* optabs.h (enum optab_index): Add new OTI_log1p.
	(log1p_optab): Define corresponding macro.
	* optabs.c (init_optabs): Initialize log1p_optab.
	* genopinit.c (optabs): Implement log1p_optab using log1p?f2
	patterns.
	* builtins.c (expand_builtin_mathfn): Handle BUILT_IN_LOG1P{,F,L}
	using log1p_optab.
	(expand_builtin): Expand BUILT_IN_LOG1P{,F,L} using
	expand_builtin_mathfn if flag_unsafe_math_optimizations is set.

	* reg-stack.c (subst_stack_regs_pat): Handle UNSPEC_FYL2XP1.

	* config/i386/i386.c (ix86_emit_i387_log1p): New function.
	* config/i386/i386-protos.h (ix86_emit_i387_log1p):
	Prototype here.
	* config/i386/i386.md (UNSPEC_FYL2XP1): New unspec to represent
	x87's fyl2xp1 instruction.
	(*fyl2x_xf3): Rename insn definition to fyl2x_xf3.
	(fyl2xp1_xf3): New pattern to implement fyl2xp1 x87 instruction.
	(log1psf2, log1pdf2, log1pxf2): New expanders to implement log1pf,
	log1p  and log1pl built-ins as inline x87 intrinsics.

	* testsuite/gcc.dg/builtins-33.c:  Also check log1p*.

From-SVN: r81606