Where does the time go?

[Joseph S. Myers]

On Thu, 20 May 2010, Steven Bosscher wrote:

> * The C front end (preprocessing+lexing+parsing) costs ~17%. For an
> optimizing compiler with so many passes, this is quite a lot.

Unlike C++ where a lot of speedups were done around 2004-5, I don't think 
much has been done about speeding up the C front end outside the 
preprocessor, so there are likely to be lots of opportunities available 
(there are probably still a fair number for C++ as well).

Preprocessor (including preprocessed output) speed is of relevance for use 
with tools such as distcc, and whole-compilation speed is of obvious 
relevance for general use of the compiler.  Front-end-only speed 
(-fsyntax-only, approximately) is less important on its own as that's not 
a normal compiler use (I think) - it's only relevant as a contribution to 
the speed of a whole compilation.

-- 
Joseph S. Myers
joseph@codesourcery.com