A New Approach to Three-Level Logic Synthesis

Three-level logic SPP forms are OR of AND of EXORs expressions. In the framework of SPP minimization we give a new algebraic definition of SPP expressions using affine spaces. The main problems of SPP model are: the ``hard to digest'' SPP theory; the time required for minimization, which is still high; and the unbounded fan-in EXOR gates in the form. Consequently, our main results in this paper are: 1) we rephrase the SPP theory using well known algebraic structures (vector and affine spaces) to obtain an easier description of pseudocubes, which play the same role as cubes in standard minimization; 2) we describe a new canonical representation of pseudocubes leading to a more efficient data structure for SPP minimization; 3) we introduce a novel form, called k-SPP form}, where the number of literal in the EXOR factors is upper bounded by a chosen constant $k$, and show how to modify the SPP algorithms for computing the minimal k-SPP form efficiently. Finally, we perform an extensive set of experiments on classical benchmarks aimed at validating the new approach.