* optabs.h (enum optab_index): Add new OTI_significand.
	(significand_optab): Define corresponding macro.
	* optabs.c (init_optabs): Initialize significand_optab.
	* genopinit.c (optabs): Implement significand_optab using
	significand?f2 patterns.
	* builtins.c (expand_builtin_mathfn): Handle
	BUILT_IN_SIGNIFICAND{,F,L}.
	(expand_builtin): Expand BUILT_IN_SIGNIFICAND{,F,L} using
	expand_builtin_mathfn if flag_unsafe_math_optimizations is set.

	* config/i386/i386.md (significandxf2, significand<mode>2): New
	expanders to implement significandf, significand and significandl
	built-ins as inline x87 intrinsics.

testsuite/ChangeLog:

	* gcc.dg/builtins-34.c: Add significand cases.

	PR testsuite/40491
	* testsuite/gcc.dg/20080522-1.c: Remove testcase for real.
	* testsuite/gcc.dg/20080528-1.c: Ditto.

From-SVN: r148705