| <!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 2.4 Release Notes</title> |
| </head> |
| <body> |
| |
| <div class="doc_title">LLVM 2.4 Release Notes</div> |
| |
| <ol> |
| <li><a href="#intro">Introduction</a></li> |
| <li><a href="#subproj">Sub-project Status Update</a></li> |
| <li><a href="#whatsnew">What's New in LLVM?</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> |
| <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 2.4. Here we describe the status of LLVM, including |
| major improvements from the previous release and significant 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 release, please see the |
| <a href="http://llvm.org/releases/">releases page</a>.</p> |
| |
| </div> |
| |
| <!-- Unfinished features in 2.4: |
| Machine LICM |
| Machine Sinking |
| LegalizeDAGTypes |
| llc -enable-value-prop, propagation of value info (sign/zero ext info) from |
| one MBB to another |
| --> |
| |
| <!-- for announcement email: |
| mention dev mtg |
| Xcode 3.1 and 3.1.1. |
| --> |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="subproj">Sub-project Status Update</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| <p> |
| The LLVM 2.4 distribution currently consists of code from the core LLVM |
| repository (which roughly includes the LLVM optimizers, code generators and |
| supporting tools) and the llvm-gcc repository. In addition to this code, the |
| LLVM Project includes other sub-projects that are in development. The two which |
| are the most actively developed are the <a href="#clang">Clang Project</a> and |
| the <a href="#vmkit">VMKit Project</a>. |
| </p> |
| |
| </div> |
| |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build |
| a set of new 'LLVM native' front-end technologies for the LLVM optimizer |
| and code generator. Clang is continuing to make major strides forward in all |
| areas. Its C and Objective-C parsing support is very solid, and the code |
| generation support is far enough along to build many C applications. While not |
| yet production quality, it is progressing very nicely. In addition, C++ |
| front-end work has started to make significant progress.</p> |
| |
| <p>Clang, in conjunction with the <tt>ccc</tt> driver, is now usable as a |
| replacement for gcc for building some small- to medium-sized C applications. |
| Additionally, Clang now has code generation support for Objective-C on Mac OS X |
| platform. Major highlights include:</p> |
| |
| <ul> |
| <li> Clang/ccc pass almost all of the LLVM test suite on Mac OS X and Linux |
| on the 32-bit x86 architecture. This includes significant C |
| applications such as <a href="http://www.sqlite.org">sqlite3</a>, |
| <a href="http://www.lua.org">lua</a>, and |
| <a href="http://www.clamav.net">Clam AntiVirus</a>. </li> |
| |
| <li> Clang can build the majority of Objective-C examples shipped with the |
| Mac OS X Developer Tools. </li> |
| </ul> |
| |
| <p>Clang code generation still needs considerable testing and development, |
| however. Some areas under active development include:</p> |
| |
| <ul> |
| <li> Improved support for C and Objective-C features, for example |
| variable-length arrays, va_arg, exception handling (Obj-C), and garbage |
| collection (Obj-C). </li> |
| <li> ABI compatibility, especially for platforms other than 32-bit |
| x86. </li> |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="clangsa">Clang Static Analyzer</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>The Clang project also includes an early stage static source code analysis |
| tool for <a href="http://clang.llvm.org/StaticAnalysis.html">automatically |
| finding bugs</a> in C and Objective-C programs. The tool performs a growing set |
| of checks to find bugs that occur on a specific path within a program. Examples |
| of bugs the tool finds include logic errors such as null dereferences, |
| violations of various API rules, dead code, and potential memory leaks in |
| Objective-C programs. Since its inception, public feedback on the tool has been |
| extremely positive, and conservative estimates put the number of real bugs it |
| has found in industrial-quality software on the order of thousands.</p> |
| |
| <p>The tool also provides a simple web GUI to inspect potential bugs found by |
| the tool. While still early in development, the GUI illustrates some of the key |
| features of Clang: accurate source location information, which is used by the |
| GUI to highlight specific code expressions that relate to a bug (including those |
| that span multiple lines); and built-in knowledge of macros, which is used to |
| perform inline expansion of macros within the GUI itself.</p> |
| |
| <p>The set of checks performed by the static analyzer is gradually expanding, |
| and future plans for the tool include full source-level inter-procedural |
| analysis and deeper checks such as buffer overrun detection. There are many |
| opportunities to extend and enhance the static analyzer, and anyone interested |
| in working on this project is encouraged to get involved!</p> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a> |
| </div> |
| |
| <div class="doc_text"> |
| <p> |
| The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of |
| a JVM and a CLI Virtual Machines (Microsoft .NET is an |
| implementation of the CLI) using the Just-In-Time compiler of LLVM.</p> |
| |
| <p>Following LLVM 2.4, VMKit has its first release 0.24 that you can find on its |
| <a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes |
| bug fixes, cleanup and new features. The major changes are:</p> |
| |
| <ul> |
| |
| <li> Support for generics in the .Net virtual machine.</li> |
| <li> Initial support for the Mono class libraries. </li> |
| <li> Support for MacOSX/x86, following LLVM's support for exceptions in |
| JIT on MacOSX/x86. </li> |
| <li> A new vmkit driver: a program to run java or .net applications. The driver |
| supports llvm command line arguments including the new "-fast" option. </li> |
| <li> A new memory allocation scheme in the JVM that makes unloading a |
| class loader very fast. </li> |
| <li> VMKit now follows the LLVM Makefile machinery. </li> |
| |
| </ul> |
| </div> |
| |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="whatsnew">What's New in LLVM?</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| |
| <p>This release includes a huge number of bug fixes, performance tweaks, and |
| minor improvements. Some of the major improvements and new features are listed |
| in this section. |
| </p> |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="majorfeatures">Major New Features</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>LLVM 2.4 includes several major new capabilities:</p> |
| |
| <ul> |
| <li><p>The most visible end-user change in LLVM 2.4 is that it includes many |
| optimizations and changes to make -O0 compile times much faster. You should see |
| improvements in speed on the order of 30% (or more) than in LLVM 2.3. There are |
| many pieces to this change described in more detail below. The speedups and new |
| components can also be used for JIT compilers that want fast |
| compilation.</p></li> |
| |
| <li><p>The biggest change to the LLVM IR is that Multiple Return Values (which |
| were introduced in LLVM 2.3) have been generalized to full support for "First |
| Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using |
| structs and arrays as values in a function. This capability is mostly useful |
| for front-end authors, who prefer to treat things like complex numbers, simple |
| tuples, dope vectors, etc., as Value*'s instead of as a tuple of Value*'s or as |
| memory values. Bitcode files from LLVM 2.3 will automatically migrate to the |
| general representation.</p></li> |
| |
| <li><p>LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This |
| target only has support for 8 bit registers, and a number of other crazy |
| constraints. While the port is still in early development stages, it shows some |
| interesting things you can do with LLVM.</p></li> |
| |
| </ul> |
| |
| </div> |
| |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC |
| front-ends and driver with the LLVM optimizer and code generator. It currently |
| includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p> |
| |
| <ul> |
| <li>LLVM 2.4 supports the full set of atomic <tt>__sync_*</tt> builtins. LLVM |
| 2.3 only supported those used by OpenMP, but 2.4 supports them all. Note that |
| while llvm-gcc supports all of these builtins, not all targets do. X86 support |
| them all in both 32-bit and 64-bit mode and PowerPC supports them all except for |
| the 64-bit operations when in 32-bit mode.</li> |
| |
| <li>llvm-gcc now supports an <tt>-flimited-precision</tt> option, which tells |
| the compiler that it is okay to use low-precision approximations of certain libm |
| functions (like <tt>exp</tt>, <tt>log</tt>, etc). This allows you to get high |
| performance if you only need (say) 12-bits of precision.</li> |
| |
| <li>llvm-gcc now supports a C language extension known as "<a |
| href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks</a>". |
| This feature is similar to nested functions and closures, but does not |
| require stack trampolines (with most ABIs), and supports returning closures |
| from functions that define them. Note that actually <em>using</em> Blocks |
| requires a small runtime that is not included with llvm-gcc.</li> |
| |
| <li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support |
| transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and |
| later) this allows the use of LTO with other optimization levels like -Os. |
| Previously, LTO could only be used with -O4, which implied optimizations in |
| -O3 that can increase code size.</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>A major change to the <tt>Use</tt> class landed, which shrank it by 25%. Since |
| this is a pervasive part of the LLVM, it ended up reducing the memory use of |
| LLVM IR in general by 15% for most programs.</li> |
| |
| <li>Values with no names are now pretty printed by <tt>llvm-dis</tt> more |
| nicely. They now print as "<tt>%3 = add i32 %A, 4</tt>" instead of |
| "<tt>add i32 %A, 4 ; <i32>:3</tt>", which makes it much easier to read. |
| </li> |
| |
| <li>LLVM 2.4 includes some changes for better vector support. First, the shift |
| operations (<tt>shl</tt>, <tt>ashr</tt>, and <tt>lshr</tt>) now all support |
| vectors and do an element-by-element shift (shifts of the whole vector can be |
| accomplished by bitcasting the vector to <1 x i128>, for example). Second, |
| there is initial support in development for vector comparisons with the |
| <tt><a href="LangRef.html#i_fcmp">fcmp</a>/<a href="LangRef.html#i_icmp">icmp</a></tt> |
| instructions. These instructions compare two vectors and return a vector of |
| <tt>i1</tt>'s for each result. Note that there is very little codegen support |
| available for any of these IR features though.</li> |
| |
| <li>A new <tt>DebugInfoBuilder</tt> class is available, which makes it much |
| easier for front-ends to create debug info descriptors, similar to the way that |
| <tt>IRBuilder</tt> makes it easier to create LLVM IR.</li> |
| |
| <li>The <tt>IRBuilder</tt> class is now parameterized by a class responsible |
| for constant folding. The default <tt>ConstantFolder</tt> class does target independent |
| constant folding. The <tt>NoFolder</tt> class does no constant folding at all, which is |
| useful when learning how LLVM works. The <tt>TargetFolder</tt> class folds the most, |
| doing target dependent constant folding.</li> |
| |
| <li>LLVM now supports "function attributes", which allow us to separate return |
| value attributes from function attributes. LLVM now supports attributes on a |
| function itself, a return value, and its parameters. New supported function |
| attributes include <tt>noinline/alwaysinline</tt> and the <tt>opt-size</tt> flag, |
| which says the function should be optimized for code size.</li> |
| |
| <li>LLVM IR now directly represents "common" linkage, instead of |
| representing it as a form of weak linkage.</li> |
| |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="optimizer">Optimizer Improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>In addition to a huge array of bug fixes and minor performance tweaks, this |
| release includes a few major enhancements and additions to the optimizers:</p> |
| |
| <ul> |
| |
| <li>The Global Value Numbering (GVN) pass now does local Partial Redundancy |
| Elimination (PRE) to eliminate some partially redundant expressions in cases |
| where doing so won't grow code size.</li> |
| |
| <li>LLVM 2.4 includes a new loop deletion pass (which removes output-free |
| provably-finite loops) and a rewritten Aggressive Dead Code Elimination (ADCE) |
| pass that no longer uses control dependence information. These changes speed up |
| the optimizer and also prevent it from deleting output-free infinite |
| loops.</li> |
| |
| <li>The new AddReadAttrs pass works out which functions are read-only or |
| read-none (these correspond to 'pure' and 'const' in GCC) and marks them |
| with the appropriate attribute.</li> |
| |
| <li>LLVM 2.4 now includes a new SparsePropagation framework, which makes it |
| trivial to build lattice-based dataflow solvers that operate over LLVM IR. Using |
| this interface means that you just define objects to represent your lattice |
| values and the transfer functions that operate on them. It handles the |
| mechanics of worklist processing, liveness tracking, handling PHI nodes, |
| etc.</li> |
| |
| <li>The Loop Strength Reduction and induction variable optimization passes have |
| several improvements to avoid inserting MAX expressions, to optimize simple |
| floating point induction variables and to analyze trip counts of more |
| loops.</li> |
| |
| <li>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were |
| pulled out of the Instruction Combining pass and put into a new |
| <tt>ValueTracking.h</tt> header, where they can be reused by other passes.</li> |
| |
| <li>The tail duplication pass has been removed from the standard optimizer |
| sequence used by llvm-gcc. This pass still exists, but the benefits it once |
| provided are now achieved by other passes.</li> |
| |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="codegen">Code Generator Improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>We have put a significant amount of work into the code generator infrastructure, |
| which allows us to implement more aggressive algorithms and make it run |
| faster:</p> |
| |
| <ul> |
| <li>The target-independent code generator supports (and the X86 backend |
| currently implements) a new interface for "fast" instruction selection. This |
| interface is optimized to produce code as quickly as possible, sacrificing |
| code quality to do it. This is used by default at -O0 or when using |
| "llc -fast" on X86. It is straight-forward to add support for |
| other targets if faster -O0 compilation is desired.</li> |
| |
| <li>In addition to the new 'fast' instruction selection path, many existing |
| pieces of the code generator have been optimized in significant ways. |
| SelectionDAG's are now pool allocated and use better algorithms in many |
| places, the ".s" file printers now use <tt>raw_ostream</tt> to emit text much faster, |
| etc. The end result of these improvements is that the compiler also takes |
| substantially less time to generate code that is just as good (and often |
| better) than before.</li> |
| |
| <li>Each target has been split to separate the ".s" file printing logic from the |
| rest of the target. This enables JIT compilers that don't link in the |
| (somewhat large) code and data tables used for printing a ".s" file.</li> |
| |
| <li>The code generator now includes a "stack slot coloring" pass, which packs |
| together individual spilled values into common stack slots. This reduces |
| the size of stack frames with many spills, which tends to increase L1 cache |
| effectiveness.</li> |
| |
| <li>Various pieces of the register allocator (e.g. the coalescer and two-address |
| operation elimination pass) now know how to rematerialize trivial operations |
| to avoid copies and include several other optimizations.</li> |
| |
| <li>The <a href="CodeGenerator.html#selectiondag_process">graphs</a> produced by |
| the <tt>llc -view-*-dags</tt> options are now significantly prettier and |
| easier to read.</li> |
| |
| <li>LLVM 2.4 includes a new register allocator based on Partitioned Boolean |
| Quadratic Programming (PBQP). This register allocator is still in |
| development, but is very simple and clean.</li> |
| |
| </ul> |
| |
| </div> |
| |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="targetspecific">Target Specific Improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| <p>New target-specific features include: |
| </p> |
| |
| <ul> |
| <li>Exception handling is supported by default on Linux/x86-64.</li> |
| <li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li> |
| <li><tt>@llvm.frameaddress</tt> now supports getting the frame address of stack frames |
| > 0 on x86/x86-64.</li> |
| <li>MIPS has improved a lot since last release, the most important changes |
| are: Little endian support, floating point support, allegrex core and |
| intrinsics support. O32 ABI is improved but isn't complete. The EABI |
| was implemented and is fully supported. We also have support for small |
| sections and gp_rel relocation for its access, a threshold in bytes can be |
| specified through command line.</li> |
| <li>The PowerPC backend now supports trampolines.</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><tt>llvmc2</tt> (the generic compiler driver) gained plugin |
| support. It is now easier to experiment with <tt>llvmc2</tt> and |
| build your own tools based on it.</li> |
| |
| <li>LLVM 2.4 includes a number of new generic algorithms and data structures, |
| include a scoped hash table, 'immutable' data structures, a simple |
| free-list manager, and a <tt>raw_ostream</tt> class. |
| The <tt>raw_ostream</tt> class and |
| <tt>format</tt> allow for efficient file output, and various pieces of LLVM |
| have switched over to use it. The eventual goal is to eliminate |
| std::ostream in favor of it.</li> |
| |
| <li>LLVM 2.4 includes an optional build system based on CMake. It |
| still is in its early stages but can be useful for Visual C++ |
| users who can not use the Visual Studio IDE.</li> |
| |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="changes">Major Changes and Removed Features</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>If you're already an LLVM user or developer with out-of-tree changes based |
| on LLVM 2.3, this section lists some "gotchas" that you may run into upgrading |
| from the previous release.</p> |
| |
| <ul> |
| |
| <li>The LLVM IR generated by llvm-gcc no longer names all instructions. This |
| makes it run faster, but may be more confusing to some people. If you |
| prefer to have names, the '<tt>opt -instnamer</tt>' pass will add names to |
| all instructions.</li> |
| |
| <li>The LoadVN and GCSE passes have been removed from the tree. They are |
| obsolete and have been replaced with the GVN and MemoryDependence passes. |
| </li> |
| </ul> |
| |
| |
| <p>In addition, many APIs have changed in this release. Some of the major LLVM |
| API changes are:</p> |
| |
| <ul> |
| |
| <li>Now, function attributes and return value attributes are managed |
| separately. Interface exported by <tt>ParameterAttributes.h</tt> header is now |
| experted by <tt>Attributes.h</tt> header. The new attributes interface changes are: |
| <ul> |
| <li><tt>getParamAttrs</tt> method is now replaced by |
| <tt>getParamAttributes</tt>, <tt>getRetAttributes</tt> and |
| <tt>getFnAttributes</tt> methods.</li> |
| <li> Return value attributes are stored at index 0. Function attributes are |
| stored at index ~0U. Parameter attributes are stored at index that matches |
| parameter number.</li> |
| <li> <tt>ParamAttr</tt> namespace is now renamed as <tt>Attribute</tt>.</li> |
| <li> The name of the class that manages reference count of opaque |
| attributes is changed from <tt>PAListPtr</tt> to <tt>AttrListPtr</tt>.</li> |
| <li> <tt>ParamAttrsWithIndex</tt> is now renamed as <tt>AttributeWithIndex</tt>. |
| </li> |
| </ul> |
| </li> |
| |
| <li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and |
| <tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be |
| converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via |
| "<tt>llvm/Analysis/ValueTracking.h</tt>".</li> |
| |
| <li>The APIs to create various instructions have changed from lower case |
| "create" methods to upper case "Create" methods (e.g. |
| <tt>BinaryOperator::create</tt>). LLVM 2.4 includes both cases, but the |
| lower case ones are removed in mainline, please migrate.</li> |
| |
| <li>Various header files like "<tt>llvm/ADT/iterator</tt>" were given a ".h" suffix. |
| Change your code to #include "<tt>llvm/ADT/iterator.h</tt>" instead.</li> |
| |
| <li>The <tt>getresult</tt> instruction has been removed and replaced with the |
| <tt>extractvalue</tt> instruction. This is part of support for first class |
| aggregates.</li> |
| |
| <li>In the code generator, many <tt>MachineOperand</tt> predicates were renamed to be |
| shorter (e.g. <tt>isFrameIndex()</tt> -> <tt>isFI()</tt>), |
| <tt>SDOperand</tt> was renamed to <tt>SDValue</tt> (and the "<tt>Val</tt>" |
| member was changed to be the <tt>getNode()</tt> accessor), and the |
| <tt>MVT::ValueType</tt> enum has been replaced with an "<tt>MVT</tt>" |
| struct. The <tt>getSignExtended</tt> and <tt>getValue</tt> methods in the |
| ConstantSDNode class were renamed to <tt>getSExtValue</tt> and |
| <tt>getZExtValue</tt> respectively, to be more consistent with |
| the <tt>ConstantInt</tt> class.</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 (IA32) 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 10.3 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 10.</li> |
| <li>Alpha-based machines running Debian GNU/Linux.</li> |
| <li>Itanium-based (IA64) machines running Linux and HP-UX.</li> |
| </ul> |
| |
| <p>The core LLVM infrastructure uses GNU autoconf 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 MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li> |
| <li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported |
| value for this 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 |
| all <a href="http://llvm.org/PR879">inline assembly that uses the X86 |
| floating point stack</a>. It supports the 'f' and 't' constraints, but not |
| 'u'.</li> |
| <li>The X86 backend generates inefficient floating point code when configured |
| to generate code for systems that don't have SSE2.</li> |
| <li>Win64 code generation wasn't widely tested. Everything should work, but we |
| expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime |
| currently due |
| to <a href="http://llvm.org/PR2255">several</a> |
| <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the |
| 'u' inline assembly constraint and X87 floating point inline assembly.</li> |
| <li>The X86-64 backend does not yet support the LLVM IR instruction |
| <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic |
| argument constructs on X86-64 by lowering them manually.</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>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="mips-be">Known problems with the MIPS back-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| <li>The O32 ABI is not fully supported.</li> |
| <li>64-bit MIPS targets are not supported yet.</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>The Itanium backend is highly experimental, and has a number of known |
| issues. We are looking for a maintainer for the Itanium backend. If you |
| are interested, please contact the LLVMdev mailing list.</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 has only basic support for |
| inline assembly code</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> |
| <li>The C backend does not support all exception handling constructs.</li> |
| </ul> |
| |
| </div> |
| |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="c-fe">Known problems with the llvm-gcc C front-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>llvm-gcc 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> |
| |
| <p>The only major language feature of GCC not supported by llvm-gcc is |
| the <tt>__builtin_apply</tt> family of builtins. However, some extensions |
| are only supported on some targets. For example, trampolines are only |
| supported on some targets (these are used when you take the address of a |
| nested function).</p> |
| |
| <p>If you run into GCC extensions which are not supported, please let us know. |
| </p> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="c++-fe">Known problems with the llvm-gcc 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 works well on the X86 and PowerPC targets. Currently |
| only linux and darwin targets are supported (both 32 and 64 bit).</li> |
| </ul> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| <ul> |
| <li>Fortran support generally works, but there are still several unresolved bugs |
| in Bugzilla. Please see the tools/gfortran component for details.</li> |
| |
| <li>The Fortran front-end currently does not build on Darwin (without tweaks) |
| due to unresolved dependencies on the C front-end.</li> |
| </ul> |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature |
| technology and problems should be expected. |
| <ul> |
| <li>The Ada front-end currently only builds on X86-32. This is mainly due |
| to lack of trampoline support (pointers to nested functions) on other platforms, |
| however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a> |
| which does support trampolines.</li> |
| <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>. |
| Workaround: configure with --disable-bootstrap.</li> |
| <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a> |
| and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail |
| (c380004 also fails with gcc-4.2 mainline).</li> |
| <li>Some gcc specific Ada tests continue to crash the compiler.</li> |
| <li>The -E binder option (exception backtraces) |
| <a href="http://llvm.org/PR1982">does not work</a> and will result in programs |
| crashing if an exception is raised. Workaround: do not use -E.</li> |
| <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start |
| or finish at a non-byte offset</a> in a record. Workaround: do not pack records |
| or use representation clauses that result in a field of a non-discrete type |
| starting or finishing in the middle of a byte.</li> |
| <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers |
| 'main' as generated by the Ada binder to be invalid</a>. |
| Workaround: hand edit the file to use pointers for <tt>argv</tt> and |
| <tt>envp</tt> rather than integers.</li> |
| <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is |
| ignored</a>.</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> |