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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
74start syncing up llvm-gcc with GCC 4.2, yielding "llvm-gcc 4.2" (creative,
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
120<p>foo</p>
121
122<ul>
123
124<li>Dale finished up the Tail Merging optimization in the code generator,
125enabling it by default. This produces smaller code that is also faster in some
126cases.</li>
127
128<li>Dan Gohman changed the way we represent vectors before legalization,
129significantly simplifying the SelectionDAG representation for these and making
130the code generator faster for vector code.</li>
131
132<li>Evan remat rewrite (coallesced intervals + folding of remat'd loads) and
133live intervals improvements.</li>
134
135<li>Dan Gohman contributed support for better alignment and volatility handling
136in the code generator, and significantly enhanced alignment analysis for SSE
137load/store instructions.</li>
138
139<li>Christopher Lamb virtual register sub-register support, better truncates and
140extends on X86.</li>
141
142<li>Duraid Madina contributed a new "bigblock" register allocator, and Roman
143Levenstein contributed several big improvements. BigBlock is optimized for code
144that uses very large basic blocks. It is slightly slower than the "local"
145allocator, but produces much better code.</li>
146
147<li>David Greene refactored the register allocator to split coallescing out from
148allocation, making coallescers pluggable.</li>
149
150</ul>
151
152</div>
153
154
155<!--=========================================================================-->
156<div class="doc_subsection">
157<a name="targetspecific">Target Specific Improvements</a>
158</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]159
160<div class="doc_text">
161<p>New features include:
162</p>
163
164<ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame^]165<li>Bruno Cardoso Lopes contributed initial MIPS support.</li>
166<li>Bill Wendling added SSSE3 support.</li>
167<li>New Target independent if converter, ARM uses it so far</li>
168<li>Nicholas Geoffray contributed improved linux/ppc ABI and JIT support.</li>
169<li>Dale Johannesen rewrote handling of 32-bit float values in the X86 backend
170when using the floating point stack, fixing several nasty bugs.</li>
171<li>Dan contributed rematerialization support for the X86 backend.</li>
172</ul>
173
174</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]175
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]176
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame^]177<!--=========================================================================-->
178<div class="doc_subsection">
179<a name="llvmgccimprovements">llvm-gcc Improvements</a>
180</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]181
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame^]182<div class="doc_text">
183<p>New features include:
184</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]185
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame^]186<ul>
187<li>Duncan and Anton exception handling in llvm-gcc 4.0/4.2</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]188
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame^]189<li>Devang and Duncan: Bitfields, pragma pack</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]190
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame^]191<li>Tanya implemented support for __attribute__((noinline)) in llvm-gcc, and
192added support for generic variable annotations which are propagated into the
193LLVM IR, e.g. "<tt>int X __attribute__((annotate("myproperty")));</tt>".</li>
194
195<li>Sheng Zhou and Christopher Lamb implemented alias analysis support for
196'restrict' arguments to functions.</li>
197
198<li>Duncan contributed support for trampolines (pointers to nested functions),
199currently only supported on x86 target.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]200
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</li>
226
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]227</ul>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame^]228
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]229</div>
230
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame^]231<!--=========================================================================-->
232<div class="doc_subsection">
233<a name="otherimprovements">Other Improvements</a>
234</div>
235
236<div class="doc_text">
237<p>New features include:
238</p>
239
240<ul>
241<li>BrainF frontend by Sterling Stein.</li>
242
243<li>David Green contributed a new --enable-expensive-checks configure option
244which enables STL checking, and fixed several bugs exposed by it.</li>
245
246</li>
247
248</ul>
249
250</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]251
252<!-- *********************************************************************** -->
253<div class="doc_section">
254 <a name="portability">Portability and Supported Platforms</a>
255</div>
256<!-- *********************************************************************** -->
257
258<div class="doc_text">
259
260<p>LLVM is known to work on the following platforms:</p>
261
262<ul>
263<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
264 (and probably other unix-like systems).</li>
265<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
266 64-bit modes.</li>
267<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
268<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
269 support is available for native builds with Visual C++).</li>
270<li>Sun UltraSPARC workstations running Solaris 8.</li>
271<li>Alpha-based machines running Debian GNU/Linux.</li>
272<li>Itanium-based machines running Linux and HP-UX.</li>
273</ul>
274
275<p>The core LLVM infrastructure uses
276<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
277to the machine and operating system on which it is built. However, minor
278porting may be required to get LLVM to work on new platforms. We welcome your
279portability patches and reports of successful builds or error messages.</p>
280
281</div>
282
283<!-- *********************************************************************** -->
284<div class="doc_section">
285 <a name="knownproblems">Known Problems</a>
286</div>
287<!-- *********************************************************************** -->
288
289<div class="doc_text">
290
291<p>This section contains all known problems with the LLVM system, listed by
292component. As new problems are discovered, they will be added to these
293sections. If you run into a problem, please check the <a
294href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
295there isn't already one.</p>
296
297</div>
298
299<!-- ======================================================================= -->
300<div class="doc_subsection">
301 <a name="experimental">Experimental features included with this release</a>
302</div>
303
304<div class="doc_text">
305
306<p>The following components of this LLVM release are either untested, known to
307be broken or unreliable, or are in early development. These components should
308not be relied on, and bugs should not be filed against them, but they may be
309useful to some people. In particular, if you would like to work on one of these
310components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
311
312<ul>
313<li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in in a
314 future release.</li>
315<li>C++ EH support is disabled for this release.</li>
316<li>The MSIL backend is experimental.</li>
317<li>The IA64 code generator is experimental.</li>
318<li>The Alpha JIT is experimental.</li>
319<li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
320 <tt>-filetype</tt> llc option.</li>
321</ul>
322
323</div>
324
325<!-- ======================================================================= -->
326<div class="doc_subsection">
327 <a name="x86-be">Known problems with the X86 back-end</a>
328</div>
329
330<div class="doc_text">
331
332<ul>
333<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
334 assembly that uses the X86 floating point stack</a>.</li>
335</ul>
336
337</div>
338
339<!-- ======================================================================= -->
340<div class="doc_subsection">
341 <a name="ppc-be">Known problems with the PowerPC back-end</a>
342</div>
343
344<div class="doc_text">
345
346<ul>
347<li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
348implement ordered FP comparisons</a>.</li>
349<li>The Linux PPC32/ABI support needs testing for the interpreter and static
350compilation, and lacks support for debug information.</li>
351</ul>
352
353</div>
354
355<!-- ======================================================================= -->
356<div class="doc_subsection">
357 <a name="arm-be">Known problems with the ARM back-end</a>
358</div>
359
360<div class="doc_text">
361
362<ul>
363<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
364processors, thumb program can crash or produces wrong
365results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
366<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
367</li>
368<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
369programs compiled with LLVM. Please use more recent versions of QEMU.</li>
370</ul>
371
372</div>
373
374<!-- ======================================================================= -->
375<div class="doc_subsection">
376 <a name="sparc-be">Known problems with the SPARC back-end</a>
377</div>
378
379<div class="doc_text">
380
381<ul>
382<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
383 support the 64-bit SPARC ABI (-m64).</li>
384</ul>
385
386</div>
387
388<!-- ======================================================================= -->
389<div class="doc_subsection">
390 <a name="alpha-be">Known problems with the Alpha back-end</a>
391</div>
392
393<div class="doc_text">
394
395<ul>
396
397<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
398appropriate nops inserted to ensure restartability.</li>
399
400</ul>
401</div>
402
403<!-- ======================================================================= -->
404<div class="doc_subsection">
405 <a name="ia64-be">Known problems with the IA64 back-end</a>
406</div>
407
408<div class="doc_text">
409
410<ul>
411
412<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
413made where the argument is not 16-byte aligned, as required on IA64. (Strictly
414speaking this is not a bug in the IA64 back-end; it will also be encountered
415when building C++ programs using the C back-end.)</li>
416
417<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
418ABI compliant layout of v-tables</a>. In particular, it just stores function
419pointers instead of function descriptors in the vtable. This bug prevents
420mixing C++ code compiled with LLVM with C++ objects compiled by other C++
421compilers.</li>
422
423<li>There are a few ABI violations which will lead to problems when mixing LLVM
424output with code built with other compilers, particularly for floating-point
425programs.</li>
426
427<li>Defining vararg functions is not supported (but calling them is ok).</li>
428
429<li>The Itanium backend has bitrotted somewhat.</li>
430</ul>
431
432</div>
433
434<!-- ======================================================================= -->
435<div class="doc_subsection">
436 <a name="c-be">Known problems with the C back-end</a>
437</div>
438
439<div class="doc_text">
440
441<ul>
442<li><a href="http://llvm.org/PR802">The C backend does not support inline
443 assembly code</a>.</li>
444</ul>
445
446</div>
447
448
449<!-- ======================================================================= -->
450<div class="doc_subsection">
451 <a name="c-fe">Known problems with the C front-end</a>
452</div>
453
454<!-- _______________________________________________________________________ -->
455<div class="doc_subsubsection">Bugs</div>
456
457<div class="doc_text">
458
459<p>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time
460Optimization</a> on most platforms "out-of-the-box". Please inquire on the
461llvmdev mailing list if you are interested.</p>
462
463</div>
464
465<!-- _______________________________________________________________________ -->
466<div class="doc_subsubsection">
467 Notes
468</div>
469
470<div class="doc_text">
471<ul>
472
473<li><p>"long double" is silently transformed by the front-end into "double". There
474is no support for floating point data types of any size other than 32 and 64
475bits.</p></li>
476
477<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
478 See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
479</li>
480
481<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
482 <ol>
483 <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>
484 Nested functions are supported, but llvm-gcc does not support non-local
485 gotos or taking the address of a nested function.</li>
486
487 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
488
489 Declaring that functions have no side effects or that they can never
490 return.<br>
491
492 <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
493 <tt>constructor</tt>, <tt>destructor</tt>,
494 <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
495 <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noreturn</tt>, <tt>regparm</tt>
496 <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
497 <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
498
499 <b>Ignored:</b> <tt>noinline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
500 <tt>malloc</tt>, <tt>no_instrument_function</tt></li>
501 </ol>
502</li>
503
504<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
505
506 <ol>
507 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
508 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
509 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
510 Other built-in functions.</li>
511 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
512 Specifying attributes of variables.</li>
513 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
514 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
515 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
516 Arrays whose length is computed at run time.</li>
517 <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>
518 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
519 <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>
520 <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>
521 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
522 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
523 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
524 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
525 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
526 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
527 <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>
528 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
529 <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>
530 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
531 <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>
532 <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>
533 <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>
534 <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>
535 <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>
536 <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>
537 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
538 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
539or arrays as values.</li>
540 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
541 <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>
542 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
543 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
544 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
545 <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>
546 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
547 <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>
548 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
549 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
550 <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>
551 <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>
552 <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>
553 <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>
554 <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>
555 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
556 </ol></li>
557
558</ul>
559
560<p>If you run into GCC extensions which have not been included in any of these
561lists, please let us know (also including whether or not they work).</p>
562
563</div>
564
565<!-- ======================================================================= -->
566<div class="doc_subsection">
567 <a name="c++-fe">Known problems with the C++ front-end</a>
568</div>
569
570<div class="doc_text">
571
572<p>The C++ front-end is considered to be fully
573tested and works for a number of non-trivial programs, including LLVM
574itself, Qt, Mozilla, etc.</p>
575
576<ul>
577<li>llvm-gcc4 only has partial support for <a href="http://llvm.org/PR870">C++
578Exception Handling</a>, and it is not enabled by default.</li>
579
580<!-- NO EH Support!
581
582<li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
583 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
584 function and in the <tt>setjmp</tt> receiver function may not be run.
585 Objects in intervening stack frames will be destroyed, however (which is
586 better than most compilers).</li>
587
588<li>The LLVM C++ front-end follows the <a
589 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
590 This document, which is not Itanium specific, specifies a standard for name
591 mangling, class layout, v-table layout, RTTI formats, and other C++
592 representation issues. Because we use this API, code generated by the LLVM
593 compilers should be binary compatible with machine code generated by other
594 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
595 <i>However</i>, the exception handling mechanism used by llvm-gcc3 is very
596 different from the model used in the Itanium ABI, so <b>exceptions will not
597 interact correctly</b>. </li>
598-->
599</ul>
600
601</div>
602
603
604
605<!-- *********************************************************************** -->
606<div class="doc_section">
607 <a name="additionalinfo">Additional Information</a>
608</div>
609<!-- *********************************************************************** -->
610
611<div class="doc_text">
612
613<p>A wide variety of additional information is available on the <a
614href="http://llvm.org">LLVM web page</a>, in particular in the <a
615href="http://llvm.org/docs/">documentation</a> section. The web page also
616contains versions of the API documentation which is up-to-date with the
617Subversion version of the source code.
618You can access versions of these documents specific to this release by going
619into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
620
621<p>If you have any questions or comments about LLVM, please feel free to contact
622us via the <a href="http://llvm.org/docs/#maillist"> mailing
623lists</a>.</p>
624
625</div>
626
627<!-- *********************************************************************** -->
628
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