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Rollup merge of #116466 - nnethercote:rustc_transmute, r=oli-obk

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`rustc_transmute` cleanups

Just some things I found while poking around this code.

r? `@oli-obk`
This commit is contained in:
Matthias Krüger 2023-10-06 21:17:49 +02:00 committed by GitHub
commit 25fbd133ea
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2 changed files with 36 additions and 78 deletions
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4
compiler/rustc_transmute/src/lib.rs
View File

@ -9,7 +9,7 @@ extern crate tracing;
pub(crate) use rustc_data_structures::fx::{FxIndexMap as Map, FxIndexSet as Set};
pub mod layout;
pub(crate) mod maybe_transmutable;
mod maybe_transmutable;
#[derive(Default)]
pub struct Assume {
@ -19,7 +19,7 @@ pub struct Assume {
pub validity: bool,
}
/// Either we have an error, transmutation is allowed, or we have an optional
/// Either transmutation is allowed, we have an error, or we have an optional
/// Condition that must hold.
#[derive(Debug, Hash, Eq, PartialEq, Clone)]
pub enum Answer<R> {

110
compiler/rustc_transmute/src/maybe_transmutable/mod.rs
View File

@ -32,26 +32,6 @@ where
) -> Self {
Self { src, dst, scope, assume, context }
}
// FIXME(bryangarza): Delete this when all usages are removed
pub(crate) fn map_layouts<F, M>(
self,
f: F,
) -> Result<MaybeTransmutableQuery<M, C>, Answer<<C as QueryContext>::Ref>>
where
F: FnOnce(
L,
L,
<C as QueryContext>::Scope,
&C,
) -> Result<(M, M), Answer<<C as QueryContext>::Ref>>,
{
let Self { src, dst, scope, assume, context } = self;
let (src, dst) = f(src, dst, scope, &context)?;
Ok(MaybeTransmutableQuery { src, dst, scope, assume, context })
}
}
// FIXME: Nix this cfg, so we can write unit tests independently of rustc
@ -107,42 +87,42 @@ where
#[instrument(level = "debug", skip(self), fields(src = ?self.src, dst = ?self.dst))]
pub(crate) fn answer(self) -> Answer<<C as QueryContext>::Ref> {
let assume_visibility = self.assume.safety;
// FIXME(bryangarza): Refactor this code to get rid of `map_layouts`
let query_or_answer = self.map_layouts(|src, dst, scope, context| {
// Remove all `Def` nodes from `src`, without checking their visibility.
let src = src.prune(&|def| true);
trace!(?src, "pruned src");
let Self { src, dst, scope, assume, context } = self;
// Remove all `Def` nodes from `dst`, additionally...
let dst = if assume_visibility {
// ...if visibility is assumed, don't check their visibility.
dst.prune(&|def| true)
} else {
// ...otherwise, prune away all unreachable paths through the `Dst` layout.
dst.prune(&|def| context.is_accessible_from(def, scope))
};
// Remove all `Def` nodes from `src`, without checking their visibility.
let src = src.prune(&|def| true);
trace!(?dst, "pruned dst");
trace!(?src, "pruned src");
// Convert `src` from a tree-based representation to an NFA-based representation.
// If the conversion fails because `src` is uninhabited, conclude that the transmutation
// is acceptable, because instances of the `src` type do not exist.
let src = Nfa::from_tree(src).map_err(|Uninhabited| Answer::Yes)?;
// Remove all `Def` nodes from `dst`, additionally...
let dst = if assume_visibility {
// ...if visibility is assumed, don't check their visibility.
dst.prune(&|def| true)
} else {
// ...otherwise, prune away all unreachable paths through the `Dst` layout.
dst.prune(&|def| context.is_accessible_from(def, scope))
};
// Convert `dst` from a tree-based representation to an NFA-based representation.
// If the conversion fails because `src` is uninhabited, conclude that the transmutation
// is unacceptable, because instances of the `dst` type do not exist.
let dst =
Nfa::from_tree(dst).map_err(|Uninhabited| Answer::No(Reason::DstIsPrivate))?;
trace!(?dst, "pruned dst");
Ok((src, dst))
});
// Convert `src` from a tree-based representation to an NFA-based representation.
// If the conversion fails because `src` is uninhabited, conclude that the transmutation
// is acceptable, because instances of the `src` type do not exist.
let src = match Nfa::from_tree(src) {
Ok(src) => src,
Err(Uninhabited) => return Answer::Yes,
};
match query_or_answer {
Ok(query) => query.answer(),
Err(answer) => answer,
}
// Convert `dst` from a tree-based representation to an NFA-based representation.
// If the conversion fails because `src` is uninhabited, conclude that the transmutation
// is unacceptable, because instances of the `dst` type do not exist.
let dst = match Nfa::from_tree(dst) {
Ok(dst) => dst,
Err(Uninhabited) => return Answer::No(Reason::DstIsPrivate),
};
MaybeTransmutableQuery { src, dst, scope, assume, context }.answer()
}
}
@ -156,14 +136,10 @@ where
#[inline(always)]
#[instrument(level = "debug", skip(self), fields(src = ?self.src, dst = ?self.dst))]
pub(crate) fn answer(self) -> Answer<<C as QueryContext>::Ref> {
// FIXME(bryangarza): Refactor this code to get rid of `map_layouts`
let query_or_answer = self
.map_layouts(|src, dst, scope, context| Ok((Dfa::from_nfa(src), Dfa::from_nfa(dst))));
match query_or_answer {
Ok(query) => query.answer(),
Err(answer) => answer,
}
let Self { src, dst, scope, assume, context } = self;
let src = Dfa::from_nfa(src);
let dst = Dfa::from_nfa(dst);
MaybeTransmutableQuery { src, dst, scope, assume, context }.answer()
}
}
@ -171,26 +147,8 @@ impl<C> MaybeTransmutableQuery<Dfa<<C as QueryContext>::Ref>, C>
where
C: QueryContext,
{
/// Answers whether a `Nfa` is transmutable into another `Nfa`.
///
/// This method converts `src` and `dst` to DFAs, then computes an answer using those DFAs.
/// Answers whether a `Dfa` is transmutable into another `Dfa`.
pub(crate) fn answer(self) -> Answer<<C as QueryContext>::Ref> {
MaybeTransmutableQuery {
src: &self.src,
dst: &self.dst,
scope: self.scope,
assume: self.assume,
context: self.context,
}
.answer()
}
}
impl<'l, C> MaybeTransmutableQuery<&'l Dfa<<C as QueryContext>::Ref>, C>
where
C: QueryContext,
{
pub(crate) fn answer(&mut self) -> Answer<<C as QueryContext>::Ref> {
self.answer_memo(&mut Map::default(), self.src.start, self.dst.start)
}