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<title>LLVM 2.0 Release Notes</title>
<div class="doc_title">LLVM 2.0 Release Notes</div>
<li><a href="#intro">Introduction</a></li>
<li><a href="#whatsnew">What's New?</a></li>
<li><a href="GettingStarted.html">Installation Instructions</a></li>
<li><a href="#portability">Portability and Supported Platforms</a></li>
<li><a href="#knownproblems">Known Problems</a>
<li><a href="#additionalinfo">Additional Information</a></li>
Chris Lattner
committed
<div class="doc_author">
Chris Lattner
committed
<p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
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<div class="doc_section">
<a name="intro">Introduction</a>
</div>
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<div class="doc_text">
<p>This document contains the release notes for the LLVM compiler
infrastructure, release 2.0. Here we describe the status of LLVM, including any
known problems and major improvements from the previous release. All LLVM
releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
releases web site</a>.
<p>For more information about LLVM, including information about the latest
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committed
release, please check out the <a href="http://llvm.org/">main LLVM
web site</a>. If you have questions or comments, the <a
href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
<p>Note that if you are reading this file from CVS or the main LLVM web page,
this document applies to the <i>next</i> release, not the current one. To see
the release notes for the current or previous releases, see the <a
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href="http://llvm.org/releases/">releases page</a>.</p>
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<div class="doc_section">
<a name="whatsnew">What's New?</a>
</div>
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<p>This is the eleventh public release of the LLVM Compiler Infrastructure.
Being the first major release since 1.0, this release is different in several
ways from our previous releases:</p>
<ol>
<li>We took this as an opportunity to
break backwards compatibility with the LLVM 1.x bytecode and .ll file format.
If you have LLVM 1.9 .ll files that you would like to upgrade to LLVM 2.x, we
recommend the use of the stand alone <a href="#llvm-upgrade">llvm-upgrade</a>
tool. We intend to keep compatibility with .ll and .bc formats within the 2.x
release series, like we did within the 1.x series.</li>
<li>There are several significant change to the LLVM IR and internal APIs, such
as a major overhaul of the type system, the completely new bitcode file
format, etc.</li>
<li>We designed the release around a 6 month release cycle instead of the usual
3-month cycle. This gave us extra time to develop and test some of the
more invasive features in this release.</li>
<li>LLVM 2.0 no longer supports the llvm-gcc3 front-end.</li>
</ol>
<p>Note that while this is a major version bump, this release has been
extensively tested on a wide range of software. It is easy to say that this
is our best release yet, in terms of both features and correctness.</p>
</div>
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<a name="newfeatures">New Features in LLVM 2.0</a>
</div>
<!--_________________________________________________________________________-->
<div class="doc_subsubsection"><a name="optimizer">Optimizer
Improvements</a></div>
<p>The mid-level optimizer is now faster and produces better code in many cases.
Significant changes include:</p>
<ul>
</div>
<!--_________________________________________________________________________-->
<div class="doc_subsubsection"><a name="codegen">Code
Generator Enhancements</a></div>
<p>
The LLVM Target-Independent code generator now supports more target features and
optimizes many cases more aggressively. New features include:
</p>
<ul>
</ul>
<p>In addition, the LLVM target description format has itself been extended in
several ways:</p>
<ul>
</ul>
<p>Further, several significant target-specific enhancements are included in
<!--_________________________________________________________________________-->
<div class="doc_subsubsection"><a name="other">Other Improvements</a></div>
<p>More specific changes include:</p>
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<div class="doc_section">
<a name="portability">Portability and Supported Platforms</a>
</div>
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<p>LLVM is known to work on the following platforms:</p>
<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
(and probably other unix-like systems).</li>
<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
<li>Sun UltraSPARC workstations running Solaris 8.</li>
<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
support is available for native builds with Visual C++).</li>
<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
64-bit modes.</li>
<li>Alpha-based machines running Debian GNU/Linux.</li>
<li>Itanium-based machines running Linux and HP-UX.</li>
<p>The core LLVM infrastructure uses
<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
to the machine and operating system on which it is built. However, minor
porting may be required to get LLVM to work on new platforms. We welcome your
portability patches and reports of successful builds or error messages.</p>
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<div class="doc_section">
<a name="knownproblems">Known Problems</a>
</div>
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<div class="doc_text">
<p>This section contains all known problems with the LLVM system, listed by
component. As new problems are discovered, they will be added to these
sections. If you run into a problem, please check the <a
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href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
there isn't already one.</p>
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<div class="doc_subsection">
<a name="experimental">Experimental features included with this release</a>
</div>
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<p>The following components of this LLVM release are either untested, known to
be broken or unreliable, or are in early development. These components should
not be relied on, and bugs should not be filed against them, but they may be
useful to some people. In particular, if you would like to work on one of these
components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
<li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in in a
future release.</li>
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<li>The Alpha JIT is experimental.</li>
<li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
<tt>-filetype</tt> llc option.</li>
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<div class="doc_subsection">
<a name="x86-be">Known problems with the X86 back-end</a>
</div>
<div class="doc_text">
<ul>
<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
assembly that uses the X86 floating point stack</a>.</li>
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<div class="doc_subsection">
<a name="ppc-be">Known problems with the PowerPC back-end</a>
</div>
<div class="doc_text">
<ul>
<li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
implement ordered FP comparisons</a>.</li>
</ul>
</div>
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<div class="doc_subsection">
<a name="sparc-be">Known problems with the SPARC back-end</a>
</div>
<div class="doc_text">
<ul>
<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
support the 64-bit SPARC ABI (-m64).</li>
</ul>
</div>
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<div class="doc_subsection">
<a name="c-be">Known problems with the C back-end</a>
</div>
<div class="doc_text">
<ul>
<li>The C back-end produces code that violates the ANSI C Type-Based Alias
Analysis rules. As such, special options may be necessary to compile the code
(for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
problem probably cannot be fixed.</li>
<li><a href="http://llvm.org/PR56">Zero arg vararg functions are not
supported</a>. This should not affect LLVM produced by the C or C++
frontends.</li>
<li>The C backend does not correctly implement the <a
href="LangRef.html#int_stacksave"><tt>llvm.stacksave</tt></a> or
<a href="LangRef.html#int_stackrestore"><tt>llvm.stackrestore</tt></a>
intrinsics. This means that some code compiled by it can run out of stack
space if they depend on these (e.g. C99 varargs).</li>
<li><a href="http://llvm.org/PR802">The C backend does not support inline
assembly code</a>.</li>
</ul>
</div>
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<div class="doc_subsection">
<a name="alpha-be">Known problems with the Alpha back-end</a>
</div>
<div class="doc_text">
<ul>
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<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
appropriate nops inserted to ensure restartability.</li>
</ul>
</div>
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<div class="doc_subsection">
<a name="ia64-be">Known problems with the IA64 back-end</a>
</div>
<div class="doc_text">
<ul>
<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
made where the argument is not 16-byte aligned, as required on IA64. (Strictly
speaking this is not a bug in the IA64 back-end; it will also be encountered
when building C++ programs using the C back-end.)</li>
<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
ABI compliant layout of v-tables</a>. In particular, it just stores function
pointers instead of function descriptors in the vtable. This bug prevents
mixing C++ code compiled with LLVM with C++ objects compiled by other C++
compilers.</li>
<li>There are a few ABI violations which will lead to problems when mixing LLVM
output with code built with other compilers, particularly for floating-point
programs.</li>
<li>Defining vararg functions is not supported (but calling them is ok).</li>
<li>The Itanium backend has bitrotted somewhat.</li>
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<div class="doc_subsection">
<a name="arm-be">Known problems with the ARM back-end</a>
</div>
<div class="doc_text">
<ul>
<li>The Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
processors, any thumb program compiled with LLVM crashes or produces wrong
results. (<a href="http://llvm.org/PR1388">PR1388</a>)</li>
<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
</li>
<li>QEMU-ARM (<= 0.9.0) wrongly executes programs compiled with LLVM. A non-affected QEMU version must be used or this
<a href="http://cvs.savannah.nongnu.org/viewcvs/qemu/target-arm/translate.c?root=qemu&r1=1.46&r2=1.47&makepatch=1&diff_format=h">
patch</a> must be applied on QEMU.</li>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="core">Known problems with the LLVM Core</a>
</div>
<div class="doc_text">
<li>In the JIT, <tt>dlsym()</tt> on a symbol compiled by the JIT will not
work.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="c-fe">Known problems with the C front-end</a>
</div>
<!-- _______________________________________________________________________ -->
<p>llvm-gcc4 is far more stable and produces better code than llvm-gcc3, but
does not currently support <a href="http://llvm.org/PR869">Link-Time
Optimization</a> or <a href="http://llvm.org/PR870">C++ Exception Handling</a>,
which llvm-gcc3 does.</p>
<p>llvm-gcc4 does not support the <a href="http://llvm.org/PR947">GCC indirect
goto extension</a>, but llvm-gcc3 does.</p>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
Notes
</div>
<div class="doc_text">
<ul>
<li>"long double" is transformed by the front-end into "double". There is no
support for floating point data types of any size other than 32 and 64
bits.</li>
<li>Although many GCC extensions are supported, some are not. In particular,
the following extensions are known to <b>not be</b> supported:
<ol>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
<p>The following GCC extensions are <b>partially</b> supported. An ignored
attribute means that the LLVM compiler ignores the presence of the attribute,
but the code should still work. An unsupported attribute is one which is
ignored by the LLVM compiler and will cause a different interpretation of
<ol>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
Arrays whose length is computed at run time.<br>
Supported, but allocated stack space is not freed until the function returns (noted above).</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
Declaring that functions have no side effects or that they can never
<b>Supported:</b> <tt>alias</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
<tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
<tt>format_arg</tt>, <tt>non_null</tt>, <tt>noreturn</tt>, <tt>regparm</tt>
<tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
<tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
<b>Ignored:</b> <tt>noinline</tt>,
<tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
<tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
<b>Unsupported:</b> All other target specific attributes</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
Specifying attributes of variables.<br>
<b>Supported:</b> <tt>alias</tt>, <tt>cleanup</tt>, <tt>common</tt>,
<tt>nocommon</tt>, <tt>deprecated</tt>, <tt>dllimport</tt>,
<tt>dllexport</tt>, <tt>section</tt>, <tt>transparent_union</tt>,
<tt>unused</tt>, <tt>used</tt>, <tt>weak</tt><br>
<b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
<tt>shared</tt>, <tt>tls_model</tt>,
<tt>vector_size</tt>, all target specific attributes.
</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
<b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
<tt>deprecated</tt>, <tt>may_alias</tt><br>
<b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
all target specific attributes.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
Other built-in functions.<br>
We support all builtins which have a C language equivalent (e.g.,
<tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
<tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
<tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt>
(currently ignored). We also support builtins for ISO C99 floating
point comparison macros (e.g., <tt>__builtin_islessequal</tt>),
<tt>__builtin_prefetch</tt>, <tt>__builtin_popcount[ll]</tt>,
<tt>__builtin_clz[ll]</tt>, and <tt>__builtin_ctz[ll]</tt>.</li>
<p>The following extensions <b>are</b> known to be supported:</p>
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<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
<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>
<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
<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>
<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>
<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>
<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>
<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>
<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
or arrays as values.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
<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>
<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>
<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>
<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>
<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>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
</ol></li>
</ul>
<p>If you run into GCC extensions which have not been included in any of these
lists, please let us know (also including whether or not they work).</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="c++-fe">Known problems with the C++ front-end</a>
</div>
<div class="doc_text">
<p>For this release, the C++ front-end is considered to be fully
tested and works for a number of non-trivial programs, including LLVM
itself.</p>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
Notes
</div>
<li>llvm-gcc4 does not support C++ exception handling at all yet.</li>
<li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
function and in the <tt>setjmp</tt> receiver function may not be run.
Objects in intervening stack frames will be destroyed, however (which is
<li>The LLVM C++ front-end follows the <a
href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
This document, which is not Itanium specific, specifies a standard for name
mangling, class layout, v-table layout, RTTI formats, and other C++
representation issues. Because we use this API, code generated by the LLVM
compilers should be binary compatible with machine code generated by other
Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
<i>However</i>, the exception handling mechanism used by llvm-gcc3 is very
different from the model used in the Itanium ABI, so <b>exceptions will not
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="additionalinfo">Additional Information</a>
</div>
<!-- *********************************************************************** -->
<p>A wide variety of additional information is available on the <a
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href="http://llvm.org">LLVM web page</a>, including <a
href="http://llvm.org/docs/">documentation</a> and <a
href="http://llvm.org/pubs/">publications describing algorithms and
components implemented in LLVM</a>. The web page also contains versions of the
API documentation which is up-to-date with the CVS version of the source code.
You can access versions of these documents specific to this release by going
into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
<p>If you have any questions or comments about LLVM, please feel free to contact
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