re PR middle-end/48590 (Alias analysis confused by builtin-stack-save/restore)

2011-04-14  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/48590
	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Handle
	BUILT_IN_ALLOCA, BUILT_IN_STACK_SAVE and BUILT_IN_STACK_RESTORE.
	(call_may_clobber_ref_p_1): Handle BUILT_IN_ALLOCA and
	BUILT_IN_STACK_SAVE.
	* tree-ssa-dce.c (propagate_necessity): Handle
	BUILT_IN_ALLOCA, BUILT_IN_STACK_SAVE and BUILT_IN_STACK_RESTORE.

From-SVN: r172427