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Philipp A Hartmann

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Posts posted by Philipp A Hartmann


  1. You can check out the example Makefiles in the installation (examples/build-unix/Makefile.{config,rules} and e.g. examples/sysc/simple_bus/Makefile) as a starting point. The files in examples/build-unix are reasonably generic, and you may "just" need to adjust the settings in Makefile.config. In the project's Makefile itself, you then set the PROJECT variable and your SRCS (to point to your source files).  Admittedly, documentation could be better (as usual), but you can ask here, if you have further questions.

    The CMake support included in SystemC 2.3.2 is still experimental and is mostly targeted for early adopters with CMake knowledge.

    Greetings from Duisburg,
      Philipp


  2. Hi Matthias,

    IIRC, KPNs require that inputs are available on all incoming connections for an actor to fire.  In your model, you already consume tokens from some inputs while being then blocked at others.  This can be the reason that you don't see the deadlock in your model.  But of course, you can also have deadlocks under this approach.  Maybe you can trigger it by just switching the order of some of the read statements in your multi-input actors.

    As a general solution, you need to use a similar pattern as recently discussed in the following thread:

     

    Here's an example for one of your processes:

    void kpn::p7() // merge
    {
      static const int f7_n = 1; // number of tokens needed from each input
      static const int f8_n = 1;
      
      while( true )
      {
        while( f7.num_available() < f7_n || f8.num_available() < f8_n ) {
          // at least one side is blocking, wait for activity on either side
          wait( f7.data_written_event() | f8.data_read_event() );
        }
      
        // forwarding possible, process tokens - will not block on inputs
        unsigned int u = f7.read();
        unsigned int v = f8.read();
     
        // ...
        // may still block out outputs
      }
    }

     

    Greetings from Duisburg,
      Philipp


  3. Hi Patrick,

    You can use every Copyable/CopyAssignable type with sc_fifo or tlm_fifo, as entries are always copied in and out of the fifo slots. There is no special support for e.g. move-only types, yet.  It might be a nice to explore options to add such support in order to reduce the cost for passing complex types through fifos.

    So yes, you can pass std::shared_ptr and std::vector, but e.g. not std::unique_ptr.

    Greetings from Duisburg,
      Philipp


  4. The model you describe is not "just" a passthrough model though, as you assume that tokens can be both intercepted (other processes reading from incoming_fifo) and injected (other processes than B writing to outgoing_fifo). From my experience, it is very difficult to design robust models with multiple readers and writers for FIFOs, at least without higher-level synchronization orchestrating the accesses somehow.  That said, let's assume these arbitrary FIFO accesses are needed and OK for your use case.

    I would suggest to indeed use the non-blocking APIs to do the forwarding:

    while( true )
    {
      if( incoming_fifo.num_available() > 0 && outgoing_fifo.num_free() > 0 ) {
        // forwarding possible, process token - will never block
        outgoing_fifo.write( incoming_fifo.read() );
      }
      // at least one side is blocking, wait for activity on either side
      wait( incoming_fifo.data_written_event() | outgoing_fifo.data_read_event() );
    }

    This will not lead to an additional implicit slot in the passthrough block, but the forwarding is "non-greedy" now, i.e. happens only if a slot is available on both sides.  Together with arbitrary other readers/writers on the FIFOs, your passthrough model might never succeed to forward a single token.  See above.

    Minor comment: Your thread_A pseudo code above looks like Java/SystemVerilog and would have a memory leak in C++.  You should not put dynamically allocated objects into a FIFO.

    Hope that helps,
      Philipp


  5. When you use MSVC 2015/2017, did you make sure to use SystemC 2.3.2? Earlier SystemC versions did not support such recent versions of MSVC.

    When you say "regression tests", do you mean the SystemC regression test suite?  If so, please check the accompanying README_windows.txt for any steps you might have missed.

    If this still doesn't help, please post some more details on what exact errors you see.

    Greetings from Duisburg,
      Philipp


  6. Ok, now I understand your concern: It's also about stack-allocated variables in your threads that are not cleaned up at the end of the simulation, as their stacks are not unwound and dynamic process stacks may not even be explicitly deallocated.  I'm not sure, if these cases qualify as real memory leaks, though.

    Small comment: instead of throwing an (non-standard) sc_halt object, you can simply call :

     h.kill(SC_INCLUDE_DESCENDANTS); // also kills all child processes

    There is currently no way to obtain (or kill) all running processes in the simulation, but you can roll your own function to

    • recurse over the object hierarchy via get_child_objects()
    • convert objects to process handles, if valid() and !terminated() call kill(SC_INCLUDE_DESCENDANTS) 

    /Philipp


  7. If you invert the logic and add a function add_initiator to the interconnect, temporarily storing the pointer to the to-be-connected initiator socket (and maybe a name, although this can be derived from the given socket or its parent), you can complete the binding and target socket creation in the interconnect's before_end_of_elaboration hook.  Sockets instantiated in this function will be placed correctly in the hierarchy and this approach is fully standards-compliant.


  8. Starting with SystemC 2.3.2, the MSVC project files shipped with the package use the DLL-based runtime library.  Therefore it is not necessary (instead rather harmful) to select the statically linked runtime library in your application.

    Secondly, you should not set the SC_SIGNAL_WRITE_CHECK environment variable to DISABLE (unrelated to your current issue, but suggested in the video above).

    More instructions on using MSVC with SystemC can be found in the INSTALL file shipped with the proof-of-concept simulator.

    Hope that helps,
      Philipp


  9. As said above, for the TLM-2.0 interconnect case, you can just use multi sockets on don't add additional sockets to the interconnect model at all.

    My question hasn't been on the "surrounding side", but on the usage of the sockets inside the interconnect and the cpu/mem/uart models.  Thes modules actually have to make use of the "injected sockets", which likely requires some additional hacks.  How does the memory handle a second "tgt()" socket during simulation?  How does the CPU suddenly leverage a second initiator?


  10. To me, this approach still looks backwards.

    If you need to finalize things in the model after the configuration is complete (e.g. spawning threads, etc), you can use the before_end_of_elaboration hook.  You can even do the instantiation itself there, if needed, by just storing the pointer to the master and doing both instantiation and process spawning during before_end_of_elaboration.

    Adding emplace_back to sc_vector would just reduce the boilerplate of the delayed instantiation of structural members.  But there are already ways to achieve all of this without any changes to the language.


  11. Quote

    The second version is probably less portable as it includes a file not intended to be included, according to the comments in the file.

    Both versions are non-portable, as the SystemC simcontext is not part of the standard either.  I am even surprised that the hierarchy_push/pop functions are not restricted (as they should be).  So the first solution might in fact break in future versions of SystemC as you shall not mess with the object hierarchy stack yourself.

    Whether or not the "hierarchy scope guard" can be extended to become a standardized solution will likely require some discussions first, especially how to avoid breaking the object hierarchy.  Certainly, this internal hierarchy stack is not  something to arbitrarily use from the model side, other than from the sc_module_name usage today.

    For the particular use case, you can now look into the new "optionally bound convenience sockets" in SystemC 2.3.2, which you can safely leave unbound when not used.  An arbitrary number of sockets can be bound to the multi_passthrough_*_socket, without having to do any such magic above.

    For a generic pattern to request additional structural things to "appear later", you can use an sc_vector with delayed initialization (since SystemC 2.3.2). This is (currently) limited to a single call, but I could envision to extend this to support distributed emplace_back() calls during elaboration.  Such an approach would at least restrict the external modification of the hierarchy to much more controllable contexts.

    Regarding your current use case: How does the destination module actually use these newly added ports/sockets?

    /Philipp


  12. Any eventual copy returned from read() by value will never be optimized away, as the source location continues to exist in the signal.

    The simplest solution is to change your signal converter as follows (untested):

    template <typename Treal, typename Tcasted>
    class signal_interface_converter
       : public sc_core::sc_signal<Treal>
       , public sc_core::sc_signal_in_if<Tcasted> // only read allowed
    {
      typedef sc_core::sc_signal<Treal> real_type;
    public:
      explicit signal_interface_converter(const char* nm)
        : real_type(nm), casted_val() {}
    
      const Tcasted &read() const override {
        return casted_val;
      }
    
    private:
      void update() override {
        real_type::update();
        casted_val = static_cast<Tcasted>(real_type::read());
      ]
    
      Tcasted casted_val;
    };

    So the idea is basically to leverage the update phase to update the casted value. If the above doesn't work due to read() overloads based on the return type only, you may need to wrap it differently to separate the two conflicting interfaces (e.g. by using an internal signal with an overridden update() function, triggering the update of the casted value in the converter).

    Hope that helps,
      Philipp


  13. Two things are to be noted here:

    • IEEE 1666-2011 added support for writer policies, IEEE 1666-2005 required to have conflict detection. So keeping the default behavior was a natural choice back then
    • SC_DEFAULT_WRITER_POLICY is not part of the IEEE Std. 1666-2011, but an extension in the proof-of-concept implementation

    Last but not least, you can always use your own signal template alias:

    template<typename T>
    using sc_signal_mw = sc_core::sc_signal<T, sc_core::SC_MANY_WRITERS>

    Hope that helps,
     Philipp


  14. 11 hours ago, yair said:

    in my case it isnt an Error if we try to write to that register, the initiator can try to do write but the target doesnt have to accept it.
    i think that the right solution would be to add a condition to the b-transport() method

    You would need to describe your actual question in a bit more detail.

    • Is it about the logic inside the target (i.e. not performing the write)?  Sure, you can check the state of the control bit in b_transport before processing the command.
    • Is it about informing the initiator that this happened? Then you need to either use the response status or an extension.

    /Philipp


  15. Hi Avihai,

    I can confirm this behavior with the latest SystemC 2.3.2 pre-release and would classify this as a bug.

    As a short-term workaround, you can mark affected threads with dont_initialize(), which happens not to trigger this misbehavior:

        SC_THREAD(thread1);
        sensitive << thread1_event;
        async_reset_signal_is(reset_in,true);
        dont_initialize(); // avoid crash when starting in reset state

    I'll forward this issue to the Language Working Group for further analysis.

    Greetings from Duisburg,
      Phiipp


  16. Can you please post a complete, self-contained example to demonstrate the issue?  Reading your post, I still cannot infer what actual values, types, ... are involved and not even where you changed the "line" to sc_uint<5>.

    The following code works for me:

    #include <systemc>
    
    int sc_main (int, char *[]) {
    
       using namespace sc_dt;
    
       #define CORE_BUS_WIDTH 5
       #define MASK_WIDTH 32
       {
         sc_uint<CORE_BUS_WIDTH> id;
         sc_uint<MASK_WIDTH>     mask(1 << id);
         std::cout << "id=" << id << "\t- mask=" << mask.to_string(SC_BIN) << std::endl;
       }
       {
         sc_uint<CORE_BUS_WIDTH> id(-1);
         sc_uint<MASK_WIDTH>     mask(1 << id);
         std::cout << "id=" << id << "\t- mask=" << mask.to_string(SC_BIN) << std::endl;
       }
       return 0;
    }

    From your original error message, it looks more like an issue with MASK_WIDTH or CORE_BUS_WIDTH to me.

    Do you see any compiler warnings?

    Hope that helps,
     Philipp


  17. Shifting by zero should of course be supported. Can you provide a self-contained example demonstrating the problem?

    Instead, the error message indicates, that you try to create an sc_uint<-2147483648> (or rather an sc_uint_base with the dynamic width of this value, e.g.), which is not allowed.

    • What's the definition of MASK_WIDTH?
    • What's the definition of ID?

    Hope that helps,
      Philipp


  18. The error message is an indication, that you might miss the /vmg switch in your the MSVC project.

    Quoting from the SystemC INSTALL file (emphasis mine):

    Quote

    Creating SystemC Applications
    -----------------------------

    1. Start Visual Studio. From the Start Page select New Project and Win32
       Console Project. Type the project name and select a suitable location
       then click OK.

    2. Select the Application Settings page of the Win32 Application Wizard
       and make sure the 'Empty project' box is ticked. Click 'Finish' to
       complete the wizard.

    3. Add new/existing C++ files to the project and edit code.

    4. Display the project Property Pages by selecting 'Properties...' from
       the Project menu.

    5. From the C/C++ tab, select the Language properties and set
       'Enable Run-Time Type Info' to Yes

    6. From the C/C++ tab, select the Command Line properties and add /vmg
       to the 'Additional Options:' box.

    7. From the Linker tab, select the Input properties and type 'systemc.lib'
       in the 'Additional Dependencies' box.

    8. Click OK

    (... more information follows)

    Hope that helps,
      Philipp

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