1. A control device for speculative instruction execution, comprising: an instruction fetch unit configured to fetch an instruction to be executed by a processor; a value prediction unit configured to predict a value obtained as an execution result of a target instruction for prediction in the case where instruction fetched by the instruction fetch unit is the target instruction for prediction; a branch instruction insertion unit configured to dynamically insert, based on a signal transmitted from the value prediction unit, a branch instruction subsequent to the target instruction for prediction in a group of instructions comprising a target instruction for prediction for which a value is predicted by the value prediction unit and an instruction subsequent to the target instruction for prediction; an instruction issuing unit configured to hold a fetched instruction and speculatively issue an instruction subsequent to the target instruction for prediction to an execution unit without waiting for an execution result for the target instruction for prediction using the value predicted by the value prediction unit; an execution unit configured to execute an instruction issued from the instruction issuing unit; a branch prediction control unit configured to predict a branch destination for a branch instruction and perform verification of a branch prediction; and a commit unit configured to commit each instruction in a group of instructions executed by the execution unit, and invalidate and re-execute a speculatively executed instruction when the predicted value and execution result do not match; wherein the branch prediction control unit verifies a value prediction by comparing the predicted value predicted by the value prediction unit and the execution result of the target instruction for prediction executed by the execution unit upon execution of the inserted branch instruction, and transmits to the commit unit a signal that indicates that a predicted value and execution result do not match when the predicted value and the execution result do not match.