Clang Compiling Against GCC On Ubuntu ARM Linux
Written by Michael Larabel in Compiler on 11 June 2012 at 09:54 AM EDT. 9 Comments
Here's an update on the LLVM/Clang vs. GCC compiler benchmarking on ARM hardware under Linux.

Last month on Phoronix I shared a few basic benchmarks of GCC vs. LLVM/Clang Compilers On ARMv7 Linux. GCC 4.6.3 on Ubuntu 12.04 was doing much better than LLVM/Clang 3.0 from the Precise repository. As was realized after the fact, LLVM/Clang on ARM Linux isn't auto-detecting the processor. GCC on ARM Linux, meanwhile, was able to recognize the dual-core ARM Cortex-A9. Therefore GCC does much better "out of the box" in a standard configuration like most Linux end-users would build their software.

Thanks to the public pressure, Apple/LLVM looks like they're now working for ARM target auto-detection so that we get functionality similar to GCC on ARM Linux or x86: Request for Help: Teach ARM target to auto-detect cpu / subtarget features. This is a current deficiency of LLVM on ARM.

For those interested, below are some updated ARM compiler benchmarks under Linux. In this article is a development snapshot of Ubuntu 12.10 while testing GCC 4.7.0 and LLVM/Clang 3.0. The benchmarking was still being done from a PandaBoard ES with Texas Instruments OMAP4460 dual-core ARM Cortex-A9 development board. Via the CFLAGS/CXXFLAGS, -march=armv7-a was passed to each compiler.

GCC 4.7 has a small advantage over LLVM/Clang 3.0 in the TSCP chess computational benchmark.

7-Zip compression on the Texas Instruments' PandaBoard ES is now faster with the LLVM/Clang compiler than the latest GCC release.

GCC is still superior for the multi-core C-Ray ray-tracing benchmark.

Additional information is available via OpenBenchmarking.org. You can also compare your x86/ARM performance with these benchmarks to the ARMv7 results by running phoronix-test-suite benchmark 1206060-SU-LLVMCLANG78. More tests are forthcoming.


Recent work on the ARM Linux cluster from the Phoronix office.

Also check out the cheap 12-core 13-Watt Ubuntu Linux ARM cluster and Ubuntu 12.10 Sets To Make ARM Even Stronger. On the x86 side there is the recent 11-way code compiler comparison on Intel's Ivy Bridge platform.
About The Author
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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