Mark all these functions as const.

src/mem/ruby/structures/CacheMemory.hh (Diff revision 1)

Can you add a comment here describing what this function does? I don't find it self explanatory from the function name/parameters.
E.g., what is the "idx" parameter? What is the min/max value (0 to getNumBlocks()-1, I assume)? Also, could you specify the mapping from idx to way/set (in the comment)? It's in the code, but the code is not easily parsable, at least to me.
Also, are you really getting the index, or are you getting the address at a specific index? Maybe a more precise name is needed as well.

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1. Brad Beckmann May 14, 2015, 9:44 a.m. (May 14, 2015, 9:44 a.m.)

   I added the following comment to the function.  Does this work for you:
   // Given an unique cache block identifier (idx): return the valid address
   
   // stored by the cache block.  If the block is invalid/notpresent, the 
   
   // function returns the 0 address

2. Jason Lowe-Power May 14, 2015, 2:05 p.m. (May 14, 2015, 2:05 p.m.)

   Sorry to be picky here, but I still don't quite understand. Is a cache block identifier a common thing? I personally don't know what it is based on just that phrase. Is each block in the cache assigned a number from 0 to number of blocks? Which block is 0, which is 1, or does this not matter for some reason? From what I can tell you're taking what's usually refered to as sets/ways and linearizing it. If you could explain how it's linearized it would make this clear.

3. Brad Beckmann May 14, 2015, 3:14 p.m. (May 14, 2015, 3:14 p.m.)

   This feature is not meant to be complicated.  Yes, the input idx parameter is just an integer between 0 and the number of blocks.  The function returns the tag at that "linearized" location in the cache.
   There is no special logic to "linearize" the cache.  The way and set is simply determined using the arithmetic implemented in the function.  There really is no magic going on outside this function.

4. Nilay Vaish May 15, 2015, 7:45 a.m. (May 15, 2015, 7:45 a.m.)

   I think the function should be renamed since it is not returning the tag but the address.
   How about getAddressAtIdx()?

5. Brad Beckmann May 19, 2015, 1:27 p.m. (May 19, 2015, 1:27 p.m.)

   Sure.  The unique information provided by the function is a tag, but renaming it Address better describes the returned data structure.
   This did not make it into the patch that Tony posted a few days ago, but it will be updated in the next posted round of patches.

Ship It!