BRANCH TARGET BUFFER COMPRESSION

Techniques for improving branch target buffer ("BTB") operation. A compressed BTB is included within a branch prediction unit along with an uncompressed BTB. To support prediction of up to two branch instructions per cycle, the uncompressed BTB includes entries that each store data for up to two branch predictions. The compressed BTB includes entries that store data for only a single branch instruction for situations where storing that single branch instruction in the uncompressed BTB would waste space in that buffer. Space would be wasted in the uncompressed BTB due to the fact that, in order to support two branch lookups per cycle, prediction data for two branches must have certain features in common (such as cache line address) in order to be stored together in a single entry.