Intel Further Speeds Up strnlen() In The GNU C Library For Recent Intel/AMD CPUs
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Matthew Sterrett of Intel unified Glibc's strnlen EVEX and EVEX512 implementations. In turn this unified, optimized strnlen handling for x86_64 Intel/AMD CPUs with EVEX support is showing some nice improvements over the prior code.
Sterrett wrote in the commit unifying the strnlen EVEX implementations:
x86: Unifies 'strnlen-evex' and 'strnlen-evex512' implementations.
This commit uses a common implementation 'strnlen-evex-base.S' for both 'strnlen-evex' and 'strnlen-evex512'
This patch serves both to reduce the number of implementations, and it also does some small optimizations that benefit strnlen-evex and strnlen-evex512.
All tests pass on x86.
Benchmarks were taken on [an Intel Core i9 7900X Skylake X CPU].
Geometric mean for strnlen-evex over all benchmarks (N=10) was (new/old) 0.881
Geometric mean for strnlen-evex512 over all benchmarks (N=10) was (new/old) 0.953
That improved code is merged in Glibc Git for the Glibc 2.41 release coming out as stable in February.
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