Cache-line retention hint information for conditional write instruction

Abstract

In response to instruction decoding circuitry decoding a conditional write instruction, processing circuitry determines whether a predetermined condition is satisfied for a target cache line corresponding to a target address specified by the conditional write instruction. If the predetermined condition is satisfied for the target cache line, a write request is issued to update the target cache line. If the predetermined condition is not satisfied for the target cache line, a failure indication is returned. The processing circuitry selects, depending on whether the sequence of instructions specifies cache-line-retention hint information applicable to the conditional write instruction, whether to prevent a unique coherency state of the target cache line being relinquished by a local cache associated with the processing circuitry for a retention period following processing of the conditional write instruction. The unique coherency state comprises a coherency state in which the processing circuitry has exclusive right to update the target cache line.