Programs having a given instruction-set architecture are executed on a multiprocessor system comprising a plurality of processors, for example of a VLIW type, each of said processors being able to execute, at each processing cycle, a respective maximum number of instructions. The instructions are compiled as instruction words of given length executable on a first processor. At least some of the instruction words of given length are converted into modified-instruction words executable on a second processor. The operation of modifying comprises in turn at least one operation chosen in the group consisting of: splitting the instruction words into modified-instruction words; and entering no-operation instructions in the modified-instruction words.