* Add a yield pattern for PowerPC64
* Fix compile error on pre-v6 ARM targets
* Use isb instead of yield on AArch64 to give the CPU a chance to enter
low-power states.
* Make the hint an inline function, the call overhead can be avoided.
This reverts commit 77cb45f59f.
Zig's error return traces will point to the return token if they
happen to occur, so having multiple return statements makes those
stack traces really helpful. This destroys debuggability.
Beside the new order being consistent with the ThreadPool API and making
more sense, this shuffling allows to write the context argument type in
terms of the startFn arguments, reducing the use of anytype (eg. less
explicit casts when using comptime_int parameters, yay).
Sorry for the breakage.
Closes#8082
* no isHaiku() function since there is not more than one os tag that
this applies to.
* clean up some control flow into a switch
* add some TODO comments to investigate panics that suspiciously look
like they should be compile errors (see #363)
* move concurrency primitives that always operate on kernel threads to
the std.Thread namespace
* remove std.SpinLock. Nobody should use this in a non-freestanding
environment; the other primitives are always preferable. In
freestanding, it will be necessary to put custom spin logic in there,
so there are no use cases for a std lib version.
* move some std lib files to the top level fields convention
* add std.Thread.spinLoopHint
* add std.Thread.Condition
* add std.Thread.Semaphore
* new implementation of std.Thread.Mutex for Windows and non-pthreads Linux
* add std.Thread.RwLock
Implementations provided by @kprotty
