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11 <div class="doc_title">LLVM 2.2 Release Notes</div>
14 <li><a href="#intro">Introduction</a></li>
15 <li><a href="#whatsnew">What's New?</a></li>
16 <li><a href="GettingStarted.html">Installation Instructions</a></li>
17 <li><a href="#portability">Portability and Supported Platforms</a></li>
18 <li><a href="#knownproblems">Known Problems</a>
19 <li><a href="#additionalinfo">Additional Information</a></li>
22 <div class="doc_author">
23 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
27 <!-- *********************************************************************** -->
28 <div class="doc_section">
29 <a name="intro">Introduction</a>
31 <!-- *********************************************************************** -->
33 <div class="doc_text">
35 <p>This document contains the release notes for the LLVM compiler
36 infrastructure, release 2.2. Here we describe the status of LLVM, including
37 major improvements from the previous release and any known problems. All LLVM
38 releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
39 releases web site</a>.</p>
41 <p>For more information about LLVM, including information about the latest
42 release, please check out the <a href="http://llvm.org/">main LLVM
43 web site</a>. If you have questions or comments, the <a
44 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
45 list</a> is a good place to send them.</p>
47 <p>Note that if you are reading this file from a Subversion checkout or the
48 main LLVM web page, this document applies to the <i>next</i> release, not the
49 current one. To see the release notes for a specific releases, please see the
50 <a href="http://llvm.org/releases/">releases page</a>.</p>
54 <!-- *********************************************************************** -->
55 <div class="doc_section">
56 <a name="whatsnew">What's New?</a>
58 <!-- *********************************************************************** -->
60 <div class="doc_text">
62 <p>This is the thirteenth public release of the LLVM Compiler Infrastructure.
63 It includes many features and refinements from LLVM 2.1.</p>
67 <!-- Unfinished features in 2.2:
68 Index Set Splitting not enabled by default
74 <!--=========================================================================-->
75 <div class="doc_subsection">
76 <a name="deprecation">Deprecated features in LLVM 2.2</a>
79 <div class="doc_text">
81 <p>This is the last LLVM release to support llvm-gcc 4.0, llvm-upgrade, and
82 llvmc in its current form. llvm-gcc 4.0 has been replaced with llvm-gcc 4.2.
83 llvm-upgrade is useful for upgrading llvm 1.9 files to llvm 2.x syntax, but you
84 can always use an old release to do this. llvmc is currently mostly useless in
85 llvm 2.2, and will be redesigned or removed in llvm 2.3.</p>
89 <!--=========================================================================-->
90 <div class="doc_subsection">
91 <a name="frontends">llvm-gcc 4.0, llvm-gcc 4.2, and clang</a>
94 <div class="doc_text">
96 <p>LLVM 2.2 fully supports both the llvm-gcc 4.0 and llvm-gcc 4.2 front-ends (in
97 LLVM 2.1, llvm-gcc 4.2 was beta). Since LLVM 2.1, the llvm-gcc 4.2 front-end
98 has made leaps and bounds and is now at least as good as 4.0 in virtually every
99 area, and is better in several areas (for example, exception handling
100 correctness, support for Ada and Fortran, better ABI compatibility, etc). We
101 strongly recommend that you
102 migrate from llvm-gcc 4.0 to llvm-gcc 4.2 in this release cycle because
103 <b>LLVM 2.2 is the last release that will support llvm-gcc 4.0</b>: LLVM 2.3
104 will only support the llvm-gcc 4.2 front-end.</p>
106 <p>The <a href="http://clang.llvm.org/">clang project</a> is an effort to build
107 a set of new 'llvm native' front-end technologies for the LLVM optimizer
108 and code generator. Currently, its C and Objective-C support is maturing
109 nicely, and it has advanced source-to-source analysis and transformation
110 capabilities. If you are interested in building source-level tools for C and
111 Objective-C (and eventually C++), you should take a look. However, note that
112 clang is not an official part of the LLVM 2.2 release. If you are interested in
113 this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
117 <!--=========================================================================-->
118 <div class="doc_subsection">
119 <a name="majorfeatures">Major New Features</a>
122 <div class="doc_text">
124 <p>LLVM 2.2 includes several major new capabilities:</p>
127 <li>Scott Michel contributed an SPU backend, which generates code for the
128 vector coprocessors on the Cell processor. (Status?)</li>
130 <li>Anton and Duncan significantly improved llvm-gcc 4.2 support for the GCC Ada
131 (GNAT) and Fortran (gfortran) front-ends. These front-ends should still be considered
132 experimental however: see the <a href="#knownproblems">list of known problems</a>.
133 The release binaries do not contain either front-end: they need to be built from
134 source (the Ada front-end only builds on x86-32 linux).</li>
136 <li>Dale contributed full support for long double on x86/x86-64 (where it is 80
137 bits) and on Darwin PPC/PPC64 (where it is 128 bits). In previous LLVM
138 releases, llvm-gcc silently mapped long double to double.</li>
140 <li>Gordon Henriksen rewrote most of the <a href="GarbageCollection.html"
141 >Accurate Garbage Collection</a> code in the code generator, making the
142 generated code more efficient and adding support for the OCaml garbage collector
143 metadata format.</li>
145 <li>Christopher Lamb contributed support for multiple address spaces in LLVM
146 IR. This is useful for supporting targets that have 'near' vs 'far' pointers,
147 'RAM' vs 'ROM' pointers, or that have non-local memory that can be accessed with
148 special instructions.</li>
150 <li>LLVM now includes a new set of detailed <a
151 href="tutorial/index.html">tutorials</a>, which explain how to implement a
152 language with LLVM and shows how to use several important APIs.</li>
158 <!--=========================================================================-->
159 <div class="doc_subsection">
160 <a name="coreimprovements">LLVM Core Improvements</a>
163 <div class="doc_text">
164 <p>New features include:
168 <li>Gordon contributed support for C and OCaml Bindings for the basic LLVM IR
169 construction routines as well as several other auxiliary APIs.</li>
171 <li>Anton added readnone/readonly attributes for modeling function side effects.
172 Duncan hooked up GCC's pure/const attributes to them and enhanced mod/ref
173 analysis to use them.</li>
175 <li>Devang added LLVMFoldingBuilder, a version of LLVMBuilder that implicitly
176 simplifies the code as it is constructed.</li>
178 <li>Ted Kremenek added a framework for generic object serialization to bitcode
179 files. This support is only used by clang right now for ASTs but is extensible
180 and could be used for serializing arbitrary other data into bitcode files.</li>
182 <li>Duncan improved TargetData to distinguish between the size/alignment of a
183 type in a register, in memory according to the platform ABI, and in memory when
184 we have a choice.</li>
186 <li>Reid moved parameter attributes off of FunctionType and onto functions
187 and calls. This makes it much easier to add attributes to a function in a
188 transformation pass.</li>
190 <li>Dan Gohman added support for vector sin, cos, and pow intrinsics.</li>
196 <!--=========================================================================-->
197 <div class="doc_subsection">
198 <a name="codegen">Code Generator Improvements</a>
201 <div class="doc_text">
203 <p>We put a significant amount of work into the code generator infrastructure,
204 which allows us to implement more aggressive algorithms and make it run
209 <li>Owen refactored the existing LLVM dominator and loop information code to
210 allow it work on the machine code representation. He contributed support for
211 dominator and loop information on machine code and merged the code for forward
212 and backward dominator computation.</li>
214 <li>Dan added support for emitting debug information with .file and .loc
215 directives on platforms that support it, instead of emitting large tables in the .s
218 <li>Evan extended the DAG scheduler to model physical register dependencies
219 explicitly and have the BURR scheduler pick a correct schedule based on the
220 dependencies. This reduces our use of the 'flag' operand hack.</li>
222 <li>Evan added initial support for register coalescing of subregister
225 <li>Rafael Espindola implemented initial support for a new 'byval' attribute,
226 which allows more efficient by-value argument passing in the LLVM IR. Evan
227 finished support for it and enabled it in the X86 (32- and 64-bit) and C
230 <li>The LLVM TargetInstrInfo class can now answer queries about the mod/ref and
231 side-effect behavior of MachineInstr's. This information is inferred
232 automatically by TableGen from .td files for all instructions with
235 <li>Evan implemented simple live interval splitting on basic block boundaries.
236 This allows the register allocator to be more successful at keeping values in
237 registers in some parts of a value's live range, even if they need to be spilled
238 in some other block.</li>
240 <li>The new MachineRegisterInfo.h class provides support for efficiently
241 iterating over all defs/uses of a register, and this information is
242 automatically kept up-to-date. This support is similar to the use_iterator in
243 the LLVM IR level.</li>
245 <li>The MachineInstr, MachineOperand and TargetInstrDesc classes are simpler,
246 more consistent, and better documented.</li>
251 <!--=========================================================================-->
252 <div class="doc_subsection">
253 <a name="optimizer">Optimizer Improvements</a>
256 <div class="doc_text">
258 <p>In addition to a huge array of bug fixes and minor performance tweaks, the
259 LLVM 2.2 optimizers support a few major enhancements:</p>
263 <li>Daniel Berlin and Curtis Dunham rewrote Andersen's alias analysis to be
264 several orders of magnitude faster, and implemented Offline Variable
265 Substitution and Lazy Cycle Detection. Note that Andersen's is not enabled in
266 llvm-gcc by default, but can be accessed through 'opt'.</li>
268 <li>Dan Gohman contributed several enhancements to Loop Strength Reduction (LSR)
269 to make it more aggressive with SSE intrinsics and when induction variables are
270 used by non-memory instructions.</li>
272 <li>Evan added support for simple exit value substitution to LSR.</li>
274 <li>Evan enhanced LSR to support induction variable reuse when the induction
275 variables have different widths.</li>
282 <!--=========================================================================-->
283 <div class="doc_subsection">
284 <a name="targetspecific">Target Specific Improvements</a>
287 <div class="doc_text">
288 <p>New target-specific features include:
292 <li>Evan contributed support to the X86 backend to model the mod/ref behavior
293 of the EFLAGS register explicitly in all instructions. This gives more freedom
294 to the scheduler, and is a more explicit way to model the instructions.</li>
295 <li>Dale contributed support for exception handling on Darwin/PPC and he and
296 Anton got x86-64 working.</li>
297 <li>Evan turned on if-conversion by default for ARM, allowing LLVM to take
298 advantage of its predication features.</li>
299 <li>Bruno added PIC support to the MIPS backend, fixed many bugs and improved
300 support for architecture variants.</li>
301 <li>Arnold Schwaighofer added support for X86 tail calls (limitations?
303 <li>Evan contributed several enhancements to Darwin/x86 debug information,
304 and improvements at -O0 (details?).</li>
305 <li>Duncan added x86-64 support for trampolines (pointers to nested functions).</li>
310 <!--=========================================================================-->
311 <div class="doc_subsection">
312 <a name="otherimprovements">Other Improvements</a>
315 <div class="doc_text">
316 <p>New features include:
320 <li>Gordon expanded and updated the <a href="Passes.html">LLVM Analysis and
321 Transformation Passes</a> reference to include descriptions for each pass.</li>
323 <li>We rewrote the lexer and parser used by TableGen to make them simpler
324 and cleaner. This gives tblgen support for 'caret diagnostics'. The .ll file
325 lexer was also rewritten to support caret diagnostics but doesn't use this
328 <li>Dale has been grinding through the GCC testsuite, and marked many
329 LLVM-incompatible tests as not-to-be-run (for example, if they are grepping
330 through some GCC dump file that LLVM doesn't produce), he also found and fixed
331 many LLVM bugs exposed by the testsuite.</li>
336 <!-- *********************************************************************** -->
337 <div class="doc_section">
338 <a name="portability">Portability and Supported Platforms</a>
340 <!-- *********************************************************************** -->
342 <div class="doc_text">
344 <p>LLVM is known to work on the following platforms:</p>
347 <li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
348 (and probably other unix-like systems).</li>
349 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
351 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
352 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
353 support is available for native builds with Visual C++).</li>
354 <li>Sun UltraSPARC workstations running Solaris 8.</li>
355 <li>Alpha-based machines running Debian GNU/Linux.</li>
356 <li>Itanium-based machines running Linux and HP-UX.</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>
367 <!-- *********************************************************************** -->
368 <div class="doc_section">
369 <a name="knownproblems">Known Problems</a>
371 <!-- *********************************************************************** -->
373 <div class="doc_text">
375 <p>This section contains all known problems with the LLVM system, listed by
376 component. As new problems are discovered, they will be added to these
377 sections. If you run into a problem, please check the <a
378 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
379 there isn't already one.</p>
383 <!-- ======================================================================= -->
384 <div class="doc_subsection">
385 <a name="experimental">Experimental features included with this release</a>
388 <div class="doc_text">
390 <p>The following components of this LLVM release are either untested, known to
391 be broken or unreliable, or are in early development. These components should
392 not be relied on, and bugs should not be filed against them, but they may be
393 useful to some people. In particular, if you would like to work on one of these
394 components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
397 <li>The <tt>-cee</tt> pass is known to be buggy and will be removed in
399 <li>The MSIL, IA64, Alpha, and MIPS backends are experimental.</li>
400 <li>The LLC "<tt>-filetype=asm</tt>" (the default) is the only supported
401 value for this option.</li>
402 <li>The llvmc tool is not supported.</li>
407 <!-- ======================================================================= -->
408 <div class="doc_subsection">
409 <a name="x86-be">Known problems with the X86 back-end</a>
412 <div class="doc_text">
415 <li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
416 assembly that uses the X86 floating point stack</a>.</li>
417 <li>The X86 backend occasionally has <a href="http://llvm.org/PR1649">alignment
418 problems</a> on operating systems that don't require 16-byte stack alignment
419 (including most non-darwin OS's like linux).</li>
420 <li>The X86 backend generates inefficient floating point code when configured to
421 generate code for systems that don't have SSE2.</li>
426 <!-- ======================================================================= -->
427 <div class="doc_subsection">
428 <a name="ppc-be">Known problems with the PowerPC back-end</a>
431 <div class="doc_text">
434 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
435 compilation, and lacks support for debug information.</li>
440 <!-- ======================================================================= -->
441 <div class="doc_subsection">
442 <a name="arm-be">Known problems with the ARM back-end</a>
445 <div class="doc_text">
448 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
449 processors, thumb programs can crash or produce wrong
450 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
451 <li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
453 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
454 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
459 <!-- ======================================================================= -->
460 <div class="doc_subsection">
461 <a name="sparc-be">Known problems with the SPARC back-end</a>
464 <div class="doc_text">
467 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
468 support the 64-bit SPARC ABI (-m64).</li>
473 <!-- ======================================================================= -->
474 <div class="doc_subsection">
475 <a name="alpha-be">Known problems with the Alpha back-end</a>
478 <div class="doc_text">
482 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
483 appropriate nops inserted to ensure restartability.</li>
488 <!-- ======================================================================= -->
489 <div class="doc_subsection">
490 <a name="ia64-be">Known problems with the IA64 back-end</a>
493 <div class="doc_text">
497 <li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
498 made where the argument is not 16-byte aligned, as required on IA64. (Strictly
499 speaking this is not a bug in the IA64 back-end; it will also be encountered
500 when building C++ programs using the C back-end.)</li>
502 <li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
503 ABI compliant layout of v-tables</a>. In particular, it just stores function
504 pointers instead of function descriptors in the vtable. This bug prevents
505 mixing C++ code compiled with LLVM with C++ objects compiled by other C++
508 <li>There are a few ABI violations which will lead to problems when mixing LLVM
509 output with code built with other compilers, particularly for floating-point
512 <li>Defining vararg functions is not supported (but calling them is ok).</li>
514 <li>The Itanium backend has bitrotted somewhat.</li>
519 <!-- ======================================================================= -->
520 <div class="doc_subsection">
521 <a name="c-be">Known problems with the C back-end</a>
524 <div class="doc_text">
527 <li><a href="http://llvm.org/PR802">The C backend does not support inline
528 assembly code</a>.</li>
529 <li><a href="http://llvm.org/PR1126">The C backend does not support vectors
531 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
532 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
533 C++ code compiled with LLC or native compilers.</li>
534 <li>The C backend does not support all exception handling constructs.</li>
540 <!-- ======================================================================= -->
541 <div class="doc_subsection">
542 <a name="c-fe">Known problems with the C front-end</a>
545 <!-- ======================================================================= -->
546 <div class="doc_subsection">
547 <a name="ada-fe">Known problems with the Ada front-end</a>
550 <div class="doc_text">
551 The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
552 technology and problems should be expected.
554 <li>The Ada front-end currently only builds on x86-32. This is mainly due
555 to lack of trampoline support (pointers to nested functions) on other platforms,
556 however it <a href="http://llvm.org/PR2006">also fails to build on x86-64</a>
557 which does support trampolines.</li>
558 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
559 Workaround: configure with --disable-bootstrap.</li>
560 <li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
561 fail (c380004 also fails with gcc-4.2 mainline).</li>
562 <li>Many gcc specific Ada tests continue to crash the compiler.</li>
563 <li>The -E binder option (exception backtraces)
564 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
565 crashing if an exception is raised. Workaround: do not use -E.</li>
566 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
567 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
568 or use representation clauses that result in a field of a non-discrete type
569 starting or finishing in the middle of a byte.</li>
570 <li>The lli interpreter <a href="http://llvm.org/PR2009">considers 'main'
571 as generated by the Ada binder to be invalid</a>.
572 Workaround: hand edit the file to use pointers for argv and envp rather than
574 <li>The -fstack-check option <a href="http://llvm.org/PR2008">is ignored</a>.</li>
578 <!-- ======================================================================= -->
579 <div class="doc_subsection">
580 <a name="fortran-fe">Known problems with the Fortran front-end</a>
583 <div class="doc_text">
586 <li>The llvm-gcc 4.2 gfortran front-end supports a broad range of Fortran code, but does
587 <a href="http://llvm.org/PR1971">not support EQUIVALENCE yet</a>.</li>
591 <!-- _______________________________________________________________________ -->
592 <div class="doc_subsubsection">Bugs</div>
594 <div class="doc_text">
596 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
597 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
598 llvmdev mailing list if you are interested.</p>
602 <!-- _______________________________________________________________________ -->
603 <div class="doc_subsubsection">
607 <div class="doc_text">
610 <li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
611 See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
614 <li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
616 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>:
618 As in Algol and Pascal, lexical scoping of functions.
619 Nested functions are supported, but llvm-gcc does not support
620 taking the address of a nested function (except on X86 targets)
621 or non-local gotos.</li>
623 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
625 Declaring that functions have no side effects or that they can never
628 <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
629 <tt>const</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
630 <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
631 <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noinline</tt>,
632 <tt>noreturn</tt>, <tt>nothrow</tt>, <tt>pure</tt>, <tt>regparm</tt>
633 <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
634 <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
636 <b>Ignored:</b> <tt>malloc</tt>,
637 <tt>no_instrument_function</tt></li>
641 <li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
644 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
645 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
646 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
647 Other built-in functions.</li>
648 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
649 Specifying attributes of variables.</li>
650 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
651 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
652 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
653 Arrays whose length is computed at run time.</li>
654 <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>
655 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
656 <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>
657 <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>
658 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
659 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
660 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
661 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
662 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
663 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
664 <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>
665 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
666 <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>
667 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
668 <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>
669 <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>
670 <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>
671 <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>
672 <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>
673 <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>
674 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
675 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
676 or arrays as values.</li>
677 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
678 <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>
679 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
680 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
681 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
682 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Comments.html#C_002b_002b-Comments">C++ Comments</a>: C++ comments are recognized.</li>
683 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
684 <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>
685 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
686 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
687 <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>
688 <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>
689 <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>
690 <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>
691 <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>
692 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
697 <p>If you run into GCC extensions which have not been included in any of these
698 lists, please let us know (also including whether or not they work).</p>
702 <!-- ======================================================================= -->
703 <div class="doc_subsection">
704 <a name="c++-fe">Known problems with the C++ front-end</a>
707 <div class="doc_text">
709 <p>The C++ front-end is considered to be fully
710 tested and works for a number of non-trivial programs, including LLVM
711 itself, Qt, Mozilla, etc.</p>
714 <li>Exception handling only works well on the X86 and PowerPC targets.
715 It works well for x86-64 darwin but not x86-64 linux.</li>
722 <!-- *********************************************************************** -->
723 <div class="doc_section">
724 <a name="additionalinfo">Additional Information</a>
726 <!-- *********************************************************************** -->
728 <div class="doc_text">
730 <p>A wide variety of additional information is available on the <a
731 href="http://llvm.org">LLVM web page</a>, in particular in the <a
732 href="http://llvm.org/docs/">documentation</a> section. The web page also
733 contains versions of the API documentation which is up-to-date with the
734 Subversion version of the source code.
735 You can access versions of these documents specific to this release by going
736 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
738 <p>If you have any questions or comments about LLVM, please feel free to contact
739 us via the <a href="http://llvm.org/docs/#maillist"> mailing
744 <!-- *********************************************************************** -->
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