diff options
Diffstat (limited to 'docs/ReleaseNotes.html')
| -rw-r--r-- | docs/ReleaseNotes.html | 861 |
1 files changed, 861 insertions, 0 deletions
diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html new file mode 100644 index 0000000..03d2db1 --- /dev/null +++ b/docs/ReleaseNotes.html @@ -0,0 +1,861 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" + "http://www.w3.org/TR/html4/strict.dtd"> +<html> +<head> + <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> + <link rel="stylesheet" href="llvm.css" type="text/css"> + <title>LLVM 2.0 Release Notes</title> +</head> +<body> + +<div class="doc_title">LLVM 2.0 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 2.0. 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 +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 the current or previous releases, 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 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 2.0</a> +</div> + +<!--_________________________________________________________________________--> +<div class="doc_subsubsection"><a name="majorchanges">Major Changes</a></div> +<div class="doc_text"> + +<p>Changes to the LLVM IR itself:</p> + +<ul> + +<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>Major new features:</p> + +<ul> + +<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> + +<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> + +<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_subsubsection"><a name="llvmgccfeatures">llvm-gcc +Improvements</a></div> +<div class="doc_text"> +<p>New features include: +</p> + +<ul> +<li>Precompiled Headers (PCH) are now supported.</li> + +<li>"<tt>#pragma packed</tt>" is now supported, as are the various features + described above (visibility, extern weak linkage, __thread, aliases, + etc).</li> + +<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="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> + +<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>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> + +<p> +Other improvements include: +</p> + +<ul> + +<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>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"><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> + +<p>ARM-specific Code Generator Enhancements:</p> + +<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>Added support for Thumb code generation (<tt>llc -march=thumb</tt>).</li> + +<li>The ARM backend now supports the ARM AAPCS/EABI ABI and PIC codegen on + arm/linux.</li> + +<li>Several bugs were fixed for DWARF debug info generation on arm/linux.</li> + +</ul> + +<p>PowerPC-specific Code Generator Enhancements:</p> + +<ul> +<li>The PowerPC 64 JIT now supports addressing code loaded above the 2G + boundary.</li> + +<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> + +<li>Many PowerPC 64 bug fixes.</li> + +</ul> + +</div> + + +<!--_________________________________________________________________________--> +<div class="doc_subsubsection"><a name="other">Other Improvements</a></div> +<div class="doc_text"> + +<p>More specific changes include:</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> + +<li>LLVM now has significantly fewer static constructors, reducing startup time. + </li> + +<li>Several classes have been refactored to reduce the amount of code that + gets linked into apps that use the JIT.</li> + +<li>Construction of intrinsic function declarations has been simplified.</li> + +<li>The gccas/gccld tools have been replaced with small shell scripts.</li> + +<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>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_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 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="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> +</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 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="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> +</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> +<!-- *********************************************************************** --> + +<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> + +<!-- *********************************************************************** --> + +<hr> +<address> + <a href="http://jigsaw.w3.org/css-validator/check/referer"><img + src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a> + <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/">LLVM Compiler Infrastructure</a><br> + Last modified: $Date$ +</address> + +</body> +</html> |