2010-01-20  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/42717
	* tree-ssa-dce.c (get_live_post_dom): Remove.
	(forward_edge_to_pdom): Take an arbitrary edge to copy
	degenerate PHI args from.
	(remove_dead_stmt): Use the first post-dominator even if it
	does not contain live statements as redirection destination.

	* gcc.c-torture/compile/pr42717.c: New testcase.

From-SVN: r156076