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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
<title>LLVM 1.5 Release Notes</title>
</head>
<body>
<div class="doc_title">LLVM 1.5 Release Notes</div>
<ol>
<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>
</ol>
<div class="doc_author">
<p>Written by the <a href="http://llvm.cs.uiuc.edu">LLVM Team</a><p>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="intro">Introduction</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>This document contains the release notes for the LLVM compiler
infrastructure, release 1.5. Here we describe the status of LLVM, including any
known problems and major improvements from the previous release. The most
up-to-date version of this document can be found on the <a
href="http://llvm.cs.uiuc.edu/releases/1.5/">LLVM 1.5 web site</a>. If you are
not reading this on the LLVM web pages, you should probably go there because
this document may be updated after the release.</p>
<p>For more information about LLVM, including information about the latest
release, please check out the <a href="http://llvm.cs.uiuc.edu">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
list</a> is a good place to send them.</p>
<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
href="http://llvm.cs.uiuc.edu/releases/">releases page</a>.</p>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="whatsnew">What's New?</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>This is the sixth public release of the LLVM Compiler Infrastructure.</p>
<p> At this time, LLVM is known to correctly compile a wide range of C and C++
programs, including the SPEC CPU95 &amp; 2000 suite. It includes bug fixes for
those problems found since the 1.4 release and a large number of new features
and enhancements, described below.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="newfeatures">New Features in LLVM 1.5</a>
</div>
<!--_________________________________________________________________________-->
<div class="doc_subsubsection">New Native Code Generators</div>
<div class="doc_text">
<p>
This release includes new native code generators for <a
href="#alpha-be">Alpha</a>, <a href="#ia64-be">IA-64</a>, and SPARC-V8 (32-bit
SPARC). These code generators are still beta quality, but are progressing
rapidly.
</p>
</div>
<!--_________________________________________________________________________-->
<div class="doc_subsubsection">New Instruction Selector Framework</div>
<div class="doc_text">
<p>This release includes a <a href="CodeGenerator.html#instselect">new framework
for building instruction selectors</a>, which has long been the hardest part of
building a new LLVM target. This framework handles a lot of the mundane (but
easy to get wrong) details of writing the instruction selector, such as
generating efficient code for <a
href="LangRef.html#i_getelementptr">getelementptr</a> instructions, promoting
small integer types to larger types (e.g. for RISC targets with one size of
integer registers), expanding 64-bit integer operations for 32-bit hosts, etc.
Currently, the X86, PowerPC, Alpha, and IA-64 backends use this framework. The
SPARC backends will be migrated when time permits.
</p>
</div>
<!--_________________________________________________________________________-->
<div class="doc_subsubsection">New Support For Custom Calling Convetions</div>
<div class="doc_text">
<p>LLVM 1.5 adds supports for <a href="LangRef.html#callingconv">custom and
target-specific calling conventions</a>. Traditionally, the LLVM code
generators match the native C calling conventions for a target. This is
important for compatibility, but is not very flexible. This release allows
custom calling conventions to be established for functions, and defines three
target-independent conventions (C call, fast call, and cold call) which may be
supported by code generators. When possible, the LLVM optimizer promotes C
functions to use the "fastcc" convention, allowing the use of more efficient
calling sequences (e.g., parameters are passed in registers in the X86 target).
</p>
<p>Targets may now also define target-specific calling conventions, allowing
LLVM to fully support calling convention altering options (e.g. GCC's
<tt>-mregparm</tt> flag) and well-defined target conventions (e.g. stdcall and
fastcall on X86).</p>
</div>
<!--_________________________________________________________________________-->
<div class="doc_subsubsection">New Support for "Proper Tail Calls"</div>
<div class="doc_text">
<p>The release now includes support for <a
href="http://doi.acm.org/10.1145/277650.277719">proper tail calls</a>, as
required to implement languages like Scheme. Tail calls make use of two
features: custom calling conventions (described above), which allow the code
generator to emit code for the caller to deallocate its own stack when it
returns. The second feature is a flag on the <a href="LangRef.html#i_call">call
instruction</a>, which indicates that the callee does not access the callers
stack frame (indicating that it is acceptable to deallocate the caller stack
before invoking the callee). LLVM proper tail calls run on the system stack (as
do normal calls), supports indirect tail calls, tail calls with arbitrary
numbers of arguments, tail calls where the callee requires more argument space
than the caller, etc. The only case not supported are varargs calls, but that
could be added if desired.
</p>
<p>In order for a front-end to get guaranteed tail call, it must mark functions
as "fastcc", mark calls with the 'tail' marker, and follow the call with a
return of the called value (or void). The optimizer and code generator attempt
to handle more general cases, but the simple case will always work if the code
generator supports tail calls. Here is a simple example:</p>
<p><pre>
fastcc int %bar(int %X, int(double, int)* %FP) { ;<i> fastcc</i>
%Y = tail call fastcc int %FP(double 0.0, int %X) ;<i> tail, fastcc</i>
ret int %Y
}
</pre></p>
<p>In LLVM 1.5, the X86 code generator is the only target that has been enhanced
to support proper tail calls (other targets will be enhanced in future).
Further, because this support was added very close to the release, it is
disabled by default. Pass <tt>-enable-x86-fastcc</tt> to llc to enable it. X86
support will be enabled by default in the next LLVM release.</p>
</div>
<!--_________________________________________________________________________-->
<div class="doc_subsubsection">Other New Features</div>
<div class="doc_text">
<ol>
<li>LLVM now includes an <a href="http://llvm.cs.uiuc.edu/PR415">
Interprocedural Sparse Conditional Constant Propagation</a> pass, named
-ipsccp, which is run by default at link-time.</li>
<li>LLVM 1.5 is now about 15% faster than LLVM 1.4 and its core data
structures use about 30% less memory.</li>
<li>Support for Microsoft Visual Studio is improved, and <a
href="GettingStartedVS.html">now documented</a>.</li>
<li><a href="GettingStarted.html#config">Configuring LLVM to build a subset
of the available targets</a> is now implemented, via the
<tt>--enable-targets=</tt> option.</li>
<li>LLVM can now create native shared libraries with '<tt>llvm-gcc ...
-shared -Wl,-native</tt>' (or with <tt>-Wl,-native-cbe</tt>).</li>
<li>LLVM now supports a new "<a href="LangRef.html#i_prefetch">llvm.prefetch
</a>" intrinsic, and llvm-gcc now supports __builtin_prefetch.
<li>LLVM now supports intrinsics for <a href="LangRef.html#int_count">bit
counting</a> and llvm-gcc now implements the GCC
<tt>__builtin_popcount</tt>, <tt>__builtin_ctz</tt>, and
<tt>__builtin_clz</tt> builtins.</li>
<li>LLVM now builds on HP-UX with the HP aCC Compiler.</li>
<li>The LLVM X86 backend can now emit Cygwin-compatible .s files.</li>
<li>LLVM now includes workarounds in the code generator generator which
reduces the likelyhood of <a href="http://llvm.cs.uiuc.edu/PR448">GCC
hitting swap during optimized builds</a>.</li>
</ol>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="codequality">Code Quality Improvements in LLVM 1.5</a>
</div>
<div class="doc_text">
<ol>
<li>The -globalopt pass now promotes non-address-taken static globals that are
only accessed in main to SSA registers.</li>
<li>Loops with trip counts based on array pointer comparisons (e.g. "<tt>for (i
= 0; &amp;A[i] != &amp;A[100]; ++i) ...</tt>") are optimized better than before,
which primarily helps iterator-intensive C++ codes.</li>
<li>The code generator now uses information about takes advantage of commutative
two-address instructions when performing register allocation.</li>
</ol>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="bugfix">Significant Bugs Fixed in LLVM 1.5</a>
</div>
<div class="doc_text">
<p>Bugs fixed in the LLVM Core:</p>
<ol>
<li><a href="http://llvm.cs.uiuc.edu/PR491">[dse] DSE deletes stores that
are partially overwritten by smaller stores</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR548">[instcombine] miscompilation of
setcc or setcc in one case</a></li>
<li>Transition code for LLVM 1.0 style varargs was removed from the .ll file
parser. LLVM 1.0 bytecode files are still supported. </li>
</ol>
<p>Code Generator Bugs:</p>
<ol>
<li><a href="http://llvm.cs.uiuc.edu/PR490">[cbackend] Logical constant
expressions (and/or/xor) not implemented</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR511">[cbackend] C backend does not
respect 'volatile'</a></li>
</ol>
<p>Bugs in the C/C++ front-end:</p>
<ol>
<li><a href="http://llvm.cs.uiuc.edu/PR487">[llvmgcc] llvm-gcc incorrectly
rejects some constant initializers involving the addresses of array
elements</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR501">[llvm-g++] Crash compiling
anonymous union</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR509">[llvm-g++] Do not use dynamic
initialization where static init will do</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR510">[llvmgcc] Field offset
miscalculated for some structure fields following bit fields</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR513">[llvm-g++] Temporary lifetimes
incorrect for short circuit logical operations</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR517">[llvm-gcc] Crash compiling
bitfield &lt;-&gt; aggregate assignment</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR520">[llvm-g++] Error compiling
virtual function thunk with an unnamed argument</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR522">[llvm-gcc] Crash on certain
C99 complex number routines</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR529">[llvm-g++] Crash using placement
new on an array type</a></li>
</ol>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="portability">Portability and Supported Platforms</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>LLVM is known to work on the following platforms:</p>
<ul>
<li>Intel and AMD machines running Red Hat Linux and FreeBSD (and probably
other unix-like systems).</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-based Mac OS X systems, running 10.2 and above.</li>
<li>Alpha-based machines running Debian GNU/Linux.</li>
<li>Itanium-based machines running Linux and HP-UX.</li>
</ul>
<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>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="knownproblems">Known Problems</a>
</div>
<!-- *********************************************************************** -->
<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
href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
there isn't already one.</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="experimental">Experimental features included with this release</a>
</div>
<div class="doc_text">
<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 llvmdev list.</p>
<ul>
<li>The following passes are incomplete or buggy, and may be removed in future
releases: <tt>-cee, -branch-combine, -instloops, -paths, -pre</tt></li>
<li>The <tt>llvm-db</tt> tool is in a very early stage of development, but can
be used to step through programs and inspect the stack.</li>
<li>The "iterative scan" register allocator (enabled with
<tt>-regalloc=iterativescan</tt>) is not stable.</li>
<li>The SparcV8, Alpha, and IA64 code generators are experimental.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="core">Known problems with the LLVM Core</a>
</div>
<div class="doc_text">
<ul>
<li>In the JIT, <tt>dlsym()</tt> on a symbol compiled by the JIT will not
work.</li>
<li>The JIT does not use mutexes to protect its internal data structures. As
such, execution of a threaded program could cause these data structures to be
corrupted.
</li>
<li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not
mark values live across a setjmp as volatile</a>. This missing feature
only affects targets whose setjmp/longjmp libraries do not save and restore
the entire register file.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="c-fe">Known problems with the C front-end</a>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">Bugs</div>
<div class="doc_text">
<ul>
<li>C99 Variable sized arrays do not release stack memory when they go out of
scope. Thus, the following program may run out of stack space:
<pre>
for (i = 0; i != 1000000; ++i) {
int X[n];
foo(X);
}
</pre></li>
<li>Initialization of global union variables can only be done <a
href="http://llvm.cs.uiuc.edu/PR162">with the largest union member</a>.</li>
</ul>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
Notes
</div>
<div class="doc_text">
<ul>
<li>Inline assembly is not yet supported.</li>
<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>The following Unix system functionality has not been tested and may not
work:
<ol>
<li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
<tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
<li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
- These functions have not been tested.
</ol></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/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/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>
</ol>
<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
the program.</p>
<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
return.<br>
<b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
<tt>noreturn</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
<tt>unused</tt>,
<tt>deprecated</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> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
<tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
<tt>fastcall</tt>, 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>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
<tt>deprecated</tt>, <tt>transparent_union</tt>,
<tt>unused</tt>, <tt>weak</tt><br>
<b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
<tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
<tt>vector_size</tt>, <tt>dllimport</tt>,
<tt>dllexport</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>
</ol>
<p>The following extensions <b>are</b> known to be supported:</p>
<ol>
<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/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 &lt;ESC&gt;.</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>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">Bugs</div>
<div class="doc_text">
<ul>
<li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
front-end</a>.</li>
<li><b>IA-64 specific</b>: The C++ front-end does not use <a
href="http://llvm.cs.uiuc.edu/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>
</ul>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
Notes
</div>
<div class="doc_text">
<ul>
<li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
parser is significantly more standards compliant (and picky) than prior GCC
versions. For more information, see the C++ section of the <a
href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</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
better than most compilers).</li>
<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 is very
different from the model used in the Itanium ABI, so <b>exceptions will not
interact correctly</b>. </li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="x86-be">Known problems with the X86 back-end</a>
</div>
<div class="doc_text">
<ul>
<li>None yet</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="sparcv9-be">Known problems with the SparcV9 back-end</a>
</div>
<div class="doc_text">
<ul>
<li><a href="http://llvm.cs.uiuc.edu/PR60">[sparcv9] SparcV9 backend miscompiles
several programs in the LLVM test suite</a></li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="ppc-be">Known problems with the PowerPC back-end</a>
</div>
<div class="doc_text">
<ul>
<li>None yet</li>
</ul>
</div>
<!-- ======================================================================= -->
<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.cs.uiuc.edu/PR56">Zero arg vararg functions are not
supported</a>. This should not affect LLVM produced by the C or C++
frontends.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="alpha-be">Known problems with the Alpha back-end</a>
</div>
<div class="doc_text">
<ul>
<li>On 21164s, some rare FP arithmatic sequences which may trap do not have the appropriate nops inserted to ensure restartability.</li>
<li>Vararg functions are not supported.</li>
<li>Due to the vararg problems, C++ exceptions do not work. Small changes are required to the CFE (which break correctness in the exception handler) to compile the exception handling library (and thus the C++ standard library).</li>
</ul>
</div>
<!-- ======================================================================= -->
<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>There are a few ABI violations which will lead to problems
when mixing LLVM output with code built with other compilers,
particularly for C++ and floating-point programs.</li>
<li>Vararg functions are not supported.</li>
</ul>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="additionalinfo">Additional Information</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>A wide variety of additional information is available on the LLVM web page,
including <a href="http://llvm.cs.uiuc.edu/docs/#maillist">mailing lists</a> and
<a href="http://llvm.cs.uiuc.edu/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
us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
lists</a>.</p>
</div>
<!-- *********************************************************************** -->
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