It looks like Emacs can use this for some NaN processing.
Emacs uses it only on double NaNs so it should be safe.
* MODULES.html.sh (func_all_modules): Add ieee754-h.
* config/srclist.txt: Mention ieee754.h in a comment.
* doc/glibc-headers/ieee754.texi (ieee754.h):
Gnulib now has a substitute that should work
except for long double and for non-IEEE platforms.
* lib/ieee754.in.h, m4/ieee754-h.m4, modules/ieee754-h:
* modules/ieee754-h-tests, tests/test-ieee754-h.c: New files.