This commit adds support for a scheduler that runs a scheduler on all
available cores. It is meant to be used on baremetal systems with a
fixed number of cores, such as the RP2040.
The initial implementation adds support for multicore scheduling to the
riscv-qemu target as a convenient testing target. This means that this
new multicore scheduler is tested in CI, including a bunch of standard
library tests (`make tinygo-test-baremetal`). This should ensure the new
scheduler is reasonably well tested before trying to use it on
harder-to-debug targets like the RP2040.
For the threads scheduler, it makes sense to have NumCPU available.
For all other schedulers, the number of available CPUs is practically
limited to one by the scheduler (even though the system might have more
CPUs).
This variable is only necessary on the cooperative and none scheduler.
It is not used on the threads scheduler.
The reason for moving is that the upcoming multicore baremetal scheduler
also needs mainExited but of a different type: an atomic variable
instead of a plain boolean.
This ensures:
1. The xorshift state is initialized during interp.
2. The xorshift state gets initialized to a real random number on
hardware that supports it at runtime.
This fixes a big binary size regression from the previous commit. It's
still not perfect: most programs increase binary size by a few bytes.
But it's not nearly as bad as before.
This moves all scheduler code into a separate file that is only compiled
when there's a scheduler in use (the tasks or asyncify scheduler, which
are both cooperative). The main goal of this change is to make it easier
to add a new "scheduler" based on OS threads.
It also fixes a few subtle issues with `-gc=none`:
- Gosched() panicked. This is now fixed to just return immediately
(the only logical thing to do when there's only one goroutine).
- Timers aren't supported without a scheduler, but the relevant code
was still present and would happily add a timer to the queue. It
just never ran. So now it exits with a runtime error, similar to any
blocking operation.
Ayke van Laethem
Elias Naur