On Wed, Jun 4, 2008 at 12:33 PM, Chris Lattner <[EMAIL PROTECTED]> wrote: > > Right, I understand that you design "stacks" on LTO. It just seems strange > to work on the advanced stuff before the basic GCC LTO stuff is close to > being useful.
To some degree, we're scratching our own itch here. Basic LTO doesn't help us much. Obviously, though, we want to implement this in a way which is generally useful to the external community. The scalability techniques required to work with distcc are different from the techniques which are useful on a single machine. > I don't know anything about the implementation of the HP or Intel LTO > implementation, but it sounds like there is much room for improvement there. > With LLVM LTO, we see a compile-time slowdown on the order of 30-50% switch > from O3 to O4, not an order of magnitude. There is also still much room for > improvement in the LLVM implementation of course. I think we're working from different baselines. We use distributed techniques for compiling individual .o files. With a tool like distcc, you can get something on the order of 20x speedup. Linking becomes 20% or more of total execution time. LTO *is* an order of magnitude increase compared to a basic link operation. Ollie
