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Commit | Line | Data |
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9fa01778 | 1 | //! A classic liveness analysis based on dataflow over the AST. Computes, |
1a4d82fc | 2 | //! for each local variable in a function, whether that variable is live |
9fa01778 XL |
3 | //! at a given point. Program execution points are identified by their |
4 | //! IDs. | |
1a4d82fc JJ |
5 | //! |
6 | //! # Basic idea | |
7 | //! | |
9fa01778 | 8 | //! The basic model is that each local variable is assigned an index. We |
1a4d82fc | 9 | //! represent sets of local variables using a vector indexed by this |
9fa01778 XL |
10 | //! index. The value in the vector is either 0, indicating the variable |
11 | //! is dead, or the ID of an expression that uses the variable. | |
1a4d82fc | 12 | //! |
9fa01778 XL |
13 | //! We conceptually walk over the AST in reverse execution order. If we |
14 | //! find a use of a variable, we add it to the set of live variables. If | |
1a4d82fc | 15 | //! we find an assignment to a variable, we remove it from the set of live |
9fa01778 XL |
16 | //! variables. When we have to merge two flows, we take the union of |
17 | //! those two flows -- if the variable is live on both paths, we simply | |
18 | //! pick one ID. In the event of loops, we continue doing this until a | |
1a4d82fc JJ |
19 | //! fixed point is reached. |
20 | //! | |
21 | //! ## Checking initialization | |
22 | //! | |
9fa01778 XL |
23 | //! At the function entry point, all variables must be dead. If this is |
24 | //! not the case, we can report an error using the ID found in the set of | |
1a4d82fc JJ |
25 | //! live variables, which identifies a use of the variable which is not |
26 | //! dominated by an assignment. | |
27 | //! | |
28 | //! ## Checking moves | |
29 | //! | |
30 | //! After each explicit move, the variable must be dead. | |
31 | //! | |
32 | //! ## Computing last uses | |
33 | //! | |
34 | //! Any use of the variable where the variable is dead afterwards is a | |
35 | //! last use. | |
36 | //! | |
37 | //! # Implementation details | |
38 | //! | |
39 | //! The actual implementation contains two (nested) walks over the AST. | |
40 | //! The outer walk has the job of building up the ir_maps instance for the | |
9fa01778 | 41 | //! enclosing function. On the way down the tree, it identifies those AST |
1a4d82fc | 42 | //! nodes and variable IDs that will be needed for the liveness analysis |
9fa01778 XL |
43 | //! and assigns them contiguous IDs. The liveness ID for an AST node is |
44 | //! called a `live_node` (it's a newtype'd `u32`) and the ID for a variable | |
45 | //! is called a `variable` (another newtype'd `u32`). | |
1a4d82fc JJ |
46 | //! |
47 | //! On the way back up the tree, as we are about to exit from a function | |
9fa01778 | 48 | //! declaration we allocate a `liveness` instance. Now that we know |
1a4d82fc | 49 | //! precisely how many nodes and variables we need, we can allocate all |
9fa01778 | 50 | //! the various arrays that we will need to precisely the right size. We then |
1a4d82fc JJ |
51 | //! perform the actual propagation on the `liveness` instance. |
52 | //! | |
53 | //! This propagation is encoded in the various `propagate_through_*()` | |
9fa01778 | 54 | //! methods. It effectively does a reverse walk of the AST; whenever we |
1a4d82fc JJ |
55 | //! reach a loop node, we iterate until a fixed point is reached. |
56 | //! | |
0bf4aa26 | 57 | //! ## The `RWU` struct |
1a4d82fc JJ |
58 | //! |
59 | //! At each live node `N`, we track three pieces of information for each | |
0bf4aa26 | 60 | //! variable `V` (these are encapsulated in the `RWU` struct): |
1a4d82fc JJ |
61 | //! |
62 | //! - `reader`: the `LiveNode` ID of some node which will read the value | |
9fa01778 | 63 | //! that `V` holds on entry to `N`. Formally: a node `M` such |
1a4d82fc | 64 | //! that there exists a path `P` from `N` to `M` where `P` does not |
1b1a35ee | 65 | //! write `V`. If the `reader` is `None`, then the current |
1a4d82fc JJ |
66 | //! value will never be read (the variable is dead, essentially). |
67 | //! | |
68 | //! - `writer`: the `LiveNode` ID of some node which will write the | |
9fa01778 | 69 | //! variable `V` and which is reachable from `N`. Formally: a node `M` |
1a4d82fc | 70 | //! such that there exists a path `P` from `N` to `M` and `M` writes |
1b1a35ee | 71 | //! `V`. If the `writer` is `None`, then there is no writer |
1a4d82fc JJ |
72 | //! of `V` that follows `N`. |
73 | //! | |
9fa01778 | 74 | //! - `used`: a boolean value indicating whether `V` is *used*. We |
1a4d82fc | 75 | //! distinguish a *read* from a *use* in that a *use* is some read that |
9fa01778 XL |
76 | //! is not just used to generate a new value. For example, `x += 1` is |
77 | //! a read but not a use. This is used to generate better warnings. | |
1a4d82fc | 78 | //! |
f9f354fc | 79 | //! ## Special nodes and variables |
1a4d82fc | 80 | //! |
f9f354fc | 81 | //! We generate various special nodes for various, well, special purposes. |
1b1a35ee | 82 | //! These are described in the `Liveness` struct. |
b7449926 | 83 | |
1a4d82fc JJ |
84 | use self::LiveNodeKind::*; |
85 | use self::VarKind::*; | |
86 | ||
3dfed10e | 87 | use rustc_ast::InlineAsmOptions; |
e74abb32 | 88 | use rustc_data_structures::fx::FxIndexMap; |
dfeec247 XL |
89 | use rustc_errors::Applicability; |
90 | use rustc_hir as hir; | |
91 | use rustc_hir::def::*; | |
f035d41b | 92 | use rustc_hir::def_id::LocalDefId; |
1b1a35ee XL |
93 | use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor}; |
94 | use rustc_hir::{Expr, HirId, HirIdMap, HirIdSet}; | |
95 | use rustc_index::vec::IndexVec; | |
ba9703b0 XL |
96 | use rustc_middle::hir::map::Map; |
97 | use rustc_middle::ty::query::Providers; | |
1b1a35ee | 98 | use rustc_middle::ty::{self, DefIdTree, TyCtxt}; |
ba9703b0 | 99 | use rustc_session::lint; |
1b1a35ee | 100 | use rustc_span::symbol::{kw, sym, Symbol}; |
dfeec247 | 101 | use rustc_span::Span; |
dfeec247 | 102 | |
e74abb32 | 103 | use std::collections::VecDeque; |
c34b1796 | 104 | use std::io; |
dfeec247 | 105 | use std::io::prelude::*; |
c34b1796 | 106 | use std::rc::Rc; |
e9174d1e | 107 | |
1b1a35ee XL |
108 | rustc_index::newtype_index! { |
109 | pub struct Variable { | |
110 | DEBUG_FORMAT = "v({})", | |
dfeec247 | 111 | } |
1a4d82fc JJ |
112 | } |
113 | ||
1b1a35ee XL |
114 | rustc_index::newtype_index! { |
115 | pub struct LiveNode { | |
116 | DEBUG_FORMAT = "ln({})", | |
dfeec247 | 117 | } |
1a4d82fc JJ |
118 | } |
119 | ||
c34b1796 | 120 | #[derive(Copy, Clone, PartialEq, Debug)] |
223e47cc | 121 | enum LiveNodeKind { |
48663c56 | 122 | UpvarNode(Span), |
1a4d82fc JJ |
123 | ExprNode(Span), |
124 | VarDefNode(Span), | |
f9f354fc | 125 | ClosureNode, |
dfeec247 | 126 | ExitNode, |
223e47cc LB |
127 | } |
128 | ||
dc9dc135 | 129 | fn live_node_kind_to_string(lnk: LiveNodeKind, tcx: TyCtxt<'_>) -> String { |
74b04a01 | 130 | let sm = tcx.sess.source_map(); |
223e47cc | 131 | match lnk { |
74b04a01 XL |
132 | UpvarNode(s) => format!("Upvar node [{}]", sm.span_to_string(s)), |
133 | ExprNode(s) => format!("Expr node [{}]", sm.span_to_string(s)), | |
134 | VarDefNode(s) => format!("Var def node [{}]", sm.span_to_string(s)), | |
f9f354fc | 135 | ClosureNode => "Closure node".to_owned(), |
0bf4aa26 | 136 | ExitNode => "Exit node".to_owned(), |
223e47cc LB |
137 | } |
138 | } | |
139 | ||
f035d41b | 140 | fn check_mod_liveness(tcx: TyCtxt<'_>, module_def_id: LocalDefId) { |
1b1a35ee | 141 | tcx.hir().visit_item_likes_in_module(module_def_id, &mut IrMaps::new(tcx).as_deep_visitor()); |
9fa01778 XL |
142 | } |
143 | ||
f035d41b | 144 | pub fn provide(providers: &mut Providers) { |
dfeec247 | 145 | *providers = Providers { check_mod_liveness, ..*providers }; |
223e47cc LB |
146 | } |
147 | ||
223e47cc LB |
148 | // ______________________________________________________________________ |
149 | // Creating ir_maps | |
150 | // | |
151 | // This is the first pass and the one that drives the main | |
152 | // computation. It walks up and down the IR once. On the way down, | |
153 | // we count for each function the number of variables as well as | |
154 | // liveness nodes. A liveness node is basically an expression or | |
155 | // capture clause that does something of interest: either it has | |
156 | // interesting control flow or it uses/defines a local variable. | |
157 | // | |
158 | // On the way back up, at each function node we create liveness sets | |
159 | // (we now know precisely how big to make our various vectors and so | |
160 | // forth) and then do the data-flow propagation to compute the set | |
161 | // of live variables at each program point. | |
162 | // | |
163 | // Finally, we run back over the IR one last time and, using the | |
164 | // computed liveness, check various safety conditions. For example, | |
165 | // there must be no live nodes at the definition site for a variable | |
166 | // unless it has an initializer. Similarly, each non-mutable local | |
167 | // variable must not be assigned if there is some successor | |
168 | // assignment. And so forth. | |
169 | ||
223e47cc LB |
170 | struct CaptureInfo { |
171 | ln: LiveNode, | |
dfeec247 | 172 | var_hid: HirId, |
223e47cc LB |
173 | } |
174 | ||
c34b1796 | 175 | #[derive(Copy, Clone, Debug)] |
223e47cc | 176 | struct LocalInfo { |
94b46f34 | 177 | id: HirId, |
f9f354fc | 178 | name: Symbol, |
2c00a5a8 | 179 | is_shorthand: bool, |
223e47cc LB |
180 | } |
181 | ||
c34b1796 | 182 | #[derive(Copy, Clone, Debug)] |
223e47cc | 183 | enum VarKind { |
f9f354fc | 184 | Param(HirId, Symbol), |
223e47cc | 185 | Local(LocalInfo), |
f9f354fc | 186 | Upvar(HirId, Symbol), |
223e47cc LB |
187 | } |
188 | ||
dc9dc135 XL |
189 | struct IrMaps<'tcx> { |
190 | tcx: TyCtxt<'tcx>, | |
94b46f34 XL |
191 | live_node_map: HirIdMap<LiveNode>, |
192 | variable_map: HirIdMap<Variable>, | |
532ac7d7 | 193 | capture_info_map: HirIdMap<Rc<Vec<CaptureInfo>>>, |
1b1a35ee XL |
194 | var_kinds: IndexVec<Variable, VarKind>, |
195 | lnks: IndexVec<LiveNode, LiveNodeKind>, | |
223e47cc LB |
196 | } |
197 | ||
dc9dc135 | 198 | impl IrMaps<'tcx> { |
1b1a35ee | 199 | fn new(tcx: TyCtxt<'tcx>) -> IrMaps<'tcx> { |
1a4d82fc | 200 | IrMaps { |
041b39d2 | 201 | tcx, |
a1dfa0c6 XL |
202 | live_node_map: HirIdMap::default(), |
203 | variable_map: HirIdMap::default(), | |
204 | capture_info_map: Default::default(), | |
1b1a35ee XL |
205 | var_kinds: IndexVec::new(), |
206 | lnks: IndexVec::new(), | |
1a4d82fc | 207 | } |
223e47cc | 208 | } |
223e47cc | 209 | |
1a4d82fc | 210 | fn add_live_node(&mut self, lnk: LiveNodeKind) -> LiveNode { |
1b1a35ee | 211 | let ln = self.lnks.push(lnk); |
223e47cc | 212 | |
dfeec247 | 213 | debug!("{:?} is of kind {}", ln, live_node_kind_to_string(lnk, self.tcx)); |
223e47cc LB |
214 | |
215 | ln | |
216 | } | |
217 | ||
94b46f34 | 218 | fn add_live_node_for_node(&mut self, hir_id: HirId, lnk: LiveNodeKind) { |
223e47cc | 219 | let ln = self.add_live_node(lnk); |
94b46f34 | 220 | self.live_node_map.insert(hir_id, ln); |
223e47cc | 221 | |
94b46f34 | 222 | debug!("{:?} is node {:?}", ln, hir_id); |
223e47cc LB |
223 | } |
224 | ||
1a4d82fc | 225 | fn add_variable(&mut self, vk: VarKind) -> Variable { |
1b1a35ee | 226 | let v = self.var_kinds.push(vk); |
223e47cc LB |
227 | |
228 | match vk { | |
f9f354fc | 229 | Local(LocalInfo { id: node_id, .. }) | Param(node_id, _) | Upvar(node_id, _) => { |
223e47cc | 230 | self.variable_map.insert(node_id, v); |
dfeec247 | 231 | } |
223e47cc LB |
232 | } |
233 | ||
1a4d82fc | 234 | debug!("{:?} is {:?}", v, vk); |
223e47cc LB |
235 | |
236 | v | |
237 | } | |
238 | ||
94b46f34 XL |
239 | fn variable(&self, hir_id: HirId, span: Span) -> Variable { |
240 | match self.variable_map.get(&hir_id) { | |
54a0048b SL |
241 | Some(&var) => var, |
242 | None => { | |
94b46f34 | 243 | span_bug!(span, "no variable registered for id {:?}", hir_id); |
54a0048b | 244 | } |
223e47cc LB |
245 | } |
246 | } | |
247 | ||
1b1a35ee XL |
248 | fn variable_name(&self, var: Variable) -> Symbol { |
249 | match self.var_kinds[var] { | |
250 | Local(LocalInfo { name, .. }) | Param(_, name) | Upvar(_, name) => name, | |
223e47cc LB |
251 | } |
252 | } | |
253 | ||
2c00a5a8 | 254 | fn variable_is_shorthand(&self, var: Variable) -> bool { |
1b1a35ee | 255 | match self.var_kinds[var] { |
2c00a5a8 | 256 | Local(LocalInfo { is_shorthand, .. }) => is_shorthand, |
f9f354fc | 257 | Param(..) | Upvar(..) => false, |
2c00a5a8 XL |
258 | } |
259 | } | |
260 | ||
532ac7d7 XL |
261 | fn set_captures(&mut self, hir_id: HirId, cs: Vec<CaptureInfo>) { |
262 | self.capture_info_map.insert(hir_id, Rc::new(cs)); | |
223e47cc LB |
263 | } |
264 | ||
1b1a35ee XL |
265 | fn add_from_pat(&mut self, pat: &hir::Pat<'tcx>) { |
266 | // For struct patterns, take note of which fields used shorthand | |
267 | // (`x` rather than `x: x`). | |
268 | let mut shorthand_field_ids = HirIdSet::default(); | |
269 | let mut pats = VecDeque::new(); | |
270 | pats.push_back(pat); | |
271 | while let Some(pat) = pats.pop_front() { | |
272 | use rustc_hir::PatKind::*; | |
273 | match &pat.kind { | |
274 | Binding(.., inner_pat) => { | |
275 | pats.extend(inner_pat.iter()); | |
276 | } | |
277 | Struct(_, fields, _) => { | |
278 | let ids = fields.iter().filter(|f| f.is_shorthand).map(|f| f.pat.hir_id); | |
279 | shorthand_field_ids.extend(ids); | |
280 | } | |
281 | Ref(inner_pat, _) | Box(inner_pat) => { | |
282 | pats.push_back(inner_pat); | |
283 | } | |
284 | TupleStruct(_, inner_pats, _) | Tuple(inner_pats, _) | Or(inner_pats) => { | |
285 | pats.extend(inner_pats.iter()); | |
286 | } | |
287 | Slice(pre_pats, inner_pat, post_pats) => { | |
288 | pats.extend(pre_pats.iter()); | |
289 | pats.extend(inner_pat.iter()); | |
290 | pats.extend(post_pats.iter()); | |
291 | } | |
292 | _ => {} | |
293 | } | |
294 | } | |
295 | ||
296 | pat.each_binding(|_, hir_id, _, ident| { | |
297 | self.add_live_node_for_node(hir_id, VarDefNode(ident.span)); | |
298 | self.add_variable(Local(LocalInfo { | |
299 | id: hir_id, | |
300 | name: ident.name, | |
301 | is_shorthand: shorthand_field_ids.contains(&hir_id), | |
302 | })); | |
303 | }); | |
223e47cc | 304 | } |
1a4d82fc | 305 | } |
223e47cc | 306 | |
1b1a35ee XL |
307 | impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> { |
308 | type Map = Map<'tcx>; | |
309 | ||
310 | fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { | |
311 | NestedVisitorMap::OnlyBodies(self.tcx.hir()) | |
83c7162d XL |
312 | } |
313 | ||
1b1a35ee XL |
314 | fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) { |
315 | debug!("visit_body {:?}", body.id()); | |
223e47cc | 316 | |
1b1a35ee XL |
317 | // swap in a new set of IR maps for this body |
318 | let mut maps = IrMaps::new(self.tcx); | |
319 | let hir_id = maps.tcx.hir().body_owner(body.id()); | |
320 | let def_id = maps.tcx.hir().local_def_id(hir_id); | |
32a655c1 | 321 | |
1b1a35ee XL |
322 | // Don't run unused pass for #[derive()] |
323 | if let Some(parent) = self.tcx.parent(def_id.to_def_id()) { | |
324 | if let DefKind::Impl = self.tcx.def_kind(parent.expect_local()) { | |
325 | if self.tcx.has_attr(parent, sym::automatically_derived) { | |
326 | return; | |
327 | } | |
328 | } | |
f9f354fc | 329 | } |
1b1a35ee XL |
330 | |
331 | if let Some(upvars) = maps.tcx.upvars_mentioned(def_id) { | |
332 | for (&var_hir_id, _upvar) in upvars { | |
333 | let var_name = maps.tcx.hir().name(var_hir_id); | |
334 | maps.add_variable(Upvar(var_hir_id, var_name)); | |
335 | } | |
336 | } | |
337 | ||
338 | // gather up the various local variables, significant expressions, | |
339 | // and so forth: | |
340 | intravisit::walk_body(&mut maps, body); | |
341 | ||
342 | // compute liveness | |
343 | let mut lsets = Liveness::new(&mut maps, def_id); | |
344 | let entry_ln = lsets.compute(&body, hir_id); | |
345 | lsets.log_liveness(entry_ln, body.id().hir_id); | |
346 | ||
347 | // check for various error conditions | |
348 | lsets.visit_body(body); | |
349 | lsets.warn_about_unused_upvars(entry_ln); | |
350 | lsets.warn_about_unused_args(body, entry_ln); | |
351 | } | |
352 | ||
353 | fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) { | |
354 | self.add_from_pat(&local.pat); | |
355 | intravisit::walk_local(self, local); | |
356 | } | |
357 | ||
358 | fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) { | |
359 | self.add_from_pat(&arm.pat); | |
360 | intravisit::walk_arm(self, arm); | |
f9f354fc XL |
361 | } |
362 | ||
1b1a35ee | 363 | fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) { |
e74abb32 | 364 | let is_shorthand = match param.pat.kind { |
dfeec247 | 365 | rustc_hir::PatKind::Struct(..) => true, |
532ac7d7 XL |
366 | _ => false, |
367 | }; | |
e1599b0c | 368 | param.pat.each_binding(|_bm, hir_id, _x, ident| { |
532ac7d7 | 369 | let var = if is_shorthand { |
dfeec247 | 370 | Local(LocalInfo { id: hir_id, name: ident.name, is_shorthand: true }) |
532ac7d7 | 371 | } else { |
e1599b0c | 372 | Param(hir_id, ident.name) |
532ac7d7 | 373 | }; |
1b1a35ee XL |
374 | self.add_variable(var); |
375 | }); | |
376 | intravisit::walk_param(self, param); | |
dfeec247 | 377 | } |
223e47cc | 378 | |
1b1a35ee XL |
379 | fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { |
380 | match expr.kind { | |
381 | // live nodes required for uses or definitions of variables: | |
382 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { | |
383 | debug!("expr {}: path that leads to {:?}", expr.hir_id, path.res); | |
384 | if let Res::Local(_var_hir_id) = path.res { | |
385 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span)); | |
386 | } | |
387 | intravisit::walk_expr(self, expr); | |
94b46f34 | 388 | } |
1b1a35ee XL |
389 | hir::ExprKind::Closure(..) => { |
390 | // Interesting control flow (for loops can contain labeled | |
391 | // breaks or continues) | |
392 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span)); | |
393 | ||
394 | // Make a live_node for each captured variable, with the span | |
395 | // being the location that the variable is used. This results | |
396 | // in better error messages than just pointing at the closure | |
397 | // construction site. | |
398 | let mut call_caps = Vec::new(); | |
399 | let closure_def_id = self.tcx.hir().local_def_id(expr.hir_id); | |
400 | if let Some(upvars) = self.tcx.upvars_mentioned(closure_def_id) { | |
401 | call_caps.extend(upvars.iter().map(|(&var_id, upvar)| { | |
402 | let upvar_ln = self.add_live_node(UpvarNode(upvar.span)); | |
403 | CaptureInfo { ln: upvar_ln, var_hid: var_id } | |
404 | })); | |
405 | } | |
406 | self.set_captures(expr.hir_id, call_caps); | |
407 | intravisit::walk_expr(self, expr); | |
94b46f34 | 408 | } |
94b46f34 | 409 | |
1b1a35ee XL |
410 | // live nodes required for interesting control flow: |
411 | hir::ExprKind::Match(..) | hir::ExprKind::Loop(..) => { | |
412 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span)); | |
413 | intravisit::walk_expr(self, expr); | |
dc9dc135 | 414 | } |
1b1a35ee XL |
415 | hir::ExprKind::Binary(op, ..) if op.node.is_lazy() => { |
416 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span)); | |
417 | intravisit::walk_expr(self, expr); | |
dfeec247 | 418 | } |
dfeec247 | 419 | |
1b1a35ee XL |
420 | // otherwise, live nodes are not required: |
421 | hir::ExprKind::Index(..) | |
422 | | hir::ExprKind::Field(..) | |
423 | | hir::ExprKind::Array(..) | |
424 | | hir::ExprKind::Call(..) | |
425 | | hir::ExprKind::MethodCall(..) | |
426 | | hir::ExprKind::Tup(..) | |
427 | | hir::ExprKind::Binary(..) | |
428 | | hir::ExprKind::AddrOf(..) | |
429 | | hir::ExprKind::Cast(..) | |
430 | | hir::ExprKind::DropTemps(..) | |
431 | | hir::ExprKind::Unary(..) | |
432 | | hir::ExprKind::Break(..) | |
433 | | hir::ExprKind::Continue(_) | |
434 | | hir::ExprKind::Lit(_) | |
29967ef6 | 435 | | hir::ExprKind::ConstBlock(..) |
1b1a35ee XL |
436 | | hir::ExprKind::Ret(..) |
437 | | hir::ExprKind::Block(..) | |
438 | | hir::ExprKind::Assign(..) | |
439 | | hir::ExprKind::AssignOp(..) | |
440 | | hir::ExprKind::Struct(..) | |
441 | | hir::ExprKind::Repeat(..) | |
442 | | hir::ExprKind::InlineAsm(..) | |
443 | | hir::ExprKind::LlvmInlineAsm(..) | |
444 | | hir::ExprKind::Box(..) | |
445 | | hir::ExprKind::Yield(..) | |
446 | | hir::ExprKind::Type(..) | |
447 | | hir::ExprKind::Err | |
448 | | hir::ExprKind::Path(hir::QPath::TypeRelative(..)) | |
449 | | hir::ExprKind::Path(hir::QPath::LangItem(..)) => { | |
450 | intravisit::walk_expr(self, expr); | |
451 | } | |
48663c56 | 452 | } |
223e47cc LB |
453 | } |
454 | } | |
455 | ||
456 | // ______________________________________________________________________ | |
457 | // Computing liveness sets | |
458 | // | |
459 | // Actually we compute just a bit more than just liveness, but we use | |
460 | // the same basic propagation framework in all cases. | |
461 | ||
1a4d82fc | 462 | #[derive(Clone, Copy)] |
0bf4aa26 | 463 | struct RWU { |
1b1a35ee XL |
464 | reader: Option<LiveNode>, |
465 | writer: Option<LiveNode>, | |
dfeec247 | 466 | used: bool, |
223e47cc LB |
467 | } |
468 | ||
0bf4aa26 XL |
469 | /// Conceptually, this is like a `Vec<RWU>`. But the number of `RWU`s can get |
470 | /// very large, so it uses a more compact representation that takes advantage | |
471 | /// of the fact that when the number of `RWU`s is large, most of them have an | |
472 | /// invalid reader and an invalid writer. | |
473 | struct RWUTable { | |
474 | /// Each entry in `packed_rwus` is either INV_INV_FALSE, INV_INV_TRUE, or | |
475 | /// an index into `unpacked_rwus`. In the common cases, this compacts the | |
476 | /// 65 bits of data into 32; in the uncommon cases, it expands the 65 bits | |
477 | /// in 96. | |
478 | /// | |
0731742a | 479 | /// More compact representations are possible -- e.g., use only 2 bits per |
0bf4aa26 XL |
480 | /// packed `RWU` and make the secondary table a HashMap that maps from |
481 | /// indices to `RWU`s -- but this one strikes a good balance between size | |
482 | /// and speed. | |
483 | packed_rwus: Vec<u32>, | |
484 | unpacked_rwus: Vec<RWU>, | |
485 | } | |
486 | ||
1b1a35ee | 487 | // A constant representing `RWU { reader: None; writer: None; used: false }`. |
0bf4aa26 XL |
488 | const INV_INV_FALSE: u32 = u32::MAX; |
489 | ||
1b1a35ee | 490 | // A constant representing `RWU { reader: None; writer: None; used: true }`. |
0bf4aa26 XL |
491 | const INV_INV_TRUE: u32 = u32::MAX - 1; |
492 | ||
493 | impl RWUTable { | |
494 | fn new(num_rwus: usize) -> RWUTable { | |
dfeec247 | 495 | Self { packed_rwus: vec![INV_INV_FALSE; num_rwus], unpacked_rwus: vec![] } |
0bf4aa26 XL |
496 | } |
497 | ||
498 | fn get(&self, idx: usize) -> RWU { | |
499 | let packed_rwu = self.packed_rwus[idx]; | |
500 | match packed_rwu { | |
1b1a35ee XL |
501 | INV_INV_FALSE => RWU { reader: None, writer: None, used: false }, |
502 | INV_INV_TRUE => RWU { reader: None, writer: None, used: true }, | |
0bf4aa26 XL |
503 | _ => self.unpacked_rwus[packed_rwu as usize], |
504 | } | |
505 | } | |
506 | ||
1b1a35ee | 507 | fn get_reader(&self, idx: usize) -> Option<LiveNode> { |
0bf4aa26 XL |
508 | let packed_rwu = self.packed_rwus[idx]; |
509 | match packed_rwu { | |
1b1a35ee | 510 | INV_INV_FALSE | INV_INV_TRUE => None, |
0bf4aa26 XL |
511 | _ => self.unpacked_rwus[packed_rwu as usize].reader, |
512 | } | |
513 | } | |
514 | ||
1b1a35ee | 515 | fn get_writer(&self, idx: usize) -> Option<LiveNode> { |
0bf4aa26 XL |
516 | let packed_rwu = self.packed_rwus[idx]; |
517 | match packed_rwu { | |
1b1a35ee | 518 | INV_INV_FALSE | INV_INV_TRUE => None, |
0bf4aa26 XL |
519 | _ => self.unpacked_rwus[packed_rwu as usize].writer, |
520 | } | |
521 | } | |
522 | ||
523 | fn get_used(&self, idx: usize) -> bool { | |
524 | let packed_rwu = self.packed_rwus[idx]; | |
525 | match packed_rwu { | |
526 | INV_INV_FALSE => false, | |
527 | INV_INV_TRUE => true, | |
528 | _ => self.unpacked_rwus[packed_rwu as usize].used, | |
529 | } | |
530 | } | |
531 | ||
532 | #[inline] | |
533 | fn copy_packed(&mut self, dst_idx: usize, src_idx: usize) { | |
534 | self.packed_rwus[dst_idx] = self.packed_rwus[src_idx]; | |
535 | } | |
536 | ||
537 | fn assign_unpacked(&mut self, idx: usize, rwu: RWU) { | |
1b1a35ee | 538 | if rwu.reader == None && rwu.writer == None { |
0bf4aa26 XL |
539 | // When we overwrite an indexing entry in `self.packed_rwus` with |
540 | // `INV_INV_{TRUE,FALSE}` we don't remove the corresponding entry | |
541 | // from `self.unpacked_rwus`; it's not worth the effort, and we | |
542 | // can't have entries shifting around anyway. | |
dfeec247 | 543 | self.packed_rwus[idx] = if rwu.used { INV_INV_TRUE } else { INV_INV_FALSE } |
0bf4aa26 XL |
544 | } else { |
545 | // Add a new RWU to `unpacked_rwus` and make `packed_rwus[idx]` | |
546 | // point to it. | |
547 | self.packed_rwus[idx] = self.unpacked_rwus.len() as u32; | |
548 | self.unpacked_rwus.push(rwu); | |
549 | } | |
550 | } | |
551 | ||
552 | fn assign_inv_inv(&mut self, idx: usize) { | |
dfeec247 | 553 | self.packed_rwus[idx] = if self.get_used(idx) { INV_INV_TRUE } else { INV_INV_FALSE }; |
223e47cc LB |
554 | } |
555 | } | |
556 | ||
c34b1796 AL |
557 | const ACC_READ: u32 = 1; |
558 | const ACC_WRITE: u32 = 2; | |
559 | const ACC_USE: u32 = 4; | |
223e47cc | 560 | |
dc9dc135 XL |
561 | struct Liveness<'a, 'tcx> { |
562 | ir: &'a mut IrMaps<'tcx>, | |
1b1a35ee | 563 | body_owner: LocalDefId, |
3dfed10e | 564 | typeck_results: &'a ty::TypeckResults<'tcx>, |
ba9703b0 | 565 | param_env: ty::ParamEnv<'tcx>, |
1b1a35ee XL |
566 | upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>, |
567 | successors: IndexVec<LiveNode, Option<LiveNode>>, | |
0bf4aa26 | 568 | rwu_table: RWUTable, |
cc61c64b | 569 | |
1b1a35ee XL |
570 | /// A live node representing a point of execution before closure entry & |
571 | /// after closure exit. Used to calculate liveness of captured variables | |
572 | /// through calls to the same closure. Used for Fn & FnMut closures only. | |
573 | closure_ln: LiveNode, | |
574 | /// A live node representing every 'exit' from the function, whether it be | |
575 | /// by explicit return, panic, or other means. | |
576 | exit_ln: LiveNode, | |
577 | ||
223e47cc LB |
578 | // mappings from loop node ID to LiveNode |
579 | // ("break" label should map to loop node ID, | |
580 | // it probably doesn't now) | |
532ac7d7 XL |
581 | break_ln: HirIdMap<LiveNode>, |
582 | cont_ln: HirIdMap<LiveNode>, | |
223e47cc LB |
583 | } |
584 | ||
1a4d82fc | 585 | impl<'a, 'tcx> Liveness<'a, 'tcx> { |
1b1a35ee XL |
586 | fn new(ir: &'a mut IrMaps<'tcx>, body_owner: LocalDefId) -> Liveness<'a, 'tcx> { |
587 | let typeck_results = ir.tcx.typeck(body_owner); | |
588 | let param_env = ir.tcx.param_env(body_owner); | |
589 | let upvars = ir.tcx.upvars_mentioned(body_owner); | |
32a655c1 | 590 | |
1b1a35ee XL |
591 | let closure_ln = ir.add_live_node(ClosureNode); |
592 | let exit_ln = ir.add_live_node(ExitNode); | |
32a655c1 | 593 | |
1b1a35ee XL |
594 | let num_live_nodes = ir.lnks.len(); |
595 | let num_vars = ir.var_kinds.len(); | |
32a655c1 | 596 | |
1a4d82fc | 597 | Liveness { |
041b39d2 | 598 | ir, |
1b1a35ee | 599 | body_owner, |
3dfed10e | 600 | typeck_results, |
ba9703b0 | 601 | param_env, |
1b1a35ee XL |
602 | upvars, |
603 | successors: IndexVec::from_elem_n(None, num_live_nodes), | |
0bf4aa26 | 604 | rwu_table: RWUTable::new(num_live_nodes * num_vars), |
1b1a35ee XL |
605 | closure_ln, |
606 | exit_ln, | |
a1dfa0c6 XL |
607 | break_ln: Default::default(), |
608 | cont_ln: Default::default(), | |
1a4d82fc | 609 | } |
223e47cc | 610 | } |
223e47cc | 611 | |
94b46f34 XL |
612 | fn live_node(&self, hir_id: HirId, span: Span) -> LiveNode { |
613 | match self.ir.live_node_map.get(&hir_id) { | |
dfeec247 XL |
614 | Some(&ln) => ln, |
615 | None => { | |
616 | // This must be a mismatch between the ir_map construction | |
617 | // above and the propagation code below; the two sets of | |
618 | // code have to agree about which AST nodes are worth | |
619 | // creating liveness nodes for. | |
620 | span_bug!(span, "no live node registered for node {:?}", hir_id); | |
621 | } | |
223e47cc LB |
622 | } |
623 | } | |
624 | ||
94b46f34 XL |
625 | fn variable(&self, hir_id: HirId, span: Span) -> Variable { |
626 | self.ir.variable(hir_id, span) | |
223e47cc LB |
627 | } |
628 | ||
dfeec247 | 629 | fn define_bindings_in_pat(&mut self, pat: &hir::Pat<'_>, mut succ: LiveNode) -> LiveNode { |
e74abb32 XL |
630 | // In an or-pattern, only consider the first pattern; any later patterns |
631 | // must have the same bindings, and we also consider the first pattern | |
632 | // to be the "authoritative" set of ids. | |
633 | pat.each_binding_or_first(&mut |_, hir_id, pat_sp, ident| { | |
634 | let ln = self.live_node(hir_id, pat_sp); | |
635 | let var = self.variable(hir_id, ident.span); | |
636 | self.init_from_succ(ln, succ); | |
637 | self.define(ln, var); | |
223e47cc | 638 | succ = ln; |
1a4d82fc | 639 | }); |
223e47cc LB |
640 | succ |
641 | } | |
642 | ||
c34b1796 | 643 | fn idx(&self, ln: LiveNode, var: Variable) -> usize { |
1b1a35ee | 644 | ln.index() * self.ir.var_kinds.len() + var.index() |
223e47cc LB |
645 | } |
646 | ||
0bf4aa26 | 647 | fn live_on_entry(&self, ln: LiveNode, var: Variable) -> Option<LiveNodeKind> { |
1b1a35ee XL |
648 | if let Some(reader) = self.rwu_table.get_reader(self.idx(ln, var)) { |
649 | Some(self.ir.lnks[reader]) | |
650 | } else { | |
651 | None | |
652 | } | |
223e47cc LB |
653 | } |
654 | ||
0bf4aa26 | 655 | // Is this variable live on entry to any of its successor nodes? |
dfeec247 | 656 | fn live_on_exit(&self, ln: LiveNode, var: Variable) -> Option<LiveNodeKind> { |
1b1a35ee | 657 | let successor = self.successors[ln].unwrap(); |
1a4d82fc | 658 | self.live_on_entry(successor, var) |
223e47cc LB |
659 | } |
660 | ||
1a4d82fc | 661 | fn used_on_entry(&self, ln: LiveNode, var: Variable) -> bool { |
0bf4aa26 | 662 | self.rwu_table.get_used(self.idx(ln, var)) |
223e47cc LB |
663 | } |
664 | ||
dfeec247 | 665 | fn assigned_on_entry(&self, ln: LiveNode, var: Variable) -> Option<LiveNodeKind> { |
1b1a35ee XL |
666 | if let Some(writer) = self.rwu_table.get_writer(self.idx(ln, var)) { |
667 | Some(self.ir.lnks[writer]) | |
668 | } else { | |
669 | None | |
670 | } | |
223e47cc LB |
671 | } |
672 | ||
dfeec247 | 673 | fn assigned_on_exit(&self, ln: LiveNode, var: Variable) -> Option<LiveNodeKind> { |
1b1a35ee | 674 | let successor = self.successors[ln].unwrap(); |
1a4d82fc | 675 | self.assigned_on_entry(successor, var) |
223e47cc LB |
676 | } |
677 | ||
dfeec247 XL |
678 | fn indices2<F>(&mut self, ln: LiveNode, succ_ln: LiveNode, mut op: F) |
679 | where | |
c34b1796 | 680 | F: FnMut(&mut Liveness<'a, 'tcx>, usize, usize), |
1a4d82fc | 681 | { |
1b1a35ee XL |
682 | let node_base_idx = self.idx(ln, Variable::from(0u32)); |
683 | let succ_base_idx = self.idx(succ_ln, Variable::from(0u32)); | |
684 | for var_idx in 0..self.ir.var_kinds.len() { | |
1a4d82fc | 685 | op(self, node_base_idx + var_idx, succ_base_idx + var_idx); |
223e47cc LB |
686 | } |
687 | } | |
688 | ||
dfeec247 XL |
689 | fn write_vars<F>(&self, wr: &mut dyn Write, ln: LiveNode, mut test: F) -> io::Result<()> |
690 | where | |
f9f354fc | 691 | F: FnMut(usize) -> bool, |
1a4d82fc | 692 | { |
1b1a35ee XL |
693 | let node_base_idx = self.idx(ln, Variable::from(0u32)); |
694 | for var_idx in 0..self.ir.var_kinds.len() { | |
223e47cc | 695 | let idx = node_base_idx + var_idx; |
f9f354fc | 696 | if test(idx) { |
1b1a35ee | 697 | write!(wr, " {:?}", Variable::from(var_idx))?; |
223e47cc LB |
698 | } |
699 | } | |
1a4d82fc | 700 | Ok(()) |
223e47cc LB |
701 | } |
702 | ||
1a4d82fc JJ |
703 | #[allow(unused_must_use)] |
704 | fn ln_str(&self, ln: LiveNode) -> String { | |
705 | let mut wr = Vec::new(); | |
706 | { | |
0531ce1d | 707 | let wr = &mut wr as &mut dyn Write; |
1b1a35ee XL |
708 | write!(wr, "[{:?} of kind {:?} reads", ln, self.ir.lnks[ln]); |
709 | self.write_vars(wr, ln, |idx| self.rwu_table.get_reader(idx).is_some()); | |
1a4d82fc | 710 | write!(wr, " writes"); |
1b1a35ee | 711 | self.write_vars(wr, ln, |idx| self.rwu_table.get_writer(idx).is_some()); |
f9f354fc XL |
712 | write!(wr, " uses"); |
713 | self.write_vars(wr, ln, |idx| self.rwu_table.get_used(idx)); | |
714 | ||
1b1a35ee | 715 | write!(wr, " precedes {:?}]", self.successors[ln]); |
223e47cc | 716 | } |
1a4d82fc | 717 | String::from_utf8(wr).unwrap() |
223e47cc LB |
718 | } |
719 | ||
f9f354fc XL |
720 | fn log_liveness(&self, entry_ln: LiveNode, hir_id: hir::HirId) { |
721 | // hack to skip the loop unless debug! is enabled: | |
722 | debug!( | |
723 | "^^ liveness computation results for body {} (entry={:?})", | |
724 | { | |
1b1a35ee XL |
725 | for ln_idx in 0..self.ir.lnks.len() { |
726 | debug!("{:?}", self.ln_str(LiveNode::from(ln_idx))); | |
f9f354fc XL |
727 | } |
728 | hir_id | |
729 | }, | |
730 | entry_ln | |
731 | ); | |
732 | } | |
733 | ||
1a4d82fc | 734 | fn init_empty(&mut self, ln: LiveNode, succ_ln: LiveNode) { |
1b1a35ee | 735 | self.successors[ln] = Some(succ_ln); |
223e47cc | 736 | |
0bf4aa26 XL |
737 | // It is not necessary to initialize the RWUs here because they are all |
738 | // set to INV_INV_FALSE when they are created, and the sets only grow | |
739 | // during iterations. | |
223e47cc LB |
740 | } |
741 | ||
1a4d82fc | 742 | fn init_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode) { |
223e47cc | 743 | // more efficient version of init_empty() / merge_from_succ() |
1b1a35ee | 744 | self.successors[ln] = Some(succ_ln); |
1a4d82fc JJ |
745 | |
746 | self.indices2(ln, succ_ln, |this, idx, succ_idx| { | |
0bf4aa26 | 747 | this.rwu_table.copy_packed(idx, succ_idx); |
223e47cc | 748 | }); |
dfeec247 | 749 | debug!("init_from_succ(ln={}, succ={})", self.ln_str(ln), self.ln_str(succ_ln)); |
223e47cc LB |
750 | } |
751 | ||
dfeec247 XL |
752 | fn merge_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode, first_merge: bool) -> bool { |
753 | if ln == succ_ln { | |
754 | return false; | |
755 | } | |
223e47cc | 756 | |
74b04a01 | 757 | let mut any_changed = false; |
1a4d82fc | 758 | self.indices2(ln, succ_ln, |this, idx, succ_idx| { |
74b04a01 XL |
759 | // This is a special case, pulled out from the code below, where we |
760 | // don't have to do anything. It occurs about 60-70% of the time. | |
761 | if this.rwu_table.packed_rwus[succ_idx] == INV_INV_FALSE { | |
762 | return; | |
763 | } | |
764 | ||
765 | let mut changed = false; | |
0bf4aa26 XL |
766 | let mut rwu = this.rwu_table.get(idx); |
767 | let succ_rwu = this.rwu_table.get(succ_idx); | |
1b1a35ee | 768 | if succ_rwu.reader.is_some() && rwu.reader.is_none() { |
0bf4aa26 XL |
769 | rwu.reader = succ_rwu.reader; |
770 | changed = true | |
771 | } | |
772 | ||
1b1a35ee | 773 | if succ_rwu.writer.is_some() && rwu.writer.is_none() { |
0bf4aa26 XL |
774 | rwu.writer = succ_rwu.writer; |
775 | changed = true | |
776 | } | |
777 | ||
778 | if succ_rwu.used && !rwu.used { | |
779 | rwu.used = true; | |
223e47cc LB |
780 | changed = true; |
781 | } | |
0bf4aa26 XL |
782 | |
783 | if changed { | |
784 | this.rwu_table.assign_unpacked(idx, rwu); | |
74b04a01 | 785 | any_changed = true; |
0bf4aa26 | 786 | } |
1a4d82fc | 787 | }); |
223e47cc | 788 | |
dfeec247 XL |
789 | debug!( |
790 | "merge_from_succ(ln={:?}, succ={}, first_merge={}, changed={})", | |
791 | ln, | |
792 | self.ln_str(succ_ln), | |
793 | first_merge, | |
74b04a01 | 794 | any_changed |
dfeec247 | 795 | ); |
ba9703b0 | 796 | any_changed |
223e47cc LB |
797 | } |
798 | ||
799 | // Indicates that a local variable was *defined*; we know that no | |
800 | // uses of the variable can precede the definition (resolve checks | |
801 | // this) so we just clear out all the data. | |
1a4d82fc | 802 | fn define(&mut self, writer: LiveNode, var: Variable) { |
223e47cc | 803 | let idx = self.idx(writer, var); |
0bf4aa26 | 804 | self.rwu_table.assign_inv_inv(idx); |
223e47cc | 805 | |
dfeec247 | 806 | debug!("{:?} defines {:?} (idx={}): {}", writer, var, idx, self.ln_str(writer)); |
223e47cc LB |
807 | } |
808 | ||
809 | // Either read, write, or both depending on the acc bitset | |
c34b1796 | 810 | fn acc(&mut self, ln: LiveNode, var: Variable, acc: u32) { |
dfeec247 | 811 | debug!("{:?} accesses[{:x}] {:?}: {}", ln, acc, var, self.ln_str(ln)); |
1a4d82fc | 812 | |
223e47cc | 813 | let idx = self.idx(ln, var); |
0bf4aa26 | 814 | let mut rwu = self.rwu_table.get(idx); |
223e47cc LB |
815 | |
816 | if (acc & ACC_WRITE) != 0 { | |
1b1a35ee XL |
817 | rwu.reader = None; |
818 | rwu.writer = Some(ln); | |
223e47cc LB |
819 | } |
820 | ||
821 | // Important: if we both read/write, must do read second | |
822 | // or else the write will override. | |
823 | if (acc & ACC_READ) != 0 { | |
1b1a35ee | 824 | rwu.reader = Some(ln); |
223e47cc LB |
825 | } |
826 | ||
827 | if (acc & ACC_USE) != 0 { | |
0bf4aa26 | 828 | rwu.used = true; |
223e47cc | 829 | } |
223e47cc | 830 | |
0bf4aa26 XL |
831 | self.rwu_table.assign_unpacked(idx, rwu); |
832 | } | |
223e47cc | 833 | |
1b1a35ee XL |
834 | fn compute(&mut self, body: &hir::Body<'_>, hir_id: HirId) -> LiveNode { |
835 | debug!("compute: for body {:?}", body.id().hir_id); | |
223e47cc | 836 | |
f9f354fc XL |
837 | // # Liveness of captured variables |
838 | // | |
839 | // When computing the liveness for captured variables we take into | |
840 | // account how variable is captured (ByRef vs ByValue) and what is the | |
841 | // closure kind (Generator / FnOnce vs Fn / FnMut). | |
842 | // | |
843 | // Variables captured by reference are assumed to be used on the exit | |
844 | // from the closure. | |
845 | // | |
846 | // In FnOnce closures, variables captured by value are known to be dead | |
847 | // on exit since it is impossible to call the closure again. | |
848 | // | |
849 | // In Fn / FnMut closures, variables captured by value are live on exit | |
850 | // if they are live on the entry to the closure, since only the closure | |
851 | // itself can access them on subsequent calls. | |
852 | ||
1b1a35ee | 853 | if let Some(upvars) = self.upvars { |
f9f354fc XL |
854 | // Mark upvars captured by reference as used after closure exits. |
855 | for (&var_hir_id, upvar) in upvars.iter().rev() { | |
856 | let upvar_id = ty::UpvarId { | |
857 | var_path: ty::UpvarPath { hir_id: var_hir_id }, | |
1b1a35ee | 858 | closure_expr_id: self.body_owner, |
f9f354fc | 859 | }; |
3dfed10e | 860 | match self.typeck_results.upvar_capture(upvar_id) { |
f9f354fc XL |
861 | ty::UpvarCapture::ByRef(_) => { |
862 | let var = self.variable(var_hir_id, upvar.span); | |
1b1a35ee | 863 | self.acc(self.exit_ln, var, ACC_READ | ACC_USE); |
f9f354fc | 864 | } |
1b1a35ee | 865 | ty::UpvarCapture::ByValue(_) => {} |
f9f354fc XL |
866 | } |
867 | } | |
868 | } | |
cc61c64b | 869 | |
1b1a35ee | 870 | let succ = self.propagate_through_expr(&body.value, self.exit_ln); |
223e47cc | 871 | |
1b1a35ee XL |
872 | if self.upvars.is_none() { |
873 | // Either not a closure, or closure without any captured variables. | |
874 | // No need to determine liveness of captured variables, since there | |
875 | // are none. | |
876 | return succ; | |
f9f354fc XL |
877 | } |
878 | ||
1b1a35ee XL |
879 | let ty = self.typeck_results.node_type(hir_id); |
880 | match ty.kind() { | |
f9f354fc XL |
881 | ty::Closure(_def_id, substs) => match substs.as_closure().kind() { |
882 | ty::ClosureKind::Fn => {} | |
883 | ty::ClosureKind::FnMut => {} | |
884 | ty::ClosureKind::FnOnce => return succ, | |
dfeec247 | 885 | }, |
f9f354fc XL |
886 | ty::Generator(..) => return succ, |
887 | _ => { | |
1b1a35ee XL |
888 | span_bug!( |
889 | body.value.span, | |
890 | "{} has upvars so it should have a closure type: {:?}", | |
891 | hir_id, | |
892 | ty | |
893 | ); | |
f9f354fc XL |
894 | } |
895 | }; | |
896 | ||
897 | // Propagate through calls to the closure. | |
898 | let mut first_merge = true; | |
899 | loop { | |
1b1a35ee | 900 | self.init_from_succ(self.closure_ln, succ); |
f9f354fc XL |
901 | for param in body.params { |
902 | param.pat.each_binding(|_bm, hir_id, _x, ident| { | |
903 | let var = self.variable(hir_id, ident.span); | |
1b1a35ee | 904 | self.define(self.closure_ln, var); |
f9f354fc XL |
905 | }) |
906 | } | |
223e47cc | 907 | |
1b1a35ee | 908 | if !self.merge_from_succ(self.exit_ln, self.closure_ln, first_merge) { |
f9f354fc XL |
909 | break; |
910 | } | |
911 | first_merge = false; | |
1b1a35ee | 912 | assert_eq!(succ, self.propagate_through_expr(&body.value, self.exit_ln)); |
f9f354fc XL |
913 | } |
914 | ||
915 | succ | |
223e47cc LB |
916 | } |
917 | ||
dfeec247 | 918 | fn propagate_through_block(&mut self, blk: &hir::Block<'_>, succ: LiveNode) -> LiveNode { |
cc61c64b | 919 | if blk.targeted_by_break { |
532ac7d7 | 920 | self.break_ln.insert(blk.hir_id, succ); |
cc61c64b | 921 | } |
f9f354fc | 922 | let succ = self.propagate_through_opt_expr(blk.expr.as_deref(), succ); |
dfeec247 | 923 | blk.stmts.iter().rev().fold(succ, |succ, stmt| self.propagate_through_stmt(stmt, succ)) |
223e47cc LB |
924 | } |
925 | ||
dfeec247 | 926 | fn propagate_through_stmt(&mut self, stmt: &hir::Stmt<'_>, succ: LiveNode) -> LiveNode { |
e74abb32 | 927 | match stmt.kind { |
9fa01778 XL |
928 | hir::StmtKind::Local(ref local) => { |
929 | // Note: we mark the variable as defined regardless of whether | |
930 | // there is an initializer. Initially I had thought to only mark | |
931 | // the live variable as defined if it was initialized, and then we | |
932 | // could check for uninit variables just by scanning what is live | |
933 | // at the start of the function. But that doesn't work so well for | |
934 | // immutable variables defined in a loop: | |
935 | // loop { let x; x = 5; } | |
936 | // because the "assignment" loops back around and generates an error. | |
937 | // | |
938 | // So now we just check that variables defined w/o an | |
939 | // initializer are not live at the point of their | |
940 | // initialization, which is mildly more complex than checking | |
941 | // once at the func header but otherwise equivalent. | |
223e47cc | 942 | |
f9f354fc | 943 | let succ = self.propagate_through_opt_expr(local.init.as_deref(), succ); |
9fa01778 | 944 | self.define_bindings_in_pat(&local.pat, succ) |
1a4d82fc | 945 | } |
9fa01778 XL |
946 | hir::StmtKind::Item(..) => succ, |
947 | hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => { | |
948 | self.propagate_through_expr(&expr, succ) | |
223e47cc | 949 | } |
223e47cc LB |
950 | } |
951 | } | |
952 | ||
dfeec247 XL |
953 | fn propagate_through_exprs(&mut self, exprs: &[Expr<'_>], succ: LiveNode) -> LiveNode { |
954 | exprs.iter().rev().fold(succ, |succ, expr| self.propagate_through_expr(&expr, succ)) | |
223e47cc LB |
955 | } |
956 | ||
dfeec247 XL |
957 | fn propagate_through_opt_expr( |
958 | &mut self, | |
959 | opt_expr: Option<&Expr<'_>>, | |
960 | succ: LiveNode, | |
961 | ) -> LiveNode { | |
1a4d82fc | 962 | opt_expr.map_or(succ, |expr| self.propagate_through_expr(expr, succ)) |
223e47cc LB |
963 | } |
964 | ||
dfeec247 | 965 | fn propagate_through_expr(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode { |
ba9703b0 | 966 | debug!("propagate_through_expr: {:?}", expr); |
223e47cc | 967 | |
e74abb32 | 968 | match expr.kind { |
0bf4aa26 XL |
969 | // Interesting cases with control flow or which gen/kill |
970 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { | |
971 | self.access_path(expr.hir_id, path, succ, ACC_READ | ACC_USE) | |
972 | } | |
223e47cc | 973 | |
dfeec247 | 974 | hir::ExprKind::Field(ref e, _) => self.propagate_through_expr(&e, succ), |
1a4d82fc | 975 | |
9fa01778 | 976 | hir::ExprKind::Closure(..) => { |
ba9703b0 | 977 | debug!("{:?} is an ExprKind::Closure", expr); |
0bf4aa26 | 978 | |
0bf4aa26 XL |
979 | // the construction of a closure itself is not important, |
980 | // but we have to consider the closed over variables. | |
dfeec247 XL |
981 | let caps = self |
982 | .ir | |
983 | .capture_info_map | |
984 | .get(&expr.hir_id) | |
985 | .cloned() | |
986 | .unwrap_or_else(|| span_bug!(expr.span, "no registered caps")); | |
0bf4aa26 XL |
987 | |
988 | caps.iter().rev().fold(succ, |succ, cap| { | |
989 | self.init_from_succ(cap.ln, succ); | |
990 | let var = self.variable(cap.var_hid, expr.span); | |
991 | self.acc(cap.ln, var, ACC_READ | ACC_USE); | |
992 | cap.ln | |
993 | }) | |
994 | } | |
223e47cc | 995 | |
0bf4aa26 XL |
996 | // Note that labels have been resolved, so we don't need to look |
997 | // at the label ident | |
dfeec247 | 998 | hir::ExprKind::Loop(ref blk, _, _) => self.propagate_through_loop(expr, &blk, succ), |
223e47cc | 999 | |
dfeec247 | 1000 | hir::ExprKind::Match(ref e, arms, _) => { |
0bf4aa26 XL |
1001 | // |
1002 | // (e) | |
1003 | // | | |
1004 | // v | |
1005 | // (expr) | |
1006 | // / | \ | |
1007 | // | | | | |
1008 | // v v v | |
1009 | // (..arms..) | |
1010 | // | | | | |
1011 | // v v v | |
1012 | // ( succ ) | |
1013 | // | |
1014 | // | |
1015 | let ln = self.live_node(expr.hir_id, expr.span); | |
1016 | self.init_empty(ln, succ); | |
1017 | let mut first_merge = true; | |
1018 | for arm in arms { | |
1019 | let body_succ = self.propagate_through_expr(&arm.body, succ); | |
1020 | ||
1021 | let guard_succ = self.propagate_through_opt_expr( | |
dfeec247 XL |
1022 | arm.guard.as_ref().map(|hir::Guard::If(e)| *e), |
1023 | body_succ, | |
0bf4aa26 | 1024 | ); |
e74abb32 | 1025 | let arm_succ = self.define_bindings_in_pat(&arm.pat, guard_succ); |
0bf4aa26 XL |
1026 | self.merge_from_succ(ln, arm_succ, first_merge); |
1027 | first_merge = false; | |
dfeec247 | 1028 | } |
0bf4aa26 XL |
1029 | self.propagate_through_expr(&e, ln) |
1030 | } | |
223e47cc | 1031 | |
0bf4aa26 | 1032 | hir::ExprKind::Ret(ref o_e) => { |
1b1a35ee XL |
1033 | // Ignore succ and subst exit_ln. |
1034 | self.propagate_through_opt_expr(o_e.as_ref().map(|e| &**e), self.exit_ln) | |
0bf4aa26 | 1035 | } |
223e47cc | 1036 | |
0bf4aa26 XL |
1037 | hir::ExprKind::Break(label, ref opt_expr) => { |
1038 | // Find which label this break jumps to | |
1039 | let target = match label.target_id { | |
532ac7d7 | 1040 | Ok(hir_id) => self.break_ln.get(&hir_id), |
94b46f34 | 1041 | Err(err) => span_bug!(expr.span, "loop scope error: {}", err), |
dfeec247 XL |
1042 | } |
1043 | .cloned(); | |
223e47cc | 1044 | |
0bf4aa26 XL |
1045 | // Now that we know the label we're going to, |
1046 | // look it up in the break loop nodes table | |
8bb4bdeb | 1047 | |
0bf4aa26 XL |
1048 | match target { |
1049 | Some(b) => self.propagate_through_opt_expr(opt_expr.as_ref().map(|e| &**e), b), | |
f035d41b | 1050 | None => span_bug!(expr.span, "`break` to unknown label"), |
0bf4aa26 XL |
1051 | } |
1052 | } | |
223e47cc | 1053 | |
0bf4aa26 XL |
1054 | hir::ExprKind::Continue(label) => { |
1055 | // Find which label this expr continues to | |
dfeec247 XL |
1056 | let sc = label |
1057 | .target_id | |
1058 | .unwrap_or_else(|err| span_bug!(expr.span, "loop scope error: {}", err)); | |
223e47cc | 1059 | |
0bf4aa26 XL |
1060 | // Now that we know the label we're going to, |
1061 | // look it up in the continue loop nodes table | |
dfeec247 XL |
1062 | self.cont_ln |
1063 | .get(&sc) | |
1064 | .cloned() | |
1065 | .unwrap_or_else(|| span_bug!(expr.span, "continue to unknown label")) | |
0bf4aa26 | 1066 | } |
223e47cc | 1067 | |
dfeec247 | 1068 | hir::ExprKind::Assign(ref l, ref r, _) => { |
2c00a5a8 XL |
1069 | // see comment on places in |
1070 | // propagate_through_place_components() | |
0bf4aa26 XL |
1071 | let succ = self.write_place(&l, succ, ACC_WRITE); |
1072 | let succ = self.propagate_through_place_components(&l, succ); | |
1073 | self.propagate_through_expr(&r, succ) | |
54a0048b | 1074 | } |
223e47cc | 1075 | |
0bf4aa26 XL |
1076 | hir::ExprKind::AssignOp(_, ref l, ref r) => { |
1077 | // an overloaded assign op is like a method call | |
3dfed10e | 1078 | if self.typeck_results.is_method_call(expr) { |
0bf4aa26 XL |
1079 | let succ = self.propagate_through_expr(&l, succ); |
1080 | self.propagate_through_expr(&r, succ) | |
1081 | } else { | |
1082 | // see comment on places in | |
1083 | // propagate_through_place_components() | |
dfeec247 | 1084 | let succ = self.write_place(&l, succ, ACC_WRITE | ACC_READ); |
0bf4aa26 XL |
1085 | let succ = self.propagate_through_expr(&r, succ); |
1086 | self.propagate_through_place_components(&l, succ) | |
1087 | } | |
1088 | } | |
223e47cc | 1089 | |
0bf4aa26 | 1090 | // Uninteresting cases: just propagate in rev exec order |
dfeec247 | 1091 | hir::ExprKind::Array(ref exprs) => self.propagate_through_exprs(exprs, succ), |
223e47cc | 1092 | |
0bf4aa26 XL |
1093 | hir::ExprKind::Struct(_, ref fields, ref with_expr) => { |
1094 | let succ = self.propagate_through_opt_expr(with_expr.as_ref().map(|e| &**e), succ); | |
dfeec247 XL |
1095 | fields |
1096 | .iter() | |
1097 | .rev() | |
1098 | .fold(succ, |succ, field| self.propagate_through_expr(&field.expr, succ)) | |
0bf4aa26 | 1099 | } |
223e47cc | 1100 | |
0bf4aa26 | 1101 | hir::ExprKind::Call(ref f, ref args) => { |
ba9703b0 XL |
1102 | let m = self.ir.tcx.parent_module(expr.hir_id).to_def_id(); |
1103 | let succ = if self.ir.tcx.is_ty_uninhabited_from( | |
1104 | m, | |
3dfed10e | 1105 | self.typeck_results.expr_ty(expr), |
ba9703b0 XL |
1106 | self.param_env, |
1107 | ) { | |
1b1a35ee | 1108 | self.exit_ln |
0bf4aa26 XL |
1109 | } else { |
1110 | succ | |
1111 | }; | |
1112 | let succ = self.propagate_through_exprs(args, succ); | |
1113 | self.propagate_through_expr(&f, succ) | |
1114 | } | |
223e47cc | 1115 | |
f035d41b | 1116 | hir::ExprKind::MethodCall(.., ref args, _) => { |
ba9703b0 XL |
1117 | let m = self.ir.tcx.parent_module(expr.hir_id).to_def_id(); |
1118 | let succ = if self.ir.tcx.is_ty_uninhabited_from( | |
1119 | m, | |
3dfed10e | 1120 | self.typeck_results.expr_ty(expr), |
ba9703b0 XL |
1121 | self.param_env, |
1122 | ) { | |
1b1a35ee | 1123 | self.exit_ln |
0bf4aa26 XL |
1124 | } else { |
1125 | succ | |
1126 | }; | |
223e47cc | 1127 | |
0bf4aa26 XL |
1128 | self.propagate_through_exprs(args, succ) |
1129 | } | |
223e47cc | 1130 | |
dfeec247 | 1131 | hir::ExprKind::Tup(ref exprs) => self.propagate_through_exprs(exprs, succ), |
223e47cc | 1132 | |
0bf4aa26 XL |
1133 | hir::ExprKind::Binary(op, ref l, ref r) if op.node.is_lazy() => { |
1134 | let r_succ = self.propagate_through_expr(&r, succ); | |
223e47cc | 1135 | |
0bf4aa26 XL |
1136 | let ln = self.live_node(expr.hir_id, expr.span); |
1137 | self.init_from_succ(ln, succ); | |
1138 | self.merge_from_succ(ln, r_succ, false); | |
223e47cc | 1139 | |
0bf4aa26 XL |
1140 | self.propagate_through_expr(&l, ln) |
1141 | } | |
1a4d82fc | 1142 | |
dfeec247 | 1143 | hir::ExprKind::Index(ref l, ref r) | hir::ExprKind::Binary(_, ref l, ref r) => { |
0bf4aa26 XL |
1144 | let r_succ = self.propagate_through_expr(&r, succ); |
1145 | self.propagate_through_expr(&l, r_succ) | |
1146 | } | |
1147 | ||
dfeec247 XL |
1148 | hir::ExprKind::Box(ref e) |
1149 | | hir::ExprKind::AddrOf(_, _, ref e) | |
1150 | | hir::ExprKind::Cast(ref e, _) | |
1151 | | hir::ExprKind::Type(ref e, _) | |
1152 | | hir::ExprKind::DropTemps(ref e) | |
1153 | | hir::ExprKind::Unary(_, ref e) | |
1154 | | hir::ExprKind::Yield(ref e, _) | |
1155 | | hir::ExprKind::Repeat(ref e, _) => self.propagate_through_expr(&e, succ), | |
0bf4aa26 | 1156 | |
f9f354fc XL |
1157 | hir::ExprKind::InlineAsm(ref asm) => { |
1158 | // Handle non-returning asm | |
1159 | let mut succ = if asm.options.contains(InlineAsmOptions::NORETURN) { | |
1b1a35ee | 1160 | self.exit_ln |
f9f354fc XL |
1161 | } else { |
1162 | succ | |
1163 | }; | |
1164 | ||
1165 | // Do a first pass for writing outputs only | |
1166 | for op in asm.operands.iter().rev() { | |
1167 | match op { | |
1168 | hir::InlineAsmOperand::In { .. } | |
1169 | | hir::InlineAsmOperand::Const { .. } | |
1170 | | hir::InlineAsmOperand::Sym { .. } => {} | |
1171 | hir::InlineAsmOperand::Out { expr, .. } => { | |
1172 | if let Some(expr) = expr { | |
1173 | succ = self.write_place(expr, succ, ACC_WRITE); | |
1174 | } | |
1175 | } | |
1176 | hir::InlineAsmOperand::InOut { expr, .. } => { | |
29967ef6 | 1177 | succ = self.write_place(expr, succ, ACC_READ | ACC_WRITE | ACC_USE); |
f9f354fc XL |
1178 | } |
1179 | hir::InlineAsmOperand::SplitInOut { out_expr, .. } => { | |
1180 | if let Some(expr) = out_expr { | |
1181 | succ = self.write_place(expr, succ, ACC_WRITE); | |
1182 | } | |
1183 | } | |
1184 | } | |
1185 | } | |
1186 | ||
1187 | // Then do a second pass for inputs | |
1188 | let mut succ = succ; | |
1189 | for op in asm.operands.iter().rev() { | |
1190 | match op { | |
1191 | hir::InlineAsmOperand::In { expr, .. } | |
1192 | | hir::InlineAsmOperand::Const { expr, .. } | |
1193 | | hir::InlineAsmOperand::Sym { expr, .. } => { | |
1194 | succ = self.propagate_through_expr(expr, succ) | |
1195 | } | |
1196 | hir::InlineAsmOperand::Out { expr, .. } => { | |
1197 | if let Some(expr) = expr { | |
1198 | succ = self.propagate_through_place_components(expr, succ); | |
1199 | } | |
1200 | } | |
1201 | hir::InlineAsmOperand::InOut { expr, .. } => { | |
1202 | succ = self.propagate_through_place_components(expr, succ); | |
1203 | } | |
1204 | hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => { | |
1205 | if let Some(expr) = out_expr { | |
1206 | succ = self.propagate_through_place_components(expr, succ); | |
1207 | } | |
1208 | succ = self.propagate_through_expr(in_expr, succ); | |
1209 | } | |
1210 | } | |
1211 | } | |
1212 | succ | |
1213 | } | |
1214 | ||
ba9703b0 | 1215 | hir::ExprKind::LlvmInlineAsm(ref asm) => { |
60c5eb7d | 1216 | let ia = &asm.inner; |
dfeec247 XL |
1217 | let outputs = asm.outputs_exprs; |
1218 | let inputs = asm.inputs_exprs; | |
0bf4aa26 | 1219 | let succ = ia.outputs.iter().zip(outputs).rev().fold(succ, |succ, (o, output)| { |
60c5eb7d XL |
1220 | // see comment on places |
1221 | // in propagate_through_place_components() | |
1222 | if o.is_indirect { | |
1223 | self.propagate_through_expr(output, succ) | |
1224 | } else { | |
dfeec247 | 1225 | let acc = if o.is_rw { ACC_WRITE | ACC_READ } else { ACC_WRITE }; |
60c5eb7d XL |
1226 | let succ = self.write_place(output, succ, acc); |
1227 | self.propagate_through_place_components(output, succ) | |
1228 | } | |
1229 | }); | |
54a0048b | 1230 | |
0bf4aa26 XL |
1231 | // Inputs are executed first. Propagate last because of rev order |
1232 | self.propagate_through_exprs(inputs, succ) | |
1233 | } | |
223e47cc | 1234 | |
dfeec247 | 1235 | hir::ExprKind::Lit(..) |
29967ef6 | 1236 | | hir::ExprKind::ConstBlock(..) |
dfeec247 | 1237 | | hir::ExprKind::Err |
3dfed10e XL |
1238 | | hir::ExprKind::Path(hir::QPath::TypeRelative(..)) |
1239 | | hir::ExprKind::Path(hir::QPath::LangItem(..)) => succ, | |
223e47cc | 1240 | |
0bf4aa26 XL |
1241 | // Note that labels have been resolved, so we don't need to look |
1242 | // at the label ident | |
dfeec247 | 1243 | hir::ExprKind::Block(ref blk, _) => self.propagate_through_block(&blk, succ), |
223e47cc LB |
1244 | } |
1245 | } | |
1246 | ||
dfeec247 | 1247 | fn propagate_through_place_components(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode { |
2c00a5a8 | 1248 | // # Places |
223e47cc LB |
1249 | // |
1250 | // In general, the full flow graph structure for an | |
1251 | // assignment/move/etc can be handled in one of two ways, | |
1252 | // depending on whether what is being assigned is a "tracked | |
1253 | // value" or not. A tracked value is basically a local | |
1254 | // variable or argument. | |
1255 | // | |
1256 | // The two kinds of graphs are: | |
1257 | // | |
2c00a5a8 | 1258 | // Tracked place Untracked place |
223e47cc LB |
1259 | // ----------------------++----------------------- |
1260 | // || | |
1261 | // | || | | |
1262 | // v || v | |
1263 | // (rvalue) || (rvalue) | |
1264 | // | || | | |
1265 | // v || v | |
2c00a5a8 | 1266 | // (write of place) || (place components) |
223e47cc LB |
1267 | // | || | |
1268 | // v || v | |
1269 | // (succ) || (succ) | |
1270 | // || | |
1271 | // ----------------------++----------------------- | |
1272 | // | |
1273 | // I will cover the two cases in turn: | |
1274 | // | |
2c00a5a8 | 1275 | // # Tracked places |
223e47cc | 1276 | // |
2c00a5a8 | 1277 | // A tracked place is a local variable/argument `x`. In |
223e47cc | 1278 | // these cases, the link_node where the write occurs is linked |
2c00a5a8 | 1279 | // to node id of `x`. The `write_place()` routine generates |
223e47cc LB |
1280 | // the contents of this node. There are no subcomponents to |
1281 | // consider. | |
1282 | // | |
2c00a5a8 | 1283 | // # Non-tracked places |
223e47cc | 1284 | // |
2c00a5a8 | 1285 | // These are places like `x[5]` or `x.f`. In that case, we |
223e47cc LB |
1286 | // basically ignore the value which is written to but generate |
1287 | // reads for the components---`x` in these two examples. The | |
1288 | // components reads are generated by | |
2c00a5a8 | 1289 | // `propagate_through_place_components()` (this fn). |
223e47cc | 1290 | // |
2c00a5a8 | 1291 | // # Illegal places |
223e47cc | 1292 | // |
2c00a5a8 | 1293 | // It is still possible to observe assignments to non-places; |
223e47cc LB |
1294 | // these errors are detected in the later pass borrowck. We |
1295 | // just ignore such cases and treat them as reads. | |
1296 | ||
e74abb32 | 1297 | match expr.kind { |
8faf50e0 XL |
1298 | hir::ExprKind::Path(_) => succ, |
1299 | hir::ExprKind::Field(ref e, _) => self.propagate_through_expr(&e, succ), | |
dfeec247 | 1300 | _ => self.propagate_through_expr(expr, succ), |
223e47cc LB |
1301 | } |
1302 | } | |
1303 | ||
2c00a5a8 | 1304 | // see comment on propagate_through_place() |
dfeec247 | 1305 | fn write_place(&mut self, expr: &Expr<'_>, succ: LiveNode, acc: u32) -> LiveNode { |
e74abb32 | 1306 | match expr.kind { |
0bf4aa26 XL |
1307 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { |
1308 | self.access_path(expr.hir_id, path, succ, acc) | |
1309 | } | |
223e47cc | 1310 | |
0bf4aa26 XL |
1311 | // We do not track other places, so just propagate through |
1312 | // to their subcomponents. Also, it may happen that | |
1313 | // non-places occur here, because those are detected in the | |
1314 | // later pass borrowck. | |
dfeec247 | 1315 | _ => succ, |
223e47cc LB |
1316 | } |
1317 | } | |
1318 | ||
dfeec247 XL |
1319 | fn access_var( |
1320 | &mut self, | |
1321 | hir_id: HirId, | |
1322 | var_hid: HirId, | |
1323 | succ: LiveNode, | |
1324 | acc: u32, | |
1325 | span: Span, | |
1326 | ) -> LiveNode { | |
94b46f34 | 1327 | let ln = self.live_node(hir_id, span); |
ea8adc8c XL |
1328 | if acc != 0 { |
1329 | self.init_from_succ(ln, succ); | |
94b46f34 | 1330 | let var = self.variable(var_hid, span); |
ea8adc8c XL |
1331 | self.acc(ln, var, acc); |
1332 | } | |
1333 | ln | |
1334 | } | |
1335 | ||
dfeec247 XL |
1336 | fn access_path( |
1337 | &mut self, | |
1338 | hir_id: HirId, | |
1339 | path: &hir::Path<'_>, | |
1340 | succ: LiveNode, | |
1341 | acc: u32, | |
1342 | ) -> LiveNode { | |
48663c56 | 1343 | match path.res { |
f9f354fc | 1344 | Res::Local(hid) => self.access_var(hir_id, hid, succ, acc, path.span), |
dfeec247 | 1345 | _ => succ, |
223e47cc LB |
1346 | } |
1347 | } | |
1348 | ||
416331ca XL |
1349 | fn propagate_through_loop( |
1350 | &mut self, | |
dfeec247 XL |
1351 | expr: &Expr<'_>, |
1352 | body: &hir::Block<'_>, | |
1353 | succ: LiveNode, | |
416331ca | 1354 | ) -> LiveNode { |
223e47cc | 1355 | /* |
223e47cc LB |
1356 | We model control flow like this: |
1357 | ||
416331ca XL |
1358 | (expr) <-+ |
1359 | | | | |
1360 | v | | |
1361 | (body) --+ | |
223e47cc | 1362 | |
416331ca XL |
1363 | Note that a `continue` expression targeting the `loop` will have a successor of `expr`. |
1364 | Meanwhile, a `break` expression will have a successor of `succ`. | |
223e47cc LB |
1365 | */ |
1366 | ||
223e47cc LB |
1367 | // first iteration: |
1368 | let mut first_merge = true; | |
94b46f34 | 1369 | let ln = self.live_node(expr.hir_id, expr.span); |
223e47cc | 1370 | self.init_empty(ln, succ); |
ba9703b0 | 1371 | debug!("propagate_through_loop: using id for loop body {} {:?}", expr.hir_id, body); |
9fa01778 | 1372 | |
532ac7d7 | 1373 | self.break_ln.insert(expr.hir_id, succ); |
cc61c64b | 1374 | |
416331ca | 1375 | self.cont_ln.insert(expr.hir_id, ln); |
9fa01778 | 1376 | |
416331ca | 1377 | let body_ln = self.propagate_through_block(body, ln); |
223e47cc LB |
1378 | |
1379 | // repeat until fixed point is reached: | |
1380 | while self.merge_from_succ(ln, body_ln, first_merge) { | |
1381 | first_merge = false; | |
416331ca | 1382 | assert_eq!(body_ln, self.propagate_through_block(body, ln)); |
223e47cc LB |
1383 | } |
1384 | ||
416331ca | 1385 | ln |
223e47cc | 1386 | } |
223e47cc LB |
1387 | } |
1388 | ||
1389 | // _______________________________________________________________________ | |
1390 | // Checking for error conditions | |
1391 | ||
32a655c1 | 1392 | impl<'a, 'tcx> Visitor<'tcx> for Liveness<'a, 'tcx> { |
ba9703b0 | 1393 | type Map = intravisit::ErasedMap<'tcx>; |
dfeec247 | 1394 | |
ba9703b0 | 1395 | fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
32a655c1 SL |
1396 | NestedVisitorMap::None |
1397 | } | |
1398 | ||
dfeec247 | 1399 | fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) { |
e74abb32 XL |
1400 | self.check_unused_vars_in_pat(&local.pat, None, |spans, hir_id, ln, var| { |
1401 | if local.init.is_some() { | |
1402 | self.warn_about_dead_assign(spans, hir_id, ln, var); | |
1403 | } | |
1404 | }); | |
32a655c1 | 1405 | |
e74abb32 | 1406 | intravisit::walk_local(self, local); |
223e47cc LB |
1407 | } |
1408 | ||
dfeec247 | 1409 | fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) { |
e74abb32 | 1410 | check_expr(self, ex); |
9fa01778 XL |
1411 | } |
1412 | ||
dfeec247 | 1413 | fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) { |
e74abb32 XL |
1414 | self.check_unused_vars_in_pat(&arm.pat, None, |_, _, _, _| {}); |
1415 | intravisit::walk_arm(self, arm); | |
9fa01778 | 1416 | } |
223e47cc LB |
1417 | } |
1418 | ||
dfeec247 | 1419 | fn check_expr<'tcx>(this: &mut Liveness<'_, 'tcx>, expr: &'tcx Expr<'tcx>) { |
e74abb32 | 1420 | match expr.kind { |
dfeec247 | 1421 | hir::ExprKind::Assign(ref l, ..) => { |
2c00a5a8 | 1422 | this.check_place(&l); |
54a0048b | 1423 | } |
223e47cc | 1424 | |
0bf4aa26 | 1425 | hir::ExprKind::AssignOp(_, ref l, _) => { |
3dfed10e | 1426 | if !this.typeck_results.is_method_call(expr) { |
0bf4aa26 XL |
1427 | this.check_place(&l); |
1428 | } | |
223e47cc LB |
1429 | } |
1430 | ||
f9f354fc XL |
1431 | hir::ExprKind::InlineAsm(ref asm) => { |
1432 | for op in asm.operands { | |
1433 | match op { | |
1434 | hir::InlineAsmOperand::Out { expr, .. } => { | |
1435 | if let Some(expr) = expr { | |
1436 | this.check_place(expr); | |
1437 | } | |
1438 | } | |
1439 | hir::InlineAsmOperand::InOut { expr, .. } => { | |
1440 | this.check_place(expr); | |
1441 | } | |
1442 | hir::InlineAsmOperand::SplitInOut { out_expr, .. } => { | |
1443 | if let Some(out_expr) = out_expr { | |
1444 | this.check_place(out_expr); | |
1445 | } | |
1446 | } | |
1447 | _ => {} | |
1448 | } | |
1449 | } | |
1450 | } | |
1451 | ||
ba9703b0 | 1452 | hir::ExprKind::LlvmInlineAsm(ref asm) => { |
dfeec247 | 1453 | for input in asm.inputs_exprs { |
0bf4aa26 XL |
1454 | this.visit_expr(input); |
1455 | } | |
223e47cc | 1456 | |
0bf4aa26 | 1457 | // Output operands must be places |
dfeec247 | 1458 | for (o, output) in asm.inner.outputs.iter().zip(asm.outputs_exprs) { |
0bf4aa26 XL |
1459 | if !o.is_indirect { |
1460 | this.check_place(output); | |
1461 | } | |
1462 | this.visit_expr(output); | |
1463 | } | |
0bf4aa26 XL |
1464 | } |
1465 | ||
1466 | // no correctness conditions related to liveness | |
dfeec247 XL |
1467 | hir::ExprKind::Call(..) |
1468 | | hir::ExprKind::MethodCall(..) | |
1469 | | hir::ExprKind::Match(..) | |
1470 | | hir::ExprKind::Loop(..) | |
1471 | | hir::ExprKind::Index(..) | |
1472 | | hir::ExprKind::Field(..) | |
1473 | | hir::ExprKind::Array(..) | |
1474 | | hir::ExprKind::Tup(..) | |
1475 | | hir::ExprKind::Binary(..) | |
1476 | | hir::ExprKind::Cast(..) | |
1477 | | hir::ExprKind::DropTemps(..) | |
1478 | | hir::ExprKind::Unary(..) | |
1479 | | hir::ExprKind::Ret(..) | |
1480 | | hir::ExprKind::Break(..) | |
1481 | | hir::ExprKind::Continue(..) | |
1482 | | hir::ExprKind::Lit(_) | |
29967ef6 | 1483 | | hir::ExprKind::ConstBlock(..) |
dfeec247 XL |
1484 | | hir::ExprKind::Block(..) |
1485 | | hir::ExprKind::AddrOf(..) | |
1486 | | hir::ExprKind::Struct(..) | |
1487 | | hir::ExprKind::Repeat(..) | |
1488 | | hir::ExprKind::Closure(..) | |
1489 | | hir::ExprKind::Path(_) | |
1490 | | hir::ExprKind::Yield(..) | |
1491 | | hir::ExprKind::Box(..) | |
1492 | | hir::ExprKind::Type(..) | |
1493 | | hir::ExprKind::Err => {} | |
223e47cc | 1494 | } |
e74abb32 XL |
1495 | |
1496 | intravisit::walk_expr(this, expr); | |
223e47cc LB |
1497 | } |
1498 | ||
e74abb32 | 1499 | impl<'tcx> Liveness<'_, 'tcx> { |
dfeec247 | 1500 | fn check_place(&mut self, expr: &'tcx Expr<'tcx>) { |
e74abb32 | 1501 | match expr.kind { |
8faf50e0 | 1502 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { |
48663c56 | 1503 | if let Res::Local(var_hid) = path.res { |
f9f354fc XL |
1504 | // Assignment to an immutable variable or argument: only legal |
1505 | // if there is no later assignment. If this local is actually | |
1506 | // mutable, then check for a reassignment to flag the mutability | |
1507 | // as being used. | |
1508 | let ln = self.live_node(expr.hir_id, expr.span); | |
1509 | let var = self.variable(var_hid, expr.span); | |
1510 | self.warn_about_dead_assign(vec![expr.span], expr.hir_id, ln, var); | |
223e47cc | 1511 | } |
223e47cc | 1512 | } |
1a4d82fc | 1513 | _ => { |
2c00a5a8 | 1514 | // For other kinds of places, no checks are required, |
1a4d82fc | 1515 | // and any embedded expressions are actually rvalues |
92a42be0 | 1516 | intravisit::walk_expr(self, expr); |
1a4d82fc | 1517 | } |
223e47cc LB |
1518 | } |
1519 | } | |
1520 | ||
1a4d82fc | 1521 | fn should_warn(&self, var: Variable) -> Option<String> { |
223e47cc | 1522 | let name = self.ir.variable_name(var); |
1b1a35ee XL |
1523 | if name == kw::Invalid { |
1524 | return None; | |
1525 | } | |
1526 | let name: &str = &name.as_str(); | |
1527 | if name.as_bytes()[0] == b'_' { | |
1528 | return None; | |
1529 | } | |
1530 | Some(name.to_owned()) | |
223e47cc LB |
1531 | } |
1532 | ||
f9f354fc | 1533 | fn warn_about_unused_upvars(&self, entry_ln: LiveNode) { |
1b1a35ee | 1534 | let upvars = match self.upvars { |
f9f354fc XL |
1535 | None => return, |
1536 | Some(upvars) => upvars, | |
1537 | }; | |
1538 | for (&var_hir_id, upvar) in upvars.iter() { | |
1539 | let var = self.variable(var_hir_id, upvar.span); | |
1540 | let upvar_id = ty::UpvarId { | |
1541 | var_path: ty::UpvarPath { hir_id: var_hir_id }, | |
1b1a35ee | 1542 | closure_expr_id: self.body_owner, |
f9f354fc | 1543 | }; |
3dfed10e | 1544 | match self.typeck_results.upvar_capture(upvar_id) { |
1b1a35ee | 1545 | ty::UpvarCapture::ByValue(_) => {} |
f9f354fc XL |
1546 | ty::UpvarCapture::ByRef(..) => continue, |
1547 | }; | |
1548 | if self.used_on_entry(entry_ln, var) { | |
1549 | if self.live_on_entry(entry_ln, var).is_none() { | |
1550 | if let Some(name) = self.should_warn(var) { | |
1551 | self.ir.tcx.struct_span_lint_hir( | |
1552 | lint::builtin::UNUSED_ASSIGNMENTS, | |
1553 | var_hir_id, | |
1554 | vec![upvar.span], | |
1555 | |lint| { | |
1556 | lint.build(&format!("value captured by `{}` is never read", name)) | |
1557 | .help("did you mean to capture by reference instead?") | |
1558 | .emit(); | |
1559 | }, | |
1560 | ); | |
1561 | } | |
1562 | } | |
1563 | } else { | |
1564 | if let Some(name) = self.should_warn(var) { | |
1565 | self.ir.tcx.struct_span_lint_hir( | |
1566 | lint::builtin::UNUSED_VARIABLES, | |
1567 | var_hir_id, | |
1568 | vec![upvar.span], | |
1569 | |lint| { | |
1570 | lint.build(&format!("unused variable: `{}`", name)) | |
1571 | .help("did you mean to capture by reference instead?") | |
1572 | .emit(); | |
1573 | }, | |
1574 | ); | |
1575 | } | |
1576 | } | |
1577 | } | |
1578 | } | |
1579 | ||
dfeec247 XL |
1580 | fn warn_about_unused_args(&self, body: &hir::Body<'_>, entry_ln: LiveNode) { |
1581 | for p in body.params { | |
e74abb32 XL |
1582 | self.check_unused_vars_in_pat(&p.pat, Some(entry_ln), |spans, hir_id, ln, var| { |
1583 | if self.live_on_entry(ln, var).is_none() { | |
f9f354fc XL |
1584 | self.report_unsed_assign(hir_id, spans, var, |name| { |
1585 | format!("value passed to `{}` is never read", name) | |
1586 | }); | |
1a4d82fc | 1587 | } |
e74abb32 | 1588 | }); |
223e47cc LB |
1589 | } |
1590 | } | |
1591 | ||
e74abb32 XL |
1592 | fn check_unused_vars_in_pat( |
1593 | &self, | |
dfeec247 | 1594 | pat: &hir::Pat<'_>, |
e74abb32 XL |
1595 | entry_ln: Option<LiveNode>, |
1596 | on_used_on_entry: impl Fn(Vec<Span>, HirId, LiveNode, Variable), | |
1597 | ) { | |
1598 | // In an or-pattern, only consider the variable; any later patterns must have the same | |
1599 | // bindings, and we also consider the first pattern to be the "authoritative" set of ids. | |
ba9703b0 | 1600 | // However, we should take the ids and spans of variables with the same name from the later |
e74abb32 | 1601 | // patterns so the suggestions to prefix with underscores will apply to those too. |
1b1a35ee | 1602 | let mut vars: FxIndexMap<Symbol, (LiveNode, Variable, Vec<(HirId, Span)>)> = <_>::default(); |
e74abb32 XL |
1603 | |
1604 | pat.each_binding(|_, hir_id, pat_sp, ident| { | |
1605 | let ln = entry_ln.unwrap_or_else(|| self.live_node(hir_id, pat_sp)); | |
1606 | let var = self.variable(hir_id, ident.span); | |
ba9703b0 | 1607 | let id_and_sp = (hir_id, pat_sp); |
e74abb32 | 1608 | vars.entry(self.ir.variable_name(var)) |
ba9703b0 XL |
1609 | .and_modify(|(.., hir_ids_and_spans)| hir_ids_and_spans.push(id_and_sp)) |
1610 | .or_insert_with(|| (ln, var, vec![id_and_sp])); | |
e74abb32 XL |
1611 | }); |
1612 | ||
ba9703b0 | 1613 | for (_, (ln, var, hir_ids_and_spans)) in vars { |
e74abb32 | 1614 | if self.used_on_entry(ln, var) { |
ba9703b0 XL |
1615 | let id = hir_ids_and_spans[0].0; |
1616 | let spans = hir_ids_and_spans.into_iter().map(|(_, sp)| sp).collect(); | |
e74abb32 XL |
1617 | on_used_on_entry(spans, id, ln, var); |
1618 | } else { | |
ba9703b0 | 1619 | self.report_unused(hir_ids_and_spans, ln, var); |
223e47cc | 1620 | } |
e74abb32 | 1621 | } |
223e47cc LB |
1622 | } |
1623 | ||
ba9703b0 XL |
1624 | fn report_unused(&self, hir_ids_and_spans: Vec<(HirId, Span)>, ln: LiveNode, var: Variable) { |
1625 | let first_hir_id = hir_ids_and_spans[0].0; | |
1626 | ||
e74abb32 XL |
1627 | if let Some(name) = self.should_warn(var).filter(|name| name != "self") { |
1628 | // annoying: for parameters in funcs like `fn(x: i32) | |
1629 | // {ret}`, there is only one node, so asking about | |
1630 | // assigned_on_exit() is not meaningful. | |
dfeec247 | 1631 | let is_assigned = |
1b1a35ee | 1632 | if ln == self.exit_ln { false } else { self.assigned_on_exit(ln, var).is_some() }; |
223e47cc | 1633 | |
e74abb32 | 1634 | if is_assigned { |
74b04a01 XL |
1635 | self.ir.tcx.struct_span_lint_hir( |
1636 | lint::builtin::UNUSED_VARIABLES, | |
ba9703b0 XL |
1637 | first_hir_id, |
1638 | hir_ids_and_spans.into_iter().map(|(_, sp)| sp).collect::<Vec<_>>(), | |
74b04a01 XL |
1639 | |lint| { |
1640 | lint.build(&format!("variable `{}` is assigned to, but never used", name)) | |
1641 | .note(&format!("consider using `_{}` instead", name)) | |
1642 | .emit(); | |
1643 | }, | |
1644 | ) | |
e74abb32 | 1645 | } else { |
74b04a01 | 1646 | self.ir.tcx.struct_span_lint_hir( |
e74abb32 | 1647 | lint::builtin::UNUSED_VARIABLES, |
ba9703b0 XL |
1648 | first_hir_id, |
1649 | hir_ids_and_spans.iter().map(|(_, sp)| *sp).collect::<Vec<_>>(), | |
74b04a01 XL |
1650 | |lint| { |
1651 | let mut err = lint.build(&format!("unused variable: `{}`", name)); | |
ba9703b0 XL |
1652 | |
1653 | let (shorthands, non_shorthands): (Vec<_>, Vec<_>) = | |
1654 | hir_ids_and_spans.into_iter().partition(|(hir_id, span)| { | |
1655 | let var = self.variable(*hir_id, *span); | |
1656 | self.ir.variable_is_shorthand(var) | |
1657 | }); | |
1658 | ||
1659 | let mut shorthands = shorthands | |
1660 | .into_iter() | |
1661 | .map(|(_, span)| (span, format!("{}: _", name))) | |
1662 | .collect::<Vec<_>>(); | |
1663 | ||
1664 | // If we have both shorthand and non-shorthand, prefer the "try ignoring | |
1665 | // the field" message, and suggest `_` for the non-shorthands. If we only | |
1666 | // have non-shorthand, then prefix with an underscore instead. | |
1667 | if !shorthands.is_empty() { | |
1668 | shorthands.extend( | |
1669 | non_shorthands | |
1670 | .into_iter() | |
1671 | .map(|(_, span)| (span, "_".to_string())) | |
1672 | .collect::<Vec<_>>(), | |
1673 | ); | |
1674 | ||
1675 | err.multipart_suggestion( | |
1676 | "try ignoring the field", | |
1677 | shorthands, | |
1678 | Applicability::MachineApplicable, | |
1679 | ); | |
74b04a01 XL |
1680 | } else { |
1681 | err.multipart_suggestion( | |
ba9703b0 XL |
1682 | "if this is intentional, prefix it with an underscore", |
1683 | non_shorthands | |
1684 | .into_iter() | |
1685 | .map(|(_, span)| (span, format!("_{}", name))) | |
1686 | .collect::<Vec<_>>(), | |
74b04a01 XL |
1687 | Applicability::MachineApplicable, |
1688 | ); | |
1689 | } | |
ba9703b0 | 1690 | |
74b04a01 XL |
1691 | err.emit() |
1692 | }, | |
e74abb32 | 1693 | ); |
223e47cc | 1694 | } |
223e47cc | 1695 | } |
223e47cc LB |
1696 | } |
1697 | ||
e74abb32 | 1698 | fn warn_about_dead_assign(&self, spans: Vec<Span>, hir_id: HirId, ln: LiveNode, var: Variable) { |
223e47cc | 1699 | if self.live_on_exit(ln, var).is_none() { |
f9f354fc XL |
1700 | self.report_unsed_assign(hir_id, spans, var, |name| { |
1701 | format!("value assigned to `{}` is never read", name) | |
1702 | }); | |
92a42be0 SL |
1703 | } |
1704 | } | |
1705 | ||
f9f354fc XL |
1706 | fn report_unsed_assign( |
1707 | &self, | |
1708 | hir_id: HirId, | |
1709 | spans: Vec<Span>, | |
1710 | var: Variable, | |
1711 | message: impl Fn(&str) -> String, | |
1712 | ) { | |
92a42be0 | 1713 | if let Some(name) = self.should_warn(var) { |
f9f354fc XL |
1714 | self.ir.tcx.struct_span_lint_hir( |
1715 | lint::builtin::UNUSED_ASSIGNMENTS, | |
1716 | hir_id, | |
1717 | spans, | |
1718 | |lint| { | |
1719 | lint.build(&message(&name)) | |
1720 | .help("maybe it is overwritten before being read?") | |
1721 | .emit(); | |
1722 | }, | |
1723 | ) | |
223e47cc LB |
1724 | } |
1725 | } | |
92a42be0 | 1726 | } |