines as well as several other auxiliary APIs.</li>
171
172<li>Anton added readnone/readonly attributes for modeling function side effects.
173Duncan hooked up GCC's pure/const attributes to use them and enhanced mod/ref
174analysis to use them.</li>
175
176<li>Devang added LLVMFoldingBuilder, a version of LLVMBuilder that implicitly
177simplifies the code as it is constructed.</li>
178
179<li>Ted Kremenek added a framework for generic object serialization to bitcode
180files. This support is only used by clang right now for ASTs but is extensible
181and could be used for serializing arbitrary other data into bitcode files.</li>
182
183<li>Duncan improved TargetData to distinguish between the size/alignment of a
184type in a register, in memory according to the platform ABI, and in memory when
185we have a choice.</li>
186
187<li>Duncan moved parameter attributes off of FunctionType and onto functions
188and calls. This makes it much easier to add attributes to a function in a
189transformation pass.</li>
190
191<li>Dan Gohman added support for vector sin, cos, and pow intrinsics.</li>
192
193</ul>
194
195</div>
196
197<!--=========================================================================-->
198<div class="doc_subsection">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]199<a name="codegen">Code Generator Improvements</a>
200</div>
201
202<div class="doc_text">
203
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]204<p>We put a significant amount of work into the code generator infrastructure,
205which allows us to implement more aggressive algorithms and make it run
206faster:</p>
Chris Lattner7d2b1102007-09-26 05:44:21 +0000[diff] [blame]207
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]208<ul>
209
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]210<li>Owen refactored the existing LLVM dominator and loop information code to
211allow it work on the machine code representation. He contributed support for
212dominator and loop information on machine code and merged the code for forward
213and backward dominator computation.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]214
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]215<li>Dan added support for emitting debug information with .file and .loc
216directives on that support it, instead of emitting large tables in the .s
217file.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]218
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]219<li>Evan extended the DAG scheduler to model physical register dependencies
220explicitly and have the BURR scheduler pick a correct schedule based on the
221dependencies. This reduces our use of the 'flag' operand hack.</li>
Chris Lattner358c3272008-02-06 18:32:06 +0000[diff] [blame]222
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]223<li>Evan added initial support for register coalescing of subregister
224references.</li>
225
226<li>Rafael Espindola implemented initial support for a new 'byval' attribute,
227which allows more efficient by-value argument passing in the LLVM IR. Evan
228finished support for it and enabled it in the X86 (32- and 64-bit) and C
229backends.</li>
230
231<li>The LLVM TargetInstrInfo class can now answer queries about the mod/ref and
232side-effect behavior of MachineInstr's. This information is inferred
233automatically by TableGen from .td files for all instructions with
234patterns.</li>
235
236<li>Evan implemented simple live interval splitting on basic block boundaries.
237This allows the register allocator to be more successful at keeping values in
238registers in some parts of a value's live range, even if they need to be spilled
239in some other block.</li>
240
241<li>The new MachineRegisterInfo.h class provides support for efficiently
242iterating over all defs/uses of a register, and this information is
243automatically kept up-to-date. This support is similar to the use_iterator in
244the LLVM IR level.</li>
245
246<li>The MachineInstr, MachineOperand and TargetInstrDesc classes are simpler,
247more consistent, and better documented.</li>
248</ul>
249
250</div>
251
252<!--=========================================================================-->
253<div class="doc_subsection">
254<a name="optimizer">Optimizer Improvements</a>
255</div>
256
257<div class="doc_text">
258
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]259<p>In addition to a huge array of bug fixes and minor performance tweaks, the
260LLVM 2.2 optimizers support a few major enhancements:</p>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]261
262<ul>
263
264<li>Daniel Berlin and Curtis Dunham rewrote Andersen's alias analysis to be
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]265several orders of magnitude faster, and implemented Offline Variable
266Substitution and Lazy Cycle Detection. Note that Andersen's is not enabled in
267llvm-gcc by default, but can be accessed through 'opt'.</li>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]268
269<li>Dan Gohman contributed several enhancements to Loop Strength Reduction (LSR)
270to make it more aggressive with SSE intrinsics.</li>
271
272<li>Evan added support for simple exit value substitution to LSR.</li>
273
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]274<li>Evan enhanced LSR to support induction variable reuse when the induction
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]275variables have different widths.</li>
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]276
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]277</ul>
278
279</div>
280
281
282<!--=========================================================================-->
283<div class="doc_subsection">
284<a name="targetspecific">Target Specific Improvements</a>
285</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]286
287<div class="doc_text">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]288<p>New target-specific features include:
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]289</p>
290
291<ul>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]292<li>Evan contributed support to the X86 backend to model the mod/ref behavior
293of the EFLAGS register explicitly in all instructions. This gives more freedom
294to the scheduler, and is a more explicit way to model the instructions.</li>
295<li>Dale contributed support for exception handling on Darwin/x86-64 and
296Darwin/ppc.</li>
297<li>Evan turned on if-conversion by default for ARM, allowing LLVM to take
298advantage of its predication features.</li>
299<li>Bruno added PIC support to the MIPS backend, fixed many bugs and improved
300support for architecture variants.</li>
301<li>Arnold Schwaighofer added support for X86 tail calls (limitations?
302details?).</li>
303<li>Evan contributed several enhancements to Darwin/x86 debug information,
304and improvements at -O0 (details?).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]305</ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]306
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]307</div>
308
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]309<!--=========================================================================-->
310<div class="doc_subsection">
311<a name="otherimprovements">Other Improvements</a>
312</div>
313
314<div class="doc_text">
315<p>New features include:
316</p>
317
318<ul>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]319<li>Gordon expanded and updated the <a href="Passes.html">LLVM Analysis and
320Transformation Passes</a> reference to include descriptions for each pass.</li>
321
322<li>We rewrote the lexer and parser used by TableGen to make them simpler
323and cleaner. This gives tblgen support for 'caret diagnostics'. The .ll file
324lexer was also rewritten to support caret diagnostics but doesn't use this
325support yet.</li>
326
327<li>Dale has been grinding through the GCC testsuite, and marked many
328LLVM-incompatible tests as not-to-be-run (for example, if they are grepping
329through some GCC dump file that LLVM doesn't produce), he also found and fixed
330many LLVM bugs exposed by the testsuite.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]331</ul>
332
333</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]334
335<!-- *********************************************************************** -->
336<div class="doc_section">
337 <a name="portability">Portability and Supported Platforms</a>
338</div>
339<!-- *********************************************************************** -->
340
341<div class="doc_text">
342
343<p>LLVM is known to work on the following platforms:</p>
344
345<ul>
346<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
347 (and probably other unix-like systems).</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]348<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]349 64-bit modes.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]350<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]351<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
352 support is available for native builds with Visual C++).</li>
353<li>Sun UltraSPARC workstations running Solaris 8.</li>
354<li>Alpha-based machines running Debian GNU/Linux.</li>
355<li>Itanium-based machines running Linux and HP-UX.</li>
356</ul>
357
358<p>The core LLVM infrastructure uses
359<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
360to the machine and operating system on which it is built. However, minor
361porting may be required to get LLVM to work on new platforms. We welcome your
362portability patches and reports of successful builds or error messages.</p>
363
364</div>
365
366<!-- *********************************************************************** -->
367<div class="doc_section">
368 <a name="knownproblems">Known Problems</a>
369</div>
370<!-- *********************************************************************** -->
371
372<div class="doc_text">
373
374<p>This section contains all known problems with the LLVM system, listed by
375component. As new problems are discovered, they will be added to these
376sections. If you run into a problem, please check the <a
377href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
378there isn't already one.</p>
379
380</div>
381
382<!-- ======================================================================= -->
383<div class="doc_subsection">
384 <a name="experimental">Experimental features included with this release</a>
385</div>
386
387<div class="doc_text">
388
389<p>The following components of this LLVM release are either untested, known to
390be broken or unreliable, or are in early development. These components should
391not be relied on, and bugs should not be filed against them, but they may be
392useful to some people. In particular, if you would like to work on one of these
393components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
394
395<ul>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]396<li>The <tt>-cee</tt> pass is known to be buggy and will be removed in
397 LLVM 2.3.</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]398<li>The MSIL, IA64, Alpha, and MIPS backends are experimental.</li>
399<li>The LLC "<tt>-filetype=asm</tt>" (the default) is the only supported
400 value for this option.</li>
401<li>The llvmc tool is not supported.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]402</ul>
403
404</div>
405
406<!-- ======================================================================= -->
407<div class="doc_subsection">
408 <a name="x86-be">Known problems with the X86 back-end</a>
409</div>
410
411<div class="doc_text">
412
413<ul>
414<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
415 assembly that uses the X86 floating point stack</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]416<li>The X86 backend occasionally has <a href="http://llvm.org/PR1649">alignment
417 problems</a> on operating systems that don't require 16-byte stack alignment
418 (including most non-darwin OS's like linux).</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]419<li>The X86 backend generates inefficient floating point code when configured to
420 generate code for systems that don't have SSE2.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]421</ul>
422
423</div>
424
425<!-- ======================================================================= -->
426<div class="doc_subsection">
427 <a name="ppc-be">Known problems with the PowerPC back-end</a>
428</div>
429
430<div class="doc_text">
431
432<ul>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]433<li>The Linux PPC32/ABI support needs testing for the interpreter and static
434compilation, and lacks support for debug information.</li>
435</ul>
436
437</div>
438
439<!-- ======================================================================= -->
440<div class="doc_subsection">
441 <a name="arm-be">Known problems with the ARM back-end</a>
442</div>
443
444<div class="doc_text">
445
446<ul>
447<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]448processors, thumb programs can crash or produce wrong
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]449results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
450<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
451</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]452<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]453programs compiled with LLVM. Please use more recent versions of QEMU.</li>
454</ul>
455
456</div>
457
458<!-- ======================================================================= -->
459<div class="doc_subsection">
460 <a name="sparc-be">Known problems with the SPARC back-end</a>
461</div>
462
463<div class="doc_text">
464
465<ul>
466<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
467 support the 64-bit SPARC ABI (-m64).</li>
468</ul>
469
470</div>
471
472<!-- ======================================================================= -->
473<div class="doc_subsection">
474 <a name="alpha-be">Known problems with the Alpha back-end</a>
475</div>
476
477<div class="doc_text">
478
479<ul>
480
481<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
482appropriate nops inserted to ensure restartability.</li>
483
484</ul>
485</div>
486
487<!-- ======================================================================= -->
488<div class="doc_subsection">
489 <a name="ia64-be">Known problems with the IA64 back-end</a>
490</div>
491
492<div class="doc_text">
493
494<ul>
495
496<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
497made where the argument is not 16-byte aligned, as required on IA64. (Strictly
498speaking this is not a bug in the IA64 back-end; it will also be encountered
499when building C++ programs using the C back-end.)</li>
500
501<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
502ABI compliant layout of v-tables</a>. In particular, it just stores function
503pointers instead of function descriptors in the vtable. This bug prevents
504mixing C++ code compiled with LLVM with C++ objects compiled by other C++
505compilers.</li>
506
507<li>There are a few ABI violations which will lead to problems when mixing LLVM
508output with code built with other compilers, particularly for floating-point
509programs.</li>
510
511<li>Defining vararg functions is not supported (but calling them is ok).</li>
512
513<li>The Itanium backend has bitrotted somewhat.</li>
514</ul>
515
516</div>
517
518<!-- ======================================================================= -->
519<div class="doc_subsection">
520 <a name="c-be">Known problems with the C back-end</a>
521</div>
522
523<div class="doc_text">
524
525<ul>
526<li><a href="http://llvm.org/PR802">The C backend does not support inline
527 assembly code</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]528<li><a href="http://llvm.org/PR1126">The C backend does not support vectors
529 yet</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]530<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
531 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
532 C++ code compiled with LLC or native compilers.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]533</ul>
534
535</div>
536
537
538<!-- ======================================================================= -->
539<div class="doc_subsection">
540 <a name="c-fe">Known problems with the C front-end</a>
541</div>
542
543<!-- _______________________________________________________________________ -->
544<div class="doc_subsubsection">Bugs</div>
545
546<div class="doc_text">
547
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]548<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
549Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]550llvmdev mailing list if you are interested.</p>
551
552</div>
553
554<!-- _______________________________________________________________________ -->
555<div class="doc_subsubsection">
556 Notes
557</div>
558
559<div class="doc_text">
560<ul>
561
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]562<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
563 See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
564</li>
565
566<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
567 <ol>
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]568 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>:
569
570 As in Algol and Pascal, lexical scoping of functions.
571 Nested functions are supported, but llvm-gcc does not support
Duncan Sands6b761d32007-09-26 16:24:52 +0000[diff] [blame]572 taking the address of a nested function (except on the X86-32 target)
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]573 or non-local gotos.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]574
575 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
576
577 Declaring that functions have no side effects or that they can never
578 return.<br>
579
Anton Korobeynikov08dcc472007-11-16 11:12:01 +0000[diff] [blame]580 <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
581 <tt>const</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]582 <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
Anton Korobeynikov08dcc472007-11-16 11:12:01 +0000[diff] [blame]583 <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noinline</tt>,
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]584 <tt>noreturn</tt>, <tt>nothrow</tt>, <tt>pure</tt>, <tt>regparm</tt>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]585 <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
586 <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
587
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]588 <b>Ignored:</b> <tt>malloc</tt>,
Anton Korobeynikov08dcc472007-11-16 11:12:01 +0000[diff] [blame]589 <tt>no_instrument_function</tt></li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]590 </ol>
591</li>
592
593<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
594
595 <ol>
596 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
597 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
598 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
599 Other built-in functions.</li>
600 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
601 Specifying attributes of variables.</li>
602 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
603 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
604 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
605 Arrays whose length is computed at run time.</li>
606 <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>
607 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
608 <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>
609 <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>
610 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
611 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
612 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
613 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
614 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
615 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
616 <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>
617 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
618 <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>
619 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
620 <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>
621 <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>
622 <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>
623 <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>
624 <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>
625 <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>
626 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
627 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
628or arrays as values.</li>
629 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
630 <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>
631 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
632 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
633 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
634 <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>
635 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
636 <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>
637 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
638 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
639 <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>
640 <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>
641 <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>
642 <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>
643 <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>
644 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
645 </ol></li>
646
647</ul>
648
649<p>If you run into GCC extensions which have not been included in any of these
650lists, please let us know (also including whether or not they work).</p>
651
652</div>
653
654<!-- ======================================================================= -->
655<div class="doc_subsection">
656 <a name="c++-fe">Known problems with the C++ front-end</a>
657</div>
658
659<div class="doc_text">
660
661<p>The C++ front-end is considered to be fully
662tested and works for a number of non-trivial programs, including LLVM
663itself, Qt, Mozilla, etc.</p>
664
665<ul>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]666<li>Exception handling only works well on the X86 and PowerPC targets.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]667</ul>
668
669</div>
670
671
672
673<!-- *********************************************************************** -->
674<div class="doc_section">
675 <a name="additionalinfo">Additional Information</a>
676</div>
677<!-- *********************************************************************** -->
678
679<div class="doc_text">
680
681<p>A wide variety of additional information is available on the <a
682href="http://llvm.org">LLVM web page</a>, in particular in the <a
683href="http://llvm.org/docs/">documentation</a> section. The web page also
684contains versions of the API documentation which is up-to-date with the
685Subversion version of the source code.
686You can access versions of these documents specific to this release by going
687into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
688
689<p>If you have any questions or comments about LLVM, please feel free to contact
690us via the <a href="http://llvm.org/docs/#maillist"> mailing
691lists</a>.</p>
692
693</div>
694
695<!-- *********************************************************************** -->
696
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