rfc: -mmemory-latency=

[Richard Henderson]

I was thinking the other day that, especially on Alpha, memory
scheduling can vary widely for an application. 

It would be ideal if GCC knew about caches itself and locality,
and whether it is likely a particular cache line is resident, and 
when it might be profitable to do prefetching, etc.

But for now, as a tuning parameter to play around with, here is 
a switch that allows the user to change the scheduling parameters.
If there are no objections, I'll check it in to the mainline.


r~