Extended-width shifter for arithmetic logic unit

摘要

A processor includes a shift device for extending the width of a rotator without increasing propagation delays. An extended-width result is obtained by combining a rotation result with a shift result in accordance with a mask that is selected in response to at least a portion of the value of the degree to which a data word is to be shifted.

主权项

1. An extended-width shifter, comprising:
a rotator arranged to sequentially rotate each bit of a first portion of a data word by a number of bit positions that is indicated by a first portion of a received shift degree to generate a rotation result, wherein each bit rotated out of the received first portion of a word is sequentially rotated in to an opposing vacated portion of the received first portion of a word to generate a wrap-around portion of the rotation result; a shifter arranged to sequentially shift each bit of a second portion of the data word by a number of bit positions that is indicated by a second portion of the received shift degree to generate a shift result, wherein the second portion of the shift degree includes lower-order bits of the first portion of the shift degree; and a bit-wise selector that is arranged to produce an extended-width result by using a mask to individually select one bit between of each bit of the shift result and each bit of a portion of the rotation result that includes the wrap-around portion of the rotation result, wherein the mask is selected at least in response to the second portion of the shift degree.