2008-03-14  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/34172
	* tree-flow.h (refs_may_alias_p): Declare.
	(get_single_def_stmt): Likewise.
	(get_single_def_stmt_from_phi): Likewise.
	(get_single_def_stmt_with_phi): Likewise.
	* tree-dfa.c (refs_may_alias_p): New function.
	(get_single_def_stmt): Likewise.
	(get_single_def_stmt_from_phi): Likewise.
	(get_single_def_stmt_with_phi): Likewise.
	* tree-ssa-sccvn.c (get_def_ref_stmt_vuses): New function.
	(vn_reference_lookup_1): New helper function.
	(vn_reference_lookup): Walk the virtual use-def chain to
	continue searching for a match if the def does not alias the
	reference we are looking for.

	* gcc.dg/tree-ssa/ssa-fre-11.c: New testcase.
	* gcc.dg/tree-ssa/ssa-fre-12.c: Likewise.
	* gcc.dg/tree-ssa/ssa-fre-13.c: Likewise.
	* gcc.dg/tree-ssa/ssa-fre-14.c: Likewise.
	* gcc.dg/tree-ssa/ssa-fre-15.c: Likewise.
	* gcc.dg/tree-ssa/20031106-4.c: Remove XFAIL.

From-SVN: r133222