[cfe-dev] Clang on Windows targteing gcc compiles very slowly

[Edward Diener]

I test Boost libraries mostly on Windows using various version of gcc 
4.3 and up, VC++ 8.0 and up, and the latest version of clang which I 
build from source using mingw/gcc-4.8.1 in release mode.

While clang is a great compiler when it comes to testing code, getting 
intelligent error message, and implementing the latest C++ standard, it 
is noticably slower ( 2x or 3x at minimum ) than the other compilers I use.

The clang command line parameters usually being used are usually along 
the lines of:

-c -x c++ -O0 -g -fno-inline -Wall -g -march=i686 -m32

with the addition of 'std=c++11' occasionally depending on the test.

Does anybody have any idea why clang is so much slower than any of the 
other compilers I use ? It does not seem to matter whether it is in 
C++03 mode or C++11 mode, it is noticeably slower than the other compilers.