Yoga: A Hybrid Dynamic VLIW/OoO Processor

Out of order (OoO) processors use complex logic to maximize Instruction Level Parallelism (ILP). However, since the resulting dynamic instruction schedule of many applications seldom changes, it is reasonable to store and reuse the schedule instead of reconstructing it each time. To do this, we propose Yoga, a hybrid VLIW/OoO processor that dynamically stores instruction schedules generated while in OoO mode as enlarged basic blocks for future VLIW execution. The enlarged basic blocks are transformed into VLIW words, where the width of the VLIW words corresponds to the ILP found in each block. Yoga switches between OoO mode and VLIW mode, depending on the costs and benefits at each point in time, saving power by turning off OoO structures and unused VLIW lanes when in VLIW mode. Yoga reduces energy consumption by 10% on average, with a maximum of 18%, with negligible performance loss with respect to a conventional OoO processor.