PR rtl-optimization/15422
	* reg-stack.c (starting_stack_p): New static global.
	(straighten_stack): Delete prototype. Change to update the stack
	before the current insn.
	(subst_stack_regs): Update call to straighten stack.
	(emit_swap_insn): Delete prototype.  For the first insn in a
	basic block, update stack_in instead of emitting a real swap.
	(change_stack): When changing the stack before the first insn
	in a basic block, update stack_in instead of emitting real code.
	(compensate_edges): Clear starting_stack_p during compensation.
	(convert_regs_1): Keep track of starting_stack_p whilst processing
	a basic block.

From-SVN: r100370