C++11 Load/Store seq cst for powerpc64: which style does the FreeBSD ABI specify?

[Mark Millard]

According to:

https://www.cl.cam.ac.uk/~pes20/cppppc/popl079-batty.pdf

the following two alternatives do not interoperate correctly
and so can not be mixed --and so the ABI needs to specify a
choice of which to use so that code from various compilers
and such can be mixed:

(leading-sync style:)

Load  Seq Cst: sync; ld; cmp; bc; isync
Store Seq Cst: sync; st

vs. (the trailing-sync style:)

Load  Seq Cst: ld; sync
Store Seq Cst: lwsync; st; sync

Which is the powerpc64 FreeBSD ABI based on?
Which is the 32-bit powerpc FreeBSD ABI based on?

Is there a place to see the FreeBSD ABI specification of
this for powerpc64 (and any related items)? If yes, where?
Similarly for 32-bit powerpc.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)