Re: [Iverilog-devel] Vhpi/vhpi and vhdl

[Jon T. <dos...@gm...>]

Hi Cary,

Sorry, I forgot to answer your first question.  So:

VHDL VHPIDIRECT function call ->
SystemVerilog DPI function call ->
VPP %vpi_call("VHPIDIRECT", "printf", ...) function call ->
VHPI.c VHPIDIRECT(...) function call ->
Linked native object file dlsym() entry point

Something like that?

Jon

On Mon, Jun 22, 2015 at 4:44 PM, Cary R. <cy...@ya...> wrote:
> Would adding functionality for the SystemVerilog DPI functionality be
> enough? Can you give us a quick overview of the VHPI you are hoping to
> translate.
>
> Cary
>
>
>
> On Monday, June 22, 2015 4:08 PM, Jon Taylor <dos...@gm...> wrote:
>
>
> On Mon, Jun 22, 2015 at 12:38 PM, Martin Whitaker
> <mai...@ma...> wrote:
>> Jon Taylor wrote:
>>> Hi all,
>>>
>>> I am the author of Controlix, an operating system written in vhdl. I am
>>> currently developing it using GHDL as the compiler, and the system
>>> interface uses vhpi calls. Works OK on top of POSIX, but Icarus' vpp is
>>> written in c instead of in ada, making a static linkage job for bare
>>> metal
>>> targeting much more feasible.
>>>
>>> Afaics from perusing the sources, neither vhpi or vpp are currently
>>> supported by vhdlpp. If someone is already looking into writing support
>>> for
>>> this, I'd be happy to test, otherwise I might be able to take a crack at
>>> it
>>> myself (I have the coding time available).
>>>
>> Hello Jon,
>>
>> Sorry nobody has replied to you sooner. As far as I know nobody is working
>> on
>> supporting VHPI - hopefully Steve or Orson will chime in if I'm wrong.
>>
>> I'm not familiar with VHPI myself, but at a quick glance it seems very
>> similar
>> to VPI.
>
> Yes, although the full spec is a lot more complex than a simple
> function-binding strategy.
> However, most of the time you don't end up needing to implement the
> full spec - GHDL
> doesn't, all it implements is procedure and function calls.
>
>> This means support would need to be added to the simulator runtime
>> (vvp).
>
> Yes again.  What I am researching now is whether I can piggyback the
> VHPI interface
> on top of the VPI interface in VVP - that is, if %vpi_call() calls can
> be generated by
> vhdlpp from VHPIDIRECT functions and procedures.
>
>> This may not be a big deal in itself, but I suspect the problem you
>> will run into is that vhdlpp is just a preprocessor that converts VHDL to
>> SystemVerilog, so some knowledge of the original code may get lost on the
>> way.
>
> I think that as long as the end product .vpi code contains the
> necessary %vpi_call()s,
> this shouldn't be a problem.  All I will need at that point is a .c
> file to link into
> vpp to map a VHPIDIRECT string to a symbol in the object file.  I think
> libDL can do that.
>
> [snip]
>
>> By vpp, do you mean the VHDL preprocessor?
>
> No, sorry I meant VVP, not vpp. |->
>
>
> Jon
>
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