ARM Compiler toolchain v4.1 for µVision Using the Compiler

Compiler Coding Practices
5.19 Inline functions
Inline functions offer a trade-off between code size and performance. By default, the compiler
decides for itself whether to inline code or not. As a general rule, when compiling with -Ospace,
the compiler makes sensible decisions about inlining with a view to producing code of minimal
size. This is because code size for embedded systems is of fundamental importance. When
compiling with -Otime, the compiler inlines in most cases, but still avoids large code growth.
In most circumstances, the decision to inline a particular function is best left to the compiler.
However, you can give the compiler a hint that a function is required to be inlined by using the
appropriate inline keyword.
Functions that are qualified with the __inline, inline, or __forceinline keywords are called
inline functions. In C++, member functions that are defined inside a class, struct, or union, are
also inline functions.
The compiler also offers a range of other facilities for modifying its behavior with respect to
inlining. There are several factors you must take into account when deciding whether to use
these facilities, or more generally, whether to inline a function at all.
The linker is able to apply some degree of function inlining to functions that are very short.
5.19.1 See also
Concepts
• Compiler decisions on function inlining on page 5-30
• Restriction on overriding compiler decisions about function inlining on page 5-35
Reference
Compiler Reference:
• --autoinline, --no_autoinline on page 3-14
• __forceinline on page 5-5
• --forceinline on page 3-40
• __inline on page 5-7.
Linker Reference:
• --inline, --no_inline on page 2-64.
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