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6 <title>LLVM 1.2 Release Notes</title>
10 <div class="doc_title">
11 LLVM 1.2 Release Notes
15 <li><a href="#intro">Introduction</a></li>
16 <li><a href="#whatsnew">What's New?</a></li>
17 <li><a href="#portability">Portability and Supported Platforms</a></li>
18 <li><a href="#install-instructions">Installation Instructions</a></li>
19 <li><a href="#knownproblems">Known Problems</a>
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="#sparc-be">Known problems with the Sparc 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_text">
32 <p><b>Written by the <a href="http://llvm.cs.uiuc.edu">LLVM team</a></b><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 1.2. 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/1.2/">LLVM 1.2 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 third public release of the LLVM compiler infrastructure.
75 <p>At this time, LLVM is known to correctly compile and run all non-unwinding C
76 & C++ SPEC CPU2000 benchmarks, the Olden benchmarks, and the Ptrdist
77 benchmarks. It has also been used to compile <b>many</b> other programs. LLVM
78 now also works with a broad variety of C++ programs, though it has still
79 received much less testing than the C front-end.
83 The LLVM native code generators are very stable but do not currently support
84 unwinding (exception throwing or <tt>longjmp</tt>ing), which prevent them from
85 working with programs like the <tt>253.perlbmk</tt> in SPEC CPU2000. The C
86 backend and the rest of LLVM supports these programs, so you can
87 still use LLVM with them. Support for unwinding will be added in a future
92 <!--=========================================================================-->
93 <div class="doc_subsubsection">
94 This release implements the following new features:
103 <!--=========================================================================-->
104 <div class="doc_subsubsection">
105 In this release, the following missing features were implemented:
114 <!--=========================================================================-->
115 <div class="doc_subsubsection">
116 In this release, the following Quality of Implementation issues were fixed:
121 <li><a href="http://llvm.cs.uiuc.edu/PR135">JIT should lazily initialize global variables</a></li>
122 <li><a href="http://llvm.cs.uiuc.edu/PR192">[X86] X86 Backend never releases memory for machine code structures</a></li>
123 <li><a href="http://llvm.cs.uiuc.edu/PR196">[vmcore] OpaqueType objects memory leak</a></li>
124 <li><a href="http://llvm.cs.uiuc.edu/PR182">[llvmgcc] C front-end does not compile "extern inline" into linkonce</a></li>
125 <li><a href="http://llvm.cs.uiuc.edu/PR73">Bytecode format inconsistent</a></li>
126 <li><a href="http://llvm.cs.uiuc.edu/PR209">[loadvn/inline/scalarrepl] Slow optimizations with extremely large basic blocks</a></li>
129 <!--=========================================================================-->
130 <div class="doc_subsubsection">
131 In this release, the following build problems were fixed:
135 <li><a href="http://llvm.cs.uiuc.edu/PR210">[build] Makefiles break if C frontend target string has unexpected value</a></li>
136 <li><a href="http://llvm.cs.uiuc.edu/PR214">[build] hard-wired assumption that shared-library extension is ".so"</a></li>
137 <li><A href="http://llvm.cs.uiuc.edu/PR222">make tools-only doesn't make lib/Support</a></li>
140 <!--=========================================================================-->
141 <div class="doc_subsubsection">
142 In this release, the following Code Quality issues were fixed:
146 <li><a href="http://llvm.cs.uiuc.edu/PR187">[loopsimplify] Many pointless phi nodes are created</a></li>
147 <li>The X86 backend didn't generate <tt>fchs</tt> to negate floating point numbers</li>
151 <!--=========================================================================-->
152 <div class="doc_subsubsection">
153 In this release, the following bugs in the previous release were fixed:
156 <p>Bugs in the LLVM Core:</p>
159 <li><a href="http://llvm.cs.uiuc.edu/PR179">[licm] LICM promotes volatile memory
160 locations to registers</a></li>
161 <li><a href="http://llvm.cs.uiuc.edu/PR191">[licm] Memory read after free causes
162 infrequent crash</a></li>
163 <li><a href="http://llvm.cs.uiuc.edu/PR194">[indvars] Induction variable
164 canonicalization always makes 32-bit indvars</a></li>
165 <li><a href="http://llvm.cs.uiuc.edu/PR193">[constantmerge] Merging globals can
166 cause use of invalid pointers!</a></li>
167 <li><a href="http://llvm.cs.uiuc.edu/PR212">[bcreader] Bytecode reader misreads 'long -9223372036854775808'!</a></li>
168 <li><a href="http://llvm.cs.uiuc.edu/PR218">VMCore mishandles double -0.0</a></li>
169 <li><a href="http://llvm.cs.uiuc.edu/PR219">[X86] X86 backend code generates -0.0 as +0.0</a></li>
170 <li><a href="http://llvm.cs.uiuc.edu/PR223">[loopsimplify] Loopsimplify incorrectly updates dominator information</a></li>
174 <p>Bugs in the C/C++ front-end:</p>
177 <li><a href="http://llvm.cs.uiuc.edu/PR186">Need weak linkage on memory
178 management functions in libc runtime to allow them to be overriden</a></li>
179 <li><a href="http://llvm.cs.uiuc.edu/PR202">[llvm-gcc] asserts when an extern inline function is redefined</a></li>
180 <li><a href="http://llvm.cs.uiuc.edu/PR204">[llvmg++] Dynamically initialized constants cannot be marked 'constant'</a></li>
181 <li><a href="http://llvm.cs.uiuc.edu/PR216">[llvmgcc] floating-point unary minus is incorrect for +0.0</a></li>
182 <li><a href="http://llvm.cs.uiuc.edu/PR221">[llvm-gcc] miscompilation of 'X = Y = Z' with aggregate values</a></li>
187 <!-- *********************************************************************** -->
188 <div class="doc_section">
189 <a name="portability">Portability and Supported Platforms</a>
191 <!-- *********************************************************************** -->
193 <div class="doc_text">
195 <p>LLVM has been extensively tested on Intel and AMD machines running Red
196 Hat Linux and FreeBSD. It has also been tested on Sun UltraSPARC workstations running Solaris 8.
198 LLVM works on Mac OS X 10.3 and above, but only with the C backend or
199 interpreter (no native backend for the PowerPC is available yet).
200 The core LLVM infrastructure uses "autoconf" for portability, so hopefully we
201 work on more platforms than that. However, it is likely that we
202 missed something and that minor porting is required to get LLVM to work on
203 new platforms. We welcome portability patches and error messages.</p>
207 <!-- *********************************************************************** -->
208 <div class="doc_section">
209 <a name="knownproblems">Known Problems</a>
211 <!-- *********************************************************************** -->
213 <div class="doc_text">
215 <p>This section contains all known problems with the LLVM system, listed by
216 component. As new problems are discovered, they will be added to these
217 sections. If you run into a problem, please check the <a
218 href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
219 there isn't already one.</p>
223 <!-- _______________________________________________________________________ -->
225 </ul><h4><a name="portability"><hr size=0>Portability Problems</h4><ul>
229 <!-- ======================================================================= -->
230 <div class="doc_subsection">
231 <a name="core">Known problems with the LLVM Core</a>
234 <div class="doc_text">
238 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
241 <li>The JIT does not use mutexes to protect its internal data structures. As
242 such, execution of a threaded program could cause these data structures to be
245 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
247 <li>Linking in static archive files (.a files) is very slow (there is no symbol
248 table in the archive).</li>
250 <li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
251 more than 256 elements</a>.</li>
255 <a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=139">
256 does not link objects/archives in the order specified on the command line.
261 <a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=174">
262 Tail duplication does not update SSA form correctly.
266 <li><a href="http://llvm.cs.uiuc.edu/PR16">[lowerinvoke] The -lowerinvoke pass
267 does not insert calls to setjmp/longjmp</a>.</li>
273 <!-- ======================================================================= -->
274 <div class="doc_subsection">
275 <a name="c-fe">Known problems with the C front-end</a>
278 <!-- _______________________________________________________________________ -->
279 <div class="doc_subsubsection">Bugs</div>
281 <div class="doc_text">
283 <li>C99 Variable sized arrays do not release stack memory when they go out of
284 scope. Thus, the following program may run out of stack space:
286 for (i = 0; i != 1000000; ++i) {
293 Initialization of global union variables can only be done
294 <a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=162">with the largest
299 <a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=182">
300 Functions marked "extern inline" are not compiled into LLVM with linkonce
307 The memory management functions in the libc runtime
308 <a href="http://llvm.cs.uiuc.edu/PR186">need weak linkage so that they can be
315 <!-- _______________________________________________________________________ -->
316 <div class="doc_subsubsection">
320 <div class="doc_text">
324 <li>Inline assembly is not yet supported.</li>
326 <li>"long double" is transformed by the front-end into "double". There is no
327 support for floating point data types of any size other than 32 and 64
330 <li>The following Unix system functionality has not been tested and may not
333 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
334 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
335 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
336 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
337 - These functions have not been tested.
340 <li>Although many GCC extensions are supported, some are not. In particular,
341 the following extensions are known to <b>not be</b> supported:
343 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
344 <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>
345 <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>
346 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
347 <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>
348 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
349 <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>
350 <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>
351 <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>
352 <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>
353 <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>
354 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
355 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
358 <p>The following GCC extensions are <b>partially</b> supported. An ignored
359 attribute means that the LLVM compiler ignores the presence of the attribute,
360 but the code should still work. An unsupported attribute is one which is
361 ignored by the LLVM compiler and will cause a different interpretation of
365 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
366 Arrays whose length is computed at run time.<br>
367 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
369 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
371 Declaring that functions have no side effects or that they can never
374 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
375 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
376 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
378 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
379 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
380 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
382 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
383 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
384 <tt>fastcall</tt>, all other target specific attributes</li>
386 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
387 Specifying attributes of variables.<br>
388 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
389 <tt>deprecated</tt>, <tt>transparent_union</tt>,
390 <tt>unused</tt>, <tt>weak</tt><br>
392 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
393 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
394 <tt>vector_size</tt>, <tt>dllimport</tt>,
395 <tt>dllexport</tt>, all target specific attributes.</li>
397 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
398 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
399 <tt>deprecated</tt>, <tt>may_alias</tt><br>
401 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
402 all target specific attributes.</li>
404 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
405 Other built-in functions.<br>
406 We support all builtins which have a C language equivalent (e.g.,
407 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
408 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
409 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> (ignored).</li>
413 <p>The following extensions <b>are</b> known to be supported:</p>
416 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
417 <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>
418 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
419 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
420 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
421 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
422 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
423 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
424 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
425 <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>
426 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
427 <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>
428 <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>
429 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
430 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
431 or arrays as values.</li>
432 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
433 <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>
434 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
435 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
436 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
437 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
438 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
439 <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>
440 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
441 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
442 <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>
443 <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>
444 <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>
445 <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>
446 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
451 <p>If you run into GCC extensions which have not been included in any of these
452 lists, please let us know (also including whether or not they work).</p>
456 <!-- ======================================================================= -->
457 <div class="doc_subsection">
458 <a name="c++-fe">Known problems with the C++ front-end</a>
461 <div class="doc_text">
463 <p>For this release, the C++ front-end is considered to be fully functional but
464 has not been tested as thoroughly as the C front-end. It has been tested and
465 works for a number of non-trivial programs, but there may be lurking bugs.
466 Please report any bugs or problems.</p>
470 <!-- _______________________________________________________________________ -->
471 <div class="doc_subsubsection">
475 <div class="doc_text">
478 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
482 <a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=137">
483 Code is generated for empty classes.
489 <!-- _______________________________________________________________________ -->
490 <div class="doc_subsubsection">
494 <div class="doc_text">
498 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
499 parser is significantly more standards compliant (and picky) than prior GCC
500 versions. For more information, see the C++ section of the <a
501 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
503 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
504 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
505 function and in the <tt>setjmp</tt> receiver function may not be run.
506 Objects in intervening stack frames will be destroyed, however (which is
507 better than most compilers).</li>
509 <li>The LLVM C++ front-end follows the <a
510 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
511 This document, which is not Itanium specific, specifies a standard for name
512 mangling, class layout, v-table layout, RTTI formats, and other C++
513 representation issues. Because we use this API, code generated by the LLVM
514 compilers should be binary compatible with machine code generated by other
515 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
516 <i>However</i>, the exception handling mechanism used by LLVM is very
517 different from the model used in the Itanium ABI, so <b>exceptions will not
518 interact correctly</b>. </li>
524 <!-- ======================================================================= -->
525 <div class="doc_subsection">
526 <a name="x86-be">Known problems with the X86 back-end</a>
529 <div class="doc_text">
533 <li>The X86 code generator <a
534 href="http://llvm.cs.uiuc.edu/PR16">does not currently
535 support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
536 or calls the C <tt>longjmp</tt> function will abort.</li>
542 <!-- ======================================================================= -->
543 <div class="doc_subsection">
544 <a name="sparc-be">Known problems with the Sparc back-end</a>
547 <div class="doc_text">
551 <li>The Sparc code generator <a
552 href="http://llvm.cs.uiuc.edu/PR16">does not currently
553 support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
554 or calls the C <tt>longjmp</tt> function will abort.</li>
557 <a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=167">
558 The llc program can crash on legal code.
565 <!-- ======================================================================= -->
566 <div class="doc_subsection">
567 <a name="c-be">Known problems with the C back-end</a>
570 <div class="doc_text">
574 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
575 Analysis rules. As such, special options may be necessary to compile the code
576 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
577 problem probably cannot be fixed.</li>
579 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
580 cannot include special floating point numbers like Not-A-Number or
583 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
584 supported</a>. This should not affect LLVM produced by the C or C++
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