PR middle-end/20219

	* fold-const.c (fold binary) <RDIV_EXPR>: Optimize 
	sin(x)/tan(x) as cos(x) and tan(x)/sin(x) as 1.0/cos(x)
	when flag_unsafe_math_optimizations is set and
	we don't care about NaNs or Infinities.

	Move x/expN(y) and x/pow(y,z) transformation into common
	flag_unsafe_math_optimizations section.

testsuite/

	* gcc.dg/builtins-20.c: Add checks for sin(x)/tan(x) and
	tan(x)/sin(x) transformations.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@107597 138bc75d-0d04-0410-961f-82ee72b054a4