Application of C++ inline functions in embedded systems

In embedded systems, inline functions optimize performance in the following ways: Reduce function call overhead: Inline functions directly replace the function body at the call point, eliminating the overhead of function calls. Improved performance: For small and frequently called functions, inlining can significantly improve performance. Reduced code size: Inline functions do not add extra code size like external functions.

Application of C inline functions in embedded systems

Introduction

Inline function is a special function in C. The compiler will directly replace its function body at the call point. This eliminates the overhead of function calls and improves performance in some cases. In embedded systems, performance is critical, so understanding intrinsics can help developers optimize their applications.

Syntax

Inline functions are declared by using the inline keyword before the function definition:

inline int square(int x) {
  return x * x;
}

Advantages

• Reduce function call overhead: Inline functions do not call functions, but insert the function body directly into the call point, thus eliminating the need for function calls. overhead.
• Improve performance: For small functions that are called frequently, inlining can significantly improve performance.
• Reduce code size: Inline functions do not add extra code size compared to external functions.

Practical case

Consider the following function to calculate distance in an embedded system:

int compute_distance(int x1, int y1, int x2, int y2) {
  int dx = x2 - x1;
  int dy = y2 - y1;
  return sqrt(dx * dx + dy * dy);
}

By converting compute_distance By declaring the function as inline, we can minimize the code size and overhead of calling the function:

inline int compute_distance(int x1, int y1, int x2, int y2) {
  int dx = x2 - x1;
  int dy = y2 - y1;
  return sqrt(dx * dx + dy * dy);
}

Notes

• Compilation time : Inline functions are expanded at compile time, so may increase compilation time.
• Execution limitations: For functions that are highly recursive or have a large number of local variables, inlining may not be suitable.
• Other optimizations: Inlining is not the only way to optimize your code. Consider using const functions and using compiler flags for additional optimizations.

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