Is there any difference when compilers implements C inline function in different platforms

Question

I was told that the implementation for C inline functions in different platforms (e.g. Mips vs x86) is a little different. For example, inline function for one of them (Mips or x86) still allocates stack and thus not so efficient. Is it true? What are all the difference? Thanks

Answer 1

It is not guaranteed that every function will be inlined when you declare it inline (it is just a suggestion to the compiler). Hence for any architecture the functions that aren't inlined will be treated as normal functions, and hence the push & pop from the stack when you call them (like any normal non-inlined function)

And it is pretty much dependent upon how your compiler is configured. For eg, GCC has flags like:

-finline-functions
Consider all functions for inlining, even if they are not declared inline. The compiler heuristically decides which functions are worth integrating in this way.

-finline-limit=n
By default, GCC limits the size of functions that can be inlined. This flag allows coarse control of this limit. n is the size of functions that can be inlined in number of pseudo instructions.

--param name=value
In some places, GCC uses various constants to control the amount of optimization that is done. For example, GCC does not inline functions that contain more than a certain number of instructions. You can control some of these constants on the command line using the --param option.