Write merging on stores with different tags

1. A caching system comprising:

a first sub-cache; and

a second sub-cache, coupled in parallel with the first sub-cache, for storing cache data evicted from the first sub-cache and write-memory commands that are not cached in the first sub-cache, the second sub-cache including:

color tag bits configured to store an indication that a corresponding line of the second sub-cache is associated with a color tag; and

an eviction controller configured to evict cache lines of the second sub-cache storing write-memory data based on the color tag associated with the line, and

wherein the second sub-cache is further configured to:

receive a first write memory command for a memory address, the first write memory command associated with a first color tag;

store first data associated with the first write memory command in a cache line of the second sub-cache;

store the first color tag in the second sub-cache;

receive a second write memory command for the cache line, the second write memory command associated with a second color tag;

merge the second color tag with the first color tag to produce a merged color tag;

store the merged color tag; and

evict the cache line based on the merged color tag.

2. The caching system of claim 1 , wherein the first color tag and the second color tag represent the same color tag.

3. The caching system of claim 1 , wherein the first color tag and the second color tag represent different color tags, and wherein the merged color tag comprises a first bit representing the first color tag and a second bit representing the second color tag.

4. The caching system of claim 3 , wherein the second sub-cache is further configured to evict the cache line based on the first color tag.

5. The caching system of claim 4 , wherein the second sub-cache is further configured to evict the cache line based on the second color tag.

6. The caching system of claim 1 , wherein the first color tag and the second color tag are stored in a bit field in a memory tracking modified, exclusive, shared, and invalid (MESI) state of entries in the second sub-cache data.

7. The caching system of claim 6 , wherein the bit field includes a bit storing the state for each color tag.

8. A method for caching data, comprising:

receiving, by a caching system, a first write memory command for a memory address, the first write memory command associated with a first color tag;

determining, by a first sub-cache of the caching system, that the memory address is not cached in the first sub-cache;

determining, by second sub-cache of the caching system, that the memory address is not cached in the second sub-cache, wherein the second sub-cache is configured to store, in parallel with the first sub-cache, cache data evicted from the first sub-cache and write-memory commands that are not cached in the first sub-cache;

storing first data associated with the first write memory command in a cache line of the second sub-cache;

storing the first color tag in the second sub-cache;

receiving a second write memory command for the cache line, the second write memory command associated with a second color tag;

merging the second color tag with the first color tag to produce a merged color tag;

storing the merged color tag; and

evicting the cache line based on the merged color tag.

9. The method of claim 8 , wherein the first color tag and the second color tag represent the same color tag.

10. The method of claim 8 , wherein the first color tag and the second color tag represent different color tags, and wherein the merged color tag comprises a first bit representing the first color tag and a second bit representing the second color tag.

11. The method of claim 10 , wherein the evicting is based on the first color tag.

12. The method of claim 11 , wherein the evicting is based on the second color tag.

13. The method of claim 8 , wherein the first color tag and the second color tag are stored in a bit field in a memory tracking a modified, exclusive, shared, and invalid (MESI) state of entries in the second sub-cache data.

14. The method of claim 13 , wherein the bit field includes a bit storing the state for each color tag.

15. A device comprising:

a processor;

a first sub-cache; and

a second sub-cache coupled in parallel with the first sub-cache, for storing cache data evicted from the first sub-cache and write-memory commands that are not cached in the first sub-cache, and the second sub-cache including:

color tag bits configured to store an indication that a corresponding line of the second sub-cache is associated with a color tag; and

an eviction controller configured to evict cache lines of the second sub-cache storing write-memory data based on the color tag associated with the line, and

wherein the second sub-cache is further configured to:

receive a first write memory command for a memory address, the first write memory command associated with a first color tag;

store first data associated with the first write memory command in a cache line of the second sub-cache;

store the first color tag in the second sub-cache;

receive a second write memory command for the cache line, the second write memory command associated with a second color tag;

merge the second color tag with the first color tag to produce a merged color tag;

store the merged color tag; and

evict the cache line based on the merged color tag.

16. The device of claim 15 , wherein the first color tag and the second color tag represent the same color tag.

17. The device of claim 15 , wherein the first color tag and the second color tag represent different color tags, and wherein the merged color tag comprises a first bit representing the first color tag and a second bit representing the second color tag.

18. The device of claim 17 , wherein the second sub-cache is further configured to evict the cache line based on the first color tag.

19. The device of claim 18 , wherein the second sub-cache is further configured to evict the cache line data based on the second color tag.

20. The device of claim 15 , wherein the first color tag and the second color tag are stored in a bit field in a memory tracking modified, exclusive, shared, and invalid (MESI) state of entries in the second sub-cache data.