Generation of Instruction Set from Architecture Description

Generating an instruction set for an architecture. A hierarchical description of an architecture is accessed. Groups in the hierarchical description that can be pre-encoded without increasing final width of said instruction set are pre-encoded. The hierarchical description is permutated into a plurality of variations. Each variation comprises a leaf-group and one or more sub-graphs to be encoded. For each said variation, the leaf-group and the one or more sub-graphs are encoded to produce a potential instruction set for each variation. One of the potential instruction sets is selected.