docs/ReleaseNotes-2.6.html

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  10
  11 <div class="doc_title">LLVM 2.6 Release Notes</div>
  12
  13 <ol>
  14   <li><a href="#intro">Introduction</a></li>
  15   <li><a href="#subproj">Sub-project Status Update</a></li>
  16   <li><a href="#externalproj">External Projects Using LLVM 2.6</a></li>
  17   <li><a href="#whatsnew">What's New in LLVM 2.6?</a></li>
  18   <li><a href="GettingStarted.html">Installation Instructions</a></li>
  19   <li><a href="#portability">Portability and Supported Platforms</a></li>
  20   <li><a href="#knownproblems">Known Problems</a></li>
  21   <li><a href="#additionalinfo">Additional Information</a></li>
  22 </ol>
  23
  24 <div class="doc_author">
  25   <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
  26 </div>
  27
  28 <!-- *********************************************************************** -->
  29 <div class="doc_section">
  30   <a name="intro">Introduction</a>
  31 </div>
  32 <!-- *********************************************************************** -->
  33
  34 <div class="doc_text">
  35
  36 <p>This document contains the release notes for the LLVM Compiler
  37 Infrastructure, release 2.6.  Here we describe the status of LLVM, including
  38 major improvements from the previous release and significant known problems.
  39 All LLVM releases may be downloaded from the <a
  40 href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
  41
  42 <p>For more information about LLVM, including information about the latest
  43 release, please check out the <a href="http://llvm.org/">main LLVM
  44 web site</a>.  If you have questions or comments, the <a
  45 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
  46 List</a> is a good place to send them.</p>
  47
  48 <p>Note that if you are reading this file from a Subversion checkout or the
  49 main LLVM web page, this document applies to the <i>next</i> release, not the
  50 current one.  To see the release notes for a specific release, please see the
  51 <a href="http://llvm.org/releases/">releases page</a>.</p>
  52
  53 </div>
  54
  55 <!-- Unfinished features in 2.5:
  56   Machine LICM
  57   Machine Sinking
  58   target-specific intrinsics
  59   gold lto plugin
  60   pre-alloc splitter, strong phi elim
  61   <tt>llc -enable-value-prop</tt>, propagation of value info
  62        (sign/zero ext info) from one MBB to another
  63   debug info for optimized code
  64   interpreter + libffi
  65   postalloc scheduler: anti dependence breaking, hazard recognizer?
  66
  67 initial support for debug line numbers when optimization enabled, not useful in
  68   2.5 but will be for 2.6.
  69
  70  -->
  71
  72  <!-- for announcement email:
  73    -->
  74
  75 <!-- *********************************************************************** -->
  76 <div class="doc_section">
  77   <a name="subproj">Sub-project Status Update</a>
  78 </div>
  79 <!-- *********************************************************************** -->
  80
  81 <div class="doc_text">
  82 <p>
  83 The LLVM 2.6 distribution currently consists of code from the core LLVM
  84 repository &mdash;which roughly includes the LLVM optimizers, code generators
  85 and supporting tools &mdash; and the llvm-gcc repository.  In addition to this
  86 code, the LLVM Project includes other sub-projects that are in development.  The
  87 two which are the most actively developed are the <a href="#clang">Clang
  88 Project</a> and the <a href="#vmkit">VMKit Project</a>.
  89 </p>
  90
  91 </div>
  92
  93
  94 <!--=========================================================================-->
  95 <div class="doc_subsection">
  96 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
  97 </div>
  98
  99 <div class="doc_text">
 100
 101 <p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
 102 a set of new 'LLVM native' front-end technologies for the LLVM optimizer and
 103 code generator.  While Clang is not included in the LLVM 2.6 release, it is
 104 continuing to make major strides forward in all areas.  Its C and Objective-C
 105 parsing and code generation support is now very solid.  For example, it is
 106 capable of successfully building many real-world applications for X86-32
 107 and X86-64,
 108 including the <a href="http://wiki.freebsd.org/BuildingFreeBSDWithClang">FreeBSD
 109 kernel</a> and <a href="http://gcc.gnu.org/gcc-4.2/">gcc 4.2</a>.  C++ is also
 110 making <a href="http://clang.llvm.org/cxx_status.html">incredible progress</a>,
 111 and work on templates has recently started.  If you are
 112 interested in fast compiles and good diagnostics, we encourage you to try it out
 113 by <a href="http://clang.llvm.org/get_started.html">building from mainline</a>
 114 and reporting any issues you hit to the <a
 115 href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
 116 list</a>.</p>
 117
 118 <p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p>
 119
 120 <ul>
 121 <li>Something wonderful!</li>
 122 <li>Many many bugs are fixed and many features have been added.</li>
 123 </ul>
 124 </div>
 125
 126 <!--=========================================================================-->
 127 <div class="doc_subsection">
 128 <a name="clangsa">Clang Static Analyzer</a>
 129 </div>
 130
 131 <div class="doc_text">
 132
 133 <p>Previously announced in the 2.4 LLVM release, the Clang project also
 134 includes an early stage static source code analysis tool for <a
 135 href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
 136 in C and Objective-C programs. The tool performs a growing set of checks to find
 137 bugs that occur on a specific path within a program.</p>
 138
 139 <p>In the LLVM 2.6 time-frame there have been many significant improvements to
 140 XYZ.</p>
 141
 142 <p>The set of checks performed by the static analyzer continues to expand, and
 143 future plans for the tool include full source-level inter-procedural analysis
 144 and deeper checks such as buffer overrun detection. There are many opportunities
 145 to extend and enhance the static analyzer, and anyone interested in working on
 146 this project is encouraged to get involved!</p>
 147
 148 </div>
 149
 150 <!--=========================================================================-->
 151 <div class="doc_subsection">
 152 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
 153 </div>
 154
 155 <div class="doc_text">
 156 <p>
 157 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
 158 a JVM and a CLI Virtual Machines (Microsoft .NET is an
 159 implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
 160
 161 <p>Following LLVM 2.6, VMKit has its XYZ release that you can find on its
 162 <a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
 163 bug fixes, cleanup and new features. The major changes are:</p>
 164
 165 <ul>
 166
 167 <li>Something wonderful!</li>
 168
 169 </ul>
 170 </div>
 171
 172 <!-- *********************************************************************** -->
 173 <div class="doc_section">
 174   <a name="externalproj">External Projects Using LLVM 2.6</a>
 175 </div>
 176 <!-- *********************************************************************** -->
 177
 178 <!--=========================================================================-->
 179 <div class="doc_subsection">
 180 <a name="pure">Pure</a>
 181 </div>
 182
 183 <div class="doc_text">
 184 <p>
 185 <a href="http://pure-lang.googlecode.com/">Pure</a>
 186 is an algebraic/functional programming language based on term rewriting.
 187 Programs are collections of equations which are used to evaluate expressions in
 188 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
 189 lexical closures, a hygienic macro system (also based on term rewriting),
 190 built-in list and matrix support (including list and matrix comprehensions) and
 191 an easy-to-use C interface. The interpreter uses LLVM as a backend to
 192  JIT-compile Pure programs to fast native code.</p>
 193
 194 <p>In addition to the usual algebraic data structures, Pure also has
 195 MATLAB-style matrices in order to support numeric computations and signal
 196 processing in an efficient way. Pure is mainly aimed at mathematical
 197 applications right now, but it has been designed as a general purpose language.
 198 The dynamic interpreter environment and the C interface make it possible to use
 199 it as a kind of functional scripting language for many application areas.
 200 </p>
 201 </div>
 202
 203
 204 <!--=========================================================================-->
 205 <div class="doc_subsection">
 206 <a name="ldc">LLVM D Compiler</a>
 207 </div>
 208
 209 <div class="doc_text">
 210 <p>
 211 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
 212 the D Programming Language using the LLVM optimizer and code generator.
 213 The LDC project works great with the LLVM 2.6 release.  General improvements in
 214 this
 215 cycle have included new inline asm constraint handling, better debug info
 216 support, general bugfixes, and better x86-64 support.  This has allowed
 217 some major improvements in LDC, getting us much closer to being as
 218 fully featured as the original DMD compiler from DigitalMars.
 219 </p>
 220 </div>
 221
 222 <!--=========================================================================-->
 223 <div class="doc_subsection">
 224 <a name="RoadsendPHP">Roadsend PHP</a>
 225 </div>
 226
 227 <div class="doc_text">
 228 <p><a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
 229 source implementation of the PHP programming
 230 language that uses LLVM for its optimizer, JIT, and static compiler. This is a
 231 reimplementation of an earlier project that is now based on LLVM.</p>
 232 </div>
 233
 234 <!--=========================================================================-->
 235 <div class="doc_subsection">
 236 <a name="Unladen Swallow">Unladen Swallow</a>
 237 </div>
 238
 239 <div class="doc_text">
 240 <p><a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
 241 branch of <a href="http://python.org/">Python</a> intended to be fully
 242 compatible and significantly faster.  It uses LLVM's optimization passes and JIT
 243 compiler.</p>
 244 </div>
 245
 246 <!--=========================================================================-->
 247 <div class="doc_subsection">
 248 <a name="Rubinius">Rubinius</a>
 249 </div>
 250
 251 <div class="doc_text">
 252 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is a new virtual
 253 machine for Ruby. It leverages LLVM to dynamically compile Ruby code down to
 254 machine code using LLVM's JIT.</p>
 255 </div>
 256
 257
 258 <!-- *********************************************************************** -->
 259 <div class="doc_section">
 260   <a name="whatsnew">What's New in LLVM 2.6?</a>
 261 </div>
 262 <!-- *********************************************************************** -->
 263
 264 <div class="doc_text">
 265
 266 <p>This release includes a huge number of bug fixes, performance tweaks, and
 267 minor improvements.  Some of the major improvements and new features are listed
 268 in this section.
 269 </p>
 270 </div>
 271
 272 <!--=========================================================================-->
 273 <div class="doc_subsection">
 274 <a name="majorfeatures">Major New Features</a>
 275 </div>
 276
 277 <div class="doc_text">
 278
 279 <p>LLVM 2.6 includes several major new capabilities:</p>
 280
 281 <ul>
 282 <li>Something wonderful!</li>
 283 </ul>
 284
 285 </div>
 286
 287
 288 <!--=========================================================================-->
 289 <div class="doc_subsection">
 290 <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
 291 </div>
 292
 293 <div class="doc_text">
 294
 295 <p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
 296 front-ends and driver with the LLVM optimizer and code generator.  It currently
 297 includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
 298
 299 <ul>
 300 <li>Something wonderful!</li>
 301 </ul>
 302
 303 </div>
 304
 305
 306 <!--=========================================================================-->
 307 <div class="doc_subsection">
 308 <a name="coreimprovements">LLVM IR and Core Improvements</a>
 309 </div>
 310
 311 <div class="doc_text">
 312 <p>LLVM IR has several new features that are used by our existing front-ends and
 313 can be useful if you are writing a front-end for LLVM:</p>
 314
 315 <ul>
 316 <li>Something wonderful!</li>
 317 </ul>
 318
 319 </div>
 320
 321 <!--=========================================================================-->
 322 <div class="doc_subsection">
 323 <a name="optimizer">Optimizer Improvements</a>
 324 </div>
 325
 326 <div class="doc_text">
 327
 328 <p>In addition to a large array of bug fixes and minor performance tweaks, this
 329 release includes a few major enhancements and additions to the optimizers:</p>
 330
 331 <ul>
 332
 333 <li>Something wonderful!</li>
 334
 335 </ul>
 336
 337 </div>
 338
 339 <!--=========================================================================-->
 340 <div class="doc_subsection">
 341 <a name="codegen">Target Independent Code Generator Improvements</a>
 342 </div>
 343
 344 <div class="doc_text">
 345
 346 <p>We have put a significant amount of work into the code generator
 347 infrastructure, which allows us to implement more aggressive algorithms and make
 348 it run faster:</p>
 349
 350 <ul>
 351
 352 <li>Something wonderful!</li>
 353 </ul>
 354 </div>
 355
 356 <!--=========================================================================-->
 357 <div class="doc_subsection">
 358 <a name="x86">X86-32 and X86-64 Target Improvements</a>
 359 </div>
 360
 361 <div class="doc_text">
 362 <p>New features of the X86 target include:
 363 </p>
 364
 365 <ul>
 366
 367 <li>Something wonderful!</li>
 368 </ul>
 369
 370 </div>
 371
 372 <!--=========================================================================-->
 373 <div class="doc_subsection">
 374 <a name="pic16">PIC16 Target Improvements</a>
 375 </div>
 376
 377 <div class="doc_text">
 378 <p>New features of the PIC16 target include:
 379 </p>
 380
 381 <ul>
 382 <li>Something wonderful!</li>
 383 </ul>
 384
 385 <p>Things not yet supported:</p>
 386
 387 <ul>
 388 <li>Floating point.</li>
 389 <li>Passing/returning aggregate types to and from functions.</li>
 390 <li>Variable arguments.</li>
 391 <li>Indirect function calls.</li>
 392 <li>Interrupts/programs.</li>
 393 <li>Debug info.</li>
 394 </ul>
 395
 396 </div>
 397
 398
 399 <!--=========================================================================-->
 400 <div class="doc_subsection">
 401 <a name="llvmc">Improvements in LLVMC</a>
 402 </div>
 403
 404 <div class="doc_text">
 405 <p>New features include:</p>
 406
 407 <ul>
 408 <li>Something wonderful!</li>
 409 </ul>
 410
 411 </div>
 412
 413
 414 <!--=========================================================================-->
 415 <div class="doc_subsection">
 416 <a name="changes">Major Changes and Removed Features</a>
 417 </div>
 418
 419 <div class="doc_text">
 420
 421 <p>If you're already an LLVM user or developer with out-of-tree changes based
 422 on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading
 423 from the previous release.</p>
 424
 425 <ul>
 426
 427 <li>Something horrible!</li>
 428
 429 </ul>
 430
 431
 432 <p>In addition, many APIs have changed in this release.  Some of the major LLVM
 433 API changes are:</p>
 434
 435 <ul>
 436 <li>LLVM's global uniquing tables for <tt>Type</tt>s and <tt>Constant</tt>s have
 437     been privatized into members of an <tt>LLVMContext</tt>.  A number of APIs
 438     now take an <tt>LLVMContext</tt> as a parameter.  To smooth the transition
 439     for clients that will only ever use a single context, the new
 440     <tt>getGlobalContext()</tt> API can be used to access a default global
 441     context which can be passed in any and all cases where a context is
 442     required.
 443 <li>The <tt>getABITypeSize</tt> methods are now called <tt>getAllocSize</tt>.</li>
 444 <li>The <tt>Add</tt>, <tt>Sub</tt>, and <tt>Mul</tt> operators are no longer
 445     overloaded for floating-point types. Floating-point addition, subtraction,
 446     and multiplication are now represented with new operators <tt>FAdd</tt>,
 447     <tt>FSub</tt>, and <tt>FMul</tt>. In the <tt>IRBuilder</tt> API,
 448     <tt>CreateAdd</tt>, <tt>CreateSub</tt>, <tt>CreateMul</tt>, and
 449     <tt>CreateNeg</tt> should only be used for integer arithmetic now;
 450     <tt>CreateFAdd</tt>, <tt>CreateFSub</tt>, <tt>CreateFMul</tt>, and
 451     <tt>CreateFNeg</tt> should now be used for floating-point arithmetic.</li>
 452 <li>The DynamicLibrary class can no longer be constructed, its functionality has
 453     moved to static member functions.</li>
 454 <li><tt>raw_fd_ostream</tt>'s constructor for opening a given filename now
 455     takes an extra <tt>Force</tt> argument. If <tt>Force</tt> is set to
 456     <tt>false</tt>, an error will be reported if a file with the given name
 457     already exists. If <tt>Force</tt> is set to <tt>true</tt>, the file will
 458     be silently truncated (which is the behavior before this flag was
 459     added).</li>
 460 <li><tt>SCEVHandle</tt> no longer exists, because reference counting is no
 461 longer done for <tt>SCEV*</tt> objects, instead <tt>const SCEV*</tt> should be
 462 used.</li>
 463
 464 <li>Many APIs, notably <tt>llvm::Value</tt>, now use the <tt>StringRef</tt>
 465 and <tt>Twine</tt> classes instead of passing <tt>const char*</tt>
 466 or <tt>std::string</tt>, as described in
 467 the <a href="ProgrammersManual.html#string_apis">Programmer's Manual</a>. Most
 468 clients should be unaffected by this transition, unless they are used to <tt>Value::getName()</tt> returning a string. Here are some tips on updating to 2.6:
 469   <ul>
 470     <li><tt>getNameStr()</tt> is still available, and matches the old
 471       behavior. Replacing <tt>getName()</tt> calls with this is an safe option,
 472       although more efficient alternatives are now possible.</li>
 473
 474     <li>If you were just relying on <tt>getName()</tt> being able to be sent to
 475       a <tt>std::ostream</tt>, consider migrating
 476       to <tt>llvm::raw_ostream</tt>.</li>
 477
 478     <li>If you were using <tt>getName().c_str()</tt> to get a <tt>const
 479         char*</tt> pointer to the name, you can use <tt>getName().data()</tt>.
 480         Note that this string (as before), may not be the entire name if the
 481         name containts embedded null characters.</li>
 482
 483     <li>If you were using operator plus on the result of <tt>getName()</tt> and
 484       treating the result as an <tt>std::string</tt>, you can either
 485       uses <tt>Twine::str</tt> to get the result as an <tt>std::string</tt>, or
 486       could move to a <tt>Twine</tt> based design.</li>
 487
 488     <li><tt>isName()</tt> should be replaced with comparison
 489       against <tt>getName()</tt> (this is now efficient).
 490   </ul>
 491 </li>
 492
 493 <li>The registration interfaces for backend Targets has changed (what was
 494 previously TargetMachineRegistry). For backend authors, see the <a href="WritingAnLLVMBackend.html#TargetRegistration">Writing An LLVM Backend</a> guide. For clients, the notable API changes are:
 495   <ul>
 496     <li><tt>TargetMachineRegistry</tt> has been renamed
 497       to <tt>TargetRegistry</tt>.</li>
 498
 499     <li>Clients should move to using the <tt>TargetRegistry::lookupTarget()</tt>
 500       function to find targets.</li>
 501   </ul>
 502 </li>
 503
 504 <li>llvm-dis now fails if output file exists, instead of dumping to stdout.
 505 FIXME: describe any other tool changes due to the raw_fd_ostream change.  FIXME:
 506 This is not an API change, maybe there should be a tool changes section?</li>
 507 <li>temporarely due to Context API change passes should call doInitialization()
 508 method of the pass they inherit from, otherwise Context is NULL.
 509 FIXME: remove this entry when this is no longer needed.<li>
 510 </ul>
 511
 512 </div>
 513
 514
 515
 516 <!-- *********************************************************************** -->
 517 <div class="doc_section">
 518   <a name="portability">Portability and Supported Platforms</a>
 519 </div>
 520 <!-- *********************************************************************** -->
 521
 522 <div class="doc_text">
 523
 524 <p>LLVM is known to work on the following platforms:</p>
 525
 526 <ul>
 527 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
 528 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like systems).</li>
 529 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
 530 and 64-bit modes.</li>
 531 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
 532 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
 533     support is available for native builds with Visual C++).</li>
 534 <li>Sun UltraSPARC workstations running Solaris 10.</li>
 535 <li>Alpha-based machines running Debian GNU/Linux.</li>
 536 </ul>
 537
 538 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
 539 to the machine and operating system on which it is built.  However, minor
 540 porting may be required to get LLVM to work on new platforms.  We welcome your
 541 portability patches and reports of successful builds or error messages.</p>
 542
 543 </div>
 544
 545 <!-- *********************************************************************** -->
 546 <div class="doc_section">
 547   <a name="knownproblems">Known Problems</a>
 548 </div>
 549 <!-- *********************************************************************** -->
 550
 551 <div class="doc_text">
 552
 553 <p>This section contains significant known problems with the LLVM system,
 554 listed by component.  If you run into a problem, please check the <a
 555 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
 556 there isn't already one.</p>
 557
 558 <ul>
 559 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
 560 using the stock GCC 3.x.x series 'out the box',
 561 See: <a href="#brokengcc">Broken versions of GCC and other tools</a>.
 562 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
 563 for x86/x64 has been made available from the third party AuroraUX Project
 564 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
 565 </ul>
 566
 567 </div>
 568
 569 <!-- ======================================================================= -->
 570 <div class="doc_subsection">
 571   <a name="experimental">Experimental features included with this release</a>
 572 </div>
 573
 574 <div class="doc_text">
 575
 576 <p>The following components of this LLVM release are either untested, known to
 577 be broken or unreliable, or are in early development.  These components should
 578 not be relied on, and bugs should not be filed against them, but they may be
 579 useful to some people.  In particular, if you would like to work on one of these
 580 components, please contact us on the <a
 581 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
 582
 583 <ul>
 584 <li>The MSIL, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
 585 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
 586     supported value for this option.</li>
 587 </ul>
 588
 589 </div>
 590
 591 <!-- ======================================================================= -->
 592 <div class="doc_subsection">
 593   <a name="x86-be">Known problems with the X86 back-end</a>
 594 </div>
 595
 596 <div class="doc_text">
 597
 598 <ul>
 599   <li>The X86 backend does not yet support
 600     all <a href="http://llvm.org/PR879">inline assembly that uses the X86
 601     floating point stack</a>.  It supports the 'f' and 't' constraints, but not
 602     'u'.</li>
 603   <li>The X86 backend generates inefficient floating point code when configured
 604     to generate code for systems that don't have SSE2.</li>
 605   <li>Win64 code generation wasn't widely tested. Everything should work, but we
 606     expect small issues to happen. Also, llvm-gcc cannot build the mingw64
 607     runtime currently due
 608     to <a href="http://llvm.org/PR2255">several</a>
 609     <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
 610     the
 611     'u' inline assembly constraint and for X87 floating point inline assembly.</li>
 612   <li>The X86-64 backend does not yet support the LLVM IR instruction
 613       <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
 614       argument constructs on X86-64 by lowering them manually.</li>
 615 </ul>
 616
 617 </div>
 618
 619 <!-- ======================================================================= -->
 620 <div class="doc_subsection">
 621   <a name="ppc-be">Known problems with the PowerPC back-end</a>
 622 </div>
 623
 624 <div class="doc_text">
 625
 626 <ul>
 627 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
 628 compilation, and lacks support for debug information.</li>
 629 </ul>
 630
 631 </div>
 632
 633 <!-- ======================================================================= -->
 634 <div class="doc_subsection">
 635   <a name="arm-be">Known problems with the ARM back-end</a>
 636 </div>
 637
 638 <div class="doc_text">
 639
 640 <ul>
 641 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
 642 processors, thumb programs can crash or produce wrong
 643 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
 644 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
 645 </li>
 646 <li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
 647  execute
 648 programs compiled with LLVM.  Please use more recent versions of QEMU.</li>
 649 </ul>
 650
 651 </div>
 652
 653 <!-- ======================================================================= -->
 654 <div class="doc_subsection">
 655   <a name="sparc-be">Known problems with the SPARC back-end</a>
 656 </div>
 657
 658 <div class="doc_text">
 659
 660 <ul>
 661 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
 662     support the 64-bit SPARC ABI (-m64).</li>
 663 </ul>
 664
 665 </div>
 666
 667 <!-- ======================================================================= -->
 668 <div class="doc_subsection">
 669   <a name="mips-be">Known problems with the MIPS back-end</a>
 670 </div>
 671
 672 <div class="doc_text">
 673
 674 <ul>
 675 <li>The O32 ABI is not fully supported.</li>
 676 <li>64-bit MIPS targets are not supported yet.</li>
 677 </ul>
 678
 679 </div>
 680
 681 <!-- ======================================================================= -->
 682 <div class="doc_subsection">
 683   <a name="alpha-be">Known problems with the Alpha back-end</a>
 684 </div>
 685
 686 <div class="doc_text">
 687
 688 <ul>
 689
 690 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
 691 appropriate nops inserted to ensure restartability.</li>
 692
 693 </ul>
 694 </div>
 695
 696 <!-- ======================================================================= -->
 697 <div class="doc_subsection">
 698   <a name="c-be">Known problems with the C back-end</a>
 699 </div>
 700
 701 <div class="doc_text">
 702
 703 <ul>
 704 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
 705     inline assembly code</a>.</li>
 706 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
 707     C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
 708     C++ code compiled with <tt>llc</tt> or native compilers.</li>
 709 <li>The C backend does not support all exception handling constructs.</li>
 710 <li>The C backend does not support arbitrary precision integers.</li>
 711 </ul>
 712
 713 </div>
 714
 715
 716 <!-- ======================================================================= -->
 717 <div class="doc_subsection">
 718   <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
 719 </div>
 720
 721 <div class="doc_text">
 722
 723 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
 724 Optimization</a> on most platforms "out-of-the-box".  Please inquire on the
 725 LLVMdev mailing list if you are interested.</p>
 726
 727 <p>The only major language feature of GCC not supported by llvm-gcc is
 728     the <tt>__builtin_apply</tt> family of builtins.   However, some extensions
 729     are only supported on some targets.  For example, trampolines are only
 730     supported on some targets (these are used when you take the address of a
 731     nested function).</p>
 732
 733 <p>If you run into GCC extensions which are not supported, please let us know.
 734 </p>
 735
 736 </div>
 737
 738 <!-- ======================================================================= -->
 739 <div class="doc_subsection">
 740   <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
 741 </div>
 742
 743 <div class="doc_text">
 744
 745 <p>The C++ front-end is considered to be fully
 746 tested and works for a number of non-trivial programs, including LLVM
 747 itself, Qt, Mozilla, etc.</p>
 748
 749 <ul>
 750 <li>Exception handling works well on the X86 and PowerPC targets. Currently
 751   only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
 752 </ul>
 753
 754 </div>
 755
 756 <!-- ======================================================================= -->
 757 <div class="doc_subsection">
 758   <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
 759 </div>
 760
 761 <div class="doc_text">
 762 <ul>
 763 <li>Fortran support generally works, but there are still several unresolved bugs
 764     in Bugzilla.  Please see the tools/gfortran component for details.</li>
 765 </ul>
 766 </div>
 767
 768 <!-- ======================================================================= -->
 769 <div class="doc_subsection">
 770   <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
 771 </div>
 772
 773 <div class="doc_text">
 774 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
 775 technology, and problems should be expected.
 776 <ul>
 777 <li>The Ada front-end currently only builds on X86-32.  This is mainly due
 778 to lack of trampoline support (pointers to nested functions) on other platforms.
 779 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
 780 which does support trampolines.</li>
 781 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
 782 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
 783 exception handling, which is used internally by the compiler.
 784 Workaround: configure with --disable-bootstrap.</li>
 785 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
 786 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
 787 (c380004 also fails with gcc-4.2 mainline).
 788 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
 789 causes the compiler to go into an infinite loop, using up all system memory.</li>
 790 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
 791 <li>The -E binder option (exception backtraces)
 792 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
 793 crashing if an exception is raised.  Workaround: do not use -E.</li>
 794 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
 795 or finish at a non-byte offset</a> in a record.  Workaround: do not pack records
 796 or use representation clauses that result in a field of a non-discrete type
 797 starting or finishing in the middle of a byte.</li>
 798 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
 799 'main' as generated by the Ada binder to be invalid</a>.
 800 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
 801 <tt>envp</tt> rather than integers.</li>
 802 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
 803 ignored</a>.</li>
 804 </ul>
 805 </div>
 806
 807 <!-- *********************************************************************** -->
 808 <div class="doc_section">
 809   <a name="additionalinfo">Additional Information</a>
 810 </div>
 811 <!-- *********************************************************************** -->
 812
 813 <div class="doc_text">
 814
 815 <p>A wide variety of additional information is available on the <a
 816 href="http://llvm.org">LLVM web page</a>, in particular in the <a
 817 href="http://llvm.org/docs/">documentation</a> section.  The web page also
 818 contains versions of the API documentation which is up-to-date with the
 819 Subversion version of the source code.
 820 You can access versions of these documents specific to this release by going
 821 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
 822
 823 <p>If you have any questions or comments about LLVM, please feel free to contact
 824 us via the <a href="http://llvm.org/docs/#maillist"> mailing
 825 lists</a>.</p>
 826
 827 </div>
 828
 829 <!-- *********************************************************************** -->
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