optabs.c (expand_float): Convert unsigned integer as signed only if it provides sufficient accuracy...

gcc/
	* optabs.c (expand_float): Convert unsigned integer as signed only
	if it provides sufficient accuracy; add mode argument to real_2expN.
	(expand_fix): Fix comment typos; extend binary float into mode
	wider than destination for converion to unsigned integer; add mode
	argument to real_2expN.
	* real.c (real_2expN): Add mode argument to special-case decimal
	float values.
	* real.h (real_2expN): Ditto.
	* fixed-value.c (check_real_for_fixed_mode): Add mode argument to
	real_2expN.
	(fixed_from_string): Ditto.
	(fixed_to_decimal): Ditto.
	(fixed_convert_from_real): Ditto.
	(real_convert_from_fixed): Ditto.
	* config/rs6000/rs6000.md (FP): Include DD and TD modes.
	* config/rs6000/dfp.md (extendddtd2, adddd3, addtd3, subdd3, subtd3,
	muldd3, multd3, divdd3, divtd3, cmpdd_internal1, cmptd_internal1,
	floatditd2, ftruncdd2, fixdddi2, ftrunctd2, fixddi2): New.

gcc/testsuite/
	* gcc.target/powerpc/dfp-dd.c: New test.
	* gcc.target/powerpc/dfp-td.c: New test.

From-SVN: r128156