xcell: A cell library characterizer

xcell is a cell library characterizer. It takes in a configuration file (xcell.conf) and an ACT file that is used to provide the list of cells to be characterized, and runs a large number of SPICE simulations to generate timing and energy tables in the .lib file format.

Cells are defined in ACT using defcell. The ports to cells should only use boolean variables, and direction flags should be specified so that tools know which ports correspond to inputs v/s outputs. The following is an example of a buffer cell:

defcell BUFX2 (bool? A; bool! Y)
{
  bool _Y;
  prs {
    A => _Y-
    _Y => Y-
  }
  sizing { _Y{-1}; Y{-2} }
}