1. A computer-implemented method comprising, in a code transformation system: identifying one or more save-to-return code instructions; identifying one or more function call code instructions, said one or more function call code instructions being associated with said one or more save-to-return code instructions; identifying one or more comparison code instructions, said one or more comparison code instructions being associated with said one or more save-to-return code instructions; identifying one or more exceptional code instructions, said one or more exceptional code instructions being associated with said one or more comparison code instructions; determining a predefined proximity range based on a predefined proximity value said predefined proximity value is a number of code instructions between the one or more comparison code instructions and the save-to-return code instructions; determining a proximity eligibility indicator, said proximity eligibility indicator denoting whether said one or more save-to-return code instructions and said one or more comparison code instructions are within said predefined proximity range; responsive to said proximity eligibility indicator denoting said one or more save-to-return code instructions and said one or more comparison code instructions are within said predefined proximity range, modifying one or more code execution flow relationships between said one or more function call code instructions and said one or more exceptional code instructions, wherein the modifications to the one or more code instructions include deleting one or more code execution flow relationships between said one or more function call code instructions and said one or more exceptional code instructions and creating a new code execution flow relationship; and executing a code transformation system using the one or more modified code execution flow relationships which allows efficient estimation of execution flow relationships.