Store sets poison propagation

A method of processing a store instruction (store) to execute before a load instruction (load) that target a common memory location, comprising:

• (a) determining if the data to be written by said store is stale;
• (b) if said data is stale, setting a value associated with said store;
• and
• (c) if said value is set, re-processing said load to execute after said data is no longer stale.

A computer system, comprising:

• a microprocessor;
• an input device coupled to said microprocessor;
• and
• memory coupled to said microprocessor, said memory containing executable instructions;
• wherein said microprocessor:
• fetches instructions from said memory, certain fetched instructions being load instructions (loads) and causing load operations, and other fetched instructions being store instructions (stores) and causing store operations;
• executes the fetched instructions out of program order;
• detects a load/store order violation wherein a load executes prior to a store on whose data the load depends;
• creates a store set for the load;
• adds the store to the store set;
• determines whether the store is poisoned by a previously poisoned instruction;
• if the store is poisoned, sets a poison value that indicates that the store is poisoned;
• and
• re-processes said load if said poison value associated with said store indicates the store has been poisoned.

A computer system, comprising:

• a microprocessor;
• and
• memory coupled to said microprocessor, said memory containing a store instruction (store) and a load instruction (load) that target a common memory location;
• wherein said microprocessor:
• fetches said load and store;
• determines if the data to be written by said store is stale;
• if said data is stale, sets a value associated with said store;
• if said value is set, re-processes said load to execute after said data is no longer stale.

A microprocessor, comprising:

• a fetch stage which fetches executable instructions from memory, certain fetched instructions being load instructions (loads) and causing load operations, and other fetched instructions being store instructions (stores) and causing store operations;
• an execution stage coupled to said fetch stage which executes the fetched instructions out of program order;
• and
• logic coupled to said fetch and execution stages that detects a load/store order violation wherein a load executes prior to a store on whose data the load depends, creates a store set for the load, adds the store to the store set, determines whether the store is poisoned by a previously poisoned instruction, if the store is poisoned, sets a poison value that indicates that the store is poisoned, and re-processes said load if said poison value associated with said store indicates the store has been poisoned.