Apparatus and method for generating a vector of elements with a wrapping constraint

Abstract

An apparatus is provided that receives a scalar start value, an adjust amount and wrapping control information, and includes vector generating circuitry for generating a vector comprising a plurality of elements such that a value of a first element is dependent on the scalar start value, and values of the plurality of elements follow a regularly progressing sequence that is constrained to wrap as required to ensure that each value is within bounds determined from the wrapping control information. The adjust amount is used to determine a difference between values of adjacent elements in the regularly progressing sequence. The vector generating circuitry has first adder circuitry for generating a plurality of first candidate values for the plurality of elements, assuming absence of a wrapping condition, and second adder circuitry for generating a plurality of second candidate values for the plurality of elements, assume presence of a wrapping condition. Wrap detection circuitry determines an adjustment limit value that provides an indication of a total number of regularly progressing values differing by the adjust amount that are available within the bounds determined from the wrapping control information, and a current adjustment value that, taking into account the scalar start value, provides an indication of an initial number of regularly progressing values differing by the adjust amount that are available before the wrapping condition occurs. Result selection circuitry selects, for each element in the plurality of elements, one of the first candidate values and the second candidate values, in dependence on at least the adjustment limit value and the current adjustment value.