register windows

Has anybody tried modifying a Sparc compiler to just use 32
registers (i.e. 1 window) rather than using all windows?


If so, what were the results?


The reason I'm interested is that saving a register window takes about 5
microseconds and it happens 2-4 times while handling an interrupt. We've
already removed as many window overflows as we can so modifying the
interrupt handler is no longer an option (or it's an option we are no
longer considering.)


I realize a lot of registers will still have to be saved, but we would
no longer trap into the window_overflow handler and we may not have to save
as many registers.


I'd like to hear any results/comments about 32 globals vs. 7 windows,
not just results relative to my interrupt speed.


Also I'll probably try this with gcc. Any advice about that? Has anybody
done that?


Thanks,
Fred (flc@cs.cmu.edu)

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