Masking operations should support default value source.

[edanor]

Currently all masking operations are using implicit vector operand as a source of default value. In order to get a value other than default, user has to first do an ASSIGN operation and then perform a specific masking operation. Because compiler is not guaranteed to optimize these two calls and merge them into one operation, it might be necessary to add additional operations that take some other, default operand. In practice this modification will double the number of masking operations supported by the interface.

What needs to be done: check if there is a performance penalty between current and new approach, and add operations with default value when necessary.

[Note to users] Please add comments if you are interested in this feature and/or if you have any hints on this idea.