ISSUANCE AND EXECUTION OF MEMORY INSTRUCTIONS TO AVOID READ-AFTER-WRITE HAZARDS

摘要

A method and apparatus for issuing and executing memory instructions so as tomaximize the number of requests issued to a highly pipelined memory and avoidreading data from memory (10) before a corresponding write to memory (10). Thememory is divided into a number of regions, each of which is associated with afence counter (18) that is incremented each time a memory instruction that istargeted to the memory region is issued and decremented each time there is awrite to the memory region. After a fence instruction is issued, no furthermemory instructions (23) are issued if the counter for the memory regionspecified in the fence instruction is above a threshold. When a sufficientnumber of the outstanding issued instructions are executed, the counter willbe decremented below the threshold and further memory instructions are thenissued.