Intel has `rep movs` which is recommended for general use, you can beat it for s... | Hacker News

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jeffbee on June 25, 2020 | parent | context | favorite | on: C performance mystery: delete unused string consta...

Intel has `rep movs` which is recommended for general use, you can beat it for sizes < 128B using a specialized loop. A very good memcpy for general purposes would just branch over the size to either a specialized small copy or `rep movs` for larger sizes.

The GCC version is just bananas. https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=sysde...

Compare the newer ERMS implementation: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/x86...

andrewf on June 25, 2020 | [–]

What's weird is that if you git blame a bit, a lot of the elaborate stuff was contributed by Intel.

jeffbee on June 25, 2020 | | [–]

Intel is at least as guilty of chasing misleading benchmarks as anyone else in the history of our field.

saagarjha on June 25, 2020 | [–]

No AVX2-optimized version? I'm disappointed…

Edit: it's rolled into the erms version.

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