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I've seen gcc do an enthusiastic job on `static` functions within a C compilation unit - specifically where they only have one call site and so can be fully inl

I've seen gcc do an enthusiastic job on `static` functions within a C compilation unit - specifically where they only have one call site and so can be fully inlined into the caller. In that case, the code did become pretty hard to debug due to the extensive inlining and reordering it had allowed. Unfortunate because the only reason such functions exist is to make the structure of the code more apparent! Maybe that's an exception (and / or maybe it's easier with C than for C++). Maybe the less is that it's still always worth trying function call boundaries, in case the compiler has been conservative!

account42 2y ago
Yes, inlining is one exception. Function variants for constant propagation are another. But both of those have been around for a long time and if neither of them apply compilers won't even reorder arguments where that makes sense or deviate from the platform calling convention based on register pressure inside the functions or drop unused arguments or reorder arguments if that improves things. Feels like in general internal function boundaries in the code should be just a hint to and optimizing compiler but somehow there has been very little development in that area. Similar for struct/class layout, compilers won't touch that even if they can see all uses.