SIMD 기계에서 중첩된 조건문을 위한 조건 실행 방법

When designing processors, SIMD technique is a widely used, simple and effective method for gaining performance. However, since the processing units inside the SIMD unit need to perform the same operation, it is difficult to deal with complex control flows, thus limiting performance gain. To solve this problem, SIMD-based processors usually adopt predicated execution schemes. However, it cannot solve the problem fully, since general predicated execution schemes do not support nested-if structures. Although there is an existing solution to the problem, it requires additional instructions to be inserted, thereby incurs some performance overhead. To eliminate this overhead, we propose a new predicated execution scheme for supporting nested-if structure, which requires only negligible area overhead and no performance overhead.