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Control inlining of a specific function in generated code



coder.inline('always') forces inlining of the current function in the generated code. Place the coder.inline directive inside the function that you want to inline. The code generator does not inline entry-point functions and recursive functions. Also, the code generator does not inline functions into parfor loops, or inline functions called from parfor loops.


coder.inline('never') prevents inlining of the current function in the generated code. Prevent inlining when you want to simplify the mapping between the MATLAB® source code and the generated code.


If you use the codegen or the fiaccel (Fixed-Point Designer) command, you can disable inlining for all functions by using the -O disable:inline option.

If you generate C/C++ code by using the codegen command or the MATLAB Coder™ app, you might have different speed and readability requirements for the code generated for functions that you write and the code generated for MathWorks® functions. Certain additional global settings enable you to separately control the inlining behavior for these two parts of the generated code base and at the boundary between them. See Control Inlining to Fine-Tune Performance and Readability of Generated Code.

In cases where the code generator does not prevent inlining of a function in the generated code even if it contains the coder.inline('never') directive, use the coder.ignoreConst function on an input at the function call site in your MATLAB code. For more information, see Resolve Issue: coder.inline('never') Does Not Prevent Inlining of Function.

coder.inline('default') instructs the code generator to use internal heuristics to determine whether to inline the current function. Usually, the heuristics produce highly optimized code. Use coder.inline explicitly in your MATLAB functions only when you need to fine-tune these optimizations.


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In this example, function foo is not inlined in the generated code:

function y = foo(x)
  y = x;

You can use coder.inline in control flow code. If the software detects contradictory coder.inline directives, the generated code uses the default inlining heuristic and issues a warning.

Suppose that you want to generate code for a division function that runs on a system with limited memory. To optimize memory use in the generated code, the inline_division function manually controls inlining based on whether it performs scalar division or vector division:

function y = inline_division(dividend, divisor)

% For scalar division, inlining produces smaller code
% than the function call itself.  
if isscalar(dividend) && isscalar(divisor)
% Vector division produces a for-loop.
% Prohibit inlining to reduce code size.

if any(divisor == 0)
   error('Cannot divide by 0');

y = dividend / divisor;

More About

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Technique that replaces a function call with the contents (body) of that function. Inlining eliminates the overhead of a function call, but can produce larger C/C++ code. Inlining can create opportunities for further optimization of the generated C/C++ code.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Version History

Introduced in R2011a