1use rustc_data_structures::graph::dominators::Dominators;
5use rustc_index::bit_set::DenseBitSet;
6use rustc_index::{IndexSlice, IndexVec};
7use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
8use rustc_middle::mir::{self, DefLocation, Location, TerminatorKind, traversal};
9use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
10use rustc_middle::{bug, span_bug};
11use tracing::debug;
12
13use super::FunctionCx;
14use crate::traits::*;
15
16pub(crate) fn non_ssa_locals<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
17 fx: &FunctionCx<'a, 'tcx, Bx>,
18 traversal_order: &[mir::BasicBlock],
19) -> DenseBitSet<mir::Local> {
20 let mir = fx.mir;
21 let dominators = mir.basic_blocks.dominators();
22 let locals = mir
23 .local_decls
24 .iter()
25 .map(|decl| {
26 let ty = fx.monomorphize(decl.ty);
27 let layout = fx.cx.spanned_layout_of(ty, decl.source_info.span);
28 if layout.is_zst() { LocalKind::ZST } else { LocalKind::Unused }
29 })
30 .collect();
31
32 let mut analyzer = LocalAnalyzer { fx, dominators, locals };
33
34 for arg in mir.args_iter() {
36 analyzer.define(arg, DefLocation::Argument);
37 }
38
39 for bb in traversal_order.iter().copied() {
43 let data = &mir.basic_blocks[bb];
44 analyzer.visit_basic_block_data(bb, data);
45 }
46
47 let mut non_ssa_locals = DenseBitSet::new_empty(analyzer.locals.len());
48 for (local, kind) in analyzer.locals.iter_enumerated() {
49 if matches!(kind, LocalKind::Memory) {
50 non_ssa_locals.insert(local);
51 }
52 }
53
54 non_ssa_locals
55}
56
57#[derive(Copy, Clone, PartialEq, Eq)]
58enum LocalKind {
59 ZST,
60 Memory,
62 Unused,
64 SSA(DefLocation),
66}
67
68struct LocalAnalyzer<'a, 'b, 'tcx, Bx: BuilderMethods<'b, 'tcx>> {
69 fx: &'a FunctionCx<'b, 'tcx, Bx>,
70 dominators: &'a Dominators<mir::BasicBlock>,
71 locals: IndexVec<mir::Local, LocalKind>,
72}
73
74impl<'a, 'b, 'tcx, Bx: BuilderMethods<'b, 'tcx>> LocalAnalyzer<'a, 'b, 'tcx, Bx> {
75 fn define(&mut self, local: mir::Local, location: DefLocation) {
76 let fx = self.fx;
77 let kind = &mut self.locals[local];
78 let decl = &fx.mir.local_decls[local];
79 match *kind {
80 LocalKind::ZST => {}
81 LocalKind::Memory => {}
82 LocalKind::Unused => {
83 let ty = fx.monomorphize(decl.ty);
84 let layout = fx.cx.spanned_layout_of(ty, decl.source_info.span);
85 *kind =
86 if fx.cx.is_backend_immediate(layout) || fx.cx.is_backend_scalar_pair(layout) {
87 LocalKind::SSA(location)
88 } else {
89 LocalKind::Memory
90 };
91 }
92 LocalKind::SSA(_) => *kind = LocalKind::Memory,
93 }
94 }
95
96 fn process_place(
97 &mut self,
98 place_ref: &mir::PlaceRef<'tcx>,
99 context: PlaceContext,
100 location: Location,
101 ) {
102 let cx = self.fx.cx;
103
104 if let Some((place_base, elem)) = place_ref.last_projection() {
105 let mut base_context = if context.is_mutating_use() {
106 PlaceContext::MutatingUse(MutatingUseContext::Projection)
107 } else {
108 PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
109 };
110
111 let is_consume = matches!(
113 context,
114 PlaceContext::NonMutatingUse(
115 NonMutatingUseContext::Copy | NonMutatingUseContext::Move,
116 )
117 );
118 if is_consume {
119 let base_ty = place_base.ty(self.fx.mir, cx.tcx());
120 let base_ty = self.fx.monomorphize(base_ty);
121
122 let elem_ty = base_ty.projection_ty(cx.tcx(), self.fx.monomorphize(elem)).ty;
124 let span = self.fx.mir.local_decls[place_ref.local].source_info.span;
125 if cx.spanned_layout_of(elem_ty, span).is_zst() {
126 return;
127 }
128
129 if let mir::ProjectionElem::Field(..) = elem {
130 let layout = cx.spanned_layout_of(base_ty.ty, span);
131 if cx.is_backend_immediate(layout) || cx.is_backend_scalar_pair(layout) {
132 base_context = context;
136 }
137 }
138 }
139
140 if let mir::ProjectionElem::Deref = elem {
141 base_context = PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy);
143 }
144
145 self.process_place(&place_base, base_context, location);
146 if let mir::ProjectionElem::Index(local) = elem {
150 self.visit_local(
151 local,
152 PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
153 location,
154 );
155 }
156 } else {
157 self.visit_local(place_ref.local, context, location);
158 }
159 }
160}
161
162impl<'a, 'b, 'tcx, Bx: BuilderMethods<'b, 'tcx>> Visitor<'tcx> for LocalAnalyzer<'a, 'b, 'tcx, Bx> {
163 fn visit_assign(
164 &mut self,
165 place: &mir::Place<'tcx>,
166 rvalue: &mir::Rvalue<'tcx>,
167 location: Location,
168 ) {
169 debug!("visit_assign(place={:?}, rvalue={:?})", place, rvalue);
170
171 if let Some(local) = place.as_local() {
172 self.define(local, DefLocation::Assignment(location));
173 if self.locals[local] != LocalKind::Memory {
174 let decl_span = self.fx.mir.local_decls[local].source_info.span;
175 if !self.fx.rvalue_creates_operand(rvalue, decl_span) {
176 self.locals[local] = LocalKind::Memory;
177 }
178 }
179 } else {
180 self.visit_place(place, PlaceContext::MutatingUse(MutatingUseContext::Store), location);
181 }
182
183 self.visit_rvalue(rvalue, location);
184 }
185
186 fn visit_place(&mut self, place: &mir::Place<'tcx>, context: PlaceContext, location: Location) {
187 debug!("visit_place(place={:?}, context={:?})", place, context);
188 self.process_place(&place.as_ref(), context, location);
189 }
190
191 fn visit_local(&mut self, local: mir::Local, context: PlaceContext, location: Location) {
192 match context {
193 PlaceContext::MutatingUse(MutatingUseContext::Call) => {
194 let call = location.block;
195 let TerminatorKind::Call { target, .. } =
196 self.fx.mir.basic_blocks[call].terminator().kind
197 else {
198 bug!()
199 };
200 self.define(local, DefLocation::CallReturn { call, target });
201 }
202
203 PlaceContext::NonUse(_)
204 | PlaceContext::NonMutatingUse(NonMutatingUseContext::PlaceMention)
205 | PlaceContext::MutatingUse(MutatingUseContext::Retag) => {}
206
207 PlaceContext::NonMutatingUse(
208 NonMutatingUseContext::Copy
209 | NonMutatingUseContext::Move
210 | NonMutatingUseContext::Inspect,
214 ) => match &mut self.locals[local] {
215 LocalKind::ZST => {}
216 LocalKind::Memory => {}
217 LocalKind::SSA(def) if def.dominates(location, self.dominators) => {}
218 kind @ (LocalKind::Unused | LocalKind::SSA(_)) => {
223 *kind = LocalKind::Memory;
224 }
225 },
226
227 PlaceContext::MutatingUse(
228 MutatingUseContext::Store
229 | MutatingUseContext::Deinit
230 | MutatingUseContext::SetDiscriminant
231 | MutatingUseContext::AsmOutput
232 | MutatingUseContext::Borrow
233 | MutatingUseContext::RawBorrow
234 | MutatingUseContext::Projection,
235 )
236 | PlaceContext::NonMutatingUse(
237 NonMutatingUseContext::SharedBorrow
238 | NonMutatingUseContext::FakeBorrow
239 | NonMutatingUseContext::RawBorrow
240 | NonMutatingUseContext::Projection,
241 ) => {
242 self.locals[local] = LocalKind::Memory;
243 }
244
245 PlaceContext::MutatingUse(MutatingUseContext::Drop) => {
246 let kind = &mut self.locals[local];
247 if *kind != LocalKind::Memory {
248 let ty = self.fx.mir.local_decls[local].ty;
249 let ty = self.fx.monomorphize(ty);
250 if self.fx.cx.type_needs_drop(ty) {
251 *kind = LocalKind::Memory;
253 }
254 }
255 }
256
257 PlaceContext::MutatingUse(MutatingUseContext::Yield) => bug!(),
258 }
259 }
260}
261
262#[derive(Copy, Clone, Debug, PartialEq, Eq)]
263pub(crate) enum CleanupKind {
264 NotCleanup,
265 Funclet,
266 Internal { funclet: mir::BasicBlock },
267}
268
269impl CleanupKind {
270 pub(crate) fn funclet_bb(self, for_bb: mir::BasicBlock) -> Option<mir::BasicBlock> {
271 match self {
272 CleanupKind::NotCleanup => None,
273 CleanupKind::Funclet => Some(for_bb),
274 CleanupKind::Internal { funclet } => Some(funclet),
275 }
276 }
277}
278
279pub(crate) fn cleanup_kinds(mir: &mir::Body<'_>) -> IndexVec<mir::BasicBlock, CleanupKind> {
283 fn discover_masters<'tcx>(
284 result: &mut IndexSlice<mir::BasicBlock, CleanupKind>,
285 mir: &mir::Body<'tcx>,
286 ) {
287 for (bb, data) in mir.basic_blocks.iter_enumerated() {
288 match data.terminator().kind {
289 TerminatorKind::Goto { .. }
290 | TerminatorKind::UnwindResume
291 | TerminatorKind::UnwindTerminate(_)
292 | TerminatorKind::Return
293 | TerminatorKind::TailCall { .. }
294 | TerminatorKind::CoroutineDrop
295 | TerminatorKind::Unreachable
296 | TerminatorKind::SwitchInt { .. }
297 | TerminatorKind::Yield { .. }
298 | TerminatorKind::FalseEdge { .. }
299 | TerminatorKind::FalseUnwind { .. } => { }
300 TerminatorKind::Call { unwind, .. }
301 | TerminatorKind::InlineAsm { unwind, .. }
302 | TerminatorKind::Assert { unwind, .. }
303 | TerminatorKind::Drop { unwind, .. } => {
304 if let mir::UnwindAction::Cleanup(unwind) = unwind {
305 debug!(
306 "cleanup_kinds: {:?}/{:?} registering {:?} as funclet",
307 bb, data, unwind
308 );
309 result[unwind] = CleanupKind::Funclet;
310 }
311 }
312 }
313 }
314 }
315
316 fn propagate<'tcx>(
317 result: &mut IndexSlice<mir::BasicBlock, CleanupKind>,
318 mir: &mir::Body<'tcx>,
319 ) {
320 let mut funclet_succs = IndexVec::from_elem(None, &mir.basic_blocks);
321
322 let mut set_successor = |funclet: mir::BasicBlock, succ| match funclet_succs[funclet] {
323 ref mut s @ None => {
324 debug!("set_successor: updating successor of {:?} to {:?}", funclet, succ);
325 *s = Some(succ);
326 }
327 Some(s) => {
328 if s != succ {
329 span_bug!(
330 mir.span,
331 "funclet {:?} has 2 parents - {:?} and {:?}",
332 funclet,
333 s,
334 succ
335 );
336 }
337 }
338 };
339
340 for (bb, data) in traversal::reverse_postorder(mir) {
341 let funclet = match result[bb] {
342 CleanupKind::NotCleanup => continue,
343 CleanupKind::Funclet => bb,
344 CleanupKind::Internal { funclet } => funclet,
345 };
346
347 debug!(
348 "cleanup_kinds: {:?}/{:?}/{:?} propagating funclet {:?}",
349 bb, data, result[bb], funclet
350 );
351
352 for succ in data.terminator().successors() {
353 let kind = result[succ];
354 debug!("cleanup_kinds: propagating {:?} to {:?}/{:?}", funclet, succ, kind);
355 match kind {
356 CleanupKind::NotCleanup => {
357 result[succ] = CleanupKind::Internal { funclet };
358 }
359 CleanupKind::Funclet => {
360 if funclet != succ {
361 set_successor(funclet, succ);
362 }
363 }
364 CleanupKind::Internal { funclet: succ_funclet } => {
365 if funclet != succ_funclet {
366 debug!(
370 "promoting {:?} to a funclet and updating {:?}",
371 succ, succ_funclet
372 );
373 result[succ] = CleanupKind::Funclet;
374 set_successor(succ_funclet, succ);
375 set_successor(funclet, succ);
376 }
377 }
378 }
379 }
380 }
381 }
382
383 let mut result = IndexVec::from_elem(CleanupKind::NotCleanup, &mir.basic_blocks);
384
385 discover_masters(&mut result, mir);
386 propagate(&mut result, mir);
387 debug!("cleanup_kinds: result={:?}", result);
388 result
389}