\brief Build a a series of PTRSUB ops at different offsets, given a root pointer Offsets and data-types are based on \b dataTypePieces, taking input data-types if \b isInput is \b true, output data-types otherwise. The data-types, relative to the root pointer, are assumed to start at the given base offset. \param rootVn is the root pointer \param ptrType is the pointer data-type associated with
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