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Re: [patch][rfa] Don't Generate Code to Support Unused Write Stacks


Frank Ch. Eigler wrote:

brolley wrote:



[...]
When generating write stacks and the supporting code in order to
suppor the (delay ...) rtl construct for SID, cgen currently generates
a write stack for all registers and memory modes regardless of whether
they are used or not. [...]
For the internal port for which performance was an issue, this yielded
an improvement of 17%. [...]



Sounds good. I'm surprised though that your change should cause such
a noticeable improvement. It may be that the sid-side code to handle
the write queue testing/iteration is rather deficient. (Try adding
some UNLIKELY markers to the CPU::writeback() function's while()
conditions.)


I think that the difference was 39 vs 2 write stacks to manage for this port.

Dave


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