Main Content

Remap Operator Output to Function Input

If your generated code must meet a specific coding pattern or you want more flexibility, for example, to further improve performance, you can remap operator outputs to input positions in an implementation function argument list.


Remapping outputs to implementation function inputs is supported only for operator replacement.

For example, for a sum operation, the code generator produces code similar to:

add8_Y.Out1 = u8_add_u8_u8(add8_U.In1, add8_U.In2);

If you remap the output to the first input, the code generator produces code similar to:

u8_add_u8_u8(&add8_Y.Out1;, add8_U.In1, add8_U.In2);

The following table definition file for a sum operation remaps operator output y1 as the first function input argument.

  1. Create a table definition file that contains a function definition. For example:

    function hTable = crl_table_add_uint8
  2. Within the function body, create the table by calling the function RTW.TflTable.

    hTable = RTW.TflTable;
  3. Create an entry for the operator mapping with a call to the RTW.TflCOperationEntry function.

    % Create operation entry 
    op_entry = RTW.TflCOperationEntry;
  4. Set operator entry parameters with a call to the setTflCOperationEntryParameters function. In the function call, set the property SideEffects to true.

    setTflCOperationEntryParameters(op_entry, ...
                        'Key',                      'RTW_OP_ADD', ...
                        'Priority',                 90, ...
                        'ImplementationName',       'u8_add_u8_u8', ...
                        'ImplementationHeaderFile', 'u8_add_u8_u8.h', ...
                        'ImplementationSourceFile', 'u8_add_u8_u8.c', ...
                        'SideEffects',              true );
  5. Create conceptual arguments y1, u1, and u2. There are multiple ways to set up the conceptual arguments. This example uses calls to the getTflArgFromString and addConceptualArg functions to create and add the arguments.

    arg = getTflArgFromString(hTable, 'y1', 'uint8');
    arg.IOType = 'RTW_IO_OUTPUT';
    addConceptualArg(op_entry, arg);
    arg = getTflArgFromString(hTable, 'u1', 'uint8');
    addConceptualArg(op_entry, arg );
    arg = getTflArgFromString(hTable, 'u2', 'uint8');
    addConceptualArg(op_entry, arg );
  6. Create the implementation arguments. There are multiple ways to set up the implementation arguments. This example uses calls to the getTflArgFromString function to create the arguments. When defining the implementation function return argument, create a new void output argument, for example, y2. When defining the implementation function argument for the conceptual output argument (y1), set the operator output argument as an additional input argument. Mark its IOType as output. Make its type a pointer type. The convenience methods setReturn and addArgument specify whether an argument is a return value or argument and adds the argument to the entry’s array of implementation arguments.

    % Create new void output y2
    arg = getTflArgFromString(hTable, 'y2', 'void');
    arg.IOType = 'RTW_IO_OUTPUT';
    % Set y1 as first input arg, mark IOType as output, and use pointer type
    arg=getTflArgFromString(hTable, 'y1', 'uint8*');
    arg.IOType = 'RTW_IO_OUTPUT';
    arg=getTflArgFromString(hTable, 'u1', 'uint8');
    arg=getTflArgFromString(hTable, 'u2', 'uint8');
  7. Add the entry to a code replacement table with a call to the addEntry function.

    addEntry(hTable, op_entry);
  8. Save the table definition file. Use the name of the table definition function to name the file.

To test this example:

  1. Register the code replacement mapping.

  2. Create a model that includes an Add block.

  3. Configure the model with the following settings:

    • On the Solver pane, select a fixed-step solver.

    • On the Code Generation pane, select an ERT-based system target file.

    • On the Code Generation > Interface pane, select the code replacement library that contains your addition operation entry.

    • Set the Optimize global data access parameter to Use global to hold temporary results to reduce data copies in the generated code.

  4. Generate code and a code generation report.

  5. Review the code replacements.

Related Topics