LLVM 1.7 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 1.7. 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 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 eighth public release of the LLVM Compiler Infrastructure. This release incorporates a large number of enhancements and new features, including vector support (Intel SSE and Altivec), a new GCC4.0-based C/C++ front-end, Objective C/C++ support, inline assembly support, and many other big features.

New Features in LLVM 1.7
GCC4.0-based llvm-gcc front-end

LLVM 1.7 includes a brand new llvm-gcc, based on GCC 4.0.1. This version of llvm-gcc solves many serious long-standing problems with llvm-gcc, including all of those blocked by the llvm-gcc 4 meta bug. In addition, llvm-gcc4 implements support for many new features, including GCC inline assembly, generic vector support, SSE and Altivec intrinsics, and several new GCC attributes. Finally, llvm-gcc4 is significantly faster than llvm-gcc3, respects -O options, its -c/-S options correspond to GCC's (they emit native code), supports Objective C/C++, and it has debugging support well underway.

If you can use it, llvm-gcc4 offers significant new functionality, and we hope that it will replace llvm-gcc3 completely in a future release. Unfortunately, it does not currently support C++ exception handling at all, and it only works on Apple Mac OS/X machines with X86 or PowerPC processors.

Inline Assembly Support

The LLVM IR and llvm-gcc4 front-end now fully support arbitrary GCC inline assembly. The LLVM X86 and PowerPC code generators have initial support for it, being able to compile basic statements, but are missing some features. Please report any inline asm statements that crash the compiler or that are miscompiled as bugs.

New SPARC backend

LLVM 1.7 includes a new, fully functional, SPARC backend built in the target-independent code generator. This SPARC backend includes support for SPARC V8 and SPARC V9 subtargets (controlling whether V9 features can be used), and targets the 32-bit SPARC ABI.

The LLVM 1.7 release is the last release that will include the LLVM "SparcV9" backend, which was the very first LLVM native code generator. It will be removed in LLVM 1.8, being replaced with the new SPARC backend.

Generic Vector Support

LLVM now includes significantly extended support for SIMD vectors in its core instruction set. It now includes three new instructions for manipulating vectors: extractelement, insertelement, and shufflevector. Further, many bugs in vector handling have been fixed, and vectors are now supported by the target-independent code generator. For example, if a vector operation is not supported by a particular target, it will be correctly broken down and executed as scalar operations.

Because llvm-gcc3 does not support GCC generic vectors or vector intrinsics, llvm-gcc4 must be used.

Intel SSE and PowerPC Altivec support

The LLVM X86 backend now supports Intel SSE 1, 2, and 3, and now uses scalar SSE operations to implement scalar floating point math when the target supports SSE1 (for floats) or SSE2 (for doubles). Vector SSE instructions are generated by llvm-gcc4 when the generic vector mechanism or specific SSE intrinsics are used.

The LLVM PowerPC backend now supports the Altivec instruction set, including both GCC -maltivec and -faltivec modes. Altivec instructions are generated by llvm-gcc4 when the generic vector mechanism or specific Altivec intrinsics are used.

Optimizer Improvements
Code Generator Improvements
Other New Features
Significant Changes in LLVM 1.7
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. See those blocked on the llvm-gcc4 meta bug. Two major ones include:


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 SparcV9 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: 2006/04/20 06:10:32 $