This patch prevents the optimizer from producing wide vectors in the IR, specifically the
MMA types (v256i1, v512i1). The idea is that on Power, we only want to be producing
these types only if the vector_pair and vector_quad types are used specifically.
To prevent the optimizer from producing these types in the IR, vectorCostAdjustmentFactor()
is updated to return an instruction cost factor or an invalid instruction cost if the current type is
that of an MMA type. An invalid instruction cost returned by this function signifies to other
cost computing functions to return the maximum instruction cost to inform the optimizer that
producing these types within the IR is expensive, and should not be produced in the first place.
This issue was first seen in the test case included within this patch.
This should be returning unsigned. And the name should change to indicate that this is a factor.