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Document mutated_statement.

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This commit is contained in:
Camille GILLOT 2023-10-17 18:35:13 +00:00
parent 4abea83663
commit b5aa1ef9b4
1 changed files with 15 additions and 4 deletions
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19
compiler/rustc_mir_transform/src/jump_threading.rs
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@ -273,6 +273,18 @@ impl<'tcx, 'a> TOFinder<'tcx, 'a> {
}
/// Extract the mutated place from a statement.
///
/// This method returns the `Place` so we can flood the state in case of a partial assignment.
/// (_1 as Ok).0 = _5;
/// (_1 as Err).0 = _6;
/// We want to ensure that a `SwitchInt((_1 as Ok).0)` does not see the first assignment, as
/// the value may have been mangled by the second assignment.
///
/// In case we assign to a discriminant, we return `Some(TrackElem::Discriminant)`, so we can
/// stop at flooding the discriminant, and preserve the variant fields.
/// (_1 as Some).0 = _6;
/// SetDiscriminant(_1, 1);
/// switchInt((_1 as Some).0)
#[instrument(level = "trace", skip(self), ret)]
fn mutated_statement(
&self,
@ -280,9 +292,6 @@ impl<'tcx, 'a> TOFinder<'tcx, 'a> {
) -> Option<(Place<'tcx>, Option<TrackElem>)> {
match stmt.kind {
StatementKind::Assign(box (place, _))
| StatementKind::Intrinsic(box NonDivergingIntrinsic::Assume(
Operand::Copy(place) | Operand::Move(place),
))
| StatementKind::Deinit(box place) => Some((place, None)),
StatementKind::SetDiscriminant { box place, variant_index: _ } => {
Some((place, Some(TrackElem::Discriminant)))
@ -291,7 +300,9 @@ impl<'tcx, 'a> TOFinder<'tcx, 'a> {
Some((Place::from(local), None))
}
StatementKind::Retag(..)
| StatementKind::Intrinsic(..)
| StatementKind::Intrinsic(box NonDivergingIntrinsic::Assume(..))
// copy_nonoverlapping takes pointers and mutated the pointed-to value.
| StatementKind::Intrinsic(box NonDivergingIntrinsic::CopyNonOverlapping(..))
| StatementKind::AscribeUserType(..)
| StatementKind::Coverage(..)
| StatementKind::FakeRead(..)