* simplify-rtx.c (associative_constant_p): New function to test
	whether an RTX expression is an immediate constant.
	(simplify_associative_operation): New function to perform some
	reassociation optimizations of associative binary expressions.
	(simplify_binary_operation): Use simplify_associative_operation
	to simplify PLUS, MULT, AND, IOR, XOR, SMIN, SMAX, UMIN and UMAX.
	Floating point expressions are only reassociated when unsafe
	math optimizations are permitted.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@70521 138bc75d-0d04-0410-961f-82ee72b054a4