On Mon, 19 Jan 2009, Nick Piggin wrote: > > I want to know what is the problem with the restrict keyword? > I'm sure I've read Linus ranting about how bad it is in the > past... No, I don't think I've ranted about 'restrict'. I think it's a reasonable solution for performance-critical code, and unlike the whole type-aliasing model, it actually works for the _sane_ cases (ie doing some operation over two arrays of the same type, and letting the compiler know that it can access the arrays without fearing that writing to one would affect reading from the other). The problem with 'restrict' is that almost nobody uses it, and it does obviously require programmer input rather than the compiler doing it automatically. But it should work well as a way to get Fortran-like performance from HPC workloads written in C - which is where most of the people are who really want the alias analysis. > it seems like a nice opt-in thing that can be used where the aliases are > verified and the code is particularly performance critical... Yes. I think we could use it in the kernel, although I'm not sure how many cases we would ever find where we really care. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
