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>AuroraUX / FreeBSD & OpenBSD Toolchain support.</li>
 123 <li>Many many bugs are fixed and many features have been added.</li>
 124 </ul>
 125 </div>
 126
 127 <!--=========================================================================-->
 128 <div class="doc_subsection">
 129 <a name="clangsa">Clang Static Analyzer</a>
 130 </div>
 131
 132 <div class="doc_text">
 133
 134 <p>Previously announced in the 2.4 LLVM release, the Clang project also
 135 includes an early stage static source code analysis tool for <a
 136 href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
 137 in C and Objective-C programs. The tool performs a growing set of checks to find
 138 bugs that occur on a specific path within a program.</p>
 139
 140 <p>In the LLVM 2.6 time-frame there have been many significant improvements to
 141 XYZ.</p>
 142
 143 <p>The set of checks performed by the static analyzer continues to expand, and
 144 future plans for the tool include full source-level inter-procedural analysis
 145 and deeper checks such as buffer overrun detection. There are many opportunities
 146 to extend and enhance the static analyzer, and anyone interested in working on
 147 this project is encouraged to get involved!</p>
 148
 149 </div>
 150
 151 <!--=========================================================================-->
 152 <div class="doc_subsection">
 153 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
 154 </div>
 155
 156 <div class="doc_text">
 157 <p>
 158 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
 159 a JVM and a CLI Virtual Machines (Microsoft .NET is an
 160 implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
 161
 162 <p>Following LLVM 2.6, VMKit has its XYZ release that you can find on its
 163 <a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
 164 bug fixes, cleanup and new features. The major changes are:</p>
 165
 166 <ul>
 167
 168 <li>Something wonderful!</li>
 169
 170 </ul>
 171 </div>
 172
 173 <!-- *********************************************************************** -->
 174 <div class="doc_section">
 175   <a name="externalproj">External Projects Using LLVM 2.6</a>
 176 </div>
 177 <!-- *********************************************************************** -->
 178
 179 <!--=========================================================================-->
 180 <div class="doc_subsection">
 181 <a name="pure">Pure</a>
 182 </div>
 183
 184 <div class="doc_text">
 185 <p>
 186 <a href="http://pure-lang.googlecode.com/">Pure</a>
 187 is an algebraic/functional programming language based on term rewriting.
 188 Programs are collections of equations which are used to evaluate expressions in
 189 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
 190 lexical closures, a hygienic macro system (also based on term rewriting),
 191 built-in list and matrix support (including list and matrix comprehensions) and
 192 an easy-to-use C interface. The interpreter uses LLVM as a backend to
 193  JIT-compile Pure programs to fast native code.</p>
 194
 195 <p>In addition to the usual algebraic data structures, Pure also has
 196 MATLAB-style matrices in order to support numeric computations and signal
 197 processing in an efficient way. Pure is mainly aimed at mathematical
 198 applications right now, but it has been designed as a general purpose language.
 199 The dynamic interpreter environment and the C interface make it possible to use
 200 it as a kind of functional scripting language for many application areas.
 201 </p>
 202 </div>
 203
 204
 205 <!--=========================================================================-->
 206 <div class="doc_subsection">
 207 <a name="ldc">LLVM D Compiler</a>
 208 </div>
 209
 210 <div class="doc_text">
 211 <p>
 212 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
 213 the D Programming Language using the LLVM optimizer and code generator.
 214 The LDC project works great with the LLVM 2.6 release.  General improvements in
 215 this
 216 cycle have included new inline asm constraint handling, better debug info
 217 support, general bugfixes, and better x86-64 support.  This has allowed
 218 some major improvements in LDC, getting us much closer to being as
 219 fully featured as the original DMD compiler from DigitalMars.
 220 </p>
 221 </div>
 222
 223 <!--=========================================================================-->
 224 <div class="doc_subsection">
 225 <a name="RoadsendPHP">Roadsend PHP</a>
 226 </div>
 227
 228 <div class="doc_text">
 229 <p><a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
 230 source implementation of the PHP programming
 231 language that uses LLVM for its optimizer, JIT, and static compiler. This is a
 232 reimplementation of an earlier project that is now based on LLVM.</p>
 233 </div>
 234
 235 <!--=========================================================================-->
 236 <div class="doc_subsection">
 237 <a name="Unladen Swallow">Unladen Swallow</a>
 238 </div>
 239
 240 <div class="doc_text">
 241 <p><a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
 242 branch of <a href="http://python.org/">Python</a> intended to be fully
 243 compatible and significantly faster.  It uses LLVM's optimization passes and JIT
 244 compiler.</p>
 245 </div>
 246
 247 <!--=========================================================================-->
 248 <div class="doc_subsection">
 249 <a name="Rubinius">Rubinius</a>
 250 </div>
 251
 252 <div class="doc_text">
 253 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is a new virtual
 254 machine for Ruby. It leverages LLVM to dynamically compile Ruby code down to
 255 machine code using LLVM's JIT.</p>
 256 </div>
 257
 258
 259 <!-- *********************************************************************** -->
 260 <div class="doc_section">
 261   <a name="whatsnew">What's New in LLVM 2.6?</a>
 262 </div>
 263 <!-- *********************************************************************** -->
 264
 265 <div class="doc_text">
 266
 267 <p>This release includes a huge number of bug fixes, performance tweaks, and
 268 minor improvements.  Some of the major improvements and new features are listed
 269 in this section.
 270 </p>
 271 </div>
 272
 273 <!--=========================================================================-->
 274 <div class="doc_subsection">
 275 <a name="majorfeatures">Major New Features</a>
 276 </div>
 277
 278 <div class="doc_text">
 279
 280 <p>LLVM 2.6 includes several major new capabilities:</p>
 281
 282 <ul>
 283 <li>Something wonderful!</li>
 284 <li>LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005 programming language.</li>
 285 </ul>
 286
 287 </div>
 288
 289
 290 <!--=========================================================================-->
 291 <div class="doc_subsection">
 292 <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
 293 </div>
 294
 295 <div class="doc_text">
 296
 297 <p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
 298 front-ends and driver with the LLVM optimizer and code generator.  It currently
 299 includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
 300
 301 <ul>
 302 <li>Something wonderful!</li>
 303 </ul>
 304
 305 </div>
 306
 307
 308 <!--=========================================================================-->
 309 <div class="doc_subsection">
 310 <a name="coreimprovements">LLVM IR and Core Improvements</a>
 311 </div>
 312
 313 <div class="doc_text">
 314 <p>LLVM IR has several new features that are used by our existing front-ends and
 315 can be useful if you are writing a front-end for LLVM:</p>
 316
 317 <ul>
 318 <li>Something wonderful!</li>
 319 </ul>
 320
 321 </div>
 322
 323 <!--=========================================================================-->
 324 <div class="doc_subsection">
 325 <a name="optimizer">Optimizer Improvements</a>
 326 </div>
 327
 328 <div class="doc_text">
 329
 330 <p>In addition to a large array of bug fixes and minor performance tweaks, this
 331 release includes a few major enhancements and additions to the optimizers:</p>
 332
 333 <ul>
 334
 335 <li>Something wonderful!</li>
 336
 337 </ul>
 338
 339 </div>
 340
 341 <!--=========================================================================-->
 342 <div class="doc_subsection">
 343 <a name="codegen">Target Independent Code Generator Improvements</a>
 344 </div>
 345
 346 <div class="doc_text">
 347
 348 <p>We have put a significant amount of work into the code generator
 349 infrastructure, which allows us to implement more aggressive algorithms and make
 350 it run faster:</p>
 351
 352 <ul>
 353
 354 <li>Something wonderful!</li>
 355 </ul>
 356 </div>
 357
 358 <!--=========================================================================-->
 359 <div class="doc_subsection">
 360 <a name="x86">X86-32 and X86-64 Target Improvements</a>
 361 </div>
 362
 363 <div class="doc_text">
 364 <p>New features of the X86 target include:
 365 </p>
 366
 367 <ul>
 368
 369 <li>Something wonderful!</li>
 370 </ul>
 371
 372 </div>
 373
 374 <!--=========================================================================-->
 375 <div class="doc_subsection">
 376 <a name="pic16">PIC16 Target Improvements</a>
 377 </div>
 378
 379 <div class="doc_text">
 380 <p>New features of the PIC16 target include:
 381 </p>
 382
 383 <ul>
 384 <li>Something wonderful!</li>
 385 </ul>
 386
 387 <p>Things not yet supported:</p>
 388
 389 <ul>
 390 <li>Floating point.</li>
 391 <li>Passing/returning aggregate types to and from functions.</li>
 392 <li>Variable arguments.</li>
 393 <li>Indirect function calls.</li>
 394 <li>Interrupts/programs.</li>
 395 <li>Debug info.</li>
 396 </ul>
 397
 398 </div>
 399
 400 <!--=========================================================================-->
 401 <div class="doc_subsection">
 402 <a name="ARM">ARM Target Improvements</a>
 403 </div>
 404
 405 <div class="doc_text">
 406 <p>New features of the ARM target include:
 407 </p>
 408
 409 <ul>
 410
 411 <li>Preliminary support for processors, such as the Cortex-A8 and Cortex-A9,
 412 that implement version v7-A of the ARM architecture.  The ARM backend now
 413 supports both the Thumb2 and Advanced SIMD (Neon) instruction sets. The
 414 AAPCS-VFP "hard float" calling conventions are also supported with the
 415 <tt>-float-abi=hard</tt> flag. These features are still somewhat experimental
 416 and subject to change. The Neon intrinsics, in particular, may change in future
 417 releases of LLVM.
 418 </li>
 419 </ul>
 420
 421 </div>
 422
 423
 424 <!--=========================================================================-->
 425 <div class="doc_subsection">
 426 <a name="llvmc">Improvements in LLVMC</a>
 427 </div>
 428
 429 <div class="doc_text">
 430 <p>New features include:</p>
 431
 432 <ul>
 433 <li>Something wonderful!</li>
 434 </ul>
 435
 436 </div>
 437
 438
 439 <!--=========================================================================-->
 440 <div class="doc_subsection">
 441 <a name="changes">Major Changes and Removed Features</a>
 442 </div>
 443
 444 <div class="doc_text">
 445
 446 <p>If you're already an LLVM user or developer with out-of-tree changes based
 447 on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading
 448 from the previous release.</p>
 449
 450 <ul>
 451
 452 <li>Something horrible!</li>
 453
 454 </ul>
 455
 456
 457 <p>In addition, many APIs have changed in this release.  Some of the major LLVM
 458 API changes are:</p>
 459
 460 <ul>
 461 <li>LLVM's global uniquing tables for <tt>Type</tt>s and <tt>Constant</tt>s have
 462     been privatized into members of an <tt>LLVMContext</tt>.  A number of APIs
 463     now take an <tt>LLVMContext</tt> as a parameter.  To smooth the transition
 464     for clients that will only ever use a single context, the new
 465     <tt>getGlobalContext()</tt> API can be used to access a default global
 466     context which can be passed in any and all cases where a context is
 467     required.
 468 <li>The <tt>getABITypeSize</tt> methods are now called <tt>getAllocSize</tt>.</li>
 469 <li>The <tt>Add</tt>, <tt>Sub</tt>, and <tt>Mul</tt> operators are no longer
 470     overloaded for floating-point types. Floating-point addition, subtraction,
 471     and multiplication are now represented with new operators <tt>FAdd</tt>,
 472     <tt>FSub</tt>, and <tt>FMul</tt>. In the <tt>IRBuilder</tt> API,
 473     <tt>CreateAdd</tt>, <tt>CreateSub</tt>, <tt>CreateMul</tt>, and
 474     <tt>CreateNeg</tt> should only be used for integer arithmetic now;
 475     <tt>CreateFAdd</tt>, <tt>CreateFSub</tt>, <tt>CreateFMul</tt>, and
 476     <tt>CreateFNeg</tt> should now be used for floating-point arithmetic.</li>
 477 <li>The DynamicLibrary class can no longer be constructed, its functionality has
 478     moved to static member functions.</li>
 479 <li><tt>raw_fd_ostream</tt>'s constructor for opening a given filename now
 480     takes an extra <tt>Force</tt> argument. If <tt>Force</tt> is set to
 481     <tt>false</tt>, an error will be reported if a file with the given name
 482     already exists. If <tt>Force</tt> is set to <tt>true</tt>, the file will
 483     be silently truncated (which is the behavior before this flag was
 484     added).</li>
 485 <li><tt>SCEVHandle</tt> no longer exists, because reference counting is no
 486 longer done for <tt>SCEV*</tt> objects, instead <tt>const SCEV*</tt> should be
 487 used.</li>
 488
 489 <li>Many APIs, notably <tt>llvm::Value</tt>, now use the <tt>StringRef</tt>
 490 and <tt>Twine</tt> classes instead of passing <tt>const char*</tt>
 491 or <tt>std::string</tt>, as described in
 492 the <a href="ProgrammersManual.html#string_apis">Programmer's Manual</a>. Most
 493 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:
 494   <ul>
 495     <li><tt>getNameStr()</tt> is still available, and matches the old
 496       behavior. Replacing <tt>getName()</tt> calls with this is an safe option,
 497       although more efficient alternatives are now possible.</li>
 498
 499     <li>If you were just relying on <tt>getName()</tt> being able to be sent to
 500       a <tt>std::ostream</tt>, consider migrating
 501       to <tt>llvm::raw_ostream</tt>.</li>
 502
 503     <li>If you were using <tt>getName().c_str()</tt> to get a <tt>const
 504         char*</tt> pointer to the name, you can use <tt>getName().data()</tt>.
 505         Note that this string (as before), may not be the entire name if the
 506         name containts embedded null characters.</li>
 507
 508     <li>If you were using operator plus on the result of <tt>getName()</tt> and
 509       treating the result as an <tt>std::string</tt>, you can either
 510       uses <tt>Twine::str</tt> to get the result as an <tt>std::string</tt>, or
 511       could move to a <tt>Twine</tt> based design.</li>
 512
 513     <li><tt>isName()</tt> should be replaced with comparison
 514       against <tt>getName()</tt> (this is now efficient).
 515   </ul>
 516 </li>
 517
 518 <li>The registration interfaces for backend Targets has changed (what was
 519 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:
 520   <ul>
 521     <li><tt>TargetMachineRegistry</tt> has been renamed
 522       to <tt>TargetRegistry</tt>.</li>
 523
 524     <li>Clients should move to using the <tt>TargetRegistry::lookupTarget()</tt>
 525       function to find targets.</li>
 526   </ul>
 527 </li>
 528
 529 <li>llvm-dis now fails if output file exists, instead of dumping to stdout.
 530 FIXME: describe any other tool changes due to the raw_fd_ostream change.  FIXME:
 531 This is not an API change, maybe there should be a tool changes section?</li>
 532 <li>temporarely due to Context API change passes should call doInitialization()
 533 method of the pass they inherit from, otherwise Context is NULL.
 534 FIXME: remove this entry when this is no longer needed.<li>
 535 </ul>
 536
 537 </div>
 538
 539
 540
 541 <!-- *********************************************************************** -->
 542 <div class="doc_section">
 543   <a name="portability">Portability and Supported Platforms</a>
 544 </div>
 545 <!-- *********************************************************************** -->
 546
 547 <div class="doc_text">
 548
 549 <p>LLVM is known to work on the following platforms:</p>
 550
 551 <ul>
 552 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
 553 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like systems).</li>
 554 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
 555 and 64-bit modes.</li>
 556 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
 557 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
 558     support is available for native builds with Visual C++).</li>
 559 <li>Sun UltraSPARC workstations running Solaris 10.</li>
 560 <li>Alpha-based machines running Debian GNU/Linux.</li>
 561 </ul>
 562
 563 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
 564 to the machine and operating system on which it is built.  However, minor
 565 porting may be required to get LLVM to work on new platforms.  We welcome your
 566 portability patches and reports of successful builds or error messages.</p>
 567
 568 </div>
 569
 570 <!-- *********************************************************************** -->
 571 <div class="doc_section">
 572   <a name="knownproblems">Known Problems</a>
 573 </div>
 574 <!-- *********************************************************************** -->
 575
 576 <div class="doc_text">
 577
 578 <p>This section contains significant known problems with the LLVM system,
 579 listed by component.  If you run into a problem, please check the <a
 580 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
 581 there isn't already one.</p>
 582
 583 <ul>
 584 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
 585 using the stock GCC 3.x.x series 'out the box',
 586 See: <a href="#brokengcc">Broken versions of GCC and other tools</a>.
 587 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
 588 for x86/x64 has been made available from the third party AuroraUX Project
 589 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
 590 </ul>
 591
 592 </div>
 593
 594 <!-- ======================================================================= -->
 595 <div class="doc_subsection">
 596   <a name="experimental">Experimental features included with this release</a>
 597 </div>
 598
 599 <div class="doc_text">
 600
 601 <p>The following components of this LLVM release are either untested, known to
 602 be broken or unreliable, or are in early development.  These components should
 603 not be relied on, and bugs should not be filed against them, but they may be
 604 useful to some people.  In particular, if you would like to work on one of these
 605 components, please contact us on the <a
 606 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
 607
 608 <ul>
 609 <li>The MSIL, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
 610 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
 611     supported value for this option.</li>
 612 </ul>
 613
 614 </div>
 615
 616 <!-- ======================================================================= -->
 617 <div class="doc_subsection">
 618   <a name="x86-be">Known problems with the X86 back-end</a>
 619 </div>
 620
 621 <div class="doc_text">
 622
 623 <ul>
 624   <li>The X86 backend does not yet support
 625     all <a href="http://llvm.org/PR879">inline assembly that uses the X86
 626     floating point stack</a>.  It supports the 'f' and 't' constraints, but not
 627     'u'.</li>
 628   <li>The X86 backend generates inefficient floating point code when configured
 629     to generate code for systems that don't have SSE2.</li>
 630   <li>Win64 code generation wasn't widely tested. Everything should work, but we
 631     expect small issues to happen. Also, llvm-gcc cannot build the mingw64
 632     runtime currently due
 633     to <a href="http://llvm.org/PR2255">several</a>
 634     <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
 635     the
 636     'u' inline assembly constraint and for X87 floating point inline assembly.</li>
 637   <li>The X86-64 backend does not yet support the LLVM IR instruction
 638       <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
 639       argument constructs on X86-64 by lowering them manually.</li>
 640 </ul>
 641
 642 </div>
 643
 644 <!-- ======================================================================= -->
 645 <div class="doc_subsection">
 646   <a name="ppc-be">Known problems with the PowerPC back-end</a>
 647 </div>
 648
 649 <div class="doc_text">
 650
 651 <ul>
 652 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
 653 compilation, and lacks support for debug information.</li>
 654 </ul>
 655
 656 </div>
 657
 658 <!-- ======================================================================= -->
 659 <div class="doc_subsection">
 660   <a name="arm-be">Known problems with the ARM back-end</a>
 661 </div>
 662
 663 <div class="doc_text">
 664
 665 <ul>
 666 <li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
 667 and not well tested.  Some features may not work at all, and the code quality
 668 may be poor in some cases.</li>
 669 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
 670 processors, thumb programs can crash or produce wrong
 671 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
 672 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
 673 </li>
 674 <li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
 675  execute
 676 programs compiled with LLVM.  Please use more recent versions of QEMU.</li>
 677 </ul>
 678
 679 </div>
 680
 681 <!-- ======================================================================= -->
 682 <div class="doc_subsection">
 683   <a name="sparc-be">Known problems with the SPARC back-end</a>
 684 </div>
 685
 686 <div class="doc_text">
 687
 688 <ul>
 689 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
 690     support the 64-bit SPARC ABI (-m64).</li>
 691 </ul>
 692
 693 </div>
 694
 695 <!-- ======================================================================= -->
 696 <div class="doc_subsection">
 697   <a name="mips-be">Known problems with the MIPS back-end</a>
 698 </div>
 699
 700 <div class="doc_text">
 701
 702 <ul>
 703 <li>The O32 ABI is not fully supported.</li>
 704 <li>64-bit MIPS targets are not supported yet.</li>
 705 </ul>
 706
 707 </div>
 708
 709 <!-- ======================================================================= -->
 710 <div class="doc_subsection">
 711   <a name="alpha-be">Known problems with the Alpha back-end</a>
 712 </div>
 713
 714 <div class="doc_text">
 715
 716 <ul>
 717
 718 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
 719 appropriate nops inserted to ensure restartability.</li>
 720
 721 </ul>
 722 </div>
 723
 724 <!-- ======================================================================= -->
 725 <div class="doc_subsection">
 726   <a name="c-be">Known problems with the C back-end</a>
 727 </div>
 728
 729 <div class="doc_text">
 730
 731 <ul>
 732 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
 733     inline assembly code</a>.</li>
 734 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
 735     C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
 736     C++ code compiled with <tt>llc</tt> or native compilers.</li>
 737 <li>The C backend does not support all exception handling constructs.</li>
 738 <li>The C backend does not support arbitrary precision integers.</li>
 739 </ul>
 740
 741 </div>
 742
 743
 744 <!-- ======================================================================= -->
 745 <div class="doc_subsection">
 746   <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
 747 </div>
 748
 749 <div class="doc_text">
 750
 751 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
 752 Optimization</a> on most platforms "out-of-the-box".  Please inquire on the
 753 LLVMdev mailing list if you are interested.</p>
 754
 755 <p>The only major language feature of GCC not supported by llvm-gcc is
 756     the <tt>__builtin_apply</tt> family of builtins.   However, some extensions
 757     are only supported on some targets.  For example, trampolines are only
 758     supported on some targets (these are used when you take the address of a
 759     nested function).</p>
 760
 761 <p>If you run into GCC extensions which are not supported, please let us know.
 762 </p>
 763
 764 </div>
 765
 766 <!-- ======================================================================= -->
 767 <div class="doc_subsection">
 768   <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
 769 </div>
 770
 771 <div class="doc_text">
 772
 773 <p>The C++ front-end is considered to be fully
 774 tested and works for a number of non-trivial programs, including LLVM
 775 itself, Qt, Mozilla, etc.</p>
 776
 777 <ul>
 778 <li>Exception handling works well on the X86 and PowerPC targets. Currently
 779   only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
 780 </ul>
 781
 782 </div>
 783
 784 <!-- ======================================================================= -->
 785 <div class="doc_subsection">
 786   <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
 787 </div>
 788
 789 <div class="doc_text">
 790 <ul>
 791 <li>Fortran support generally works, but there are still several unresolved bugs
 792     in Bugzilla.  Please see the tools/gfortran component for details.</li>
 793 </ul>
 794 </div>
 795
 796 <!-- ======================================================================= -->
 797 <div class="doc_subsection">
 798   <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
 799 </div>
 800
 801 <div class="doc_text">
 802 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
 803 technology, and problems should be expected.
 804 <ul>
 805 <li>The Ada front-end currently only builds on X86-32.  This is mainly due
 806 to lack of trampoline support (pointers to nested functions) on other platforms.
 807 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
 808 which does support trampolines.</li>
 809 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
 810 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
 811 exception handling, which is used internally by the compiler.
 812 Workaround: configure with --disable-bootstrap.</li>
 813 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
 814 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
 815 (c380004 also fails with gcc-4.2 mainline).
 816 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
 817 causes the compiler to go into an infinite loop, using up all system memory.</li>
 818 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
 819 <li>The -E binder option (exception backtraces)
 820 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
 821 crashing if an exception is raised.  Workaround: do not use -E.</li>
 822 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
 823 or finish at a non-byte offset</a> in a record.  Workaround: do not pack records
 824 or use representation clauses that result in a field of a non-discrete type
 825 starting or finishing in the middle of a byte.</li>
 826 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
 827 'main' as generated by the Ada binder to be invalid</a>.
 828 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
 829 <tt>envp</tt> rather than integers.</li>
 830 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
 831 ignored</a>.</li>
 832 </ul>
 833 </div>
 834
 835 <!-- *********************************************************************** -->
 836 <div class="doc_section">
 837   <a name="additionalinfo">Additional Information</a>
 838 </div>
 839 <!-- *********************************************************************** -->
 840
 841 <div class="doc_text">
 842
 843 <p>A wide variety of additional information is available on the <a
 844 href="http://llvm.org">LLVM web page</a>, in particular in the <a
 845 href="http://llvm.org/docs/">documentation</a> section.  The web page also
 846 contains versions of the API documentation which is up-to-date with the
 847 Subversion version of the source code.
 848 You can access versions of these documents specific to this release by going
 849 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
 850
 851 <p>If you have any questions or comments about LLVM, please feel free to contact
 852 us via the <a href="http://llvm.org/docs/#maillist"> mailing
 853 lists</a>.</p>
 854
 855 </div>
 856
 857 <!-- *********************************************************************** -->
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