2011-10-23  Tom de Vries  <tom@codesourcery.com>

	PR tree-optimization/50763
	* tree-ssa-tail-merge.c (same_succ_flush_bb): New function, factored out
	of ...
	(same_succ_flush_bbs): Use same_succ_flush_bb.
	(purge_bbs): Remove argument.  Remove calls to same_succ_flush_bbs,
	release_last_vdef and delete_basic_block.
	(unlink_virtual_phi): New function.
	(update_vuses): Add and use vuse1_phi_args argument.  Set var to
	SSA_NAME_VAR of vuse1 or vuse2, and use var.  Handle case that def_stmt2
	is NULL.  Use phi result as phi arg in case vuse1 or vuse2 is NULL_TREE.
	Replace uses of vuse1 if vuse2 is NULL_TREE.  Fix code to limit
	replacement of uses.  Propagate phi argument for phis with a single
	argument.
	(replace_block_by): Update vops if phi_vuse1 or phi_vuse2 is NULL_TREE.
	Set vuse1_phi_args if vuse1 is a phi defined in bb1.  Add vuse1_phi_args
	as argument to call to update_vuses.  Call release_last_vdef,
	same_succ_flush_bb, delete_basic_block.  Update CDI_DOMINATORS info.
	(tail_merge_optimize): Remove argument in call to purge_bbs.  Remove
	call to free_dominance_info.  Only call calculate_dominance_info once.

From-SVN: r180341