tree-ssa-structalias.c (find_func_aliases): For memset use a constraint from NULL if we memset to zero.

2009-06-20  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-structalias.c (find_func_aliases): For memset use
	a constraint from NULL if we memset to zero.
	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Add builtins
	we explicitly handle that do not read from memory.
	(call_may_clobber_ref_p_1): Properly handle builtins that may
	set errno.

From-SVN: r148747