A method and apparatus for including in a processor instructions for performing logical-comparison and branch support operations on packed or unpacked data. In one embodiment, a processor is coupled to a memory. The memory has stored therein a first data and a second data. The processor performs logical comparisons on the first and second data. The logical comparisons may be performed on each bit of the first and second data, or may be performed only on certain bits. For at least one embodiment, at least the first data includes packed data elements, and the logical comparisons are performed on the most significant bits of the packed data elements. The logical comparisons may include comparison of the same respective bits of the first and second data, and also includes logical comparisons of bits of the first data with the complement of the corresponding bits of the second data. Based on these comparisons, branch support actions are taken. Such branch support actions may include setting one or more flags, which in turn may be utilized by a branching unit. Alternatively, the branch support actions may include branching to an indicated target code location.