src/lib/libc/amd64/string/memmove.S, branch releng/12.4

amd64: Stop using REP MOVSB for backward memmove()s.

2022-06-30T01:14:12Z

Enhanced REP MOVSB feature of CPUs starting from Ivy Bridge makes REP MOVSB the fastest way to copy memory in most of cases. However Intel Optimization Reference Manual says: "setting the DF to force REP MOVSB to copy bytes from high towards low addresses will expe- rience significant performance degradation". Measurements on Intel Cascade Lake and Alder Lake, same as on AMD Zen3 show that it can drop throughput to as low as 2.5-3.5GB/s, comparing to ~10-30GB/s of REP MOVSQ or hand-rolled loop, used for non-ERMS CPUs. This patch keeps ERMS use for forward ordered memory copies, but removes it for backward overlapped moves where it does not work. This is just a cosmetic sync with kernel, since libc does not use ERMS at this time. Reviewed by: mjg MFC after: 2 weeks (cherry picked from commit f22068d91bf53696ee13a69685e809d35776ec3f)

amd64: add missing ALIGN_TEXT to loops in memset and memmove

2021-06-26T15:52:36Z

(cherry picked from commit 164c3b81848bc81dc200b12370999474225447a3)

MFC r341272,r341273,r341351

2018-12-19T21:25:43Z

amd64: tidy up copying backwards in memmove amd64: remove stale attribution for memmove work amd64: handle small memmove buffers with overlapping stores

MFC r341364

2018-12-19T21:03:17Z

amd64: align target memmove buffer to 16 bytes before using rep movs

amd64: import updated kernel memmove to libc

2018-10-13T21:15:47Z

bcopy is left alone as it is expected to be converted to a C func. Due to header mess ALIGN_TEXT is temporarily defined explicitly in memmove.S Reviewed by: kib Approved by: re (gjb) Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D17538

Remove duplicate .note.GNU-stack section declaration. bcopy already

2011-02-04T21:04:00Z

made the neccessary provisions. Reported by: arundel

Add section .note.GNU-stack for assembly files used by 386 and amd64.

2011-01-07T16:08:40Z

Add machine-specific, optimized implementations of bcopy, bzero, memcpy,

2005-04-07T03:56:03Z

memmove, and memset. PR: 73111 Submitted by: Ville-Pertti Keinonen (taken from NetBSD) MFC after: 3 weeks