Intel Haswell Scheduler Updated In LLVM

Written by Michael Larabel in LLVM on 28 August 2017 at 06:19 AM EDT. 11 Comments
Last month in LLVM there was new Sandy Bridge scheduler information to improve the instruction scheduling and other hardware detail changes so LLVM can generate more efficient code for those older CPUs. At that time we learned Intel developers were also planning improvements too for LLVM with newer Haswell / Broadwell / Skylake / Skylake-X CPUs. Improvements have now landed for Haswell.

As of this morning in LLVM Git is updated scheduling information for Haswell CPUs. This updates the Haswell architecture target with new instruction scheduling data, including latency, number of micro-ops, etc. This is likely to result in some code performance fluctuations.

The updated Haswell scheduler can be found via LLVM in their 6.0 development code. I'll be working on some fresh LLVM/Clang Haswell/SandyBridge benchmarks shortly at Phoronix.
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Michael Larabel is the principal author of 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 automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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