Synchronization of predetermined class of load/store operations

A method comprising:

• for a predetermined class of load/store operations, buffering store data of store operations of the predetermined class in a predetermined-class store buffer, and controlling store-to-load forwarding of store data from the predetermined-class store buffer to load operations of the predetermined class;
• in response to a predetermined-class-load/store synchronization instruction, controlling load/store processing circuitry to control that, for a hazarding younger non-predetermined-class load/store operation occurring after the predetermined-class-load/store synchronization instruction in program order and a hazarding older predetermined-class store operation occurring before the predetermined-class-load/store synchronization instruction in program order, for which an address range accessed by the hazarding younger non-predetermined-class load/store operation overlaps with an address range accessed by the hazarding older predetermined-class store operation, the hazarding younger non-predetermined-class load/store operation observes a result of the hazarding older predetermined-class store operation;
• in which:
• in absence of any intervening predetermined-class-load/store synchronization instruction occurring in program order between a given older predetermined-class store operation and a given younger non-predetermined-class load/store operation for which an address range accessed by the given older predetermined-class store operation overlaps with an address range accessed by the given younger non-predetermined-class load/store operation, the given younger non-predetermined-class load/store operation is permitted to yield a result which fails to observe a result of the given older predetermined-class store operation.

An apparatus comprising:

• load/store processing circuitry to process load/store operations, including guarded-control-stack (GCS) load/store operations for accessing a GCS data structure for protecting return state information for returning from a function call or exception;
• and
• an instruction decoder responsive to a GCS synchronization instruction to control the load/store processing circuitry to enforce that, for a hazarding younger non-GCS-load/store operation occurring after the GCS synchronization instruction in program order and a hazarding older GCS store operation occurring before the GCS synchronization instruction in program order, for which an address range accessed by the hazarding younger non-GCS load/store operation overlaps with an address range accessed by the hazarding older GCS store operation, the hazarding younger non-GCS load/store operation observes a result of the hazarding older GCS store operation;
• in which:
• in absence of any intervening GCS synchronization instruction occurring in program order between a given older GCS store operation and a given younger non-GCS load/store operation for which an address range accessed by the given older GCS store operation overlaps with an address range accessed by the given younger non-GCS load/store operation, the load/store processing circuitry is configured to permit the given younger non-GCS load/store operation to yield a result which fails to observe a result of the given older GCS store operation.

A method comprising:

• processing load/store operations, including guarded-control-stack (GCS) load/store operations for accessing a GCS data structure for protecting return state information for returning from a function call or exception;
• and
• in response to a GCS synchronization instruction, controlling load/store processing circuitry to enforce that, for a hazarding younger non-GCS-load/store operation occurring after the GCS synchronization instruction in program order and a hazarding older GCS store operation occurring before the GCS synchronization instruction in program order, for which an address range accessed by the hazarding younger non-GCS load/store operation overlaps with an address range accessed by the hazarding older GCS store operation, the hazarding younger non-GCS load/store operation observes a result of the hazarding older GCS store operation;
• in which:
• in absence of any intervening GCS synchronization instruction occurring in program order between a given older GCS store operation and a given younger non-GCS load/store operation for which an address range accessed by the given older GCS store operation overlaps with an address range accessed by the given younger non-GCS load/store operation, the given younger non-GCS load/store operation is permitted to yield a result which fails to observe a result of the given older GCS store operation.