Indicating cleanup in the index file

Any routine that does not throw the flag value of 8 will be evaluated by the install as a cleanup possibility. Flag values are very important for indicating opportunities for cleanup. Here is an example from the release:
  1 480 4 4 1 1 1 4 4 2 ATL_mm4x4x2US.c "V. Nguyen & P. Strazdins"

OK, as always, we can read this to see that MB and NB must be multiples of 4, and that KB can be any value. With no flag modifiers, if we wanted to use the routine for K cleanup, we would have to compile it into $N_B$ different routines, since loop dimensions are compile-time parameters by default. However, this routine is modified by a flag value of 480. What does this mean? Consulting table 1, we see that $32 + 64 + 128 + 256 = 480$, which means lda and ldb are not restricted to KB (i.e., they are run-time parameters to the routine), the M-loop is controlled by a run-time variable, the N-loop is controlled by a run-time variable, and the K-loop is controlled by a run-time variable. We therefore know that we can use this routine for all cleanups (M-, N-, and K-cleanup), and we need only one routine to do so (i.e., we do not have to compile $N_B$ routines to handle all cases). However, it can only be used for M- and N- cleanup cases where the respective dimension is a multiple of 4. Therefore, assuming this kernel is superior to the generated code, it will be used for all K cleanup routines. However, for M and N cleanup, there will be something corresponding to the following pseudocode:

   if (M % 4 == 0) call ATL_mm4x4x2US
   else call generated M cleanup

It is clear that without overloading the flag value to an even more ludicrous degree, that cleanup will eventually need to have it's own index file. For instance, it would be nice to be able to insist that a particular K-cleanup code be used only when $K > 3$, for instance, in addition to insisting it be a multiple of a particular value. The fact that cleanup does not already have such a seperate file simply represents a design failure on my part; it was not until I had already produced the system working as it does now that I saw its shortcomings, and then it was too late to change for the release. Subsequent developer releases will probably address this shortcoming.

Clint Whaley 2012-07-10