LLVM 2.3 Release Notes
  1. Introduction
  2. Major Changes and Sub-project Status
  3. What's New?
  4. Installation Instructions
  5. Portability and Supported Platforms
  6. Known Problems
  7. Additional Information

Written by the LLVM Team


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 LLVM releases web site.

For more information about LLVM, including information about the latest release, please check out the main LLVM web site. If you have questions or comments, the LLVM developer's mailing list is a good place to send them.

Note that if you are reading this file from a Subversion checkout or the main LLVM web page, this document applies to the next release, not the current one. To see the release notes for a specific releases, please see the releases page.

Major Changes and Sub-project Status

This is the fourteenth public release of the LLVM Compiler Infrastructure. It includes a large number of features and refinements from LLVM 2.2.

Major Changes in LLVM 2.3

LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with llvm-gcc 4.2.

LLVM 2.3 no longer includes the llvm-upgrade 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.

The llvm2cpp tool has been folded into llc, use llc -march=cpp instead of llvm2cpp.

LLVM API Changes:

Other LLVM Sub-Projects

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 vmkit Project and the Clang Project.


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.

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.

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:

svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit


The Clang project 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.

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 static analysis tool in development. This tool focuses on automatically finding bugs in C and Objective-C code.

What's New?

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.

Major New Features

LLVM 2.3 includes several major new capabilities:

llvm-gcc 4.2 Improvements

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.

LLVM Core Improvements

New features include:

Optimizer Improvements

In addition to a huge array of bug fixes and minor performance tweaks, the LLVM 2.3 optimizers support a few major enhancements:

Code Generator Improvements

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:

X86/X86-64 Specific Improvements

New target-specific features include:

Other Target Specific Improvements

New target-specific features include:

Other Improvements

New features include:

Portability and Supported Platforms

LLVM is known to work on the following platforms:

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.

Known Problems

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 LLVM bug database and submit a bug if there isn't already one.

Experimental features included with this release

The following components of this LLVM release are either untested, known to be broken or unreliable, or are in early development. These components should not be relied on, and bugs should not be filed against them, but they may be useful to some people. In particular, if you would like to work on one of these components, please contact us on the LLVMdev list.

Known problems with the X86 back-end
Known problems with the PowerPC back-end
Known problems with the ARM back-end
Known problems with the SPARC back-end
Known problems with the Alpha back-end
Known problems with the IA64 back-end
Known problems with the C back-end
Known problems with the llvm-gcc C front-end

llvm-gcc does not currently support Link-Time Optimization on most platforms "out-of-the-box". Please inquire on the llvmdev mailing list if you are interested.

The only major language feature of GCC not supported by llvm-gcc is the __builtin_apply 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).

If you run into GCC extensions which are not supported, please let us know.

Known problems with the llvm-gcc C++ front-end

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.

Known problems with the llvm-gcc Ada front-end
The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature technology and problems should be expected.
Additional Information

A wide variety of additional information is available on the LLVM web page, in particular in the documentation 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 "llvm/doc/" directory in the LLVM tree.

If you have any questions or comments about LLVM, please feel free to contact us via the mailing lists.

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Last modified: $Date: 2008/06/09 08:20:32 $