Multilevel reverse most-significant carry computation
IEEE Transactions on Very Large Scale Integration (VLSI) Systems - System Level Design
Multilevel Reverse-Carry Addition: Single and Dual Adders
Journal of VLSI Signal Processing Systems
Multilevel Reverse-Carry Adder
ICCD '00 Proceedings of the 2000 IEEE International Conference on Computer Design: VLSI in Computers & Processors
Journal of Systems Architecture: the EUROMICRO Journal
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We present efficient methods to determine the four usual branch conditions for a sum or difference, before the result of the addition or subtraction is available. The methods lead to the design of an early branch resolver which integrates well with a regular adder/subtracter, adding only a small amount of circuitry and almost no delay. The methods exploit the properties of half-adder form. Sums in half-adder form can be computed very quickly (with the delay of a half adder), yet they have enough structure so that many of the properties of the final sum can be easily detected. The reduced latency for evaluating branch conditions means that an addition or subtraction and a dependent conditional instruction can execute in the same cycle, with a consequent increase in instruction-level parallelism, and improved performance for both single-issue and superscalar processors.