PR target/61300
	* doc/tm.texi.in (INCOMING_REG_PARM_STACK_SPACE): Document.
	* doc/tm.texi: Regenerate.
	* function.c (INCOMING_REG_PARM_STACK_SPACE): Provide default.
	Use throughout in place of REG_PARM_STACK_SPACE.
	* config/rs6000/rs6000.c (rs6000_reg_parm_stack_space): Add
	"incoming" param.  Pass to rs6000_function_parms_need_stack.
	(rs6000_function_parms_need_stack): Add "incoming" param, ignore
	prototype_p when incoming.  Use function decl when incoming
	to handle K&R style functions.
	* config/rs6000/rs6000.h (REG_PARM_STACK_SPACE): Adjust.
	(INCOMING_REG_PARM_STACK_SPACE): Define.

From-SVN: r211296