LLVM is a shit compiler

It's worse than GCC 4.5 in terms of speed, and that says A LOT

--enable-optimized
    Enables optimized compilation (debugging symbols are removed and GCC optimization flags are enabled).
    Note that this is the default setting if you are using the LLVM distribution. The default behavior of an
    Subversion checkout is to use an unoptimized build (also known as a debug build).