Excellent!  From a bit of searching, it looks as though this assembler
syntax works on icc as well, which is very good news.

Thanks for finding fesetprec as well.  It's a shame this isn't standard
C.  Oh well;  maybe for C201X.  I think I'd prefer to stick with the
inline assembly, since it seems that there's very little to do to make
this just work.

Next problem:  when compiling with suncc, how do I detect (in the
configure script)

(1) that I'm using suncc, and
(2) whether the hardware is x86 or not (preferably excluding the case of
x86-64).

For gcc, configure.in is using:

if test -n "`$CC -dM -E - </dev/null | grep i386`"

to detect whether we're on x86.  I guess it's too much to hope for that
this works for suncc as well.