using CPUTYPE?= with poudriere jails

[tech-lists]

Hi,

I've been trying to use CPUTYPE?= with certain poudriere jails.
My reasoning being that it should be better (more efficient?) making a
targeted binary especially when the target is a cpu that doesn't have a lot of
processing power comparitively.

I'm not at all certain if my reasoning is correct though, so can anyone
advise? Or is it not worth it for the performance gained?  (in which case why
have the option at all?)

Anyway, I was surprised to find that if CPUTYPE?=btver1 was used in a
poudriere make.conf for a freebsd 12.1 jail on a 
sandybridge host (Intel(R) Xeon(R) CPU E5-2690 0 @ 2.90GHz) (also running
12.1), that some ports would not compile, like python36 and lzo2.

If I run a poudriere jail configured the same way on the same freebsd version
but on a system which is Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz and is a
haswell host, the same programs compile without error.

Is this expected and, if so, why?

thanks,
-- 
J.
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