SIMD variable shift and rotate using control manipulation

Vector single instruction multiple data (SIMD) shift and rotate instructions are provided specifying: a destination vector register comprising fields to store vector elements, a first vector register, a vector element size, and a second vector register. Vector data fields of a first element size are duplicated. Duplicate vector data fields are stored as corresponding data fields of twice the first element size. Control logic receives an element size for performing a SIMD shift or rotation operation. Through selectors corresponding to a vector element, portions are selected from the duplicated data fields, the selectors corresponding to any particular vector element select all portions similarly from the duplicated data fields for that particular vector element responsive to the first element size, but selectors corresponding to any particular vector element select at least two portions from the duplicated data fields differently for that particular vector element responsive to a second element size.