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Shrink a loop to its looping part and move out the part that runs after the loop

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This commit is contained in:
Oli Scherer 2024-04-09 07:53:12 +00:00
parent 626fd4b258
commit f014e91a38
1 changed files with 54 additions and 54 deletions
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108
compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
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@ -144,67 +144,67 @@ impl<'tcx> MirPass<'tcx> for ByMoveBody {
.skip(num_args) .skip(num_args)
.enumerate() .enumerate()
{ {
let (mut parent_field_idx, mut parent_capture);
loop { loop {
let &(parent_field_idx, parent_capture) = (parent_field_idx, parent_capture) =
parent_captures.peek().expect("we ran out of parent captures!"); *parent_captures.peek().expect("we ran out of parent captures!");
// A parent matches a child they share the same prefix of projections. // A parent matches a child they share the same prefix of projections.
// The child may have more, if it is capturing sub-fields out of // The child may have more, if it is capturing sub-fields out of
// something that is captured by-move in the parent closure. // something that is captured by-move in the parent closure.
if !child_prefix_matches_parent_projections(parent_capture, child_capture) { if child_prefix_matches_parent_projections(parent_capture, child_capture) {
// Make sure the field was used at least once. break;
assert!(
field_used_at_least_once,
"we captured {parent_capture:#?} but it was not used in the child coroutine?"
);
field_used_at_least_once = false;
// Skip this field.
let _ = parent_captures.next().unwrap();
continue;
} }
// Make sure the field was used at least once.
// Store this set of additional projections (fields and derefs). assert!(
// We need to re-apply them later. field_used_at_least_once,
let child_precise_captures = "we captured {parent_capture:#?} but it was not used in the child coroutine?"
&child_capture.place.projections[parent_capture.place.projections.len()..];
// If the parent captures by-move, and the child captures by-ref, then we
// need to peel an additional `deref` off of the body of the child.
let needs_deref = child_capture.is_by_ref() && !parent_capture.is_by_ref();
if needs_deref {
assert_ne!(
coroutine_kind,
ty::ClosureKind::FnOnce,
"`FnOnce` coroutine-closures return coroutines that capture from \
their body; it will always result in a borrowck error!"
);
}
// Finally, store the type of the parent's captured place. We need
// this when building the field projection in the MIR body later on.
let mut parent_capture_ty = parent_capture.place.ty();
parent_capture_ty = match parent_capture.info.capture_kind {
ty::UpvarCapture::ByValue => parent_capture_ty,
ty::UpvarCapture::ByRef(kind) => Ty::new_ref(
tcx,
tcx.lifetimes.re_erased,
parent_capture_ty,
kind.to_mutbl_lossy(),
),
};
field_remapping.insert(
FieldIdx::from_usize(child_field_idx + num_args),
(
FieldIdx::from_usize(parent_field_idx + num_args),
parent_capture_ty,
needs_deref,
child_precise_captures,
),
); );
field_used_at_least_once = false;
field_used_at_least_once = true; // Skip this field.
break; let _ = parent_captures.next().unwrap();
} }
// Store this set of additional projections (fields and derefs).
// We need to re-apply them later.
let child_precise_captures =
&child_capture.place.projections[parent_capture.place.projections.len()..];
// If the parent captures by-move, and the child captures by-ref, then we
// need to peel an additional `deref` off of the body of the child.
let needs_deref = child_capture.is_by_ref() && !parent_capture.is_by_ref();
if needs_deref {
assert_ne!(
coroutine_kind,
ty::ClosureKind::FnOnce,
"`FnOnce` coroutine-closures return coroutines that capture from \
their body; it will always result in a borrowck error!"
);
}
// Finally, store the type of the parent's captured place. We need
// this when building the field projection in the MIR body later on.
let mut parent_capture_ty = parent_capture.place.ty();
parent_capture_ty = match parent_capture.info.capture_kind {
ty::UpvarCapture::ByValue => parent_capture_ty,
ty::UpvarCapture::ByRef(kind) => Ty::new_ref(
tcx,
tcx.lifetimes.re_erased,
parent_capture_ty,
kind.to_mutbl_lossy(),
),
};
field_remapping.insert(
FieldIdx::from_usize(child_field_idx + num_args),
(
FieldIdx::from_usize(parent_field_idx + num_args),
parent_capture_ty,
needs_deref,
child_precise_captures,
),
);
field_used_at_least_once = true;
} }
// Pop the last parent capture // Pop the last parent capture