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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>
186 <li><a href="http://llvm.cs.uiuc.edu/PR392">Global Vars Have (Somewhat) Limited
188 <li><a href="http://llvm.cs.uiuc.edu/PR341">operator<< on a Value* now prints the address of the object instead of its contents.</a></li>
189 <li><a href="http://llvm.cs.uiuc.edu/PR402">Bytecode Enhancements
191 <li><a href="http://llvm.cs.uiuc.edu/PR404">[loopsimplify] Loop simplify is really slow on 252.eon</a></li>
196 <!--=========================================================================-->
197 <div class="doc_subsubsection">
198 In this release, the following build problems were fixed:
201 <div class="doc_text">
203 <li><a href="http://llvm.cs.uiuc.edu/PR301">Minor configure bugs with
204 -disable/enable-povray and -disable-spec</a></li>
205 <li><a href="http://llvm.cs.uiuc.edu/PR289">shell scripts output by gccld don't
206 work if you change PATH</a></li>
207 <li><a href="http://llvm.cs.uiuc.edu/PR364">[llvmgcc] llvmgcc does not compile
208 with gcc 3.4</a></li>
209 <li><a href="http://llvm.cs.uiuc.edu/PR373">[llvmgcc] obstack.h relies on
210 obsolete casts-as-lvalues GCC extension</a></li>
214 <!--=========================================================================-->
215 <div class="doc_subsubsection">
216 <a name="codequality">This release includes the following Code Quality
220 <div class="doc_text">
222 <li>Fixed: <a href="http://llvm.cs.uiuc.edu/PR309">[vmcore] Code quality problem
223 due to long operand of getelementptr</a></li>
225 <li>The X86 backend now generates substantially better code for 64-bit integer
226 and floating point operations.</li>
228 <li>The -inline pass no longer inlines mutually recursive functions until it
229 hits the inlining threshold.</li>
231 <li>The -inline pass no longer misses obvious inlining opportunities just
232 because the callee eventually calls into an external function.</li>
234 <li>The -simplifycfg pass can now "if convert" simple statements into the new
235 <tt>select</tt> instruction.</li>
237 <li>The -loopsimplify pass can now break <a
238 href="http://llvm.cs.uiuc.edu/PR35">natural loops with multiple backedges</a>
239 into multiple nested loops. This enables a variety of subsequent
242 <li>The -adce pass can now eliminate calls to functions that do not not write to
245 <li>The link-time optimizer now runs the -prune-eh pass (to remove unused
246 exception handlers).</li>
248 <li>The -simplifycfg pass can now eliminate simple correlated branches (such as
249 "<tt>if (A < B && A < B)</tt>", and can turn short-circuiting
250 operators into the strict versions when useful (such as "<tt>if (A < B || A
251 > C)</tt>" into "<tt>if (A < B | A > C)</tt>"</li>
253 <li>LLVM now has infrastructure for (simple and sparse conditional) constant
254 propagation of function calls. It currently supports a few math library
255 functions like sqrt/sin/cos/etc.</li>
257 <li>The C backend now emits <a href="http://llvm.cs.uiuc.edu/PR334">Syntactic
258 loops</a> in the code to help C compilers whose optimizers do not recognize
259 loops formed from gotos (like GCC).</li>
261 <li>Fixed: <a href="http://llvm.cs.uiuc.edu/PR368">[sparcv9] null
262 often spilled to constant pool</a>.</li>
264 <li>Fixed: <a href="Http://llvm.cs.uiuc.edu/PR122">[code-cleanup] SymbolTable
265 class cleanup, Type should not derive from Value, eliminate
266 ConstantPointerRef class</a>. All three changes have been made.
269 <!--=========================================================================-->
270 <div class="doc_subsubsection">
271 <a name="bugfix">In this release, the following bugs in the previous release
275 <div class="doc_text">
277 <p>Bugs in the LLVM Core:</p>
280 <li><a href="http://llvm.cs.uiuc.edu/PR306">[loopsimplify] Loop simplify
281 incorrectly updates dominator information</a></li>
282 <li><a href="http://llvm.cs.uiuc.edu/PR310">[tailduplicate] DemoteRegToStack
283 breaks SSA form</a></li>
284 <li><a href="http://llvm.cs.uiuc.edu/PR313">[X86] JIT miscompiles unsigned short
285 to floating point cast</a></li>
286 <li><a href="http://llvm.cs.uiuc.edu/PR315">[jit] abort, don't warn, when
287 missing external functions encountered</a></li>
288 <li><a href="http://llvm.cs.uiuc.edu/PR330">[vmcore] Linker causes erroneous
290 <li><a href="http://llvm.cs.uiuc.edu/PR332">[adce] Crash handling unreachable
291 code that unwinds</a></li>
292 <li><a href="http://llvm.cs.uiuc.edu/PR333">[sparcv9] LLC can't emit 2 functions
293 of the same name, both having constant pools</a></li>
294 <li><a href="http://llvm.cs.uiuc.edu/PR337">[livevar] Live variables missed
295 physical register use of aliased definition</a></li>
296 <li><a href="http://llvm.cs.uiuc.edu/PR340">Verifier misses malformed switch
298 <li><a href="http://llvm.cs.uiuc.edu/PR365">[asmwriter] Asm writer aborts if
299 an instruction is not embedded into a function</a></li>
300 <li><a href="http://llvm.cs.uiuc.edu/PR369">[X86] stackifier crash on floating
301 point setcc X, X</a></li>
302 <li><a href="http://llvm.cs.uiuc.edu/PR407">Can't add LICM to FunctionPassManager</a></li>
305 <p>Bugs in the C/C++ front-end:</p>
308 <li><a href="http://llvm.cs.uiuc.edu/PR298">[llvmgcc] Variable length array
309 indexing miscompiled</a></li>
310 <li><a href="http://llvm.cs.uiuc.edu/PR326">[llvmgcc] Crash on use of undeclared
312 <li><a href="http://llvm.cs.uiuc.edu/PR355">[llvmgcc] Errors handling function
313 prototypes that take opaque structs by-value</a></li>
314 <li><a href="http://llvm.cs.uiuc.edu/PR374">[llvmgcc] Crash compiling variable
315 length array of structures</a></li>
316 <li><a href="http://llvm.cs.uiuc.edu/PR377">[llvmgcc] miscompilation of staticly
317 initialized unsigned bitfields</a></li>
318 <li><a href="http://llvm.cs.uiuc.edu/PR396">[llvm-gcc] Crash casting function to void</a></li>
322 <!-- *********************************************************************** -->
323 <div class="doc_section">
324 <a name="portability">Portability and Supported Platforms</a>
326 <!-- *********************************************************************** -->
328 <div class="doc_text">
330 <p>LLVM is known to work in the following platforms:</p>
333 <li>Intel and AMD machines running Red Hat Linux and FreeBSD (and probably
334 other unix-like systems).</li>
335 <li>Sun UltraSPARC workstations running Solaris 8.</li>
336 <li>PowerPC-based Mac OS X boxes, running 10.3 and above (C backend and
337 interpreter only, no native codegen is available yet).</li>
338 <li>Intel and AMD machines running on Win32 with the Cygwin libraries.</li>
342 <p>The core LLVM infrastructure uses
343 <a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
344 to the machine and operating system on which it is built. However, minor
345 porting may be required to get LLVM to work on new platforms. We welcome your
346 portability patches and reports of successful builds or error messages.</p>
348 <p>Note that the LLVM build system does not currently support directories with
349 spaces on them when running on Win32/cygwin. We strongly recommend running
350 LLVM and the C frontend out of a top-level directory without spaces (e.g.,
351 <tt>/cygdrive/c/llvm</tt>). Also, make sure to install <b>all</b> of the
352 cygwin packages. By default, many important tools are not installed that
353 are needed by the LLVM build process or test suite (e.g., /bin/time).</p>
357 <!--=========================================================================-->
358 <div class="doc_subsection">
359 In this release, the following portability problems were fixed:
362 <div class="doc_text">
365 <li><a href="http://llvm.cs.uiuc.edu/PR304">warnings compiling Stacker compiler
367 <li><a href="http://llvm.cs.uiuc.edu/PR308">Archive file reader doesn't
368 understand abbreviated names in headers</a></li>
373 <!-- *********************************************************************** -->
374 <div class="doc_section">
375 <a name="knownproblems">Known Problems</a>
377 <!-- *********************************************************************** -->
379 <div class="doc_text">
381 <p>This section contains all known problems with the LLVM system, listed by
382 component. As new problems are discovered, they will be added to these
383 sections. If you run into a problem, please check the <a
384 href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
385 there isn't already one.</p>
389 <!-- ======================================================================= -->
390 <div class="doc_subsection">
391 <a name="experimental">Experimental features included with this release</a>
394 <div class="doc_text">
396 <p>The following components of this LLVM release are either untested, known to
397 be broken or unreliable, or are in early development. These components should
398 not be relied on, and bugs should not be filed against them, but they may be
399 useful to some people. In particular, if you would like to work on one of these
400 components, please contact us on the llvmdev list.</p>
403 <li>The following passes are incomplete or buggy: <tt>-pgmdep, -memdep,
404 -ipmodref, -cee</tt></li>
406 <li>The <tt>-pre</tt> pass is incomplete (there are cases it doesn't handle that
407 it should) and not thoroughly tested.</li>
408 <li>The <tt>llvm-ar</tt> tool is incomplete and probably buggy.</li>
409 <li>The <tt>llvm-db</tt> tool is in a very early stage of development.</li>
414 <!-- ======================================================================= -->
415 <div class="doc_subsection">
416 <a name="core">Known problems with the LLVM Core</a>
419 <div class="doc_text">
423 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
426 <li>The JIT does not use mutexes to protect its internal data structures. As
427 such, execution of a threaded program could cause these data structures to be
430 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
432 <li>Linking in static archive files (.a files) is very slow (there is no symbol
433 table in the archive).</li>
435 <li>The gccld program <a href="http://llvm.cs.uiuc.edu/PR139">does not link
436 objects/archives in the order specified on the command line.</a></li>
438 <li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not mark
439 values live across a setjmp as volatile</a>. This missing feature only affects
440 targets whose setjmp/longjmp libraries do not save and restore the entire
445 <!-- ======================================================================= -->
446 <div class="doc_subsection">
447 <a name="c-fe">Known problems with the C front-end</a>
450 <!-- _______________________________________________________________________ -->
451 <div class="doc_subsubsection">Bugs</div>
453 <div class="doc_text">
455 <li>C99 Variable sized arrays do not release stack memory when they go out of
456 scope. Thus, the following program may run out of stack space:
458 for (i = 0; i != 1000000; ++i) {
464 <li>Initialization of global union variables can only be done <a
465 href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=162">with the largest union
468 <li><a href="http://llvm.cs.uiuc.edu/PR244">[llvm-gcc] Error when an implicitly
469 external function is re-declared as static</a></li>
474 <!-- _______________________________________________________________________ -->
475 <div class="doc_subsubsection">
479 <div class="doc_text">
483 <li>Inline assembly is not yet supported.</li>
485 <li>"long double" is transformed by the front-end into "double". There is no
486 support for floating point data types of any size other than 32 and 64
489 <li>The following Unix system functionality has not been tested and may not
492 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
493 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
494 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
495 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
496 - These functions have not been tested.
499 <li>Although many GCC extensions are supported, some are not. In particular,
500 the following extensions are known to <b>not be</b> supported:
502 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
503 <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>
504 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
505 <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>
506 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
507 <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>
508 <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>
509 <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>
510 <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>
511 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
512 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
515 <p>The following GCC extensions are <b>partially</b> supported. An ignored
516 attribute means that the LLVM compiler ignores the presence of the attribute,
517 but the code should still work. An unsupported attribute is one which is
518 ignored by the LLVM compiler and will cause a different interpretation of
522 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
523 Arrays whose length is computed at run time.<br>
524 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
526 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
528 Declaring that functions have no side effects or that they can never
531 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
532 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
533 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
535 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
536 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
537 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
539 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
540 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
541 <tt>fastcall</tt>, all other target specific attributes</li>
543 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
544 Specifying attributes of variables.<br>
545 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
546 <tt>deprecated</tt>, <tt>transparent_union</tt>,
547 <tt>unused</tt>, <tt>weak</tt><br>
549 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
550 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
551 <tt>vector_size</tt>, <tt>dllimport</tt>,
552 <tt>dllexport</tt>, all target specific attributes.</li>
554 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
555 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
556 <tt>deprecated</tt>, <tt>may_alias</tt><br>
558 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
559 all target specific attributes.</li>
561 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
562 Other built-in functions.<br>
563 We support all builtins which have a C language equivalent (e.g.,
564 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
565 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
566 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt>
567 (currently ignored). We also support builtins for ISO C99 floating
568 point comparison macros (e.g., <tt>__builtin_islessequal</tt>).</li>
571 <p>The following extensions <b>are</b> known to be supported:</p>
574 <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>
575 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
576 <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>
577 <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>
578 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
579 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
580 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
581 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
582 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
583 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
584 <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>
585 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
586 <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>
587 <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>
588 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
589 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
590 or arrays as values.</li>
591 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
592 <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>
593 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
594 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
595 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
596 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
597 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
598 <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>
599 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
600 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
601 <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>
602 <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>
603 <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>
604 <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>
605 <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>
606 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
611 <p>If you run into GCC extensions which have not been included in any of these
612 lists, please let us know (also including whether or not they work).</p>
616 <!-- ======================================================================= -->
617 <div class="doc_subsection">
618 <a name="c++-fe">Known problems with the C++ front-end</a>
621 <div class="doc_text">
623 <p>For this release, the C++ front-end is considered to be fully functional but
624 has not been tested as thoroughly as the C front-end. It has been tested and
625 works for a number of non-trivial programs, but there may be lurking bugs.
626 Please report any bugs or problems.</p>
630 <!-- _______________________________________________________________________ -->
631 <div class="doc_subsubsection">Bugs</div>
633 <div class="doc_text">
636 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
640 <p><b>IA64 note</b>: The C++ front-end does not use <a
641 href="http://llvm.cs.uiuc.edu/PR406">IA64 ABI compliant layout of vtables</a>.
642 In particular, it just stores function pointers instead of function
643 descriptors in the vtable. This bug prevents mixing C++ code compiled with
644 LLVM with C++ objects compiled by other C++ compilers.</p>
648 <!-- _______________________________________________________________________ -->
649 <div class="doc_subsubsection">
653 <div class="doc_text">
657 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
658 parser is significantly more standards compliant (and picky) than prior GCC
659 versions. For more information, see the C++ section of the <a
660 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
662 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
663 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
664 function and in the <tt>setjmp</tt> receiver function may not be run.
665 Objects in intervening stack frames will be destroyed, however (which is
666 better than most compilers).</li>
668 <li>The LLVM C++ front-end follows the <a
669 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
670 This document, which is not Itanium specific, specifies a standard for name
671 mangling, class layout, v-table layout, RTTI formats, and other C++
672 representation issues. Because we use this API, code generated by the LLVM
673 compilers should be binary compatible with machine code generated by other
674 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
675 <i>However</i>, the exception handling mechanism used by LLVM is very
676 different from the model used in the Itanium ABI, so <b>exceptions will not
677 interact correctly</b>. </li>
683 <!-- ======================================================================= -->
684 <div class="doc_subsection">
685 <a name="x86-be">Known problems with the X86 back-end</a>
688 <div class="doc_text">
691 <li>Optimized (Release) versions of LLVM built with GCC 3.3.2 or 3.3.3 will
692 produce an llc tool that always enters an infinite loop due to what
693 appears to be an optimization bug (-O2 and -O3) in those versions of GCC.
694 This problem does not happen in GCC 3.3.1 nor GCC 3.4.0 nor does it happen if
695 you build a Debug version of LLVM. You are cautioned not to use GCC 3.3.2 or
696 GCC 3.3.3 to build Optimized versions of LLVM. It is unclear whether this problem
697 affects other backends but it is unlikely.</li>
702 <!-- ======================================================================= -->
703 <div class="doc_subsection">
704 <a name="sparcv9-be">Known problems with the SparcV9 back-end</a>
707 <div class="doc_text">
710 <li><a href="http://llvm.cs.uiuc.edu/PR60">[sparcv9] SparcV9 backend miscompiles
711 several programs in the LLVM test suite</a></li>
716 <!-- ======================================================================= -->
717 <div class="doc_subsection">
718 <a name="c-be">Known problems with the C back-end</a>
721 <div class="doc_text">
725 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
726 Analysis rules. As such, special options may be necessary to compile the code
727 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
728 problem probably cannot be fixed.</li>
730 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
731 cannot include special floating point numbers like Not-A-Number or
734 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
735 supported</a>. This should not affect LLVM produced by the C or C++
742 <!-- *********************************************************************** -->
743 <div class="doc_section">
744 <a name="additionalinfo">Additional Information</a>
746 <!-- *********************************************************************** -->
748 <div class="doc_text">
750 <p>A wide variety of additional information is available on the LLVM web page,
751 including mailing lists and publications describing algorithms and components
752 implemented in LLVM. The web page also contains versions of the API
753 documentation which is up-to-date with the CVS version of the source code. You
754 can access versions of these documents specific to this release by going into
755 the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
757 <p>If you have any questions or comments about LLVM, please feel free to contact
758 us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
763 <!-- *********************************************************************** -->
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