On 10/09/13 10:11, Jakub Jelinek wrote: > On Tue, Sep 10, 2013 at 10:06:04AM +0200, David Brown wrote: >> This last point is crucial. I haven't looked at the code in question, >> but one point to check is how the functions are called. If they are >> often called with constant values, then they may be very much simplified >> due to constant propagation. Secondly, if a function is inlined, the >> compiler has full knowledge of the effects of the function "call" and >> can thus optimise better (keeping data in registers over the "call", >> shuffling around loads and stores, etc.). Finally, if the functions are >> called in loops or other time-critical code, it can be worth spending >> more code section space for a faster result (but sometimes smaller code >> is faster due to caches, branch prediction buffers, etc.). >> >> The ideal situation is that LTO figures this out for you, and the code > > At least until LTO keeps to end up with unusable or hardly usable debug > info, effectively requiring LTO for good compiler performance is a > non-starter. And, the inliner we have is not dumb, if it sees an inline > function, but it is too large, it will usually not inline it. > So, rather than counting the lines of inline functions in headers, IMHO it > is better to look at inliner's decisions about those functions, if it > never inlines them, then supposedly moving them out of line is reasonable. > > Jakub >
That should be easy enough with "-Winline", I think. David
