Methods, systems, and articles of manufacture for computing program equivalence based on a hierarchy of program semantics and related canonical representations are provided herein. A method includes defining a program semantic representation for a first program; generating a search query based on said semantic representation for the first program; executing said search query against an index of multiple programs to determine a set of candidate programs among the multiple programs, wherein said index comprises a program semantic representation defined for each of the multiple programs; and identifying one or more programs among the set of candidate programs that match the first program by performing one or more comparisons, across the set of candidate programs, of a canonical representation associated with each program in the identified set of candidate programs to a canonical representation associated with the first program.