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7 <title>LLVM 1.8 Release Notes</title>
11 <div class="doc_title">LLVM 1.8 Release Notes</div>
14 <li><a href="#intro">Introduction</a></li>
15 <li><a href="#whatsnew">What's New?</a></li>
16 <li><a href="GettingStarted.html">Installation Instructions</a></li>
17 <li><a href="#portability">Portability and Supported Platforms</a></li>
18 <li><a href="#knownproblems">Known Problems</a>
19 <li><a href="#additionalinfo">Additional Information</a></li>
22 <div class="doc_author">
23 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
26 <!-- *********************************************************************** -->
27 <div class="doc_section">
28 <a name="intro">Introduction</a>
30 <!-- *********************************************************************** -->
32 <div class="doc_text">
34 <p>This document contains the release notes for the LLVM compiler
35 infrastructure, release 1.8. Here we describe the status of LLVM, including any
36 known problems and major improvements from the previous release. The most
37 up-to-date version of this document (corresponding to LLVM CVS) can be found
39 href="http://llvm.org/releases/">LLVM releases web site</a>. If you are
40 not reading this on the LLVM web pages, you should probably go there because
41 this document may be updated after the release.</p>
43 <p>For more information about LLVM, including information about the latest
44 release, please check out the <a href="http://llvm.org/">main LLVM
45 web site</a>. If you have questions or comments, the <a
46 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
47 list</a> is a good place to send them.</p>
49 <p>Note that if you are reading this file from CVS or the main LLVM web page,
50 this document applies to the <i>next</i> release, not the current one. To see
51 the release notes for the current or previous releases, see the <a
52 href="http://llvm.org/releases/">releases page</a>.</p>
56 <!-- *********************************************************************** -->
57 <div class="doc_section">
58 <a name="whatsnew">What's New?</a>
60 <!-- *********************************************************************** -->
62 <div class="doc_text">
64 <p>This is the ninth public release of the LLVM Compiler Infrastructure. This
65 release incorporates a large number of enhancements and new features,
66 including DWARF debugging support (C and C++ on Darwin/PPC), improved inline
67 assembly support, a new <a href="http://llvm.org/nightlytest/">nightly
68 tester</a>, llvm-config enhancements, many bugs
69 fixed, and performance and compile time improvements.
74 <!--=========================================================================-->
75 <div class="doc_subsection">
76 <a name="newfeatures">New Features in LLVM 1.8</a>
79 <!--_________________________________________________________________________-->
80 <div class="doc_subsubsection"><a name="dwarf">DWARF debugging
83 <div class="doc_text">
85 <p>The llvm-gcc4 C front-end now generates debugging info for C and C++. This
86 information is propagated through the compiler and the code generator can
87 currently produce DWARF debugging information from it. DWARF is a standard
88 debugging format used on many platforms, but currently LLVM only includes
89 target support for Mac OS X targets for the 1.8 release.
94 <!--_________________________________________________________________________-->
95 <div class="doc_subsubsection"><a name="inlineasm">Inline Assembly
98 <div class="doc_text">
100 <p>Inline assembly support is substantially improved in LLVM 1.8 over LLVM 1.7.
101 Many unsupported features are now supported, and inline asm support in the X86
102 backend is far better. llvm-gcc4 now supports global register variables as
107 <!--_________________________________________________________________________-->
108 <div class="doc_subsubsection"><a name="loopopt">Loop Optimizer Improvements</a></div>
110 <div class="doc_text">
112 <p>The loop optimizer passes now uses "Loop-Closed SSA Form", which makes it
113 easier to update SSA form as loop transformations change the code. An
114 immediate benefit of this is that the loop unswitching pass can now unswitch
120 <!--_________________________________________________________________________-->
121 <div class="doc_subsubsection"><a name="jumptab">Jump Table Support for Switches
124 <div class="doc_text">
126 <p>The code generator now lowers switch statements to jump tables, providing
127 significant performance boosts for applications (e.g. interpreters) whose
128 performance is highly correlated to switch statement performance.</p>
132 <!--_________________________________________________________________________-->
133 <div class="doc_subsubsection"><a name="jitrelease">Deallocation of JIT'd
137 <div class="doc_text">
139 <p>The LLVM JIT now allows clients to deallocate machine code JIT'd to its code
140 buffer. This is important for long living applications that depend on the JIT.
145 <!--_________________________________________________________________________-->
146 <div class="doc_subsubsection"><a name="other">Other Improvements</a></div>
148 <div class="doc_text">
150 <p>This release includes many other improvements, including improvements to
151 the optimizers and code generators (improving the generated code) changes to
152 speed up the compiler in many ways (improving algorithms and fine tuning
153 code), and changes to reduce the code size of the compiler itself.</p>
155 <p>More specific changes include:</p>
158 <li>LLVM 1.8 includes an initial ARM backend. This backend is in early
159 development stages.</li>
160 <li>LLVM 1.8 now includes significantly better support for mingw and
162 <li>The <a href="CommandGuide/html/llvm-config.html">llvm-config</a> tool is
163 now built by default and has several new features.</li>
164 <li>The X86 and PPC backends now use the correct platform ABI for passing
165 vectors as arguments to functions.</li>
166 <li>The X86 backend now includes support for the Microsoft ML assembler
168 <li>The PowerPC backend now pattern matches the 'rlwimi' instruction more
170 <li>Most of LLVM is now built with "-pedantic", ensuring better portability
171 to more C++ Compilers.</li>
172 <li>The PowerPC backend now includes initial 64-bit support. The JIT is not
173 complete, and the static compiler has a couple of known bugs, but support
174 is mostly in place. LLVM 1.9 will include completed PPC-64 support. </li>
179 <!--=========================================================================-->
180 <div class="doc_subsection">
181 <a name="changes">Significant Changes in LLVM 1.8</a>
184 <div class="doc_text">
186 <li>The LLVM "SparcV9" backend (deprecated in LLVM 1.7) has been removed in
187 LLVM 1.8. The LLVM "Sparc" backend replaces it.</li>
188 <li>The --version option now prints more useful information, including the
189 build configuration for the tool.</li>
194 <!-- *********************************************************************** -->
195 <div class="doc_section">
196 <a name="portability">Portability and Supported Platforms</a>
198 <!-- *********************************************************************** -->
200 <div class="doc_text">
202 <p>LLVM is known to work on the following platforms:</p>
205 <li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
206 (and probably other unix-like systems).</li>
207 <li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
208 <li>Sun UltraSPARC workstations running Solaris 8.</li>
209 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
210 support is available for native builds with Visual C++).</li>
211 <li>PowerPC and X86-based Mac OS X systems, running 10.2 and above.</li>
212 <li>Alpha-based machines running Debian GNU/Linux.</li>
213 <li>Itanium-based machines running Linux and HP-UX.</li>
216 <p>The core LLVM infrastructure uses
217 <a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
218 to the machine and operating system on which it is built. However, minor
219 porting may be required to get LLVM to work on new platforms. We welcome your
220 portability patches and reports of successful builds or error messages.</p>
224 <!-- *********************************************************************** -->
225 <div class="doc_section">
226 <a name="knownproblems">Known Problems</a>
228 <!-- *********************************************************************** -->
230 <div class="doc_text">
232 <p>This section contains all known problems with the LLVM system, listed by
233 component. As new problems are discovered, they will be added to these
234 sections. If you run into a problem, please check the <a
235 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
236 there isn't already one.</p>
240 <!-- ======================================================================= -->
241 <div class="doc_subsection">
242 <a name="experimental">Experimental features included with this release</a>
245 <div class="doc_text">
247 <p>The following components of this LLVM release are either untested, known to
248 be broken or unreliable, or are in early development. These components should
249 not be relied on, and bugs should not be filed against them, but they may be
250 useful to some people. In particular, if you would like to work on one of these
251 components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
254 <li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in in a
256 <li>The IA64 code generator is experimental.</li>
257 <li>The Alpha JIT is experimental.</li>
258 <li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
259 <tt>-filetype</tt> llc option.</li>
264 <!-- ======================================================================= -->
265 <div class="doc_subsection">
266 <a name="build">Known problems with the Build System</a>
269 <div class="doc_text">
277 <!-- ======================================================================= -->
278 <div class="doc_subsection">
279 <a name="core">Known problems with the LLVM Core</a>
282 <div class="doc_text">
285 <li>In the JIT, <tt>dlsym()</tt> on a symbol compiled by the JIT will not
290 <!-- ======================================================================= -->
291 <div class="doc_subsection">
292 <a name="c-fe">Known problems with the C front-end</a>
295 <!-- _______________________________________________________________________ -->
296 <div class="doc_subsubsection">Bugs</div>
298 <div class="doc_text">
301 llvm-gcc3 has many significant problems that are fixed by llvm-gcc4.
302 Two major ones include:</p>
306 C99 variable sized arrays do not release stack memory when they go out of
307 scope. Thus, the following program may run out of stack space:
309 for (i = 0; i != 1000000; ++i) {
315 <li>With llvm-gcc3, Initialization of global union variables can only be done <a
316 href="http://llvm.org/PR162">with the largest union member</a>.</li>
320 <p>llvm-gcc4 is far more stable and produces better code than llvm-gcc3, but
321 does not currently support Link-Time-Optimization or C++ Exception Handling,
322 which llvm-gcc3 does.</p>
326 <!-- _______________________________________________________________________ -->
327 <div class="doc_subsubsection">
331 <div class="doc_text">
335 <li>"long double" is transformed by the front-end into "double". There is no
336 support for floating point data types of any size other than 32 and 64
339 <li>The following Unix system functionality has not been tested and may not
342 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
343 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
344 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
345 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
346 - These functions have not been tested.
349 <li>Although many GCC extensions are supported, some are not. In particular,
350 the following extensions are known to <b>not be</b> supported:
352 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
353 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>: As in Algol and Pascal, lexical scoping of functions.</li>
354 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
355 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.</li>
356 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
357 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html#Asm%20Labels">Asm Labels</a>: Specifying the assembler name to use for a C symbol.</li>
358 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html#Explicit%20Reg%20Vars">Explicit Reg Vars</a>: Defining variables residing in specified registers.</li>
359 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.</li>
360 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.</li>
361 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
362 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
365 <p>The following GCC extensions are <b>partially</b> supported. An ignored
366 attribute means that the LLVM compiler ignores the presence of the attribute,
367 but the code should still work. An unsupported attribute is one which is
368 ignored by the LLVM compiler and will cause a different interpretation of
372 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
373 Arrays whose length is computed at run time.<br>
374 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
376 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
378 Declaring that functions have no side effects or that they can never
381 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
382 <tt>noreturn</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
383 <tt>unused</tt>, <tt>used</tt>,
384 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
386 <b>Ignored:</b> <tt>noinline</tt>,
387 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
388 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
390 <b>Unsupported:</b> <tt>section</tt>, <tt>alias</tt>,
391 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
392 <tt>fastcall</tt>, all other target specific attributes</li>
394 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
395 Specifying attributes of variables.<br>
396 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
397 <tt>deprecated</tt>, <tt>transparent_union</tt>,
398 <tt>unused</tt>, <tt>used</tt>, <tt>weak</tt><br>
400 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
401 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
402 <tt>vector_size</tt>, <tt>dllimport</tt>,
403 <tt>dllexport</tt>, all target specific attributes.</li>
405 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
406 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
407 <tt>deprecated</tt>, <tt>may_alias</tt><br>
409 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
410 all target specific attributes.</li>
412 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
413 Other built-in functions.<br>
414 We support all builtins which have a C language equivalent (e.g.,
415 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
416 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
417 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt>
418 (currently ignored). We also support builtins for ISO C99 floating
419 point comparison macros (e.g., <tt>__builtin_islessequal</tt>),
420 <tt>__builtin_prefetch</tt>, <tt>__builtin_popcount[ll]</tt>,
421 <tt>__builtin_clz[ll]</tt>, and <tt>__builtin_ctz[ll]</tt>.</li>
424 <p>The following extensions <b>are</b> known to be supported:</p>
427 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">Labels as Values</a>: Getting pointers to labels and computed gotos.</li>
428 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
429 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.</li>
430 <li><a href="http://gcc.gnu.org/onlinedocs/gcc-3.4.0/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
431 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
432 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
433 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
434 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
435 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
436 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
437 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.</li>
438 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
439 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.</li>
440 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html#Pointer%20Arith">Pointer Arith</a>: Arithmetic on <code>void</code>-pointers and function pointers.</li>
441 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
442 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
443 or arrays as values.</li>
444 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
445 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast%20to%20Union">Cast to Union</a>: Casting to union type from any member of the union.</li>
446 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
447 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
448 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
449 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Comments.html#C_002b_002b-Comments">C++ Comments</a>: C++ comments are recognized.</li>
450 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
451 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Character-Escapes.html#Character%20Escapes">Character Escapes</a>: <code>\e</code> stands for the character <ESC>.</li>
452 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
453 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
454 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html#Alternate%20Keywords">Alternate Keywords</a>:<code>__const__</code>, <code>__asm__</code>, etc., for header files.</li>
455 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html#Incomplete%20Enums">Incomplete Enums</a>: <code>enum foo;</code>, with details to follow.</li>
456 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function%20Names">Function Names</a>: Printable strings which are the name of the current function.</li>
457 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html#Return%20Address">Return Address</a>: Getting the return or frame address of a function.</li>
458 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.</li>
459 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
464 <p>If you run into GCC extensions which have not been included in any of these
465 lists, please let us know (also including whether or not they work).</p>
469 <!-- ======================================================================= -->
470 <div class="doc_subsection">
471 <a name="c++-fe">Known problems with the C++ front-end</a>
474 <div class="doc_text">
476 <p>For this release, the C++ front-end is considered to be fully
477 tested and works for a number of non-trivial programs, including LLVM
482 <!-- _______________________________________________________________________ -->
483 <div class="doc_subsubsection">Bugs</div>
485 <div class="doc_text">
488 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
495 <!-- _______________________________________________________________________ -->
496 <div class="doc_subsubsection">
500 <div class="doc_text">
504 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
505 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
506 function and in the <tt>setjmp</tt> receiver function may not be run.
507 Objects in intervening stack frames will be destroyed, however (which is
508 better than most compilers).</li>
510 <li>The LLVM C++ front-end follows the <a
511 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
512 This document, which is not Itanium specific, specifies a standard for name
513 mangling, class layout, v-table layout, RTTI formats, and other C++
514 representation issues. Because we use this API, code generated by the LLVM
515 compilers should be binary compatible with machine code generated by other
516 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
517 <i>However</i>, the exception handling mechanism used by LLVM is very
518 different from the model used in the Itanium ABI, so <b>exceptions will not
519 interact correctly</b>. </li>
525 <!-- ======================================================================= -->
526 <div class="doc_subsection">
527 <a name="c-be">Known problems with the C back-end</a>
530 <div class="doc_text">
534 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
535 Analysis rules. As such, special options may be necessary to compile the code
536 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
537 problem probably cannot be fixed.</li>
539 <li><a href="http://llvm.org/PR56">Zero arg vararg functions are not
540 supported</a>. This should not affect LLVM produced by the C or C++
543 <li>The C backend does not correctly implement the <a
544 href="LangRef.html#i_stacksave"><tt>llvm.stacksave</tt></a> or
545 <a href="LangRef.html#i_stackrestore"><tt>llvm.stackrestore</tt></a>
546 intrinsics. This means that some code compiled by it can run out of stack
547 space if they depend on these (e.g. C99 varargs).</li>
553 <!-- ======================================================================= -->
554 <div class="doc_subsection">
555 <a name="x86-be">Known problems with the X86 back-end</a>
558 <div class="doc_text">
566 <!-- ======================================================================= -->
567 <div class="doc_subsection">
568 <a name="ppc-be">Known problems with the PowerPC back-end</a>
571 <div class="doc_text">
574 <li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
575 implement ordered FP comparisons</a>.</li>
580 <!-- ======================================================================= -->
581 <div class="doc_subsection">
582 <a name="alpha-be">Known problems with the Alpha back-end</a>
585 <div class="doc_text">
589 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
590 appropriate nops inserted to ensure restartability.</li>
596 <!-- ======================================================================= -->
597 <div class="doc_subsection">
598 <a name="ia64-be">Known problems with the IA64 back-end</a>
601 <div class="doc_text">
605 <li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
606 made where the argument is not 16-byte aligned, as required on IA64. (Strictly
607 speaking this is not a bug in the IA64 back-end; it will also be encountered
608 when building C++ programs using the C back-end.)</li>
610 <li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
611 ABI compliant layout of v-tables</a>. In particular, it just stores function
612 pointers instead of function descriptors in the vtable. This bug prevents
613 mixing C++ code compiled with LLVM with C++ objects compiled by other C++
616 <li>There are a few ABI violations which will lead to problems when mixing LLVM
617 output with code built with other compilers, particularly for floating-point
620 <li>Defining vararg functions is not supported (but calling them is ok).</li>
626 <!-- ======================================================================= -->
627 <div class="doc_subsection">
628 <a name="sparc-be">Known problems with the SPARC back-end</a>
631 <div class="doc_text">
634 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
635 support the 64-bit SPARC ABI (-m64).</li>
640 <!-- ======================================================================= -->
641 <div class="doc_subsection">
642 <a name="arm-be">Known problems with the ARM back-end</a>
645 <div class="doc_text">
648 <li>The ARM backend is currently in early development stages, it is not
649 ready for production use.</li>
654 <!-- *********************************************************************** -->
655 <div class="doc_section">
656 <a name="additionalinfo">Additional Information</a>
658 <!-- *********************************************************************** -->
660 <div class="doc_text">
662 <p>A wide variety of additional information is available on the <a
663 href="http://llvm.org">LLVM web page</a>, including <a
664 href="http://llvm.org/docs/">documentation</a> and <a
665 href="http://llvm.org/pubs/">publications describing algorithms and
666 components implemented in LLVM</a>. The web page also contains versions of the
667 API documentation which is up-to-date with the CVS version of the source code.
668 You can access versions of these documents specific to this release by going
669 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
671 <p>If you have any questions or comments about LLVM, please feel free to contact
672 us via the <a href="http://llvm.org/docs/#maillist"> mailing
677 <!-- *********************************************************************** -->
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