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Unused function code can unnecessarily increase code size. Feedback from the linker to the compiler can remove unused function code, minimizing code size.
Unused function code might occur in the following situations.
Where you have legacy functions that are no longer used in your source code. Rather than manually remove the unused function code from your source code, you can use linker feedback to remove the unused object code automatically from the final image.
Where a function is inlined. Where an inlined function
is not declared as
static, the out-of-line function
code is still present in the object file, but there is no longer
a call to that code.
In addition, the linker can detect when an ARM function is being called from a Thumb state, and when a Thumb function is being called from an ARM state. You can use feedback from the linker to avoid compiling functions for interworking that are never used in an interworking context.
Reduction of compilation required for interworking is only applicable to ARMv4T architectures. ARMv5T and later processors can interwork without penalty.
The linker option
--feedback=filename creates a feedback file, and the
--feeback_type option controls the different types of feedback generated.