PR fortran/48979

	* simplify.c (gfc_simplify_atan): Use mpfr_zero_p to check for zeros.
	(gfc_simplify_log): Likewise.
	(gfc_simplify_scale): Likewise.
	(gfc_simplify_exponent): Handle infinities and NaNs.
	(gfc_simplify_fraction): Handle infinities.
	(gfc_simplify_rrspacing): Handle signed zeros and NaNs.
	(gfc_simplify_set_exponent): Handle infinities and NaNs.
	(gfc_simplify_spacing): Handle zeros, infinities and NaNs.

	* gfortran.dg/ieee/intrinsics_1.f90: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@216120 138bc75d-0d04-0410-961f-82ee72b054a4