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Auto merge of #85885 - bjorn3:remove_box_region, r=cjgillot

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Don't use a generator for BoxedResolver

The generator is non-trivial and requires unsafe code anyway. Using regular unsafe code without a generator is much easier to follow.

Based on #85810 as it touches rustc_interface too.
This commit is contained in:
bors 2021-06-11 16:11:20 +00:00
commit 0a8629bff6
6 changed files with 91 additions and 215 deletions
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169
compiler/rustc_data_structures/src/box_region.rs
View file

@ -1,169 +0,0 @@
//! This module provides a way to deal with self-referential data.
//!
//! The main idea is to allocate such data in a generator frame and then
//! give access to it by executing user-provided closures inside that generator.
//! The module provides a safe abstraction for the latter task.
//!
//! The interface consists of two exported macros meant to be used together:
//! * `declare_box_region_type` wraps a generator inside a struct with `access`
//! method which accepts closures.
//! * `box_region_allow_access` is a helper which should be called inside
//! a generator to actually execute those closures.
use std::marker::PhantomData;
use std::ops::{Generator, GeneratorState};
use std::pin::Pin;
#[derive(Copy, Clone)]
pub struct AccessAction(*mut dyn FnMut());
impl AccessAction {
pub fn get(self) -> *mut dyn FnMut() {
self.0
}
}
#[derive(Copy, Clone)]
pub enum Action {
Initial,
Access(AccessAction),
Complete,
}
pub struct PinnedGenerator<I, A, R> {
generator: Pin<Box<dyn Generator<Action, Yield = YieldType<I, A>, Return = R>>>,
}
impl<I, A, R> PinnedGenerator<I, A, R> {
pub fn new<T: Generator<Action, Yield = YieldType<I, A>, Return = R> + 'static>(
generator: T,
) -> (I, Self) {
let mut result = PinnedGenerator { generator: Box::pin(generator) };
// Run it to the first yield to set it up
let init = match Pin::new(&mut result.generator).resume(Action::Initial) {
GeneratorState::Yielded(YieldType::Initial(y)) => y,
_ => panic!(),
};
(init, result)
}
pub unsafe fn access(&mut self, closure: *mut dyn FnMut()) {
// Call the generator, which in turn will call the closure
if let GeneratorState::Complete(_) =
Pin::new(&mut self.generator).resume(Action::Access(AccessAction(closure)))
{
panic!()
}
}
pub fn complete(&mut self) -> R {
// Tell the generator we want it to complete, consuming it and yielding a result
let result = Pin::new(&mut self.generator).resume(Action::Complete);
if let GeneratorState::Complete(r) = result { r } else { panic!() }
}
}
#[derive(PartialEq)]
pub struct Marker<T>(PhantomData<T>);
impl<T> Marker<T> {
pub unsafe fn new() -> Self {
Marker(PhantomData)
}
}
pub enum YieldType<I, A> {
Initial(I),
Accessor(Marker<A>),
}
#[macro_export]
#[allow_internal_unstable(fn_traits)]
macro_rules! declare_box_region_type {
(impl $v:vis
$name: ident,
$yield_type:ty,
for($($lifetimes:tt)*),
($($args:ty),*) -> ($reti:ty, $retc:ty)
) => {
$v struct $name($crate::box_region::PinnedGenerator<
$reti,
for<$($lifetimes)*> fn(($($args,)*)),
$retc
>);
impl $name {
fn new<T: ::std::ops::Generator<$crate::box_region::Action, Yield = $yield_type, Return = $retc> + 'static>(
generator: T
) -> ($reti, Self) {
let (initial, pinned) = $crate::box_region::PinnedGenerator::new(generator);
(initial, $name(pinned))
}
$v fn access<F: for<$($lifetimes)*> FnOnce($($args,)*) -> R, R>(&mut self, f: F) -> R {
// Turn the FnOnce closure into *mut dyn FnMut()
// so we can pass it in to the generator
let mut r = None;
let mut f = Some(f);
let mut_f: &mut dyn for<$($lifetimes)*> FnMut(($($args,)*)) =
&mut |args| {
let f = f.take().unwrap();
r = Some(FnOnce::call_once(f, args));
};
let mut_f = mut_f as *mut dyn for<$($lifetimes)*> FnMut(($($args,)*));
// Get the generator to call our closure
unsafe {
self.0.access(::std::mem::transmute(mut_f));
}
// Unwrap the result
r.unwrap()
}
$v fn complete(mut self) -> $retc {
self.0.complete()
}
fn initial_yield(value: $reti) -> $yield_type {
$crate::box_region::YieldType::Initial(value)
}
}
};
($v:vis $name: ident, for($($lifetimes:tt)*), ($($args:ty),*) -> ($reti:ty, $retc:ty)) => {
declare_box_region_type!(
impl $v $name,
$crate::box_region::YieldType<$reti, for<$($lifetimes)*> fn(($($args,)*))>,
for($($lifetimes)*),
($($args),*) -> ($reti, $retc)
);
};
}
#[macro_export]
#[allow_internal_unstable(fn_traits)]
macro_rules! box_region_allow_access {
(for($($lifetimes:tt)*), ($($args:ty),*), ($($exprs:expr),*), $action:ident) => {
loop {
match $action {
$crate::box_region::Action::Access(accessor) => {
let accessor: &mut dyn for<$($lifetimes)*> FnMut($($args),*) = unsafe {
::std::mem::transmute(accessor.get())
};
(*accessor)(($($exprs),*));
unsafe {
let marker = $crate::box_region::Marker::<
for<$($lifetimes)*> fn(($($args,)*))
>::new();
$action = yield $crate::box_region::YieldType::Accessor(marker);
};
}
$crate::box_region::Action::Complete => break,
$crate::box_region::Action::Initial => panic!("unexpected box_region action: Initial"),
}
}
}
}

2
compiler/rustc_data_structures/src/lib.rs
View file

@ -10,7 +10,6 @@
#![feature(array_windows)]
#![feature(control_flow_enum)]
#![feature(in_band_lifetimes)]
#![feature(generator_trait)]
#![feature(min_specialization)]
#![feature(auto_traits)]
#![feature(nll)]
@ -63,7 +62,6 @@ macro_rules! unlikely {
pub mod base_n;
pub mod binary_search_util;
pub mod box_region;
pub mod captures;
pub mod flock;
pub mod functor;