L1 cache synonyms in a two-level cache system are detected and resolved by
logic in the L2 cache. Duplicate copies of the L1 cache tags and state
("Dtags") are maintained in the L2 cache. After a miss occurs in the L1
cache, the Dtags in the second-level cache that correspond to all possible
synonym locations in the L1 cache are searched for synonyms. If a synonym
is found, the L2 cache notifies the L1 cache where the requested cache
line can be found in the L1 cache. The L1 cache then copies the cache line
from the location where the synonym was found to the location where the
miss occurred, and it invalidates the cache line at the original location.
The Dtags in the second-level cache are updated to reflect the changes
made in the L1 cache.
