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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
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]100correctness, support for Ada and Fortran). We strongly recommend that you
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]101migrate from llvm-gcc 4.0 to llvm-gcc 4.2 in this release cycle because
102<b>LLVM 2.2 is the last release that will support llvm-gcc 4.0</b>: LLVM 2.3
103will only support the llvm-gcc 4.2 front-end.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]104
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]105<p>The <a href="http://clang.llvm.org/">clang project</a> is an effort to build
106a set of new 'llvm native' front-end technologies for the LLVM optimizer
107and code generator. Currently, its C and Objective-C support is maturing
108nicely, and it has advanced source-to-source analysis and transformation
109capabilities. If you are interested in building source-level tools for C and
110Objective-C (and eventually C++), you should take a look. However, note that
111clang 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]112this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]113
114</div>
115
116<!--=========================================================================-->
117<div class="doc_subsection">
118<a name="majorfeatures">Major New Features</a>
119</div>
120
121<div class="doc_text">
122
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]123<p>LLVM 2.2 includes several major new capabilities:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]124
125<ul>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]126<li>Scott Michel contributed an SPU backend, which generates code for the
127vector coprocessors on the Cell processor. (Status?)</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]128
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]129<li>Anton and Duncan significantly improved llvm-gcc 4.2 support for the GCC Ada
130(GNAT) and Fortran (gfortran) front-ends. These front-ends should still be considered
131experimental however: see the <a href="#knownproblems">list of known problems</a>.
132The release binaries do not contain either front-end: they need to be built from
133source (the Ada front-end only builds on x86-32 linux).
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]134
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]135<li>Dale contributed full support for long double on x86/x86-64 (where it is 80
136bits) and on Darwin PPC/PPC64 (where it is 128 bits). In previous LLVM
137releases, llvm-gcc silently mapped long double to double.</li>
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]138
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]139<li>Gordon Henriksen rewrote most of the <a href="GarbageCollection.html"
140>Accurate Garbage Collection</a> code in the code generator, making the
141generated code more efficient and adding support for the Ocaml garbage collector
142metadata format.</li>
143
144<li>Christopher Lamb contributed support for multiple address spaces in LLVM
145IR. This is useful for supporting targets that have 'near' vs 'far' pointers,
146'RAM' vs 'ROM' pointers, or that have non-local memory that can be accessed with
147special instructions.</li>
Chris Lattner527afe62008-02-09 22:58:07 +0000[diff] [blame]148
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]149<li>LLVM now includes a new set of detailed <a
150href="tutorial/index.html">tutorials</a>, which explain how to implement a
151language with LLVM and shows how to use several important APIs.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]152
Chris Lattner5ba16862008-02-10 08:18:42 +0000[diff] [blame]153</ul>
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.
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]171Duncan hooked up GCC's pure/const attributes to them and enhanced mod/ref
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]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
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]185<li>Reid moved parameter attributes off of FunctionType and onto functions
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]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
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]214directives on platforms that support it, instead of emitting large tables in the .s
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]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>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]303<li>Duncan added x86-64 support for trampolines (pointers to nested functions).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]304</ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]305
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]306</div>
307
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]308<!--=========================================================================-->
309<div class="doc_subsection">
310<a name="otherimprovements">Other Improvements</a>
311</div>
312
313<div class="doc_text">
314<p>New features include:
315</p>
316
317<ul>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]318<li>Gordon expanded and updated the <a href="Passes.html">LLVM Analysis and
319Transformation Passes</a> reference to include descriptions for each pass.</li>
320
321<li>We rewrote the lexer and parser used by TableGen to make them simpler
322and cleaner. This gives tblgen support for 'caret diagnostics'. The .ll file
323lexer was also rewritten to support caret diagnostics but doesn't use this
324support yet.</li>
325
326<li>Dale has been grinding through the GCC testsuite, and marked many
327LLVM-incompatible tests as not-to-be-run (for example, if they are grepping
328through some GCC dump file that LLVM doesn't produce), he also found and fixed
329many LLVM bugs exposed by the testsuite.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]330</ul>
331
332</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]333
334<!-- *********************************************************************** -->
335<div class="doc_section">
336 <a name="portability">Portability and Supported Platforms</a>
337</div>
338<!-- *********************************************************************** -->
339
340<div class="doc_text">
341
342<p>LLVM is known to work on the following platforms:</p>
343
344<ul>
345<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
346 (and probably other unix-like systems).</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]347<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]348 64-bit modes.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]349<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]350<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
351 support is available for native builds with Visual C++).</li>
352<li>Sun UltraSPARC workstations running Solaris 8.</li>
353<li>Alpha-based machines running Debian GNU/Linux.</li>
354<li>Itanium-based machines running Linux and HP-UX.</li>
355</ul>
356
357<p>The core LLVM infrastructure uses
358<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
359to the machine and operating system on which it is built. However, minor
360porting may be required to get LLVM to work on new platforms. We welcome your
361portability patches and reports of successful builds or error messages.</p>
362
363</div>
364
365<!-- *********************************************************************** -->
366<div class="doc_section">
367 <a name="knownproblems">Known Problems</a>
368</div>
369<!-- *********************************************************************** -->
370
371<div class="doc_text">
372
373<p>This section contains all known problems with the LLVM system, listed by
374component. As new problems are discovered, they will be added to these
375sections. If you run into a problem, please check the <a
376href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
377there isn't already one.</p>
378
379</div>
380
381<!-- ======================================================================= -->
382<div class="doc_subsection">
383 <a name="experimental">Experimental features included with this release</a>
384</div>
385
386<div class="doc_text">
387
388<p>The following components of this LLVM release are either untested, known to
389be broken or unreliable, or are in early development. These components should
390not be relied on, and bugs should not be filed against them, but they may be
391useful to some people. In particular, if you would like to work on one of these
392components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
393
394<ul>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]395<li>The <tt>-cee</tt> pass is known to be buggy and will be removed in
396 LLVM 2.3.</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]397<li>The MSIL, IA64, Alpha, and MIPS backends are experimental.</li>
398<li>The LLC "<tt>-filetype=asm</tt>" (the default) is the only supported
399 value for this option.</li>
400<li>The llvmc tool is not supported.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]401</ul>
402
403</div>
404
405<!-- ======================================================================= -->
406<div class="doc_subsection">
407 <a name="x86-be">Known problems with the X86 back-end</a>
408</div>
409
410<div class="doc_text">
411
412<ul>
413<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
414 assembly that uses the X86 floating point stack</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]415<li>The X86 backend occasionally has <a href="http://llvm.org/PR1649">alignment
416 problems</a> on operating systems that don't require 16-byte stack alignment
417 (including most non-darwin OS's like linux).</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]418<li>The X86 backend generates inefficient floating point code when configured to
419 generate code for systems that don't have SSE2.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]420</ul>
421
422</div>
423
424<!-- ======================================================================= -->
425<div class="doc_subsection">
426 <a name="ppc-be">Known problems with the PowerPC back-end</a>
427</div>
428
429<div class="doc_text">
430
431<ul>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]432<li>The Linux PPC32/ABI support needs testing for the interpreter and static
433compilation, and lacks support for debug information.</li>
434</ul>
435
436</div>
437
438<!-- ======================================================================= -->
439<div class="doc_subsection">
440 <a name="arm-be">Known problems with the ARM back-end</a>
441</div>
442
443<div class="doc_text">
444
445<ul>
446<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]447processors, thumb programs can crash or produce wrong
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]448results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
449<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
450</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]451<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]452programs compiled with LLVM. Please use more recent versions of QEMU.</li>
453</ul>
454
455</div>
456
457<!-- ======================================================================= -->
458<div class="doc_subsection">
459 <a name="sparc-be">Known problems with the SPARC back-end</a>
460</div>
461
462<div class="doc_text">
463
464<ul>
465<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
466 support the 64-bit SPARC ABI (-m64).</li>
467</ul>
468
469</div>
470
471<!-- ======================================================================= -->
472<div class="doc_subsection">
473 <a name="alpha-be">Known problems with the Alpha back-end</a>
474</div>
475
476<div class="doc_text">
477
478<ul>
479
480<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
481appropriate nops inserted to ensure restartability.</li>
482
483</ul>
484</div>
485
486<!-- ======================================================================= -->
487<div class="doc_subsection">
488 <a name="ia64-be">Known problems with the IA64 back-end</a>
489</div>
490
491<div class="doc_text">
492
493<ul>
494
495<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
496made where the argument is not 16-byte aligned, as required on IA64. (Strictly
497speaking this is not a bug in the IA64 back-end; it will also be encountered
498when building C++ programs using the C back-end.)</li>
499
500<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
501ABI compliant layout of v-tables</a>. In particular, it just stores function
502pointers instead of function descriptors in the vtable. This bug prevents
503mixing C++ code compiled with LLVM with C++ objects compiled by other C++
504compilers.</li>
505
506<li>There are a few ABI violations which will lead to problems when mixing LLVM
507output with code built with other compilers, particularly for floating-point
508programs.</li>
509
510<li>Defining vararg functions is not supported (but calling them is ok).</li>
511
512<li>The Itanium backend has bitrotted somewhat.</li>
513</ul>
514
515</div>
516
517<!-- ======================================================================= -->
518<div class="doc_subsection">
519 <a name="c-be">Known problems with the C back-end</a>
520</div>
521
522<div class="doc_text">
523
524<ul>
525<li><a href="http://llvm.org/PR802">The C backend does not support inline
526 assembly code</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]527<li><a href="http://llvm.org/PR1126">The C backend does not support vectors
528 yet</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]529<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
530 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
531 C++ code compiled with LLC or native compilers.</li>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]532<li>The C backend does not support all exception handling constructs.</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
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]543<!-- ======================================================================= -->
544<div class="doc_subsection">
545 <a name="ada-fe">Known problems with the Ada front-end</a>
546</div>
547
548<div class="doc_text">
549The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
550technology and problems should be expected.
551<ul>
552<li>The Ada front-end currently only builds on x86-32. This is mainly due
553to lack of trampoline support (pointers to nested functions) on other platforms,
554however it <a href="http://llvm.org/PR2006">also fails to build on x86-64</a>
555which does support trampolines.</li>
556<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
557Workaround: configure with --disable-bootstrap.</li>
558<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
559fail (c380004 also fails with gcc-4.2 mainline).</li>
560<li>Many gcc specific Ada tests continue to crash the compiler.</li>
561<li>The -E binder option (exception backtraces)
562<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
563crashing if an exception is raised. Workaround: do not use -E.</li>
564<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
565or finish at a non-byte offset</a> in a record. Workaround: do not pack records
566or use representation clauses that result in a field of a non-discrete type
567starting or finishing in the middle of a byte.</li>
568<li>The lli interpreter <a href="http://llvm.org/PR2009">considers 'main'
569as generated by the Ada binder to be invalid</a>.
570Workaround: hand edit the file to use pointers for argv and envp rather than
571integers.</li>
572<li>The -fstack-check option <a href="http://llvm.org/PR2008">is ignored</a>.</li>
573</ul>
574</div>
575
576<!-- ======================================================================= -->
577<div class="doc_subsection">
578 <a name="fortran-fe">Known problems with the Fortran front-end</a>
579</div>
580
581<div class="doc_text">
582
583<ul>
584<li>The llvm-gcc 4.2 gfortran front-end supports a broad range of Fortran code, but does
585<a href="http://llvm.org/PR1971">not support EQUIVALENCE yet</a>.</li>
586</ul>
587</div>
588
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]589<!-- _______________________________________________________________________ -->
590<div class="doc_subsubsection">Bugs</div>
591
592<div class="doc_text">
593
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]594<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
595Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]596llvmdev mailing list if you are interested.</p>
597
598</div>
599
600<!-- _______________________________________________________________________ -->
601<div class="doc_subsubsection">
602 Notes
603</div>
604
605<div class="doc_text">
606<ul>
607
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]608<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
609 See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
610</li>
611
612<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
613 <ol>
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]614 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>:
615
616 As in Algol and Pascal, lexical scoping of functions.
617 Nested functions are supported, but llvm-gcc does not support
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]618 taking the address of a nested function (except on X86 targets)
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]619 or non-local gotos.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]620
621 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
622
623 Declaring that functions have no side effects or that they can never
624 return.<br>
625
Anton Korobeynikov08dcc472007-11-16 11:12:01 +0000[diff] [blame]626 <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
627 <tt>const</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]628 <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
Anton Korobeynikov08dcc472007-11-16 11:12:01 +0000[diff] [blame]629 <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noinline</tt>,
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]630 <tt>noreturn</tt>, <tt>nothrow</tt>, <tt>pure</tt>, <tt>regparm</tt>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]631 <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
632 <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
633
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]634 <b>Ignored:</b> <tt>malloc</tt>,
Anton Korobeynikov08dcc472007-11-16 11:12:01 +0000[diff] [blame]635 <tt>no_instrument_function</tt></li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]636 </ol>
637</li>
638
639<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
640
641 <ol>
642 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
643 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
644 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
645 Other built-in functions.</li>
646 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
647 Specifying attributes of variables.</li>
648 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
649 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
650 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
651 Arrays whose length is computed at run time.</li>
652 <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>
653 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
654 <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>
655 <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>
656 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
657 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
658 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
659 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
660 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
661 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
662 <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>
663 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
664 <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>
665 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
666 <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>
667 <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>
668 <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>
669 <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>
670 <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>
671 <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>
672 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
673 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
674or arrays as values.</li>
675 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
676 <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>
677 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
678 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
679 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
680 <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>
681 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
682 <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>
683 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
684 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
685 <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>
686 <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>
687 <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>
688 <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>
689 <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>
690 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
691 </ol></li>
692
693</ul>
694
695<p>If you run into GCC extensions which have not been included in any of these
696lists, please let us know (also including whether or not they work).</p>
697
698</div>
699
700<!-- ======================================================================= -->
701<div class="doc_subsection">
702 <a name="c++-fe">Known problems with the C++ front-end</a>
703</div>
704
705<div class="doc_text">
706
707<p>The C++ front-end is considered to be fully
708tested and works for a number of non-trivial programs, including LLVM
709itself, Qt, Mozilla, etc.</p>
710
711<ul>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame^]712<li>Exception handling only works well on the X86 and PowerPC targets.
713It works well for x86-64 darwin but not x86-64 linux.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]714</ul>
715
716</div>
717
718
719
720<!-- *********************************************************************** -->
721<div class="doc_section">
722 <a name="additionalinfo">Additional Information</a>
723</div>
724<!-- *********************************************************************** -->
725
726<div class="doc_text">
727
728<p>A wide variety of additional information is available on the <a
729href="http://llvm.org">LLVM web page</a>, in particular in the <a
730href="http://llvm.org/docs/">documentation</a> section. The web page also
731contains versions of the API documentation which is up-to-date with the
732Subversion version of the source code.
733You can access versions of these documents specific to this release by going
734into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
735
736<p>If you have any questions or comments about LLVM, please feel free to contact
737us via the <a href="http://llvm.org/docs/#maillist"> mailing
738lists</a>.</p>
739
740</div>
741
742<!-- *********************************************************************** -->
743
744<hr>
745<address>
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