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| 1 | +//! This module analyzes the relationship between the function signature and |
| 2 | +//! the internal dataflow. Specifically, it checks for the following things: |
| 3 | +//! |
| 4 | +//! - Might an owned argument be returned |
| 5 | +//! - Are arguments stored in `&mut` loans |
| 6 | +//! - Are dependent loans returned |
| 7 | +//! - Might a returned loan be `'static` |
| 8 | +//! - Are all returned values const |
| 9 | +//! - Is the unit type returned |
| 10 | +//! - How often do `&mut self` refs need to be `&mut` |
| 11 | +//! - Are all the dependencies from the function signature used. |
| 12 | +
|
| 13 | +#![warn(unused)] |
| 14 | + |
| 15 | +use super::prelude::*; |
| 16 | +use super::{calc_fn_arg_relations, has_mut_ref, visit_body, BodyStats}; |
| 17 | + |
| 18 | +use clippy_utils::ty::for_each_region; |
| 19 | + |
| 20 | +mod pattern; |
| 21 | +pub use pattern::*; |
| 22 | +mod flow; |
| 23 | +use flow::DfWalker; |
| 24 | +use rustc_middle::ty::Region; |
| 25 | + |
| 26 | +#[derive(Debug)] |
| 27 | +pub struct BodyAnalysis<'a, 'tcx> { |
| 28 | + info: &'a AnalysisInfo<'tcx>, |
| 29 | + pats: BTreeSet<BodyPat>, |
| 30 | + data_flow: IndexVec<Local, SmallVec<[MutInfo; 2]>>, |
| 31 | + stats: BodyStats, |
| 32 | +} |
| 33 | + |
| 34 | +/// This indicates an assignment to `to`. In most cases, there is also a `from`. |
| 35 | +#[derive(Debug, Clone)] |
| 36 | +enum MutInfo { |
| 37 | + /// A different place was copied or moved into this one |
| 38 | + Place(Local), |
| 39 | + Const, |
| 40 | + Arg, |
| 41 | + Calc, |
| 42 | + /// This is typical for loans and function calls. |
| 43 | + Dep(Vec<Local>), |
| 44 | + /// A value was constructed from this data |
| 45 | + Ctor(Vec<Local>), |
| 46 | + /// This is not an assignment, but the notification that a mut borrow was created |
| 47 | + Loan(Local), |
| 48 | + MutRef(Local), |
| 49 | +} |
| 50 | + |
| 51 | +impl<'a, 'tcx> BodyAnalysis<'a, 'tcx> { |
| 52 | + fn new(info: &'a AnalysisInfo<'tcx>, arg_ctn: usize) -> Self { |
| 53 | + let mut data_flow: IndexVec<Local, SmallVec<[MutInfo; 2]>> = IndexVec::default(); |
| 54 | + data_flow.resize(info.locals.len(), SmallVec::default()); |
| 55 | + |
| 56 | + (0..arg_ctn).for_each(|idx| data_flow[Local::from_usize(idx + 1)].push(MutInfo::Arg)); |
| 57 | + |
| 58 | + let mut pats = BTreeSet::default(); |
| 59 | + if arg_ctn == 0 { |
| 60 | + pats.insert(BodyPat::NoArguments); |
| 61 | + } |
| 62 | + |
| 63 | + Self { |
| 64 | + info, |
| 65 | + pats, |
| 66 | + data_flow, |
| 67 | + stats: Default::default(), |
| 68 | + } |
| 69 | + } |
| 70 | + |
| 71 | + pub fn run( |
| 72 | + info: &'a AnalysisInfo<'tcx>, |
| 73 | + def_id: LocalDefId, |
| 74 | + hir_sig: &rustc_hir::FnSig<'_>, |
| 75 | + context: BodyContext, |
| 76 | + ) -> (BodyInfo, BTreeSet<BodyPat>) { |
| 77 | + let mut anly = Self::new(info, hir_sig.decl.inputs.len()); |
| 78 | + |
| 79 | + visit_body(&mut anly, info); |
| 80 | + anly.check_fn_relations(def_id); |
| 81 | + |
| 82 | + let body_info = BodyInfo::from_sig(hir_sig, info, context); |
| 83 | + |
| 84 | + anly.stats.arg_relation_possibly_missed_due_generics = |
| 85 | + info.stats.borrow().arg_relation_possibly_missed_due_generics; |
| 86 | + anly.stats.arg_relation_possibly_missed_due_to_late_bounds = |
| 87 | + info.stats.borrow().arg_relation_possibly_missed_due_to_late_bounds; |
| 88 | + info.stats.replace(anly.stats); |
| 89 | + (body_info, anly.pats) |
| 90 | + } |
| 91 | + |
| 92 | + fn check_fn_relations(&mut self, def_id: LocalDefId) { |
| 93 | + let mut rels = calc_fn_arg_relations(self.info.cx.tcx, def_id); |
| 94 | + let return_rels = rels.remove(&RETURN_LOCAL).unwrap_or_default(); |
| 95 | + |
| 96 | + // Argument relations |
| 97 | + for (child, maybe_parents) in &rels { |
| 98 | + self.check_arg_relation(*child, maybe_parents); |
| 99 | + } |
| 100 | + |
| 101 | + self.check_return_relations(&return_rels, def_id); |
| 102 | + } |
| 103 | + |
| 104 | + fn check_return_relations(&mut self, sig_parents: &[Local], def_id: LocalDefId) { |
| 105 | + self.stats.return_relations_signature = sig_parents.len(); |
| 106 | + |
| 107 | + let arg_ctn = self.info.body.arg_count; |
| 108 | + let args: Vec<_> = (0..arg_ctn).map(|i| Local::from(i + 1)).collect(); |
| 109 | + |
| 110 | + let mut checker = DfWalker::new(self.info, &self.data_flow, RETURN_LOCAL, &args); |
| 111 | + checker.walk(); |
| 112 | + |
| 113 | + for arg in &args { |
| 114 | + if checker.found_connection(*arg) { |
| 115 | + // These two branches are mutually exclusive: |
| 116 | + if sig_parents.contains(arg) { |
| 117 | + self.stats.return_relations_found += 1; |
| 118 | + } |
| 119 | + // FIXME: It would be nice if we can say, if an argument was |
| 120 | + // returned, but it feels like all we can say is that there is an connection between |
| 121 | + // this and the other thing else if !self.info.body.local_decls[* |
| 122 | + // arg].ty.is_ref() { println!("Track owned argument returned"); |
| 123 | + // } |
| 124 | + } |
| 125 | + } |
| 126 | + |
| 127 | + // check for static returns |
| 128 | + let mut all_regions_static = true; |
| 129 | + let mut region_count = 0; |
| 130 | + let fn_sig = self.info.cx.tcx.fn_sig(def_id).instantiate_identity().skip_binder(); |
| 131 | + for_each_region(fn_sig.output(), &mut |region: Region<'_>| { |
| 132 | + region_count += 1; |
| 133 | + all_regions_static &= region.is_static(); |
| 134 | + }); |
| 135 | + |
| 136 | + // Check if there can be static returns |
| 137 | + if region_count >= 1 && !all_regions_static { |
| 138 | + let mut pending_return_df = std::mem::take(&mut self.data_flow[RETURN_LOCAL]); |
| 139 | + let mut checked_return_df = SmallVec::with_capacity(pending_return_df.len()); |
| 140 | + // We check for every assignment, if it's constant and therefore static |
| 141 | + while let Some(return_df) = pending_return_df.pop() { |
| 142 | + self.data_flow[RETURN_LOCAL].push(return_df); |
| 143 | + |
| 144 | + let mut checker = DfWalker::new(self.info, &self.data_flow, RETURN_LOCAL, &args); |
| 145 | + checker.walk(); |
| 146 | + let all_const = checker.all_const(); |
| 147 | + |
| 148 | + checked_return_df.push(self.data_flow[RETURN_LOCAL].pop().unwrap()); |
| 149 | + |
| 150 | + if all_const { |
| 151 | + self.pats.insert(BodyPat::ReturnedStaticLoanForNonStatic); |
| 152 | + break; |
| 153 | + } |
| 154 | + } |
| 155 | + |
| 156 | + checked_return_df.append(&mut pending_return_df); |
| 157 | + self.data_flow[RETURN_LOCAL] = checked_return_df; |
| 158 | + } |
| 159 | + } |
| 160 | + |
| 161 | + fn check_arg_relation(&mut self, child: Local, maybe_parents: &[Local]) { |
| 162 | + let mut checker = DfWalker::new(self.info, &self.data_flow, child, maybe_parents); |
| 163 | + checker.walk(); |
| 164 | + |
| 165 | + self.stats.arg_relations_signature += maybe_parents.len(); |
| 166 | + self.stats.arg_relations_found += checker.connection_count(); |
| 167 | + } |
| 168 | +} |
| 169 | + |
| 170 | +impl<'a, 'tcx> Visitor<'tcx> for BodyAnalysis<'a, 'tcx> { |
| 171 | + fn visit_assign(&mut self, target: &Place<'tcx>, rval: &Rvalue<'tcx>, _loc: mir::Location) { |
| 172 | + match rval { |
| 173 | + Rvalue::Ref(_reg, BorrowKind::Fake, _src) => { |
| 174 | + #[allow(clippy::needless_return)] |
| 175 | + return; |
| 176 | + }, |
| 177 | + Rvalue::Ref(_reg, kind, src) => { |
| 178 | + self.stats.ref_stmt_ctn += 1; |
| 179 | + |
| 180 | + let is_mut = matches!(kind, BorrowKind::Mut { .. }); |
| 181 | + if is_mut { |
| 182 | + self.data_flow[src.local].push(MutInfo::MutRef(target.local)); |
| 183 | + } |
| 184 | + if matches!(src.projection.as_slice(), [mir::PlaceElem::Deref]) { |
| 185 | + // &(*_1) => Copy |
| 186 | + self.data_flow[target.local].push(MutInfo::Place(src.local)); |
| 187 | + return; |
| 188 | + } |
| 189 | + |
| 190 | + // _1 = &_2 => simple loan |
| 191 | + self.data_flow[target.local].push(MutInfo::Loan(src.local)); |
| 192 | + }, |
| 193 | + Rvalue::Cast(_, op, _) | Rvalue::Use(op) => { |
| 194 | + let event = match &op { |
| 195 | + Operand::Constant(_) => MutInfo::Const, |
| 196 | + Operand::Copy(from) | Operand::Move(from) => MutInfo::Place(from.local), |
| 197 | + }; |
| 198 | + self.data_flow[target.local].push(event); |
| 199 | + }, |
| 200 | + Rvalue::CopyForDeref(from) => { |
| 201 | + self.data_flow[target.local].push(MutInfo::Place(from.local)); |
| 202 | + }, |
| 203 | + Rvalue::Repeat(op, _) => { |
| 204 | + let event = match &op { |
| 205 | + Operand::Constant(_) => MutInfo::Const, |
| 206 | + Operand::Copy(from) | Operand::Move(from) => MutInfo::Ctor(vec![from.local]), |
| 207 | + }; |
| 208 | + self.data_flow[target.local].push(event); |
| 209 | + }, |
| 210 | + // Constructed Values |
| 211 | + Rvalue::Aggregate(_, fields) => { |
| 212 | + let args = fields |
| 213 | + .iter() |
| 214 | + .filter_map(rustc_middle::mir::Operand::place) |
| 215 | + .map(|place| place.local) |
| 216 | + .collect(); |
| 217 | + self.data_flow[target.local].push(MutInfo::Ctor(args)); |
| 218 | + }, |
| 219 | + // Casts should depend on the input data |
| 220 | + Rvalue::ThreadLocalRef(_) |
| 221 | + | Rvalue::NullaryOp(_, _) |
| 222 | + | Rvalue::AddressOf(_, _) |
| 223 | + | Rvalue::Discriminant(_) |
| 224 | + | Rvalue::ShallowInitBox(_, _) |
| 225 | + | Rvalue::Len(_) |
| 226 | + | Rvalue::BinaryOp(_, _) |
| 227 | + | Rvalue::UnaryOp(_, _) |
| 228 | + | Rvalue::CheckedBinaryOp(_, _) => { |
| 229 | + self.data_flow[target.local].push(MutInfo::Calc); |
| 230 | + }, |
| 231 | + } |
| 232 | + } |
| 233 | + |
| 234 | + fn visit_terminator(&mut self, term: &Terminator<'tcx>, loc: Location) { |
| 235 | + let TerminatorKind::Call { |
| 236 | + destination: dest, |
| 237 | + args, |
| 238 | + .. |
| 239 | + } = &term.kind |
| 240 | + else { |
| 241 | + return; |
| 242 | + }; |
| 243 | + |
| 244 | + for arg in args { |
| 245 | + if let Some(place) = arg.node.place() { |
| 246 | + let ty = self.info.body.local_decls[place.local].ty; |
| 247 | + if has_mut_ref(ty) { |
| 248 | + self.data_flow[place.local].push(MutInfo::Calc); |
| 249 | + } |
| 250 | + } |
| 251 | + } |
| 252 | + |
| 253 | + assert!(dest.just_local()); |
| 254 | + self.data_flow[dest.local].push(MutInfo::Calc); |
| 255 | + |
| 256 | + let rels = &self.info.terms[&loc.block]; |
| 257 | + for (target, sources) in rels { |
| 258 | + self.data_flow[*target].push(MutInfo::Dep(sources.clone())); |
| 259 | + } |
| 260 | + } |
| 261 | +} |
| 262 | + |
| 263 | +pub(crate) fn update_pats_from_stats(pats: &mut BTreeSet<BodyPat>, info: &AnalysisInfo<'_>) { |
| 264 | + let stats = info.stats.borrow(); |
| 265 | + |
| 266 | + if stats.ref_stmt_ctn > 0 { |
| 267 | + pats.insert(BodyPat::Borrow); |
| 268 | + } |
| 269 | + |
| 270 | + if stats.owned.named_borrow_count > 0 { |
| 271 | + pats.insert(BodyPat::OwnedNamedBorrow); |
| 272 | + } |
| 273 | + if stats.owned.named_borrow_mut_count > 0 { |
| 274 | + pats.insert(BodyPat::OwnedNamedBorrowMut); |
| 275 | + } |
| 276 | + |
| 277 | + if stats.owned.arg_borrow_count > 0 { |
| 278 | + pats.insert(BodyPat::OwnedArgBorrow); |
| 279 | + } |
| 280 | + if stats.owned.arg_borrow_mut_count > 0 { |
| 281 | + pats.insert(BodyPat::OwnedArgBorrowMut); |
| 282 | + } |
| 283 | + |
| 284 | + if stats.owned.two_phased_borrows > 0 { |
| 285 | + pats.insert(BodyPat::OwnedTwoPhaseBorrow); |
| 286 | + } |
| 287 | + |
| 288 | + if stats.owned.borrowed_for_closure_count > 0 { |
| 289 | + pats.insert(BodyPat::OwnedClosureBorrow); |
| 290 | + } |
| 291 | + if stats.owned.borrowed_mut_for_closure_count > 0 { |
| 292 | + pats.insert(BodyPat::OwnedClosureBorrowMut); |
| 293 | + } |
| 294 | +} |
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