Target Language Compiler

Fully Inlined S-Function Example

Inlining an S-function provides a mechanism to directly embed code for an S-function block into the generated code for a model. Instead of calling into a separate source file via function pointers and maintaining a separate data structure (SimStruct) for it, the code appears "inlined" as the diagram below shows.

The S-function timestwo.c provides a simple example of a fully inlined S-function. This block multiplies its input by 2 and outputs it. The C-MEX version of the block is in matlabroot/simulink/src/timestwo.c and the inlining TLC file for the block is in matlabroot/toolbox/simulink/blocks/tlc_c/timestwo.tlc.

timestwo.tlc

• %implements "timestwo" "C"
  
  %% Function: Outputs ==========================================
  %%
  %function Outputs(block, system) Output
    /* %<Type> Block: %<Name> */
    %%
    /* Multiply input by two */
    %assign rollVars = ["U", "Y"]
    %roll idx = RollRegions, lcv = RollThreshold, block, "Roller", rollVars
      %<LibBlockOutputSignal(0, "", lcv, idx)> = \
      %<LibBlockInputSignal(0, "", lcv, idx)> * 2.0;
    %endroll
  %endfunction
  

TLC Block Analysis

The %implements line is required by all TLC blocks file and is used by the Target Language Compiler to verify correct block type and correct language support by the block. The %function directive starts a function declaration and shows the name of the function, Outputs, and the arguments passed to it, block and system. These are the relevant records from the model.rtw file for this instance of the block.

The last piece to the prototype is Output. This means that any line that is not a TLC directive is output by the function to the current file that is selected in TLC. So, any nondirective lines in the Outputs function become generated code for the block.

The most complicated piece of this TLC block example is the %roll directive. TLC uses this directive to provide for the automatic generation of for loops depending on input/output widths and whether the inputs are contiguous in memory. This example uses the typical form of accessing outputs and inputs from within the body of the roll, using LibBlockOutputSignal and LibBlockInputSignal to access the outputs and inputs and perform the multiplication and assignment. Note that this TLC file supports any signal width.

The only function needed to implement this block is Outputs. For more complicated blocks, other functions will be declared as well. You can find examples of more complicated inlining TLC files in matlabroot/toolbox/simulink/blocks and matlabroot/toolbox/simulink/blocks/tlc_c, and by looking at the code for built-in blocks in matlabroot/rtw/c/tlc/blocks.

timestwo Model

This simple model uses the timestwo S-function and shows the MdlOutputs function from the generated model.c file, which contains the inlined S-function code.

MdlOutputs Code

• void MdlOutputs(int_T tid)
  {
    /* S-Function Block: <Root>/S-Function */
    /* Multiply input by two */
    rtB.S_Function = (rtB.Constant_Value) * 2.0;
  
    /* Outport Block: <Root>/Out1 */
    rtY.Out1 = rtB.S_Function;
  }
  

Inlining S-Function Concepts

Wrapper Inlined S-Function Example