3. The non-transitory computer readable storage media of claim 2 , wherein determining the cost of execution of the program with the conditional expression moved to the move destination comprises: determining a first provisional cost corresponding to the conditional expression being positive; and determining a second provisional cost corresponding to the conditional expression being negative, wherein the cost is a sum of the first provisional cost and the second provisional cost.
5. The non-transitory computer readable storage media of claim 3 , wherein the first provisional cost is computed for the conditional expression as a product of a number of expressions being true in response to the conditional expression being positive, and a probability of the conditional expression being true; and the second provisional cost is computed for the conditional expression as a product of a number of expressions being true in response to the conditional expression being negative, and a probability of the conditional expression being false.