OPERAND CACHE FLUSH, EVICTION, AND CLEAN TECHNIQUES

摘要

An apparatus includes an operand cache for storing operands from a register file for use by execution circuitry. In some embodiments, eviction priority for the operand cache is based on the status of entries (e.g., whether dirty or clean) and the retention priority of entries. In some embodiments, flushes are handled differently based on their retention priority (e.g., low-priority entries may be pre-emptively flushed). In some embodiments, timing for cache clean operations is specified on a per-instruction basis. Disclosed techniques may spread out write backs in time, facilitate cache clean operations, facilitate thread switching, extend the time operands are available in an operand cache, and/or improve the use of compiler hints, in some embodiments

主权项

1. An apparatus, comprising:
an execution unit; a register file configured to store operands for instructions to be executed by the execution unit; and an operand cache that includes a plurality of entries configured to store source operands from the register file and result operands of operations by the execution unit, wherein entries of the operand cache include fields that comprise at least:
a hint field indicating a retention priority for the operand stored by the entry; anda dirty field indicating whether the operand stored by the entry has been modified; wherein the apparatus is configured to select an entry to evict from the operand cache according to the following priority order:
select, at a first priority level, the entry from clean entries associated with a first hint field value that indicates a first retention priority;select, at a second priority level that is lower than the first priority level, the entry from dirty entries associated with a second hint field value that indicates a second retention priority that is higher than the first retention priority; andselect, at a third priority level that is lower than the second priority level, the entry from clean entries associated with the second hint field value that indicates the second retention priority.