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| <body> | |
| <div class="doc_title">LLVM 2.1 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.org">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 2.1. 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 | |
| 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 a Subversion checkout 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 a specific releases, please see the | |
| <a href="http://llvm.org/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 twelfth public release of the LLVM Compiler Infrastructure. | |
| It includes many features and refinements from LLVM 2.0.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="frontends">New Frontends</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM 2.1 brings two new beta C front-ends. First, a new version of llvm-gcc | |
| based on GCC 4.2, innovatively called "llvm-gcc-4.2". This promises to bring | |
| FORTRAN and Ada support to LLVM as well as features like atomic builtins and | |
| OpenMP. None of these actually work yet, but don't let that stop you checking | |
| it out!</p> | |
| <p>Second, LLVM now includes its own native C and Objective-C front-end (C++ is | |
| in progress, but is not very far along) code named "<a | |
| href="http://clang.llvm.org/">clang</a>". This front-end has a number of great | |
| features, primarily aimed at source-level analysis and speeding up compile-time. | |
| At this point though, the LLVM Code Generator component is still very early in | |
| development, so it's mostly useful for people looking to build source-level | |
| analysis tools or source-to-source translators.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="optimizer">Optimizer Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>Some of the most noticable feature improvements this release have been in the | |
| optimizer, speeding it up and making it more aggressive. For example:</p> | |
| <ul> | |
| <li>Owen Anderson wrote the new MemoryDependenceAnalysis pass, which provides | |
| a lazy, caching layer on top of <a | |
| href="AliasAnalysis.html">AliasAnalysis</a>. He then used it to rewrite | |
| DeadStoreElimination which resulted in significantly better compile time in | |
| common cases, </li> | |
| <li>Owen implemented the new GVN pass, which is also based on | |
| MemoryDependenceAnalysis. This pass replaces GCSE/LoadVN in the standard | |
| set of passes, providing more aggressive optimization at a some-what | |
| improved compile-time cost.</li> | |
| <li>Owen implemented GVN-PRE, a partial redundancy elimination algorithm that | |
| shares some details with the new GVN pass. It is still in need of compile | |
| time tuning, and is not turned on by default.</li> | |
| <li>Devang merged ETForest and DomTree into a single easier to use data | |
| structure. This makes it more obvious which datastructure to choose | |
| (because there is only one) and makes the compiler more memory and time | |
| efficient (less stuff to keep up-to-date).</li> | |
| <li>Nick Lewycky improved loop trip count analysis to handle many more common | |
| cases.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="codegen">Code Generator Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>One of the main focuses of this release was performance tuning and bug | |
| fixing. In addition to these, several new major changes occurred:</p> | |
| <ul> | |
| <li>Dale finished up the Tail Merging optimization in the code generator, and | |
| enabled it by default. This produces smaller code that is also faster in | |
| some cases.</li> | |
| <li>Christopher Lamb implemented support for virtual register sub-registers, | |
| which can be used to better model many forms of subregisters. As an example | |
| use, he modified the X86 backend to use this to model truncates and | |
| extends more accurately (leading to better code).</li> | |
| <li>Dan Gohman changed the way we represent vectors before legalization, | |
| significantly simplifying the SelectionDAG representation for these and | |
| making the code generator faster for vector code.</li> | |
| <li>Evan contributed a new target independent if-converter. While it is | |
| target independent, so far only the ARM backend uses it.</li> | |
| <li>Evan rewrite the way the register allocator handles rematerialization, | |
| allowing it to be much more effective on two-address targets like X86, | |
| and taught it to fold loads away when possible (also a big win on X86).</li> | |
| <li>Dan Gohman contributed support for better alignment and volatility handling | |
| in the code generator, and significantly enhanced alignment analysis for SSE | |
| load/store instructions. With his changes, an insufficiently-aligned SSE | |
| load instruction turns into <tt>movups</tt>, for example.</li> | |
| <li>Duraid Madina contributed a new "bigblock" register allocator, and Roman | |
| Levenstein contributed several big improvements. BigBlock is optimized for | |
| code that uses very large basic blocks. It is slightly slower than the | |
| "local" allocator, but produces much better code.</li> | |
| <li>David Greene refactored the register allocator to split coalescing out from | |
| allocation, making coalescers pluggable.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="targetspecific">Target Specific Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>New features include: | |
| </p> | |
| <ul> | |
| <li>Bruno Cardoso Lopes contributed initial MIPS support. It is sufficient to | |
| run many small programs, but is still incomplete and is not yet | |
| fully performant.</li> | |
| <li>Bill Wendling added SSSE3 support to the X86 backend.</li> | |
| <li>Nicholas Geoffray contributed improved linux/ppc ABI and JIT support.</li> | |
| <li>Dale Johannesen rewrote handling of 32-bit float values in the X86 backend | |
| when using the floating point stack, fixing several nasty bugs.</li> | |
| <li>Dan contributed rematerialization support for the X86 backend, in addition | |
| to several X86-specific micro optimizations.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="llvmgccimprovements">llvm-gcc Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>New features include: | |
| </p> | |
| <ul> | |
| <li>Duncan and Anton made significant progress chasing down a number of problems | |
| with C++ Zero-Cost exception handling in llvm-gcc 4.0 and 4.2. It is now at | |
| the point where it "just works" on linux/X86-32 and has partial support on | |
| other targets.</li> | |
| <li>Devang and Duncan fixed a huge number of bugs relating to bitfields, pragma | |
| pack, and variable sized fields in structures.</li> | |
| <li>Tanya implemented support for <tt>__attribute__((noinline))</tt> in | |
| llvm-gcc, and added support for generic variable annotations which are | |
| propagated into the LLVM IR, e.g. | |
| "<tt>int X __attribute__((annotate("myproperty")));</tt>".</li> | |
| <li>Sheng Zhou and Christopher Lamb implemented alias analysis support for | |
| "restrict" pointer arguments to functions.</li> | |
| <li>Duncan contributed support for trampolines (taking the address of a nested | |
| function). Currently this is only supported on the X86-32 target.</li> | |
| <li>Lauro Ramos Venancio contributed support to encode alignment info in | |
| load and store instructions, the foundation for other alignment-related | |
| work.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="coreimprovements">LLVM Core Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>New features include: | |
| </p> | |
| <ul> | |
| <li>Neil Booth contributed a new "APFloat" class, which ensures that floating | |
| point representation and constant folding is not dependent on the host | |
| architecture that builds the application. This support is the foundation | |
| for "long double" support that will be wrapped up in LLVM 2.2.</li> | |
| <li>Based on the APFloat class, Dale redesigned the internals of the ConstantFP | |
| class and has been working on extending the core and optimizer components to | |
| support various target-specific 'long double's. We expect this work to be | |
| completed in LLVM 2.2.</li> | |
| <li>LLVM now provides an LLVMBuilder class, which makes it significantly easier | |
| to create LLVM IR instructions.</li> | |
| <li>Reid contributed support for intrinsics that take arbitrary integer typed | |
| arguments. Dan Gohman and Chandler extended it to support arbitrary | |
| floating point arguments and vectors.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="otherimprovements">Other Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>New features include: | |
| </p> | |
| <ul> | |
| <li>Sterling Stein contributed a new BrainF frontend, located in llvm/examples. | |
| This shows a some of the more modern APIs for building a front-end, and | |
| demonstrates JIT compiler support.</li> | |
| <li>David Green contributed a new <tt>--enable-expensive-checks</tt> configure | |
| option which enables STL checking, and fixed several bugs exposed by | |
| it.</li> | |
| </ul> | |
| </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, 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_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.org/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 <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 a | |
| future release.</li> | |
| <li>The MSIL backend is experimental.</li> | |
| <li>The IA64 code generator is experimental.</li> | |
| <li>The Alpha backend 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="x86-be">Known problems with the X86 back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <ul> | |
| <li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline | |
| assembly that uses the X86 floating point stack</a>.</li> | |
| <li>The X86 backend occasionally has <a href="http://llvm.org/PR1649">alignment | |
| problems</a> on operating systems that don't require 16-byte stack alignment | |
| (including most non-darwin OS's like linux).</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><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="arm-be">Known problems with the ARM back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <ul> | |
| <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6 | |
| processors, thumb programs can crash or produce 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="sparc-be">Known problems with the SPARC back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <ul> | |
| <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not | |
| support the 64-bit SPARC ABI (-m64).</li> | |
| </ul> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <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 arithmetic sequences which may trap do not have the | |
| appropriate nops inserted to ensure restartability.</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>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64 | |
| ABI compliant layout of v-tables</a>. In particular, it just stores function | |
| pointers instead of function descriptors in the vtable. This bug prevents | |
| mixing C++ code compiled with LLVM with C++ objects compiled by other C++ | |
| compilers.</li> | |
| <li>There are a few ABI violations which will lead to problems when mixing LLVM | |
| output with code built with other compilers, particularly for floating-point | |
| programs.</li> | |
| <li>Defining vararg functions is not supported (but calling them is ok).</li> | |
| <li>The Itanium backend has bitrotted somewhat.</li> | |
| </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><a href="http://llvm.org/PR802">The C backend does not support inline | |
| assembly code</a>.</li> | |
| <li><a href="http://llvm.org/PR1126">The C backend does not support vectors | |
| yet</a>.</li> | |
| <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common | |
| C++ programs</a>, preventing intermixing between C++ compiled by the CBE and | |
| C++ code compiled with LLC or native compilers.</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. | |
| Nested functions are supported, but llvm-gcc does not support | |
| taking the address of a nested function (except on the X86-32 target) | |
| or non-local gotos.</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>noinline</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>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>Exception handling only works well on the linux/X86-32 target. | |
| In some cases, illegally throwing an exception does not result | |
| in a call to terminate.</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> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>A wide variety of additional information is available on the <a | |
| 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 | |
| Subversion 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://llvm.org/docs/#maillist"> mailing | |
| lists</a>.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
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