Re: NetBSD 9.2 Alpha: error in handling of IEEE 754 binary 32-bit subnormals

[John Klos <john%ziaspace.com@localhost>]

> of creating a virtual machine for NetBSD 9.2 (really, 9.99.88, but
> packages are still pulled from the 9.2 repository, which is currently
> identical to the 9.0 repository).

They're all symlinked and therefore the same, yes.

> I now have an apparently stable running NetBSD on Alpha, with a few
> irregularities: emacs seems to hang on startup, and the PostgreSQL
> package collection is incomplete.  MySQL is installed: Ver 15.1
> Distrib 10.3.31-MariaDB.

I'll check out emacs. The lack of complete PostgreSQL is because they 
preferred to unsupport Alpha instead of just switching it to using common 
code. That can be fixed, if you have a use for PostgreSQL.

> Another anomaly is shown by the ufl32.c program: it reports the status
> of the IEEE 754 floating-point underflow and inexact flags, and
> whether the result is subnormal or not.  The SPARC64 flag settings are
> as expected, and the AMD64 flags differ because of the different
> rounding behavior of those two architectures. There is a discussion
> and explanation here in the section that begins on page 10:
>
> 	http://www.math.utah.edu/~beebe/ufl/pages-13-21.pdf
>
> Because both Debian and NetBSD VMs are running on QEMU (6.0.0 and
> 6.1.0, respectively), the Alpha architecture is almost 30 years old,
> and QEMU is generally a solid and reliable emulation of numerous
> architectures, the different flag behavior for subnormals is
> unexpected, and it seems that NetBSD is wrong here too.

Real hardware gives MINNORMAL = 0x1.0p-126, but is otherwise the same.
Real hardware also gives the same results as Linux-Alpha for
netbsd-alpha-bug001.c

Everything else I've looked at so far shows that qemu matches hardware,
but it'll be helpful to note where an issue is because of NetBSD versus
where it's a qemu issue.

I believe there was a similar set of issues with m68k, no?

John