Signature buffer: bridging performance gap between registers and caches

Data communications between producer instructions and consumer instructions through memory incur extra delays that degrade processor performance. We introduce a new storage media with a novel addressing mechanism to avoid address calculations. Instead of a memory address, each load and store is assigned a signature for accessing the new storage. A signature consists of the color of the base register along with its displacement value. A unique color is assigned to a register whenever the register is updated. When two memory instructions have the same signature, they address to the same memory location. This memory signature can be formed early in the processor pipeline. A small signature buffer, addressed by the memory signature, can be established to permit stores and loads bypassing normal memory hierarchy for fast data communication. Performance evaluations based on an Alpha 21264-like pipeline using SPEC2000 integer benchmarks show that an IPC (instruction-per-cycle) improvement of 13-18% is possible using a small 8-entry signature buffer.