2012-12-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/55124
	* tree-ssa-pre.c (find_or_generate_expression): Instead of
	ICEing when we are not able to generate an expression defer it
	by signalling failure.  Fix possible wrong-code issue by
	not picking random REFERENCE expressions as fallback.
	(create_component_ref_by_pieces_1): Adjust.  Add failure paths.
	(create_expression_by_pieces): Likewise.
	(insert_into_preds_of_block): When expression generation failed
	for one edge make sure to not insert a PHI node.

	* gcc.dg/torture/pr55124.c: New testcase.

From-SVN: r194125