source: src/ResolvExpr/ResolveAssertions.cc@ 6e3e0717

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation jenkins-sandbox new-ast new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 6e3e0717 was d3b2c32a, checked in by Aaron Moss <a3moss@…>, 6 years ago

Add limit to number of recursive assertions tried at once
  • Property mode set to 100644
File size: 16.5 KB
Line 
1//
2// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
3//
4// The contents of this file are covered under the licence agreement in the
5// file "LICENCE" distributed with Cforall.
6//
7// ResolveAssertions.cc --
8//
9// Author : Aaron B. Moss
10// Created On : Fri Oct 05 13:46:00 2018
11// Last Modified By : Aaron B. Moss
12// Last Modified On : Fri Oct 05 13:46:00 2018
13// Update Count : 1
14//
15
16#include "ResolveAssertions.h"
17
18#include <algorithm> // for sort
19#include <cassert> // for assertf
20#include <list> // for list
21#include <memory> // for unique_ptr
22#include <sstream> // for ostringstream
23#include <string> // for string
24#include <unordered_map> // for unordered_map, unordered_multimap
25#include <utility> // for move
26#include <vector> // for vector
27
28#include "Alternative.h" // for Alternative, AssertionItem, AssertionList
29#include "Common/FilterCombos.h" // for filterCombos
30#include "Common/Indenter.h" // for Indenter
31#include "Common/utility.h" // for sort_mins
32#include "GenPoly/GenPoly.h" // for getFunctionType
33#include "ResolvExpr/RenameVars.h" // for renameTyVars
34#include "SymTab/Indexer.h" // for Indexer
35#include "SymTab/Mangler.h" // for Mangler
36#include "SynTree/Expression.h" // for InferredParams
37#include "TypeEnvironment.h" // for TypeEnvironment, etc.
38#include "typeops.h" // for adjustExprType, specCost
39#include "Unify.h" // for unify
40
41namespace ResolvExpr {
42 /// Unified assertion candidate
43 struct AssnCandidate {
44 SymTab::Indexer::IdData cdata; ///< Satisfying declaration
45 Type* adjType; ///< Satisfying type
46 TypeEnvironment env; ///< Post-unification environment
47 AssertionSet have; ///< Post-unification have-set
48 AssertionSet need; ///< Post-unification need-set
49 OpenVarSet openVars; ///< Post-unification open-var set
50 UniqueId resnSlot; ///< Slot for any recursive assertion IDs
51
52 AssnCandidate( const SymTab::Indexer::IdData& cdata, Type* adjType, TypeEnvironment&& env,
53 AssertionSet&& have, AssertionSet&& need, OpenVarSet&& openVars, UniqueId resnSlot )
54 : cdata(cdata), adjType(adjType), env(std::move(env)), have(std::move(have)),
55 need(std::move(need)), openVars(std::move(openVars)), resnSlot(resnSlot) {}
56 };
57
58 /// List of candidate assertion resolutions
59 using CandidateList = std::vector<AssnCandidate>;
60
61 /// Reference to single deferred item
62 struct DeferRef {
63 const DeclarationWithType* decl;
64 const AssertionSetValue& info;
65 const AssnCandidate& match;
66 };
67
68 /// Wrapper for the deferred items from a single assertion resolution.
69 /// Acts like indexed list of DeferRef
70 struct DeferItem {
71 const DeclarationWithType* decl;
72 const AssertionSetValue& info;
73 CandidateList matches;
74
75 DeferItem( DeclarationWithType* decl, const AssertionSetValue& info, CandidateList&& matches )
76 : decl(decl), info(info), matches(std::move(matches)) {}
77
78 bool empty() const { return matches.empty(); }
79
80 CandidateList::size_type size() const { return matches.size(); }
81
82 DeferRef operator[] ( unsigned i ) const { return { decl, info, matches[i] }; }
83 };
84
85 /// List of deferred resolution items
86 using DeferList = std::vector<DeferItem>;
87
88 /// Combo iterator that combines candidates into an output list, merging their environments.
89 /// Rejects an appended candidate if the environments cannot be merged.
90 class CandidateEnvMerger {
91 /// Current list of merged candidates
92 std::vector<DeferRef> crnt;
93 /// Stack of environments to support backtracking
94 std::vector<TypeEnvironment> envs;
95 /// Stack of open variables to support backtracking
96 std::vector<OpenVarSet> varSets;
97 /// Indexer to use for merges
98 const SymTab::Indexer& indexer;
99
100 public:
101 /// The merged environment/open variables and the list of candidates
102 struct OutType {
103 TypeEnvironment env;
104 OpenVarSet openVars;
105 std::vector<DeferRef> assns;
106 Cost cost;
107
108 OutType( const TypeEnvironment& env, const OpenVarSet& openVars,
109 const std::vector<DeferRef>& assns )
110 : env(env), openVars(openVars), assns(assns), cost(Cost::infinity) {}
111 };
112
113 CandidateEnvMerger( const TypeEnvironment& env, const OpenVarSet& openVars,
114 const SymTab::Indexer& indexer )
115 : crnt(), envs{ env }, varSets{ openVars }, indexer(indexer) {}
116
117 bool append( DeferRef i ) {
118 TypeEnvironment env = envs.back();
119 OpenVarSet openVars = varSets.back();
120 mergeOpenVars( openVars, i.match.openVars );
121
122 if ( ! env.combine( i.match.env, openVars, indexer ) ) return false;
123
124 crnt.emplace_back( i );
125 envs.emplace_back( env );
126 varSets.emplace_back( openVars );
127 return true;
128 }
129
130 void backtrack() {
131 crnt.pop_back();
132 envs.pop_back();
133 varSets.pop_back();
134 }
135
136 OutType finalize() { return { envs.back(), varSets.back(), crnt }; }
137 };
138
139 /// Comparator for CandidateEnvMerger outputs that sums their costs and caches the stored
140 /// sums
141 struct CandidateCost {
142 using Element = CandidateEnvMerger::OutType;
143 private:
144 const SymTab::Indexer& indexer; ///< Indexer for costing
145
146 public:
147 CandidateCost( const SymTab::Indexer& indexer ) : indexer(indexer) {}
148
149 /// reports the cost of an element
150 Cost get( Element& x ) const {
151 // check cached cost
152 if ( x.cost != Cost::infinity ) return x.cost;
153
154 // generate cost
155 Cost k = Cost::zero;
156 for ( const auto& assn : x.assns ) {
157 // compute conversion cost from satisfying decl to assertion
158 k += computeConversionCost(
159 assn.match.adjType, assn.decl->get_type(), indexer, x.env );
160
161 // mark vars+specialization cost on function-type assertions
162 FunctionType* func = GenPoly::getFunctionType( assn.match.cdata.id->get_type() );
163 if ( ! func ) continue;
164
165 for ( DeclarationWithType* formal : func->parameters ) {
166 k.decSpec( specCost( formal->get_type() ) );
167 }
168 k.incVar( func->forall.size() );
169 for ( TypeDecl* td : func->forall ) {
170 k.decSpec( td->assertions.size() );
171 }
172 }
173
174 // cache and return
175 x.cost = k;
176 return k;
177 }
178
179 /// compares elements by cost
180 bool operator() ( Element& a, Element& b ) const {
181 return get( a ) < get( b );
182 }
183 };
184
185 /// Set of assertion resolutions, grouped by resolution ID
186 using InferCache = std::unordered_map< UniqueId, InferredParams >;
187
188 /// Flag for state iteration
189 enum IterateFlag { IterateState };
190
191 /// State needed to resolve a set of assertions
192 struct ResnState {
193 Alternative alt; ///< Alternative assertion is rooted on
194 AssertionList need; ///< Assertions to find
195 AssertionSet newNeed; ///< New assertions for current resolutions
196 DeferList deferred; ///< Deferred matches
197 InferCache inferred; ///< Cache of already-inferred parameters
198 SymTab::Indexer& indexer; ///< Name lookup (depends on previous assertions)
199
200 /// Initial resolution state for an alternative
201 ResnState( Alternative& a, SymTab::Indexer& indexer )
202 : alt(a), need(), newNeed(), deferred(), inferred(), indexer(indexer) {
203 need.swap( a.need );
204 }
205
206 /// Updated resolution state with new need-list
207 ResnState( ResnState&& o, IterateFlag )
208 : alt(std::move(o.alt)), need(o.newNeed.begin(), o.newNeed.end()), newNeed(), deferred(),
209 inferred(std::move(o.inferred)), indexer(o.indexer) {}
210 };
211
212 /// Binds a single assertion, updating resolution state
213 void bindAssertion( const DeclarationWithType* decl, AssertionSetValue info, Alternative& alt,
214 AssnCandidate& match, InferCache& inferred ) {
215
216 DeclarationWithType* candidate = match.cdata.id;
217 assertf( candidate->get_uniqueId(), "Assertion candidate does not have a unique ID: %s", toString( candidate ).c_str() );
218
219 Expression* varExpr = match.cdata.combine( alt.cvtCost );
220 delete varExpr->result;
221 varExpr->result = match.adjType->clone();
222 if ( match.resnSlot ) { varExpr->resnSlots.push_back( match.resnSlot ); }
223
224 // place newly-inferred assertion in proper place in cache
225 inferred[ info.resnSlot ][ decl->get_uniqueId() ] = ParamEntry{
226 candidate->get_uniqueId(), match.adjType->clone(), decl->get_type()->clone(),
227 varExpr };
228 }
229
230 /// Adds a captured assertion to the symbol table
231 void addToIndexer( AssertionSet &assertSet, SymTab::Indexer &indexer ) {
232 for ( auto& i : assertSet ) {
233 if ( i.second.isUsed ) {
234 indexer.addId( i.first );
235 }
236 }
237 }
238
239 // in AlternativeFinder.cc; unique ID for assertion resolutions
240 extern UniqueId globalResnSlot;
241
242 /// Resolve a single assertion, in context
243 bool resolveAssertion( AssertionItem& assn, ResnState& resn ) {
244 // skip unused assertions
245 if ( ! assn.info.isUsed ) return true;
246
247 // lookup candidates for this assertion
248 std::list< SymTab::Indexer::IdData > candidates;
249 resn.indexer.lookupId( assn.decl->name, candidates );
250
251 // find the candidates that unify with the desired type
252 CandidateList matches;
253 for ( const auto& cdata : candidates ) {
254 DeclarationWithType* candidate = cdata.id;
255
256 // build independent unification context for candidate
257 AssertionSet have, newNeed;
258 TypeEnvironment newEnv{ resn.alt.env };
259 OpenVarSet newOpenVars{ resn.alt.openVars };
260 Type* adjType = candidate->get_type()->clone();
261 adjustExprType( adjType, newEnv, resn.indexer );
262 renameTyVars( adjType );
263
264 // keep unifying candidates
265 if ( unify( assn.decl->get_type(), adjType, newEnv, newNeed, have, newOpenVars,
266 resn.indexer ) ) {
267 // set up binding slot for recursive assertions
268 UniqueId crntResnSlot = 0;
269 if ( ! newNeed.empty() ) {
270 crntResnSlot = ++globalResnSlot;
271 for ( auto& a : newNeed ) {
272 a.second.resnSlot = crntResnSlot;
273 }
274 }
275
276 matches.emplace_back( cdata, adjType, std::move(newEnv), std::move(have),
277 std::move(newNeed), std::move(newOpenVars), crntResnSlot );
278 } else {
279 delete adjType;
280 }
281 }
282
283 // break if no suitable assertion
284 if ( matches.empty() ) return false;
285
286 // defer if too many suitable assertions
287 if ( matches.size() > 1 ) {
288 resn.deferred.emplace_back( assn.decl, assn.info, std::move(matches) );
289 return true;
290 }
291
292 // otherwise bind current match in ongoing scope
293 AssnCandidate& match = matches.front();
294 addToIndexer( match.have, resn.indexer );
295 resn.newNeed.insert( match.need.begin(), match.need.end() );
296 resn.alt.env = std::move(match.env);
297 resn.alt.openVars = std::move(match.openVars);
298
299 bindAssertion( assn.decl, assn.info, resn.alt, match, resn.inferred );
300 return true;
301 }
302
303 /// Associates inferred parameters with an expression
304 struct InferMatcher {
305 InferCache& inferred;
306
307 InferMatcher( InferCache& inferred ) : inferred( inferred ) {}
308
309 Expression* postmutate( Expression* expr ) {
310 // defer missing inferred parameters until they are hopefully found later
311 std::vector<UniqueId> missingSlots;
312 // place inferred parameters into resolution slots
313 for ( UniqueId slot : expr->resnSlots ) {
314 // fail if no matching parameters found
315 auto it = inferred.find( slot );
316 if ( it == inferred.end() ) {
317 missingSlots.push_back( slot );
318 continue;
319 }
320 InferredParams& inferParams = it->second;
321
322 // place inferred parameters into proper place in expression
323 for ( auto& entry : inferParams ) {
324 // recurse on inferParams of resolved expressions
325 entry.second.expr = postmutate( entry.second.expr );
326 // xxx - look at entry.second.inferParams?
327 expr->inferParams[ entry.first ] = entry.second;
328 }
329 }
330
331 // clear resolution slots and return
332 expr->resnSlots.swap( missingSlots );
333 return expr;
334 }
335 };
336
337 void finalizeAssertions( Alternative& alt, InferCache& inferred, AltList& out ) {
338 PassVisitor<InferMatcher> matcher{ inferred };
339 alt.expr = alt.expr->acceptMutator( matcher );
340 out.emplace_back( alt );
341 }
342
343 /// Limit to depth of recursion of assertion satisfaction
344 static const int recursionLimit = 4;
345 /// Maximum number of simultaneously-deferred assertions to attempt concurrent satisfaction of
346 static const int deferLimit = 10;
347
348 void resolveAssertions( Alternative& alt, const SymTab::Indexer& indexer, AltList& out, std::list<std::string>& errors ) {
349 // finish early if no assertions to resolve
350 if ( alt.need.empty() ) {
351 out.emplace_back( alt );
352 return;
353 }
354
355 // build list of possible resolutions
356 using ResnList = std::vector<ResnState>;
357 SymTab::Indexer root_indexer{ indexer };
358 ResnList resns{ ResnState{ alt, root_indexer } };
359 ResnList new_resns{};
360
361 // resolve assertions in breadth-first-order up to a limited number of levels deep
362 for ( unsigned level = 0; level < recursionLimit; ++level ) {
363 // scan over all mutually-compatible resolutions
364 for ( auto& resn : resns ) {
365 // make initial pass at matching assertions
366 for ( auto& assn : resn.need ) {
367 // fail early if any assertion is not resolvable
368 if ( ! resolveAssertion( assn, resn ) ) {
369 Indenter tabs{ 3 };
370 std::ostringstream ss;
371 ss << tabs << "Unsatisfiable alternative:\n";
372 resn.alt.print( ss, ++tabs );
373 ss << (tabs-1) << "Could not satisfy assertion:\n";
374 assn.decl->print( ss, tabs );
375
376 errors.emplace_back( ss.str() );
377 goto nextResn;
378 }
379 }
380
381 if ( resn.deferred.empty() ) {
382 // either add successful match or push back next state
383 if ( resn.newNeed.empty() ) {
384 finalizeAssertions( resn.alt, resn.inferred, out );
385 } else {
386 new_resns.emplace_back( std::move(resn), IterateState );
387 }
388 } else if ( resn.deferred.size() > deferLimit ) {
389 // too many deferred assertions to attempt mutual compatibility
390 Indenter tabs{ 3 };
391 std::ostringstream ss;
392 ss << tabs << "Unsatisfiable alternative:\n";
393 resn.alt.print( ss, ++tabs );
394 ss << (tabs-1) << "Too many non-unique satisfying assignments for "
395 "assertions:\n";
396 for ( const auto& d : resn.deferred ) {
397 d.decl->print( ss, tabs );
398 }
399
400 errors.emplace_back( ss.str() );
401 goto nextResn;
402 } else {
403 // resolve deferred assertions by mutual compatibility
404 std::vector<CandidateEnvMerger::OutType> compatible = filterCombos(
405 resn.deferred,
406 CandidateEnvMerger{ resn.alt.env, resn.alt.openVars, resn.indexer } );
407 // fail early if no mutually-compatible assertion satisfaction
408 if ( compatible.empty() ) {
409 Indenter tabs{ 3 };
410 std::ostringstream ss;
411 ss << tabs << "Unsatisfiable alternative:\n";
412 resn.alt.print( ss, ++tabs );
413 ss << (tabs-1) << "No mutually-compatible satisfaction for assertions:\n";
414 for ( const auto& d : resn.deferred ) {
415 d.decl->print( ss, tabs );
416 }
417
418 errors.emplace_back( ss.str() );
419 goto nextResn;
420 }
421 // sort by cost
422 CandidateCost coster{ resn.indexer };
423 std::sort( compatible.begin(), compatible.end(), coster );
424
425 // keep map of detected options
426 std::unordered_map<std::string, Cost> found;
427 for ( auto& compat : compatible ) {
428 // filter by environment-adjusted result type, keep only cheapest option
429 Type* resType = alt.expr->result->clone();
430 compat.env.apply( resType );
431 // skip if cheaper alternative already processed with same result type
432 Cost resCost = coster.get( compat );
433 auto it = found.emplace( SymTab::Mangler::mangleType( resType ), resCost );
434 delete resType;
435 if ( it.second == false && it.first->second < resCost ) continue;
436
437 // proceed with resolution step
438 ResnState new_resn = resn;
439
440 // add compatible assertions to new resolution state
441 for ( DeferRef r : compat.assns ) {
442 AssnCandidate match = r.match;
443 addToIndexer( match.have, new_resn.indexer );
444 new_resn.newNeed.insert( match.need.begin(), match.need.end() );
445
446 bindAssertion( r.decl, r.info, new_resn.alt, match, new_resn.inferred );
447 }
448
449 // set mutual environment into resolution state
450 new_resn.alt.env = std::move(compat.env);
451 new_resn.alt.openVars = std::move(compat.openVars);
452
453 // either add sucessful match or push back next state
454 if ( new_resn.newNeed.empty() ) {
455 finalizeAssertions( new_resn.alt, new_resn.inferred, out );
456 } else {
457 new_resns.emplace_back( std::move(new_resn), IterateState );
458 }
459 }
460 }
461 nextResn:; }
462
463 // finish or reset for next round
464 if ( new_resns.empty() ) return;
465 resns.swap( new_resns );
466 new_resns.clear();
467 }
468
469 // exceeded recursion limit if reaches here
470 if ( out.empty() ) {
471 SemanticError( alt.expr->location, "Too many recursive assertions" );
472 }
473 }
474} // namespace ResolvExpr
475
476// Local Variables: //
477// tab-width: 4 //
478// mode: c++ //
479// compile-command: "make install" //
480// End: //
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