2009-04-06  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/28868
	* tree-ssa-pre.c (inserted_phi_names): New bitmap to keep track
	of which PHI results we inserted.
	(insert_into_preds_of_block): Record inserted PHIs.
	(eliminate): Eliminate redundant PHI nodes.
	(init_pre): Init inserted_phi_names.

	* gcc.dg/tree-ssa/ssa-fre-21.c: New testcase.
	* gcc.dg/tree-ssa/ssa-sccvn-1.c: Adjust.
	* gcc.dg/tree-ssa/ssa-sccvn-2.c: Likewise.
	* gcc.dg/tree-ssa/ssa-sccvn-4.c: Likewise.

From-SVN: r145607