1. A semiconductor integrated circuit device which executes a plurality of threads each as a software execution unit while switching the threads synchronously with clocks, comprising: a first register used for execution of a first thread in the threads; a second register used for execution of a second thread different from the first thread, in the threads; and a comparison circuit for comparing a result of execution of the first thread and a result of execution of the second thread when the first and second threads are execution units of the same specific software, wherein the first and second registers are different registers.