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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
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]27<!-- *********************************************************************** -->
28<div class="doc_section">
29 <a name="intro">Introduction</a>
30</div>
31<!-- *********************************************************************** -->
32
33<div class="doc_text">
34
35<p>This document contains the release notes for the LLVM compiler
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]36infrastructure, release 2.2. Here we describe the status of LLVM, including
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]37major improvements from the previous release and any known problems. All LLVM
38releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
39releases web site</a>.</p>
40
41<p>For more information about LLVM, including information about the latest
42release, please check out the <a href="http://llvm.org/">main LLVM
43web site</a>. If you have questions or comments, the <a
44href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
45list</a> is a good place to send them.</p>
46
47<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]48main LLVM web page, this document applies to the <i>next</i> release, not the
49current one. To see the release notes for a specific releases, please see the
50<a href="http://llvm.org/releases/">releases page</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]51
52</div>
53
54<!-- *********************************************************************** -->
55<div class="doc_section">
56 <a name="whatsnew">What's New?</a>
57</div>
58<!-- *********************************************************************** -->
59
60<div class="doc_text">
61
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]62<p>This is the thirteenth public release of the LLVM Compiler Infrastructure.
63It includes many features and refinements from LLVM 2.1.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]64
65</div>
66
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]67<!-- Unfinished features in 2.2:
68 Index Set Splitting not enabled by default
69 Machine LICM
70 Machine Sinking
71 LegalizeDAGTypes
72 -->
73
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]74<!--=========================================================================-->
75<div class="doc_subsection">
Chris Lattner41bf8e92008-02-10 07:04:35 +0000[diff] [blame]76<a name="deprecation">Deprecated features in LLVM 2.2</a>
77</div>
78
79<div class="doc_text">
80
81<p>This is the last LLVM release to support llvm-gcc 4.0, llvm-upgrade, and
82llvmc in its current form. llvm-gcc 4.0 has been replaced with llvm-gcc 4.2.
83llvm-upgrade is useful for upgrading llvm 1.9 files to llvm 2.x syntax, but you
84can always use an old release to do this. llvmc is currently mostly useless in
85llvm 2.2, and will be redesigned or removed in llvm 2.3.</p>
86
87</div>
88
89<!--=========================================================================-->
90<div class="doc_subsection">
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]91<a name="frontends">llvm-gcc 4.0, llvm-gcc 4.2, and clang</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]92</div>
93
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]94<div class="doc_text">
95
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]96<p>LLVM 2.2 fully supports both the llvm-gcc 4.0 and llvm-gcc 4.2 front-ends (in
97LLVM 2.1, llvm-gcc 4.2 was beta). Since LLVM 2.1, the llvm-gcc 4.2 front-end
98has made leaps and bounds and is now at least as good as 4.0 in virtually every
99area, and is better in several areas (for example, exception handling
Chris Lattner4e1e7ca2008-02-11 07:21:08 +0000[diff] [blame]100correctness, support for Ada and Fortran, better ABI compatibility, etc). We
101strongly recommend that you
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]102migrate from llvm-gcc 4.0 to llvm-gcc 4.2 in this release cycle because
103<b>LLVM 2.2 is the last release that will support llvm-gcc 4.0</b>: LLVM 2.3
104will only support the llvm-gcc 4.2 front-end.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]105
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]106<p>The <a href="http://clang.llvm.org/">clang project</a> is an effort to build
107a set of new 'llvm native' front-end technologies for the LLVM optimizer
108and code generator. Currently, its C and Objective-C support is maturing
109nicely, and it has advanced source-to-source analysis and transformation
110capabilities. If you are interested in building source-level tools for C and
111Objective-C (and eventually C++), you should take a look. However, note that
112clang 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]113this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]114
115</div>
116
117<!--=========================================================================-->
118<div class="doc_subsection">
119<a name="majorfeatures">Major New Features</a>
120</div>
121
122<div class="doc_text">
123
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]124<p>LLVM 2.2 includes several major new capabilities:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]125
126<ul>
Scott Michelef9a9eb2008-02-11 21:05:47 +0000[diff] [blame]127<li>A research team led by Scott Michel in the Computer Systems Research
128Department at The Aerospace Corporation contributed the CellSPU backend, which
129generates code for the vector coprocessors on the Sony/Toshiba/IBM Cell BE
130processor. llvm-gcc 4.2 supports CellSPU as a 'configure' target and progress
131is being made so that libgcc.a compiles cleanly. Notable pieces still in
132development include full 64-bit integer and full double precision floating
133point support.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]134
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]135<li>Anton and Duncan significantly improved llvm-gcc 4.2 support for the GCC Ada
136(GNAT) and Fortran (gfortran) front-ends. These front-ends should still be considered
137experimental however: see the <a href="#knownproblems">list of known problems</a>.
138The release binaries do not contain either front-end: they need to be built from
Chris Lattnerb6eca482008-02-10 17:52:05 +0000[diff] [blame]139source (the Ada front-end only builds on x86-32 linux).</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]140
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]141<li>Dale contributed full support for long double on x86/x86-64 (where it is 80
142bits) and on Darwin PPC/PPC64 (where it is 128 bits). In previous LLVM
143releases, llvm-gcc silently mapped long double to double.</li>
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]144
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]145<li>Gordon Henriksen rewrote most of the <a href="GarbageCollection.html"
146>Accurate Garbage Collection</a> code in the code generator, making the
Gabor Greif08f9d042008-02-10 20:08:16 +0000[diff] [blame]147generated code more efficient and adding support for the OCaml garbage collector
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]148metadata format.</li>
149
150<li>Christopher Lamb contributed support for multiple address spaces in LLVM
151IR. This is useful for supporting targets that have 'near' vs 'far' pointers,
152'RAM' vs 'ROM' pointers, or that have non-local memory that can be accessed with
153special instructions.</li>
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]154
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]155<li>LLVM now includes a new set of detailed <a
156href="tutorial/index.html">tutorials</a>, which explain how to implement a
157language with LLVM and shows how to use several important APIs.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]158
Chris Lattner5ba16862008-02-10 08:18:42 +0000[diff] [blame]159</ul>
160
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]161</div>
162
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]163<!--=========================================================================-->
164<div class="doc_subsection">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]165<a name="coreimprovements">LLVM Core Improvements</a>
166</div>
167
168<div class="doc_text">
169<p>New features include:
170</p>
171
172<ul>
Gabor Greif08f9d042008-02-10 20:08:16 +0000[diff] [blame]173<li>Gordon contributed support for C and OCaml Bindings for the basic LLVM IR
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]174construction routines as well as several other auxiliary APIs.</li>
175
176<li>Anton added readnone/readonly attributes for modeling function side effects.
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]177Duncan hooked up GCC's pure/const attributes to them and enhanced mod/ref
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]178analysis to use them.</li>
179
180<li>Devang added LLVMFoldingBuilder, a version of LLVMBuilder that implicitly
181simplifies the code as it is constructed.</li>
182
183<li>Ted Kremenek added a framework for generic object serialization to bitcode
184files. This support is only used by clang right now for ASTs but is extensible
185and could be used for serializing arbitrary other data into bitcode files.</li>
186
187<li>Duncan improved TargetData to distinguish between the size/alignment of a
188type in a register, in memory according to the platform ABI, and in memory when
189we have a choice.</li>
190
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]191<li>Reid moved parameter attributes off of FunctionType and onto functions
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]192and calls. This makes it much easier to add attributes to a function in a
193transformation pass.</li>
194
195<li>Dan Gohman added support for vector sin, cos, and pow intrinsics.</li>
196
197</ul>
198
199</div>
200
201<!--=========================================================================-->
202<div class="doc_subsection">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]203<a name="codegen">Code Generator Improvements</a>
204</div>
205
206<div class="doc_text">
207
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]208<p>We put a significant amount of work into the code generator infrastructure,
209which allows us to implement more aggressive algorithms and make it run
210faster:</p>
Chris Lattner7d2b1102007-09-26 05:44:21 +0000[diff] [blame]211
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]212<ul>
213
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]214<li>Owen refactored the existing LLVM dominator and loop information code to
215allow it work on the machine code representation. He contributed support for
216dominator and loop information on machine code and merged the code for forward
217and backward dominator computation.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]218
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]219<li>Dan added support for emitting debug information with .file and .loc
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]220directives on platforms that support it, instead of emitting large tables in the .s
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]221file.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]222
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]223<li>Evan extended the DAG scheduler to model physical register dependencies
224explicitly and have the BURR scheduler pick a correct schedule based on the
225dependencies. This reduces our use of the 'flag' operand hack.</li>
Chris Lattner358c3272008-02-06 18:32:06 +0000[diff] [blame]226
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]227<li>Evan added initial support for register coalescing of subregister
228references.</li>
229
230<li>Rafael Espindola implemented initial support for a new 'byval' attribute,
231which allows more efficient by-value argument passing in the LLVM IR. Evan
232finished support for it and enabled it in the X86 (32- and 64-bit) and C
233backends.</li>
234
235<li>The LLVM TargetInstrInfo class can now answer queries about the mod/ref and
236side-effect behavior of MachineInstr's. This information is inferred
237automatically by TableGen from .td files for all instructions with
238patterns.</li>
239
240<li>Evan implemented simple live interval splitting on basic block boundaries.
241This allows the register allocator to be more successful at keeping values in
242registers in some parts of a value's live range, even if they need to be spilled
243in some other block.</li>
244
245<li>The new MachineRegisterInfo.h class provides support for efficiently
246iterating over all defs/uses of a register, and this information is
247automatically kept up-to-date. This support is similar to the use_iterator in
248the LLVM IR level.</li>
249
250<li>The MachineInstr, MachineOperand and TargetInstrDesc classes are simpler,
251more consistent, and better documented.</li>
252</ul>
253
254</div>
255
256<!--=========================================================================-->
257<div class="doc_subsection">
258<a name="optimizer">Optimizer Improvements</a>
259</div>
260
261<div class="doc_text">
262
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]263<p>In addition to a huge array of bug fixes and minor performance tweaks, the
264LLVM 2.2 optimizers support a few major enhancements:</p>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]265
266<ul>
267
268<li>Daniel Berlin and Curtis Dunham rewrote Andersen's alias analysis to be
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]269several orders of magnitude faster, and implemented Offline Variable
270Substitution and Lazy Cycle Detection. Note that Andersen's is not enabled in
271llvm-gcc by default, but can be accessed through 'opt'.</li>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]272
273<li>Dan Gohman contributed several enhancements to Loop Strength Reduction (LSR)
Chris Lattner4e1e7ca2008-02-11 07:21:08 +0000[diff] [blame]274to make it more aggressive with SSE intrinsics and when induction variables are
275used by non-memory instructions.</li>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]276
277<li>Evan added support for simple exit value substitution to LSR.</li>
278
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]279<li>Evan enhanced LSR to support induction variable reuse when the induction
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]280variables have different widths.</li>
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]281
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]282</ul>
283
284</div>
285
286
287<!--=========================================================================-->
288<div class="doc_subsection">
289<a name="targetspecific">Target Specific Improvements</a>
290</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]291
292<div class="doc_text">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]293<p>New target-specific features include:
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]294</p>
295
296<ul>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]297<li>Evan contributed support to the X86 backend to model the mod/ref behavior
298of the EFLAGS register explicitly in all instructions. This gives more freedom
299to the scheduler, and is a more explicit way to model the instructions.</li>
Chris Lattner56ca2d72008-02-11 07:27:21 +0000[diff] [blame]300<li>Dale contributed support for exception handling on Darwin/PPC and he and
301Anton got x86-64 working.</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]302<li>Evan turned on if-conversion by default for ARM, allowing LLVM to take
303advantage of its predication features.</li>
304<li>Bruno added PIC support to the MIPS backend, fixed many bugs and improved
305support for architecture variants.</li>
306<li>Arnold Schwaighofer added support for X86 tail calls (limitations?
307details?).</li>
308<li>Evan contributed several enhancements to Darwin/x86 debug information,
309and improvements at -O0 (details?).</li>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]310<li>Duncan added x86-64 support for trampolines (pointers to nested functions).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]311</ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]312
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]313</div>
314
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]315<!--=========================================================================-->
316<div class="doc_subsection">
317<a name="otherimprovements">Other Improvements</a>
318</div>
319
320<div class="doc_text">
321<p>New features include:
322</p>
323
324<ul>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]325<li>Gordon expanded and updated the <a href="Passes.html">LLVM Analysis and
326Transformation Passes</a> reference to include descriptions for each pass.</li>
327
328<li>We rewrote the lexer and parser used by TableGen to make them simpler
329and cleaner. This gives tblgen support for 'caret diagnostics'. The .ll file
330lexer was also rewritten to support caret diagnostics but doesn't use this
331support yet.</li>
332
333<li>Dale has been grinding through the GCC testsuite, and marked many
334LLVM-incompatible tests as not-to-be-run (for example, if they are grepping
335through some GCC dump file that LLVM doesn't produce), he also found and fixed
336many LLVM bugs exposed by the testsuite.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]337</ul>
338
339</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]340
341<!-- *********************************************************************** -->
342<div class="doc_section">
343 <a name="portability">Portability and Supported Platforms</a>
344</div>
345<!-- *********************************************************************** -->
346
347<div class="doc_text">
348
349<p>LLVM is known to work on the following platforms:</p>
350
351<ul>
352<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
353 (and probably other unix-like systems).</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]354<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]355 64-bit modes.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]356<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]357<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
358 support is available for native builds with Visual C++).</li>
359<li>Sun UltraSPARC workstations running Solaris 8.</li>
360<li>Alpha-based machines running Debian GNU/Linux.</li>
361<li>Itanium-based machines running Linux and HP-UX.</li>
362</ul>
363
364<p>The core LLVM infrastructure uses
365<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
366to the machine and operating system on which it is built. However, minor
367porting may be required to get LLVM to work on new platforms. We welcome your
368portability patches and reports of successful builds or error messages.</p>
369
370</div>
371
372<!-- *********************************************************************** -->
373<div class="doc_section">
374 <a name="knownproblems">Known Problems</a>
375</div>
376<!-- *********************************************************************** -->
377
378<div class="doc_text">
379
380<p>This section contains all known problems with the LLVM system, listed by
381component. As new problems are discovered, they will be added to these
382sections. If you run into a problem, please check the <a
383href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
384there isn't already one.</p>
385
386</div>
387
388<!-- ======================================================================= -->
389<div class="doc_subsection">
390 <a name="experimental">Experimental features included with this release</a>
391</div>
392
393<div class="doc_text">
394
395<p>The following components of this LLVM release are either untested, known to
396be broken or unreliable, or are in early development. These components should
397not be relied on, and bugs should not be filed against them, but they may be
398useful to some people. In particular, if you would like to work on one of these
399components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
400
401<ul>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]402<li>The <tt>-cee</tt> pass is known to be buggy and will be removed in
403 LLVM 2.3.</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]404<li>The MSIL, IA64, Alpha, and MIPS backends are experimental.</li>
405<li>The LLC "<tt>-filetype=asm</tt>" (the default) is the only supported
406 value for this option.</li>
407<li>The llvmc tool is not supported.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]408</ul>
409
410</div>
411
412<!-- ======================================================================= -->
413<div class="doc_subsection">
414 <a name="x86-be">Known problems with the X86 back-end</a>
415</div>
416
417<div class="doc_text">
418
419<ul>
420<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
421 assembly that uses the X86 floating point stack</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]422<li>The X86 backend occasionally has <a href="http://llvm.org/PR1649">alignment
423 problems</a> on operating systems that don't require 16-byte stack alignment
424 (including most non-darwin OS's like linux).</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]425<li>The X86 backend generates inefficient floating point code when configured to
426 generate code for systems that don't have SSE2.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]427</ul>
428
429</div>
430
431<!-- ======================================================================= -->
432<div class="doc_subsection">
433 <a name="ppc-be">Known problems with the PowerPC back-end</a>
434</div>
435
436<div class="doc_text">
437
438<ul>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]439<li>The Linux PPC32/ABI support needs testing for the interpreter and static
440compilation, and lacks support for debug information.</li>
441</ul>
442
443</div>
444
445<!-- ======================================================================= -->
446<div class="doc_subsection">
447 <a name="arm-be">Known problems with the ARM back-end</a>
448</div>
449
450<div class="doc_text">
451
452<ul>
453<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]454processors, thumb programs can crash or produce wrong
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]455results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
456<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
457</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]458<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]459programs compiled with LLVM. Please use more recent versions of QEMU.</li>
460</ul>
461
462</div>
463
464<!-- ======================================================================= -->
465<div class="doc_subsection">
466 <a name="sparc-be">Known problems with the SPARC back-end</a>
467</div>
468
469<div class="doc_text">
470
471<ul>
472<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
473 support the 64-bit SPARC ABI (-m64).</li>
474</ul>
475
476</div>
477
478<!-- ======================================================================= -->
479<div class="doc_subsection">
480 <a name="alpha-be">Known problems with the Alpha back-end</a>
481</div>
482
483<div class="doc_text">
484
485<ul>
486
487<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
488appropriate nops inserted to ensure restartability.</li>
489
490</ul>
491</div>
492
493<!-- ======================================================================= -->
494<div class="doc_subsection">
495 <a name="ia64-be">Known problems with the IA64 back-end</a>
496</div>
497
498<div class="doc_text">
499
500<ul>
501
502<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
503made where the argument is not 16-byte aligned, as required on IA64. (Strictly
504speaking this is not a bug in the IA64 back-end; it will also be encountered
505when building C++ programs using the C back-end.)</li>
506
507<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
508ABI compliant layout of v-tables</a>. In particular, it just stores function
509pointers instead of function descriptors in the vtable. This bug prevents
510mixing C++ code compiled with LLVM with C++ objects compiled by other C++
511compilers.</li>
512
513<li>There are a few ABI violations which will lead to problems when mixing LLVM
514output with code built with other compilers, particularly for floating-point
515programs.</li>
516
517<li>Defining vararg functions is not supported (but calling them is ok).</li>
518
519<li>The Itanium backend has bitrotted somewhat.</li>
520</ul>
521
522</div>
523
524<!-- ======================================================================= -->
525<div class="doc_subsection">
526 <a name="c-be">Known problems with the C back-end</a>
527</div>
528
529<div class="doc_text">
530
531<ul>
532<li><a href="http://llvm.org/PR802">The C backend does not support inline
533 assembly code</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]534<li><a href="http://llvm.org/PR1126">The C backend does not support vectors
535 yet</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]536<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
537 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
538 C++ code compiled with LLC or native compilers.</li>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]539<li>The C backend does not support all exception handling constructs.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]540</ul>
541
542</div>
543
544
545<!-- ======================================================================= -->
546<div class="doc_subsection">
547 <a name="c-fe">Known problems with the C front-end</a>
548</div>
549
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]550<!-- ======================================================================= -->
551<div class="doc_subsection">
552 <a name="ada-fe">Known problems with the Ada front-end</a>
553</div>
554
555<div class="doc_text">
556The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
557technology and problems should be expected.
558<ul>
559<li>The Ada front-end currently only builds on x86-32. This is mainly due
560to lack of trampoline support (pointers to nested functions) on other platforms,
561however it <a href="http://llvm.org/PR2006">also fails to build on x86-64</a>
562which does support trampolines.</li>
563<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
564Workaround: configure with --disable-bootstrap.</li>
565<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
566fail (c380004 also fails with gcc-4.2 mainline).</li>
567<li>Many gcc specific Ada tests continue to crash the compiler.</li>
568<li>The -E binder option (exception backtraces)
569<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
570crashing if an exception is raised. Workaround: do not use -E.</li>
571<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
572or finish at a non-byte offset</a> in a record. Workaround: do not pack records
573or use representation clauses that result in a field of a non-discrete type
574starting or finishing in the middle of a byte.</li>
575<li>The lli interpreter <a href="http://llvm.org/PR2009">considers 'main'
576as generated by the Ada binder to be invalid</a>.
577Workaround: hand edit the file to use pointers for argv and envp rather than
578integers.</li>
579<li>The -fstack-check option <a href="http://llvm.org/PR2008">is ignored</a>.</li>
580</ul>
581</div>
582
583<!-- ======================================================================= -->
584<div class="doc_subsection">
585 <a name="fortran-fe">Known problems with the Fortran front-end</a>
586</div>
587
588<div class="doc_text">
589
590<ul>
591<li>The llvm-gcc 4.2 gfortran front-end supports a broad range of Fortran code, but does
592<a href="http://llvm.org/PR1971">not support EQUIVALENCE yet</a>.</li>
593</ul>
594</div>
595
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]596<!-- _______________________________________________________________________ -->
597<div class="doc_subsubsection">Bugs</div>
598
599<div class="doc_text">
600
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]601<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
602Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]603llvmdev mailing list if you are interested.</p>
604
605</div>
606
607<!-- _______________________________________________________________________ -->
608<div class="doc_subsubsection">
609 Notes
610</div>
611
612<div class="doc_text">
613<ul>
614
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]615<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
616 See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
617</li>
618
619<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
620 <ol>
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]621 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>:
622
623 As in Algol and Pascal, lexical scoping of functions.
624 Nested functions are supported, but llvm-gcc does not support
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]625 taking the address of a nested function (except on X86 targets)
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]626 or non-local gotos.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]627
628 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
629
630 Declaring that functions have no side effects or that they can never
631 return.<br>
632
Anton Korobeynikov08dcc472007-11-16 11:12:01 +0000[diff] [blame]633 <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
634 <tt>const</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]635 <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
Anton Korobeynikov08dcc472007-11-16 11:12:01 +0000[diff] [blame]636 <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noinline</tt>,
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]637 <tt>noreturn</tt>, <tt>nothrow</tt>, <tt>pure</tt>, <tt>regparm</tt>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]638 <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
639 <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
640
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]641 <b>Ignored:</b> <tt>malloc</tt>,
Anton Korobeynikov08dcc472007-11-16 11:12:01 +0000[diff] [blame]642 <tt>no_instrument_function</tt></li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]643 </ol>
644</li>
645
646<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
647
648 <ol>
649 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
650 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
651 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
652 Other built-in functions.</li>
653 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
654 Specifying attributes of variables.</li>
655 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
656 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
657 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
658 Arrays whose length is computed at run time.</li>
659 <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>
660 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
661 <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>
662 <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>
663 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
664 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
665 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
666 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
667 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
668 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
669 <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>
670 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
671 <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>
672 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
673 <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>
674 <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>
675 <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>
676 <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>
677 <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>
678 <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>
679 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
680 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
681or arrays as values.</li>
682 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
683 <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>
684 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
685 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
686 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
687 <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>
688 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
689 <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>
690 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
691 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
692 <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>
693 <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>
694 <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>
695 <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>
696 <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>
697 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
698 </ol></li>
699
700</ul>
701
702<p>If you run into GCC extensions which have not been included in any of these
703lists, please let us know (also including whether or not they work).</p>
704
705</div>
706
707<!-- ======================================================================= -->
708<div class="doc_subsection">
709 <a name="c++-fe">Known problems with the C++ front-end</a>
710</div>
711
712<div class="doc_text">
713
714<p>The C++ front-end is considered to be fully
715tested and works for a number of non-trivial programs, including LLVM
716itself, Qt, Mozilla, etc.</p>
717
718<ul>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]719<li>Exception handling only works well on the X86 and PowerPC targets.
720It works well for x86-64 darwin but not x86-64 linux.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]721</ul>
722
723</div>
724
725
726
727<!-- *********************************************************************** -->
728<div class="doc_section">
729 <a name="additionalinfo">Additional Information</a>
730</div>
731<!-- *********************************************************************** -->
732
733<div class="doc_text">
734
735<p>A wide variety of additional information is available on the <a
736href="http://llvm.org">LLVM web page</a>, in particular in the <a
737href="http://llvm.org/docs/">documentation</a> section. The web page also
738contains versions of the API documentation which is up-to-date with the
739Subversion version of the source code.
740You can access versions of these documents specific to this release by going
741into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
742
743<p>If you have any questions or comments about LLVM, please feel free to contact
744us via the <a href="http://llvm.org/docs/#maillist"> mailing
745lists</a>.</p>
746
747</div>
748
749<!-- *********************************************************************** -->
750
751<hr>
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