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