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Robert.g.Liu

SV-DPI and co-routine

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I have seen several SV-DPI and pthread related posts in this forum and in stackoverflow. However, it seems no post for SV-DPI and co-routine. I guess the reason is there is NO standard library or C language native support for co-routine ( except C++20).

Now I'm trying several C based co-routine libraries mentioned in https://en.wikipedia.org/wiki/Coroutine to support python/javascript type of generator in Systemverilog/UVM testbench.

Here is how. 

1. One SV thread is working as main thread. A SV function will be working as a co-routine and exported to DPI.

2. The SV thread need to create a co-routine by calling co_create through the DPI. the first argument of the co_create would be a wrapper function to the SV exported function.  And co_create will use a dynamically allocated array as standalone stack for the co-routine being created. 

3. Then SV thread need to resume the co-routine by calling co_resume through the DPI. Here, stack pointer of the CPU will switch to the new stack of the co-routine and entry point is the wrapper function.  And finally, the execution will go to the SV exported function and go back to SV side.

4. In the middle of the SV exported function, co_yield will be called. stack pointer will be switched back to the main thread and program counter will be returned to right after the co_resume. Finally, execution will return back to the SV side of the main thread. 

5. Above step 3-4 can be repeated many times until the exported function is finished and co-routine can be destroyed.

I don't know how much stack space is needed to run SV functions on it. I just allocated 32KB for each co-routine.

That's all. This is completely single threaded with user space cooperative multiple tasking. Again, this is to mimic the python/javascript type of generator for test framework development.

Is there any risk ?

 

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