fenv.h support for alpha?

[Dave Huang <khym%azeotrope.org@localhost>]

I was trying to build ffmpeg3 from pkgsrc on NetBSD/alpha, and got this error:

In file included from libavfilter/vf_drawtext.c:40:0:
/usr/include/fenv.h:31:2: error: #error "fenv.h is currently not supported for this architecture"
 #error "fenv.h is currently not supported for this architecture"
  ^

Back in 2014, Martin Husemann mentioned that he was planning to look at 
adding support: 
http://mail-index.netbsd.org/port-alpha/2014/03/07/msg000695.html

There's also this PR 49997 about the lack of fenv.h support on various 
architectures: http://gnats.netbsd.org/49997

Has there been any progress on this since then? What's involved in 
adding support? I seem to recall hearing that the Alpha doesn't fully 
implement the IEEE FP standard, and that it needs some software 
assistance--is the problem that we need to write that software?
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