1. A method of converting a computer program into an execution speed optimized computer program, the method comprising: detecting, within one of a COBOL source code or a COBOL binary executable program, a sign assignment instruction having an input operand and an output operand identical in size to each other, the sign assignment instruction comprising a ZAP instruction operating on an input operand having a packed decimal format, the sign assignment instruction operating to assign a value of zero to a packed decimal data value of the input operand having a value of negative zero; analyzing, based on the detecting, the input operand of the sign assignment instruction to determine whether a value of the input operand results from an add or subtract operation and whether the value is greater than the value prior to the operation; and based on the analyzing determining at least one of that the value of the input operand does not result from an add or subtract operation or that the value is not greater than the value prior to the operation, checking, based on the input operand and the output operand of the sign assignment instruction having identical addresses, that the input operand of the sign assignment instruction is able to have a value of negative zero; removing, to create an optimized COBOL binary executable program, the sign assignment instruction comprising the ZAP instruction based on determining addresses of the input operand and the output operand are identical; replacing, in the optimized COBOL binary executable program based on determining that the input operand and the output operand of the sign assignment instruction have different addresses and do not overlap each other, the sign assignment instruction comprising the ZAP instruction with a copy instruction to copy the input operand to the output operand; and outputting, based on the removing or replacing, the optimized COBOL binary executable program.