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- <title>LLVM 1.7cvs Release Notes</title>
+ <title>LLVM 2.0 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 1.7 Release Notes</div>
+<div class="doc_title">LLVM 2.0 Release Notes</div>
<ol>
<li><a href="#intro">Introduction</a></li>
<div class="doc_text">
<p>This document contains the release notes for the LLVM compiler
-infrastructure, release 1.7. 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.org/releases/">LLVM releases 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>
+infrastructure, release 2.0. Here we describe the status of LLVM, including
+major improvements from the previous release and any known problems. All LLVM
+releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
+releases web site</a>.</p>
<p>For more information about LLVM, including information about the latest
release, please check out the <a href="http://llvm.org/">main LLVM
<div class="doc_text">
-<p>This is the seventh public release of the LLVM Compiler Infrastructure. This
-release incorporates a large number of enhancements and additions (primarily in
-the code generator), which combine to improve the quality of the code generated
-by LLVM by up to 30% in some cases. This release is also the first release to
-have first-class support for Mac OS X: all of the major bugs have been shaken
-out and it is now as well supported as Linux on X86.</p>
+<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 (which is included with 2.0). 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 (described below).</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. Users are required to
+ upgrade to llvm-gcc4. llvm-gcc4 includes many features over
+ llvm-gcc3, is faster, and is <a href="CFEBuildInstrs.html">much easier to
+ build from source</a>.</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. This is
+ the first LLVM release to correctly compile and optimize major software like
+ LLVM itself, Mozilla/Seamonkey, Qt 4.3rc1, kOffice, etc out of the box on
+ linux/x86.
+ </p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="newfeatures">New Features in LLVM 1.7cvs</a>
-</div>
-
-
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="portability">Portability and Supported Platforms</a>
+<a name="newfeatures">New Features in LLVM 2.0</a>
</div>
-<!-- *********************************************************************** -->
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="majorchanges">Major Changes</a></div>
<div class="doc_text">
-<p>LLVM is known to work on the following platforms:</p>
+<p>Changes to the LLVM IR itself:</p>
<ul>
- <li>Intel and AMD machines running Red Hat Linux, Fedora Core 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 and X86-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>
+
+<li>Integer types are now completely signless. This means that we
+ have types like i8/i16/i32 instead of ubyte/sbyte/short/ushort/int
+ etc. LLVM operations that depend on sign have been split up into
+ separate instructions (<a href="http://llvm.org/PR950">PR950</a>). This
+ eliminates cast instructions that just change the sign of the operands (e.g.
+ int -> uint), which reduces the size of the IR and makes optimizers
+ simpler to write.</li>
+
+<li>Integer types with arbitrary bitwidths (e.g. i13, i36, i42, i1057, etc) are
+ now supported in the LLVM IR and optimizations (<a
+ href="http://llvm.org/PR1043">PR1043</a>). However, neither llvm-gcc
+ (<a href="http://llvm.org/PR1284">PR1284</a>) nor the native code generators
+ (<a href="http://llvm.org/PR1270">PR1270</a>) support non-standard width
+ integers yet.</li>
+
+<li>'Type planes' have been removed (<a href="http://llvm.org/PR411">PR411</a>).
+ It is no longer possible to have two values with the same name in the
+ same symbol table. This simplifies LLVM internals, allowing significant
+ speedups.</li>
+
+<li>Global variables and functions in .ll files are now prefixed with
+ @ instead of % (<a href="http://llvm.org/PR645">PR645</a>).</li>
+
+<li>The LLVM 1.x "bytecode" format has been replaced with a
+ completely new binary representation, named 'bitcode'. The <a
+ href="BitCodeFormat.html">Bitcode Format</a> brings a
+ number of advantages to the LLVM over the old bytecode format: it is denser
+ (files are smaller), more extensible, requires less memory to read,
+ is easier to keep backwards compatible (so LLVM 2.5 will read 2.0 .bc
+ files), and has many other nice features.</li>
+
+<li>Load and store instructions now track the alignment of their pointer
+ (<a href="http://www.llvm.org/PR400">PR400</a>). This allows the IR to
+ express loads that are not sufficiently aligned (e.g. due to '<tt>#pragma
+ packed</tt>') or to capture extra alignment information.</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>
+<p>Major new features:</p>
-</div>
+<ul>
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="knownproblems">Known Problems</a>
-</div>
-<!-- *********************************************************************** -->
+<li>A number of ELF features are now supported by LLVM, including 'visibility',
+ extern weak linkage, Thread Local Storage (TLS) with the <tt>__thread</tt>
+ keyword, and symbol aliases.
+ Among other things, this means that many of the special options needed to
+ configure llvm-gcc on linux are no longer needed, and special hacks to build
+ large C++ libraries like Qt are not needed.</li>
-<div class="doc_text">
+<li>LLVM now has a new MSIL backend. <tt>llc -march=msil</tt> will now turn LLVM
+ into MSIL (".net") bytecode. This is still fairly early development
+ with a number of limitations.</li>
-<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.org/bugs/">LLVM bug database</a> and submit a bug if
-there isn't already one.</p>
+<li>A new <a href="CommandGuide/html/llvm-upgrade.html">llvm-upgrade</a> tool
+ exists to migrates LLVM 1.9 .ll files to LLVM 2.0 syntax.</li>
+</ul>
</div>
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="experimental">Experimental features included with this release</a>
-</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="llvmgccfeatures">llvm-gcc
+Improvements</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>
+<p>New features include:
+</p>
<ul>
-<li>The following passes are incomplete or buggy, and may be removed in future
- releases: <tt>-cee, -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 SparcV8 and IA64 code generators are experimental.</li>
-<li>The Alpha JIT is experimental.</li>
-</ul>
+<li>Precompiled Headers (PCH) are now supported.</li>
-</div>
+<li>"<tt>#pragma packed</tt>" is now supported, as are the various features
+ described above (visibility, extern weak linkage, __thread, aliases,
+ etc).</li>
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="build">Known problems with the Build System</a>
+<li>Tracking function parameter/result attributes is now possible.</li>
+
+<li>Many internal enhancements have been added, such as improvements to
+ NON_LVALUE_EXPR, arrays with non-zero base, structs with variable sized
+ fields, VIEW_CONVERT_EXPR, CEIL_DIV_EXPR, nested functions, and many other
+ things. This is primarily to supports non-C GCC front-ends, like Ada.</li>
+
+<li>It is simpler to configure llvm-gcc for linux.</li>
+
+</ul>
+
</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="optimizer">Optimizer
+Improvements</a></div>
+
<div class="doc_text">
+<p>New features include:
+</p>
<ul>
- <li>The <a href="http://llvm.org/PR656">configure script sometimes fails on Solaris/Sparc</a>. A work around is documented in <a href="http://llvm.org/PR656">PR656.</a></li>
-</ul>
-</div>
+<li>The <a href="WritingAnLLVMPass.html">pass manager</a> has been entirely
+ rewritten, making it significantly smaller, simpler, and more extensible.
+ Support has been added to run <tt>FunctionPass</tt>es interlaced with
+ <tt>CallGraphSCCPass</tt>es, we now support loop transformations
+ explicitly with <tt>LoopPass</tt>, and <tt>ModulePass</tt>es may now use the
+ result of <tt>FunctionPass</tt>es.</li>
+<li>LLVM 2.0 includes a new loop rotation pass, which converts "for loops" into
+ "do/while loops", where the condition is at the bottom of the loop.</li>
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="core">Known problems with the LLVM Core</a>
+<li>The Loop Strength Reduction pass has been improved, and we now support
+ sinking expressions across blocks to reduce register pressure.</li>
+
+<li>The <tt>-scalarrepl</tt> pass can now promote unions containing FP values
+ into a register, it can also handle unions of vectors of the same
+ size.</li>
+
+<li>The [Post]DominatorSet classes have been removed from LLVM and clients
+ switched to use the more-efficient ETForest class instead.</li>
+
+<li>The ImmediateDominator class has also been removed, and clients have been
+ switched to use DominatorTree instead.</li>
+
+<li>The predicate simplifier pass has been improved, making it able to do
+ simple value range propagation and eliminate more conditionals. However,
+ note that predsimplify is not enabled by default in llvm-gcc.</li>
+
+</ul>
+
</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="codegen">Code
+Generator Enhancements</a></div>
+
<div class="doc_text">
+<p>
+New features include:
+</p>
<ul>
- <li>In the JIT, <tt>dlsym()</tt> on a symbol compiled by the JIT will not
- work.</li>
+
+<li>LLVM now supports software floating point, which allows LLVM to target
+ chips that don't have hardware FPUs (e.g. ARM thumb mode).</li>
+
+<li>A new register scavenger has been implemented, which is useful for
+ finding free registers after register allocation. This is useful when
+ rewriting frame references on RISC targets, for example.</li>
+
+<li>Heuristics have been added to avoid coalescing vregs with very large live
+ ranges to physregs. This was bad because it effectively pinned the physical
+ register for the entire lifetime of the virtual register (<a
+ href="http://llvm.org/PR711">PR711</a>).</li>
+
+<li>Support now exists for very simple (but still very useful)
+ rematerialization the register allocator, enough to move
+ instructions like "load immediate" and constant pool loads.</li>
+
+<li>Switch statement lowering is significantly better, improving codegen for
+ sparse switches that have dense subregions, and implemented support
+ for the shift/and trick.</li>
+
+<li>LLVM now supports tracking physreg sub-registers and super-registers
+ in the code generator, and includes extensive register
+ allocator changes to track them.</li>
+
+<li>There is initial support for virtreg sub-registers
+ (<a href="http://llvm.org/PR1350">PR1350</a>).</li>
+
</ul>
-</div>
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="c-fe">Known problems with the C front-end</a>
-</div>
+<p>
+Other improvements include:
+</p>
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">Bugs</div>
+<ul>
-<div class="doc_text">
+<li>Inline assembly support is much more solid that before.
+ The two primary features still missing are support for 80-bit floating point
+ stack registers on X86 (<a href="http://llvm.org/PR879">PR879</a>), and
+ support for inline asm in the C backend (<a
+ href="http://llvm.org/PR802">PR802</a>).</li>
+
+<li>DWARF debug information generation has been improved. LLVM now passes
+ most of the GDB testsuite on MacOS and debug info is more dense.</li>
+
+<li>Codegen support for Zero-cost DWARF exception handling has been added (<a
+ href="http://llvm.org/PR592">PR592</a>). It is mostly
+ complete and just in need of continued bug fixes and optimizations at
+ this point. However, support in llvm-g++ is disabled with an
+ #ifdef for the 2.0 release (<a
+ href="http://llvm.org/PR870">PR870</a>).</li>
+
+<li>The code generator now has more accurate and general hooks for
+ describing addressing modes ("isLegalAddressingMode") to
+ optimizations like loop strength reduction and code sinking.</li>
+
+<li>Progress has been made on a direct Mach-o .o file writer. Many small
+ apps work, but it is still not quite complete.</li>
+
+</ul>
+
+<p>In addition, the LLVM target description format has itself been extended in
+ several ways:</p>
+
<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.org/PR162">with the largest union member</a>.</li>
+<li>TargetData now supports better target parameterization in
+ the .ll/.bc files, eliminating the 'pointersize/endianness' attributes
+ in the files (<a href="http://llvm.org/PR761">PR761</a>).</li>
+
+<li>TargetData was generalized for finer grained alignment handling,
+ handling of vector alignment, and handling of preferred alignment</li>
+
+<li>LLVM now supports describing target calling conventions
+ explicitly in .td files, reducing the amount of C++ code that needs
+ to be written for a port.</li>
</ul>
-</div>
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">
- Notes
</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="specifictargets">Target-Specific
+Improvements</a></div>
+
<div class="doc_text">
+<p>X86-specific Code Generator Enhancements:
+</p>
+
<ul>
+<li>The MMX instruction set is now supported through intrinsics.</li>
+<li>The scheduler was improved to better reduce register pressure on
+ X86 and other targets that are register pressure sensitive.</li>
+<li>Linux/x86-64 support is much better.</li>
+<li>PIC support for linux/x86 has been added.</li>
+<li>The X86 backend now supports the GCC regparm attribute.</li>
+<li>LLVM now supports inline asm with multiple constraint letters per operand
+ (like "mri") which is common in X86 inline asms.</li>
+</ul>
-<li>Inline assembly is not yet supported.</li>
+<p>ARM-specific Code Generator Enhancements:</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.</li>
+<ul>
+<li>The ARM code generator is now stable and fully supported.</li>
+
+<li>There are major new features, including support for ARM
+ v4-v6 chips, vfp support, soft float point support, pre/postinc support,
+ load/store multiple generation, constant pool entry motion (to support
+ large functions), inline asm support, weak linkage support, static
+ ctor/dtor support and many bug fixes.</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>Added support for Thumb code generation (<tt>llc -march=thumb</tt>).</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>
+<li>The ARM backend now supports the ARM AAPCS/EABI ABI and PIC codegen on
+ arm/linux.</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
- the program.</p>
+<li>Several bugs were fixed for DWARF debug info generation on arm/linux.</li>
- <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>
+</ul>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
+<p>PowerPC-specific Code Generator Enhancements:</p>
- Declaring that functions have no side effects or that they can never
- return.<br>
+<ul>
+<li>The PowerPC 64 JIT now supports addressing code loaded above the 2G
+ boundary.</li>
- <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>
+<li>Improved support for the Linux/ppc ABI and the linux/ppc JIT is fully
+ functional now. llvm-gcc and static compilation are not fully supported
+ yet though.</li>
- <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>
+<li>Many PowerPC 64 bug fixes.</li>
- <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>
+</ul>
- <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>
+</div>
- <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>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="other">Other Improvements</a></div>
+<div class="doc_text">
- <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>More specific changes include:</p>
- <p>The following extensions <b>are</b> known to be supported:</p>
+<ul>
+<li>LLVM no longer relies on static destructors to shut itself down. Instead,
+ it lazily initializes itself and shuts down when <tt>llvm_shutdown()</tt> is
+ explicitly called.</li>
- <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 <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>
+<li>LLVM now has significantly fewer static constructors, reducing startup time.
+ </li>
-</ul>
+<li>Several classes have been refactored to reduce the amount of code that
+ gets linked into apps that use the JIT.</li>
-<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>
+<li>Construction of intrinsic function declarations has been simplified.</li>
-</div>
+<li>The gccas/gccld tools have been replaced with small shell scripts.</li>
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="c++-fe">Known problems with the C++ front-end</a>
+<li>Support has been added to llvm-test for running on low-memory
+ or slow machines (make SMALL_PROBLEM_SIZE=1).</li>
+
+</ul>
</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="apichanges">API Changes</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>
+<p>LLVM 2.0 contains a revamp of the type system and several other significant
+internal changes. If you are programming to the C++ API, be aware of the
+following major changes:</p>
+
+<ul>
+<li>Pass registration is slightly different in LLVM 2.0 (you now need an
+ <tt>intptr_t</tt> in your constructor), as explained in the <a
+ href="WritingAnLLVMPass.html#basiccode">Writing an LLVM Pass</a>
+ document.</li>
+
+<li><tt>ConstantBool</tt>, <tt>ConstantIntegral</tt> and <tt>ConstantInt</tt>
+ classes have been merged together, we now just have
+ <tt>ConstantInt</tt>.</li>
+
+<li><tt>Type::IntTy</tt>, <tt>Type::UIntTy</tt>, <tt>Type::SByteTy</tt>, ... are
+ replaced by <tt>Type::Int8Ty</tt>, <tt>Type::Int16Ty</tt>, etc. LLVM types
+ have always corresponded to fixed size types
+ (e.g. long was always 64-bits), but the type system no longer includes
+ information about the sign of the type. Also, the
+ <tt>Type::isPrimitiveType()</tt> method now returns false for integers.</li>
+
+<li>Several classes (<tt>CallInst</tt>, <tt>GetElementPtrInst</tt>,
+ <tt>ConstantArray</tt>, etc), that once took <tt>std::vector</tt> as
+ arguments now take ranges instead. For example, you can create a
+ <tt>GetElementPtrInst</tt> with code like:
+
+ <pre>
+ Value *Ops[] = { Op1, Op2, Op3 };
+ GEP = new GetElementPtrInst(BasePtr, Ops, 3);
+ </pre>
+
+ This avoids creation of a temporary vector (and a call to malloc/free). If
+ you have an <tt>std::vector</tt>, use code like this:
+ <pre>
+ std::vector<Value*> Ops = ...;
+ GEP = new GetElementPtrInst(BasePtr, &Ops[0], Ops.size());
+ </pre>
+
+ </li>
+
+<li><tt>CastInst</tt> is now abstract and its functionality is split into
+ several parts, one for each of the <a href="LangRef.html#convertops">new
+ cast instructions</a>.</li>
+<li><tt>Instruction::getNext()/getPrev()</tt> are now private (along with
+ <tt>BasicBlock::getNext</tt>, etc), for efficiency reasons (they are now no
+ longer just simple pointers). Please use <tt>BasicBlock::iterator</tt>, etc
+ instead.
+</li>
+
+<li><tt>Module::getNamedFunction()</tt> is now called
+ <tt>Module::getFunction()</tt>.</li>
+
+<li><tt>SymbolTable.h</tt> has been split into <tt>ValueSymbolTable.h</tt> and
+<tt>TypeSymbolTable.h</tt>.</li>
+</ul>
</div>
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">Bugs</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="portability">Portability and Supported Platforms</a>
+</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>
+<p>LLVM is known to work on the following platforms:</p>
+<ul>
+<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
+ (and probably other unix-like systems).</li>
+<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
+ 64-bit modes.</li>
+<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</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>Sun UltraSPARC workstations running Solaris 8.</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_subsubsection">
- Notes
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="knownproblems">Known Problems</a>
</div>
+<!-- *********************************************************************** -->
<div class="doc_text">
-<ul>
+<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.org/bugs/">LLVM bug database</a> and submit a bug if
+there isn't already one.</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>.</li>
+</div>
-<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>
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="experimental">Experimental features included with this release</a>
+</div>
-<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>
+<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 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
+<ul>
+<li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in in a
+ future release.</li>
+<li>C++ EH support is disabled for this release.</li>
+<li>The MSIL backend is experimental.</li>
+<li>The IA64 code generator is experimental.</li>
+<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>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="c-be">Known problems with the C back-end</a>
+ <a name="x86-be">Known problems with the X86 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 X86 backend does not yet support <a href="http://llvm.org/PR879">inline
+ assembly that uses the X86 floating point stack</a>.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="x86-be">Known problems with the X86 back-end</a>
+ <a name="ppc-be">Known problems with the PowerPC back-end</a>
</div>
<div class="doc_text">
<ul>
-<li><a href="http://llvm.org/PR566">Memory Mapped I/O Intrinsics do not fence
-memory</a></li>
+<li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
+implement ordered FP comparisons</a>.</li>
+<li>The Linux PPC32/ABI support needs testing for the interpreter and static
+compilation, and lacks support for debug information.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="ppc-be">Known problems with the PowerPC back-end</a>
+ <a name="arm-be">Known problems with the ARM back-end</a>
</div>
<div class="doc_text">
<ul>
-<li>None yet</li>
+<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
+processors, thumb program can crash 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>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
+programs compiled with LLVM. Please use more recent versions of QEMU.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="sparcv9-be">Known problems with the SparcV9 back-end</a>
+ <a name="sparc-be">Known problems with the SPARC back-end</a>
</div>
<div class="doc_text">
<ul>
-<li><a href="http://llvm.org/PR60">[sparcv9] SparcV9 backend miscompiles
-several programs in the LLVM test suite</a></li>
+<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>
appropriate nops inserted to ensure restartability.</li>
</ul>
-
</div>
<!-- ======================================================================= -->
<li>Defining vararg functions is not supported (but calling them is ok).</li>
+<li>The Itanium backend has bitrotted somewhat.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="sparcv8">Known problems with the SPARC-V8 back-end</a>
+ <a name="c-be">Known problems with the C back-end</a>
</div>
<div class="doc_text">
<ul>
-<li>Many features are still missing (e.g. support for 64-bit integer
-arithmetic). This back-end is in pre-beta state.</li>
+<li><a href="http://llvm.org/PR802">The C backend does not support inline
+ assembly code</a>.</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">
+
+<p>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time
+Optimization</a> on most platforms "out-of-the-box". Please inquire on the
+llvmdev mailing list if you are interested.</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsubsection">
+ Notes
</div>
+<div class="doc_text">
+<ul>
+
+<li><p>"long double" is silently 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>
+
+<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
+ See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
+</li>
+
+<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
+ <ol>
+ <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.<br>
+ Nested functions are supported, but llvm-gcc does not support non-local
+ gotos or taking the address of a nested function.</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>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</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>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
+ <tt>malloc</tt>, <tt>no_instrument_function</tt></li>
+ </ol>
+</li>
+
+<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
+
+ <ol>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
+ <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/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
+ Other built-in functions.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
+ Specifying attributes of variables.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</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/Variable-Length.html#Variable%20Length">Variable Length</a>:
+ Arrays whose length is computed at run time.</li>
+ <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>The C++ front-end is considered to be fully
+tested and works for a number of non-trivial programs, including LLVM
+itself, Qt, Mozilla, etc.</p>
+
+<ul>
+<li>llvm-gcc4 only has partial support for <a href="http://llvm.org/PR870">C++
+Exception Handling</a>, and it is not enabled by default.</li>
+
+<!-- NO EH Support!
+
+<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-gcc3 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_section">
<a name="additionalinfo">Additional Information</a>
<div class="doc_text">
<p>A wide variety of additional information is available on the <a
-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.
+href="http://llvm.org">LLVM web page</a>, in particular in the <a
+href="http://llvm.org/docs/">documentation</a> section. 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>
<a href="http://validator.w3.org/check/referer"><img
src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
- <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
+ <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Last modified: $Date$
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