On Wed, 5 Jun 2024 02:52:29 +0200 Andrew Lunn <andrew@xxxxxxx> wrote: > > How is a compiler going to know that? > > It might have some heuristics to try to guess unlikely/likely, but > that is not what we are talking about here. > > How much difference did 'always_inline' and 'noinline' make? Hopefully > the likely is enough of a clue it should prefer to inline whatever is > in that branch, where as for the unlikely case it can do a function > call. Perhaps, but one of the issues was that I have lots of small functions that are used all over the place, and gcc tends to change them to function calls, instead of duplicating them. I did this analysis back in 2016, so maybe it became better. > > But compilers is not my thing, which is why i would reach out to the > compiler people and ask them, is it expected to get this wrong, could > it be made better? Well, I actually do work with the compiler folks, and we are actually trying to get a session at GNU Cauldron where Linux kernel folks can talk with the gcc compiler folks. I've stared at so many objdump outputs, that I can now pretty much see the assembly that my C code makes ;-) -- Steve
