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

LLVM May Expand Its Use Of The Loop Vectorizer

Compiler

Published on 06 June 2013 01:05 AM EDT
Written by Michael Larabel in Compiler
8 Comments

LLVM's Loop Vectorizer, which is able to automatically vectorize code loops for performance benefits in many scenarios, may find its use expanded for other optimization levels in future LLVM releases.

LLVM's automatic loop vectorizer was merged for the LLVM 3.2 release and benchmarking the loop vectorizer showed it to provide performance benefits for many scenarios. In the LLVM 3.2 release it wasn't enabled by default, but for LLVM 3.3 it's now enabled when using the -O3 optimization level.

Besides enabling it default for this greatest optimization level, LLVM 3.3 also provided improvements to the loop vectorizer. The LLVM loop vectorizer is now in good standing and so it might be enabled too by default for -O2 and -Os.

There's still some differing views on why the vectorizer should be turned on for -O2, which is the mid optimization level before -O3, but for at least -Os it should be turned on. The -Os level is when optimizing generated binaries for size. The loop vectorizer has the potential of increasing the binary size for some loops, but LLVM is able to weight that information and decide when to vectorize or not.

Apple LLVM developers have now been discussing on the LLVM mailing list about expanding the loop vectorizer's usage by default. The performance wins provided by this vectorizer seem to be worth it to many people even at the potential cost of a slightly longer compile time or the chance that the resulting binary size is slightly larger. This is a change that won't come for LLVM 3.3 but will be for LLVM 3.4 or later; we'll see what happens and post the decision on Phoronix.

LLVM 3.3 also has the interesting SLP vectorizer to optimize straight-line code, but this current discussion is only talking about the loop vectorizer.

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 Articles & Reviews
  1. NVIDIA's $1000+ GeForce GTX TITAN X Delivers Maximum Linux Performance
  2. OS X 10.10 vs. Ubuntu 15.04 vs. Fedora 21 Tests: Linux Sweeps The Board
  3. The New Place Where Linux Code Is Constantly Being Benchmarked
  4. 18-GPU NVIDIA/AMD Linux Comparison Of BioShock: Infinite
  5. Phoronix Test Suite 5.6 Adds New Phoromatic Enterprise Benchmarking Features
  6. OpenGL Threaded Optimizations Responsible For NVIDIA's Faster Performance?
Latest Linux News
  1. Improved OpenCL Support For Blender's Cycles Renderer
  2. Mesa 10.5.2 Packs In A Handful Of Fixes
  3. More Fedora/Ubuntu Linux vs. OS X OpenGL Benchmarks
  4. Intel Adds Mesa IR To NIR Translator & Makes Other NIR Improvements
  5. HAMMER2 Gets A Man Page
  6. Kodi 14.2 Released To End Out The "XBMC" 14.x Series
  7. Debian 8.0 Jessie RC2 Installer Released
  8. Shadow Warrior Is Being Released For Linux Next Week
  9. Intel Pushes A Bunch Of Broadwell Code Into Coreboot
  10. Open-Source Driver Fans Will Love NVIDIA's New OpenGL Demo
Most Viewed News This Week
  1. Introducing The Library Operating System For Linux
  2. AMD Is Hiring Two More Open-Source Linux GPU Driver Developers
  3. Allwinner Continues Jerking Around The Open-Source Community
  4. New SecureBoot Concerns Arise With Windows 10
  5. Systemd Change Allows For Stateless Systems With Tmpfs
  6. GNOME Shell & Mutter 3.16.0 Released
  7. GNU Nano 2.4.0 Brings Complete Undo System, Linter Support & More
  8. Red Hat Is Rolling Out A VirtIO DRM/KMS GPU Driver