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6 <title>LLVM 1.4 Release Notes</title>
10 <div class="doc_title">LLVM 1.4 Release Notes</div>
13 <li><a href="#intro">Introduction</a></li>
14 <li><a href="#whatsnew">What's New?</a></li>
15 <li><a href="GettingStarted.html">Installation Instructions</a></li>
16 <li><a href="#portability">Portability and Supported Platforms</a></li>
17 <li><a href="#knownproblems">Known Problems</a>
19 <li><a href="#experimental">Experimental features included in this
21 <li><a href="#core">Known problems with the LLVM Core</a>
22 <li><a href="#c-fe">Known problems with the C Front-end</a>
23 <li><a href="#c++-fe">Known problems with the C++ Front-end</a>
24 <li><a href="#x86-be">Known problems with the X86 Back-end</a>
25 <li><a href="#sparcv9-be">Known problems with the SparcV9 Back-end</a>
26 <li><a href="#c-be">Known problems with the C back-end</a>
28 <li><a href="#additionalinfo">Additional Information</a></li>
31 <div class="doc_author">
32 <p>Written by the <a href="http://llvm.cs.uiuc.edu">LLVM team</a><p>
35 <!-- *********************************************************************** -->
36 <div class="doc_section">
37 <a name="intro">Introduction</a>
39 <!-- *********************************************************************** -->
41 <div class="doc_text">
43 <p>This document contains the release notes for the LLVM compiler
44 infrastructure, release 1.4. Here we describe the status of LLVM, including any
45 known problems and bug fixes from the previous release. The most up-to-date
46 version of this document can be found on the <a
47 href="http://llvm.cs.uiuc.edu/releases/1.4/">LLVM 1.4 web site</a>. If you are
48 not reading this on the LLVM web pages, you should probably go there because
49 this document may be updated after the release.</p>
51 <p>For more information about LLVM, including information about potentially more
52 current releases, please check out the <a href="http://llvm.cs.uiuc.edu">main
53 web site</a>. If you have questions or comments, the <a
54 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
55 list</a> is a good place to send them.</p>
57 <p>Note that if you are reading this file from CVS, this document applies
58 to the <i>next</i> release, not the current one. To see the release notes for
59 the current or previous releases, see the <a
60 href="http://llvm.cs.uiuc.edu/releases/">releases page</a>.</p>
64 <!-- *********************************************************************** -->
65 <div class="doc_section">
66 <a name="whatsnew">What's New?</a>
68 <!-- *********************************************************************** -->
70 <div class="doc_text">
72 <p>This is the fifth public release of the LLVM compiler infrastructure.</p>
74 <p> At this time, LLVM is known to correctly compile and run all C & C++
75 SPEC CPU95 & 2000 benchmarks, the Olden benchmarks, and the Ptrdist
76 benchmarks, and <b>many</b> other C and C++ programs.</p>
80 <!--=========================================================================-->
81 <div class="doc_subsubsection">
82 <a name="newfeatures">This release implements the following new features:</a>
85 <div class="doc_text">
88 <li>The test/Programs hierarchy<a href="http://llvm.cs.uiuc.edu/PR257">has
89 been moved out of the main LLVM tree</a> into a separate CVS repo and
91 <li>LLVM now optimizes global variables significantly more than it did
93 <li>LLVM now includes the new '<tt>undef</tt>' value and <a
94 href="LangRef.html#i_unreachable"><tt>unreachable</tt></a> instruction,
95 which give the optimizer more information about the behavior of the
102 <!--=========================================================================-->
103 <div class="doc_subsubsection">
104 In this release, the following missing features were implemented:
107 <div class="doc_text">
110 <li><a href="http://llvm.cs.uiuc.edu/PR419">JIT interface should support arbitrary
116 <!--=========================================================================-->
117 <div class="doc_subsubsection">
118 <a name="qualityofimp">In this release, the following Quality of Implementation
119 issues were fixed:</a>
122 <div class="doc_text">
125 <li><a href="http://llvm.cs.uiuc.edu/PR426">[llvmg++] Tons of warnings are spewed when
126 linking to libstdc++</a></li>
127 <li><a href="http://llvm.cs.uiuc.edu/PR352">include/{Support,Config} ->
128 include/llvm/{Support,Config}</a></li>
133 <!--=========================================================================-->
134 <div class="doc_subsubsection">
135 In this release, the following build problems were fixed:
138 <div class="doc_text">
144 <!--=========================================================================-->
145 <div class="doc_subsubsection">
146 <a name="codequality">This release includes the following Code Quality
150 <div class="doc_text">
152 <li><a href="http://llvm.cs.uiuc.edu/PR362">Ugly code generated for
153 std::min/std::max</a></li>
157 <!--=========================================================================-->
158 <div class="doc_subsubsection">
159 <a name="bugfix">In this release, the following bugs in the previous release
163 <div class="doc_text">
165 <p>Bugs fixed in the LLVM Core:</p>
168 <li><a href="http://llvm.cs.uiuc.edu/PR420">[licm] LICM invalidates alias analysis info
169 and uses broken information</a> (optimizer crash)</li>
170 <li><a href="http://llvm.cs.uiuc.edu/PR422">[asmwriter] Asmwriter is really slow for
171 functions with lots of values</a></li>
172 <li><a href="http://llvm.cs.uiuc.edu/PR423">[anders-aa] Andersen's AA is completely
173 broken in LLVM 1.3</a></li>
174 <li><a href="http://llvm.cs.uiuc.edu/PR430">[bcwriter] Empty compaction tables
178 <p>Bugs in the C/C++ front-end:</p>
181 <li><a href="http://llvm.cs.uiuc.edu/PR445">[llvmg++] not enough templates are instantiated</a></li>
182 <li><a href="http://llvm.cs.uiuc.edu/PR450">[llvmg++] Extern const globals cannot be
183 marked 'constant' if they have nontrivial ctors or dtors</a></li>
186 <p>Bugs fixed in the Sparc V9 back-end:</p>
189 <li><a href="http://llvm.cs.uiuc.edu/PR428">[sparcv9] regalloc assertion
190 failure with certain indirect calls</a></li>
195 <!-- *********************************************************************** -->
196 <div class="doc_section">
197 <a name="portability">Portability and Supported Platforms</a>
199 <!-- *********************************************************************** -->
201 <div class="doc_text">
203 <p>LLVM is known to work in the following platforms:</p>
206 <li>Intel and AMD machines running Red Hat Linux and FreeBSD (and probably
207 other unix-like systems).</li>
208 <li>Sun UltraSPARC workstations running Solaris 8.</li>
209 <li>Intel and AMD machines running on Win32 with the Cygwin libraries.</li>
210 <li>PowerPC-based Mac OS X boxes, running 10.2 and above. Note that no JIT
211 support is available yet, and LLC support is beta. The C backend can be used
212 to produce stable code for this platform.</li>
215 <p>The core LLVM infrastructure uses
216 <a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
217 to the machine and operating system on which it is built. However, minor
218 porting may be required to get LLVM to work on new platforms. We welcome your
219 portability patches and reports of successful builds or error messages.</p>
221 <p>Note that the LLVM build system does not currently support directories with
222 spaces on them when running on Win32/cygwin. We strongly recommend running
223 LLVM and the C frontend out of a top-level directory without spaces (e.g.,
224 <tt>/cygdrive/c/llvm</tt>). Also, make sure to install <b>all</b> of the
225 cygwin packages. By default, many important tools are not installed that
226 are needed by the LLVM build process or test suite (e.g., /bin/time). Finally,
227 please make sure that there are no directories with spaces in them in your
228 PATH environment variable.</p>
232 <!-- *********************************************************************** -->
233 <div class="doc_section">
234 <a name="knownproblems">Known Problems</a>
236 <!-- *********************************************************************** -->
238 <div class="doc_text">
240 <p>This section contains all known problems with the LLVM system, listed by
241 component. As new problems are discovered, they will be added to these
242 sections. If you run into a problem, please check the <a
243 href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
244 there isn't already one.</p>
248 <!-- ======================================================================= -->
249 <div class="doc_subsection">
250 <a name="experimental">Experimental features included with this release</a>
253 <div class="doc_text">
255 <p>The following components of this LLVM release are either untested, known to
256 be broken or unreliable, or are in early development. These components should
257 not be relied on, and bugs should not be filed against them, but they may be
258 useful to some people. In particular, if you would like to work on one of these
259 components, please contact us on the llvmdev list.</p>
262 <li>The PowerPC backend is incomplete and is known to miscompile several SPEC
263 benchmarks. The file <tt>llvm/lib/Target/PowerPC/README.txt</tt> has
265 <li>The following passes are incomplete or buggy: <tt>-pgmdep, -memdep,
266 -ipmodref, -cee, -branch-combine, -instloops, -paths</tt></li>
267 <li>The <tt>-pre</tt> pass is incomplete (there are cases it doesn't handle that
268 it should) and not thoroughly tested.</li>
269 <li>The <tt>llvm-ar</tt> tool is incomplete and probably buggy.</li>
270 <li>The <tt>llvm-db</tt> tool is in a very early stage of development.</li>
275 <!-- ======================================================================= -->
276 <div class="doc_subsection">
277 <a name="core">Known problems with the LLVM Core</a>
280 <div class="doc_text">
284 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
287 <li>The JIT does not use mutexes to protect its internal data structures. As
288 such, execution of a threaded program could cause these data structures to be
291 <li>Linking in static archive files (.a files) is slow (there is no symbol
292 table in the archive).</li>
294 <li>The gccld program <a href="http://llvm.cs.uiuc.edu/PR139">does not link
295 objects/archives in the order specified on the command line.</a></li>
297 <li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not mark
298 values live across a setjmp as volatile</a>. This missing feature only affects
299 targets whose setjmp/longjmp libraries do not save and restore the entire
304 <!-- ======================================================================= -->
305 <div class="doc_subsection">
306 <a name="c-fe">Known problems with the C front-end</a>
309 <!-- _______________________________________________________________________ -->
310 <div class="doc_subsubsection">Bugs</div>
312 <div class="doc_text">
314 <li>C99 Variable sized arrays do not release stack memory when they go out of
315 scope. Thus, the following program may run out of stack space:
317 for (i = 0; i != 1000000; ++i) {
323 <li>Initialization of global union variables can only be done <a
324 href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=162">with the largest union
327 <li><a href="http://llvm.cs.uiuc.edu/PR244">[llvm-gcc] Error when an implicitly
328 external function is re-declared as static</a></li>
333 <!-- _______________________________________________________________________ -->
334 <div class="doc_subsubsection">
338 <div class="doc_text">
342 <li>Inline assembly is not yet supported.</li>
344 <li>"long double" is transformed by the front-end into "double". There is no
345 support for floating point data types of any size other than 32 and 64
348 <li>The following Unix system functionality has not been tested and may not
351 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
352 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
353 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
354 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
355 - These functions have not been tested.
358 <li>Although many GCC extensions are supported, some are not. In particular,
359 the following extensions are known to <b>not be</b> supported:
361 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
362 <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.</li>
363 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
364 <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>
365 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
366 <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>
367 <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>
368 <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>
369 <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>
370 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
371 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
374 <p>The following GCC extensions are <b>partially</b> supported. An ignored
375 attribute means that the LLVM compiler ignores the presence of the attribute,
376 but the code should still work. An unsupported attribute is one which is
377 ignored by the LLVM compiler and will cause a different interpretation of
381 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
382 Arrays whose length is computed at run time.<br>
383 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
385 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
387 Declaring that functions have no side effects or that they can never
390 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
391 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
392 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
394 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
395 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
396 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
398 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
399 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
400 <tt>fastcall</tt>, all other target specific attributes</li>
402 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
403 Specifying attributes of variables.<br>
404 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
405 <tt>deprecated</tt>, <tt>transparent_union</tt>,
406 <tt>unused</tt>, <tt>weak</tt><br>
408 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
409 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
410 <tt>vector_size</tt>, <tt>dllimport</tt>,
411 <tt>dllexport</tt>, all target specific attributes.</li>
413 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
414 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
415 <tt>deprecated</tt>, <tt>may_alias</tt><br>
417 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
418 all target specific attributes.</li>
420 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
421 Other built-in functions.<br>
422 We support all builtins which have a C language equivalent (e.g.,
423 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
424 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
425 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt>
426 (currently ignored). We also support builtins for ISO C99 floating
427 point comparison macros (e.g., <tt>__builtin_islessequal</tt>).</li>
430 <p>The following extensions <b>are</b> known to be supported:</p>
433 <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>
434 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
435 <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>
436 <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>
437 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
438 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
439 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
440 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
441 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
442 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
443 <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>
444 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
445 <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>
446 <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>
447 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
448 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
449 or arrays as values.</li>
450 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
451 <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>
452 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
453 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
454 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
455 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
456 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
457 <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>
458 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
459 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
460 <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>
461 <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>
462 <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>
463 <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>
464 <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>
465 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
470 <p>If you run into GCC extensions which have not been included in any of these
471 lists, please let us know (also including whether or not they work).</p>
475 <!-- ======================================================================= -->
476 <div class="doc_subsection">
477 <a name="c++-fe">Known problems with the C++ front-end</a>
480 <div class="doc_text">
482 <p>For this release, the C++ front-end is considered to be fully functional but
483 has not been tested as thoroughly as the C front-end. It has been tested and
484 works for a number of non-trivial programs, but there may be lurking bugs.
485 Please report any bugs or problems.</p>
489 <!-- _______________________________________________________________________ -->
490 <div class="doc_subsubsection">Bugs</div>
492 <div class="doc_text">
495 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
498 <li><b>IA-64 specific</b>: The C++ front-end does not use <a
499 href="http://llvm.cs.uiuc.edu/PR406">IA64 ABI compliant layout of v-tables</a>.
500 In particular, it just stores function pointers instead of function
501 descriptors in the vtable. This bug prevents mixing C++ code compiled with
502 LLVM with C++ objects compiled by other C++ compilers.</li>
508 <!-- _______________________________________________________________________ -->
509 <div class="doc_subsubsection">
513 <div class="doc_text">
517 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
518 parser is significantly more standards compliant (and picky) than prior GCC
519 versions. For more information, see the C++ section of the <a
520 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
522 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
523 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
524 function and in the <tt>setjmp</tt> receiver function may not be run.
525 Objects in intervening stack frames will be destroyed, however (which is
526 better than most compilers).</li>
528 <li>The LLVM C++ front-end follows the <a
529 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
530 This document, which is not Itanium specific, specifies a standard for name
531 mangling, class layout, v-table layout, RTTI formats, and other C++
532 representation issues. Because we use this API, code generated by the LLVM
533 compilers should be binary compatible with machine code generated by other
534 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
535 <i>However</i>, the exception handling mechanism used by LLVM is very
536 different from the model used in the Itanium ABI, so <b>exceptions will not
537 interact correctly</b>. </li>
543 <!-- ======================================================================= -->
544 <div class="doc_subsection">
545 <a name="x86-be">Known problems with the X86 back-end</a>
548 <div class="doc_text">
556 <!-- ======================================================================= -->
557 <div class="doc_subsection">
558 <a name="sparcv9-be">Known problems with the SparcV9 back-end</a>
561 <div class="doc_text">
564 <li><a href="http://llvm.cs.uiuc.edu/PR60">[sparcv9] SparcV9 backend miscompiles
565 several programs in the LLVM test suite</a></li>
570 <!-- ======================================================================= -->
571 <div class="doc_subsection">
572 <a name="c-be">Known problems with the C back-end</a>
575 <div class="doc_text">
579 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
580 Analysis rules. As such, special options may be necessary to compile the code
581 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
582 problem probably cannot be fixed.</li>
584 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
585 cannot include special floating point numbers like Not-A-Number or
588 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
589 supported</a>. This should not affect LLVM produced by the C or C++
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