[m-rev.] for review: update to Boehm GC v8.0.6

[Peter Wang]

On Mon, 29 Nov 2021 17:46:20 +1100 Julien Fischer <jfischer at opturion.com> wrote:
> 
> Hi Peter,
> 
> The subject says you are updating to version 8.0.6 but the log message
> says version 8.2.0.  Which is it?

Oops, it's v8.0.6.

> 
> On Mon, 29 Nov 2021, Peter Wang wrote:
> 
> > I'd like to update Boehm GC at this time, and libatomic_ops with it.
> > I've pushed changes to our repos:
> >
> > libatomic_ops
> >    updated branch: release-7_6-mercury
> >    new tag: release-7_6-mercury-20211129
> >
> > bdwgc
> >    new branch: release-8_0-mercury
> >    new tag: release-8_0-mercury-20211129
> >
> > The following diff updates the Mercury repository. I haven't applied it.
> >
> > The bdwgc v8.0.x branch can make use gcc/clang atomic intrinsics instead
> > of libatomic_ops. Unfortunately, we would still need to keep
> > libatomic_ops around for MSVC.
> 
> Recent versions of MSVC, might provide the necessary intrinsics but I
> guess Boehm doesn't use them yet?
> 

It only uses gcc intrinsics right now.

> > We should be able to enable munmap support by default once the upgrade
> > is done.
> 
> No objection from me.  Has the upgrade been tested much?

Only tested on Linux and FreeBSD on x86-64 so far. It will be more
convenient to test with a release tarball, but I forgot that I can make
one for myself :)

Peter