Fitting for incremental compilation of electronic designs

Abstract

A technique is disclosed for efficiently placing logic cells from an electronic design during an incremental recompile. This is accomplished by fixing in place as many logic cells as possible during the recompile procedure. To understand how this works, recognize than an 'original electronic design' has already been fully compiled. Now, a user has made one or more changes to the original electronic design to produce a 'changed electronic design.' The disclosed technique fits the changed electronic design, during incremental recompile, without effecting too much of the logic previously fit during compilation of the original electronic design. Initially, a compiler attempts to fit logic cells of the changed portion of the electronic design onto available logic elements of the hardware device while confining logic cells from the unchanged portion of the changed electronic design to their original positions. If this fails, the compiler allows logic cells from the unchanged portion of the changed electronic design to shift by a limited amount to other logic elements within the target hardware device. At first, this shifting is fairly constrained in order to preserve as much of the original compilation's placement as possible. However, if fitting can not be accomplished under these constraints, gradually the constraints are lifted, until a fit is achieved.