I noticed that Google's C++ style guide cautions against inlining functions with loops or switch statements:
Another useful rule of thumb: it's typically not cost effective to inline functions with loops or switch statements (unless, in the common case, the loop or switch statement is never executed).
Other comments on StackOverflow have reiterated this sentiment.
Why are functions with loops or switch statements (or gotos) not suitable for or compatible with inlining. Does this apply to functions that contain any type of jump? Does it apply to functions with if statements? Also (and this might be somewhat unrelated), why is inlining functions that return a value discouraged?
I am particularly interested in this question because I am working with a segment of performance-sensitive code. I noticed that after inlining a function that contains a series of if statements, performance degrades pretty significantly. I'm using GNU Make 3.81, if that's relevant.
Inlining functions with conditional branches makes it more difficult for the CPU to accurately predict the branch statements, since each instance of the branch is independent.
If there are several branch statements, successful branch prediction saves a lot more cycles than the cost of calling the function.
Similar logic applies to unrolling loops with switch statements.
The Google guide referenced doesn't mention anything about functions returning values, so I'm assuming that reference is elsewhere, and requires a different question with an explicit citation.