* emit-rtl.c (dconstm2, dconsthalf): New real constants.
	(init_emit_once): Initialize dconstm2 and dconsthalf here.
	* real.h (dconstm2, dconsthalf): Add prototypes here.
	* real.c (real_sqrt): Use dconsthalf rather than local copy.
	* builtins.c (fold_builtin): When optimizing sqrt(exp(x)) as
	exp(x/2.0) remember to fold the division if possible.
	Fold sin(0.0) as 0.0, cos(0.0) as 1.0, pow(x,1.0) as x,
	pow(x,-1.0) as 1.0/x, pow(x,2.0) as x*x, pow(x,-2.0) as
	1.0/(x*x) and pow(x,0.5) as sqrt(x).

	* gcc.dg/builtins-3.c: Add new tests for sin and cos.
	* gcc.dg/builtins-7.c: New test case.
	* gcc.dg/builtins-8.c: New test case.

From-SVN: r65088