* defaults.h (MODE_HAS_NANS, MODE_HAS_INFINITIES): New.
	(MODE_HAS_SIGNED_ZEROS, MODE_HAS_SIGN_DEPENDENT_ROUNDING): New.
	* flags.h (HONOR_NANS, HONOR_INFINITIES, HONOR_SIGNED_ZEROS): New.
	(HONOR_SIGN_DEPENDENT_ROUNDING): New.
	* builtins.c (expand_builtin_mathfn): Use HONOR_NANS.
	* c-common.c (truthvalue_conversion): Reduce x - y != 0 to x != y
	unless x and y could be infinite.
	(expand_unordered_cmp): New, mostly split from expand_tree_builtin.
	Check that the common type of both arguments is a real, even for
	targets without unordered comparisons.  Allow an integer argument
	to be compared against a real.
	(expand_tree_builtin): Use expand_unordered_cmp.
	* combine.c (combine_simplify_rtx): Use the new HONOR_... macros.
	* cse.c (fold_rtx): Likewise.  Fix indentation.
	* fold-const.c (fold_real_zero_addition_p): New.
	(fold): Use it, and the new HONOR_... macros.
	* ifcvt.c (noce_try_minmax): Use the new HONOR_... macros.
	* jump.c (reversed_comparison_code_parts): After searching for
	the true comparison mode, use HONOR_NANS to decide whether it
	can be safely reversed.
	(reverse_condition_maybe_unordered): Remove IEEE check.
	* simplify-rtx.c (simplify_binary_operation): Use the new macros
	to decide which simplifications are valid.  Allow the following
	simplifications for IEEE: (-a + b) to (b - a), (a + -b) to (a - b),
	and (a - -b) to (a + b).
	(simplify_relational_operation): Use HONOR_NANS.
	* doc/tm.texi: Document the MODE_HAS_... macros.

From-SVN: r50401