13. A system for optimizing conditional statements in a program, the system comprising a hardware processor configured to implement a method comprising: obtaining, for a conditional expression used in a conditional statement in the program, a set of conditional expressions having an inclusion relation; computing a first provisional cost corresponding to the conditional expression being positive, and a second provisional cost corresponding to the conditional expression being negative; and moving the conditional expression to a move destination, wherein the move destination is determined by performing a data-flow analysis using expressions of positive and negative conditions of the conditional expression, and wherein moving the conditional expression comprises: in response to a result of the conditional expression not being cached in a variable, generating an if statement for the conditional expression and caching the result of the conditional expression in a new variable, wherein the if statement is generated in increasing order of the first provisional cost and the second provisional cost; and in response to the result of the conditional expression being cached in a variable, replacing a conditional operator of the conditional expression with a logical operator, prior to caching the result in the new variable.
13. A system for optimizing conditional statements in a program, the system comprising a hardware processor configured to implement a method comprising: obtaining, for a conditional expression used in a conditional statement in the program, a set of conditional expressions having an inclusion relation; computing a first provisional cost corresponding to the conditional expression being positive, and a second provisional cost corresponding to the conditional expression being negative; and moving the conditional expression to a move destination, wherein the move destination is determined by performing a data-flow analysis using expressions of positive and negative conditions of the conditional expression, and wherein moving the conditional expression comprises: in response to a result of the conditional expression not being cached in a variable, generating an if statement for the conditional expression and caching the result of the conditional expression in a new variable, wherein the if statement is generated in increasing order of the first provisional cost and the second provisional cost; and in response to the result of the conditional expression being cached in a variable, replacing a conditional operator of the conditional expression with a logical operator, prior to caching the result in the new variable. 16. The system of claim 13 , 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.