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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="#sparcv9-be">Known problems with the SparcV9 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 many <a
75 href="#newfeatures">new features</a>, and <a href="#bugfix">fixes 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
109 href="GarbageCollection.html">Accurate Garbage Collection</a>, enabling the use
110 of aggressive copying and generational collectors.</li>
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-bcanalyzer. This tool can compute basic
121 statistics and bytecode density statistics on a module or function basis and
122 also dump out bytecode in a textual format that is lower level than assembly
123 (values are not resolved from slot numbers). It should only be of interest to
124 (a) those who are working to improve the bytecode format and (b) those who
125 really want to understand or document the details of the bytecode format.</li>
126 <li>The <a href="BytecodeFormat.html">LLVM Bytecode file format</a> is now
128 <li>LLVM now provides an <a
129 href="LangRef.html#i_isunordered">llvm.isunordered</a> intrinsic for efficient
130 implementation of unordered floating point comparisons.</li>
131 <li>The llvmgcc front-end now supports the GCC builtins for ISO C99 floating
132 point comparison macros (e.g., <tt>__builtin_islessequal</tt>).</li>
133 <li>Now that there are more source files than can fit on a 32Kbyte command
134 line (Linux's limit), there's a new utility for searching the sources. The
135 llvmgrep tool in the utils directory combines an egrep and a find without
136 passing filenames through the command line. This improves performance
137 slightly. Simply run llvmgrep like you might egrep but leave off the file
139 <li>We now generate HTML documentation and man pages for the tools from a single
140 source (perl-style POD files).</li>
141 <li>The LLVM code generator can now dynamically load targets from shared
148 <!--=========================================================================-->
149 <div class="doc_subsubsection">
150 In this release, the following missing features were implemented:
153 <div class="doc_text">
156 <li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
157 more than 256 elements</a></li>
158 <li><a href="http://llvm.cs.uiuc.edu/PR38">[bugpoint] External functions used in
159 non-instruction entities, such as global constant initializer</a></li>
160 <li><a href="http://llvm.cs.uiuc.edu/PR178">Stacker does not handle targets
161 with 64-bit pointers.</a></li>
162 <li><a href="http://llvm.cs.uiuc.edu/PR290">Bugpoint doesn't support
163 uses of external fns by immediate constant exprs</a></li>
168 <!--=========================================================================-->
169 <div class="doc_subsubsection">
170 <a name="qualityofimp">In this release, the following Quality of Implementation
171 issues were fixed:</a>
174 <div class="doc_text">
177 <li><a href="http://llvm.cs.uiuc.edu/PR305">LLVM tools will happily spew
178 bytecode onto your terminal</a></li>
179 <li><a href="http://llvm.cs.uiuc.edu/PR329">[llvmgcc] type names are not emitted
180 for structure typedefs</a></li>
181 <li>All documentation is now conformant to the HTML 4.01 (Strict) level.</li>
182 <li>The spurious "WARNING: Found global types that are not compatible" warning
183 produced when linking C++ programs has been fixed.</li>
184 <li><a href="http://llvm.cs.uiuc.edu/PR391">lli Doesn't Handle Exceptions From
185 Bytecode Reader</a></li>
190 <!--=========================================================================-->
191 <div class="doc_subsubsection">
192 In this release, the following build problems were fixed:
195 <div class="doc_text">
197 <li><a href="http://llvm.cs.uiuc.edu/PR301">Minor configure bugs with
198 -disable/enable-povray and -disable-spec</a></li>
199 <li><a href="http://llvm.cs.uiuc.edu/PR289">shell scripts output by gccld don't
200 work if you change PATH</a></li>
201 <li><a href="http://llvm.cs.uiuc.edu/PR364">[llvmgcc] llvmgcc does not compile
202 with gcc 3.4</a></li>
203 <li><a href="http://llvm.cs.uiuc.edu/PR373">[llvmgcc] obstack.h relies on
204 obsolete casts-as-lvalues GCC extension</a></li>
208 <!--=========================================================================-->
209 <div class="doc_subsubsection">
210 <a name="codequality">This release includes the following Code Quality
214 <div class="doc_text">
216 <li>Fixed: <a href="http://llvm.cs.uiuc.edu/PR309">[vmcore] Code quality problem
217 due to long operand of getelementptr</a></li>
219 <li>The X86 backend now generates substantially better code for 64-bit integer
220 and floating point operations.</li>
222 <li>The -inline pass no longer inlines mutually recursive functions until it
223 hits the inlining threshold.</li>
225 <li>The -inline pass no longer misses obvious inlining opportunities just
226 because the callee eventually calls into an external function.</li>
228 <li>The -simplifycfg pass can now "if convert" simple statements into the new
229 <tt>select</tt> instruction.</li>
231 <li>The -loopsimplify pass can now break <a
232 href="http://llvm.cs.uiuc.edu/PR35">natural loops with multiple backedges</a>
233 into multiple nested loops. This enables a variety of subsequent
236 <li>The -adce pass can now eliminate calls to functions that do not not write to
239 <li>The link-time optimizer now runs the -prune-eh pass (to remove unused
240 exception handlers).</li>
242 <li>The -simplifycfg pass can now eliminate simple correlated branches (such as
243 "<tt>if (A < B && A < B)</tt>", and can turn short-circuiting
244 operators into the strict versions when useful (such as "<tt>if (A < B || A
245 > C)</tt>" into "<tt>if (A < B | A > C)</tt>"</li>
247 <li>LLVM now has infrastructure for (simple and sparse conditional) constant
248 propagation of function calls. It currently supports a few math library
249 functions like sqrt/sin/cos/etc.</li>
251 <li>The C backend now emits <a href="http://llvm.cs.uiuc.edu/PR334">Syntactic
252 loops</a> in the code to help C compilers whose optimizers do not recognize
253 loops formed from gotos (like GCC).</li>
255 <li>Fixed: <a href="http://llvm.cs.uiuc.edu/PR368">[sparcv9] null
256 often spilled to constant pool</a>.</li>
260 <!--=========================================================================-->
261 <div class="doc_subsubsection">
262 <a name="bugfix">In this release, the following bugs in the previous release
266 <div class="doc_text">
268 <p>Bugs in the LLVM Core:</p>
271 <li><a href="http://llvm.cs.uiuc.edu/PR306">[loopsimplify] Loop simplify
272 incorrectly updates dominator information</a></li>
273 <li><a href="http://llvm.cs.uiuc.edu/PR310">[tailduplicate] DemoteRegToStack
274 breaks SSA form</a></li>
275 <li><a href="http://llvm.cs.uiuc.edu/PR313">[X86] JIT miscompiles unsigned short
276 to floating point cast</a></li>
277 <li><a href="http://llvm.cs.uiuc.edu/PR315">[jit] abort, don't warn, when
278 missing external functions encountered</a></li>
279 <li><a href="http://llvm.cs.uiuc.edu/PR330">[vmcore] Linker causes erroneous
281 <li><a href="http://llvm.cs.uiuc.edu/PR332">[adce] Crash handling unreachable
282 code that unwinds</a></li>
283 <li><a href="http://llvm.cs.uiuc.edu/PR333">[sparcv9] LLC can't emit 2 functions
284 of the same name, both having constant pools</a></li>
285 <li><a href="http://llvm.cs.uiuc.edu/PR337">[livevar] Live variables missed
286 physical register use of aliased definition</a></li>
287 <li><a href="http://llvm.cs.uiuc.edu/PR340">Verifier misses malformed switch
289 <li><a href="http://llvm.cs.uiuc.edu/PR365">[asmwriter] Asm writer aborts if
290 an instruction is not embedded into a function</a></li>
291 <li><a href="http://llvm.cs.uiuc.edu/PR369">[X86] stackifier crash on floating
292 point setcc X, X</a></li>
295 <p>Bugs in the C/C++ front-end:</p>
298 <li><a href="http://llvm.cs.uiuc.edu/PR298">[llvmgcc] Variable length array
299 indexing miscompiled</a></li>
300 <li><a href="http://llvm.cs.uiuc.edu/PR326">[llvmgcc] Crash on use of undeclared
302 <li><a href="http://llvm.cs.uiuc.edu/PR355">[llvmgcc] Errors handling function
303 prototypes that take opaque structs by-value</a></li>
304 <li><a href="http://llvm.cs.uiuc.edu/PR374">[llvmgcc] Crash compiling variable
305 length array of structures</a></li>
306 <li><a href="http://llvm.cs.uiuc.edu/PR377">[llvmgcc] miscompilation of staticly
307 initialized unsigned bitfields</a></li>
308 <li><a href="http://llvm.cs.uiuc.edu/PR396">[llvm-gcc] Crash casting function to void</a></li>
312 <!-- *********************************************************************** -->
313 <div class="doc_section">
314 <a name="portability">Portability and Supported Platforms</a>
316 <!-- *********************************************************************** -->
318 <div class="doc_text">
320 <p>LLVM is known to work in the following platforms:</p>
323 <li>Intel and AMD machines running Red Hat Linux and FreeBSD (and probably
324 other unix-like systems).</li>
325 <li>Sun UltraSPARC workstations running Solaris 8.</li>
326 <li>PowerPC-based Mac OS X boxes, running 10.3 and above (C backend and
327 interpreter only, no native codegen is available yet).</li>
328 <li>Intel and AMD machines running on Win32 with the Cygwin libraries.</li>
332 <p>The core LLVM infrastructure uses
333 <a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
334 to the machine and operating system on which it is built. However, minor
335 porting may be required to get LLVM to work on new platforms. We welcome your
336 portability patches and reports of successful builds or error messages.</p>
338 <p>Note that the LLVM build system does not currently support directories with
339 spaces on them when running on Win32/cygwin. We strongly recommend running
340 LLVM and the C frontend out of a top-level directory without spaces (e.g.,
341 <tt>/cygdrive/c/llvm</tt>). Also, make sure to install <b>all</b> of the
342 cygwin packages. By default, many important tools are not installed that
343 are needed by the LLVM build process or test suite (e.g., /bin/time).</p>
347 <!--=========================================================================-->
348 <div class="doc_subsection">
349 In this release, the following portability problems were fixed:
352 <div class="doc_text">
355 <li><a href="http://llvm.cs.uiuc.edu/PR304">warnings compiling Stacker compiler
357 <li><a href="http://llvm.cs.uiuc.edu/PR308">Archive file reader doesn't
358 understand abbreviated names in headers</a></li>
363 <!-- *********************************************************************** -->
364 <div class="doc_section">
365 <a name="knownproblems">Known Problems</a>
367 <!-- *********************************************************************** -->
369 <div class="doc_text">
371 <p>This section contains all known problems with the LLVM system, listed by
372 component. As new problems are discovered, they will be added to these
373 sections. If you run into a problem, please check the <a
374 href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
375 there isn't already one.</p>
379 <!-- ======================================================================= -->
380 <div class="doc_subsection">
381 <a name="experimental">Experimental features included with this release</a>
384 <div class="doc_text">
386 <p>The following components of this LLVM release are either untested, known to
387 be broken or unreliable, or are in early development. These components should
388 not be relied on, and bugs should not be filed against them, but they may be
389 useful to some people. In particular, if you would like to work on one of these
390 components, please contact us on the llvmdev list.</p>
393 <li>The following passes are incomplete or buggy: <tt>-pgmdep, -memdep,
394 -ipmodref, -cee</tt></li>
396 <li>The <tt>-pre</tt> pass is incomplete (there are cases it doesn't handle that
397 it should) and not thoroughly tested.</li>
398 <li>The <tt>llvm-ar</tt> tool is incomplete and probably buggy.</li>
399 <li>The <tt>llvm-db</tt> tool is in a very early stage of development.</li>
404 <!-- ======================================================================= -->
405 <div class="doc_subsection">
406 <a name="core">Known problems with the LLVM Core</a>
409 <div class="doc_text">
413 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
416 <li>The JIT does not use mutexes to protect its internal data structures. As
417 such, execution of a threaded program could cause these data structures to be
420 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
422 <li>Linking in static archive files (.a files) is very slow (there is no symbol
423 table in the archive).</li>
425 <li>The gccld program <a href="http://llvm.cs.uiuc.edu/PR139">does not link
426 objects/archives in the order specified on the command line.</a></li>
428 <li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not mark
429 values live across a setjmp as volatile</a>. This missing feature only affects
430 targets whose setjmp/longjmp libraries do not save and restore the entire
435 <!-- ======================================================================= -->
436 <div class="doc_subsection">
437 <a name="c-fe">Known problems with the C front-end</a>
440 <!-- _______________________________________________________________________ -->
441 <div class="doc_subsubsection">Bugs</div>
443 <div class="doc_text">
445 <li>C99 Variable sized arrays do not release stack memory when they go out of
446 scope. Thus, the following program may run out of stack space:
448 for (i = 0; i != 1000000; ++i) {
454 <li>Initialization of global union variables can only be done <a
455 href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=162">with the largest union
458 <li><a href="http://llvm.cs.uiuc.edu/PR244">[llvm-gcc] Error when an implicitly
459 external function is re-declared as static</a></li>
464 <!-- _______________________________________________________________________ -->
465 <div class="doc_subsubsection">
469 <div class="doc_text">
473 <li>Inline assembly is not yet supported.</li>
475 <li>"long double" is transformed by the front-end into "double". There is no
476 support for floating point data types of any size other than 32 and 64
479 <li>The following Unix system functionality has not been tested and may not
482 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
483 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
484 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
485 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
486 - These functions have not been tested.
489 <li>Although many GCC extensions are supported, some are not. In particular,
490 the following extensions are known to <b>not be</b> supported:
492 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
493 <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>
494 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
495 <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>
496 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
497 <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>
498 <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>
499 <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>
500 <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>
501 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
502 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
505 <p>The following GCC extensions are <b>partially</b> supported. An ignored
506 attribute means that the LLVM compiler ignores the presence of the attribute,
507 but the code should still work. An unsupported attribute is one which is
508 ignored by the LLVM compiler and will cause a different interpretation of
512 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
513 Arrays whose length is computed at run time.<br>
514 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
516 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
518 Declaring that functions have no side effects or that they can never
521 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
522 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
523 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
525 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
526 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
527 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
529 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
530 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
531 <tt>fastcall</tt>, all other target specific attributes</li>
533 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
534 Specifying attributes of variables.<br>
535 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
536 <tt>deprecated</tt>, <tt>transparent_union</tt>,
537 <tt>unused</tt>, <tt>weak</tt><br>
539 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
540 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
541 <tt>vector_size</tt>, <tt>dllimport</tt>,
542 <tt>dllexport</tt>, all target specific attributes.</li>
544 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
545 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
546 <tt>deprecated</tt>, <tt>may_alias</tt><br>
548 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
549 all target specific attributes.</li>
551 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
552 Other built-in functions.<br>
553 We support all builtins which have a C language equivalent (e.g.,
554 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
555 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
556 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt>
557 (currently ignored). We also support builtins for ISO C99 floating
558 point comparison macros (e.g., <tt>__builtin_islessequal</tt>).</li>
561 <p>The following extensions <b>are</b> known to be supported:</p>
564 <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>
565 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
566 <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>
567 <li><a href="http://gcc.gnu.org/onlinedocs/gcc-3.4.0/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
568 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
569 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
570 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
571 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
572 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
573 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
574 <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>
575 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
576 <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>
577 <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>
578 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
579 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
580 or arrays as values.</li>
581 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
582 <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>
583 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
584 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
585 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
586 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
587 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
588 <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>
589 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
590 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
591 <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>
592 <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>
593 <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>
594 <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>
595 <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>
596 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
601 <p>If you run into GCC extensions which have not been included in any of these
602 lists, please let us know (also including whether or not they work).</p>
606 <!-- ======================================================================= -->
607 <div class="doc_subsection">
608 <a name="c++-fe">Known problems with the C++ front-end</a>
611 <div class="doc_text">
613 <p>For this release, the C++ front-end is considered to be fully functional but
614 has not been tested as thoroughly as the C front-end. It has been tested and
615 works for a number of non-trivial programs, but there may be lurking bugs.
616 Please report any bugs or problems.</p>
620 <!-- _______________________________________________________________________ -->
621 <div class="doc_subsubsection">Bugs</div>
623 <div class="doc_text">
626 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
631 <!-- _______________________________________________________________________ -->
632 <div class="doc_subsubsection">
636 <div class="doc_text">
640 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
641 parser is significantly more standards compliant (and picky) than prior GCC
642 versions. For more information, see the C++ section of the <a
643 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
645 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
646 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
647 function and in the <tt>setjmp</tt> receiver function may not be run.
648 Objects in intervening stack frames will be destroyed, however (which is
649 better than most compilers).</li>
651 <li>The LLVM C++ front-end follows the <a
652 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
653 This document, which is not Itanium specific, specifies a standard for name
654 mangling, class layout, v-table layout, RTTI formats, and other C++
655 representation issues. Because we use this API, code generated by the LLVM
656 compilers should be binary compatible with machine code generated by other
657 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
658 <i>However</i>, the exception handling mechanism used by LLVM is very
659 different from the model used in the Itanium ABI, so <b>exceptions will not
660 interact correctly</b>. </li>
666 <!-- ======================================================================= -->
667 <div class="doc_subsection">
668 <a name="x86-be">Known problems with the X86 back-end</a>
671 <div class="doc_text">
674 <li>Optimized (Release) versions of LLVM built with GCC 3.3.2 or 3.3.3 will
675 produce an llc tool that always enters an infinite loop due to what
676 appears to be an optimization bug (-O2 and -O3) in those versions of GCC.
677 This problem does not happen in GCC 3.3.1 nor GCC 3.4.0 nor does it happen if
678 you build a Debug version of LLVM. You are cautioned not to use GCC 3.3.2 or
679 GCC 3.3.3 to build Optimized versions of LLVM. It is unclear whether this problem
680 affects other backends but it is unlikely.</li>
685 <!-- ======================================================================= -->
686 <div class="doc_subsection">
687 <a name="sparcv9-be">Known problems with the SparcV9 back-end</a>
690 <div class="doc_text">
693 <li><a href="http://llvm.cs.uiuc.edu/PR60">[sparcv9] SparcV9 backend miscompiles
694 several programs in the LLVM test suite</a></li>
699 <!-- ======================================================================= -->
700 <div class="doc_subsection">
701 <a name="c-be">Known problems with the C back-end</a>
704 <div class="doc_text">
708 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
709 Analysis rules. As such, special options may be necessary to compile the code
710 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
711 problem probably cannot be fixed.</li>
713 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
714 cannot include special floating point numbers like Not-A-Number or
717 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
718 supported</a>. This should not affect LLVM produced by the C or C++
725 <!-- *********************************************************************** -->
726 <div class="doc_section">
727 <a name="additionalinfo">Additional Information</a>
729 <!-- *********************************************************************** -->
731 <div class="doc_text">
733 <p>A wide variety of additional information is available on the LLVM web page,
734 including mailing lists and publications describing algorithms and components
735 implemented in LLVM. The web page also contains versions of the API
736 documentation which is up-to-date with the CVS version of the source code. You
737 can access versions of these documents specific to this release by going into
738 the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
740 <p>If you have any questions or comments about LLVM, please feel free to contact
741 us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
746 <!-- *********************************************************************** -->
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