Hi Ryan
So I just finished a ROACH2 build, and everything from "copy base
package" through bitgen took almost 2 hours. It looks like this is
because I have 48 "shared memories", plus about another 20
"snapshots". The tools seem to be synthesizing each of these
separately.
I would expect that many designs have several yellow blocks which are
instantiated multiple times with identical parameters. I don't have a
strong background in the CASPER toolflow, but does anyone know if
there's a way for us to cache synthesis products of identical yellow
blocks?
As far as I know Dave (M) uses black-boxing for doing this with some
parts of the DSP design (i.e not necessarily yellow blocks). He also
implemented some logic recently to cache and reuse Shared BRAM coregen
products (as these also take a while to generate).
I have mentioned this idea before to Dave but I think that it would be
possible to take this idea a lot further. The toolflow could automate
this quite easily. Basically, at compile time do the following;
1. For every 'large' CASPER DSP/yellow block
a. check that we don't already have the synthesis products for this
block in our database, if so skip to 2.
b. make a new design and copy it across, joining input ports to
Getway Ins and outputs to Gateway outs
c. synthesise the resultant design with System Generator
2. Create a copy of the original full design and replace each 'large'
block with a black box
3. Synthesise the modified full design
4. Have the toolflow copy the required output products from the small
component block compiles into the appropriate place and join everything
up (much like we already do with the yellow blocks)
5. On subsequent compiles, check the 'large' blocks for changes (hash
the parameter inputs and maybe some other things) and only re-synthesise
those blocks that have changed.
6. Logic could also be added to build up a local database of compiled
blocks that could be queried when a compile of a design occurs
It would be a reasonable amount of work to implement, but would save a
lot of time for people who compile the same design often.
Regards
Andrew
