This pull request extracts all scheduling functionality from libstd, moving it into its own separate crates. The new libnative and libgreen will be the new way in which 1:1 and M:N scheduling is implemented. The standard library still requires an interface to the runtime, however, (think of things like `std::comm` and `io::println`). The interface is now defined by the `Runtime` trait inside of `std::rt`.
The booting process is now that libgreen defines the start lang-item and that's it. I want to extend this soon to have libnative also have a "start lang item" but also allow libgreen and libnative to be linked together in the same process. For now though, only libgreen can be used to start a program (unless you define the start lang item yourself). Again though, I want to change this soon, I just figured that this pull request is large enough as-is.
This certainly wasn't a smooth transition, certain functionality has no equivalent in this new separation, and some functionality is now better enabled through this new system. I did my best to separate all of the commits by topic and keep things fairly bite-sized, although are indeed larger than others.
As a note, this is currently rebased on top of my `std::comm` rewrite (or at least an old copy of it), but none of those commits need reviewing (that will all happen in another pull request).
For now, this moves the following modules to std::sync
* UnsafeArc (also removed unwrap method)
* mpsc_queue
* spsc_queue
* atomics
* mpmc_bounded_queue
* deque
We may want to remove some of the queues, but for now this moves things out of
std::rt into std::sync
This uses quite a bit of unsafe code for speed and failure safety, and allocates `2*n` temporary storage.
[Performance](https://gist.github.com/huonw/5547f2478380288a28c2):
| n | new | priority_queue | quick3 |
|-------:|---------:|---------------:|---------:|
| 5 | 200 | 155 | 106 |
| 100 | 6490 | 8750 | 5810 |
| 10000 | 1300000 | 1790000 | 1060000 |
| 100000 | 16700000 | 23600000 | 12700000 |
| sorted | 520000 | 1380000 | 53900000 |
| trend | 1310000 | 1690000 | 1100000 |
(The times are in nanoseconds, having subtracted the set-up time (i.e. the `just_generate` bench target).)
I imagine that there is still significant room for improvement, particularly because both priority_queue and quick3 are doing a static call via `Ord` or `TotalOrd` for the comparisons, while this is using a (boxed) closure.
Also, this code does not `clone`, unlike `quick_sort3`; and is stable, unlike both of the others.
Right now the --crate-id and related flags are all process *after* the entire
crate is parsed. This is less than desirable when used with makefiles because it
means that just to learn the output name of the crate you have to parse the
entire crate (unnecessary).
This commit changes the behavior to lift the handling of these flags much sooner
in the compilation process. This allows us to not have to parse the entire crate
and only have to worry about parsing the crate attributes themselves. The
related methods have all been updated to take an array of attributes rather than
a crate.
Additionally, this ceases duplication of the "what output are we producing"
logic in order to correctly handle things in the case of --test.
Finally, this adds tests for all of this functionality to ensure that it does
not regress.
