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Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]7 <title>LLVM 2.1 Release Notes</title>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]8</head>
9<body>
10
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]11<div class="doc_title">LLVM 2.1 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
26<!-- *********************************************************************** -->
27<div class="doc_section">
28 <a name="intro">Introduction</a>
29</div>
30<!-- *********************************************************************** -->
31
32<div class="doc_text">
33
34<p>This document contains the release notes for the LLVM compiler
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]35infrastructure, release 2.1. Here we describe the status of LLVM, including
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]36major improvements from the previous release and any known problems. All LLVM
37releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
38releases web site</a>.</p>
39
40<p>For more information about LLVM, including information about the latest
41release, please check out the <a href="http://llvm.org/">main LLVM
42web site</a>. If you have questions or comments, the <a
43href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
44list</a> is a good place to send them.</p>
45
46<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]47main LLVM web page, this document applies to the <i>next</i> release, not the
48current one. To see the release notes for a specific releases, please see the
49<a href="http://llvm.org/releases/">releases page</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]50
51</div>
52
53<!-- *********************************************************************** -->
54<div class="doc_section">
55 <a name="whatsnew">What's New?</a>
56</div>
57<!-- *********************************************************************** -->
58
59<div class="doc_text">
60
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]61<p>This is the twelfth public release of the LLVM Compiler Infrastructure.
62It includes many features and refinements from LLVM 2.0.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]63
64</div>
65
66<!--=========================================================================-->
67<div class="doc_subsection">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]68<a name="frontends">New Frontends</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]69</div>
70
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]71<div class="doc_text">
72
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]73<p>LLVM 2.1 brings two new beta C front-ends. First, Duncan, Anton and Devang
Devang Patel2966bf32007-09-21 18:02:24 +0000[diff] [blame]74has started syncing up llvm-gcc with GCC 4.2, yielding "llvm-gcc 4.2" (creative,
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]75huh?). llvm-gcc 4.2 has the promise to bring much better FORTRAN and Ada
76support to LLVM as well as features like atomic builtins, OpenMP, and many other
77things. Check it out!</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]78
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]79<p>Second, LLVM now includes its own native C and Objective-C front-end (C++ is
80in progress, but is not very far along) code named "<a
81href="http://clang.llvm.org/">clang</a>". This front-end has a number of great
82features, primarily aimed at source-level analysis and speeding up compile-time.
83At this point though, the LLVM Code Generator component is still very early in
84development, so it's mostly useful for people looking to build source-level
85analysis tools or source-to-source translators.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]86
87</div>
88
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]89<!--=========================================================================-->
90<div class="doc_subsection">
91<a name="optimizer">Optimizer Improvements</a>
92</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]93
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]94<div class="doc_text">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]95
96<p>Some of the most noticable improvements this release have been in the
97optimizer, speeding it up and making it more aggressive</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]98
99<ul>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]100
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]101<li>Owen DSE and MemDep analysis</li>
102<li>Owen GVN</li>
103<li>Owen GVN-PRE, not in llvm-gcc</li>
104<li>Devang merged ETForest and DomTree into a single easier to use data
105structure.</li>
106<li>Nick Lewycky improved loop trip count analysis to handle many more common
107cases.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]108
109</ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]110
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]111</div>
112
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]113<!--=========================================================================-->
114<div class="doc_subsection">
115<a name="codegen">Code Generator Improvements</a>
116</div>
117
118<div class="doc_text">
119
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]120<ul>
121
122<li>Dale finished up the Tail Merging optimization in the code generator,
123enabling it by default. This produces smaller code that is also faster in some
124cases.</li>
125
126<li>Dan Gohman changed the way we represent vectors before legalization,
127significantly simplifying the SelectionDAG representation for these and making
128the code generator faster for vector code.</li>
129
Chris Lattner76dec102007-09-21 17:43:52 +0000[diff] [blame]130<li>Evan remat rewrite (coalesced intervals + folding of remat'd loads) and
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]131live intervals improvements.</li>
132
133<li>Dan Gohman contributed support for better alignment and volatility handling
134in the code generator, and significantly enhanced alignment analysis for SSE
135load/store instructions.</li>
136
137<li>Christopher Lamb virtual register sub-register support, better truncates and
138extends on X86.</li>
139
140<li>Duraid Madina contributed a new "bigblock" register allocator, and Roman
141Levenstein contributed several big improvements. BigBlock is optimized for code
142that uses very large basic blocks. It is slightly slower than the "local"
143allocator, but produces much better code.</li>
144
Chris Lattner76dec102007-09-21 17:43:52 +0000[diff] [blame]145<li>David Greene refactored the register allocator to split coalescing out from
146allocation, making coalescers pluggable.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]147
148</ul>
149
150</div>
151
152
153<!--=========================================================================-->
154<div class="doc_subsection">
155<a name="targetspecific">Target Specific Improvements</a>
156</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]157
158<div class="doc_text">
159<p>New features include:
160</p>
161
162<ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]163<li>Bruno Cardoso Lopes contributed initial MIPS support.</li>
164<li>Bill Wendling added SSSE3 support.</li>
165<li>New Target independent if converter, ARM uses it so far</li>
166<li>Nicholas Geoffray contributed improved linux/ppc ABI and JIT support.</li>
167<li>Dale Johannesen rewrote handling of 32-bit float values in the X86 backend
168when using the floating point stack, fixing several nasty bugs.</li>
169<li>Dan contributed rematerialization support for the X86 backend.</li>
170</ul>
171
172</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]173
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]174
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]175<!--=========================================================================-->
176<div class="doc_subsection">
177<a name="llvmgccimprovements">llvm-gcc Improvements</a>
178</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]179
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]180<div class="doc_text">
181<p>New features include:
182</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]183
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]184<ul>
185<li>Duncan and Anton exception handling in llvm-gcc 4.0/4.2</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]186
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]187<li>Devang and Duncan: Bitfields, pragma pack</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]188
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]189<li>Tanya implemented support for __attribute__((noinline)) in llvm-gcc, and
190added support for generic variable annotations which are propagated into the
191LLVM IR, e.g. "<tt>int X __attribute__((annotate("myproperty")));</tt>".</li>
192
193<li>Sheng Zhou and Christopher Lamb implemented alias analysis support for
194'restrict' arguments to functions.</li>
195
196<li>Duncan contributed support for trampolines (pointers to nested functions),
197currently only supported on x86 target.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]198
Devang Patel2966bf32007-09-21 18:02:24 +0000[diff] [blame]199<li> Lauro Ramos Venancio contributed support to encode alignment info in
200load and store instructions.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]201</ul>
202
203</div>
204
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]205
206<!--=========================================================================-->
207<div class="doc_subsection">
208<a name="coreimprovements">LLVM Core Improvements</a>
209</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]210
211<div class="doc_text">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]212<p>New features include:
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]213</p>
214
215<ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]216<li>Neil Booth APFloat, foundation for long double support that will be wrapped
217up in 2.2. Dale contributed most of long double support, will be enabled in
2182.2.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]219
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]220<li>LLVM now provides an LLVMBuilder class which makes it significantly easier
221to create LLVM IR instructions.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]222
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]223<li>Reid contributed support for intrinsics that take arbitrary integer typed
224arguments, Dan Gohman and Chandler extended it to support FP and vectors.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]225</ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]226
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]227</div>
228
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]229<!--=========================================================================-->
230<div class="doc_subsection">
231<a name="otherimprovements">Other Improvements</a>
232</div>
233
234<div class="doc_text">
235<p>New features include:
236</p>
237
238<ul>
239<li>BrainF frontend by Sterling Stein.</li>
240
241<li>David Green contributed a new --enable-expensive-checks configure option
242which enables STL checking, and fixed several bugs exposed by it.</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]243</ul>
244
245</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]246
247<!-- *********************************************************************** -->
248<div class="doc_section">
249 <a name="portability">Portability and Supported Platforms</a>
250</div>
251<!-- *********************************************************************** -->
252
253<div class="doc_text">
254
255<p>LLVM is known to work on the following platforms:</p>
256
257<ul>
258<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
259 (and probably other unix-like systems).</li>
260<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
261 64-bit modes.</li>
262<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
263<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
264 support is available for native builds with Visual C++).</li>
265<li>Sun UltraSPARC workstations running Solaris 8.</li>
266<li>Alpha-based machines running Debian GNU/Linux.</li>
267<li>Itanium-based machines running Linux and HP-UX.</li>
268</ul>
269
270<p>The core LLVM infrastructure uses
271<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
272to the machine and operating system on which it is built. However, minor
273porting may be required to get LLVM to work on new platforms. We welcome your
274portability patches and reports of successful builds or error messages.</p>
275
276</div>
277
278<!-- *********************************************************************** -->
279<div class="doc_section">
280 <a name="knownproblems">Known Problems</a>
281</div>
282<!-- *********************************************************************** -->
283
284<div class="doc_text">
285
286<p>This section contains all known problems with the LLVM system, listed by
287component. As new problems are discovered, they will be added to these
288sections. If you run into a problem, please check the <a
289href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
290there isn't already one.</p>
291
292</div>
293
294<!-- ======================================================================= -->
295<div class="doc_subsection">
296 <a name="experimental">Experimental features included with this release</a>
297</div>
298
299<div class="doc_text">
300
301<p>The following components of this LLVM release are either untested, known to
302be broken or unreliable, or are in early development. These components should
303not be relied on, and bugs should not be filed against them, but they may be
304useful to some people. In particular, if you would like to work on one of these
305components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
306
307<ul>
308<li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in in a
309 future release.</li>
310<li>C++ EH support is disabled for this release.</li>
311<li>The MSIL backend is experimental.</li>
312<li>The IA64 code generator is experimental.</li>
313<li>The Alpha JIT is experimental.</li>
314<li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
315 <tt>-filetype</tt> llc option.</li>
316</ul>
317
318</div>
319
320<!-- ======================================================================= -->
321<div class="doc_subsection">
322 <a name="x86-be">Known problems with the X86 back-end</a>
323</div>
324
325<div class="doc_text">
326
327<ul>
328<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
329 assembly that uses the X86 floating point stack</a>.</li>
330</ul>
331
332</div>
333
334<!-- ======================================================================= -->
335<div class="doc_subsection">
336 <a name="ppc-be">Known problems with the PowerPC back-end</a>
337</div>
338
339<div class="doc_text">
340
341<ul>
342<li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
343implement ordered FP comparisons</a>.</li>
344<li>The Linux PPC32/ABI support needs testing for the interpreter and static
345compilation, and lacks support for debug information.</li>
346</ul>
347
348</div>
349
350<!-- ======================================================================= -->
351<div class="doc_subsection">
352 <a name="arm-be">Known problems with the ARM back-end</a>
353</div>
354
355<div class="doc_text">
356
357<ul>
358<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
359processors, thumb program can crash or produces wrong
360results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
361<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
362</li>
363<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
364programs compiled with LLVM. Please use more recent versions of QEMU.</li>
365</ul>
366
367</div>
368
369<!-- ======================================================================= -->
370<div class="doc_subsection">
371 <a name="sparc-be">Known problems with the SPARC back-end</a>
372</div>
373
374<div class="doc_text">
375
376<ul>
377<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
378 support the 64-bit SPARC ABI (-m64).</li>
379</ul>
380
381</div>
382
383<!-- ======================================================================= -->
384<div class="doc_subsection">
385 <a name="alpha-be">Known problems with the Alpha back-end</a>
386</div>
387
388<div class="doc_text">
389
390<ul>
391
392<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
393appropriate nops inserted to ensure restartability.</li>
394
395</ul>
396</div>
397
398<!-- ======================================================================= -->
399<div class="doc_subsection">
400 <a name="ia64-be">Known problems with the IA64 back-end</a>
401</div>
402
403<div class="doc_text">
404
405<ul>
406
407<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
408made where the argument is not 16-byte aligned, as required on IA64. (Strictly
409speaking this is not a bug in the IA64 back-end; it will also be encountered
410when building C++ programs using the C back-end.)</li>
411
412<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
413ABI compliant layout of v-tables</a>. In particular, it just stores function
414pointers instead of function descriptors in the vtable. This bug prevents
415mixing C++ code compiled with LLVM with C++ objects compiled by other C++
416compilers.</li>
417
418<li>There are a few ABI violations which will lead to problems when mixing LLVM
419output with code built with other compilers, particularly for floating-point
420programs.</li>
421
422<li>Defining vararg functions is not supported (but calling them is ok).</li>
423
424<li>The Itanium backend has bitrotted somewhat.</li>
425</ul>
426
427</div>
428
429<!-- ======================================================================= -->
430<div class="doc_subsection">
431 <a name="c-be">Known problems with the C back-end</a>
432</div>
433
434<div class="doc_text">
435
436<ul>
437<li><a href="http://llvm.org/PR802">The C backend does not support inline
438 assembly code</a>.</li>
439</ul>
440
441</div>
442
443
444<!-- ======================================================================= -->
445<div class="doc_subsection">
446 <a name="c-fe">Known problems with the C front-end</a>
447</div>
448
449<!-- _______________________________________________________________________ -->
450<div class="doc_subsubsection">Bugs</div>
451
452<div class="doc_text">
453
454<p>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time
455Optimization</a> on most platforms "out-of-the-box". Please inquire on the
456llvmdev mailing list if you are interested.</p>
457
458</div>
459
460<!-- _______________________________________________________________________ -->
461<div class="doc_subsubsection">
462 Notes
463</div>
464
465<div class="doc_text">
466<ul>
467
468<li><p>"long double" is silently transformed by the front-end into "double". There
469is no support for floating point data types of any size other than 32 and 64
470bits.</p></li>
471
472<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
473 See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
474</li>
475
476<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
477 <ol>
478 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>: As in Algol and Pascal, lexical scoping of functions.<br>
479 Nested functions are supported, but llvm-gcc does not support non-local
480 gotos or taking the address of a nested function.</li>
481
482 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
483
484 Declaring that functions have no side effects or that they can never
485 return.<br>
486
487 <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
488 <tt>constructor</tt>, <tt>destructor</tt>,
489 <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
490 <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noreturn</tt>, <tt>regparm</tt>
491 <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
492 <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
493
494 <b>Ignored:</b> <tt>noinline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
495 <tt>malloc</tt>, <tt>no_instrument_function</tt></li>
496 </ol>
497</li>
498
499<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
500
501 <ol>
502 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
503 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
504 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
505 Other built-in functions.</li>
506 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
507 Specifying attributes of variables.</li>
508 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
509 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
510 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
511 Arrays whose length is computed at run time.</li>
512 <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>
513 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
514 <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>
515 <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>
516 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
517 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
518 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
519 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
520 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
521 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
522 <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>
523 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
524 <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>
525 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
526 <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>
527 <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>
528 <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>
529 <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>
530 <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>
531 <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>
532 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
533 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
534or arrays as values.</li>
535 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
536 <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>
537 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
538 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
539 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
540 <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>
541 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
542 <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>
543 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
544 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
545 <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>
546 <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>
547 <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>
548 <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>
549 <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>
550 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
551 </ol></li>
552
553</ul>
554
555<p>If you run into GCC extensions which have not been included in any of these
556lists, please let us know (also including whether or not they work).</p>
557
558</div>
559
560<!-- ======================================================================= -->
561<div class="doc_subsection">
562 <a name="c++-fe">Known problems with the C++ front-end</a>
563</div>
564
565<div class="doc_text">
566
567<p>The C++ front-end is considered to be fully
568tested and works for a number of non-trivial programs, including LLVM
569itself, Qt, Mozilla, etc.</p>
570
571<ul>
572<li>llvm-gcc4 only has partial support for <a href="http://llvm.org/PR870">C++
573Exception Handling</a>, and it is not enabled by default.</li>
574
575<!-- NO EH Support!
576
577<li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
578 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
579 function and in the <tt>setjmp</tt> receiver function may not be run.
580 Objects in intervening stack frames will be destroyed, however (which is
581 better than most compilers).</li>
582
583<li>The LLVM C++ front-end follows the <a
584 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
585 This document, which is not Itanium specific, specifies a standard for name
586 mangling, class layout, v-table layout, RTTI formats, and other C++
587 representation issues. Because we use this API, code generated by the LLVM
588 compilers should be binary compatible with machine code generated by other
589 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
590 <i>However</i>, the exception handling mechanism used by llvm-gcc3 is very
591 different from the model used in the Itanium ABI, so <b>exceptions will not
592 interact correctly</b>. </li>
593-->
594</ul>
595
596</div>
597
598
599
600<!-- *********************************************************************** -->
601<div class="doc_section">
602 <a name="additionalinfo">Additional Information</a>
603</div>
604<!-- *********************************************************************** -->
605
606<div class="doc_text">
607
608<p>A wide variety of additional information is available on the <a
609href="http://llvm.org">LLVM web page</a>, in particular in the <a
610href="http://llvm.org/docs/">documentation</a> section. The web page also
611contains versions of the API documentation which is up-to-date with the
612Subversion version of the source code.
613You can access versions of these documents specific to this release by going
614into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
615
616<p>If you have any questions or comments about LLVM, please feel free to contact
617us via the <a href="http://llvm.org/docs/#maillist"> mailing
618lists</a>.</p>
619
620</div>
621
622<!-- *********************************************************************** -->
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