1. A program execution control device which controls execution of a program by a processor having a predicate function for conditional execution of an instruction, wherein the program includes a branch instruction to control iterations in loop processing, the branch instruction is further an instruction to generate an execute-or-not condition indicating whether or not the branch instruction is to be executed at an iteration in the loop processing after a current iteration, and to reflect the execute-or-not condition on a predicate flag used for conditional execution of the branch instruction, said program execution control device comprises a processor status changing unit configured to change, before an execution cycle of the branch instruction, a status of the processor in advance for execution of an instruction following the branch instruction, the status being changed based on the execute-or-not condition reflected on the predicate flag.