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6 <title>LLVM 1.1 Release Notes</title>
10 <div class="doc_title">
11 LLVM 1.1 Release Notes
15 <li><a href="#intro">Introduction</a></li>
16 <li><a href="#whatsnew">What's New?</a></li>
17 <li><a href="#portability">Portability and Supported Platforms</a></li>
18 <li><a href="#install-instructions">Installation Instructions</a></li>
19 <li><a href="#knownproblems">Known Problems</a>
21 <!-- <li><a href="#portabilityprobs">Portability Problems</a> -->
22 <li><a href="#core">Known problems with the LLVM Core</a>
23 <li><a href="#c-fe">Known problems with the C Front-end</a>
24 <li><a href="#c++-fe">Known problems with the C++ Front-end</a>
25 <li><a href="#x86-be">Known problems with the X86 Back-end</a>
26 <li><a href="#sparc-be">Known problems with the Sparc Back-end</a>
27 <li><a href="#c-be">Known problems with the C back-end</a>
29 <li><a href="#additionalinfo">Additional Information</a></li>
32 <div class="doc_text">
33 <p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
36 <!-- *********************************************************************** -->
37 <div class="doc_section">
38 <a name="intro">Introduction</a>
40 <!-- *********************************************************************** -->
42 <div class="doc_text">
44 <p>This document contains the release notes for the LLVM compiler
45 infrastructure, release 1.1. Here we describe the status of LLVM, including any
46 known problems, and bug fixes from the previous release. The most up-to-date
47 version of this document can be found on the <a
48 href="http://llvm.cs.uiuc.edu/releases/1.1/">LLVM 1.1 web site</a>. If you are
49 not reading this on the LLVM web pages, you should probably go there, because
50 this document may be updated after the release.</p>
52 <p>For more information about LLVM, including information about potentially more
53 current releases, please check out the <a href="http://llvm.cs.uiuc.edu">main
54 web site</a>. If you have questions or comments, the <a
55 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
56 list</a> is a good place to send them.</p>
58 <p>Note that if you are reading this file from CVS, this document applies
59 to the <i>next</i> release, not the current one. To see the release notes for
60 the current or previous releases, see the <a
61 href="http://llvm.cs.uiuc.edu/releases/">releases page</a>.</p>
65 <!-- *********************************************************************** -->
66 <div class="doc_section">
67 <a name="whatsnew">What's New?</a>
69 <!-- *********************************************************************** -->
71 <div class="doc_text">
73 <p>This is the second public release of the LLVM compiler infrastructure. This
74 release is primarily a bugfix release, dramatically improving the C/C++
75 front-end, and improving support for C++ in the LLVM core. This release also
76 includes a few new features, such as a simple profiler, support for Mac OS/X,
77 better interoperability with external source bases, a new example language
78 front-end, and improvements in a few optimizations.</p>
80 <p>At this time, LLVM is known to correctly compile the C & C++ SPEC CPU2000
81 benchmarks with the C backend (X86 only), the Olden benchmarks, and the Ptrdist
82 benchmarks. It has also been used to compile
83 <b>many</b> other programs. LLVM now also works with a broad variety of
84 C++ programs, though it has still received much less testing than the C
89 Note that the Sparc and X86 backends do not currently support exception throwing
90 or long jumping (including 253.perlbmk in SPEC). For these programs, you must
91 use the C backend. Support for unwinding will be added in a future release.
95 <!--=========================================================================-->
96 <div class="doc_subsubsection">
97 This release implements the following new features:
102 href="http://mail.cs.uiuc.edu/pipermail/llvmdev/2003-November/000528.html">A new
103 LLVM profiler, similar to gprof</a> is available</li>
105 <li>LLVM and the C/C++ front-end now compile on Mac OS/X! Mac OS/X users can
106 now explore the LLVM optimizer with the C backend and interpreter. Note that
107 LLVM requires GCC 3.3 on Mac OS/X.</li>
110 href="http://mail.cs.uiuc.edu/pipermail/llvmdev/2003-November/000554.html">moved
111 into an 'llvm' C++ namespace</a>, for easier integration with third-party
112 code. Note that due to lack of namespace support in GDB 5.x, you will probably
113 want to upgrade to GDB 6 or better to debug LLVM code.</li>
116 The build system now copies Makefiles dynamically from the source tree to the
117 object tree as subdirectories are built. This means that:
120 New directories can be added to the source tree, and the build will
121 automatically pick them up (i.e. no need to re-run <tt>configure</tt>).
125 You will need to build LLVM from the top of the object tree once to ensure
126 that all of the Makefiles are copied into the object tree subdirectories.
131 <li>A front-end for "Stacker" (a simple Forth-like language) is now
132 <a href="http://llvm.cs.uiuc.edu/PR136">included in the main LLVM tree</a>.
133 Additionally, Reid Spencer, the author, contributed a document <a href="Stacker.html">describing his experiences writing Stacker, and the language itself</a>. This document is invaluable for others writing front-ends targetting LLVM.</li>
135 <li>The <tt>configure</tt> script will now configure all projects placed in the
136 <tt>llvm/projects</tt> directory.</li>
138 <li>The <tt>-tailcallelim</tt> pass can now introduce "accumulator" variables
139 to transform functions in many common cases that it could not before.</li>
141 <li>The <tt>-licm</tt> pass can now sink instructions out the bottom of loops
142 in addition to being able to hoist them out the top.</li>
144 <li>The <tt>-basicaa</tt> pass (the default alias analysis) has been upgraded
145 to be <a href="http://llvm.cs.uiuc.edu/PR86">significantly more
148 <li>LLVM 1.1 implements a simple size optimization for LLVM bytecode files.
149 This means that the 1.1 files are smaller than 1.0, but that 1.0 won't
150 read 1.1 bytecode files.</li>
152 <li><a href="http://llvm.cs.uiuc.edu/PR140">The gccld program produces a runner script that includes command-line options to load the necessary shared objects.</a></li>
156 <!--=========================================================================-->
157 <div class="doc_subsubsection">
158 In this release, the following missing features were implemented:
162 <li><a href="http://llvm.cs.uiuc.edu/PR88">The interpreter does not support
163 invoke or unwind</a></li>
165 <li><a href="http://llvm.cs.uiuc.edu/PR99">Interpreter does not support the
166 <tt>vaarg</tt> instruction</a></li>
168 <li><a href="http://llvm.cs.uiuc.edu/PR117">llvm-nm cannot read archive
171 <li><a href="http://llvm.cs.uiuc.edu/PR146">Interpreter does not handle
172 setne constant expression</a></li>
176 <!--=========================================================================-->
177 <div class="doc_subsubsection">
178 In this release, the following Quality of Implementation issues were
184 <li>The C++ front-end now compiles functions to
185 <a href="http://llvm.cs.uiuc.edu/PR29">use the linkonce linkage type</a>
186 more, giving the optimizer more freedom.</a></li>
188 <li>The C front-end now <a href="http://llvm.cs.uiuc.edu/PR84">generates
189 type-safe code</a> in several cases that it did not before, which prevented
190 some important optimizations.</li>
192 <li>The LLVM build system has been taught to catch some common configuration
193 problems that <a href="http://llvm.cs.uiuc.edu/PR96">caused it to get
194 horribly confused</a> before.</li>
196 <li>The LLVM header files are now
197 <a href="http://llvm.cs.uiuc.edu/PR114">-Wold-style-cast clean</a>.</li>
199 <li>The LLVM bytecode reader has been <a
200 href="http://llvm.cs.uiuc.edu/PR127">sped up a lot</a> (up to 4x in some
203 <li>In C++, methods and functions in anonymous namespaces <a href="http://llvm.cs.uiuc.edu/PR85">now get internal linkage</a>.</li>
205 <li>Constant initializers now generate loops instead of potentially <a href="http://llvm.cs.uiuc.edu/PR75">huge amounts of straight-line code</a>.</li>
207 <li>Code for running C++ destructors is now properly shared when possible. Before, the C++ front-end
208 <a href="http://llvm.cs.uiuc.edu/PR11">generated N^2 amounts of duplicated cleanup code</a> in some cases.</li>
210 <li>The JIT used to <a href="http://llvm.cs.uiuc.edu/PR177">generate code for
211 all functions pointed to by globals</a> immediately, before the program
212 started execution, but now it waits until the first time they are called to
213 compile them. This dramatically speeds up short runs of large C++ programs,
214 which often have large numbers of functions pointed to by vtables.</li>
218 <!--=========================================================================-->
219 <div class="doc_subsubsection">
220 In this release, the following bugs in the previous release were fixed:
223 <p>Bugs in the LLVM Core:</p>
226 <li><a href="http://llvm.cs.uiuc.edu/PR57">[inliner] Inlining invoke with PHI in unwind target is broken</a></li>
227 <li><a href="http://llvm.cs.uiuc.edu/PR58">[linker] linkonce globals should link successfully to external globals</a></li>
228 <li><a href="http://llvm.cs.uiuc.edu/PR64">[constmerge] Constant merging pass merges constants with external linkage</a></li>
229 <li><a href="http://llvm.cs.uiuc.edu/PR66">[scalarrepl] Scalar Replacement of aggregates is decimating structures it shouldn't be</a></li>
230 <li><a href="http://llvm.cs.uiuc.edu/PR70">[instcombine] Resolving invoke inserts cast after terminator</a></li>
231 <li><a href="http://llvm.cs.uiuc.edu/PR71">llvm-as crashes when labels are used in phi nodes</a></li>
232 <li><a href="http://llvm.cs.uiuc.edu/PR72">[build problem] Callgraph.cpp not pulled in from libipa.a</a></li>
233 <li><a href="http://llvm.cs.uiuc.edu/PR77">Variables in scope of output setjmp
234 calls should be volatile</a> (Note that this does not effect correctness on
235 many platforms, such as X86).</li>
236 <li><a href="http://llvm.cs.uiuc.edu/PR83">[X86] Emission of global bool initializers broken</a></li>
237 <li><a href="http://llvm.cs.uiuc.edu/PR91">[gccld] The -r (relinking) option does not work correctly</a></li>
238 <li><a href="http://llvm.cs.uiuc.edu/PR92">[bcreader] Cannot read shift constant expressions from bytecode file</a></li>
239 <li><a href="http://llvm.cs.uiuc.edu/PR93">[lowersetjmp] Lowersetjmp pass breaks dominance properties!</a></li>
240 <li><a href="http://llvm.cs.uiuc.edu/PR95">SymbolTable::getUniqueName is very inefficient</a></li>
241 <li><a href="http://llvm.cs.uiuc.edu/PR97">bugpoint must not pass -R<directory> to Mach-O linker</a></li>
242 <li><a href="http://llvm.cs.uiuc.edu/PR98">[buildscripts] Building into objdir with .o in it fails</a></li>
243 <li><a href="http://llvm.cs.uiuc.edu/PR101">[setjmp/longjmp] Linking C programs which use setjmp/longjmp sometimes fail with references to the C++ runtime library!</a></li>
244 <li><a href="http://llvm.cs.uiuc.edu/PR107">AsmParser Misses Symbol Redefinition Error</a></li>
245 <li><a href="http://llvm.cs.uiuc.edu/PR108">gccld -Lfoo -lfoo fails to find ./foo/libfoo.a</a></li>
246 <li><a href="http://llvm.cs.uiuc.edu/PR110">[bcreader] Incorrect cast causes misread forward constant references</a></li>
247 <li><a href="http://llvm.cs.uiuc.edu/PR116">[adce] ADCE considers blocks without postdominators to be unreachable</a></li>
248 <li><a href="http://llvm.cs.uiuc.edu/PR123">[X86] div and rem constant exprs invalidate iterators!</a></li>
249 <li><a href="http://llvm.cs.uiuc.edu/PR130">[vmcore] Symbol table doesn't rename colliding variables during type resolution</a></li>
250 <li><a href="http://llvm.cs.uiuc.edu/PR138">Archive reader does not understand 4.4BSD/Mac OS X long filenames</a></li>
251 <li><a href="http://llvm.cs.uiuc.edu/PR30">[llvm-ar] Command line arguments have funny syntax</a></li>
255 <p>Bugs in the C/C++ front-end:</p>
258 <li><a href="http://llvm.cs.uiuc.edu/PR59">C++ frontend can crash when compiling virtual base classes</a></li>
259 <li><a href="http://llvm.cs.uiuc.edu/PR62">C backend fails on constant cast expr to ptr-to-anonymous struct</a></li>
260 <li><a href="http://llvm.cs.uiuc.edu/PR63">#ident is not recognized by C frontend</a></li>
261 <li><a href="http://llvm.cs.uiuc.edu/PR65">C front-end miscompiles the builtin_expect intrinsic!</a></li>
262 <li><a href="http://llvm.cs.uiuc.edu/PR67">1.0 precompiled libstdc++ does not include wchar_t support</a></li>
263 <li><a href="http://llvm.cs.uiuc.edu/PR68">llvmgcc asserts when compiling functions renamed with asm's</a></li>
264 <li><a href="http://llvm.cs.uiuc.edu/PR69">C frontend crashes on some programs with lots of types.</a></li>
265 <li><a href="http://llvm.cs.uiuc.edu/PR79">llvm-gcc crashes compiling global union initializer</a></li>
266 <li><a href="http://llvm.cs.uiuc.edu/PR80">C front-end crash on empty structure</a></li>
267 <li><a href="http://llvm.cs.uiuc.edu/PR81">CFrontend crashes when compiling C99 compound expressions</a></li>
268 <li><a href="http://llvm.cs.uiuc.edu/PR87">llvm-gcc infinite loops on "case MAXINT:"</a></li>
269 <li><a href="http://llvm.cs.uiuc.edu/PR89">[C++] Catch blocks make unparsable labels</a></li>
270 <li><a href="http://llvm.cs.uiuc.edu/PR90">[C++] Initializing array with constructable objects fail</a></li>
271 <li><a href="http://llvm.cs.uiuc.edu/PR94">llvm-gcc tries to add bools</a></li>
272 <li><a href="http://llvm.cs.uiuc.edu/PR104">[c++] C++ Frontend lays out superclasses like anonymous bitfields!</a></li>
273 <li><a href="http://llvm.cs.uiuc.edu/PR54">C front-end miscompiles unsigned enums whose LLVM types are signed</a></li>
274 <li><a href="http://llvm.cs.uiuc.edu/PR112">Casting a string constant to void crashes llvm-gcc</a></li>
275 <li><a href="http://llvm.cs.uiuc.edu/PR125">[llvmg++] Enum types are incorrectly shrunk to smaller than 'int' size</a></li>
276 <li><a href="http://llvm.cs.uiuc.edu/PR128">[llvmg++] Cannot use pointer to member to initialize global</a></li>
277 <li><a href="http://llvm.cs.uiuc.edu/PR131">[llvm-gcc] ?: operator as lvalue not implemented</a></li>
278 <li><a href="http://llvm.cs.uiuc.edu/PR133">[C/C++] Bogus warning about taking the address of 'register' variable</a></li>
279 <li><a href="http://llvm.cs.uiuc.edu/PR113">crash assigning into an array in a struct which contains a bitfield</a>.</li>
280 <li><a href="http://llvm.cs.uiuc.edu/PR6">Oversized integer bitfields cause crash</a></li>
281 <li><a href="http://llvm.cs.uiuc.edu/PR141">[llvm-gcc] Bitfields & large array don't mix well</a></li>
282 <li><a href="http://llvm.cs.uiuc.edu/PR132">[llvm-gcc] Complex division is not supported</a></li>
283 <li><a href="http://llvm.cs.uiuc.edu/PR143">[llvm-gcc] Illegal union field reference</a></li>
284 <li><a href="http://llvm.cs.uiuc.edu/PR148">[llvmg++] Front-end attempts to return structure by value</a></li>
285 <li><a href="http://llvm.cs.uiuc.edu/PR152">[llvmg++] Pointer to member initializers not supported in constructors</a></li>
286 <li><a href="http://llvm.cs.uiuc.edu/PR155">[llvm-gcc] crash on union initialization</a></li>
287 <li><a href="http://llvm.cs.uiuc.edu/PR124">[llvm-g++] ?: expressions do not run correct number of destructors!</a></li>
288 <li><a href="http://llvm.cs.uiuc.edu/PR157">[llvm-gcc] Pointer & constant results in invalid shift</a></li>
289 <li><a href="http://llvm.cs.uiuc.edu/PR165">[llvmg++] call through array of pointers to member functions causes assertion</a></li>
294 <!-- *********************************************************************** -->
295 <div class="doc_section">
296 <a name="portability">Portability and Supported Platforms</a>
298 <!-- *********************************************************************** -->
300 <div class="doc_text">
302 <p>LLVM has been extensively tested on Intel and AMD machines running Red
303 Hat Linux and has been tested on Sun UltraSPARC workstations running Solaris 8.
305 LLVM works on Mac OS/X 10.3 and above, but only with the C backend or
306 interpreter (no native backend for the PowerPC is available yet).
307 The core LLVM infrastructure uses "autoconf" for portability, so hopefully we
308 work on more platforms than that. However, it is likely that we
309 missed something, and that minor porting is required to get LLVM to work on
310 new platforms. We welcome portability patches and error messages.</p>
314 <!-- *********************************************************************** -->
315 <div class="doc_section">
316 <a name="knownproblems">Known Problems</a>
318 <!-- *********************************************************************** -->
320 <div class="doc_text">
322 <p>This section contains all known problems with the LLVM system, listed by
323 component. As new problems are discovered, they will be added to these
324 sections. If you run into a problem, please check the <a
325 href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a>, and submit a bug if
326 there isn't already one.</p>
330 <!-- _______________________________________________________________________ -->
332 </ul><h4><a name="portability"><hr size=0>Portability Problems</h4><ul>
336 <!-- ======================================================================= -->
337 <div class="doc_subsection">
338 <a name="core">Known problems with the LLVM Core</a>
341 <div class="doc_text">
345 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
348 <li>The JIT does not use mutexes to protect its internal data structures. As
349 such, execution of a threaded program could cause these data structures to be
352 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
354 <li>Linking in static archive files (.a files) is very slow (there is no symbol
355 table in the archive).</li>
357 <li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
358 more than 256 elements</a>.</li>
364 <!-- ======================================================================= -->
365 <div class="doc_subsection">
366 <a name="c-fe">Known problems with the C front-end</a>
369 <!-- _______________________________________________________________________ -->
370 <div class="doc_subsubsection">
374 <div class="doc_text">
378 <li>C99 Variable sized arrays do not release stack memory when they go out of
379 scope. Thus, the following program may run out of stack space:
381 for (i = 0; i != 1000000; ++i) {
391 <!-- _______________________________________________________________________ -->
392 <div class="doc_subsubsection">
396 <div class="doc_text">
400 <li>Inline assembly is not yet supported.</li>
402 <li>"long double" is transformed by the front-end into "double". There is no
403 support for floating point data types of any size other than 32 and 64
406 <li>The following Unix system functionality has not been tested and may not
409 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
410 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
411 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
412 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
413 - These functions have not been tested.
416 <li>Although many GCC extensions are supported, some are not. In particular,
417 the following extensions are known to <b>not be</b> supported:
419 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
420 <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>
421 <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>
422 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
423 <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>
424 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands</li>
425 <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>
426 <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>
427 <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>
428 <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>
429 <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>
430 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
431 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
434 <p>The following GCC extensions are <b>partially</b> supported. An ignored
435 attribute means that the LLVM compiler ignores the presence of the attribute,
436 but the code should still work. An unsupported attribute is one which is
437 ignored by the LLVM compiler, which will cause a different interpretation of
441 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
442 Arrays whose length is computed at run time.<br>
443 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
445 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
447 Declaring that functions have no side effects, or that they can never
450 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
451 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
452 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
454 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
455 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
456 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
458 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
459 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
460 <tt>fastcall</tt>, all other target specific attributes</li>
462 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
463 Specifying attributes of variables.<br>
464 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
465 <tt>deprecated</tt>, <tt>transparent_union</tt>,
466 <tt>unused</tt>, <tt>weak</tt><br>
468 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
469 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
470 <tt>vector_size</tt>, <tt>dllimport</tt>,
471 <tt>dllexport</tt>, all target specific attributes.</li>
473 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
474 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
475 <tt>deprecated</tt>, <tt>may_alias</tt><br>
477 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
478 all target specific attributes.</li>
480 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
481 Other built-in functions.<br>
482 We support all builtins which have a C language equivalent (e.g.,
483 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
484 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
485 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> (ignored).</li>
489 <p>The following extensions <b>are</b> known to be supported:</p>
492 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
493 <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>
494 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
495 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
496 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
497 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
498 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
499 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
500 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
501 <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>
502 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
503 <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>
504 <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>
505 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
506 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions or arrays as values.</li>
507 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
508 <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>
509 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
510 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
511 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
512 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
513 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
514 <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>
515 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
516 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
517 <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>
518 <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>
519 <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>
520 <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>
521 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
526 <p>If you run into GCC extensions which have not been included in any of these
527 lists, please let us know (also including whether or not they work).</p>
531 <!-- ======================================================================= -->
532 <div class="doc_subsection">
533 <a name="c++-fe">Known problems with the C++ front-end</a>
536 <div class="doc_text">
538 <p>For this release, the C++ front-end is considered to be fully functional, but
539 has not been tested as thoroughly as the C front-end. It has been tested and
540 works for a number of non-trivial programs, but there may be lurking bugs.
541 Please report any bugs or problems.</p>
545 <!-- _______________________________________________________________________ -->
546 <div class="doc_subsubsection">
550 <div class="doc_text">
553 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
559 <!-- _______________________________________________________________________ -->
560 <div class="doc_subsubsection">
564 <div class="doc_text">
568 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
569 parser is significantly more standards compliant (and picky) than prior GCC
570 versions. For more information, see the C++ section of the <a
571 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
573 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
574 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
575 function and in the <tt>setjmp</tt> receiver function may not be run.
576 Objects in intervening stack frames will be destroyed however (which is
577 better than most compilers).</li>
579 <li>The LLVM C++ front-end follows the <a
580 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
581 This document, which is not Itanium specific, specifies a standard for name
582 mangling, class layout, v-table layout, RTTI formats, and other C++
583 representation issues. Because we use this API, code generated by the LLVM
584 compilers should be binary compatible with machine code generated by other
585 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
586 <i>However</i>, the exception handling mechanism used by LLVM is very
587 different from the model used in the Itanium ABI, so <b>exceptions will not
588 interact correctly</b>. </li>
594 <!-- ======================================================================= -->
595 <div class="doc_subsection">
596 <a name="x86-be">Known problems with the X86 back-end</a>
599 <div class="doc_text">
603 <li>The X86 code generator <a
604 href="http://llvm.cs.uiuc.edu/PR16">does not currently
605 support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
606 or calls the C <tt>longjmp</tt> function will abort.</li>
612 <!-- ======================================================================= -->
613 <div class="doc_subsection">
614 <a name="sparc-be">Known problems with the Sparc back-end</a>
617 <div class="doc_text">
621 <li>The Sparc code generator <a
622 href="http://llvm.cs.uiuc.edu/PR15">does not currently
623 support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
624 or calls the C <tt>longjmp</tt> function will abort.</li>
630 <!-- ======================================================================= -->
631 <div class="doc_subsection">
632 <a name="c-be">Known problems with the C back-end</a>
635 <div class="doc_text">
639 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
640 Analysis rules. As such, special options may be necessary to compile the code
641 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
642 problem probably cannot be fixed.</li>
644 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
645 cannot include special floating point numbers like Not-A-Number or
648 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
649 supported</a>. This should not affect LLVM produced by the C or C++
656 <!-- *********************************************************************** -->
657 <div class="doc_section">
658 <a name="additionalinfo">Additional Information</a>
660 <!-- *********************************************************************** -->
662 <div class="doc_text">
664 <p>A wide variety of additional information is available on the LLVM web page,
665 including mailing lists publications describing algorithms and components
666 implemented in LLVM. The web page also contains versions of the API
667 documentation which is up-to-date with the CVS version of the source code. You
668 can access versions of these documents specific to this release by going into
669 the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
671 <p>If you have any questions or comments about LLVM, please feel free to contact
672 us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
677 <!-- *********************************************************************** -->
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