Method and apparatus for reducing branch prediction table pollution

The technical field is computer architectures that use branch prediction as a means to improve processing performance. A branch target structure predicts a branch target address for an instruction flow. To conserve space, only a portion of the branch target address is stored. The branch target address is reconstructed assuming that an unspecified portion of a current branch instruction address matches corresponding bits of the branch target address. A comparator determines if the unspecified portion of the current branch instruction address matches corresponding bits of the branch target address. If the unspecified portion of the current branch instruction address does not match the corresponding bits of the branch target address, update of the branch target structure is inhibited. Otherwise update allowed.