Re: Profiling compilation time

[Yang Zhang <yanghatespam at gmail dot com>]

Ian Lance Taylor wrote:
> Yang Zhang <yanghatespam@gmail.com> writes:
>
> > Ian Lance Taylor wrote:
> > > Use the -ftime-report option.
> > Neat!  Is there something similar for breaking down the time into time
> > spent on individual files so that I can see which #included files are
> > the most costly?  (If you treat the compiler as a template language
> > interpreter then you can even imagine getting call-graph profiling
> > results.)
>
> That's a good idea.  Unfortunately, I don't think there is anything like
> that at present.  It would be hard, and perhaps meaningless, to do that
> for the IPA passes, but it could be done for the frontends and for the
> general optimization passes (where I suppose the time for inlined
> functions would go the function into which they are inlined.)
>
> Ian

For me, -ftime-report shows that compilation time is by far dominated by 
parsing, so that's what I'm most interested in.  To that end, would a 
valid poor man's profiling approach be to simply measure the time of 
#including individual files into an otherwise empty source file?  Or 
would it be necessary to actually "trigger" the parsing somehow by using 
the headers' contents (particularly for templated entities)?
--
Yang Zhang
http://www.mit.edu/~y_z/