1. A data processing apparatus comprising: a processor; a memory; a comparison controller configured to perform an element comparison process between a first vector of data elements and a second vector of data elements, said element comparison process comprising performing a comparison of a first data element at a first index in said first vector with a second data element at a second index in said second vector; and a hazard vector generator configured, when said comparison controller determines a match condition between said first data element and said second data element, to populate a hazard vector at an index determined by said first index with a value dependent on said second index, wherein said comparison controller is configured to perform said element comparison process by iteratively performing said comparison for data elements of said first vector with each element of a subset of said second vector, wherein the element comparison process comprises a plurality of iterations, each iteration comparing a data element at a current index of said first vector with each element of said subset of said second vector, and wherein said comparison controller is configured to determine said subset of said second vector as those data elements of said second vector at indices which are less than said current index of said first vector and which are greater than any previously determined value of said second index for said match condition, and, in response to determining the match condition between said first data element and said second data element when said first data element is a data element of said first vector other than a last data element of said first vector, to omit from the element comparison process any further comparisons for data elements at indices of said second vector which are less than or equal to said any previously determined value of said second index for said match condition and perform one or more further comparisons for one or more data elements at indices of said second vector which are greater than said any previously determined value of said second index for said match condition; and the hazard vector generator is configured to output said hazard vector populated based on said element comparison process.