Fix linux kernel -foptimize-sibling-calls miscompilation

Fix linux kernel -foptimize-sibling-calls miscompilation
	* config/ia64/ia64.c (ia64_expand_epilogue): Emit alloc if sibcall_p.
	(first_instruction): New static variable.
	(rtx_needs_barrier): Return 1 for alloc.
	(init_insn_group_barriers): Set first_instruction.
	(rws_sum): Delete duplicate definition.
	(group_barrier_needed_p): Return 0 when first_instruction true.
	(safe_group_barrier_needed_p): Save and restore first_instruction
	around group_barrier_needed_p call.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@41347 138bc75d-0d04-0410-961f-82ee72b054a4