[llvm-dev] RPC on LLVM IR: any example programs for this?

[Shen Liu via llvm-dev]

Thank you for your helpful answer, Lang! I will try it.

On Wed, Apr 19, 2017 at 5:57 PM, Lang Hames via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hi Shen,
>
> Let's say we have two modules M1.bc and M2.bc, and in M1 we want to call
>> function foo(defined in M2.bc)with the function type
>>
>
>
> int foo(float, char*){...}
>>
>
>
> what basic steps do I need to do to make M1.bc call foo remotely?
>
>
> There's currently no built in support for calling functions with
> signatures other than void(), int(), or int(int, char*[]).
>
> To call a function with a different signature you have a couple of options:
>
> (1) Generate a wrapper, encode the args, then decode the return:
>
> void wrapper(void *inputs, void *output) {
>   // args = decode(inputs)
>   int result = foo(args...);
>   // output = encode(result)
> }
>
> Then on the client end you have to write data to the inputs slab, send it
> to the server, call wrapper, read the outputs slab back, then decode it.
>
> (2) If you know the signature of the function that you want to be able to
> call ahead of time, you can extend the JIT server's RPC endpoint to handle
> your function type. (We would just need to make the RPC endpoint in
> OrcRemoteTargetServer publicly visible for this to work, but that's an easy
> change):
>
> // Declare your function pointer type.
> typedef int (*MyFuncType)(float, char*);
>
> // Write a handler to call into a function of your type.
> int callMyFunc(JITTargetAddress MyFuncAddr, float Arg1, std::string Arg2) {
>   MyFuncType MyFunc = (MyFuncType)MyFuncAddr;
>   return MyFunc(Arg1, Arg2.c_str());
> }
>
> // Write an RPC function definition.
> class CallMyFunc : public llvm::orc::rpc::Function<CallMyFunc,
> int(JITTargetAddress, float, std::string)> {
> public:
>   static const char *getName() { return "CallMyFunc"; }
> };
>
> // Register the callMyFunc function as a handler for CallMyFunc (the RPC
> definition) with the RPC endpoint.
> OrcRemoteTargetServer Server(...);
> Server.getRPCEndpoint().addHandler<CallMyFunc>(callMyFunc);
>
> Now on your client you could write:
>
> int Result = Client.getRPCEndpoint.callB<CallMyFunc>(3.141, "pi");
>
> (3) If you don't know the signature of the function at server build type,
> you can write the code from part (2) and JIT it into the server after you
> connect. This would require us extending the OrcRemoteTargetRPC API with a
> "RegisterRPCExtension" function, but that should also be pretty easy.
>
> BTW, does the RPCUtility supports handling pointers now?
>
>
> It does not, and I doubt it ever will - I expect it to remain limited to
> value types only.
>
> The aim of Orc RPC is to be good enough for basic cases, and especially
> for testing purposes, but we don't want it growing into a fully featured
> RPC library. That kind of use case would be better supported by writing a
> new client/server (out of tree) on top of a fully featured RPC library like
> GRPC or Cap'n Proto.
>
> Cheers,
> Lang.
>
> On Tue, Apr 18, 2017 at 6:04 PM, Shen Liu <sxl463 at cse.psu.edu> wrote:
>
>> Hi Lang,
>>
>> Thanks for your reply! It seems that the code of ORC has been changed a
>> lot these months. Actually what I wanted to see then was quite simple,
>> Let's say we have two modules M1.bc and M2.bc, and in M1 we want to call
>> function foo(defined in M2.bc)with the function type
>>
>> int foo(float, char*){...}
>>
>> what basic steps do I need to do to make M1.bc call foo remotely?
>>
>> BTW, does the RPCUtility supports handling pointers now?
>>
>> Thanks very much!
>>
>> Best regards,
>>
>> Shen
>>
>> On Thu, Apr 13, 2017 at 9:13 PM, Lang Hames via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Hi Shen,
>>>
>>> The best place to look for examples is currently the RPCUtilsTest unit
>>> test: llvm/unittests/ExecutionEngine/Orc/RPCUtilsTest.cpp
>>>
>>> What API do you want to be able to call via RPC? If it's small I can
>>> probably write up an example for you.
>>>
>>> Cheers,
>>> Lang.
>>>
>>>
>>>
>>> On Fri, Dec 16, 2016 at 7:37 AM, Shen Liu via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> Hi everyone,
>>>>
>>>> I want to use an LLVM new feature (llvm::orc::remote::RPCBase) to
>>>> implement a simple RPC framework between two LLVM modules. It seems by
>>>> this new class we can do serialization/deserialization on LLVM IR type
>>>> system directly. But I haven't found any helpful stuff on google showing me
>>>> how to use these RPC APIs. Can anyone give me some hints or example
>>>> programs showing me how to use these API correctly? Just a simple
>>>> serialization/deserialization toy demo is OK, Thanks very much!
>>>>
>>>> Best regards,
>>>>
>>>> Shen
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>
>>>>
>>>
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>>>
>>
>
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