PR rtl-optimization/576

	PR rtl-optimization/576
	* real.c (real_arithmetic): Change return type from void to bool
	to return an indication that the result may be inexact.
	* real.h (real_arithmeric): Update prototype.
	* fold-const.c (const_binop):  Don't constant fold floating
	point expressions when the user specifies -frounding-math and
	the result may depend upon the run-time rounding mode.
	(fold_convert_const_real_from_real): Clean-up.
	(fold_initializer): Ignore flag_rounding_math for initializers.
	* simplify-rtx.c (simplify_binary_operation): Likewise, don't
	constant fold FP operations with flag_rounding_math if the
	result may depend upon the run-time rounding mode.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@94020 138bc75d-0d04-0410-961f-82ee72b054a4