[PATCH] Merge flow-sensitive info in merge_alias_info

[Diego Novillo]

Richard Guenther wrote:

> This patch makes us merge flow-sensitive alias info in simple propagation
> cases where we previously failed to do so.  I am not sure if this just
> increases precision or also fixes correctness, so if it is appropriate
> for stage3 or not.

It should not affect correctness one way or the other, so I think it 
should be harmless.

> 	* tree-ssa-copy.c (may_propagate_copy): Remove redundant
> 	checks.
> 	(merge_alias_info): Do verification only if checking is
> 	enabled.  Merge flow-sensitive alias information in simple
> 	cases.
> 	* tree-ssa-operands.c (get_addr_dereference_operands): Also
> 	complain about missing NMTs.
> 
> 	* gcc.dg/tree-ssa/alias-17.c: New testcase.

OK.