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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>The <a href="BytecodeFormat.html">LLVM Bytecode file format</a> is now
110 <li>LLVM now has first-class support for <a href="GarbageCollection.html">Accurate
111 Garbage Collection</a>, enabling the use of aggressive copying and generational
113 <li>LLVM now includes an implementation of Andersen's interprocedural alias
114 analysis algorithm.</li>
120 <!--=========================================================================-->
121 <div class="doc_subsubsection">
122 In this release, the following missing features were implemented:
125 <div class="doc_text">
128 <li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
129 more than 256 elements</a></li>
130 <li><a href="http://llvm.cs.uiuc.edu/PR38">[bugpoint] External functions used in
131 non-instruction entities, such as global constant initializer</a></li>
132 <li><a href="http://llvm.cs.uiuc.edu/PR178">Stacker does not handle targets
133 with 64-bit pointers.</a></li>
134 <li><a href="http://llvm.cs.uiuc.edu/PR290">Bugpoint doesn't support
135 uses of external fns by immediate constant exprs</a></li>
140 <!--=========================================================================-->
141 <div class="doc_subsubsection">
142 <a name="qualityofimp">In this release, the following Quality of Implementation
143 issues were fixed:</a>
146 <div class="doc_text">
149 <li><a href="http://llvm.cs.uiuc.edu/PR305">LLVM tools will happily spew
150 bytecode onto your terminal</a></li>
151 <li><a href="http://llvm.cs.uiuc.edu/PR329">[llvmgcc] type names are not emitted
152 for structure typedefs</a></li>
153 <li>All documentation is now conformant to the HTML 4.01 (Strict) level.</li>
158 <!--=========================================================================-->
159 <div class="doc_subsubsection">
160 In this release, the following build problems were fixed:
163 <div class="doc_text">
165 <li><a href="http://llvm.cs.uiuc.edu/PR301">Minor configure bugs with
166 -disable/enable-povray and -disable-spec</a></li>
167 <li><a href="http://llvm.cs.uiuc.edu/PR289">shell scripts output by gccld don't
168 work if you change PATH</a></li>
172 <!--=========================================================================-->
173 <div class="doc_subsubsection">
174 <a name="codequality">This release includes the following Code Quality
178 <div class="doc_text">
180 <li>Fixed: <a href="http://llvm.cs.uiuc.edu/PR309">[vmcore] Code quality problem
181 due to long operand of getelementptr</a></li>
183 <li>The X86 backend now generates substantially better code for 64-bit integer
184 and floating point operations.</li>
186 <li>The -inline pass no longer inlines mutually recursive functions until it
187 hits the inlining threshold.</li>
189 <li>The -inline pass no longer misses obvious inlining opportunities just
190 because the callee eventually calls into an external function.</li>
192 <li>The -simplifycfg pass can now "if convert" simple statements into the new
193 <tt>select</tt> instruction.</li>
195 <li>The -loopsimplify pass can now break <a
196 href="http://llvm.cs.uiuc.edu/PR35">natural loops with multiple backedges</a>
197 into multiple nested loops. This enables a variety of subsequent
200 <li>The -adce pass can now eliminate calls to functions that do not not write to
203 <li>The link-time optimizer now runs the -prune-eh pass (to remove unused
204 exception handlers).</li>
206 <li>The -simplifycfg pass can now eliminate simple correlated branches (such as
207 "<tt>if (A < B && A < B)</tt>", and can turn short-circuiting
208 operators into the strict versions when useful (such as "<tt>if (A < B || A
209 > C)</tt>" into "<tt>if (A < B | A > C)</tt>"</li>
211 <li>LLVM now has infrastructure for (simple and sparse conditional) constant
212 propagation of function calls. It currently supports a few math library
213 functions like sqrt/sin/cos/etc.</li>
217 <!--=========================================================================-->
218 <div class="doc_subsubsection">
219 <a name="bugfix">In this release, the following bugs in the previous release
223 <div class="doc_text">
225 <p>Bugs in the LLVM Core:</p>
228 <li><a href="http://llvm.cs.uiuc.edu/PR330">[vmcore] Linker causes erroneous
230 <li><a href="http://llvm.cs.uiuc.edu/PR306">[loopsimplify] Loop simplify
231 incorrectly updates dominator information</a></li>
232 <li><a href="http://llvm.cs.uiuc.edu/PR310">[tailduplicate] DemoteRegToStack
233 breaks SSA form</a></li>
234 <li><a href="http://llvm.cs.uiuc.edu/PR313">[X86] JIT miscompiles unsigned short
235 to floating point cast</a></li>
236 <li><a href="http://llvm.cs.uiuc.edu/PR332">[adce] Crash handling unreachable
237 code that unwinds</a></li>
238 <li><a href="http://llvm.cs.uiuc.edu/PR333">[sparc] LLC can't emit 2 functions
239 of the same name, both having constant pools</a></li>
240 <li><a href="http://llvm.cs.uiuc.edu/PR337">[livevar] Live variables missed
241 physical register use of aliased definition</a></li>
242 <li><a href="http://llvm.cs.uiuc.edu/PR340">Verifier misses malformed switch instruction</a></li>
245 <p>Bugs in the C/C++ front-end:</p>
248 <li><a href="http://llvm.cs.uiuc.edu/PR326">[llvmgcc] Crash on use of undeclared
250 <li><a href="http://llvm.cs.uiuc.edu/PR298">[llvmgcc] Variable length array
251 indexing miscompiled</a></li>
255 <!-- *********************************************************************** -->
256 <div class="doc_section">
257 <a name="portability">Portability and Supported Platforms</a>
259 <!-- *********************************************************************** -->
261 <div class="doc_text">
263 <p>LLVM has been extensively tested on Intel and AMD machines running Red Hat
264 Linux. It has also been tested under FreeBSD, and on Sun UltraSPARC
265 workstations running Solaris 8. Additionally, LLVM works on Mac OS X 10.3 and
266 above, but only with the C backend and interpreter; no native machine-code
267 generator for the PowerPC is available yet.</p>
269 <p>The core LLVM infrastructure uses
270 <a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
271 to the machine and operating system on which it is built. However, minor
272 porting may be required to get LLVM to work on new platforms. We welcome your
273 portability patches and reports of successful builds or error messages.</p>
277 <!--=========================================================================-->
278 <div class="doc_subsection">
279 In this release, the following portability problems were fixed:
282 <div class="doc_text">
285 <li><a href="http://llvm.cs.uiuc.edu/PR304">warnings compiling Stacker compiler
287 <li><a href="http://llvm.cs.uiuc.edu/PR308">Archive file reader doesn't
288 understand abbreviated names in headers</a></li>
293 <!-- *********************************************************************** -->
294 <div class="doc_section">
295 <a name="knownproblems">Known Problems</a>
297 <!-- *********************************************************************** -->
299 <div class="doc_text">
301 <p>This section contains all known problems with the LLVM system, listed by
302 component. As new problems are discovered, they will be added to these
303 sections. If you run into a problem, please check the <a
304 href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
305 there isn't already one.</p>
309 <!-- ======================================================================= -->
310 <div class="doc_subsection">
311 <a name="experimental">Experimental features included with this release</a>
314 <div class="doc_text">
316 <p>The following components of this LLVM release are either untested, known to
317 be broken or unreliable, or are in early development. These components should
318 not be relied on, and bugs should not be filed against them, but they may be
319 useful to some people. In particular, if you would like to work on one of these
320 components, please contact us on the llvmdev list.</p>
323 <li>The following passes are incomplete or buggy: <tt>-pgmdep, -memdep,
324 -ipmodref, -sortstructs, -swapstructs, -cee</tt></li>
326 <li>The <tt>-pre</tt> pass is incomplete (there are cases it doesn't handle that
327 it should) and not thoroughly tested.</li>
328 <li>The <tt>llvm-ar</tt> tool is incomplete and probably buggy.</li>
329 <li>The <tt>llvm-db</tt> tool is in a very early stage of development.</li>
334 <!-- ======================================================================= -->
335 <div class="doc_subsection">
336 <a name="core">Known problems with the LLVM Core</a>
339 <div class="doc_text">
343 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
346 <li>The JIT does not use mutexes to protect its internal data structures. As
347 such, execution of a threaded program could cause these data structures to be
350 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
352 <li>Linking in static archive files (.a files) is very slow (there is no symbol
353 table in the archive).</li>
355 <li>The gccld program <a href="http://llvm.cs.uiuc.edu/PR139">does not link
356 objects/archives in the order specified on the command line.</a></li>
358 <li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not mark
359 values live across a setjmp as volatile</a>. This missing feature only affects
360 targets whose setjmp/longjmp libraries do not save and restore the entire
365 <!-- ======================================================================= -->
366 <div class="doc_subsection">
367 <a name="c-fe">Known problems with the C front-end</a>
370 <!-- _______________________________________________________________________ -->
371 <div class="doc_subsubsection">Bugs</div>
373 <div class="doc_text">
375 <li>C99 Variable sized arrays do not release stack memory when they go out of
376 scope. Thus, the following program may run out of stack space:
378 for (i = 0; i != 1000000; ++i) {
384 <li>Initialization of global union variables can only be done <a
385 href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=162">with the largest union
388 <li><a href="http://llvm.cs.uiuc.edu/PR244">[llvm-gcc] Error when an implicitly
389 external function is re-declared as static</a></li>
394 <!-- _______________________________________________________________________ -->
395 <div class="doc_subsubsection">
399 <div class="doc_text">
403 <li>Inline assembly is not yet supported.</li>
405 <li>"long double" is transformed by the front-end into "double". There is no
406 support for floating point data types of any size other than 32 and 64
409 <li>The following Unix system functionality has not been tested and may not
412 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
413 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
414 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
415 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
416 - These functions have not been tested.
419 <li>Although many GCC extensions are supported, some are not. In particular,
420 the following extensions are known to <b>not be</b> supported:
422 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
423 <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>
424 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
425 <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>
426 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
427 <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>
428 <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>
429 <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>
430 <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>
431 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
432 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
435 <p>The following GCC extensions are <b>partially</b> supported. An ignored
436 attribute means that the LLVM compiler ignores the presence of the attribute,
437 but the code should still work. An unsupported attribute is one which is
438 ignored by the LLVM compiler and will cause a different interpretation of
442 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
443 Arrays whose length is computed at run time.<br>
444 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
446 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
448 Declaring that functions have no side effects or that they can never
451 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
452 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
453 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
455 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
456 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
457 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
459 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
460 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
461 <tt>fastcall</tt>, all other target specific attributes</li>
463 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
464 Specifying attributes of variables.<br>
465 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
466 <tt>deprecated</tt>, <tt>transparent_union</tt>,
467 <tt>unused</tt>, <tt>weak</tt><br>
469 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
470 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
471 <tt>vector_size</tt>, <tt>dllimport</tt>,
472 <tt>dllexport</tt>, all target specific attributes.</li>
474 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
475 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
476 <tt>deprecated</tt>, <tt>may_alias</tt><br>
478 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
479 all target specific attributes.</li>
481 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
482 Other built-in functions.<br>
483 We support all builtins which have a C language equivalent (e.g.,
484 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
485 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
486 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> (ignored).</li>
490 <p>The following extensions <b>are</b> known to be supported:</p>
493 <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>
494 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
495 <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>
496 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
497 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
498 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
499 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
500 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
501 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
502 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
503 <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>
504 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
505 <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>
506 <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>
507 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
508 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
509 or arrays as values.</li>
510 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
511 <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>
512 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
513 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
514 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
515 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
516 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
517 <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>
518 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
519 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
520 <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>
521 <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>
522 <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>
523 <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>
524 <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>
525 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
530 <p>If you run into GCC extensions which have not been included in any of these
531 lists, please let us know (also including whether or not they work).</p>
535 <!-- ======================================================================= -->
536 <div class="doc_subsection">
537 <a name="c++-fe">Known problems with the C++ front-end</a>
540 <div class="doc_text">
542 <p>For this release, the C++ front-end is considered to be fully functional but
543 has not been tested as thoroughly as the C front-end. It has been tested and
544 works for a number of non-trivial programs, but there may be lurking bugs.
545 Please report any bugs or problems.</p>
549 <!-- _______________________________________________________________________ -->
550 <div class="doc_subsubsection">Bugs</div>
552 <div class="doc_text">
555 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
560 <!-- _______________________________________________________________________ -->
561 <div class="doc_subsubsection">
565 <div class="doc_text">
569 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
570 parser is significantly more standards compliant (and picky) than prior GCC
571 versions. For more information, see the C++ section of the <a
572 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
574 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
575 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
576 function and in the <tt>setjmp</tt> receiver function may not be run.
577 Objects in intervening stack frames will be destroyed, however (which is
578 better than most compilers).</li>
580 <li>The LLVM C++ front-end follows the <a
581 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
582 This document, which is not Itanium specific, specifies a standard for name
583 mangling, class layout, v-table layout, RTTI formats, and other C++
584 representation issues. Because we use this API, code generated by the LLVM
585 compilers should be binary compatible with machine code generated by other
586 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
587 <i>However</i>, the exception handling mechanism used by LLVM is very
588 different from the model used in the Itanium ABI, so <b>exceptions will not
589 interact correctly</b>. </li>
595 <!-- ======================================================================= -->
596 <div class="doc_subsection">
597 <a name="x86-be">Known problems with the X86 back-end</a>
600 <div class="doc_text">
608 <!-- ======================================================================= -->
609 <div class="doc_subsection">
610 <a name="sparc-be">Known problems with the Sparc back-end</a>
613 <div class="doc_text">
616 <li>There are several programs in the LLVM testsuite that the Sparc code generator is known to miscompile.</li>
621 <!-- ======================================================================= -->
622 <div class="doc_subsection">
623 <a name="c-be">Known problems with the C back-end</a>
626 <div class="doc_text">
630 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
631 Analysis rules. As such, special options may be necessary to compile the code
632 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
633 problem probably cannot be fixed.</li>
635 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
636 cannot include special floating point numbers like Not-A-Number or
639 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
640 supported</a>. This should not affect LLVM produced by the C or C++
647 <!-- *********************************************************************** -->
648 <div class="doc_section">
649 <a name="additionalinfo">Additional Information</a>
651 <!-- *********************************************************************** -->
653 <div class="doc_text">
655 <p>A wide variety of additional information is available on the LLVM web page,
656 including mailing lists and publications describing algorithms and components
657 implemented in LLVM. The web page also contains versions of the API
658 documentation which is up-to-date with the CVS version of the source code. You
659 can access versions of these documents specific to this release by going into
660 the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
662 <p>If you have any questions or comments about LLVM, please feel free to contact
663 us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
668 <!-- *********************************************************************** -->
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