This introduces simplify_logical_relational_operation. Currently the
only thing implemented it can simplify is the IOR of two CONDs of the
same arguments.
* simplify-rtx.c (comparison_to_mask): New function.
(mask_to_comparison): New function.
(simplify_logical_relational_operation): New function.
(simplify_binary_operation_1): Call
simplify_logical_relational_operation.