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11 <div class="doc_title">LLVM 2.1 Release Notes</div>
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>
22 <div class="doc_author">
23 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
26 <!-- *********************************************************************** -->
27 <div class="doc_section">
28 <a name="intro">Introduction</a>
30 <!-- *********************************************************************** -->
32 <div class="doc_text">
34 <p>This document contains the release notes for the LLVM compiler
35 infrastructure, release 2.1. Here we describe the status of LLVM, including
36 major improvements from the previous release and any known problems. All LLVM
37 releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
38 releases web site</a>.</p>
40 <p>For more information about LLVM, including information about the latest
41 release, please check out the <a href="http://llvm.org/">main LLVM
42 web site</a>. If you have questions or comments, the <a
43 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
44 list</a> is a good place to send them.</p>
46 <p>Note that if you are reading this file from a Subversion checkout or the
47 main LLVM web page, this document applies to the <i>next</i> release, not the
48 current one. To see the release notes for a specific releases, please see the
49 <a href="http://llvm.org/releases/">releases page</a>.</p>
53 <!-- *********************************************************************** -->
54 <div class="doc_section">
55 <a name="whatsnew">What's New?</a>
57 <!-- *********************************************************************** -->
59 <div class="doc_text">
61 <p>This is the twelfth public release of the LLVM Compiler Infrastructure.
62 It includes many features and refinements from LLVM 2.0.</p>
66 <!--=========================================================================-->
67 <div class="doc_subsection">
68 <a name="frontends">New Frontends</a>
71 <div class="doc_text">
73 <p>LLVM 2.1 brings two new beta C front-ends. First, Duncan, Anton and Devang
74 has started syncing up llvm-gcc with GCC 4.2, yielding "llvm-gcc 4.2" (creative,
75 huh?). llvm-gcc 4.2 has the promise to bring much better FORTRAN and Ada
76 support to LLVM as well as features like atomic builtins, OpenMP, and many other
77 things. Check it out!</p>
79 <p>Second, LLVM now includes its own native C and Objective-C front-end (C++ is
80 in progress, but is not very far along) code named "<a
81 href="http://clang.llvm.org/">clang</a>". This front-end has a number of great
82 features, primarily aimed at source-level analysis and speeding up compile-time.
83 At this point though, the LLVM Code Generator component is still very early in
84 development, so it's mostly useful for people looking to build source-level
85 analysis tools or source-to-source translators.</p>
89 <!--=========================================================================-->
90 <div class="doc_subsection">
91 <a name="optimizer">Optimizer Improvements</a>
94 <div class="doc_text">
96 <p>Some of the most noticable improvements this release have been in the
97 optimizer, speeding it up and making it more aggressive</p>
101 <li>Owen Anderson wrote the new MemoryDependenceAnalysis pass, which provides
102 a lazy, caching layer on top of alias analysis. He then used it to rewrite
103 DeadStoreElimination which resulted in significantly better compile time in
105 <li>Owen implemented the new GVN pass, which is also based on
106 MemoryDependenceAnalysis. This pass replaces GCSE/LoadVN in the standard
107 set of passes, providing more aggressive optimization at a some-what
108 improved compile-time cost.</li>
109 <li>Owen implemented GVN-PRE, a partial redundancy elimination algorithm that
110 shares some details with the new GVN pass. It is still in need of compile
111 time tuning, and is not turned on by default.</li>
112 <li>Devang merged ETForest and DomTree into a single easier to use data
114 <li>Nick Lewycky improved loop trip count analysis to handle many more common
121 <!--=========================================================================-->
122 <div class="doc_subsection">
123 <a name="codegen">Code Generator Improvements</a>
126 <div class="doc_text">
130 <li>Dale finished up the Tail Merging optimization in the code generator,
131 enabling it by default. This produces smaller code that is also faster in some
134 <li>Dan Gohman changed the way we represent vectors before legalization,
135 significantly simplifying the SelectionDAG representation for these and making
136 the code generator faster for vector code.</li>
138 <li>Evan remat rewrite (coalesced intervals + folding of remat'd loads) and
139 live intervals improvements.</li>
141 <li>Dan Gohman contributed support for better alignment and volatility handling
142 in the code generator, and significantly enhanced alignment analysis for SSE
143 load/store instructions.</li>
145 <li>Christopher Lamb virtual register sub-register support, better truncates and
148 <li>Duraid Madina contributed a new "bigblock" register allocator, and Roman
149 Levenstein contributed several big improvements. BigBlock is optimized for code
150 that uses very large basic blocks. It is slightly slower than the "local"
151 allocator, but produces much better code.</li>
153 <li>David Greene refactored the register allocator to split coalescing out from
154 allocation, making coalescers pluggable.</li>
161 <!--=========================================================================-->
162 <div class="doc_subsection">
163 <a name="targetspecific">Target Specific Improvements</a>
166 <div class="doc_text">
167 <p>New features include:
171 <li>Bruno Cardoso Lopes contributed initial MIPS support.</li>
172 <li>Bill Wendling added SSSE3 support.</li>
173 <li>New Target independent if converter, ARM uses it so far</li>
174 <li>Nicholas Geoffray contributed improved linux/ppc ABI and JIT support.</li>
175 <li>Dale Johannesen rewrote handling of 32-bit float values in the X86 backend
176 when using the floating point stack, fixing several nasty bugs.</li>
177 <li>Dan contributed rematerialization support for the X86 backend.</li>
183 <!--=========================================================================-->
184 <div class="doc_subsection">
185 <a name="llvmgccimprovements">llvm-gcc Improvements</a>
188 <div class="doc_text">
189 <p>New features include:
193 <li>Duncan and Anton exception handling in llvm-gcc 4.0/4.2</li>
195 <li>Devang and Duncan: Bitfields, pragma pack</li>
197 <li>Tanya implemented support for __attribute__((noinline)) in llvm-gcc, and
198 added support for generic variable annotations which are propagated into the
199 LLVM IR, e.g. "<tt>int X __attribute__((annotate("myproperty")));</tt>".</li>
201 <li>Sheng Zhou and Christopher Lamb implemented alias analysis support for
202 'restrict' arguments to functions.</li>
204 <li>Duncan contributed support for trampolines (pointers to nested functions),
205 currently only supported on x86 target.</li>
207 <li> Lauro Ramos Venancio contributed support to encode alignment info in
208 load and store instructions.</li>
214 <!--=========================================================================-->
215 <div class="doc_subsection">
216 <a name="coreimprovements">LLVM Core Improvements</a>
219 <div class="doc_text">
220 <p>New features include:
224 <li>Neil Booth APFloat, foundation for long double support that will be wrapped
225 up in 2.2. Dale contributed most of long double support, will be enabled in
228 <li>LLVM now provides an LLVMBuilder class which makes it significantly easier
229 to create LLVM IR instructions.</li>
231 <li>Reid contributed support for intrinsics that take arbitrary integer typed
232 arguments, Dan Gohman and Chandler extended it to support FP and vectors.</li>
237 <!--=========================================================================-->
238 <div class="doc_subsection">
239 <a name="otherimprovements">Other Improvements</a>
242 <div class="doc_text">
243 <p>New features include:
247 <li>BrainF frontend by Sterling Stein.</li>
249 <li>David Green contributed a new --enable-expensive-checks configure option
250 which enables STL checking, and fixed several bugs exposed by it.</li>
255 <!-- *********************************************************************** -->
256 <div class="doc_section">
257 <a name="portability">Portability and Supported Platforms</a>
259 <!-- *********************************************************************** -->
261 <div class="doc_text">
263 <p>LLVM is known to work on the following platforms:</p>
266 <li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
267 (and probably other unix-like systems).</li>
268 <li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
270 <li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
271 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
272 support is available for native builds with Visual C++).</li>
273 <li>Sun UltraSPARC workstations running Solaris 8.</li>
274 <li>Alpha-based machines running Debian GNU/Linux.</li>
275 <li>Itanium-based machines running Linux and HP-UX.</li>
278 <p>The core LLVM infrastructure uses
279 <a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
280 to the machine and operating system on which it is built. However, minor
281 porting may be required to get LLVM to work on new platforms. We welcome your
282 portability patches and reports of successful builds or error messages.</p>
286 <!-- *********************************************************************** -->
287 <div class="doc_section">
288 <a name="knownproblems">Known Problems</a>
290 <!-- *********************************************************************** -->
292 <div class="doc_text">
294 <p>This section contains all known problems with the LLVM system, listed by
295 component. As new problems are discovered, they will be added to these
296 sections. If you run into a problem, please check the <a
297 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
298 there isn't already one.</p>
302 <!-- ======================================================================= -->
303 <div class="doc_subsection">
304 <a name="experimental">Experimental features included with this release</a>
307 <div class="doc_text">
309 <p>The following components of this LLVM release are either untested, known to
310 be broken or unreliable, or are in early development. These components should
311 not be relied on, and bugs should not be filed against them, but they may be
312 useful to some people. In particular, if you would like to work on one of these
313 components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
316 <li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in a
318 <li>C++ EH support is disabled for this release.</li>
319 <li>The MSIL backend is experimental.</li>
320 <li>The IA64 code generator is experimental.</li>
321 <li>The Alpha JIT is experimental.</li>
322 <li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
323 <tt>-filetype</tt> llc option.</li>
328 <!-- ======================================================================= -->
329 <div class="doc_subsection">
330 <a name="x86-be">Known problems with the X86 back-end</a>
333 <div class="doc_text">
336 <li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
337 assembly that uses the X86 floating point stack</a>.</li>
342 <!-- ======================================================================= -->
343 <div class="doc_subsection">
344 <a name="ppc-be">Known problems with the PowerPC back-end</a>
347 <div class="doc_text">
350 <li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
351 implement ordered FP comparisons</a>.</li>
352 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
353 compilation, and lacks support for debug information.</li>
358 <!-- ======================================================================= -->
359 <div class="doc_subsection">
360 <a name="arm-be">Known problems with the ARM back-end</a>
363 <div class="doc_text">
366 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
367 processors, thumb program can crash or produces wrong
368 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
369 <li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
371 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
372 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
377 <!-- ======================================================================= -->
378 <div class="doc_subsection">
379 <a name="sparc-be">Known problems with the SPARC back-end</a>
382 <div class="doc_text">
385 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
386 support the 64-bit SPARC ABI (-m64).</li>
391 <!-- ======================================================================= -->
392 <div class="doc_subsection">
393 <a name="alpha-be">Known problems with the Alpha back-end</a>
396 <div class="doc_text">
400 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
401 appropriate nops inserted to ensure restartability.</li>
406 <!-- ======================================================================= -->
407 <div class="doc_subsection">
408 <a name="ia64-be">Known problems with the IA64 back-end</a>
411 <div class="doc_text">
415 <li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
416 made where the argument is not 16-byte aligned, as required on IA64. (Strictly
417 speaking this is not a bug in the IA64 back-end; it will also be encountered
418 when building C++ programs using the C back-end.)</li>
420 <li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
421 ABI compliant layout of v-tables</a>. In particular, it just stores function
422 pointers instead of function descriptors in the vtable. This bug prevents
423 mixing C++ code compiled with LLVM with C++ objects compiled by other C++
426 <li>There are a few ABI violations which will lead to problems when mixing LLVM
427 output with code built with other compilers, particularly for floating-point
430 <li>Defining vararg functions is not supported (but calling them is ok).</li>
432 <li>The Itanium backend has bitrotted somewhat.</li>
437 <!-- ======================================================================= -->
438 <div class="doc_subsection">
439 <a name="c-be">Known problems with the C back-end</a>
442 <div class="doc_text">
445 <li><a href="http://llvm.org/PR802">The C backend does not support inline
446 assembly code</a>.</li>
452 <!-- ======================================================================= -->
453 <div class="doc_subsection">
454 <a name="c-fe">Known problems with the C front-end</a>
457 <!-- _______________________________________________________________________ -->
458 <div class="doc_subsubsection">Bugs</div>
460 <div class="doc_text">
462 <p>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time
463 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
464 llvmdev mailing list if you are interested.</p>
468 <!-- _______________________________________________________________________ -->
469 <div class="doc_subsubsection">
473 <div class="doc_text">
476 <li><p>"long double" is silently transformed by the front-end into "double". There
477 is no support for floating point data types of any size other than 32 and 64
480 <li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
481 See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
484 <li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
486 <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>
487 Nested functions are supported, but llvm-gcc does not support non-local
488 gotos or taking the address of a nested function.</li>
490 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
492 Declaring that functions have no side effects or that they can never
495 <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
496 <tt>constructor</tt>, <tt>destructor</tt>,
497 <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
498 <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noreturn</tt>, <tt>regparm</tt>
499 <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
500 <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
502 <b>Ignored:</b> <tt>noinline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
503 <tt>malloc</tt>, <tt>no_instrument_function</tt></li>
507 <li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
510 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
511 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
512 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
513 Other built-in functions.</li>
514 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
515 Specifying attributes of variables.</li>
516 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
517 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
518 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
519 Arrays whose length is computed at run time.</li>
520 <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>
521 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
522 <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>
523 <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>
524 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
525 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
526 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
527 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
528 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
529 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
530 <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>
531 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
532 <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>
533 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
534 <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>
535 <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>
536 <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>
537 <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>
538 <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>
539 <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>
540 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
541 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
542 or arrays as values.</li>
543 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
544 <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>
545 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
546 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
547 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
548 <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>
549 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
550 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Character-Escapes.html#Character%20Escapes">Character Escapes</a>: <code>\e</code> stands for the character <ESC>.</li>
551 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
552 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
553 <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>
554 <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>
555 <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>
556 <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>
557 <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>
558 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
563 <p>If you run into GCC extensions which have not been included in any of these
564 lists, please let us know (also including whether or not they work).</p>
568 <!-- ======================================================================= -->
569 <div class="doc_subsection">
570 <a name="c++-fe">Known problems with the C++ front-end</a>
573 <div class="doc_text">
575 <p>The C++ front-end is considered to be fully
576 tested and works for a number of non-trivial programs, including LLVM
577 itself, Qt, Mozilla, etc.</p>
580 <li>llvm-gcc4 only has partial support for <a href="http://llvm.org/PR870">C++
581 Exception Handling</a>, and it is not enabled by default.</li>
585 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
586 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
587 function and in the <tt>setjmp</tt> receiver function may not be run.
588 Objects in intervening stack frames will be destroyed, however (which is
589 better than most compilers).</li>
591 <li>The LLVM C++ front-end follows the <a
592 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
593 This document, which is not Itanium specific, specifies a standard for name
594 mangling, class layout, v-table layout, RTTI formats, and other C++
595 representation issues. Because we use this API, code generated by the LLVM
596 compilers should be binary compatible with machine code generated by other
597 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
598 <i>However</i>, the exception handling mechanism used by llvm-gcc3 is very
599 different from the model used in the Itanium ABI, so <b>exceptions will not
600 interact correctly</b>. </li>
608 <!-- *********************************************************************** -->
609 <div class="doc_section">
610 <a name="additionalinfo">Additional Information</a>
612 <!-- *********************************************************************** -->
614 <div class="doc_text">
616 <p>A wide variety of additional information is available on the <a
617 href="http://llvm.org">LLVM web page</a>, in particular in the <a
618 href="http://llvm.org/docs/">documentation</a> section. The web page also
619 contains versions of the API documentation which is up-to-date with the
620 Subversion version of the source code.
621 You can access versions of these documents specific to this release by going
622 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
624 <p>If you have any questions or comments about LLVM, please feel free to contact
625 us via the <a href="http://llvm.org/docs/#maillist"> mailing
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