Re: Using C++ in GCC is OK

[Joern Rennecke <amylaar at spamcop dot net>]

Quoting Vladimir Makarov <vmakarov@redhat.com>:
> Reviewers are frequently busy.  I bet not a lot of reviewers apply
> patches and play with it.
>
> So it would be nice that people who submits such patches report changes
> in compile time/footprint/build time (at least I am going to ask this
> for parts which I review even if such changes in these parts will be
> not critical for whole compiler as tree or rtl infrastructure changes).
>  Otherwise, we are in danger to get slowly degrading compiler.

I'm not sure that this will be effective against bloat creep.  When
considering one small patch that slows down the compiler (and/or slows down
build time) by 0.1%, the difference will be in the noise and impossible to
measure with a manageable sample size.
But if you combine 1100 of such small patches, the compiler will be three
times slower.

So, unless we can get some coding style/review mechanism in place that  
prevents
such bloat creep by examining the source code change and the area where it is
applied, I think we would need a way to magnify the performance impact
of abstraction penalties.  E.g. if the penalty is a vtable lookup, making
it take a hundred times more specifically in the changed places would
magnify the 0.1% overall change to a measurable delta of 10%.