rapx/analysis/core/alias_analysis/default/
alias.rs

1use super::{MopAliasPair, MopFnAliasMap, block::Term, graph::*, types::*, value::*};
2use crate::{analysis::graphs::scc::Scc, def_id::*};
3use rustc_data_structures::fx::FxHashSet;
4use rustc_hir::def_id::DefId;
5use rustc_middle::{
6    mir::{Local, Operand, Place, ProjectionElem, TerminatorKind},
7    ty,
8};
9use std::collections::HashSet;
10
11impl<'tcx> MopGraph<'tcx> {
12    /* alias analysis for a single block */
13    pub fn alias_bb(&mut self, bb_index: usize) {
14        for constant in self.blocks[bb_index].const_value.clone() {
15            self.constants.insert(constant.local, constant.value);
16        }
17        let cur_block = self.blocks[bb_index].clone();
18        for assign in cur_block.assignments {
19            rap_debug!("assign: {:?}", assign);
20            let lv_idx = self.projection(assign.lv);
21            let rv_idx = self.projection(assign.rv);
22
23            self.assign_alias(lv_idx, rv_idx);
24            rap_debug!("Alias sets: {:?}", self.alias_sets)
25        }
26    }
27
28    /* Check the aliases introduced by the terminator of a basic block, i.e., a function call */
29    pub fn alias_bbcall(
30        &mut self,
31        bb_index: usize,
32        fn_map: &mut MopFnAliasMap,
33        recursion_set: &mut HashSet<DefId>,
34    ) {
35        let cur_block = self.blocks[bb_index].clone();
36        if let Term::Call(call) | Term::Drop(call) = cur_block.terminator {
37            if let TerminatorKind::Call {
38                func: Operand::Constant(ref constant),
39                ref args,
40                ref destination,
41                target: _,
42                unwind: _,
43                call_source: _,
44                fn_span: _,
45            } = call.kind
46            {
47                let lv = self.projection(*destination);
48                let mut may_drop = false;
49                if self.values[lv].may_drop {
50                    may_drop = true;
51                }
52
53                let mut merge_vec = Vec::new();
54                merge_vec.push(lv);
55
56                for arg in args {
57                    match arg.node {
58                        Operand::Copy(ref p) | Operand::Move(ref p) => {
59                            let rv = self.projection(*p);
60                            merge_vec.push(rv);
61                            if self.values[rv].may_drop {
62                                may_drop = true;
63                            }
64                        }
65                        //
66                        Operand::Constant(_) => {
67                            merge_vec.push(0);
68                        }
69                    }
70                }
71                if let &ty::FnDef(target_id, _) = constant.const_.ty().kind() {
72                    if may_drop == false {
73                        return;
74                    }
75                    // This function does not introduce new aliases.
76                    if is_no_alias_intrinsic(target_id) {
77                        return;
78                    }
79                    if !self.tcx.is_mir_available(target_id) {
80                        return;
81                    }
82                    rap_debug!("Sync aliases for function call: {:?}", target_id);
83                    let fn_aliases = if fn_map.contains_key(&target_id) {
84                        rap_debug!("Aliases existed");
85                        fn_map.get(&target_id).unwrap()
86                    } else {
87                        /* Fixed-point iteration: this is not perfect */
88                        if recursion_set.contains(&target_id) {
89                            return;
90                        }
91                        recursion_set.insert(target_id);
92                        let mut mop_graph = MopGraph::new(self.tcx, target_id);
93                        mop_graph.find_scc();
94                        mop_graph.check(0, fn_map, recursion_set);
95                        let ret_alias = mop_graph.ret_alias.clone();
96                        rap_debug!("Find aliases of {:?}: {:?}", target_id, ret_alias);
97                        fn_map.insert(target_id, ret_alias);
98                        recursion_set.remove(&target_id);
99                        fn_map.get(&target_id).unwrap()
100                    };
101                    if fn_aliases.aliases().is_empty() {
102                        if let Some(l_set_idx) = self.find_alias_set(lv) {
103                            self.alias_sets[l_set_idx].remove(&lv);
104                        }
105                    }
106                    for alias in fn_aliases.aliases().iter() {
107                        if !alias.valuable() {
108                            continue;
109                        }
110                        self.handle_fn_alias(alias, &merge_vec);
111                        rap_debug!("{:?}", self.alias_sets);
112                    }
113                } else if self.values[lv].may_drop {
114                    for rv in &merge_vec {
115                        if self.values[*rv].may_drop && lv != *rv && self.values[lv].is_ptr() {
116                            // We assume they are alias;
117                            // It is a function call and we should not distinguish left or right;
118                            // Merge the alias instead of assign.
119                            self.merge_alias(lv, *rv);
120                        }
121                    }
122                }
123            }
124        }
125    }
126
127    /*
128     * This is the function for field sensitivity
129     * If the projection is a deref, we directly return its local;
130     * If the projection is a field, we further make the id and its first element an alias.
131     */
132    pub fn projection(&mut self, place: Place<'tcx>) -> usize {
133        let local = place.local.as_usize();
134        rap_debug!("projection: place = {:?}, local = {:?}", place, local);
135        let mut value_idx = local;
136        // Projections are leveled
137        // Case 1: (*6).1 involves two projections: a Deref and a Field.
138        // Case 2: (6.0).1 involves two field projections.
139        // We should recursively parse the projection.
140        for proj in place.projection {
141            rap_debug!("proj: {:?}", proj);
142            let new_value_idx = self.values.len();
143            match proj {
144                ProjectionElem::Deref => {}
145                ProjectionElem::Field(field, ty) => {
146                    let field_idx = field.as_usize();
147                    // If the field has not been created as a value, we crate a value;
148                    if !self.values[value_idx].fields.contains_key(&field_idx) {
149                        let ty_env = ty::TypingEnv::post_analysis(self.tcx, self.def_id);
150                        let need_drop = ty.needs_drop(self.tcx, ty_env);
151                        let may_drop = !is_not_drop(self.tcx, ty);
152                        let mut node =
153                            Value::new(new_value_idx, local, need_drop, need_drop || may_drop);
154                        node.kind = kind(ty);
155                        node.father = Some(FatherInfo::new(value_idx, field_idx));
156                        self.values[value_idx].fields.insert(field_idx, node.index);
157                        self.values.push(node);
158                    }
159                    value_idx = *self.values[value_idx].fields.get(&field_idx).unwrap();
160                }
161                _ => {}
162            }
163        }
164        value_idx
165    }
166
167    /// Used to assign alias for a statement.
168    /// Operation: dealiasing the left; aliasing the left with right.
169    /// Synchronize the fields and father nodes iteratively.
170    pub fn assign_alias(&mut self, lv_idx: usize, rv_idx: usize) {
171        rap_debug!("assign_alias: lv = {:?}. rv = {:?}", lv_idx, rv_idx);
172
173        let r_set_idx = if let Some(idx) = self.find_alias_set(rv_idx) {
174            idx
175        } else {
176            self.alias_sets
177                .push([rv_idx].into_iter().collect::<FxHashSet<usize>>());
178            self.alias_sets.len() - 1
179        };
180
181        if let Some(l_set_idx) = self.find_alias_set(lv_idx) {
182            if l_set_idx == r_set_idx {
183                return;
184            }
185            self.alias_sets[l_set_idx].remove(&lv_idx);
186        }
187        let new_l_set_idx = r_set_idx;
188        self.alias_sets[new_l_set_idx].insert(lv_idx);
189
190        if self.values[lv_idx].fields.len() > 0 || self.values[rv_idx].fields.len() > 0 {
191            self.sync_field_alias(lv_idx, rv_idx, 0, true);
192        }
193        if self.values[rv_idx].father != None {
194            self.sync_father_alias(lv_idx, rv_idx, new_l_set_idx);
195        }
196    }
197
198    // Update the aliases of fields.
199    // Case 1, lv = 1; rv = 2; field of rv: 1;
200    // Expected result: [1,2] [1.1,2.1];
201    // Case 2, lv = 0.0, rv = 7, field of rv: 0;
202    // Expected result: [0.0,7] [0.0.0,7.0]
203    pub fn sync_field_alias(&mut self, lv: usize, rv: usize, depth: usize, clear_left: bool) {
204        rap_debug!("sync field aliases for lv:{} rv:{}", lv, rv);
205
206        let max_field_depth = 15;
207
208        if depth > max_field_depth {
209            return;
210        }
211
212        // For the fields of lv; we should remove them from the alias sets;
213        if clear_left {
214            for lv_field in self.values[lv].fields.clone().into_iter() {
215                if let Some(alias_set_idx) = self.find_alias_set(lv_field.1) {
216                    self.alias_sets[alias_set_idx].remove(&lv_field.1);
217                }
218            }
219        }
220        for rv_field in self.values[rv].fields.clone().into_iter() {
221            rap_debug!("rv_field: {:?}", rv_field);
222            if !self.values[lv].fields.contains_key(&rv_field.0) {
223                let mut node = Value::new(
224                    self.values.len(),
225                    self.values[lv].local,
226                    self.values[rv_field.1].need_drop,
227                    self.values[rv_field.1].may_drop,
228                );
229                node.kind = self.values[rv_field.1].kind;
230                node.father = Some(FatherInfo::new(lv, rv_field.0));
231                self.values[lv].fields.insert(rv_field.0, node.index);
232                self.values.push(node);
233            }
234            let lv_field_value_idx = *(self.values[lv].fields.get(&rv_field.0).unwrap());
235
236            rap_debug!(
237                "alias_set_id of rv_field {:?}",
238                self.find_alias_set(rv_field.1)
239            );
240            if let Some(alias_set_idx) = self.find_alias_set(rv_field.1) {
241                self.alias_sets[alias_set_idx].insert(lv_field_value_idx);
242            }
243            rap_debug!("alias sets: {:?}", self.alias_sets);
244            self.sync_field_alias(lv_field_value_idx, rv_field.1, depth + 1, true);
245        }
246    }
247
248    // For example,
249    // Case 1: lv = 1; rv = 2.0; alias set [2, 3]
250    // Expected result: [1, 2.0, 3.0], [2, 3];
251    // Case 2: lv = 1.0; rv = 2; alias set [1, 3]
252    // Expected result: [1.0, 2], [1, 3]
253    pub fn sync_father_alias(&mut self, lv: usize, rv: usize, lv_alias_set_idx: usize) {
254        rap_debug!("sync father aliases for lv:{} rv:{}", lv, rv);
255        let mut father_id = rv;
256        let mut father = self.values[father_id].father.clone();
257        while let Some(father_info) = father {
258            father_id = father_info.father_value_id;
259            let field_id = father_info.field_id;
260            let father_value = self.values[father_id].clone();
261            if let Some(alias_set_idx) = self.find_alias_set(father_id) {
262                for value_idx in self.alias_sets[alias_set_idx].clone() {
263                    // create a new node if the node does not exist;
264                    let field_value_idx = if self.values[value_idx].fields.contains_key(&field_id) {
265                        *self.values[value_idx].fields.get(&field_id).unwrap()
266                    } else {
267                        let mut node = Value::new(
268                            self.values.len(),
269                            self.values[value_idx].local,
270                            self.values[value_idx].need_drop,
271                            self.values[value_idx].may_drop,
272                        );
273                        node.kind = self.values[value_idx].kind;
274                        node.father = Some(FatherInfo::new(value_idx, field_id));
275                        self.values.push(node.clone());
276                        self.values[value_idx].fields.insert(field_id, node.index);
277                        node.index
278                    };
279                    // add the node to the alias_set of lv;
280                    self.alias_sets[lv_alias_set_idx].insert(field_value_idx);
281                }
282            }
283            father = father_value.father;
284        }
285    }
286
287    // Handle aliases introduced by function calls.
288    pub fn handle_fn_alias(&mut self, fn_alias: &MopAliasPair, arg_vec: &[usize]) {
289        rap_debug!(
290            "merge aliases returned by function calls, args: {:?}",
291            arg_vec
292        );
293        rap_debug!("fn alias: {}", fn_alias);
294        if fn_alias.left_local() >= arg_vec.len() || fn_alias.right_local() >= arg_vec.len() {
295            return;
296        }
297
298        let mut lv = arg_vec[fn_alias.left_local()];
299        let mut rv = arg_vec[fn_alias.right_local()];
300        let left_local = self.values[lv].local;
301        let right_local = self.values[rv].local;
302
303        for index in fn_alias.lhs_fields().iter() {
304            if !self.values[lv].fields.contains_key(index) {
305                let need_drop = fn_alias.lhs_need_drop;
306                let may_drop = fn_alias.lhs_may_drop;
307                let mut node = Value::new(self.values.len(), left_local, need_drop, may_drop);
308                node.kind = ValueKind::RawPtr;
309                node.father = Some(FatherInfo::new(lv, *index));
310                self.values[lv].fields.insert(*index, node.index);
311                self.values.push(node);
312            }
313            lv = *self.values[lv].fields.get(index).unwrap();
314        }
315        for index in fn_alias.rhs_fields().iter() {
316            if !self.values[rv].fields.contains_key(index) {
317                let need_drop = fn_alias.rhs_need_drop;
318                let may_drop = fn_alias.rhs_may_drop;
319                let mut node = Value::new(self.values.len(), right_local, need_drop, may_drop);
320                node.kind = ValueKind::RawPtr;
321                node.father = Some(FatherInfo::new(rv, *index));
322                self.values[rv].fields.insert(*index, node.index);
323                self.values.push(node);
324            }
325            rv = *self.values[rv].fields.get(index).unwrap();
326        }
327        // It is a function call and we should not distinguish left or right;
328        // Merge the alias instead of assign.
329        self.merge_alias(lv, rv);
330    }
331
332    pub fn get_field_seq(&self, value: &Value) -> Vec<usize> {
333        let mut field_id_seq = vec![];
334        let mut node_ref = value;
335        while let Some(father) = &node_ref.father {
336            field_id_seq.push(father.field_id);
337            node_ref = &self.values[father.father_value_id];
338        }
339        field_id_seq
340    }
341
342    /// Checks whether a sequence of field projections on a local MIR variable is valid.
343    /// For example, if the type of a local (e.g., 0) has two fields, 0.2 or 0.3 are both invalid.
344    fn is_valid_field(&self, local: usize, field_seq: &[usize]) -> bool {
345        let body = self.tcx.optimized_mir(self.def_id);
346        let mut ty = body.local_decls[Local::from_usize(local)].ty;
347        for &fidx in field_seq {
348            while let ty::TyKind::Ref(_, inner, _) | ty::TyKind::RawPtr(inner, _) = ty.kind() {
349                ty = *inner;
350            }
351            if let ty::Adt(def, _) = ty.kind() {
352                let field_count = def.all_fields().count();
353                if fidx >= field_count {
354                    return false;
355                }
356            } else {
357                // 不是 ADT（struct/tuple），不能投影 field
358                return false;
359            }
360        }
361        true
362    }
363
364    //merge the result of current path to the final result.
365    pub fn merge_results(&mut self) {
366        rap_debug!("merge results");
367        let f_node: Vec<Option<FatherInfo>> =
368            self.values.iter().map(|v| v.father.clone()).collect();
369        for node in self.values.iter() {
370            if node.local > self.arg_size {
371                continue;
372            }
373            for idx in 1..self.values.len() {
374                if !self.is_aliasing(idx, node.index) {
375                    continue;
376                }
377
378                let mut replace = None;
379                if self.values[idx].local > self.arg_size {
380                    for (i, fidx) in f_node.iter().enumerate() {
381                        if let Some(father_info) = fidx {
382                            if i != idx && i != node.index {
383                                // && father_info.father_value_id == f_node[idx] {
384                                for (j, v) in self.values.iter().enumerate() {
385                                    if j != idx
386                                        && j != node.index
387                                        && self.is_aliasing(j, father_info.father_value_id)
388                                        && v.local <= self.arg_size
389                                    {
390                                        replace = Some(&self.values[j]);
391                                    }
392                                }
393                            }
394                        }
395                    }
396                }
397
398                if (self.values[idx].local <= self.arg_size || replace.is_some())
399                    && idx != node.index
400                    && node.local != self.values[idx].local
401                {
402                    let left_node;
403                    let right_node;
404                    match self.values[idx].local {
405                        0 => {
406                            left_node = match replace {
407                                Some(replace_node) => replace_node,
408                                None => &self.values[idx],
409                            };
410                            right_node = node;
411                        }
412                        _ => {
413                            left_node = node;
414                            right_node = match replace {
415                                Some(replace_node) => replace_node,
416                                None => &self.values[idx],
417                            };
418                        }
419                    }
420                    let mut new_alias = MopAliasPair::new(
421                        left_node.local,
422                        left_node.may_drop,
423                        left_node.need_drop,
424                        right_node.local,
425                        right_node.may_drop,
426                        right_node.need_drop,
427                    );
428                    new_alias.fact.lhs_fields = self.get_field_seq(left_node);
429                    new_alias.fact.rhs_fields = self.get_field_seq(right_node);
430                    if new_alias.left_local() == new_alias.right_local() {
431                        continue;
432                    }
433                    if !self.is_valid_field(left_node.local, &new_alias.fact.lhs_fields)
434                        || !self.is_valid_field(right_node.local, &new_alias.fact.rhs_fields)
435                    {
436                        rap_debug!("new_alias with invalid field: {:?}", new_alias);
437                        continue;
438                    }
439                    rap_debug!("new_alias: {:?}", new_alias);
440                    self.ret_alias.add_alias(new_alias);
441                }
442            }
443        }
444        self.compress_aliases();
445    }
446
447    /// Compresses the alias analysis results with a two-step procedure:
448    ///
449    /// 1. **Field Truncation:**
450    ///    For each alias fact, any `lhs_fields` or `rhs_fields` projection longer than one element
451    ///    is truncated to just its first element (e.g., `1.0.1` becomes `1.0`, `1.2.2.0.0` becomes `1.2`).
452    ///    This aggressively flattens all field projections to a single field level.
453    ///
454    /// 2. **Containment Merging:**
455    ///    For all pairs of alias facts with the same locals, if both the truncated `lhs_fields` and
456    ///    `rhs_fields` of one are a (strict) prefix of another, only the more general (shorter) alias
457    ///    is kept. For example:
458    ///      - Keep (0, 1), remove (0.0, 1.1)
459    ///      - But do **not** merge (0, 1.0) and (0, 1.1), since these have different non-prefix fields.
460    ///
461    /// Call this after constructing the alias set to minimize and canonicalize the result.
462    pub fn compress_aliases(&mut self) {
463        // Step 1: Truncate fields to only the first element if present
464        let mut truncated_facts = Vec::new();
465        for fact in self.ret_alias.alias_set.iter() {
466            let mut new_fact = fact.clone();
467            if !new_fact.fact.lhs_fields.is_empty() {
468                new_fact.fact.lhs_fields = vec![new_fact.fact.lhs_fields[0]];
469            }
470            if !new_fact.fact.rhs_fields.is_empty() {
471                new_fact.fact.rhs_fields = vec![new_fact.fact.rhs_fields[0]];
472            }
473            truncated_facts.push(new_fact);
474        }
475        // Clean up alias set and replace with truncated
476        self.ret_alias.alias_set.clear();
477        for fact in truncated_facts {
478            self.ret_alias.alias_set.insert(fact);
479        }
480
481        // Step 2: Containment merging
482        // For the same (left_local, rhs_local), if (a, b) is a prefix of (a', b'), keep only (a, b)
483        let aliases: Vec<MopAliasPair> = self.ret_alias.alias_set.iter().cloned().collect();
484        let n = aliases.len();
485        let mut to_remove: HashSet<MopAliasPair> = HashSet::new();
486
487        for i in 0..n {
488            for j in 0..n {
489                if i == j || to_remove.contains(&aliases[j]) {
490                    continue;
491                }
492                let a = &aliases[i].fact;
493                let b = &aliases[j].fact;
494                // Only merge if both lhs/rhs locals are equal and BOTH are strict prefixes
495                if a.left_local() == b.left_local() && a.right_local() == b.right_local() {
496                    if a.lhs_fields.len() <= b.lhs_fields.len()
497                    && a.lhs_fields == b.lhs_fields[..a.lhs_fields.len()]
498                    && a.rhs_fields.len() <= b.rhs_fields.len()
499                    && a.rhs_fields == b.rhs_fields[..a.rhs_fields.len()]
500                    // Exclude case where fields are exactly the same (avoid self-removal)
501                    && (a.lhs_fields.len() < b.lhs_fields.len() || a.rhs_fields.len() < b.rhs_fields.len())
502                    {
503                        to_remove.insert(aliases[j].clone());
504                    }
505                }
506            }
507        }
508        for alias in to_remove {
509            self.ret_alias.alias_set.remove(&alias);
510        }
511    }
512
513    #[inline(always)]
514    pub fn find_alias_set(&self, e: usize) -> Option<usize> {
515        self.alias_sets.iter().position(|set| set.contains(&e))
516    }
517
518    #[inline(always)]
519    pub fn is_aliasing(&self, e1: usize, e2: usize) -> bool {
520        let s1 = self.find_alias_set(e1);
521        let s2 = self.find_alias_set(e2);
522        s1.is_some() && s1 == s2
523    }
524
525    pub fn merge_alias(&mut self, e1: usize, e2: usize) {
526        let mut s1 = self.find_alias_set(e1);
527        let mut s2 = self.find_alias_set(e2);
528
529        // Create set for e1 if needed
530        if s1.is_none() {
531            self.alias_sets
532                .push([e1].into_iter().collect::<FxHashSet<usize>>());
533            s1 = Some(self.alias_sets.len() - 1);
534        }
535
536        // Create set for e2 if needed
537        if s2.is_none() {
538            self.alias_sets
539                .push([e2].into_iter().collect::<FxHashSet<usize>>());
540            s2 = Some(self.alias_sets.len() - 1);
541        }
542
543        // After creation, fetch indices (unwrap OK)
544        let idx1 = s1.unwrap();
545        let idx2 = s2.unwrap();
546
547        if idx1 == idx2 {
548            return;
549        }
550
551        let set2 = self.alias_sets.remove(idx2);
552        // If idx2 < idx1, removing idx2 shifts idx1 down by one
553        let idx1 = if idx2 < idx1 { idx1 - 1 } else { idx1 };
554        self.alias_sets[idx1].extend(set2);
555
556        if self.values[e1].fields.len() > 0 {
557            self.sync_field_alias(e2, e1, 0, false);
558        }
559        if self.values[e2].fields.len() > 0 {
560            self.sync_field_alias(e1, e2, 0, false);
561        }
562        if self.values[e1].father != None {
563            self.sync_father_alias(e2, e1, idx1);
564        }
565        if self.values[e2].father != None {
566            self.sync_father_alias(e1, e2, idx1);
567        }
568    }
569
570    #[inline(always)]
571    pub fn get_alias_set(&mut self, e: usize) -> Option<FxHashSet<usize>> {
572        if let Some(idx) = self.find_alias_set(e) {
573            Some(self.alias_sets[idx].clone())
574        } else {
575            None
576        }
577    }
578}
579
580pub fn is_no_alias_intrinsic(def_id: DefId) -> bool {
581    let v = [call_mut_opt(), clone_opt(), take_opt()];
582    contains(&v, def_id)
583}
rapx/analysis/core/alias_analysis/default/alias.rs

rapx/analysis/core/alias_analysis/default/
alias.rs
