Moved thread_local implementation to sys::common

This allows removing all the platform-dependent code from `library/std/src/thread/local.rs` and `library/std/src/thread/mod.rs`

Signed-off-by: Ayush Singh <ayushsingh1325@gmail.com>

1 files changed, 0 insertions, 373 deletions

diff --git a/library/std/src/thread/local.rs b/library/std/src/thread/local.rs
index c82b5c2284f..7fdf03acc14 100644
--- a/library/std/src/thread/local.rs
+++ b/library/std/src/thread/local.rs
@@ -585,376 +585,3 @@ impl<T: 'static> LocalKey<RefCell<T>> {
         self.with(|cell| cell.replace(value))
     }
 }
-
-mod lazy {
-    use crate::cell::UnsafeCell;
-    use crate::hint;
-    use crate::mem;
-
-    pub struct LazyKeyInner<T> {
-        inner: UnsafeCell<Option<T>>,
-    }
-
-    impl<T> LazyKeyInner<T> {
-        pub const fn new() -> LazyKeyInner<T> {
-            LazyKeyInner { inner: UnsafeCell::new(None) }
-        }
-
-        pub unsafe fn get(&self) -> Option<&'static T> {
-            // SAFETY: The caller must ensure no reference is ever handed out to
-            // the inner cell nor mutable reference to the Option<T> inside said
-            // cell. This make it safe to hand a reference, though the lifetime
-            // of 'static is itself unsafe, making the get method unsafe.
-            unsafe { (*self.inner.get()).as_ref() }
-        }
-
-        /// The caller must ensure that no reference is active: this method
-        /// needs unique access.
-        pub unsafe fn initialize<F: FnOnce() -> T>(&self, init: F) -> &'static T {
-            // Execute the initialization up front, *then* move it into our slot,
-            // just in case initialization fails.
-            let value = init();
-            let ptr = self.inner.get();
-
-            // SAFETY:
-            //
-            // note that this can in theory just be `*ptr = Some(value)`, but due to
-            // the compiler will currently codegen that pattern with something like:
-            //
-            //      ptr::drop_in_place(ptr)
-            //      ptr::write(ptr, Some(value))
-            //
-            // Due to this pattern it's possible for the destructor of the value in
-            // `ptr` (e.g., if this is being recursively initialized) to re-access
-            // TLS, in which case there will be a `&` and `&mut` pointer to the same
-            // value (an aliasing violation). To avoid setting the "I'm running a
-            // destructor" flag we just use `mem::replace` which should sequence the
-            // operations a little differently and make this safe to call.
-            //
-            // The precondition also ensures that we are the only one accessing
-            // `self` at the moment so replacing is fine.
-            unsafe {
-                let _ = mem::replace(&mut *ptr, Some(value));
-            }
-
-            // SAFETY: With the call to `mem::replace` it is guaranteed there is
-            // a `Some` behind `ptr`, not a `None` so `unreachable_unchecked`
-            // will never be reached.
-            unsafe {
-                // After storing `Some` we want to get a reference to the contents of
-                // what we just stored. While we could use `unwrap` here and it should
-                // always work it empirically doesn't seem to always get optimized away,
-                // which means that using something like `try_with` can pull in
-                // panicking code and cause a large size bloat.
-                match *ptr {
-                    Some(ref x) => x,
-                    None => hint::unreachable_unchecked(),
-                }
-            }
-        }
-
-        /// The other methods hand out references while taking &self.
-        /// As such, callers of this method must ensure no `&` and `&mut` are
-        /// available and used at the same time.
-        #[allow(unused)]
-        pub unsafe fn take(&mut self) -> Option<T> {
-            // SAFETY: See doc comment for this method.
-            unsafe { (*self.inner.get()).take() }
-        }
-    }
-}
-
-/// On some targets like wasm there's no threads, so no need to generate
-/// thread locals and we can instead just use plain statics!
-#[doc(hidden)]
-#[cfg(all(target_family = "wasm", not(target_feature = "atomics")))]
-pub mod statik {
-    use super::lazy::LazyKeyInner;
-    use crate::fmt;
-
-    pub struct Key<T> {
-        inner: LazyKeyInner<T>,
-    }
-
-    unsafe impl<T> Sync for Key<T> {}
-
-    impl<T> fmt::Debug for Key<T> {
-        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-            f.debug_struct("Key").finish_non_exhaustive()
-        }
-    }
-
-    impl<T> Key<T> {
-        pub const fn new() -> Key<T> {
-            Key { inner: LazyKeyInner::new() }
-        }
-
-        pub unsafe fn get(&self, init: impl FnOnce() -> T) -> Option<&'static T> {
-            // SAFETY: The caller must ensure no reference is ever handed out to
-            // the inner cell nor mutable reference to the Option<T> inside said
-            // cell. This make it safe to hand a reference, though the lifetime
-            // of 'static is itself unsafe, making the get method unsafe.
-            let value = unsafe {
-                match self.inner.get() {
-                    Some(ref value) => value,
-                    None => self.inner.initialize(init),
-                }
-            };
-
-            Some(value)
-        }
-    }
-}
-
-#[doc(hidden)]
-#[cfg(all(target_thread_local, not(all(target_family = "wasm", not(target_feature = "atomics"))),))]
-pub mod fast {
-    use super::lazy::LazyKeyInner;
-    use crate::cell::Cell;
-    use crate::sys::thread_local_dtor::register_dtor;
-    use crate::{fmt, mem, panic};
-
-    #[derive(Copy, Clone)]
-    enum DtorState {
-        Unregistered,
-        Registered,
-        RunningOrHasRun,
-    }
-
-    // This data structure has been carefully constructed so that the fast path
-    // only contains one branch on x86. That optimization is necessary to avoid
-    // duplicated tls lookups on OSX.
-    //
-    // LLVM issue: https://bugs.llvm.org/show_bug.cgi?id=41722
-    pub struct Key<T> {
-        // If `LazyKeyInner::get` returns `None`, that indicates either:
-        //   * The value has never been initialized
-        //   * The value is being recursively initialized
-        //   * The value has already been destroyed or is being destroyed
-        // To determine which kind of `None`, check `dtor_state`.
-        //
-        // This is very optimizer friendly for the fast path - initialized but
-        // not yet dropped.
-        inner: LazyKeyInner<T>,
-
-        // Metadata to keep track of the state of the destructor. Remember that
-        // this variable is thread-local, not global.
-        dtor_state: Cell<DtorState>,
-    }
-
-    impl<T> fmt::Debug for Key<T> {
-        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-            f.debug_struct("Key").finish_non_exhaustive()
-        }
-    }
-
-    impl<T> Key<T> {
-        pub const fn new() -> Key<T> {
-            Key { inner: LazyKeyInner::new(), dtor_state: Cell::new(DtorState::Unregistered) }
-        }
-
-        // note that this is just a publicly-callable function only for the
-        // const-initialized form of thread locals, basically a way to call the
-        // free `register_dtor` function defined elsewhere in std.
-        pub unsafe fn register_dtor(a: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) {
-            unsafe {
-                register_dtor(a, dtor);
-            }
-        }
-
-        pub unsafe fn get<F: FnOnce() -> T>(&self, init: F) -> Option<&'static T> {
-            // SAFETY: See the definitions of `LazyKeyInner::get` and
-            // `try_initialize` for more information.
-            //
-            // The caller must ensure no mutable references are ever active to
-            // the inner cell or the inner T when this is called.
-            // The `try_initialize` is dependant on the passed `init` function
-            // for this.
-            unsafe {
-                match self.inner.get() {
-                    Some(val) => Some(val),
-                    None => self.try_initialize(init),
-                }
-            }
-        }
-
-        // `try_initialize` is only called once per fast thread local variable,
-        // except in corner cases where thread_local dtors reference other
-        // thread_local's, or it is being recursively initialized.
-        //
-        // Macos: Inlining this function can cause two `tlv_get_addr` calls to
-        // be performed for every call to `Key::get`.
-        // LLVM issue: https://bugs.llvm.org/show_bug.cgi?id=41722
-        #[inline(never)]
-        unsafe fn try_initialize<F: FnOnce() -> T>(&self, init: F) -> Option<&'static T> {
-            // SAFETY: See comment above (this function doc).
-            if !mem::needs_drop::<T>() || unsafe { self.try_register_dtor() } {
-                // SAFETY: See comment above (this function doc).
-                Some(unsafe { self.inner.initialize(init) })
-            } else {
-                None
-            }
-        }
-
-        // `try_register_dtor` is only called once per fast thread local
-        // variable, except in corner cases where thread_local dtors reference
-        // other thread_local's, or it is being recursively initialized.
-        unsafe fn try_register_dtor(&self) -> bool {
-            match self.dtor_state.get() {
-                DtorState::Unregistered => {
-                    // SAFETY: dtor registration happens before initialization.
-                    // Passing `self` as a pointer while using `destroy_value<T>`
-                    // is safe because the function will build a pointer to a
-                    // Key<T>, which is the type of self and so find the correct
-                    // size.
-                    unsafe { register_dtor(self as *const _ as *mut u8, destroy_value::<T>) };
-                    self.dtor_state.set(DtorState::Registered);
-                    true
-                }
-                DtorState::Registered => {
-                    // recursively initialized
-                    true
-                }
-                DtorState::RunningOrHasRun => false,
-            }
-        }
-    }
-
-    unsafe extern "C" fn destroy_value<T>(ptr: *mut u8) {
-        let ptr = ptr as *mut Key<T>;
-
-        // SAFETY:
-        //
-        // The pointer `ptr` has been built just above and comes from
-        // `try_register_dtor` where it is originally a Key<T> coming from `self`,
-        // making it non-NUL and of the correct type.
-        //
-        // Right before we run the user destructor be sure to set the
-        // `Option<T>` to `None`, and `dtor_state` to `RunningOrHasRun`. This
-        // causes future calls to `get` to run `try_initialize_drop` again,
-        // which will now fail, and return `None`.
-        //
-        // Wrap the call in a catch to ensure unwinding is caught in the event
-        // a panic takes place in a destructor.
-        if let Err(_) = panic::catch_unwind(panic::AssertUnwindSafe(|| unsafe {
-            let value = (*ptr).inner.take();
-            (*ptr).dtor_state.set(DtorState::RunningOrHasRun);
-            drop(value);
-        })) {
-            rtabort!("thread local panicked on drop");
-        }
-    }
-}
-
-#[doc(hidden)]
-#[cfg(all(
-    not(target_thread_local),
-    not(all(target_family = "wasm", not(target_feature = "atomics"))),
-))]
-pub mod os {
-    use super::lazy::LazyKeyInner;
-    use crate::cell::Cell;
-    use crate::sys_common::thread_local_key::StaticKey as OsStaticKey;
-    use crate::{fmt, marker, panic, ptr};
-
-    /// Use a regular global static to store this key; the state provided will then be
-    /// thread-local.
-    pub struct Key<T> {
-        // OS-TLS key that we'll use to key off.
-        os: OsStaticKey,
-        marker: marker::PhantomData<Cell<T>>,
-    }
-
-    impl<T> fmt::Debug for Key<T> {
-        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-            f.debug_struct("Key").finish_non_exhaustive()
-        }
-    }
-
-    unsafe impl<T> Sync for Key<T> {}
-
-    struct Value<T: 'static> {
-        inner: LazyKeyInner<T>,
-        key: &'static Key<T>,
-    }
-
-    impl<T: 'static> Key<T> {
-        #[rustc_const_unstable(feature = "thread_local_internals", issue = "none")]
-        pub const fn new() -> Key<T> {
-            Key { os: OsStaticKey::new(Some(destroy_value::<T>)), marker: marker::PhantomData }
-        }
-
-        /// It is a requirement for the caller to ensure that no mutable
-        /// reference is active when this method is called.
-        pub unsafe fn get(&'static self, init: impl FnOnce() -> T) -> Option<&'static T> {
-            // SAFETY: See the documentation for this method.
-            let ptr = unsafe { self.os.get() as *mut Value<T> };
-            if ptr.addr() > 1 {
-                // SAFETY: the check ensured the pointer is safe (its destructor
-                // is not running) + it is coming from a trusted source (self).
-                if let Some(ref value) = unsafe { (*ptr).inner.get() } {
-                    return Some(value);
-                }
-            }
-            // SAFETY: At this point we are sure we have no value and so
-            // initializing (or trying to) is safe.
-            unsafe { self.try_initialize(init) }
-        }
-
-        // `try_initialize` is only called once per os thread local variable,
-        // except in corner cases where thread_local dtors reference other
-        // thread_local's, or it is being recursively initialized.
-        unsafe fn try_initialize(&'static self, init: impl FnOnce() -> T) -> Option<&'static T> {
-            // SAFETY: No mutable references are ever handed out meaning getting
-            // the value is ok.
-            let ptr = unsafe { self.os.get() as *mut Value<T> };
-            if ptr.addr() == 1 {
-                // destructor is running
-                return None;
-            }
-
-            let ptr = if ptr.is_null() {
-                // If the lookup returned null, we haven't initialized our own
-                // local copy, so do that now.
-                let ptr = Box::into_raw(Box::new(Value { inner: LazyKeyInner::new(), key: self }));
-                // SAFETY: At this point we are sure there is no value inside
-                // ptr so setting it will not affect anyone else.
-                unsafe {
-                    self.os.set(ptr as *mut u8);
-                }
-                ptr
-            } else {
-                // recursive initialization
-                ptr
-            };
-
-            // SAFETY: ptr has been ensured as non-NUL just above an so can be
-            // dereferenced safely.
-            unsafe { Some((*ptr).inner.initialize(init)) }
-        }
-    }
-
-    unsafe extern "C" fn destroy_value<T: 'static>(ptr: *mut u8) {
-        // SAFETY:
-        //
-        // The OS TLS ensures that this key contains a null value when this
-        // destructor starts to run. We set it back to a sentinel value of 1 to
-        // ensure that any future calls to `get` for this thread will return
-        // `None`.
-        //
-        // Note that to prevent an infinite loop we reset it back to null right
-        // before we return from the destructor ourselves.
-        //
-        // Wrap the call in a catch to ensure unwinding is caught in the event
-        // a panic takes place in a destructor.
-        if let Err(_) = panic::catch_unwind(|| unsafe {
-            let ptr = Box::from_raw(ptr as *mut Value<T>);
-            let key = ptr.key;
-            key.os.set(ptr::invalid_mut(1));
-            drop(ptr);
-            key.os.set(ptr::null_mut());
-        }) {
-            rtabort!("thread local panicked on drop");
-        }
-    }
-}