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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, adds many <a
75 href="#newfeatures">new features</a>, <a href="#bugfix">fixes a few
76 bugs</a>, speeds up the compiler, and introduces a new (experimental)
77 PowerPC code generator.</p>
79 <p> At this time, LLVM is known to correctly compile and run all C & C++
80 SPEC CPU95 & 2000 benchmarks, the Olden benchmarks, and the Ptrdist
81 benchmarks, and <b>many</b> other programs. LLVM now also works
82 with a broad variety of C++ programs.</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>).</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 a simple implementation of <a
112 href="AliasAnalysis.html#anders-aa">Andersen's interprocedural alias
113 analysis</a> algorithm.</li>
114 <li>Bugpoint can <a href="http://llvm.cs.uiuc.edu/PR327">extract individual
115 basic blocks</a> to track down reduce miscompilation testcases.</li>
116 <li>LLVM and the C front-end now work under Win32 using the
117 <a href="http://www.cygwin.com">Cygwin</a> runtime libraries.
118 This includes the JIT compiler.</li>
119 <li>The LLVM code generator is now being <a
120 href="CodeGenerator.html">documented</a>.</li>
121 <li>LLVM includes a new tool, <a
122 href="CommandGuide/html/llvm-bcanalyzer.html">llvm-bcanalyzer</a>, This tool
123 can compute various statistics and dump information about LLVM bytecode
125 <li>The <a href="BytecodeFormat.html">LLVM bytecode file format</a> is now
127 <li>LLVM now provides an <a
128 href="LangRef.html#i_isunordered">llvm.isunordered</a> intrinsic for efficient
129 implementation of unordered floating point comparisons.</li>
130 <li>The llvmgcc front-end now supports the GCC builtins for ISO C99 floating
131 point comparison macros (e.g., <tt>__builtin_islessequal</tt>).</li>
132 <li>We now generate <a href="CommandGuide/">HTML documentation and man pages</a>
133 for the tools from a single source (perl-style POD files).</li>
134 <li>The LLVM code generator can now dynamically load targets from shared
136 <li>LLVM now includes a "skeleton" target, which makes it easier to get
137 started porting LLVM to new architectures.</li>
138 <li>The linear scan register allocator is now enabled by default in the
139 target-independent code generator.</li>
140 <li>LLVM now includes a dead store elimination pass.</li>
141 <li>Bugpoint can now debug miscompilations that lead to the program going
142 into an infinite loop.</li>
143 <li>LLVM now provides interfaces to support ML-style pattern matching on the
145 <li>LLVM now includes a <a
146 href="AliasAnalysis.html#globalsmodref">context-sensitive mod/ref analysis</a>
147 for global variables, which is now enabled by default in gccld.</li>
148 <li>LLVM can now autogenerate assembly printers for code generators from the
149 tablegen description of the target (before they were hand coded).</li>
150 <li>All LLVM tools will now respond to the
151 <a href="http://llvm.cs.uiuc.edu/PR413"><tt>--version</tt> option</a> which
152 will tell you the version of LLVM on which the tool is based.</li>
153 <li>An experimental PowerPC backend has been added, capable of compiling several
154 SPEC benchmarks.</li>
160 <!--=========================================================================-->
161 <div class="doc_subsubsection">
162 In this release, the following missing features were implemented:
165 <div class="doc_text">
168 <li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
169 more than 256 elements</a></li>
170 <li><a href="http://llvm.cs.uiuc.edu/PR38">[bugpoint] External functions used in
171 non-instruction entities, such as global constant initializer</a></li>
172 <li><a href="http://llvm.cs.uiuc.edu/PR178">Stacker does not handle targets
173 with 64-bit pointers.</a></li>
174 <li><a href="http://llvm.cs.uiuc.edu/PR290">Bugpoint doesn't support
175 uses of external fns by immediate constant exprs</a></li>
176 <li><a href="http://llvm.cs.uiuc.edu/PR407">Can't add function passes that
177 depend on immutable passes to the FunctionPassManager</a>.</li>
178 <li><a href="http://llvm.cs.uiuc.edu/PR308">Archive file reader doesn't
179 understand abbreviated names in headers</a></li>
184 <!--=========================================================================-->
185 <div class="doc_subsubsection">
186 <a name="qualityofimp">In this release, the following Quality of Implementation
187 issues were fixed:</a>
190 <div class="doc_text">
193 <li><a href="http://llvm.cs.uiuc.edu/PR305">LLVM tools will happily spew
194 bytecode onto your terminal</a></li>
195 <li><a href="http://llvm.cs.uiuc.edu/PR329">[llvmgcc] type names are not emitted
196 for structure typedefs</a></li>
197 <li>All documentation is now conformant to the HTML 4.01 (Strict) level.</li>
198 <li>The spurious "WARNING: Found global types that are not compatible" warning
199 produced when linking C++ programs has been fixed.</li>
200 <li><a href="http://llvm.cs.uiuc.edu/PR391">lli Doesn't Handle Exceptions From
201 Bytecode Reader</a></li>
202 <li><a href="http://llvm.cs.uiuc.edu/PR392">Global Vars Have (Somewhat) Limited
204 <li><a href="http://llvm.cs.uiuc.edu/PR341">operator<< on a Value* now
205 prints the address of the object instead of its contents.</a></li>
206 <li><a href="http://llvm.cs.uiuc.edu/PR402">Bytecode Enhancements
208 <li><a href="http://llvm.cs.uiuc.edu/PR404">[loopsimplify] Loop simplify is
209 really slow on 252.eon</a></li>
210 <li><a href="Http://llvm.cs.uiuc.edu/PR122">[code-cleanup] SymbolTable class
211 cleanup, Type should not derive from Value, eliminate ConstantPointerRef
213 <li>The memory footprint of the LLVM IR has been reduced substantially.</li>
214 <li>The LLVM linker and many core classes have been sped up substantially.</li>
219 <!--=========================================================================-->
220 <div class="doc_subsubsection">
221 In this release, the following build problems were fixed:
224 <div class="doc_text">
226 <li><a href="http://llvm.cs.uiuc.edu/PR301">Minor configure bugs with
227 -disable/enable-povray and -disable-spec</a></li>
228 <li><a href="http://llvm.cs.uiuc.edu/PR289">shell scripts output by gccld don't
229 work if you change PATH</a></li>
230 <li><a href="http://llvm.cs.uiuc.edu/PR364">[llvmgcc] llvmgcc does not compile
231 with gcc 3.4</a></li>
232 <li><a href="http://llvm.cs.uiuc.edu/PR373">[llvmgcc] obstack.h relies on
233 obsolete casts-as-lvalues GCC extension</a></li>
237 <!--=========================================================================-->
238 <div class="doc_subsubsection">
239 <a name="codequality">This release includes the following Code Quality
243 <div class="doc_text">
245 <li>Fixed: <a href="http://llvm.cs.uiuc.edu/PR309">[vmcore] Code quality problem
246 due to long operand of getelementptr</a></li>
248 <li>The X86 backend now generates substantially better code for 64-bit integer
249 and floating point operations.</li>
251 <li>The -inline pass no longer inlines mutually recursive functions until it
252 hits the inlining threshold.</li>
254 <li>The -inline pass no longer misses obvious inlining opportunities just
255 because the callee eventually calls into an external function.</li>
257 <li>The -simplifycfg pass can now "if convert" simple statements into the
258 <tt>select</tt> instruction.</li>
260 <li>The -loopsimplify pass can now break <a
261 href="http://llvm.cs.uiuc.edu/PR35">natural loops with multiple backedges</a>
262 into multiple nested loops. This enables a variety of subsequent
265 <li>The -adce pass can now eliminate calls to functions that do not not write to
268 <li>The link-time optimizer now runs the -prune-eh pass (to remove unused
269 exception handlers).</li>
271 <li>The link-time optimizer now runs dead store elimination and uses a simple
272 interprocedural alias analysis.</li>
274 <li>The -simplifycfg pass can now eliminate simple correlated branches (such as
275 "<tt>if (A < B && A < B)</tt>", and can turn short-circuiting
276 operators into the strict versions when useful (such as "<tt>if (A < B || A
277 > C)</tt>" into "<tt>if (A < B | A > C)</tt>"</li>
279 <li>LLVM now has infrastructure for (simple and sparse conditional) constant
280 propagation of function calls. It currently supports a few math library
281 functions like sqrt/sin/cos/etc.</li>
283 <li>The C backend now emits <a href="http://llvm.cs.uiuc.edu/PR334">syntactic
284 loops</a> in the code to help C compilers whose optimizers do not recognize
285 loops formed from gotos (like GCC).</li>
287 <li>The SparcV9 backend no longers <a
288 href="http://llvm.cs.uiuc.edu/PR368">spills the null constant to the constant
293 <!--=========================================================================-->
294 <div class="doc_subsubsection">
295 <a name="bugfix">In this release, the following bugs in the previous release
299 <div class="doc_text">
301 <p>Bugs fixed in the LLVM Core:</p>
304 <li><a href="http://llvm.cs.uiuc.edu/PR306">[loopsimplify] Loop simplify
305 incorrectly updates dominator information</a></li>
306 <li><a href="http://llvm.cs.uiuc.edu/PR310">[tailduplicate] DemoteRegToStack
307 breaks SSA form</a></li>
308 <li><a href="http://llvm.cs.uiuc.edu/PR313">[X86] JIT miscompiles unsigned short
309 to floating point cast</a></li>
310 <li><a href="http://llvm.cs.uiuc.edu/PR330">[vmcore] Linker causes erroneous
312 <li><a href="http://llvm.cs.uiuc.edu/PR332">[adce] Crash handling unreachable
313 code that unwinds</a></li>
314 <li><a href="http://llvm.cs.uiuc.edu/PR333">[sparcv9] LLC can't emit 2 functions
315 of the same name, both having constant pools</a></li>
316 <li><a href="http://llvm.cs.uiuc.edu/PR337">[livevar] Live variables missed
317 physical register use of aliased definition</a></li>
318 <li><a href="http://llvm.cs.uiuc.edu/PR369">[X86] stackifier crash on floating
319 point setcc X, X</a></li>
322 <p>Bugs in the C/C++ front-end:</p>
325 <li><a href="http://llvm.cs.uiuc.edu/PR298">[llvmgcc] Variable length array
326 indexing miscompiled</a></li>
327 <li><a href="http://llvm.cs.uiuc.edu/PR326">[llvmgcc] Crash on use of undeclared
329 <li><a href="http://llvm.cs.uiuc.edu/PR355">[llvmgcc] Errors handling function
330 prototypes that take opaque structs by-value</a></li>
331 <li><a href="http://llvm.cs.uiuc.edu/PR374">[llvmgcc] Crash compiling variable
332 length array of structures</a></li>
333 <li><a href="http://llvm.cs.uiuc.edu/PR377">[llvmgcc] miscompilation of staticly
334 initialized unsigned bitfields</a></li>
335 <li><a href="http://llvm.cs.uiuc.edu/PR396">[llvm-gcc] Crash casting function to void</a></li>
339 <!-- *********************************************************************** -->
340 <div class="doc_section">
341 <a name="portability">Portability and Supported Platforms</a>
343 <!-- *********************************************************************** -->
345 <div class="doc_text">
347 <p>LLVM is known to work in the following platforms:</p>
350 <li>Intel and AMD machines running Red Hat Linux and FreeBSD (and probably
351 other unix-like systems).</li>
352 <li>Sun UltraSPARC workstations running Solaris 8.</li>
353 <li>Intel and AMD machines running on Win32 with the Cygwin libraries.</li>
354 <li>PowerPC-based Mac OS X boxes, running 10.2 and above. Note that no JIT
355 support is available yet, and LLC support is beta. The C backend can be used
356 to produce stable code for this platform.</li>
359 <p>The core LLVM infrastructure uses
360 <a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
361 to the machine and operating system on which it is built. However, minor
362 porting may be required to get LLVM to work on new platforms. We welcome your
363 portability patches and reports of successful builds or error messages.</p>
365 <p>Note that the LLVM build system does not currently support directories with
366 spaces on them when running on Win32/cygwin. We strongly recommend running
367 LLVM and the C frontend out of a top-level directory without spaces (e.g.,
368 <tt>/cygdrive/c/llvm</tt>). Also, make sure to install <b>all</b> of the
369 cygwin packages. By default, many important tools are not installed that
370 are needed by the LLVM build process or test suite (e.g., /bin/time).</p>
374 <!-- *********************************************************************** -->
375 <div class="doc_section">
376 <a name="knownproblems">Known Problems</a>
378 <!-- *********************************************************************** -->
380 <div class="doc_text">
382 <p>This section contains all known problems with the LLVM system, listed by
383 component. As new problems are discovered, they will be added to these
384 sections. If you run into a problem, please check the <a
385 href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
386 there isn't already one.</p>
390 <!-- ======================================================================= -->
391 <div class="doc_subsection">
392 <a name="experimental">Experimental features included with this release</a>
395 <div class="doc_text">
397 <p>The following components of this LLVM release are either untested, known to
398 be broken or unreliable, or are in early development. These components should
399 not be relied on, and bugs should not be filed against them, but they may be
400 useful to some people. In particular, if you would like to work on one of these
401 components, please contact us on the llvmdev list.</p>
404 <li>The PowerPC backend is incomplete and is known to miscompile several SPEC
405 benchmarks. The file <tt>llvm/lib/Target/PowerPC/README.txt</tt> has
407 <li>The following passes are incomplete or buggy: <tt>-pgmdep, -memdep,
408 -ipmodref, -cee</tt></li>
409 <li>The <tt>-pre</tt> pass is incomplete (there are cases it doesn't handle that
410 it should) and not thoroughly tested.</li>
411 <li>The <tt>llvm-ar</tt> tool is incomplete and probably buggy.</li>
412 <li>The <tt>llvm-db</tt> tool is in a very early stage of development.</li>
417 <!-- ======================================================================= -->
418 <div class="doc_subsection">
419 <a name="core">Known problems with the LLVM Core</a>
422 <div class="doc_text">
426 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
429 <li>The JIT does not use mutexes to protect its internal data structures. As
430 such, execution of a threaded program could cause these data structures to be
433 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
435 <li>Linking in static archive files (.a files) is very slow (there is no symbol
436 table in the archive).</li>
438 <li>The gccld program <a href="http://llvm.cs.uiuc.edu/PR139">does not link
439 objects/archives in the order specified on the command line.</a></li>
441 <li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not mark
442 values live across a setjmp as volatile</a>. This missing feature only affects
443 targets whose setjmp/longjmp libraries do not save and restore the entire
448 <!-- ======================================================================= -->
449 <div class="doc_subsection">
450 <a name="c-fe">Known problems with the C front-end</a>
453 <!-- _______________________________________________________________________ -->
454 <div class="doc_subsubsection">Bugs</div>
456 <div class="doc_text">
458 <li>C99 Variable sized arrays do not release stack memory when they go out of
459 scope. Thus, the following program may run out of stack space:
461 for (i = 0; i != 1000000; ++i) {
467 <li>Initialization of global union variables can only be done <a
468 href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=162">with the largest union
471 <li><a href="http://llvm.cs.uiuc.edu/PR244">[llvm-gcc] Error when an implicitly
472 external function is re-declared as static</a></li>
477 <!-- _______________________________________________________________________ -->
478 <div class="doc_subsubsection">
482 <div class="doc_text">
486 <li>Inline assembly is not yet supported.</li>
488 <li>"long double" is transformed by the front-end into "double". There is no
489 support for floating point data types of any size other than 32 and 64
492 <li>The following Unix system functionality has not been tested and may not
495 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
496 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
497 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
498 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
499 - These functions have not been tested.
502 <li>Although many GCC extensions are supported, some are not. In particular,
503 the following extensions are known to <b>not be</b> supported:
505 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
506 <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>
507 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
508 <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>
509 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
510 <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>
511 <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>
512 <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>
513 <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>
514 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
515 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
518 <p>The following GCC extensions are <b>partially</b> supported. An ignored
519 attribute means that the LLVM compiler ignores the presence of the attribute,
520 but the code should still work. An unsupported attribute is one which is
521 ignored by the LLVM compiler and will cause a different interpretation of
525 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
526 Arrays whose length is computed at run time.<br>
527 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
529 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
531 Declaring that functions have no side effects or that they can never
534 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
535 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
536 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
538 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
539 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
540 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
542 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
543 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
544 <tt>fastcall</tt>, all other target specific attributes</li>
546 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
547 Specifying attributes of variables.<br>
548 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
549 <tt>deprecated</tt>, <tt>transparent_union</tt>,
550 <tt>unused</tt>, <tt>weak</tt><br>
552 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
553 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
554 <tt>vector_size</tt>, <tt>dllimport</tt>,
555 <tt>dllexport</tt>, all target specific attributes.</li>
557 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
558 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
559 <tt>deprecated</tt>, <tt>may_alias</tt><br>
561 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
562 all target specific attributes.</li>
564 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
565 Other built-in functions.<br>
566 We support all builtins which have a C language equivalent (e.g.,
567 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
568 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
569 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt>
570 (currently ignored). We also support builtins for ISO C99 floating
571 point comparison macros (e.g., <tt>__builtin_islessequal</tt>).</li>
574 <p>The following extensions <b>are</b> known to be supported:</p>
577 <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>
578 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
579 <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>
580 <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>
581 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
582 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
583 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
584 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
585 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
586 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
587 <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>
588 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
589 <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>
590 <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>
591 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
592 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
593 or arrays as values.</li>
594 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
595 <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>
596 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
597 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
598 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
599 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
600 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
601 <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>
602 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
603 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
604 <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>
605 <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>
606 <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>
607 <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>
608 <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>
609 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
614 <p>If you run into GCC extensions which have not been included in any of these
615 lists, please let us know (also including whether or not they work).</p>
619 <!-- ======================================================================= -->
620 <div class="doc_subsection">
621 <a name="c++-fe">Known problems with the C++ front-end</a>
624 <div class="doc_text">
626 <p>For this release, the C++ front-end is considered to be fully functional but
627 has not been tested as thoroughly as the C front-end. It has been tested and
628 works for a number of non-trivial programs, but there may be lurking bugs.
629 Please report any bugs or problems.</p>
633 <!-- _______________________________________________________________________ -->
634 <div class="doc_subsubsection">Bugs</div>
636 <div class="doc_text">
639 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
642 <li><b>IA-64 specific</b>: The C++ front-end does not use <a
643 href="http://llvm.cs.uiuc.edu/PR406">IA64 ABI compliant layout of v-tables</a>.
644 In particular, it just stores function pointers instead of function
645 descriptors in the vtable. This bug prevents mixing C++ code compiled with
646 LLVM with C++ objects compiled by other C++ compilers.</li>
652 <!-- _______________________________________________________________________ -->
653 <div class="doc_subsubsection">
657 <div class="doc_text">
661 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
662 parser is significantly more standards compliant (and picky) than prior GCC
663 versions. For more information, see the C++ section of the <a
664 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
666 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
667 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
668 function and in the <tt>setjmp</tt> receiver function may not be run.
669 Objects in intervening stack frames will be destroyed, however (which is
670 better than most compilers).</li>
672 <li>The LLVM C++ front-end follows the <a
673 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
674 This document, which is not Itanium specific, specifies a standard for name
675 mangling, class layout, v-table layout, RTTI formats, and other C++
676 representation issues. Because we use this API, code generated by the LLVM
677 compilers should be binary compatible with machine code generated by other
678 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
679 <i>However</i>, the exception handling mechanism used by LLVM is very
680 different from the model used in the Itanium ABI, so <b>exceptions will not
681 interact correctly</b>. </li>
687 <!-- ======================================================================= -->
688 <div class="doc_subsection">
689 <a name="x86-be">Known problems with the X86 back-end</a>
692 <div class="doc_text">
700 <!-- ======================================================================= -->
701 <div class="doc_subsection">
702 <a name="sparcv9-be">Known problems with the SparcV9 back-end</a>
705 <div class="doc_text">
708 <li><a href="http://llvm.cs.uiuc.edu/PR60">[sparcv9] SparcV9 backend miscompiles
709 several programs in the LLVM test suite</a></li>
714 <!-- ======================================================================= -->
715 <div class="doc_subsection">
716 <a name="c-be">Known problems with the C back-end</a>
719 <div class="doc_text">
723 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
724 Analysis rules. As such, special options may be necessary to compile the code
725 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
726 problem probably cannot be fixed.</li>
728 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
729 cannot include special floating point numbers like Not-A-Number or
732 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
733 supported</a>. This should not affect LLVM produced by the C or C++
740 <!-- *********************************************************************** -->
741 <div class="doc_section">
742 <a name="additionalinfo">Additional Information</a>
744 <!-- *********************************************************************** -->
746 <div class="doc_text">
748 <p>A wide variety of additional information is available on the LLVM web page,
749 including mailing lists and publications describing algorithms and components
750 implemented in LLVM. The web page also contains versions of the API
751 documentation which is up-to-date with the CVS version of the source code. You
752 can access versions of these documents specific to this release by going into
753 the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
755 <p>If you have any questions or comments about LLVM, please feel free to contact
756 us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
761 <!-- *********************************************************************** -->
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