* tree.h (enum tree_index): Add TI_VA_LIST_GPR_COUNTER_FIELD
	and TI_VA_LIST_FPR_COUNTER_FIELD.
	(va_list_gpr_counter_field, va_list_fpr_counter_field): Define.
	* tree-pass.h (pass_stdarg): Add.
	* tree-optimize.c (init_tree_optimization_passes): Add pass_stdarg.
	* tree-stdarg.c: New file.
	* Makefile.in (OBJS-common): Add tree-stdarg.o.
	(tree-stdarg.o): Add dependencies.
	* function.h (struct function): Add va_list_gpr_size and
	va_list_fpr_size fields.
	* function.c (allocate_struct_function): Initialize them.

	* config/i386/i386.c (ix86_build_builtin_va_list): Initialize
	va_list_{g,f}pr_counter_field.
	(ix86_setup_incoming_varargs): Don't do anything if reg_save
	area will not be used.  Only save registers that tree-stdarg.c
	detected they need saving.
	(ix86_va_start): Don't set up fields that won't be used.

	* config/rs6000/rs6000.c (rs6000_build_builtin_va_list): Initialize
	va_list_{g,f}pr_counter_field.
	(setup_incoming_varargs): Don't do anything if reg_save
	area will not be used.  Only save registers that tree-stdarg.c
	detected they need saving.
	(rs6000_va_start): Don't set up fields that won't be used.

	* gcc.c-torture/execute/stdarg-1.c: New test.
	* gcc.c-torture/execute/stdarg-2.c: New test.
	* gcc.c-torture/execute/stdarg-3.c: New test.
	* gcc.dg/tree-ssa/stdarg-1.c: New test.
	* gcc.dg/tree-ssa/stdarg-2.c: New test.
	* gcc.dg/tree-ssa/stdarg-3.c: New test.
	* gcc.dg/tree-ssa/stdarg-4.c: New test.
	* gcc.dg/tree-ssa/stdarg-5.c: New test.

From-SVN: r88279