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6 <title>LLVM 1.1 Release Notes</title>
10 <div class="doc_title">
11 LLVM 1.1 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="#portabilityprobs">Portability Problems</a> -->
22 <li><a href="#core">Known problems with the LLVM Core</a>
23 <li><a href="#c-fe">Known problems with the C Front-end</a>
24 <li><a href="#c++-fe">Known problems with the C++ Front-end</a>
25 <li><a href="#x86-be">Known problems with the X86 Back-end</a>
26 <li><a href="#sparc-be">Known problems with the Sparc Back-end</a>
27 <li><a href="#c-be">Known problems with the C back-end</a>
29 <li><a href="#additionalinfo">Additional Information</a></li>
32 <div class="doc_text">
33 <p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
36 <!-- *********************************************************************** -->
37 <div class="doc_section">
38 <a name="intro">Introduction</a>
40 <!-- *********************************************************************** -->
42 <div class="doc_text">
44 <p>This document contains the release notes for the LLVM compiler
45 infrastructure, release 1.1. Here we describe the status of LLVM, including any
46 known problems, and bug fixes from the previous release. The most up-to-date
47 version of this document can be found on the <a
48 href="http://llvm.cs.uiuc.edu/releases/1.1/">LLVM 1.1 web site</a>. If you are
49 not reading this on the LLVM web pages, you should probably go there, because
50 this document may be updated after the release.</p>
52 <p>For more information about LLVM, including information about potentially more
53 current releases, please check out the <a href="http://llvm.cs.uiuc.edu">main
54 web site</a>. If you have questions or comments, the <a
55 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
56 list</a> is a good place to send them.</p>
58 <p>Note that if you are reading this file from CVS, that this document applies
59 to the <i>next</i> release, not the previous one. To see the release notes for
60 the previous release, see the <a
61 href="http://llvm.cs.uiuc.edu/releases/">releases page</a>.</p>
65 <!-- *********************************************************************** -->
66 <div class="doc_section">
67 <a name="whatsnew">What's New?</a>
69 <!-- *********************************************************************** -->
71 <div class="doc_text">
73 <p>This is the second public release of the LLVM compiler infrastructure. This
74 release implements the following new features:</p>
78 href="http://mail.cs.uiuc.edu/pipermail/llvmdev/2003-November/000528.html">A new
79 LLVM profiler, similar to gprof</a> is available</li>
81 <li>LLVM and the C/C++ front-end now compile on Mac OSX! Mac OSX users can
82 now explore the LLVM optimizer with the C backend (note that LLVM requires GCC
86 href="http://mail.cs.uiuc.edu/pipermail/llvmdev/2003-November/000554.html">moved
87 into an 'llvm' C++ namespace</a>, for easier integration with third-party
88 code. Note that due to a bug in GDB 5.x, to debug namespacified LLVM code,
89 you will need to upgrade to GDB 6.</li>
92 <p>In this release, the following missing features were implemented:</p>
95 <li><a href="http://llvm.cs.uiuc.edu/PR88">The interpreter does not support
96 invoke or unwind</a></li>
98 <li><a href="http://llvm.cs.uiuc.edu/PR99">Interpreter does not support the
99 <tt>vaarg</tt> instruction</a></li>
101 <li><a href="http://llvm.cs.uiuc.edu/PR117">llvm-nm cannot read archive
106 <p>In this release, the following Quality of Implementation issues were
111 <li><a href="http://llvm.cs.uiuc.edu/PR29">C++ front-end is not generating
112 linkonce linkage type when it can</a></li>
114 <li><a href="http://llvm.cs.uiuc.edu/PR84">C front-end doesn't emit
115 getelementptr for address of array element</a></li>
117 <li><a href="http://llvm.cs.uiuc.edu/PR96">Bad path to the C/C++ frontend causes
118 build problems</a></li>
120 <li><a href="http://llvm.cs.uiuc.edu/PR114">LLVM header files should be -Wold-style-cast clean</a></li>
122 <li>The LLVM bytecode reader has been <a
123 href="http://llvm.cs.uiuc.edu/PR127">sped up a lot</a> (up to 4x in some
126 <li>Methods and functions in anonymous namespaces <a href="http://llvm.cs.uiuc.edu/PR85">now get internal linkage</a>.</li>
130 <p>In this release, the following bugs in the previous release were fixed:</p>
133 <li><a href="http://llvm.cs.uiuc.edu/PR57">[inliner] Inlining invoke with PHI in unwind target is broken</a></li>
134 <li><a href="http://llvm.cs.uiuc.edu/PR58">[linker] linkonce globals should link successfully to external globals</a></li>
135 <li><a href="http://llvm.cs.uiuc.edu/PR59">C++ frontend can crash when compiling virtual base classes</a></li>
136 <li><a href="http://llvm.cs.uiuc.edu/PR62">C backend fails on constant cast expr to ptr-to-anonymous struct</a></li>
137 <li><a href="http://llvm.cs.uiuc.edu/PR63">#ident is not recognized by C frontend</a></li>
138 <li><a href="http://llvm.cs.uiuc.edu/PR64">[constmerge] Constant merging pass merges constants with external linkage</a></li>
139 <li><a href="http://llvm.cs.uiuc.edu/PR65">C front-end miscompiles the builtin_expect intrinsic!</a></li>
140 <li><a href="http://llvm.cs.uiuc.edu/PR66">[scalarrepl] Scalar Replacement of aggregates is decimating structures it shouldn't be</a></li>
141 <li><a href="http://llvm.cs.uiuc.edu/PR67">1.0 precompiled libstdc++ does not include wchar_t support</a></li>
142 <li><a href="http://llvm.cs.uiuc.edu/PR68">llvmgcc asserts when compiling functions renamed with asm's</a></li>
143 <li><a href="http://llvm.cs.uiuc.edu/PR69">C frontend crashes on some programs with lots of types.</a></li>
144 <li><a href="http://llvm.cs.uiuc.edu/PR70">[instcombine] Resolving invoke inserts cast after terminator</a></li>
145 <li><a href="http://llvm.cs.uiuc.edu/PR71">llvm-as crashes when labels are used in phi nodes</a></li>
146 <li><a href="http://llvm.cs.uiuc.edu/PR72">[build problem] Callgraph.cpp not pulled in from libipa.a</a></li>
147 <li><a href="http://llvm.cs.uiuc.edu/PR77">Variables in scope of output setjmp
148 calls should be volatile</a>. Note that this does not effect correctness on
149 many platforms, such as X86.</li>
150 <li><a href="http://llvm.cs.uiuc.edu/PR79">llvm-gcc crashes compiling global union initializer</a></li>
151 <li><a href="http://llvm.cs.uiuc.edu/PR80">C front-end crash on empty structure</a></li>
152 <li><a href="http://llvm.cs.uiuc.edu/PR81">CFrontend crashes when compiling C99 compound expressions</a></li>
153 <li><a href="http://llvm.cs.uiuc.edu/PR83">[X86] Emission of global bool initializers broken</a></li>
154 <li><a href="http://llvm.cs.uiuc.edu/PR87">llvm-gcc infinite loops on "case MAXINT:"</a></li>
155 <li><a href="http://llvm.cs.uiuc.edu/PR89">[C++] Catch blocks make unparsable labels</a></li>
156 <li><a href="http://llvm.cs.uiuc.edu/PR90">[C++] Initializing array with constructable objects fail</a></li>
157 <li><a href="http://llvm.cs.uiuc.edu/PR91">[gccld] The -r (relinking) option does not work correctly</a></li>
158 <li><a href="http://llvm.cs.uiuc.edu/PR92">[bcreader] Cannot read shift constant expressions from bytecode file</a></li>
159 <li><a href="http://llvm.cs.uiuc.edu/PR93">[lowersetjmp] Lowersetjmp pass breaks dominance properties!</a></li>
160 <li><a href="http://llvm.cs.uiuc.edu/PR94">llvm-gcc tries to add bools</a></li>
161 <li><a href="http://llvm.cs.uiuc.edu/PR95">SymbolTable::getUniqueName is very inefficient</a></li>
162 <li><a href="http://llvm.cs.uiuc.edu/PR98">[buildscripts] Building into objdir with .o in it fails</a></li>
163 <li><a href="http://llvm.cs.uiuc.edu/PR101">[setjmp/longjmp] Linking C programs which use setjmp/longjmp sometimes fail with references to the C++ runtime library!</a></li>
164 <li><a href="http://llvm.cs.uiuc.edu/PR104">[c++] C++ Frontend lays out superclasses like anonymous bitfields!</a></li>
165 <li><a href="http://llvm.cs.uiuc.edu/PR107">AsmParser Misses Symbol Redefinition Error</a></li>
166 <li><a href="http://llvm.cs.uiuc.edu/PR108">gccld -Lfoo -lfoo fails to find ./foo/libfoo.a</a></li>
167 <li><a href="http://llvm.cs.uiuc.edu/PR110">[bcreader] Incorrect cast causes misread forward constant references</a></li>
168 <li><a href="http://llvm.cs.uiuc.edu/PR112">Casting a string constant to void crashes llvm-gcc</a></li>
169 <li><a href="http://llvm.cs.uiuc.edu/PR116">[adce] ADCE considers blocks without postdominators to be unreachable</a></li>
170 <li><a href="http://llvm.cs.uiuc.edu/PR54">C front-end miscompiles unsigned enums whose LLVM types are signed</a></li>
171 <li><a href="http://llvm.cs.uiuc.edu/PR123">[X86] div and rem constant exprs invalidate iterators!</a></li>
172 <li><a href="http://llvm.cs.uiuc.edu/PR125">[llvmg++] Enum types are incorrectly shrunk to smaller than 'int' size</a></li>
173 <li><a href="http://llvm.cs.uiuc.edu/PR128">[llvmg++] Cannot use pointer to member to initialize global</a></li>
174 <li><a href="http://llvm.cs.uiuc.edu/PR130">[vmcore] Symbol table doesn't rename colliding variables during type resolution</a></li>
175 <li><a href="http://llvm.cs.uiuc.edu/PR131">[llvm-gcc] ?: operator as lvalue not implemented</a></li>
176 <li><a href="http://llvm.cs.uiuc.edu/PR133">[C/C++] Bogus warning about taking the address of 'register' variable</a></li>
177 <li><a href="http://llvm.cs.uiuc.edu/PR97">bugpoint must not pass -R<directory> to Mach-O linker</a></li>
178 <li><a href="http://llvm.cs.uiuc.edu/PR113">crash assigning into an array in a struct which contains a bitfield</a>.</li>
179 <li><a href="http://llvm.cs.uiuc.edu/PR6">Oversized integer bitfields cause crash</a></li>
180 <li><a href="http://llvm.cs.uiuc.edu/PR140">gccld produces a runner script that includes command-line options to load the necessary shared objects</a></li>
181 <li><a href="http://llvm.cs.uiuc.edu/PR141">[llvm-gcc] Bitfields & large array don't mix well</a></li>
182 <li><a href="http://llvm.cs.uiuc.edu/PR132">[llvm-gcc] Complex division is not supported</a></li>
183 <li><a href="http://llvm.cs.uiuc.edu/PR143">[llvm-gcc] Illegal union field reference</a></li>
186 <p>At this time, LLVM is known to work properly with SPEC CPU 2000 (X86 only),
187 the Olden benchmarks, and the Ptrdist benchmarks among many other programs.
188 Note however that the Sparc and X86 backends do not currently support exception
189 throwing or long jumping (including 253.perlbmk in SPEC). For these programs,
190 you must use the C backend.</p>
194 <!-- *********************************************************************** -->
195 <div class="doc_section">
196 <a name="portability">Portability and Supported Platforms</a>
198 <!-- *********************************************************************** -->
200 <div class="doc_text">
202 <p>LLVM has been extensively tested on Intel and AMD machines running Red
203 Hat Linux, and Sun UltraSPARC workstations running Solaris 8. Additionally,
204 LLVM works on Mac OS/X 10.3 and above, but only with the C back-end (no native
205 backend for the PowerPC is available yet).
206 The core LLVM infrastructure uses "autoconf" for portability, so hopefully we
207 work on more platforms than that. However, it is likely that we
208 missed something, and that minor porting is required to get LLVM to work on
209 new platforms. We welcome portability patches and error messages.</p>
213 <!-- *********************************************************************** -->
214 <div class="doc_section">
215 <a name="knownproblems">Known Problems</a>
217 <!-- *********************************************************************** -->
219 <div class="doc_text">
221 <p>This section contains all known problems with the LLVM system, listed by
222 component. As new problems are discovered, they will be added to these
227 <!-- _______________________________________________________________________ -->
229 </ul><h4><a name="portability"><hr size=0>Portability Problems</h4><ul>
233 <!-- ======================================================================= -->
234 <div class="doc_subsection">
235 <a name="core">Known problems with the LLVM Core</a>
238 <div class="doc_text">
242 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
245 <li>The JIT does not use mutexes to protect its internal data structures. As
246 such, execution of a threaded program could cause these data structures to be
249 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
251 <li>Linking in static archive files (.a files) is very slow (there is no symbol
252 table in the archive).</li>
254 <li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
255 more than 256 elements</a>.</li>
261 <!-- ======================================================================= -->
262 <div class="doc_subsection">
263 <a name="c-fe">Known problems with the C front-end</a>
266 <!-- _______________________________________________________________________ -->
267 <div class="doc_subsubsection">
271 <div class="doc_text">
275 <li>C99 Variable sized arrays do not release stack memory when they go out of
276 scope. Thus, the following program may run out of stack space:
278 for (i = 0; i != 1000000; ++i) {
288 <!-- _______________________________________________________________________ -->
289 <div class="doc_subsubsection">
293 <div class="doc_text">
297 <li>Inline assembly is not yet supported.</li>
299 <li>"long double" is transformed by the front-end into "double". There is no
300 support for floating point data types of any size other than 32 and 64
303 <li>The following Unix system functionality has not been tested and may not
306 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
307 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
308 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
309 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
310 - These functions have not been tested.
313 <li>Although many GCC extensions are supported, some are not. In particular,
314 the following extensions are known to <b>not be</b> supported:
316 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
317 <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>
318 <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>
319 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
320 <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>
321 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands</li>
322 <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>
323 <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>
324 <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>
325 <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>
326 <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>
327 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
328 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
331 <p>The following GCC extensions are <b>partially</b> supported. An ignored
332 attribute means that the LLVM compiler ignores the presence of the attribute,
333 but the code should still work. An unsupported attribute is one which is
334 ignored by the LLVM compiler, which will cause a different interpretation of
338 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
339 Arrays whose length is computed at run time.<br>
340 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
342 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
344 Declaring that functions have no side effects, or that they can never
347 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
348 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
349 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
351 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
352 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
353 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
355 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
356 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
357 <tt>fastcall</tt>, all other target specific attributes</li>
359 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
360 Specifying attributes of variables.<br>
361 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
362 <tt>deprecated</tt>, <tt>transparent_union</tt>,
363 <tt>unused</tt>, <tt>weak</tt><br>
365 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
366 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
367 <tt>vector_size</tt>, <tt>dllimport</tt>,
368 <tt>dllexport</tt>, all target specific attributes.</li>
370 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.
371 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
372 <tt>deprecated</tt>, <tt>may_alias</tt>
374 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
375 all target specific attributes.</li>
377 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
378 Other built-in functions.<br>
379 We support all builtins which have a C language equivalent (e.g.,
380 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
381 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
382 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> (ignored).</li>
386 <p>The following extensions <b>are</b> known to be supported:</p>
389 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
390 <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>
391 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
392 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
393 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
394 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
395 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
396 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
397 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
398 <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>
399 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
400 <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>
401 <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>
402 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
403 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions or arrays as values.</li>
404 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
405 <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>
406 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
407 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
408 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
409 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
410 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
411 <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>
412 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
413 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
414 <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>
415 <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>
416 <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>
417 <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>
418 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
423 <p>If you run into GCC extensions which have not been included in any of these
424 lists, please let us know (also including whether or not they work).</p>
428 <!-- ======================================================================= -->
429 <div class="doc_subsection">
430 <a name="c++-fe">Known problems with the C++ front-end</a>
433 <div class="doc_text">
435 <p>For this release, the C++ front-end is considered to be fully functional but
436 of <b>beta</b> quality. It has been tested and works for a number of simple
437 programs that collectively exercise most of the language. Nevertheless, it has
438 not been in use as long as the C front-end. Please report any bugs or
443 <!-- _______________________________________________________________________ -->
444 <div class="doc_subsubsection">
448 <div class="doc_text">
451 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
457 <!-- _______________________________________________________________________ -->
458 <div class="doc_subsubsection">
462 <div class="doc_text">
466 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
467 parser is significantly more standards compliant (and picky) than prior GCC
468 versions. For more information, see the C++ section of the <a
469 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.<p>
471 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
472 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
473 function and in the <tt>setjmp</tt> receiver function may not be run.
474 Objects in intervening stack frames will be destroyed however (which is
475 better than most compilers).</li>
477 <li>The LLVM C++ front-end follows the <a
478 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
479 This document, which is not Itanium specific, specifies a standard for name
480 mangling, class layout, v-table layout, RTTI formats, and other C++
481 representation issues. Because we use this API, code generated by the LLVM
482 compilers should be binary compatible with machine code generated by other
483 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
484 <i>However</i>, the exception handling mechanism used by LLVM is very
485 different from the model used in the Itanium ABI, so <b>exceptions will not
486 interact correctly</b>. </li>
488 <li><a href="http://llvm.cs.uiuc.edu/PR11">Code for executing destructors when
489 unwinding is not shared</a> (this is a quality of implementation problem,
490 which does not effect functionality).</li>
496 <!-- ======================================================================= -->
497 <div class="doc_subsection">
498 <a name="x86-be">Known problems with the X86 back-end</a>
501 <div class="doc_text">
505 <li>The X86 code generator <a
506 href="http://llvm.cs.uiuc.edu/PR16">does not currently
507 support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
508 or calls the C <tt>longjmp</tt> function will abort.</li>
514 <!-- ======================================================================= -->
515 <div class="doc_subsection">
516 <a name="sparc-be">Known problems with the Sparc back-end</a>
519 <div class="doc_text">
523 <li>The Sparc code generator <a
524 href="http://llvm.cs.uiuc.edu/PR15">does not currently
525 support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
526 or calls the C <tt>longjmp</tt> function will abort.</li>
532 <!-- ======================================================================= -->
533 <div class="doc_subsection">
534 <a name="c-be">Known problems with the C back-end</a>
537 <div class="doc_text">
541 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
542 Analysis rules. As such, special options may be necessary to compile the code
543 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
544 problem probably cannot be fixed.</li>
546 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
547 cannot include special floating point numbers like Not-A-Number or
550 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
551 supported</a>. This should not affect LLVM produced by the C or C++
554 <li>The code produces by the C back-end has only been tested with the Sun CC,
555 GCC, and Intel compilers. It is possible that it will have to be adjusted to
556 support other C compilers.</li>
562 <!-- *********************************************************************** -->
563 <div class="doc_section">
564 <a name="additionalinfo">Additional Information</a>
566 <!-- *********************************************************************** -->
568 <div class="doc_text">
570 <p>A wide variety of additional information is available on the LLVM web page,
571 including mailing lists publications describing algorithms and components
572 implemented in LLVM. The web page also contains versions of the API
573 documentation which is up-to-date with the CVS version of the source code. You
574 can access versions of these documents specific to this release by going into
575 the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
577 <p>If you have any questions or comments about LLVM, please feel free to contact
578 us via the mailing lists.</p>
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