[libre-riscv-dev] [Bug 325] create POWER9 TRAP pipeline

[bugzilla-daemon@libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=325

--- Comment #72 from Cole Poirier <colepoirier@gmail.com> ---
(In reply to Luke Kenneth Casson Leighton from comment #67)
> in the libreriscv submodule first to "git pull origin master" - watch out
> because submodules are a pain - then you can generate the emulator code.
> 
> run pywriter.py (see top-level Makefile).  then - and only then - will
> the simulator "understand" mtmsr.
> 
> you can inspect the results by looking at... errr... what did we say
> it was added to?  sprset.mdwn?
> 
> so... pywriter.py will.. err.. put that into... 1sec....
> soc/decoder/isa/sprset.py
> 
> [btw do *NOT* "git add" that to the repository (it's auto-generated.  we
>  do *NOT* add auto-generated files to the git repository, because they
>  change).]
> 
> example:  mcrxrx, from the sprset.mdwn file
> 
> * mcrxrx BF
> 
>     CR[4*BF+32:4*BF+35] <-  XER[OV] || XER[OV32] || XER[CA] || XER[CA32]
> 
> ---> is translated to, in sprset.py --->
> 
>     @inject()
>     def op_mcrxrx(self, CR):
>         CR[4 * BF + 32:4 * BF + 35 + 1] = concat(XER[OV], XER[OV32],
> XER[CA], XER[CA32]
>             )
>         return (CR,)
> 
> 
> at that point, you *should* be able to add something to
> soc/fu/trap/test/test_pipe_caller.py in class TrapTestCase
> 
> which i see you deleted all the unit tests (i usually leave one
> in there on cookie-cutting so that it's less typing when it comes
> to creating one.  now you will have to re-open one of the
> test_pipe_caller.py files to cut/paste an example from.  this is
> more work for you)
> 
> 
> here's the thing: it is highly likely that op_trap() from sprset.py
> will fail.  this because it's literally the first time that the emulator
> has ever seen the "trap" instruction, and that code also has to be written.
> 
> do not let this stop you from actually writing the unit test!
> 
> the unit test *is* the way to highlight that the code needs to be written!
> [this is called test-driven development]
> https://en.wikipedia.org/wiki/Test-driven_development

I'm having a difficult time understanding how to write the first test for class
TrapTestCase looking both at cr/test/test_pipe_caller and
logical/test/test_pipe_caller... Do I have to translate all the code that was
set up for CR into setting up for TRAP? Trying to think through it I can't
figure it out, and I suspect it is related to my previous comment about not
understanding how the test_pipe_caller, XXXInput/OutputData, CompALUOpSubset,
and CompTrapOpSubset, and the decoder, relate to and interact with each
other... I have a little idea of each but I'm doing the 'freeze cause I don't
understand' right now.

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