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Rollup merge of #107739 - spastorino:check-overflow-evaluate_canonical_goal, r=lcnr

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Check for overflow in evaluate_canonical_goal

r? `@lcnr`
This commit is contained in:
Matthias Krüger 2023-02-14 18:02:50 +01:00 committed by GitHub
commit 9ee3c7ac4b
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 138 additions and 87 deletions
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29
compiler/rustc_trait_selection/src/solve/mod.rs
View File

@ -31,6 +31,7 @@
};
use rustc_span::DUMMY_SP;
use crate::solve::search_graph::OverflowHandler;
use crate::traits::ObligationCause;
mod assembly;
@ -210,27 +211,16 @@ fn evaluate_canonical_goal(
search_graph: &'a mut search_graph::SearchGraph<'tcx>,
canonical_goal: CanonicalGoal<'tcx>,
) -> QueryResult<'tcx> {
match search_graph.try_push_stack(tcx, canonical_goal) {
Ok(()) => {}
// Our goal is already on the stack, eager return.
Err(response) => return response,
}
// We may have to repeatedly recompute the goal in case of coinductive cycles,
// check out the `cache` module for more information.
// Deal with overflow, caching, and coinduction.
//
// FIXME: Similar to `evaluate_all`, this has to check for overflow.
loop {
// The actual solver logic happens in `ecx.compute_goal`.
search_graph.with_new_goal(tcx, canonical_goal, |search_graph| {
let (ref infcx, goal, var_values) =
tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal);
let mut ecx =
EvalCtxt { infcx, var_values, search_graph, in_projection_eq_hack: false };
let result = ecx.compute_goal(goal);
if search_graph.try_finalize_goal(tcx, canonical_goal, result) {
return result;
}
}
ecx.compute_goal(goal)
})
}
fn make_canonical_response(&self, certainty: Certainty) -> QueryResult<'tcx> {
@ -485,7 +475,9 @@ fn evaluate_all(
mut goals: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
) -> Result<Certainty, NoSolution> {
let mut new_goals = Vec::new();
self.repeat_while_none(|this| {
self.repeat_while_none(
|_| Ok(Certainty::Maybe(MaybeCause::Overflow)),
|this| {
let mut has_changed = Err(Certainty::Yes);
for goal in goals.drain(..) {
let (changed, certainty) = match this.evaluate_goal(goal) {
@ -513,7 +505,8 @@ fn evaluate_all(
}
Err(certainty) => Some(Ok(certainty)),
}
})
},
)
}
// Recursively evaluates a list of goals to completion, making a query response.

58
compiler/rustc_trait_selection/src/solve/search_graph/mod.rs
View File

@ -3,6 +3,7 @@
use self::cache::ProvisionalEntry;
use super::{CanonicalGoal, Certainty, MaybeCause, QueryResult};
pub(super) use crate::solve::search_graph::overflow::OverflowHandler;
use cache::ProvisionalCache;
use overflow::OverflowData;
use rustc_index::vec::IndexVec;
@ -46,7 +47,7 @@ pub(super) fn is_empty(&self) -> bool {
///
/// This correctly updates the provisional cache if there is a cycle.
#[instrument(level = "debug", skip(self, tcx), ret)]
pub(super) fn try_push_stack(
fn try_push_stack(
&mut self,
tcx: TyCtxt<'tcx>,
goal: CanonicalGoal<'tcx>,
@ -121,19 +122,19 @@ pub(super) fn try_push_stack(
///
/// FIXME: Refer to the rustc-dev-guide entry once it exists.
#[instrument(level = "debug", skip(self, tcx, actual_goal), ret)]
pub(super) fn try_finalize_goal(
fn try_finalize_goal(
&mut self,
tcx: TyCtxt<'tcx>,
actual_goal: CanonicalGoal<'tcx>,
response: QueryResult<'tcx>,
) -> bool {
let StackElem { goal, has_been_used } = self.stack.pop().unwrap();
let stack_elem = self.stack.pop().unwrap();
let StackElem { goal, has_been_used } = stack_elem;
assert_eq!(goal, actual_goal);
let cache = &mut self.provisional_cache;
let provisional_entry_index = *cache.lookup_table.get(&goal).unwrap();
let provisional_entry = &mut cache.entries[provisional_entry_index];
let depth = provisional_entry.depth;
// We eagerly update the response in the cache here. If we have to reevaluate
// this goal we use the new response when hitting a cycle, and we definitely
// want to access the final response whenever we look at the cache.
@ -157,6 +158,22 @@ pub(super) fn try_finalize_goal(
self.stack.push(StackElem { goal, has_been_used: false });
false
} else {
self.try_move_finished_goal_to_global_cache(tcx, stack_elem);
true
}
}
fn try_move_finished_goal_to_global_cache(
&mut self,
tcx: TyCtxt<'tcx>,
stack_elem: StackElem<'tcx>,
) {
let StackElem { goal, .. } = stack_elem;
let cache = &mut self.provisional_cache;
let provisional_entry_index = *cache.lookup_table.get(&goal).unwrap();
let provisional_entry = &mut cache.entries[provisional_entry_index];
let depth = provisional_entry.depth;
// If not, we're done with this goal.
//
// Check whether that this goal doesn't depend on a goal deeper on the stack
@ -165,8 +182,7 @@ pub(super) fn try_finalize_goal(
// Note that if any nested goal were to depend on something deeper on the stack,
// this would have also updated the depth of the current goal.
if depth == self.stack.next_index() {
for (i, entry) in cache.entries.drain_enumerated(provisional_entry_index.index()..)
{
for (i, entry) in cache.entries.drain_enumerated(provisional_entry_index.index()..) {
let actual_index = cache.lookup_table.remove(&entry.goal);
debug_assert_eq!(Some(i), actual_index);
debug_assert!(entry.depth == depth);
@ -179,7 +195,35 @@ pub(super) fn try_finalize_goal(
);
}
}
true
}
pub(super) fn with_new_goal(
&mut self,
tcx: TyCtxt<'tcx>,
canonical_goal: CanonicalGoal<'tcx>,
mut loop_body: impl FnMut(&mut Self) -> QueryResult<'tcx>,
) -> QueryResult<'tcx> {
match self.try_push_stack(tcx, canonical_goal) {
Ok(()) => {}
// Our goal is already on the stack, eager return.
Err(response) => return response,
}
self.repeat_while_none(
|this| {
let result = this.deal_with_overflow(tcx, canonical_goal);
let stack_elem = this.stack.pop().unwrap();
this.try_move_finished_goal_to_global_cache(tcx, stack_elem);
result
},
|this| {
let result = loop_body(this);
if this.try_finalize_goal(tcx, canonical_goal, result) {
Some(result)
} else {
None
}
},
)
}
}

58
compiler/rustc_trait_selection/src/solve/search_graph/overflow.rs
View File

@ -50,6 +50,42 @@ fn deal_with_overflow(&mut self) {
}
}
pub(in crate::solve) trait OverflowHandler<'tcx> {
fn search_graph(&mut self) -> &mut SearchGraph<'tcx>;
fn repeat_while_none<T>(
&mut self,
on_overflow: impl FnOnce(&mut Self) -> Result<T, NoSolution>,
mut loop_body: impl FnMut(&mut Self) -> Option<Result<T, NoSolution>>,
) -> Result<T, NoSolution> {
let start_depth = self.search_graph().overflow_data.additional_depth;
let depth = self.search_graph().stack.len();
while !self.search_graph().overflow_data.has_overflow(depth) {
if let Some(result) = loop_body(self) {
self.search_graph().overflow_data.additional_depth = start_depth;
return result;
}
self.search_graph().overflow_data.additional_depth += 1;
}
self.search_graph().overflow_data.additional_depth = start_depth;
self.search_graph().overflow_data.deal_with_overflow();
on_overflow(self)
}
}
impl<'tcx> OverflowHandler<'tcx> for EvalCtxt<'_, 'tcx> {
fn search_graph(&mut self) -> &mut SearchGraph<'tcx> {
&mut self.search_graph
}
}
impl<'tcx> OverflowHandler<'tcx> for SearchGraph<'tcx> {
fn search_graph(&mut self) -> &mut SearchGraph<'tcx> {
self
}
}
impl<'tcx> SearchGraph<'tcx> {
pub fn deal_with_overflow(
&mut self,
@ -60,25 +96,3 @@ pub fn deal_with_overflow(
response_no_constraints(tcx, goal, Certainty::Maybe(MaybeCause::Overflow))
}
}
impl<'tcx> EvalCtxt<'_, 'tcx> {
/// A `while`-loop which tracks overflow.
pub fn repeat_while_none(
&mut self,
mut loop_body: impl FnMut(&mut Self) -> Option<Result<Certainty, NoSolution>>,
) -> Result<Certainty, NoSolution> {
let start_depth = self.search_graph.overflow_data.additional_depth;
let depth = self.search_graph.stack.len();
while !self.search_graph.overflow_data.has_overflow(depth) {
if let Some(result) = loop_body(self) {
self.search_graph.overflow_data.additional_depth = start_depth;
return result;
}
self.search_graph.overflow_data.additional_depth += 1;
}
self.search_graph.overflow_data.additional_depth = start_depth;
self.search_graph.overflow_data.deal_with_overflow();
Ok(Certainty::Maybe(MaybeCause::Overflow))
}
}