Hardware based profiling (e.g. hwpmc) is much better and produces more
useful results. Today the profiling lib archives (_p.a) serve no real
purpose other than increasing the library build time.
Both upstream and base system (in commit b762974cf4b9) Clang have been
modified to remove the special case for linking against these libraries.
Clang's -pg support and mcount() remain, so building with -pg can still
be used on code that the user builds; we just no longer provide prebuilt
libraries compiled with -pg.
Discussed on freebsd-hackers[1] / freebsd-current [2] in 2020 and
freebsd-arch [3] in 2021. A deprecation notice was added in
commit 175841285e28.
[1] https://lists.freebsd.org/pipermail/freebsd-hackers/2020-January/055551.html
[2] https://lists.freebsd.org/pipermail/freebsd-current/2020-January/075105.html
[3] https://lists.freebsd.org/archives/freebsd-arch/2021-June/000016.html
PR: 256873 [exp-run]
Reviewed by: imp, jhb, kib
Relnotes: Yes
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D30833
fe52b7f60e