LLVM 1.8 Release Notes
  1. Introduction
  2. What's New?
  3. Installation Instructions
  4. Portability and Supported Platforms
  5. Known Problems
  6. Additional Information

Written by the LLVM Team


This document contains the release notes for the LLVM compiler infrastructure, release 1.8. Here we describe the status of LLVM, including any known problems and major improvements from the previous release. The most up-to-date version of this document (corresponding to LLVM CVS) can be found on the LLVM releases web site. If you are not reading this on the LLVM web pages, you should probably go there because this document may be updated after the release.

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 CVS or the main LLVM web page, this document applies to the next release, not the current one. To see the release notes for the current or previous releases, see the releases page.

What's New?

This is the nineth public release of the LLVM Compiler Infrastructure. This release incorporates a large number of enhancements and new features, including DWARF debugging support (C and C++ on Darwin/PPC), improved inline assembly support, a new nightly tester, llvm-config enhancements, many bugs fixed, and performance and compile time improvements.

New Features in LLVM 1.8
DWARF debugging support

The llvm-gcc4 C front-end now generates debugging info for C and C++. This information is propagated through the compiler and the code generator can currently produce DWARF debugging information from it. DWARF is a standard debugging format used on many platforms, but currently LLVM only includes target support for Mac OS X targets for the 1.8 release.

Inline Assembly Support

Inline assembly support is substantially improved in LLVM 1.8 over LLVM 1.7. Many unsupported features are now supported, and inline asm support in the X86 backend is far better. llvm-gcc4 now supports global register variables as well.

Loop Optimizer Improvements

The loop optimizer passes now use "Loop-Closed SSA Form", which makes it easier to update SSA form as loop transformations change the code. An immediate benefit of this is that the loop unswitching pass can now unswitch loops in more cases.

Jump Table Support for Switches

The code generator now lowers switch statements to jump tables, providing significant performance boosts for applications (e.g. interpreters) whose performance is highly correlated to switch statement performance.

Deallocation of JIT'd Machine Code

The LLVM JIT now allows clients to deallocate machine code JIT'd to its code buffer. This is important for long living applications that depend on the JIT.

Other Improvements

This release includes many other improvements, including improvements to the optimizers and code generators (improving the generated code) changes to speed up the compiler in many ways (improving algorithms and fine tuning code), and changes to reduce the code size of the compiler itself.

More specific changes include:

Significant Changes in LLVM 1.8
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 Build System
Known problems with the LLVM Core
Known problems with the C front-end

llvm-gcc3 has many significant problems that are fixed by llvm-gcc4. Two major ones include:

llvm-gcc4 is far more stable and produces better code than llvm-gcc3, but does not currently support Link-Time-Optimization or C++ Exception Handling, which llvm-gcc3 does.


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).

Known problems with the C++ front-end

For this release, the C++ front-end is considered to be fully tested and works for a number of non-trivial programs, including LLVM itself.

Known problems with the C back-end
Known problems with the X86 back-end
Known problems with the PowerPC back-end
Known problems with the Alpha back-end
Known problems with the IA64 back-end
Known problems with the SPARC back-end
Known problems with the ARM back-end
Additional Information

A wide variety of additional information is available on the LLVM web page, including documentation and publications describing algorithms and components implemented in LLVM. The web page also contains versions of the API documentation which is up-to-date with the CVS 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: 2006/08/09 16:32:30 $