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GCC 4.8.0 vs. LLVM Clang 3.3 Compiler Performance Three-Way

Michael Larabel

Published on 25 May 2013
Written by Michael Larabel
Page 4 of 4 - 17 Comments

Smallpt is just another case where LLVM/Clang performs slowly due to its lack of OpenMP support.

The FFmpeg performance hasn't really changed much with the new LLVM/Clang release, but this video encoder relies a lot on hand-tuned Assembly.

The PostgreSQL server performance also hasn't evolved much with LLVM/Clang 3.3.

For the Intel systems with the Apache web-server the LLVM/Clang 3.3 performance appears slightly faster.

Overall, LLVM/Clang 3.3 appears to be largely competitive with GCC 4.8.0 except in select cases like the missing OpenMP support. Depending upon the hardware, there are some nice performance improvements with LLVM 3.3 over its predecessor. Aside from performance changes, LLVM 3.3 is nice in that the Clang compiler is C++11 feature-complete, there is now the ARM AArch64 64-bit support, IBM SystemZ support, there's the SLP Vectorizer and improvements to the Loop Vectorizer, the AMD R600 GPU LLVM back-end has been merged, and much more. Look for the LLVM/Clang 3.3 final release in early June.

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 .
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