1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

Looping Through LLVM's New Loop Vectorizer

Compiler

Published on 08 December 2012 09:21 AM EST
Written by Michael Larabel in Compiler
Comment On This Article

Premiering with LLVM 3.2, which will debut later this month, is an automatic loop vectorizer. I've already delivered benchmarks of LLVM's new automatic loop vectorizer, but here's more details on this new LLVM compiler feature.

The LLVM Loop Vectorizer is the second vectorizer for the compiler infrastructure after its Basic Block Vectorizer for dealing with straight-line code. The Loop Vectorizer is meant to widen instructions in an original loop for operating on multiple consecutive loop iterations. As mentioned in the earlier Phoronix articles on the subject, this feature isn't enabled by default with the forthcoming LLVM 3.2 but can be flipped on via the -mllvm -vectorize-loops compiler switches.

On the LLVM Blog is a new posting from yesterday that goes into detail about LLVM's Loop Vectorizer. The posting also mentions that for the LLVM 3.3 release in 2013 they will be aiming to have this vectorizer enabled by default. The blog post covers a few examples of how LLVM can now vectorize different complex loops.

The post also shares that there's more work going forward:

The Loop Vectorizer is a target independent IR-level optimization that depends on target-specific information from the different backends. It needs to select the optimal vector width and to decide if vectorization is worthwhile. Users can force a certain vector width using the command line flag "-mllvm -force-vector-width=X", where X is the number of vector elements. At the moment, only the X86 backend provides detailed cost information, while other targets use a less accurate method.

The work on the Loop Vectorizer is not complete and the vectorizer has a long way to go. We plan to add additional vectorization features such as automatic alignment of buffers, vectorization of function calls and support for user pragmas. We also plan to improve the quality of the generated code.
Read about this new LLVM 3.2 feature at blog.llvm.org. Also to be found in this month's LLVM/Clang/DragonEgg 3.2 release is better PowerPC compiler support, Polly improvements, and much more.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. CompuLab Intense-PC2: An Excellent, Fanless, Mini PC Powered By Intel's i7 Haswell
  2. From The Atom 330 To Haswell ULT: Intel Linux Performance Benchmarks
  3. AMD Radeon R9 285 Tonga Performance On Linux
  4. Apotop Wi-Copy
Latest Linux Articles
  1. AMD Moves Forward With Unified Linux Driver Strategy, New Kernel Driver
  2. MSI: Update Your BIOS From The Linux Desktop
  3. NVIDIA vs. AMD 2D Linux Drivers: Catalyst Is Getting Quite Good At 2D
  4. 15-Way GPU Comparison With Mesa 10.3 + Linux 3.17
Latest Linux News
  1. NVIDIA's NVPTX Support For GCC Is Close To Being Merged
  2. KDE's KWin On Wayland Begins Using Libinput
  3. Khronos Releases OpenVX 1.0 Specification
  4. Linux Kernel Working Towards GNU11/C11 Compatibility
  5. Ubuntu 15.04 Is Codenamed After A Monkey: Vivid Vervet
  6. Following GCC, Clang Looks To Default To C11
  7. Users/Developers Threatening Fork Of Debian GNU/Linux
  8. Linux 3.18-rc1 Released One Week Early With Many Changes
  9. The VC4 Gallium3D Driver Is Still Moving Along For The Raspberry Pi
  10. Direct3D 9 Support Might Land Within Mainline Mesa 3D Drivers
Latest Forum Discussions
  1. Users/Developers Threatening Fork Of Debian GNU/Linux
  2. HOPE: The Ease Of Python With The Speed Of C++
  3. NVIDIA Presents Its Driver Plans To Support Mir/Wayland & KMS On Linux
  4. AMD Is Restructuring Again, Losing 7% Of Employees
  5. Bye bye BSD, Hello Linux: A Sys Admin's Story
  6. Open-Source AMD Fusion E-350 Support Takes A Dive
  7. Upgrade to Kaveri, very slow VDPAU performance
  8. ChromeOS Drops Support For EXT2/EXT3/EXT4 File-Systems