Would it make sense to use __attribute__ ((noinline)) for functions like _M_realloc_insert?

[Groke, Paul]

Hi,

I've recently noticed that GCC is inlining vector::_M_realloc_insert into some of my functions that call vector::emplace_back. IMO that doesn't make a lot of sense - reallocation is usually so expensive that an extra function call doesn't really matter. And it bloats the code, which has two drawbacks: the binary gets bigger and the fast path gets slower (less efficient pre-fetching/more cache thrashing).

What do you think about marking such functions __attribute__ ((noinline))?

In our own code, we've seen measurable improvements (size & execution speed) by splitting the "slow path" out into helper functions and making those helper functions noinline.

(I've also noticed that there's no __builtin_expect for the fast path, but that's a different topic and IMO far less important.)

Regards,
Paul Groke

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