GCC 8/9 Land Fix For "-march=native" Tuning On Modern Intel CPUs
Written by Michael Larabel in GNU on 14 July 2018 at 05:48 AM EDT. 3 Comments
GNU --
The other day we reported on a GCC 8 regression where Skylake and newer CPUs with "-march=native" haven't been performance as optimally as they should be. Fortunately, that patch was quickly landed into the GCC SVN/Git code for GCC 9 as well as back-ported to GCC 8.

In the GCC 8.1 release and mainline code since April, as the previous article outlined, when using "-march=native" as part of the compiler flags with GCC the full capabilities of the CPU haven't been leveraged. This affects Intel Skylake CPUs and newer generations, including yet to be released hardware like Cannonlake and Icelake.

Fortunately, once the Intel developers spotted the situation, which coincidentally was detected with the use of the Phoronix Test Suite, the situation was quickly resolved. The fix has now been mainlined as well as backported to the current GCC 8 branch.

This means the fix for Skylake+ using "-march=native" will indeed be included as part of the upcoming GCC 8.2 release. It will certainly be interesting to run some fresh compiler benchmarks with modern Intel CPUs on this latest GCC code.
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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 20,000 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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