There is provided an apparatus including input circuitry that receives input data. Output circuitry outputs a sequence of instructions to be executed by data processing circuitry, at least some of the instructions being grouped into functions and generation circuitry performs a generation process to generate the sequence of instructions using the input data. The generation process causes at least one of the instructions in the sequence of instructions to store a state of control flow speculation performed during execution of the sequence of instructions and the stored state of control flow speculation is maintained between the functions.