instruction selection based on size

in mips16, we have two versions of many of the instructions that have immediate fields.

one version is 16 bits and the other is 32 bits.

we want it to chose the 16 bit version but both patterns will match the selection dag if the
immediate fields is small enough.

any simple way to do this?



You can use the AddedComplexity field to give the smaller encoding priority in the SelectionDAG matcher.