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  10
  11 <h1>LLVM 3.0 Release Notes</h1>
  12
  13 <img align=right src="http://llvm.org/img/DragonSmall.png"
  14     width="136" height="136" alt="LLVM Dragon Logo">
  15
  16 <ol>
  17   <li><a href="#intro">Introduction</a></li>
  18   <li><a href="#subproj">Sub-project Status Update</a></li>
  19   <li><a href="#externalproj">External Projects Using LLVM 3.0</a></li>
  20   <li><a href="#whatsnew">What's New in LLVM 3.0?</a></li>
  21   <li><a href="GettingStarted.html">Installation Instructions</a></li>
  22   <li><a href="#knownproblems">Known Problems</a></li>
  23   <li><a href="#additionalinfo">Additional Information</a></li>
  24 </ol>
  25
  26 <div class="doc_author">
  27   <p>Written by the <a href="http://llvm.org/">LLVM Team</a></p>
  28 </div>
  29
  30 <!--
  31 <h1 style="color:red">These are in-progress notes for the upcoming LLVM 3.0
  32 release.<br>
  33 You may prefer the
  34 <a href="http://llvm.org/releases/2.9/docs/ReleaseNotes.html">LLVM 2.9
  35 Release Notes</a>.</h1>
  36  -->
  37
  38 <!-- *********************************************************************** -->
  39 <h2>
  40   <a name="intro">Introduction</a>
  41 </h2>
  42 <!-- *********************************************************************** -->
  43
  44 <div>
  45
  46 <p>This document contains the release notes for the LLVM Compiler
  47 Infrastructure, release 3.0.  Here we describe the status of LLVM, including
  48 major improvements from the previous release and significant known problems.
  49 All LLVM releases may be downloaded from the <a
  50 href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
  51
  52 <p>For more information about LLVM, including information about the latest
  53 release, please check out the <a href="http://llvm.org/">main LLVM
  54 web site</a>.  If you have questions or comments, the <a
  55 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's
  56 Mailing List</a> is a good place to send them.</p>
  57
  58 <p>Note that if you are reading this file from a Subversion checkout or the
  59 main LLVM web page, this document applies to the <i>next</i> release, not the
  60 current one.  To see the release notes for a specific release, please see the
  61 <a href="http://llvm.org/releases/">releases page</a>.</p>
  62
  63 </div>
  64
  65 <!-- Features that need text if they're finished for 3.1:
  66   ARM EHABI
  67   combiner-aa?
  68   strong phi elim
  69   loop dependence analysis
  70   CorrelatedValuePropagation
  71   lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
  72  -->
  73
  74 <!-- *********************************************************************** -->
  75 <h2>
  76   <a name="subproj">Sub-project Status Update</a>
  77 </h2>
  78 <!-- *********************************************************************** -->
  79
  80 <div>
  81 <p>
  82 The LLVM 3.0 distribution currently consists of code from the core LLVM
  83 repository (which roughly includes the LLVM optimizers, code generators
  84 and supporting tools), the Clang repository and the llvm-gcc repository.  In
  85 addition to this code, the LLVM Project includes other sub-projects that are in
  86 development.  Here we include updates on these subprojects.
  87 </p>
  88
  89 <!--=========================================================================-->
  90 <h3>
  91 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
  92 </h3>
  93
  94 <div>
  95
  96 <p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
  97 C++, and Objective-C languages. Clang aims to provide a better user experience
  98 through expressive diagnostics, a high level of conformance to language
  99 standards, fast compilation, and low memory use. Like LLVM, Clang provides a
 100 modular, library-based architecture that makes it suitable for creating or
 101 integrating with other development tools. Clang is considered a
 102 production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
 103 (32- and 64-bit), and for darwin/arm targets.</p>
 104
 105 <p>In the LLVM 3.0 time-frame, the Clang team has made many improvements:</p>
 106
 107 <p>If Clang rejects your code but another compiler accepts it, please take a
 108 look at the <a href="http://clang.llvm.org/compatibility.html">language
 109 compatibility</a> guide to make sure this is not intentional or a known issue.
 110 </p>
 111
 112 </div>
 113
 114 <!--=========================================================================-->
 115 <h3>
 116 <a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
 117 </h3>
 118
 119 <div>
 120 <p>
 121 <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a
 122 <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
 123 optimizers and code generators with LLVM's.
 124 Currently it requires a patched version of gcc-4.5.
 125 The plugin can target the x86-32 and x86-64 processor families and has been
 126 used successfully on the Darwin, FreeBSD and Linux platforms.
 127 The Ada, C, C++ and Fortran languages work well.
 128 The plugin is capable of compiling plenty of Obj-C, Obj-C++ and Java but it is
 129 not known whether the compiled code actually works or not!
 130 </p>
 131
 132 <p>
 133 The 3.0 release has the following notable changes:
 134 <ul>
 135 <!--
 136 <li></li>
 137 -->
 138 </ul>
 139
 140 </div>
 141
 142 <!--=========================================================================-->
 143 <h3>
 144 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
 145 </h3>
 146
 147 <div>
 148 <p>
 149 The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
 150 is a simple library that provides an implementation of the low-level
 151 target-specific hooks required by code generation and other runtime components.
 152 For example, when compiling for a 32-bit target, converting a double to a 64-bit
 153 unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
 154 function. The compiler-rt library provides highly optimized implementations of
 155 this and other low-level routines (some are 3x faster than the equivalent
 156 libgcc routines).</p>
 157
 158 <p>In the LLVM 3.0 timeframe,</p>
 159
 160 </div>
 161
 162 <!--=========================================================================-->
 163 <h3>
 164 <a name="lldb">LLDB: Low Level Debugger</a>
 165 </h3>
 166
 167 <div>
 168 <p>
 169 <a href="http://lldb.llvm.org/">LLDB</a> is a brand new member of the LLVM
 170 umbrella of projects. LLDB is a next generation, high-performance debugger. It
 171 is built as a set of reusable components which highly leverage existing
 172 libraries in the larger LLVM Project, such as the Clang expression parser, the
 173 LLVM disassembler and the LLVM JIT.</p>
 174
 175 <p>
 176 LLDB is has advanced by leaps and bounds in the 3.0 timeframe.  It is
 177 dramatically more stable and useful, and includes both a new <a
 178 href="http://lldb.llvm.org/tutorial.html">tutorial</a> and a <a
 179 href="http://lldb.llvm.org/lldb-gdb.html">side-by-side comparison with
 180 GDB</a>.</p>
 181
 182 </div>
 183
 184 <!--=========================================================================-->
 185 <h3>
 186 <a name="libc++">libc++: C++ Standard Library</a>
 187 </h3>
 188
 189 <div>
 190 <p>
 191 <a href="http://libcxx.llvm.org/">libc++</a> is another new member of the LLVM
 192 family.  It is an implementation of the C++ standard library, written from the
 193 ground up to specifically target the forthcoming C++'0X standard and focus on
 194 delivering great performance.</p>
 195
 196 <p>
 197 In the LLVM 3.0 timeframe,</p>
 198
 199 <p>
 200 Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
 201   licensed</a> under the MIT and UIUC license, allowing it to be used more
 202   permissively.
 203 </p>
 204
 205 </div>
 206
 207
 208 <!--=========================================================================-->
 209 <h3>
 210 <a name="LLBrowse">LLBrowse: IR Browser</a>
 211 </h3>
 212
 213 <div>
 214 <p>
 215 <a href="http://llvm.org/svn/llvm-project/llbrowse/trunk/doc/LLBrowse.html">
 216   LLBrowse</a> is an interactive viewer for LLVM modules. It can load any LLVM
 217   module and displays its contents as an expandable tree view, facilitating an
 218   easy way to inspect types, functions, global variables, or metadata nodes. It
 219   is fully cross-platform, being based on the popular wxWidgets GUI toolkit.
 220 </p>
 221 </div>
 222
 223 <!--=========================================================================-->
 224 <h3>
 225 <a name="vmkit">VMKit</a>
 226 </h3>
 227
 228 <div>
 229 <p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation
 230   of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
 231   just-in-time compilation. As of LLVM 3.0, VMKit now supports generational
 232   garbage collectors. The garbage collectors are provided by the MMTk framework,
 233   and VMKit can be configured to use one of the numerous implemented collectors
 234   of MMTk.
 235 </p>
 236 </div>
 237
 238
 239 <!--=========================================================================-->
 240 <!--
 241 <h3>
 242 <a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
 243 </h3>
 244
 245 <div>
 246 <p>
 247 <a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for
 248 programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths
 249 through the application and records state transitions that lead to fault
 250 states. This allows it to construct testcases that lead to faults and can even
 251 be used to verify some algorithms.
 252 </p>
 253
 254 <p>UPDATE!</p>
 255 </div>-->
 256
 257 </div>
 258
 259 <!-- *********************************************************************** -->
 260 <h2>
 261   <a name="externalproj">External Open Source Projects Using LLVM 3.0</a>
 262 </h2>
 263 <!-- *********************************************************************** -->
 264
 265 <div>
 266
 267 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
 268    a lot of other language and tools projects.  This section lists some of the
 269    projects that have already been updated to work with LLVM 3.0.</p>
 270
 271 <!--=========================================================================-->
 272 <h3>Crack Programming Language</h3>
 273
 274 <div>
 275 <p>
 276 <a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide the
 277 ease of development of a scripting language with the performance of a compiled
 278 language. The language derives concepts from C++, Java and Python, incorporating
 279 object-oriented programming, operator overloading and strong typing.</p>
 280 </div>
 281
 282
 283 <!--=========================================================================-->
 284 <h3>TTA-based Codesign Environment (TCE)</h3>
 285
 286 <div>
 287 <p>TCE is a toolset for designing application-specific processors (ASP) based on
 288 the Transport triggered architecture (TTA). The toolset provides a complete
 289 co-design flow from C/C++ programs down to synthesizable VHDL and parallel
 290 program binaries. Processor customization points include the register files,
 291 function units, supported operations, and the interconnection network.</p>
 292
 293 <p>TCE uses Clang and LLVM for C/C++ language support, target independent
 294 optimizations and also for parts of code generation. It generates new LLVM-based
 295 code generators "on the fly" for the designed TTA processors and loads them in
 296 to the compiler backend as runtime libraries to avoid per-target recompilation
 297 of larger parts of the compiler chain.</p>
 298 </div>
 299
 300
 301
 302 <!--=========================================================================-->
 303 <h3>PinaVM</h3>
 304
 305 <div>
 306 <p><a href="http://gitorious.org/pinavm/pages/Home">PinaVM</a> is an open
 307 source, <a href="http://www.systemc.org/">SystemC</a> front-end. Unlike many
 308 other front-ends, PinaVM actually executes the elaboration of the
 309 program analyzed using LLVM's JIT infrastructure. It later enriches the
 310 bitcode with SystemC-specific information.</p>
 311 </div>
 312
 313 <!--=========================================================================-->
 314 <h3>Pure</h3>
 315
 316 <div>
 317 <p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
 318   algebraic/functional
 319   programming language based on term rewriting. Programs are collections
 320   of equations which are used to evaluate expressions in a symbolic
 321   fashion. The interpreter uses LLVM as a backend to JIT-compile Pure
 322   programs to fast native code. Pure offers dynamic typing, eager and lazy
 323   evaluation, lexical closures, a hygienic macro system (also based on
 324   term rewriting), built-in list and matrix support (including list and
 325   matrix comprehensions) and an easy-to-use interface to C and other
 326   programming languages (including the ability to load LLVM bitcode
 327   modules, and inline C, C++, Fortran and Faust code in Pure programs if
 328   the corresponding LLVM-enabled compilers are installed).</p>
 329
 330 <p>Pure version 0.47 has been tested and is known to work with LLVM 3.0
 331   (and continues to work with older LLVM releases &gt;= 2.5).</p>
 332 </div>
 333
 334 <!--=========================================================================-->
 335 <h3 id="icedtea">IcedTea Java Virtual Machine Implementation</h3>
 336
 337 <div>
 338 <p>
 339 <a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
 340 harness to build OpenJDK using only free software build tools and to provide
 341 replacements for the not-yet free parts of OpenJDK.  One of the extensions that
 342 IcedTea provides is a new JIT compiler named <a
 343 href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
 344 to provide native code generation without introducing processor-dependent
 345 code.
 346 </p>
 347
 348 <p> OpenJDK 7 b112, IcedTea6 1.9 and IcedTea7 1.13 and later have been tested
 349 and are known to work with LLVM 3.0 (and continue to work with older LLVM
 350 releases &gt;= 2.6 as well).</p>
 351 </div>
 352
 353 <!--=========================================================================-->
 354 <h3>Glasgow Haskell Compiler (GHC)</h3>
 355
 356 <div>
 357 <p>GHC is an open source, state-of-the-art programming suite for Haskell,
 358 a standard lazy functional programming language. It includes an
 359 optimizing static compiler generating good code for a variety of
 360 platforms, together with an interactive system for convenient, quick
 361 development.</p>
 362
 363 <p>In addition to the existing C and native code generators, GHC 7.0 now
 364 supports an LLVM code generator. GHC supports LLVM 2.7 and later.</p>
 365 </div>
 366
 367 <!--=========================================================================-->
 368 <h3>Polly - Polyhedral optimizations for LLVM</h3>
 369
 370 <div>
 371 <p>Polly is a project that aims to provide advanced memory access optimizations
 372 to better take advantage of SIMD units, cache hierarchies, multiple cores or
 373 even vector accelerators for LLVM. Built around an abstract mathematical
 374 description based on Z-polyhedra, it provides the infrastructure to develop
 375 advanced optimizations in LLVM and to connect complex external optimizers. In
 376 its first year of existence Polly already provides an exact value-based
 377 dependency analysis as well as basic SIMD and OpenMP code generation support.
 378 Furthermore, Polly can use PoCC(Pluto) an advanced optimizer for data-locality
 379 and parallelism.</p>
 380 </div>
 381
 382 <!--=========================================================================-->
 383 <h3>Rubinius</h3>
 384
 385 <div>
 386   <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
 387   for running Ruby code which strives to write as much of the implementation in
 388   Ruby as possible. Combined with a bytecode interpreting VM, it uses LLVM to
 389   optimize and compile ruby code down to machine code. Techniques such as type
 390   feedback, method inlining, and deoptimization are all used to remove dynamism
 391   from ruby execution and increase performance.</p>
 392 </div>
 393
 394
 395 <!--=========================================================================-->
 396 <h3>
 397 <a name="FAUST">FAUST Real-Time Audio Signal Processing Language</a>
 398 </h3>
 399
 400 <div>
 401 <p>
 402 <a href="http://faust.grame.fr">FAUST</a> is a compiled language for real-time
 403 audio signal processing. The name FAUST stands for Functional AUdio STream. Its
 404 programming model combines two approaches: functional programming and block
 405 diagram composition. In addition with the C, C++, JAVA output formats, the
 406 Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7-3.0.</p>
 407
 408 </div>
 409
 410 </div>
 411
 412 <!-- *********************************************************************** -->
 413 <h2>
 414   <a name="whatsnew">What's New in LLVM 3.0?</a>
 415 </h2>
 416 <!-- *********************************************************************** -->
 417
 418 <div>
 419
 420 <p>This release includes a huge number of bug fixes, performance tweaks and
 421 minor improvements.  Some of the major improvements and new features are listed
 422 in this section.
 423 </p>
 424
 425 <!--=========================================================================-->
 426 <h3>
 427 <a name="majorfeatures">Major New Features</a>
 428 </h3>
 429
 430 <div>
 431
 432 <p>LLVM 3.0 includes several major new capabilities:</p>
 433
 434 <ul>
 435
 436 <!--
 437 <li></li>
 438 -->
 439
 440 </ul>
 441
 442 </div>
 443
 444 <!--=========================================================================-->
 445 <h3>
 446 <a name="coreimprovements">LLVM IR and Core Improvements</a>
 447 </h3>
 448
 449 <div>
 450 <p>LLVM IR has several new features for better support of new targets and that
 451 expose new optimization opportunities:</p>
 452
 453 <ul>
 454 <!--
 455 <li></li>
 456 -->
 457 </ul>
 458
 459 </div>
 460
 461 <!--=========================================================================-->
 462 <h3>
 463 <a name="optimizer">Optimizer Improvements</a>
 464 </h3>
 465
 466 <div>
 467
 468 <p>In addition to a large array of minor performance tweaks and bug fixes, this
 469 release includes a few major enhancements and additions to the optimizers:</p>
 470
 471 <ul>
 472 <!--
 473 <li></li>
 474 -->
 475 </li>
 476
 477 </ul>
 478
 479 </div>
 480
 481 <!--=========================================================================-->
 482 <h3>
 483 <a name="mc">MC Level Improvements</a>
 484 </h3>
 485
 486 <div>
 487 <p>
 488 The LLVM Machine Code (aka MC) subsystem was created to solve a number
 489 of problems in the realm of assembly, disassembly, object file format handling,
 490 and a number of other related areas that CPU instruction-set level tools work
 491 in.</p>
 492
 493 <ul>
 494 <!--
 495 <li></li>
 496 -->
 497 </ul>
 498
 499 <p>For more information, please see the <a
 500 href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
 501 LLVM MC Project Blog Post</a>.
 502 </p>
 503
 504 </div>
 505
 506 <!--=========================================================================-->
 507 <h3>
 508 <a name="codegen">Target Independent Code Generator Improvements</a>
 509 </h3>
 510
 511 <div>
 512
 513 <p>We have put a significant amount of work into the code generator
 514 infrastructure, which allows us to implement more aggressive algorithms and make
 515 it run faster:</p>
 516
 517 <ul>
 518 <!--
 519 <li></li>
 520 -->
 521 </ul>
 522 </div>
 523
 524 <!--=========================================================================-->
 525 <h3>
 526 <a name="x86">X86-32 and X86-64 Target Improvements</a>
 527 </h3>
 528
 529 <div>
 530 <p>New features and major changes in the X86 target include:
 531 </p>
 532
 533 <ul>
 534 <li>The CRC32 intrinsics have been renamed.  The intrinsics were previously
 535   @llvm.x86.sse42.crc32.[8|16|32] and @llvm.x86.sse42.crc64.[8|64].  They have
 536   been renamed to @llvm.x86.sse42.crc32.32.[8|16|32] and
 537   @llvm.x86.sse42.crc32.64.[8|64].</li>
 538
 539 </ul>
 540
 541 </div>
 542
 543 <!--=========================================================================-->
 544 <h3>
 545 <a name="ARM">ARM Target Improvements</a>
 546 </h3>
 547
 548 <div>
 549 <p>New features of the ARM target include:
 550 </p>
 551
 552 <ul>
 553 <!--
 554 <li></li>
 555 -->
 556 </ul>
 557 </div>
 558
 559 <!--=========================================================================-->
 560 <h3>
 561 <a name="OtherTS">Other Target Specific Improvements</a>
 562 </h3>
 563
 564 <div>
 565 <ul>
 566 <!--
 567 <li></li>
 568 -->
 569 </ul>
 570 </div>
 571
 572 <!--=========================================================================-->
 573 <h3>
 574 <a name="changes">Major Changes and Removed Features</a>
 575 </h3>
 576
 577 <div>
 578
 579 <p>If you're already an LLVM user or developer with out-of-tree changes based
 580 on LLVM 2.9, this section lists some "gotchas" that you may run into upgrading
 581 from the previous release.</p>
 582
 583 <ul>
 584 <!--
 585 <li></li>
 586 -->
 587 </ul>
 588
 589 </div>
 590
 591 <!--=========================================================================-->
 592 <h3>
 593 <a name="api_changes">Internal API Changes</a>
 594 </h3>
 595
 596 <div>
 597
 598 <p>In addition, many APIs have changed in this release.  Some of the major
 599   LLVM API changes are:</p>
 600
 601 <ul>
 602 <!--
 603 <li></ld>
 604 -->
 605 </ul>
 606 </div>
 607
 608 </div>
 609
 610 <!-- *********************************************************************** -->
 611 <h2>
 612   <a name="knownproblems">Known Problems</a>
 613 </h2>
 614 <!-- *********************************************************************** -->
 615
 616 <div>
 617
 618 <p>This section contains significant known problems with the LLVM system,
 619 listed by component.  If you run into a problem, please check the <a
 620 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
 621 there isn't already one.</p>
 622
 623 <!-- ======================================================================= -->
 624 <h3>
 625   <a name="experimental">Experimental features included with this release</a>
 626 </h3>
 627
 628 <div>
 629
 630 <p>The following components of this LLVM release are either untested, known to
 631 be broken or unreliable, or are in early development.  These components should
 632 not be relied on, and bugs should not be filed against them, but they may be
 633 useful to some people.  In particular, if you would like to work on one of these
 634 components, please contact us on the <a
 635 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
 636
 637 <ul>
 638 <li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ
 639     and XCore backends are experimental.</li>
 640 <li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets
 641     other than darwin and ELF X86 systems.</li>
 642
 643 </ul>
 644
 645 </div>
 646
 647 <!-- ======================================================================= -->
 648 <h3>
 649   <a name="x86-be">Known problems with the X86 back-end</a>
 650 </h3>
 651
 652 <div>
 653
 654 <ul>
 655   <li>The X86 backend does not yet support
 656     all <a href="http://llvm.org/PR879">inline assembly that uses the X86
 657     floating point stack</a>.  It supports the 'f' and 't' constraints, but not
 658     'u'.</li>
 659   <li>The X86-64 backend does not yet support the LLVM IR instruction
 660       <tt>va_arg</tt>. Currently, front-ends support variadic
 661       argument constructs on X86-64 by lowering them manually.</li>
 662   <li>Windows x64 (aka Win64) code generator has a few issues.
 663     <ul>
 664       <li>llvm-gcc cannot build the mingw-w64 runtime currently
 665        due to lack of support for the 'u' inline assembly
 666        constraint and for X87 floating point inline assembly.</li>
 667       <li>On mingw-w64, you will see unresolved symbol <tt>__chkstk</tt>
 668        due to <a href="http://llvm.org/bugs/show_bug.cgi?id=8919">Bug 8919</a>.
 669        It is fixed in <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20110321/118499.html">r128206</a>.</li>
 670       <li>Miss-aligned MOVDQA might crash your program. It is due to
 671        <a href="http://llvm.org/bugs/show_bug.cgi?id=9483">Bug 9483</a>,
 672        lack of handling aligned internal globals.</li>
 673       </ul>
 674   </li>
 675
 676 </ul>
 677
 678 </div>
 679
 680 <!-- ======================================================================= -->
 681 <h3>
 682   <a name="ppc-be">Known problems with the PowerPC back-end</a>
 683 </h3>
 684
 685 <div>
 686
 687 <ul>
 688 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
 689 compilation, and lacks support for debug information.</li>
 690 </ul>
 691
 692 </div>
 693
 694 <!-- ======================================================================= -->
 695 <h3>
 696   <a name="arm-be">Known problems with the ARM back-end</a>
 697 </h3>
 698
 699 <div>
 700
 701 <ul>
 702 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
 703 processors, thumb programs can crash or produce wrong
 704 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
 705 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
 706 </li>
 707 </ul>
 708
 709 </div>
 710
 711 <!-- ======================================================================= -->
 712 <h3>
 713   <a name="sparc-be">Known problems with the SPARC back-end</a>
 714 </h3>
 715
 716 <div>
 717
 718 <ul>
 719 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
 720     support the 64-bit SPARC ABI (-m64).</li>
 721 </ul>
 722
 723 </div>
 724
 725 <!-- ======================================================================= -->
 726 <h3>
 727   <a name="mips-be">Known problems with the MIPS back-end</a>
 728 </h3>
 729
 730 <div>
 731
 732 <ul>
 733 <li>64-bit MIPS targets are not supported yet.</li>
 734 </ul>
 735
 736 </div>
 737
 738 <!-- ======================================================================= -->
 739 <h3>
 740   <a name="alpha-be">Known problems with the Alpha back-end</a>
 741 </h3>
 742
 743 <div>
 744
 745 <ul>
 746
 747 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
 748 appropriate nops inserted to ensure restartability.</li>
 749
 750 </ul>
 751 </div>
 752
 753 <!-- ======================================================================= -->
 754 <h3>
 755   <a name="c-be">Known problems with the C back-end</a>
 756 </h3>
 757
 758 <div>
 759
 760 <p>The C backend has numerous problems and is not being actively maintained.
 761 Depending on it for anything serious is not advised.</p>
 762
 763 <ul>
 764 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
 765     inline assembly code</a>.</li>
 766 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
 767     C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
 768     C++ code compiled with <tt>llc</tt> or native compilers.</li>
 769 <li>The C backend does not support all exception handling constructs.</li>
 770 <li>The C backend does not support arbitrary precision integers.</li>
 771 </ul>
 772
 773 </div>
 774
 775
 776 <!-- ======================================================================= -->
 777 <h3>
 778   <a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
 779 </h3>
 780
 781 <div>
 782
 783 <p><b>LLVM 3.0 will be the last release of llvm-gcc.</b></p>
 784
 785 <p>llvm-gcc is generally very stable for the C family of languages.  The only
 786    major language feature of GCC not supported by llvm-gcc is the
 787    <tt>__builtin_apply</tt> family of builtins.   However, some extensions
 788    are only supported on some targets.  For example, trampolines are only
 789    supported on some targets (these are used when you take the address of a
 790    nested function).</p>
 791
 792 <p>Fortran support generally works, but there are still several unresolved bugs
 793    in <a href="http://llvm.org/bugs/">Bugzilla</a>.  Please see the
 794    tools/gfortran component for details.  Note that llvm-gcc is missing major
 795    Fortran performance work in the frontend and library that went into GCC after
 796    4.2.  If you are interested in Fortran, we recommend that you consider using
 797    <a href="#dragonegg">dragonegg</a> instead.</p>
 798
 799 <p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being
 800 actively maintained.  If you are interested in Ada, we recommend that you
 801 consider using <a href="#dragonegg">dragonegg</a> instead.</p>
 802 </div>
 803
 804 </div>
 805
 806 <!-- *********************************************************************** -->
 807 <h2>
 808   <a name="additionalinfo">Additional Information</a>
 809 </h2>
 810 <!-- *********************************************************************** -->
 811
 812 <div>
 813
 814 <p>A wide variety of additional information is available on the <a
 815 href="http://llvm.org/">LLVM web page</a>, in particular in the <a
 816 href="http://llvm.org/docs/">documentation</a> section.  The web page also
 817 contains versions of the API documentation which is up-to-date with the
 818 Subversion version of the source code.
 819 You can access versions of these documents specific to this release by going
 820 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
 821
 822 <p>If you have any questions or comments about LLVM, please feel free to contact
 823 us via the <a href="http://llvm.org/docs/#maillist"> mailing
 824 lists</a>.</p>
 825
 826 </div>
 827
 828 <!-- *********************************************************************** -->
 829
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