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-rw-r--r--src/tools/clippy/clippy_lints/src/redundant_clone.rs776
1 files changed, 776 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/redundant_clone.rs b/src/tools/clippy/clippy_lints/src/redundant_clone.rs
new file mode 100644
index 000000000..eddca6045
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/redundant_clone.rs
@@ -0,0 +1,776 @@
+use clippy_utils::diagnostics::{span_lint_hir, span_lint_hir_and_then};
+use clippy_utils::source::snippet_opt;
+use clippy_utils::ty::{has_drop, is_copy, is_type_diagnostic_item, walk_ptrs_ty_depth};
+use clippy_utils::{fn_has_unsatisfiable_preds, match_def_path, paths};
+use if_chain::if_chain;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::Applicability;
+use rustc_hir::intravisit::FnKind;
+use rustc_hir::{def_id, Body, FnDecl, HirId};
+use rustc_index::bit_set::{BitSet, HybridBitSet};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::mir::{
+ self, traversal,
+ visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor as _},
+ Mutability,
+};
+use rustc_middle::ty::{self, visit::TypeVisitor, Ty};
+use rustc_mir_dataflow::{Analysis, AnalysisDomain, CallReturnPlaces, GenKill, GenKillAnalysis, ResultsCursor};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::source_map::{BytePos, Span};
+use rustc_span::sym;
+use std::ops::ControlFlow;
+
+macro_rules! unwrap_or_continue {
+ ($x:expr) => {
+ match $x {
+ Some(x) => x,
+ None => continue,
+ }
+ };
+}
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for a redundant `clone()` (and its relatives) which clones an owned
+ /// value that is going to be dropped without further use.
+ ///
+ /// ### Why is this bad?
+ /// It is not always possible for the compiler to eliminate useless
+ /// allocations and deallocations generated by redundant `clone()`s.
+ ///
+ /// ### Known problems
+ /// False-negatives: analysis performed by this lint is conservative and limited.
+ ///
+ /// ### Example
+ /// ```rust
+ /// # use std::path::Path;
+ /// # #[derive(Clone)]
+ /// # struct Foo;
+ /// # impl Foo {
+ /// # fn new() -> Self { Foo {} }
+ /// # }
+ /// # fn call(x: Foo) {}
+ /// {
+ /// let x = Foo::new();
+ /// call(x.clone());
+ /// call(x.clone()); // this can just pass `x`
+ /// }
+ ///
+ /// ["lorem", "ipsum"].join(" ").to_string();
+ ///
+ /// Path::new("/a/b").join("c").to_path_buf();
+ /// ```
+ #[clippy::version = "1.32.0"]
+ pub REDUNDANT_CLONE,
+ perf,
+ "`clone()` of an owned value that is going to be dropped immediately"
+}
+
+declare_lint_pass!(RedundantClone => [REDUNDANT_CLONE]);
+
+impl<'tcx> LateLintPass<'tcx> for RedundantClone {
+ #[expect(clippy::too_many_lines)]
+ fn check_fn(
+ &mut self,
+ cx: &LateContext<'tcx>,
+ _: FnKind<'tcx>,
+ _: &'tcx FnDecl<'_>,
+ body: &'tcx Body<'_>,
+ _: Span,
+ _: HirId,
+ ) {
+ let def_id = cx.tcx.hir().body_owner_def_id(body.id());
+
+ // Building MIR for `fn`s with unsatisfiable preds results in ICE.
+ if fn_has_unsatisfiable_preds(cx, def_id.to_def_id()) {
+ return;
+ }
+
+ let mir = cx.tcx.optimized_mir(def_id.to_def_id());
+
+ let possible_origin = {
+ let mut vis = PossibleOriginVisitor::new(mir);
+ vis.visit_body(mir);
+ vis.into_map(cx)
+ };
+ let maybe_storage_live_result = MaybeStorageLive
+ .into_engine(cx.tcx, mir)
+ .pass_name("redundant_clone")
+ .iterate_to_fixpoint()
+ .into_results_cursor(mir);
+ let mut possible_borrower = {
+ let mut vis = PossibleBorrowerVisitor::new(cx, mir, possible_origin);
+ vis.visit_body(mir);
+ vis.into_map(cx, maybe_storage_live_result)
+ };
+
+ for (bb, bbdata) in mir.basic_blocks().iter_enumerated() {
+ let terminator = bbdata.terminator();
+
+ if terminator.source_info.span.from_expansion() {
+ continue;
+ }
+
+ // Give up on loops
+ if terminator.successors().any(|s| s == bb) {
+ continue;
+ }
+
+ let (fn_def_id, arg, arg_ty, clone_ret) =
+ unwrap_or_continue!(is_call_with_ref_arg(cx, mir, &terminator.kind));
+
+ let from_borrow = match_def_path(cx, fn_def_id, &paths::CLONE_TRAIT_METHOD)
+ || match_def_path(cx, fn_def_id, &paths::TO_OWNED_METHOD)
+ || (match_def_path(cx, fn_def_id, &paths::TO_STRING_METHOD)
+ && is_type_diagnostic_item(cx, arg_ty, sym::String));
+
+ let from_deref = !from_borrow
+ && (match_def_path(cx, fn_def_id, &paths::PATH_TO_PATH_BUF)
+ || match_def_path(cx, fn_def_id, &paths::OS_STR_TO_OS_STRING));
+
+ if !from_borrow && !from_deref {
+ continue;
+ }
+
+ if let ty::Adt(def, _) = arg_ty.kind() {
+ if def.is_manually_drop() {
+ continue;
+ }
+ }
+
+ // `{ arg = &cloned; clone(move arg); }` or `{ arg = &cloned; to_path_buf(arg); }`
+ let (cloned, cannot_move_out) = unwrap_or_continue!(find_stmt_assigns_to(cx, mir, arg, from_borrow, bb));
+
+ let loc = mir::Location {
+ block: bb,
+ statement_index: bbdata.statements.len(),
+ };
+
+ // `Local` to be cloned, and a local of `clone` call's destination
+ let (local, ret_local) = if from_borrow {
+ // `res = clone(arg)` can be turned into `res = move arg;`
+ // if `arg` is the only borrow of `cloned` at this point.
+
+ if cannot_move_out || !possible_borrower.only_borrowers(&[arg], cloned, loc) {
+ continue;
+ }
+
+ (cloned, clone_ret)
+ } else {
+ // `arg` is a reference as it is `.deref()`ed in the previous block.
+ // Look into the predecessor block and find out the source of deref.
+
+ let ps = &mir.basic_blocks.predecessors()[bb];
+ if ps.len() != 1 {
+ continue;
+ }
+ let pred_terminator = mir[ps[0]].terminator();
+
+ // receiver of the `deref()` call
+ let (pred_arg, deref_clone_ret) = if_chain! {
+ if let Some((pred_fn_def_id, pred_arg, pred_arg_ty, res)) =
+ is_call_with_ref_arg(cx, mir, &pred_terminator.kind);
+ if res == cloned;
+ if cx.tcx.is_diagnostic_item(sym::deref_method, pred_fn_def_id);
+ if is_type_diagnostic_item(cx, pred_arg_ty, sym::PathBuf)
+ || is_type_diagnostic_item(cx, pred_arg_ty, sym::OsString);
+ then {
+ (pred_arg, res)
+ } else {
+ continue;
+ }
+ };
+
+ let (local, cannot_move_out) =
+ unwrap_or_continue!(find_stmt_assigns_to(cx, mir, pred_arg, true, ps[0]));
+ let loc = mir::Location {
+ block: bb,
+ statement_index: mir.basic_blocks()[bb].statements.len(),
+ };
+
+ // This can be turned into `res = move local` if `arg` and `cloned` are not borrowed
+ // at the last statement:
+ //
+ // ```
+ // pred_arg = &local;
+ // cloned = deref(pred_arg);
+ // arg = &cloned;
+ // StorageDead(pred_arg);
+ // res = to_path_buf(cloned);
+ // ```
+ if cannot_move_out || !possible_borrower.only_borrowers(&[arg, cloned], local, loc) {
+ continue;
+ }
+
+ (local, deref_clone_ret)
+ };
+
+ let clone_usage = if local == ret_local {
+ CloneUsage {
+ cloned_used: false,
+ cloned_consume_or_mutate_loc: None,
+ clone_consumed_or_mutated: true,
+ }
+ } else {
+ let clone_usage = visit_clone_usage(local, ret_local, mir, bb);
+ if clone_usage.cloned_used && clone_usage.clone_consumed_or_mutated {
+ // cloned value is used, and the clone is modified or moved
+ continue;
+ } else if let Some(loc) = clone_usage.cloned_consume_or_mutate_loc {
+ // cloned value is mutated, and the clone is alive.
+ if possible_borrower.local_is_alive_at(ret_local, loc) {
+ continue;
+ }
+ }
+ clone_usage
+ };
+
+ let span = terminator.source_info.span;
+ let scope = terminator.source_info.scope;
+ let node = mir.source_scopes[scope]
+ .local_data
+ .as_ref()
+ .assert_crate_local()
+ .lint_root;
+
+ if_chain! {
+ if let Some(snip) = snippet_opt(cx, span);
+ if let Some(dot) = snip.rfind('.');
+ then {
+ let sugg_span = span.with_lo(
+ span.lo() + BytePos(u32::try_from(dot).unwrap())
+ );
+ let mut app = Applicability::MaybeIncorrect;
+
+ let call_snip = &snip[dot + 1..];
+ // Machine applicable when `call_snip` looks like `foobar()`
+ if let Some(call_snip) = call_snip.strip_suffix("()").map(str::trim) {
+ if call_snip.as_bytes().iter().all(|b| b.is_ascii_alphabetic() || *b == b'_') {
+ app = Applicability::MachineApplicable;
+ }
+ }
+
+ span_lint_hir_and_then(cx, REDUNDANT_CLONE, node, sugg_span, "redundant clone", |diag| {
+ diag.span_suggestion(
+ sugg_span,
+ "remove this",
+ "",
+ app,
+ );
+ if clone_usage.cloned_used {
+ diag.span_note(
+ span,
+ "cloned value is neither consumed nor mutated",
+ );
+ } else {
+ diag.span_note(
+ span.with_hi(span.lo() + BytePos(u32::try_from(dot).unwrap())),
+ "this value is dropped without further use",
+ );
+ }
+ });
+ } else {
+ span_lint_hir(cx, REDUNDANT_CLONE, node, span, "redundant clone");
+ }
+ }
+ }
+ }
+}
+
+/// If `kind` is `y = func(x: &T)` where `T: !Copy`, returns `(DefId of func, x, T, y)`.
+fn is_call_with_ref_arg<'tcx>(
+ cx: &LateContext<'tcx>,
+ mir: &'tcx mir::Body<'tcx>,
+ kind: &'tcx mir::TerminatorKind<'tcx>,
+) -> Option<(def_id::DefId, mir::Local, Ty<'tcx>, mir::Local)> {
+ if_chain! {
+ if let mir::TerminatorKind::Call { func, args, destination, .. } = kind;
+ if args.len() == 1;
+ if let mir::Operand::Move(mir::Place { local, .. }) = &args[0];
+ if let ty::FnDef(def_id, _) = *func.ty(mir, cx.tcx).kind();
+ if let (inner_ty, 1) = walk_ptrs_ty_depth(args[0].ty(mir, cx.tcx));
+ if !is_copy(cx, inner_ty);
+ then {
+ Some((def_id, *local, inner_ty, destination.as_local()?))
+ } else {
+ None
+ }
+ }
+}
+
+type CannotMoveOut = bool;
+
+/// Finds the first `to = (&)from`, and returns
+/// ``Some((from, whether `from` cannot be moved out))``.
+fn find_stmt_assigns_to<'tcx>(
+ cx: &LateContext<'tcx>,
+ mir: &mir::Body<'tcx>,
+ to_local: mir::Local,
+ by_ref: bool,
+ bb: mir::BasicBlock,
+) -> Option<(mir::Local, CannotMoveOut)> {
+ let rvalue = mir.basic_blocks()[bb].statements.iter().rev().find_map(|stmt| {
+ if let mir::StatementKind::Assign(box (mir::Place { local, .. }, v)) = &stmt.kind {
+ return if *local == to_local { Some(v) } else { None };
+ }
+
+ None
+ })?;
+
+ match (by_ref, rvalue) {
+ (true, mir::Rvalue::Ref(_, _, place)) | (false, mir::Rvalue::Use(mir::Operand::Copy(place))) => {
+ Some(base_local_and_movability(cx, mir, *place))
+ },
+ (false, mir::Rvalue::Ref(_, _, place)) => {
+ if let [mir::ProjectionElem::Deref] = place.as_ref().projection {
+ Some(base_local_and_movability(cx, mir, *place))
+ } else {
+ None
+ }
+ },
+ _ => None,
+ }
+}
+
+/// Extracts and returns the undermost base `Local` of given `place`. Returns `place` itself
+/// if it is already a `Local`.
+///
+/// Also reports whether given `place` cannot be moved out.
+fn base_local_and_movability<'tcx>(
+ cx: &LateContext<'tcx>,
+ mir: &mir::Body<'tcx>,
+ place: mir::Place<'tcx>,
+) -> (mir::Local, CannotMoveOut) {
+ use rustc_middle::mir::PlaceRef;
+
+ // Dereference. You cannot move things out from a borrowed value.
+ let mut deref = false;
+ // Accessing a field of an ADT that has `Drop`. Moving the field out will cause E0509.
+ let mut field = false;
+ // If projection is a slice index then clone can be removed only if the
+ // underlying type implements Copy
+ let mut slice = false;
+
+ let PlaceRef { local, mut projection } = place.as_ref();
+ while let [base @ .., elem] = projection {
+ projection = base;
+ deref |= matches!(elem, mir::ProjectionElem::Deref);
+ field |= matches!(elem, mir::ProjectionElem::Field(..))
+ && has_drop(cx, mir::Place::ty_from(local, projection, &mir.local_decls, cx.tcx).ty);
+ slice |= matches!(elem, mir::ProjectionElem::Index(..))
+ && !is_copy(cx, mir::Place::ty_from(local, projection, &mir.local_decls, cx.tcx).ty);
+ }
+
+ (local, deref || field || slice)
+}
+
+#[derive(Default)]
+struct CloneUsage {
+ /// Whether the cloned value is used after the clone.
+ cloned_used: bool,
+ /// The first location where the cloned value is consumed or mutated, if any.
+ cloned_consume_or_mutate_loc: Option<mir::Location>,
+ /// Whether the clone value is mutated.
+ clone_consumed_or_mutated: bool,
+}
+fn visit_clone_usage(cloned: mir::Local, clone: mir::Local, mir: &mir::Body<'_>, bb: mir::BasicBlock) -> CloneUsage {
+ struct V {
+ cloned: mir::Local,
+ clone: mir::Local,
+ result: CloneUsage,
+ }
+ impl<'tcx> mir::visit::Visitor<'tcx> for V {
+ fn visit_basic_block_data(&mut self, block: mir::BasicBlock, data: &mir::BasicBlockData<'tcx>) {
+ let statements = &data.statements;
+ for (statement_index, statement) in statements.iter().enumerate() {
+ self.visit_statement(statement, mir::Location { block, statement_index });
+ }
+
+ self.visit_terminator(
+ data.terminator(),
+ mir::Location {
+ block,
+ statement_index: statements.len(),
+ },
+ );
+ }
+
+ fn visit_place(&mut self, place: &mir::Place<'tcx>, ctx: PlaceContext, loc: mir::Location) {
+ let local = place.local;
+
+ if local == self.cloned
+ && !matches!(
+ ctx,
+ PlaceContext::MutatingUse(MutatingUseContext::Drop) | PlaceContext::NonUse(_)
+ )
+ {
+ self.result.cloned_used = true;
+ self.result.cloned_consume_or_mutate_loc = self.result.cloned_consume_or_mutate_loc.or_else(|| {
+ matches!(
+ ctx,
+ PlaceContext::NonMutatingUse(NonMutatingUseContext::Move)
+ | PlaceContext::MutatingUse(MutatingUseContext::Borrow)
+ )
+ .then(|| loc)
+ });
+ } else if local == self.clone {
+ match ctx {
+ PlaceContext::NonMutatingUse(NonMutatingUseContext::Move)
+ | PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
+ self.result.clone_consumed_or_mutated = true;
+ },
+ _ => {},
+ }
+ }
+ }
+ }
+
+ let init = CloneUsage {
+ cloned_used: false,
+ cloned_consume_or_mutate_loc: None,
+ // Consider non-temporary clones consumed.
+ // TODO: Actually check for mutation of non-temporaries.
+ clone_consumed_or_mutated: mir.local_kind(clone) != mir::LocalKind::Temp,
+ };
+ traversal::ReversePostorder::new(mir, bb)
+ .skip(1)
+ .fold(init, |usage, (tbb, tdata)| {
+ // Short-circuit
+ if (usage.cloned_used && usage.clone_consumed_or_mutated) ||
+ // Give up on loops
+ tdata.terminator().successors().any(|s| s == bb)
+ {
+ return CloneUsage {
+ cloned_used: true,
+ clone_consumed_or_mutated: true,
+ ..usage
+ };
+ }
+
+ let mut v = V {
+ cloned,
+ clone,
+ result: usage,
+ };
+ v.visit_basic_block_data(tbb, tdata);
+ v.result
+ })
+}
+
+/// Determines liveness of each local purely based on `StorageLive`/`Dead`.
+#[derive(Copy, Clone)]
+struct MaybeStorageLive;
+
+impl<'tcx> AnalysisDomain<'tcx> for MaybeStorageLive {
+ type Domain = BitSet<mir::Local>;
+ const NAME: &'static str = "maybe_storage_live";
+
+ fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
+ // bottom = dead
+ BitSet::new_empty(body.local_decls.len())
+ }
+
+ fn initialize_start_block(&self, body: &mir::Body<'tcx>, state: &mut Self::Domain) {
+ for arg in body.args_iter() {
+ state.insert(arg);
+ }
+ }
+}
+
+impl<'tcx> GenKillAnalysis<'tcx> for MaybeStorageLive {
+ type Idx = mir::Local;
+
+ fn statement_effect(&self, trans: &mut impl GenKill<Self::Idx>, stmt: &mir::Statement<'tcx>, _: mir::Location) {
+ match stmt.kind {
+ mir::StatementKind::StorageLive(l) => trans.gen(l),
+ mir::StatementKind::StorageDead(l) => trans.kill(l),
+ _ => (),
+ }
+ }
+
+ fn terminator_effect(
+ &self,
+ _trans: &mut impl GenKill<Self::Idx>,
+ _terminator: &mir::Terminator<'tcx>,
+ _loc: mir::Location,
+ ) {
+ }
+
+ fn call_return_effect(
+ &self,
+ _trans: &mut impl GenKill<Self::Idx>,
+ _block: mir::BasicBlock,
+ _return_places: CallReturnPlaces<'_, 'tcx>,
+ ) {
+ // Nothing to do when a call returns successfully
+ }
+}
+
+/// Collects the possible borrowers of each local.
+/// For example, `b = &a; c = &a;` will make `b` and (transitively) `c`
+/// possible borrowers of `a`.
+struct PossibleBorrowerVisitor<'a, 'tcx> {
+ possible_borrower: TransitiveRelation,
+ body: &'a mir::Body<'tcx>,
+ cx: &'a LateContext<'tcx>,
+ possible_origin: FxHashMap<mir::Local, HybridBitSet<mir::Local>>,
+}
+
+impl<'a, 'tcx> PossibleBorrowerVisitor<'a, 'tcx> {
+ fn new(
+ cx: &'a LateContext<'tcx>,
+ body: &'a mir::Body<'tcx>,
+ possible_origin: FxHashMap<mir::Local, HybridBitSet<mir::Local>>,
+ ) -> Self {
+ Self {
+ possible_borrower: TransitiveRelation::default(),
+ cx,
+ body,
+ possible_origin,
+ }
+ }
+
+ fn into_map(
+ self,
+ cx: &LateContext<'tcx>,
+ maybe_live: ResultsCursor<'tcx, 'tcx, MaybeStorageLive>,
+ ) -> PossibleBorrowerMap<'a, 'tcx> {
+ let mut map = FxHashMap::default();
+ for row in (1..self.body.local_decls.len()).map(mir::Local::from_usize) {
+ if is_copy(cx, self.body.local_decls[row].ty) {
+ continue;
+ }
+
+ let mut borrowers = self.possible_borrower.reachable_from(row, self.body.local_decls.len());
+ borrowers.remove(mir::Local::from_usize(0));
+ if !borrowers.is_empty() {
+ map.insert(row, borrowers);
+ }
+ }
+
+ let bs = BitSet::new_empty(self.body.local_decls.len());
+ PossibleBorrowerMap {
+ map,
+ maybe_live,
+ bitset: (bs.clone(), bs),
+ }
+ }
+}
+
+impl<'a, 'tcx> mir::visit::Visitor<'tcx> for PossibleBorrowerVisitor<'a, 'tcx> {
+ fn visit_assign(&mut self, place: &mir::Place<'tcx>, rvalue: &mir::Rvalue<'_>, _location: mir::Location) {
+ let lhs = place.local;
+ match rvalue {
+ mir::Rvalue::Ref(_, _, borrowed) => {
+ self.possible_borrower.add(borrowed.local, lhs);
+ },
+ other => {
+ if ContainsRegion
+ .visit_ty(place.ty(&self.body.local_decls, self.cx.tcx).ty)
+ .is_continue()
+ {
+ return;
+ }
+ rvalue_locals(other, |rhs| {
+ if lhs != rhs {
+ self.possible_borrower.add(rhs, lhs);
+ }
+ });
+ },
+ }
+ }
+
+ fn visit_terminator(&mut self, terminator: &mir::Terminator<'_>, _loc: mir::Location) {
+ if let mir::TerminatorKind::Call {
+ args,
+ destination: mir::Place { local: dest, .. },
+ ..
+ } = &terminator.kind
+ {
+ // TODO add doc
+ // If the call returns something with lifetimes,
+ // let's conservatively assume the returned value contains lifetime of all the arguments.
+ // For example, given `let y: Foo<'a> = foo(x)`, `y` is considered to be a possible borrower of `x`.
+
+ let mut immutable_borrowers = vec![];
+ let mut mutable_borrowers = vec![];
+
+ for op in args {
+ match op {
+ mir::Operand::Copy(p) | mir::Operand::Move(p) => {
+ if let ty::Ref(_, _, Mutability::Mut) = self.body.local_decls[p.local].ty.kind() {
+ mutable_borrowers.push(p.local);
+ } else {
+ immutable_borrowers.push(p.local);
+ }
+ },
+ mir::Operand::Constant(..) => (),
+ }
+ }
+
+ let mut mutable_variables: Vec<mir::Local> = mutable_borrowers
+ .iter()
+ .filter_map(|r| self.possible_origin.get(r))
+ .flat_map(HybridBitSet::iter)
+ .collect();
+
+ if ContainsRegion.visit_ty(self.body.local_decls[*dest].ty).is_break() {
+ mutable_variables.push(*dest);
+ }
+
+ for y in mutable_variables {
+ for x in &immutable_borrowers {
+ self.possible_borrower.add(*x, y);
+ }
+ for x in &mutable_borrowers {
+ self.possible_borrower.add(*x, y);
+ }
+ }
+ }
+ }
+}
+
+/// Collect possible borrowed for every `&mut` local.
+/// For example, `_1 = &mut _2` generate _1: {_2,...}
+/// Known Problems: not sure all borrowed are tracked
+struct PossibleOriginVisitor<'a, 'tcx> {
+ possible_origin: TransitiveRelation,
+ body: &'a mir::Body<'tcx>,
+}
+
+impl<'a, 'tcx> PossibleOriginVisitor<'a, 'tcx> {
+ fn new(body: &'a mir::Body<'tcx>) -> Self {
+ Self {
+ possible_origin: TransitiveRelation::default(),
+ body,
+ }
+ }
+
+ fn into_map(self, cx: &LateContext<'tcx>) -> FxHashMap<mir::Local, HybridBitSet<mir::Local>> {
+ let mut map = FxHashMap::default();
+ for row in (1..self.body.local_decls.len()).map(mir::Local::from_usize) {
+ if is_copy(cx, self.body.local_decls[row].ty) {
+ continue;
+ }
+
+ let mut borrowers = self.possible_origin.reachable_from(row, self.body.local_decls.len());
+ borrowers.remove(mir::Local::from_usize(0));
+ if !borrowers.is_empty() {
+ map.insert(row, borrowers);
+ }
+ }
+ map
+ }
+}
+
+impl<'a, 'tcx> mir::visit::Visitor<'tcx> for PossibleOriginVisitor<'a, 'tcx> {
+ fn visit_assign(&mut self, place: &mir::Place<'tcx>, rvalue: &mir::Rvalue<'_>, _location: mir::Location) {
+ let lhs = place.local;
+ match rvalue {
+ // Only consider `&mut`, which can modify origin place
+ mir::Rvalue::Ref(_, rustc_middle::mir::BorrowKind::Mut { .. }, borrowed) |
+ // _2: &mut _;
+ // _3 = move _2
+ mir::Rvalue::Use(mir::Operand::Move(borrowed)) |
+ // _3 = move _2 as &mut _;
+ mir::Rvalue::Cast(_, mir::Operand::Move(borrowed), _)
+ => {
+ self.possible_origin.add(lhs, borrowed.local);
+ },
+ _ => {},
+ }
+ }
+}
+
+struct ContainsRegion;
+
+impl TypeVisitor<'_> for ContainsRegion {
+ type BreakTy = ();
+
+ fn visit_region(&mut self, _: ty::Region<'_>) -> ControlFlow<Self::BreakTy> {
+ ControlFlow::BREAK
+ }
+}
+
+fn rvalue_locals(rvalue: &mir::Rvalue<'_>, mut visit: impl FnMut(mir::Local)) {
+ use rustc_middle::mir::Rvalue::{Aggregate, BinaryOp, Cast, CheckedBinaryOp, Repeat, UnaryOp, Use};
+
+ let mut visit_op = |op: &mir::Operand<'_>| match op {
+ mir::Operand::Copy(p) | mir::Operand::Move(p) => visit(p.local),
+ mir::Operand::Constant(..) => (),
+ };
+
+ match rvalue {
+ Use(op) | Repeat(op, _) | Cast(_, op, _) | UnaryOp(_, op) => visit_op(op),
+ Aggregate(_, ops) => ops.iter().for_each(visit_op),
+ BinaryOp(_, box (lhs, rhs)) | CheckedBinaryOp(_, box (lhs, rhs)) => {
+ visit_op(lhs);
+ visit_op(rhs);
+ },
+ _ => (),
+ }
+}
+
+/// Result of `PossibleBorrowerVisitor`.
+struct PossibleBorrowerMap<'a, 'tcx> {
+ /// Mapping `Local -> its possible borrowers`
+ map: FxHashMap<mir::Local, HybridBitSet<mir::Local>>,
+ maybe_live: ResultsCursor<'a, 'tcx, MaybeStorageLive>,
+ // Caches to avoid allocation of `BitSet` on every query
+ bitset: (BitSet<mir::Local>, BitSet<mir::Local>),
+}
+
+impl PossibleBorrowerMap<'_, '_> {
+ /// Returns true if the set of borrowers of `borrowed` living at `at` matches with `borrowers`.
+ fn only_borrowers(&mut self, borrowers: &[mir::Local], borrowed: mir::Local, at: mir::Location) -> bool {
+ self.maybe_live.seek_after_primary_effect(at);
+
+ self.bitset.0.clear();
+ let maybe_live = &mut self.maybe_live;
+ if let Some(bitset) = self.map.get(&borrowed) {
+ for b in bitset.iter().filter(move |b| maybe_live.contains(*b)) {
+ self.bitset.0.insert(b);
+ }
+ } else {
+ return false;
+ }
+
+ self.bitset.1.clear();
+ for b in borrowers {
+ self.bitset.1.insert(*b);
+ }
+
+ self.bitset.0 == self.bitset.1
+ }
+
+ fn local_is_alive_at(&mut self, local: mir::Local, at: mir::Location) -> bool {
+ self.maybe_live.seek_after_primary_effect(at);
+ self.maybe_live.contains(local)
+ }
+}
+
+#[derive(Default)]
+struct TransitiveRelation {
+ relations: FxHashMap<mir::Local, Vec<mir::Local>>,
+}
+impl TransitiveRelation {
+ fn add(&mut self, a: mir::Local, b: mir::Local) {
+ self.relations.entry(a).or_default().push(b);
+ }
+
+ fn reachable_from(&self, a: mir::Local, domain_size: usize) -> HybridBitSet<mir::Local> {
+ let mut seen = HybridBitSet::new_empty(domain_size);
+ let mut stack = vec![a];
+ while let Some(u) = stack.pop() {
+ if let Some(edges) = self.relations.get(&u) {
+ for &v in edges {
+ if seen.insert(v) {
+ stack.push(v);
+ }
+ }
+ }
+ }
+ seen
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-09 16:04:59 +0000