Control of instruction issue based on issue groups

A non-transitory computer-readable medium to store computer-readable code for fabrication of an apparatus comprising:

• issue circuitry to issue micro-operations for execution;
• and
• issue group allocation circuitry to control allocation of each micro-operation to one of a plurality of issue groups, depending on detection of register conflicts between micro-operations, the register conflicts concerning access to registers of a first register set;
• in which:
• the issue group allocation circuitry is configured to allocate a given micro-operation to a selected issue group for which no micro-operation already allocated to the selected issue group has a register conflict with the given micro-operation and the selected issue group is a younger issue group than any issue group already allocated an older micro-operation than the given micro-operation for which a register conflict is detected between the given micro-operation and the older micro-operation;
• and
• the issue circuitry is configured to control issue of the micro-operations based on the issue groups, to prevent any instruction in a given issue group being issued until all micro-operations in any older issue group than the given issue group have been issued.