Error control code management

A method of operating a data processor operable to execute programs to perform data processing operations, and in which plural execution threads may be grouped together into thread groups in which an instruction is executed upon one or more execution threads of a thread group, the method comprising:

• dividing each execution thread into at least two sub-thread data width groups;
• during a write access operation to update data values associated with a group of execution threads in a register file based on the execution of the instruction, the method further comprises:
• calculating a first error control code for a combination of the data values associated with each execution thread in the group of execution threads of a first sub-thread data width group;
• calculating a second error control code for a combination of the data values associated with each execution thread in the group of execution threads of a second sub-thread data width group;
• and
• writing the updated data values associated with a group of execution threads, the first error control code associated with the first sub-thread data width group, and the second error control code associated with the second sub-thread data width group to the register file.