Memory ordering queue/versioning cache circuit
A processor includes a circuit for tracking memory operations with trace-based execution. Each trace includes a sequence of operations that includes zero or more of the memory operations. The memory operations being executed form a set of active memory operations that have a predefined program order among them. At least some of the active memory operations access the memory in an execution order that is different from the program order. During the operation of the circuit, none of the operations of a given trace has any effect on the execution unit's architectural state prior to committing that trace. Each trace becomes eligible for commitment after all operations in the trace complete executing. The circuit also includes a sub-circuit that holds memory operation ordering information corresponding to the active memory operations. The sub-circuit detects violations of ordering constraints. After each trace is committed, the sub-circuit invalidates all of the memory operation ordering information associated with the trace.
1. A circuit for tracking memory operations in an out-of-order and speculative processor,
wherein the circuit is adapted for use with a trace unit and with an execution unit of the processor, where the trace unit sequences traces for execution thereby forming a trace sequence order, where each of the traces includes a sequence of operations that includes zero or more of the memory operations, where the execution unit executes the operations and has an architectural state, and where the circuit comprises:
a memory configured to cache at least some of the data accessed by the memory operations,
wherein the memory operations being executed form a set of active memory operations, where the active memory operations have a predefined program order among themselves, where the predefined program order imposes a set of ordering constraints, and where at least some of the active memory operations access the memory in an execution order that is different from the predefined program order;
a sub-circuit configured to hold memory operation ordering information corresponding to the active memory operations, and configured to detect a violation of the ordering constraints;
wherein none of the operations of a first particular one of the traces has any effect on the architectural state prior to a commitment of the first particular trace, and where the first particular trace becomes eligible for the commitment after the execution completes for all operations of the first particular trace; and
wherein the sub-circuit is further configured to invalidate all of the memory operation ordering information associated with the first particular trace after the commitment of the first particular trace, provided that the first particular trace does commit.
2. The circuit of claim 1 , where:
the sub-circuit is further configured to hold all of the memory operation ordering information associated with a second particular one of the traces until after the second particular trace commits, provided that the second particular trace does commit.
3. The circuit of claim 1 , where:
none of the operations of a third particular one of the traces has any effect on the architectural state, provided that the third particular trace does abort; and
the sub-circuit is further configured to invalidate all of the memory operation ordering information associated with the third particular trace after the third particular trace does abort, provided that the third particular trace aborts.
4. The circuit of claim 1 , where:
none of the operations of a fourth particular one of the traces has any effect on the architectural state, provided that the fourth particular trace does abort; and
the sub-circuit is further configured to hold all of the memory operation ordering information associated with the fourth particular trace until after the fourth particular trace abort, provided that the fourth particular trace does abort.
5. The circuit of claim 1 , where the operation sequences of a set of at least two of the traces are executed concurrently by the execution unit, where the active memory operations include a memory operation from a first particular one of the set, and where the active memory operations include a memory operation from a second particular one of the set.
6. The circuit of claim 1 , where:
the memory is further configured to cache at least some of the active memory operations that are the cacheable type; and
the sub-circuit is further configured to hold operation ordering information for the at least some of the active memory operations.
7. The circuit of claim 1 , where:
the active memory operations include all memory operations being executed that are a write combining type of memory operation; and
the sub-circuit is further configured to hold operation ordering information for each one of the active memory operations that is of the write combining type.