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| <!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 2.3 Release Notes</title> |
| </head> |
| <body> |
| |
| <div class="doc_title">LLVM 2.3 Release Notes</div> |
| |
| <ol> |
| <li><a href="#intro">Introduction</a></li> |
| <li><a href="#changes">Major Changes and Sub-project Status</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> |
| |
| <!-- Done through Week-of-Mon-20080324.txt --> |
| |
| <!-- *********************************************************************** --> |
| <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 2.3. 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="changes">Major Changes and Sub-project Status</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| |
| <p>This is the fourteenth public release of the LLVM Compiler Infrastructure. |
| It includes a large number of features and refinements from LLVM 2.2.</p> |
| |
| </div> |
| |
| <!-- Unfinished features in 2.3: |
| Machine LICM |
| Machine Sinking |
| LegalizeDAGTypes |
| --> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="changes">Major Changes in LLVM 2.3</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with |
| llvm-gcc 4.2.</p> |
| |
| <p>LLVM 2.3 no longer includes the <tt>llvm-upgrade</tt> tool. It was useful |
| for upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a |
| previous LLVM release to do this. One nice impact of this is that the LLVM |
| regression test suite no longer depends on llvm-upgrade, which makes it run |
| faster.</p> |
| |
| <p>The <tt>llvm2cpp</tt> tool has been folded into llc, use |
| <tt>llc -march=cpp</tt> instead of <tt>llvm2cpp</tt>.</p> |
| |
| <p>LLVM API Changes:</p> |
| |
| <ul> |
| <li>Several core LLVM IR classes have migrated to use the |
| '<tt>FOOCLASS::Create(...)</tt>' pattern instead of '<tt>new |
| FOOCLASS(...)</tt>' (e.g. where FOOCLASS=<tt>BasicBlock</tt>). We hope to |
| standardize on <tt>FOOCLASS::Create</tt> for all IR classes in the future, |
| but not all of them have been moved over yet.</li> |
| <li>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to |
| <a href="http://llvm.org/doxygen/classllvm_1_1IRBuilder.html">IRBuilder</a>. |
| </li> |
| <li>MRegisterInfo was renamed to |
| <a href="http://llvm.org/doxygen/classllvm_1_1TargetRegisterInfo.html"> |
| TargetRegisterInfo</a>.</li> |
| <li>The MappedFile class is gone, please use |
| <a href="http://llvm.org/doxygen/classllvm_1_1MemoryBuffer.html"> |
| MemoryBuffer</a> instead.</li> |
| <li>The '<tt>-enable-eh</tt>' flag to llc has been removed. Now code should |
| encode whether it is safe to omit unwind information for a function by |
| tagging the Function object with the '<tt>nounwind</tt>' attribute.</li> |
| <li>The ConstantFP::get method that uses APFloat now takes one argument |
| instead of two. The type argument has been removed, and the type is |
| now inferred from the size of the given APFloat value.</li> |
| |
| </ul> |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="otherprojects">Other LLVM Sub-Projects</a> |
| </div> |
| |
| <div class="doc_text"> |
| <p> |
| The core LLVM 2.3 distribution currently consists of code from the core LLVM |
| repository (which roughly contains the LLVM optimizer, 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 new <a href="#vmkit">vmkit Project</a> |
| and the <a href="#clang">Clang Project</a>. |
| </p> |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsubsection"> |
| <a name="vmkit">vmkit</a> |
| </div> |
| |
| <div class="doc_text"> |
| <p> |
| The "vmkit" project is a new addition to the LLVM family. It 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>The JVM, called JnJVM, executes real-world applications such as Apache |
| projects (e.g. Felix and Tomcat) and the SpecJVM98 benchmark. It uses the GNU |
| Classpath project for the base classes. The CLI implementation, called N3, is |
| its in early stages but can execute simple applications and the "pnetmark" |
| benchmark. It uses the pnetlib project as its core library.</p> |
| |
| <p>The 'vmkit' VMs compare in performance with industrial and top open-source |
| VMs on scientific applications. Besides the JIT, the VMs use many features of |
| the LLVM framework, including the standard set of optimizations, atomic |
| operations, custom function provider and memory manager for JITed methods, and |
| specific virtual machine optimizations. vmkit is not an official part of LLVM |
| 2.3 release. It is publicly available under the LLVM license and can be |
| downloaded from: |
| </p> |
| |
| <div class="doc_code"> |
| <pre>svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit</pre> |
| </div> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsubsection"> |
| <a name="clang">Clang</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>At this point, Clang is most useful if you are interested in source-to-source |
| transformations (such as refactoring) and other source-level tools for C and |
| Objective-C. Clang now also includes tools for turning C code into pretty HTML, |
| and includes a new <a href="http://clang.llvm.org/StaticAnalysis.html">static |
| analysis tool</a> in development. This tool focuses on automatically finding |
| bugs in C and Objective-C code.</p> |
| |
| </div> |
| |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="whatsnew">What's New?</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| |
| <p>LLVM 2.3 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 2.3 includes several major new capabilities:</p> |
| |
| <ul> |
| <li><p>The biggest change in LLVM 2.3 is Multiple Return Value (MRV) support. |
| MRVs allow LLVM IR to directly represent functions that return multiple |
| values without having to pass them "by reference" in the LLVM IR. This |
| allows a front-end to generate more efficient code, as MRVs are generally |
| returned in registers if a target supports them. See the <a |
| href="LangRef.html#i_getresult">LLVM IR Reference</a> for more details.</p> |
| |
| <p>MRVs are fully supported in the LLVM IR, but are not yet fully supported in |
| on all targets. However, it is generally safe to return up to 2 values from |
| a function: most targets should be able to handle at least that. MRV |
| support is a critical requirement for X86-64 ABI support, as X86-64 requires |
| the ability to return multiple registers from functions, and we use MRVs to |
| accomplish this in a direct way.</p></li> |
| |
| <li><p>LLVM 2.3 includes a complete reimplementation of the "<tt>llvmc</tt>" |
| tool. It is designed to overcome several problems with the original |
| <tt>llvmc</tt> and to provide a superset of the features of the |
| '<tt>gcc</tt>' driver.</p> |
| |
| <p>The main features of <tt>llvmc2</tt> are: |
| <ul> |
| <li>Extended handling of command line options and smart rules for |
| dispatching them to different tools.</li> |
| <li>Flexible (and extensible) rules for defining different tools.</li> |
| <li>The different intermediate steps performed by tools are represented |
| as edges in the abstract graph.</li> |
| <li>The 'language' for driver behavior definition is tablegen and thus |
| it's relatively easy to add new features.</li> |
| <li>The definition of driver is transformed into set of C++ classes, thus |
| no runtime interpretation is needed.</li> |
| </ul> |
| </li> |
| |
| <li><p>LLVM 2.3 includes a completely rewritten interface for <a |
| href="LinkTimeOptimization.html">Link Time Optimization</a>. This interface |
| is written in C, which allows for easier integration with C code bases, and |
| incorporates improvements we learned about from the first incarnation of the |
| interface.</p></li> |
| |
| <li><p>The <a href="tutorial/LangImpl1.html">Kaleidoscope tutorial</a> now |
| includes a "port" of the tutorial that <a |
| href="tutorial/OCamlLangImpl1.html">uses the Ocaml bindings</a> to implement |
| the Kaleidoscope language.</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 2.3 fully supports the llvm-gcc 4.2 front-end, and includes support |
| for the C, C++, Objective-C, Ada, and Fortran front-ends.</p> |
| |
| <p> |
| <ul> |
| <li>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C |
| front-end. Objective-C now works very well on Mac OS/X.</li> |
| |
| <li>Fortran <tt>EQUIVALENCE</tt>s are now supported by the gfortran |
| front-end.</li> |
| |
| <li>llvm-gcc 4.2 includes many other fixes which improve conformance with the |
| relevant parts of the GCC testsuite.</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>LLVM IR now directly represents "common" linkage, instead of representing it |
| as a form of weak linkage.</li> |
| |
| <li>LLVM IR now has support for atomic operations, and this functionality can be |
| accessed through the llvm-gcc "<tt>__sync_synchronize</tt>", |
| "<tt>__sync_val_compare_and_swap</tt>", and related builtins. Support for |
| atomics are available in the Alpha, X86, X86-64, and PowerPC backends.</li> |
| |
| <li>The C and Ocaml bindings have extended to cover pass managers, several |
| transformation passes, iteration over the LLVM IR, target data, and parameter |
| attribute lists.</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, the |
| LLVM 2.3 optimizers support a few major enhancements:</p> |
| |
| <ul> |
| |
| <li><p>Loop index set splitting on by default. |
| This transformation hoists conditions from loop bodies and reduces a loop's |
| iteration space to improve performance. For example,</p> |
| |
| <div class="doc_code"> |
| <pre> |
| for (i = LB; i < UB; ++i) |
| if (i <= NV) |
| LOOP_BODY |
| </pre> |
| </div> |
| |
| <p>is transformed into:</p> |
| |
| <p><div class="doc_code"> |
| <pre> |
| NUB = min(NV+1, UB) |
| for (i = LB; i < NUB; ++i) |
| LOOP_BODY |
| </pre> |
| </div> |
| </p> |
| </li> |
| |
| <li>LLVM now includes a new <tt>memcpy</tt> optimization pass which removes |
| dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and performs |
| return slot optimization. The LLVM optimizer now notices long sequences of |
| consecutive stores and merges them into <tt>memcpy</tt>'s where profitable.</li> |
| |
| <li>Alignment detection for vector memory references and for <tt>memcpy</tt> and |
| <tt>memset</tt> is now more aggressive.</li> |
| |
| <li>The Aggressive Dead Code Elimination (ADCE) optimization has been rewritten |
| to make it both faster and safer in the presence of code containing infinite |
| loops. Some of its prior functionality has been factored out into the loop |
| deletion pass, which <em>is</em> safe for infinite loops. The new ADCE pass is |
| no longer based on control dependence, making it run faster.</li> |
| |
| <li>The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm |
| functions for C-based languages, has been rewritten to be a FunctionPass |
| instead a ModulePass. This allows it to be run more often and to be |
| included at -O1 in llvm-gcc. It was also extended to include more |
| optimizations and several corner case bugs were fixed.</li> |
| |
| <li>LLVM now includes a simple 'Jump Threading' pass, which attempts to simplify |
| conditional branches using information about predecessor blocks, simplifying |
| the control flow graph. This pass is pretty basic at this point, but |
| catches some important cases and provides a foundation to build on.</li> |
| |
| <li>Several corner case bugs which could lead to deleting volatile memory |
| accesses have been fixed.</li> |
| |
| <li>Several optimizations have been sped up, leading to faster code generation |
| with the same code quality.</li> |
| |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="codegen">Code Generator Improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>We 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 code generator now has support for carrying information about memory |
| references throughout the entire code generation process, via the |
| <a href="http://llvm.org/doxygen/classllvm_1_1MachineMemOperand.html"> |
| MachineMemOperand</a> class. In the future this will be used to improve |
| both pre-pass and post-pass scheduling, and to improve compiler-debugging |
| output.</li> |
| |
| <li>The target-independent code generator infrastructure now uses LLVM's |
| <a href="http://llvm.org/doxygen/classllvm_1_1APInt.html">APInt</a> |
| class to handle integer values, which allows it to support integer types |
| larger than 64 bits (for example i128). Note that support for such types is |
| also dependent on target-specific support. Use of APInt is also a step |
| toward support for non-power-of-2 integer sizes.</li> |
| |
| <li>LLVM 2.3 includes several compile time speedups for code with large basic |
| blocks, particularly in the instruction selection phase, register |
| allocation, scheduling, and tail merging/jump threading.</li> |
| |
| <li>LLVM 2.3 includes several improvements which make llc's |
| <tt>--view-sunit-dags</tt> visualization of scheduling dependency graphs |
| easier to understand.</li> |
| |
| <li>The code generator allows targets to write patterns that generate subreg |
| references directly in .td files now.</li> |
| |
| <li><tt>memcpy</tt> lowering in the backend is more aggressive, particularly for |
| <tt>memcpy</tt> calls introduced by the code generator when handling |
| pass-by-value structure argument copies.</li> |
| |
| <li>Inline assembly with multiple register results now returns those results |
| directly in the appropriate registers, rather than going through memory. |
| Inline assembly that uses constraints like "ir" with immediates now use the |
| 'i' form when possible instead of always loading the value in a register. |
| This saves an instruction and reduces register use.</li> |
| |
| <li>Added support for PIC/GOT style <a |
| href="CodeGenerator.html#tailcallopt">tail calls</a> on X86/32 and initial |
| support for tail calls on PowerPC 32 (it may also work on PowerPC 64 but is |
| not thoroughly tested).</li> |
| </ul> |
| |
| </div> |
| |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="x86specific">X86/X86-64 Specific Improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| <p>New target-specific features include: |
| </p> |
| |
| <ul> |
| <li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the |
| area of passing and returning structures by value. llvm-gcc compiled code |
| now interoperates very well on X86-64 systems with other compilers.</li> |
| |
| <li>Support for Win64 was added. This includes code generation itself, JIT |
| support, and necessary changes to llvm-gcc.</li> |
| |
| <li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and |
| the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins. Various |
| generic vector operations (insert/extract/shuffle) are much more efficient |
| when SSE 4.1 is enabled. The JIT automatically takes advantage of these |
| instructions, but llvm-gcc must be explicitly told to use them, e.g. with |
| <tt>-march=penryn</tt>.</li> |
| |
| <li>The X86 backend now does a number of optimizations that aim to avoid |
| converting numbers back and forth from SSE registers to the X87 floating |
| point stack. This is important because most X86 ABIs require return values |
| to be on the X87 Floating Point stack, but most CPUs prefer computation in |
| the SSE units.</li> |
| |
| <li>The X86 backend supports stack realignment, which is particularly useful for |
| vector code on OS's without 16-byte aligned stacks, such as Linux and |
| Windows.</li> |
| |
| <li>The X86 backend now supports the "sseregparm" options in GCC, which allow |
| functions to be tagged as passing floating point values in SSE |
| registers.</li> |
| |
| <li>Trampolines (taking the address of a nested function) now work on |
| Linux/X86-64.</li> |
| |
| <li><tt>__builtin_prefetch</tt> is now compiled into the appropriate prefetch |
| instructions instead of being ignored.</li> |
| |
| <li>128-bit integers are now supported on X86-64 targets. This can be used |
| through <tt>__attribute__((TImode))</tt> in llvm-gcc.</li> |
| |
| <li>The register allocator can now rematerialize PIC-base computations, which is |
| an important optimization for register use.</li> |
| |
| <li>The "t" and "f" inline assembly constraints for the X87 floating point stack |
| now work. However, the "u" constraint is still not fully supported.</li> |
| |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="targetspecific">Other Target Specific Improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| <p>New target-specific features include: |
| </p> |
| |
| <ul> |
| <li>The LLVM C backend now supports vector code.</li> |
| <li>The Cell SPU backend includes a number of improvements. It generates better |
| code and its stability/completeness is improving.</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>LLVM now builds with GCC 4.3.</li> |
| <li>Bugpoint now supports running custom scripts (with the <tt>-run-custom</tt> |
| option) to determine how to execute the command and whether it is making |
| forward process.</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, and MIPS 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 position-independent code (PIC) |
| generation on Linux targets.</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="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, including |
| X86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is |
| supported on X86-64 linux, but that is disabled by default in this release.</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 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests |
| fail (c380004 also fails with gcc-4.2 mainline). When built at -O3, the |
| <a href="http://llvm.org/PR2421">cxg2021</a> ACATS test also fails.</li> |
| <li>Some gcc specific Ada tests continue to crash the compiler. The testsuite |
| reports most tests as having failed even though they pass.</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> |
| |
| <!-- *********************************************************************** --> |
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