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6 <title>LLVM 1.3 Release Notes</title>
10 <div class="doc_title">LLVM 1.3 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="#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_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 1.3. 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/1.3/">LLVM 1.3 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 fourth public release of the LLVM compiler infrastructure. This
73 release primarily improves the <a href="#codequality">performance of the
74 code</a> produced by all aspects of the LLVM compiler and adds some <a
75 href="#newfeatures">new features</a>, though it does <a href="#bugfix">fix a few
78 <p> At this time, LLVM is known to correctly compile and run all C & C++
79 SPEC CPU2000 benchmarks, the Olden benchmarks, and the Ptrdist benchmarks. It
80 has also been used to compile <b>many</b> other programs. LLVM now also works
81 with a broad variety of C++ programs, though it has still received less testing
82 than the C front-end.</p>
86 <!--=========================================================================-->
87 <div class="doc_subsubsection">
88 <a name="newfeatures">This release implements the following new features:</a>
91 <div class="doc_text">
94 <li>The LLVM <a href="LangRef.html#i_select"><tt>select</tt></a> instruction is
95 now fully implemented and supported by all transformations, native code
96 generators, and the interpreter.</li>
97 <li>Bugpoint can now narrow down code-generation bugs to a loop nest, where
98 before it could only narrow them down to a function being miscompiled.</li>
99 <li><a href="http://llvm.cs.uiuc.edu/PR40">Bugpoint can now debug arbitrary
100 modes of llc</a> and lli, by passing them command line flags (e.g.,
101 <tt>-regalloc=linearscan</tt>, <tt>-enable-correct-eh-support</tt>, etc.) </li>
102 <li>The Control Flow Graph in the native code generators is no longer
103 constrained to be the same as the CFG for the LLVM input code.</li>
104 <li>The LLVM induction variable analysis routines have been rewritten.</li>
105 <li>LLVM now has new loop unrolling and loop unswitching passes.</li>
106 <li>The induction variable substitution pass performs linear function test
107 replacement and exit value replacement optimizations.</li>
108 <li>LLVM now has first-class support for <a href="GarbageCollection.html">Accurate
109 Garbage Collection</a>, enabling the use of aggressive copying and generational
111 <li>LLVM now includes an implementation of Andersen's interprocedural alias
112 analysis algorithm.</li>
113 <li>Bugpoint can <a href="http://llvm.cs.uiuc.edu/PR327">extract individual
114 basic blocks</a> to track down reduce miscompilation testcases.</li>
115 <li>LLVM and the C front-end now work under Win32 using the
116 <a href="http://www.cygwin.com">Cygwin</a> runtime libraries.
117 This includes the JIT compiler.</li>
118 <li>The LLVM code generator is now being <a
119 href="CodeGenerator.html">documented</a>.</li>
120 <li>There is a new tool, llvm-abcd, the Analysis of ByteCode Dumper (abcd).
121 This tool can compute basic statistics and bytecode density statistics on a
122 module or function basis and also dump out bytecode in a textual format that
123 is lower level than assembly (values are not resolved from slot numbers).
124 It should only be of interest to (a) those who are working to improve the
125 bytecode format and (b) those who really want to understand or document the
126 details of the bytecode format.</li>
127 <li>The <a href="BytecodeFormat.html">LLVM Bytecode file format</a> is now
128 being documented.</li>
134 <!--=========================================================================-->
135 <div class="doc_subsubsection">
136 In this release, the following missing features were implemented:
139 <div class="doc_text">
142 <li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
143 more than 256 elements</a></li>
144 <li><a href="http://llvm.cs.uiuc.edu/PR38">[bugpoint] External functions used in
145 non-instruction entities, such as global constant initializer</a></li>
146 <li><a href="http://llvm.cs.uiuc.edu/PR178">Stacker does not handle targets
147 with 64-bit pointers.</a></li>
148 <li><a href="http://llvm.cs.uiuc.edu/PR290">Bugpoint doesn't support
149 uses of external fns by immediate constant exprs</a></li>
154 <!--=========================================================================-->
155 <div class="doc_subsubsection">
156 <a name="qualityofimp">In this release, the following Quality of Implementation
157 issues were fixed:</a>
160 <div class="doc_text">
163 <li><a href="http://llvm.cs.uiuc.edu/PR305">LLVM tools will happily spew
164 bytecode onto your terminal</a></li>
165 <li><a href="http://llvm.cs.uiuc.edu/PR329">[llvmgcc] type names are not emitted
166 for structure typedefs</a></li>
167 <li>All documentation is now conformant to the HTML 4.01 (Strict) level.</li>
168 <li>The spurious "WARNING: Found global types that are not compatible" warning
169 produced when linking C++ programs has been fixed.</li>
174 <!--=========================================================================-->
175 <div class="doc_subsubsection">
176 In this release, the following build problems were fixed:
179 <div class="doc_text">
181 <li><a href="http://llvm.cs.uiuc.edu/PR301">Minor configure bugs with
182 -disable/enable-povray and -disable-spec</a></li>
183 <li><a href="http://llvm.cs.uiuc.edu/PR289">shell scripts output by gccld don't
184 work if you change PATH</a></li>
185 <li><a href="http://llvm.cs.uiuc.edu/PR364">[llvmgcc] llvmgcc does not compile
186 with gcc 3.4</a></li>
190 <!--=========================================================================-->
191 <div class="doc_subsubsection">
192 <a name="codequality">This release includes the following Code Quality
196 <div class="doc_text">
198 <li>Fixed: <a href="http://llvm.cs.uiuc.edu/PR309">[vmcore] Code quality problem
199 due to long operand of getelementptr</a></li>
201 <li>The X86 backend now generates substantially better code for 64-bit integer
202 and floating point operations.</li>
204 <li>The -inline pass no longer inlines mutually recursive functions until it
205 hits the inlining threshold.</li>
207 <li>The -inline pass no longer misses obvious inlining opportunities just
208 because the callee eventually calls into an external function.</li>
210 <li>The -simplifycfg pass can now "if convert" simple statements into the new
211 <tt>select</tt> instruction.</li>
213 <li>The -loopsimplify pass can now break <a
214 href="http://llvm.cs.uiuc.edu/PR35">natural loops with multiple backedges</a>
215 into multiple nested loops. This enables a variety of subsequent
218 <li>The -adce pass can now eliminate calls to functions that do not not write to
221 <li>The link-time optimizer now runs the -prune-eh pass (to remove unused
222 exception handlers).</li>
224 <li>The -simplifycfg pass can now eliminate simple correlated branches (such as
225 "<tt>if (A < B && A < B)</tt>", and can turn short-circuiting
226 operators into the strict versions when useful (such as "<tt>if (A < B || A
227 > C)</tt>" into "<tt>if (A < B | A > C)</tt>"</li>
229 <li>LLVM now has infrastructure for (simple and sparse conditional) constant
230 propagation of function calls. It currently supports a few math library
231 functions like sqrt/sin/cos/etc.</li>
233 <li>The C backend now emits <a href="http://llvm.cs.uiuc.edu/PR334">Syntactic
234 loops</a> in the code to help C compilers whose optimizers do not recognize
235 loops formed from gotos (like GCC).</li>
237 <li>Fixed: <a href="http://llvm.cs.uiuc.edu/PR368">[sparcv9] null
238 often spilled to constant pool</a>.</li>
242 <!--=========================================================================-->
243 <div class="doc_subsubsection">
244 <a name="bugfix">In this release, the following bugs in the previous release
248 <div class="doc_text">
250 <p>Bugs in the LLVM Core:</p>
253 <li><a href="http://llvm.cs.uiuc.edu/PR330">[vmcore] Linker causes erroneous
255 <li><a href="http://llvm.cs.uiuc.edu/PR306">[loopsimplify] Loop simplify
256 incorrectly updates dominator information</a></li>
257 <li><a href="http://llvm.cs.uiuc.edu/PR310">[tailduplicate] DemoteRegToStack
258 breaks SSA form</a></li>
259 <li><a href="http://llvm.cs.uiuc.edu/PR313">[X86] JIT miscompiles unsigned short
260 to floating point cast</a></li>
261 <li><a href="http://llvm.cs.uiuc.edu/PR332">[adce] Crash handling unreachable
262 code that unwinds</a></li>
263 <li><a href="http://llvm.cs.uiuc.edu/PR333">[sparc] LLC can't emit 2 functions
264 of the same name, both having constant pools</a></li>
265 <li><a href="http://llvm.cs.uiuc.edu/PR337">[livevar] Live variables missed
266 physical register use of aliased definition</a></li>
267 <li><a href="http://llvm.cs.uiuc.edu/PR340">Verifier misses malformed switch instruction</a></li>
268 <li><a href="http://llvm.cs.uiuc.edu/PR315">[jit] abort, don't warn, when missing external functions encountered</a></li>
271 <p>Bugs in the C/C++ front-end:</p>
274 <li><a href="http://llvm.cs.uiuc.edu/PR326">[llvmgcc] Crash on use of undeclared
276 <li><a href="http://llvm.cs.uiuc.edu/PR298">[llvmgcc] Variable length array
277 indexing miscompiled</a></li>
278 <li><a href="http://llvm.cs.uiuc.edu/PR355">[llvmgcc] Errors handling function prototypes that take opaque structs by-value</a></li>
282 <!-- *********************************************************************** -->
283 <div class="doc_section">
284 <a name="portability">Portability and Supported Platforms</a>
286 <!-- *********************************************************************** -->
288 <div class="doc_text">
290 <p>LLVM is known to work in the following platforms:</p>
293 <li>Intel and AMD machines running Red Hat Linux and FreeBSD (and probably
294 other unix-like systems).</li>
295 <li>Sun UltraSPARC workstations running Solaris 8.</li>
296 <li>PowerPC-based Mac OS X boxes, running 10.3 and above (C backend and
297 interpreter only, no native codegen is available yet).</li>
298 <li>Intel and AMD machines running on Win32 with the Cygwin libraries.</li>
302 <p>The core LLVM infrastructure uses
303 <a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
304 to the machine and operating system on which it is built. However, minor
305 porting may be required to get LLVM to work on new platforms. We welcome your
306 portability patches and reports of successful builds or error messages.</p>
308 <p>Note that the LLVM build system does not currently support directories with
309 spaces on them when running on Win32/cygwin. We strongly recommend running
310 LLVM and the C frontend out of a top-level directory without spaces (e.g.,
311 <tt>/cygdrive/c/llvm</tt>). Also, make sure to install <b>all</b> of the
312 cygwin packages. By default, many important tools are not installed that
313 are needed by the LLVM build process or test suite (e.g., /bin/time).</p>
317 <!--=========================================================================-->
318 <div class="doc_subsection">
319 In this release, the following portability problems were fixed:
322 <div class="doc_text">
325 <li><a href="http://llvm.cs.uiuc.edu/PR304">warnings compiling Stacker compiler
327 <li><a href="http://llvm.cs.uiuc.edu/PR308">Archive file reader doesn't
328 understand abbreviated names in headers</a></li>
333 <!-- *********************************************************************** -->
334 <div class="doc_section">
335 <a name="knownproblems">Known Problems</a>
337 <!-- *********************************************************************** -->
339 <div class="doc_text">
341 <p>This section contains all known problems with the LLVM system, listed by
342 component. As new problems are discovered, they will be added to these
343 sections. If you run into a problem, please check the <a
344 href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
345 there isn't already one.</p>
349 <!-- ======================================================================= -->
350 <div class="doc_subsection">
351 <a name="experimental">Experimental features included with this release</a>
354 <div class="doc_text">
356 <p>The following components of this LLVM release are either untested, known to
357 be broken or unreliable, or are in early development. These components should
358 not be relied on, and bugs should not be filed against them, but they may be
359 useful to some people. In particular, if you would like to work on one of these
360 components, please contact us on the llvmdev list.</p>
363 <li>The following passes are incomplete or buggy: <tt>-pgmdep, -memdep,
364 -ipmodref, -sortstructs, -swapstructs, -cee</tt></li>
366 <li>The <tt>-pre</tt> pass is incomplete (there are cases it doesn't handle that
367 it should) and not thoroughly tested.</li>
368 <li>The <tt>llvm-ar</tt> tool is incomplete and probably buggy.</li>
369 <li>The <tt>llvm-db</tt> tool is in a very early stage of development.</li>
374 <!-- ======================================================================= -->
375 <div class="doc_subsection">
376 <a name="core">Known problems with the LLVM Core</a>
379 <div class="doc_text">
383 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
386 <li>The JIT does not use mutexes to protect its internal data structures. As
387 such, execution of a threaded program could cause these data structures to be
390 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
392 <li>Linking in static archive files (.a files) is very slow (there is no symbol
393 table in the archive).</li>
395 <li>The gccld program <a href="http://llvm.cs.uiuc.edu/PR139">does not link
396 objects/archives in the order specified on the command line.</a></li>
398 <li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not mark
399 values live across a setjmp as volatile</a>. This missing feature only affects
400 targets whose setjmp/longjmp libraries do not save and restore the entire
405 <!-- ======================================================================= -->
406 <div class="doc_subsection">
407 <a name="c-fe">Known problems with the C front-end</a>
410 <!-- _______________________________________________________________________ -->
411 <div class="doc_subsubsection">Bugs</div>
413 <div class="doc_text">
415 <li>C99 Variable sized arrays do not release stack memory when they go out of
416 scope. Thus, the following program may run out of stack space:
418 for (i = 0; i != 1000000; ++i) {
424 <li>Initialization of global union variables can only be done <a
425 href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=162">with the largest union
428 <li><a href="http://llvm.cs.uiuc.edu/PR244">[llvm-gcc] Error when an implicitly
429 external function is re-declared as static</a></li>
434 <!-- _______________________________________________________________________ -->
435 <div class="doc_subsubsection">
439 <div class="doc_text">
443 <li>Inline assembly is not yet supported.</li>
445 <li>"long double" is transformed by the front-end into "double". There is no
446 support for floating point data types of any size other than 32 and 64
449 <li>The following Unix system functionality has not been tested and may not
452 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
453 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
454 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
455 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
456 - These functions have not been tested.
459 <li>Although many GCC extensions are supported, some are not. In particular,
460 the following extensions are known to <b>not be</b> supported:
462 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
463 <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>
464 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
465 <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>
466 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
467 <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>
468 <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>
469 <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>
470 <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>
471 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
472 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
475 <p>The following GCC extensions are <b>partially</b> supported. An ignored
476 attribute means that the LLVM compiler ignores the presence of the attribute,
477 but the code should still work. An unsupported attribute is one which is
478 ignored by the LLVM compiler and will cause a different interpretation of
482 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
483 Arrays whose length is computed at run time.<br>
484 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
486 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
488 Declaring that functions have no side effects or that they can never
491 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
492 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
493 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
495 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
496 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
497 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
499 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
500 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
501 <tt>fastcall</tt>, all other target specific attributes</li>
503 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
504 Specifying attributes of variables.<br>
505 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
506 <tt>deprecated</tt>, <tt>transparent_union</tt>,
507 <tt>unused</tt>, <tt>weak</tt><br>
509 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
510 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
511 <tt>vector_size</tt>, <tt>dllimport</tt>,
512 <tt>dllexport</tt>, all target specific attributes.</li>
514 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
515 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
516 <tt>deprecated</tt>, <tt>may_alias</tt><br>
518 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
519 all target specific attributes.</li>
521 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
522 Other built-in functions.<br>
523 We support all builtins which have a C language equivalent (e.g.,
524 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
525 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
526 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> (ignored).</li>
530 <p>The following extensions <b>are</b> known to be supported:</p>
533 <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>
534 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
535 <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>
536 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
537 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
538 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
539 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
540 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
541 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
542 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
543 <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>
544 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
545 <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>
546 <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>
547 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
548 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
549 or arrays as values.</li>
550 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
551 <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>
552 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
553 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
554 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
555 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
556 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
557 <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>
558 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
559 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
560 <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>
561 <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>
562 <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>
563 <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>
564 <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>
565 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
570 <p>If you run into GCC extensions which have not been included in any of these
571 lists, please let us know (also including whether or not they work).</p>
575 <!-- ======================================================================= -->
576 <div class="doc_subsection">
577 <a name="c++-fe">Known problems with the C++ front-end</a>
580 <div class="doc_text">
582 <p>For this release, the C++ front-end is considered to be fully functional but
583 has not been tested as thoroughly as the C front-end. It has been tested and
584 works for a number of non-trivial programs, but there may be lurking bugs.
585 Please report any bugs or problems.</p>
589 <!-- _______________________________________________________________________ -->
590 <div class="doc_subsubsection">Bugs</div>
592 <div class="doc_text">
595 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
600 <!-- _______________________________________________________________________ -->
601 <div class="doc_subsubsection">
605 <div class="doc_text">
609 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
610 parser is significantly more standards compliant (and picky) than prior GCC
611 versions. For more information, see the C++ section of the <a
612 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
614 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
615 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
616 function and in the <tt>setjmp</tt> receiver function may not be run.
617 Objects in intervening stack frames will be destroyed, however (which is
618 better than most compilers).</li>
620 <li>The LLVM C++ front-end follows the <a
621 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
622 This document, which is not Itanium specific, specifies a standard for name
623 mangling, class layout, v-table layout, RTTI formats, and other C++
624 representation issues. Because we use this API, code generated by the LLVM
625 compilers should be binary compatible with machine code generated by other
626 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
627 <i>However</i>, the exception handling mechanism used by LLVM is very
628 different from the model used in the Itanium ABI, so <b>exceptions will not
629 interact correctly</b>. </li>
635 <!-- ======================================================================= -->
636 <div class="doc_subsection">
637 <a name="x86-be">Known problems with the X86 back-end</a>
640 <div class="doc_text">
648 <!-- ======================================================================= -->
649 <div class="doc_subsection">
650 <a name="sparc-be">Known problems with the Sparc back-end</a>
653 <div class="doc_text">
656 <li>There are several programs in the LLVM testsuite that the Sparc code generator is known to miscompile.</li>
661 <!-- ======================================================================= -->
662 <div class="doc_subsection">
663 <a name="c-be">Known problems with the C back-end</a>
666 <div class="doc_text">
670 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
671 Analysis rules. As such, special options may be necessary to compile the code
672 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
673 problem probably cannot be fixed.</li>
675 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
676 cannot include special floating point numbers like Not-A-Number or
679 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
680 supported</a>. This should not affect LLVM produced by the C or C++
687 <!-- *********************************************************************** -->
688 <div class="doc_section">
689 <a name="additionalinfo">Additional Information</a>
691 <!-- *********************************************************************** -->
693 <div class="doc_text">
695 <p>A wide variety of additional information is available on the LLVM web page,
696 including mailing lists and publications describing algorithms and components
697 implemented in LLVM. The web page also contains versions of the API
698 documentation which is up-to-date with the CVS version of the source code. You
699 can access versions of these documents specific to this release by going into
700 the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
702 <p>If you have any questions or comments about LLVM, please feel free to contact
703 us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
708 <!-- *********************************************************************** -->
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