Why is optimizing inline functions easier than normal functions?

user_19627772 0
Viewed 99

Im reading What Every Programmer Should Know About Memory https://people.freebsd.org/~lstewart/articles/cpumemory.pdf and it says that inline functions make your code more optimizable

for example:
Inlining of functions, in particular, allows the compiler to optimize larger chunks of code at a time which, in turn, enables the generation of machine code which better exploits the processor’s pipeline architecture

and:
The handling of both code and data (through dead code elimination or value range propagation, and others) works better when larger parts of the program can be considered as a single unit.

and this also:
If a function is only called once it might as well be inlined. This gives the compiler the opportunity to perform more optimizations (like value range propagation, which might significantly improve the code).

After reading these, to me atleast it seems like inline functions are easier to optimize, but why? Why is it easier to optimize something is inline?

compiler-optimization inline gcc optimization c
1 Answers

The reason that it is easier to make a better job when optimizing inlined functions than with outlined is that you know the complete context in which the function is called and can use this information to tune the generated code to match this exact context. This often allows more efficient code for the inlined copy of the function but also for the calling function. The caller and the callee can be optimized to fit each other in a way that is not possible for outlined functions.

user_36684620
Related