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<html><head><title>LLVM 1.1 Release Notes</title></head>
<body bgcolor=white>
<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp; <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>LLVM 1.1 Release Notes</b></font></td>
</tr></table>
<ol>
<li><a href="#intro">Introduction</a>
<li><a href="#whatsnew">What's New?</a>
<li><a href="#portability">Portability and Supported Platforms</a>
<li><a href="#install-instructions">Installation Instructions</a>
<li><a href="#knownproblems">Known Problems</a>
<ul>
<!-- <li><a href="#portabilityprobs">Portability Problems</a> -->
<li><a href="#core">Known problems with the LLVM Core</a>
<li><a href="#c-fe">Known problems with the C Front-end</a>
<li><a href="#c++-fe">Known problems with the C++ Front-end</a>
<li><a href="#x86-be">Known problems with the X86 Back-end</a>
<li><a href="#sparc-be">Known problems with the Sparc Back-end</a>
<li><a href="#c-be">Known problems with the C back-end</a>
</ul>
<li><a href="#additionalinfo">Additional Information</a>
</ul>
<p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
</ol>
<!-- *********************************************************************** -->
<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
<a name="intro">Introduction
</b></font></td></tr></table><ul>
<!-- *********************************************************************** -->
This document contains the release notes for the LLVM compiler infrastructure,
release 1.1. Here we describe the status of LLVM, including any known problems,
and bug fixes 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/1.1/">LLVM 1.1 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>
For more information about LLVM, including information about potentially more
current releases, please check out the <a href="http://llvm.cs.uiuc.edu">main
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>
Note that if you are reading this file from CVS, that this document applies to
the <i>next</i> release, not the previous one. To see the release notes for the
previous release, see the <a href="http://llvm.cs.uiuc.edu/releases/">releases
page</a>.<p>
<!-- *********************************************************************** -->
</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
<a name="whatsnew">What's New?
</b></font></td></tr></table><ul>
<!-- *********************************************************************** -->
This is the second public release of the LLVM compiler infrastructure. This
release implements the following new features:<p>
<ol>
<li><a href="http://mail.cs.uiuc.edu/pipermail/llvmdev/2003-November/000528.html">A new LLVM profiler, similar to gprof</a> is available</li><p>
<li>LLVM and the C/C++ front-end now compile on Mac OSX! Mac OSX users can now
explore the LLVM optimizer with the C backend (note that LLVM requires GCC 3.3
on Mac OSX).</li><p>
<li>LLVM has been <a
href="http://mail.cs.uiuc.edu/pipermail/llvmdev/2003-November/000554.html">moved
into an 'llvm' C++ namespace</a>, for easier integration with third-party
code.</a> Note that due to a bug in GDB 5.x, to debug namespacified LLVM code,
you will need to upgrade to GDB 6.</li>
</ol><p>
In this release, the following missing features were implemented:<p>
<ol>
<li><a href="http://llvm.cs.uiuc.edu/PR88">The interpreter does not support
invoke or unwind</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR99">Interpreter does not support the
<tt>vaarg</tt> instruction</a></li><p>
</ol><p>
In this release, the following Quality of Implementation issues were fixed:<p>
<ol>
<li><a href="http://llvm.cs.uiuc.edu/PR29">C++ front-end is not generating
linkonce linkage type when it can</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR84">C front-end doesn't emit
getelementptr for address of array element</a></li>
</ol><p>
In this release, the following bugs in the previous release were fixed:<p>
<ol>
<li><a href="http://llvm.cs.uiuc.edu/PR57">[inliner] Inlining invoke with PHI in unwind target is broken</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR58">[linker] linkonce globals should link successfully to external globals</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR59">C++ frontend can crash when compiling virtual base classes</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR62">C backend fails on constant cast expr to ptr-to-anonymous struct</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR63">#ident is not recognized by C frontend</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR64">[constmerge] Constant merging pass merges constants with external linkage</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR65">C front-end miscompiles the builtin_expect intrinsic!</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR66">[scalarrepl] Scalar Replacement of aggregates is decimating structures it shouldn't be</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR67">1.0 precompiled libstdc++ does not include wchar_t support</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR68">llvmgcc asserts when compiling functions renamed with asm's</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR69">C frontend crashes on some programs with lots of types.</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR70">[instcombine] Resolving invoke inserts cast after terminator</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR71">llvm-as crashes when labels are used in phi nodes</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR72">[build problem] Callgraph.cpp not pulled in from libipa.a</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR79">llvm-gcc crashes compiling global union initializer</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR80">C front-end crash on empty structure</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR81">CFrontend crashes when compiling C99 compound expressions</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR83">[X86] Emission of global bool initializers broken</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR87">llvm-gcc infinite loops on "case MAXINT:"</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR89">[C++] Catch blocks make unparsable labels</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR90">[C++] Initializing array with constructable objects fail</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR91">[gccld] The -r (relinking) option does not work correctly</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR92">[bcreader] Cannot read shift constant expressions from bytecode file</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR93">[lowersetjmp] Lowersetjmp pass breaks dominance properties!</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR94">llvm-gcc tries to add bools</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR95">SymbolTable::getUniqueName is very inefficient</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR98">[buildscripts] Building into objdir with .o in it fails</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR101">[setjmp/longjmp] Linking C programs which use setjmp/longjmp sometimes fail with references to the C++ runtime library!</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR104">[c++] C++ Frontend lays out superclasses like anonymous bitfields!</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR107">AsmParser Misses Symbol Redefinition Error</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR108">gccld -Lfoo -lfoo fails to find ./foo/libfoo.a</a></li>
<li><a href="http://llvm.cs.uiuc.edu/PR112">Casting a string constant to void crashes llvm-gcc</a></li>
</ol><p>
At this time, LLVM is known to work properly with SPEC CPU 2000, the Olden
benchmarks, and the Ptrdist benchmarks among many other programs. Note however
that the Sparc and X86 backends do not currently support exception throwing or
long jumping (including 253.perlbmk in SPEC). For these programs you must use
the C backend.<p>
<!-- *********************************************************************** -->
</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
<a name="portability">Portability and Supported Platforms
</b></font></td></tr></table><ul>
<!-- *********************************************************************** -->
LLVM has been extensively tested on Intel and AMD machines running Red
Hat Linux, and Sun UltraSPARC workstations running Solaris 8. Additionally,
LLVM works on Mac OS/X 10.3 and above, but only with the C back-end (no native
backend for the PowerPC is available yet).
The core LLVM infrastructure uses "autoconf" for portability, so hopefully we
work on more platforms than that. However, it is likely that we
missed something, and that minor porting is required to get LLVM to work on
new platforms. We welcome portability patches and error messages.<p>
<!-- *********************************************************************** -->
</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
<a name="knownproblems">Known Problems
</b></font></td></tr></table><ul>
<!-- *********************************************************************** -->
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.
<!-- _______________________________________________________________________ -->
<!--
</ul><h4><a name="portability"><hr size=0>Portability Problems</h4><ul>
-->
<!-- _______________________________________________________________________ -->
</ul><h4><a name="core"><hr size=0>Known problems with the LLVM Core</h4><ul>
<li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not work.<p>
<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.<p>
<li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.<p>
<li>Linking in static archive files (.a files) is very slow (there is no symbol
table in the archive).<p>
<li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
more than 256 elements</a>.<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="c-fe"><hr size=0>Known problems with the C front-end</h4><ul>
</ul><b>Bugs:</b><ul><p>
<li><a href="http://llvm.cs.uiuc.edu/PR6">Oversized integer bitfields cause crash</a>.<p>
<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><p>
</ul><b>Notes:</b><ul><p>
<li>Inline assembly is not yet supported.<p>
<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.
<p>
<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><p>
<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><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><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><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.
<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><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands
<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><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><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><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.
<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><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.
</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, which 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><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>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>, <tt>deprecated</tt>,
<tt>warn_unused_result</tt>, <tt>weak</tt><br>
<b>Ignored:</b> <tt>noreturn</tt>, <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><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.<br>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.
<b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
<tt>deprecated</tt>, <tt>may_alias</tt>
<b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>
all target specific attributes.<br>
<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> (ignored).
</ol><p>
The following extensions <b>are</b> known to be supported:
<ol>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.
<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><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.
<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><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.
<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><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><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.
<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><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.
<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><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.
<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><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).
<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><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><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><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.
</ol><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).
<!-- _______________________________________________________________________ -->
</ul><h4><a name="c++-fe"><hr size=0>Known problems with the C++ front-end</h4><ul>
For this release, the C++ front-end is considered to be fully functional but
of <b>beta</b> quality. It has been tested and works for a number of simple programs that collectively exercise most of the language. Nevertheless, it has not been in use as long as the C front-end. Please report any bugs or problems.<p>
</ul><b>Bugs</b>:<ul><p>
<li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
front-end</a><p>
</ul><b>Notes</b>:<ul><p>
<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>.<p>
<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).<p>
<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><a href="http://llvm.cs.uiuc.edu/PR11">Code for executing destructors when
unwinding is not shared</a> (this is a quality of implementation problem,
which does not effect functionality).<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="x86-be"><hr size=0>Known problems with the X86 back-end</h4><ul>
<li>The X86 code generator <a
href="http://llvm.cs.uiuc.edu/PR16">does not currently
support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
or calls the C <tt>longjmp</tt> function will abort.<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="sparc-be"><hr size=0>Known problems with the Sparc back-end</h4><ul>
<li>The Sparc code generator <a
href="http://llvm.cs.uiuc.edu/PR15">does not currently
support the <tt>unwind</tt> instruction</a>, so code that throws a C++ exception
or calls the C <tt>longjmp</tt> function will abort.<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="c-be"><hr size=0>Known problems with the C back-end</h4><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.<p>
<li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
cannot include special floating point numbers like Not-A-Number or Infinity.<p>
<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.<p>
<li><a href="http://llvm.cs.uiuc.edu/PR77">Variables in scope of output setjmp
calls should be volatile</a>. Note that this does not effect correctness on
many platforms.<p>
<li>The code produces by the C back-end has only been tested with the Sun CC,
GCC, and Intel compilers. It is possible that it will have to be adjusted to
support other C compilers.<p>
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</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
<a name="additionalinfo">Additional Information
</b></font></td></tr></table><ul>
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A wide variety of additional information is available on the LLVM web page,
including mailing lists publications describing algorithms and components
implemented in LLVM. 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>
If you have any questions or comments about LLVM, please feel free to contact us
via the mailing lists.<p>
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</ul>
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<hr><font size-1>
Maintained By: <a href="http://llvm.cs.uiuc.edu/">The LLVM Team</a><br>
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Last modified: Wed Nov 12 16:48:33 CST 2003
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