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5 <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
6 <tr><td> <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>LLVM 1.0 Release Notes</b></font></td>
10 <li><a href="#intro">Introduction</a>
11 <li><a href="#whatsnew">What's New?</a>
12 <li><a href="#portability">Portability and Supported Platforms</a>
13 <li><a href="#install-instructions">Installation Instructions</a>
14 <li><a href="#knownproblems">Known Problems</a>
16 <!-- <li><a href="#portabilityprobs">Portability Problems</a> -->
17 <li><a href="#core">Known problems with the LLVM Core</a>
18 <li><a href="#c-fe">Known problems with the C Front-end</a>
19 <li><a href="#c++-fe">Known problems with the C++ Front-end</a>
20 <li><a href="#x86-be">Known problems with the X86 Back-end</a>
21 <li><a href="#sparc-be">Known problems with the Sparc Back-end</a>
22 <li><a href="#c-be">Known problems with the C back-end</a>
24 <li><a href="#additionalinfo">Additional Information</a>
27 <p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
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32 <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
33 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
34 <a name="intro">Introduction
35 </b></font></td></tr></table><ul>
36 <!-- *********************************************************************** -->
38 This document contains the release notes for the LLVM compiler infrastructure,
39 release 1.0. Here we describe how to install LLVM, as well as any known
40 problems. The most up-to-date version of this document can be found on the <a
41 href="http://llvm.cs.uiuc.edu/releases/1.0/">LLVM 1.0 web site</a>. If you are
42 not reading this on the LLVM web pages, you should probably go there, because
43 this document may be updated after the release.<p>
45 For more information about LLVM, including information about potentially more
46 current releases, please check out the <a href="http://llvm.cs.uiuc.edu">main
47 web site</a>. If you have questions or comments, the <a
48 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
49 list</a> is a good place to send them.<p>
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53 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
54 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
55 <a name="whatsnew">What's New?
56 </b></font></td></tr></table><ul>
57 <!-- *********************************************************************** -->
59 This is the first public release of the LLVM compiler infrastructure. As such,
60 it is all new! In particular, we are providing a stable C compiler, beta C++
61 compiler, a C back-end, stable X86 and Sparc V9 static and JIT code generators,
62 as well as a large suite of scalar and interprocedural optimizations.<p>
64 The default optimizer sequence used by the C/C++ front-ends is:<p>
67 <li>Interprocedural dead code elimination (-globaldce)
68 <li>Exception handling pruning (-prune-eh)
69 <li>Function inlining (-inline)
70 <li>Instruction combining (-instcombine)
71 <li>Cast elimination (-raise)
72 <li>Tail duplication (-tailduplicate)
73 <li>CFG simplification (-simplifycfg)
74 <li>Scalar replacement of aggregates (-scalarrepl)
75 <li>Tail call elimination (-tailcallelim)
76 <li>Instruction combining (-instcombine)
77 <li>Reassociation (-reassociate)
78 <li>Instruction combining (-instcombine)
79 <li>CFG simplification (-simplifycfg)
80 <li>Loop canonicalization (-loopsimplify)
81 <li>Loop invariant code motion, with scalar promotion (-licm)
82 <li>Global common subexpression elimination, with load elimination (-gcse)
83 <li>Sparse conditional constant propagation (-sccp)
84 <li>Instruction combining (-instcombine)
85 <li>Induction variable canonicalization (-indvars)
86 <li>Aggressive dead code elimination (-adce)
87 <li>CFG simplication (-simplifycfg)
88 <li>Dead type elimination (-deadtypeelim)
89 <li>Global constant merging (-constmerge)
92 At link-time, the following optimizations are run:<p>
95 <li>Global constant merging (-constmerge)
96 <li>[optional] Internalization [which marks most functions and global variables static] (-internalize)
97 <li>Interprocedural dead argument elimination (-deadargelim)
98 <li>Instruction combining (-instcombine)
99 <li>CFG simplification (-simplifycfg)
100 <li>Interprocedural dead code elimination (-globaldce)
104 TODO: Works on: SPEC CPU 2000<p>
105 TODO: Works on: Olden/Ptrdist benchmarks<p>
107 The What's New section should give a bulletted list of what is
108 included, perhaps a couple of lists (Stable, Beta).<p>
110 It would be useful to give a pointer to a list of the available passes (at least
111 for the standard compiler techniques).<p>
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115 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
116 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
117 <a name="portability">Portability and Supported Platforms
118 </b></font></td></tr></table><ul>
119 <!-- *********************************************************************** -->
121 LLVM has only been extensively tested on ia32-linux and sparc-solaris machines.
122 The core LLVM infrastructure uses "autoconf" for portability, so hopefully we
123 work on more platforms than that. However, it is extremely likely that we
124 missed something. We welcome portability patches and error messages.<p>
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128 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
129 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
130 <a name="install-instructions">Installation Instructions
131 </b></font></td></tr></table><ul>
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138 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
139 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
140 <a name="knownproblems">Known Problems
141 </b></font></td></tr></table><ul>
142 <!-- *********************************************************************** -->
144 This section contains all known problems with the LLVM system, listed by
145 component. As new problems are discovered, they will be added to these
149 <!-- _______________________________________________________________________ -->
151 </ul><h4><a name="portability"><hr size=0>Portability Problems</h4><ul>
155 <!-- _______________________________________________________________________ -->
156 </ul><h4><a name="core"><hr size=0>Known problems with the LLVM Core</h4><ul>
158 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not work.<p>
160 <li>The JIT does not use mutexes to protect its internal data structures. As
161 such, execution of a threaded program could cause these data structures to
164 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.<p>
166 <li>Linking in static archive files (.a files) is very slow.
168 <!-- _______________________________________________________________________ -->
169 </ul><h4><a name="c-fe"><hr size=0>Known problems with the C front-end</h4><ul>
171 <li>Inline assembly is not yet supported.<p>
173 <li>"long double" is transformed by the front-end into "double". There is no
174 support for floating point data types of any size other than 32 and 64 bits.
176 <li>C99 Variable sized arrays do not release stack memory when they go out of
177 scope. Thus, the following program may run out of stack space:
179 for (i = 0; i != 1000000; ++i) {
185 <li>The following Unix system functionality has not been tested and may not work:
187 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
188 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions.
189 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
190 - These functions have not been tested.
194 <a href="http://llvm.cs.uiuc.edu/PR6">Oversized integer bitfields cause crash</a>.<br>
195 <a href="http://llvm.cs.uiuc.edu/PR9">LLVM needs explicit support for weak variables</a>.<br>
198 <li>Although many GCC extensions are supported, some are not. In particular,
199 the following extensions are known to <b>not be</b> supported:
201 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.
202 <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.
203 <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.
204 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.
205 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.
206 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands
207 <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.
208 <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.
209 <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.
210 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.
211 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.
212 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.
213 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.
216 The following GCC extensions are <b>partially</b> supported. An ignored
217 attribute means that the LLVM compiler ignores the presence of the attribute,
218 but the code should still work. An unsupported attribute is one which is
219 ignored by the LLVM compiler, which will cause a different interpretation of
223 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
224 Arrays whose length is computed at run time.<br>
225 Supported, but allocated stack space is not freed until the function returns (noted above).
227 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
228 Declaring that functions have no side effects, or that they can never return.<br>
229 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>, <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>, <tt>deprecated</tt>,
230 <tt>warn_unused_result</tt>, <tt>weak</tt><br>
231 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>, <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>, <tt>malloc</tt>
232 <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
233 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>, <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
234 <tt>fastcall</tt>, all other target specific attributes
236 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
237 Specifying attributes of variables.<br>
238 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
239 <tt>deprecated</tt>, <tt>transparent_union</tt>,
240 <tt>unused</tt>, <tt>weak</tt><br>
241 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
242 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
243 <tt>vector_size</tt>, <tt>dllimport</tt>,
244 <tt>dllexport</tt>, all target specific attributes.<br>
246 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.
247 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
248 <tt>deprecated</tt>, <tt>may_alias</tt>
249 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>
250 all target specific attributes.<br>
251 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
252 Other built-in functions.<br>
253 We support all builtins which have a C language equivalent (e.g.,
254 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
255 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
256 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> (ignored).
260 The following extensions <b>are</b> known to be supported:
262 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.
263 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.
264 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.
265 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.
266 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.
267 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.
268 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.
269 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.
270 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.
271 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.
272 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.
273 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.
274 <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.
275 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.
276 <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.
277 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.
279 <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.
280 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.
281 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.
283 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.
284 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.
285 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.
286 <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>.
287 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.
288 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).
289 <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.
290 <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.
291 <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.
292 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.
293 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.
296 If you run into GCC extensions which have not been included in any of these
297 lists, please let us know (also including whether or not they work).
300 <!-- _______________________________________________________________________ -->
301 </ul><h4><a name="c++-fe"><hr size=0>Known problems with the C++ front-end</h4><ul>
303 For this release, the C++ front-end is considered to be of <b>beta</b> quality.
304 It works for a large number of simple programs, but has not been extensively
305 tested. We welcome bug reports though!<p>
307 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
310 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
311 parser is significantly more standards compliant (and picky) than prior GCC
312 versions. For more information, see the C++ section of the <a
313 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.<p>
315 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
316 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
317 function and in the <tt>setjmp</tt> receiver function may not be run.
318 Objects in intervening stack frames will be destroyed however (which is
319 better than most compilers).<p>
321 <li>The LLVM C++ front-end follows the <a
322 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
323 This document, which is not Itanium specific, specifies a standard for name
324 mangling, class layout, v-table layout, RTTI formats, and other C++
325 representation issues. Because we use this API, code generated by the LLVM
326 compilers should be binary compatible with machine code generated by other
327 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
328 <i>However</i>, the exception handling mechanism used by LLVM is very
329 different from the model used in the Itanium ABI, so <b>exceptions will not
330 interact correctly</b> .
332 <li><a href="http://llvm.cs.uiuc.edu/PR11">Code for executing
333 destructors when unwinding is not shared</a>.
336 <!-- _______________________________________________________________________ -->
337 </ul><h4><a name="x86-be"><hr size=0>Known problems with the X86 back-end</h4><ul>
339 <li>The X86 code generator <a
340 href="http://llvm.cs.uiuc.edu/PR16">does not currently
341 support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
342 or calls the C <tt>longjmp</tt> function will abort.<p>
344 <li><a href="http://llvm.cs.uiuc.edu/PR4">Some executables
345 produced by LLC seem to intermittently crash (extremely infrequently)</a>. The
346 cause of the problem has not been diagnosed, and does not affect the JIT.<p>
349 <!-- _______________________________________________________________________ -->
350 </ul><h4><a name="sparc-be"><hr size=0>Known problems with the Sparc back-end</h4><ul>
352 <li>The Sparc code generator <a
353 href="http://llvm.cs.uiuc.edu/PR15">does not currently
354 support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
355 or calls the C <tt>longjmp</tt> function will abort.<p>
358 <!-- _______________________________________________________________________ -->
359 </ul><h4><a name="c-be"><hr size=0>Known problems with the C back-end</h4><ul>
361 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
362 Analysis rules. As such, special options may be necessary to compile the code
363 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
364 problem probably cannot be fixed.<p>
366 <li>Initializers for global variables that include floating point numbers may
367 not be initialized with exactly the right floating point number, if the number
368 is not accurately representable in decimal. This prevents the Olden "power"
369 benchmark from producing exactly the right results with the C back-end.<p>
371 <li>The code produces by the C back-end has only been tested with the Sun CC and
372 GCC compilers. It is possible that it will have to be adjusted to support other
377 <!-- *********************************************************************** -->
378 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
379 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
380 <a name="additionalinfo">Additional Information
381 </b></font></td></tr></table><ul>
382 <!-- *********************************************************************** -->
384 A wide variety of additional information is available on the LLVM web page,
385 including mailing lists publications describing algorithms and components
386 implemented in LLVM. The web page also contains versions of the API
387 documentation which is up-to-date with the CVS version of the source code. You
388 can access versions of these documents specific to this release by going into
389 the "<tt>llvm/www/doc/</tt>" directory in the LLVM tree.<p>
391 If you have any questions or comments about LLVM, please feel free to contact us
392 via the mailing lists.<p>
395 <!-- *********************************************************************** -->
397 <!-- *********************************************************************** -->
401 Maintained By: <a href="http://llvm.cs.uiuc.edu/">The LLVM Team</a><br>
402 <!-- Created: Wed Oct 1 17:38:54 CDT 2003 -->
404 Last modified: Sun Oct 12 16:51:06 CDT 2003