[webkit-dev] Compiling WebKit up to 25% faster in Windows?

[Daniel Bratell]

Hi WebKittens,

As you might be aware, we at Opera now have Chromium based products which  
means that we compile WebKit quite a lot. A big issue for us and our  
automatic systems has been the long time needed to compile WebKit (inside  
Chromium), especially in Windows.

The big compilation time difference between Linux and Windows didn't seem  
to make sense so we did some analysis of what was going on and we think  
that we have found a cause. In WebKit include directives are without path,  
and instead the compiler is given a very long list of directories to  
search through. That process takes a lot of time in Windows. It must take  
some time in OSX and in Linux too but probably less.

As an experiment we took the (chromium) project webcore_dom, that normally  
compiles in 56 seconds in Windows on a generic computer and "fixed" it.  
Removing the many include paths in the build system and instead specifying  
the path in the include directives changed that to 42 seconds, a 25%  
reduction.

There is no reason to think the same reduction doesn't apply to all  
projects and then there are many many minutes to save for developers and  
build servers here.

Caveat: I don't know if the resulting binary is correct.

Is this something that has been talked about in the past, and would you be  
interested in replacing the long list of directories to search for every  
include with paths (relative some good base) directly in the include  
directives?

/Daniel