source: src/ResolvExpr/ResolveAssertions.cc@ 4a60488

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation new-ast new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 4a60488 was 7d01cf44, checked in by Andrew Beach <ajbeach@…>, 6 years ago

lvalue is now read through the expression.
  • Property mode set to 100644
File size: 18.0 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 : Andrew Beach
12// Last Modified On : Thu Aug 8 16:47:00 2019
13// Update Count : 3
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( const 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 assert( !assn.match.adjType->get_lvalue() );
159 k += computeConversionCost(
160 assn.match.adjType, assn.decl->get_type(), false, indexer, x.env );
161
162 // mark vars+specialization cost on function-type assertions
163 FunctionType* func = GenPoly::getFunctionType( assn.match.cdata.id->get_type() );
164 if ( ! func ) continue;
165
166 for ( DeclarationWithType* formal : func->parameters ) {
167 k.decSpec( specCost( formal->get_type() ) );
168 }
169 k.incVar( func->forall.size() );
170 for ( TypeDecl* td : func->forall ) {
171 k.decSpec( td->assertions.size() );
172 }
173 }
174
175 // cache and return
176 x.cost = k;
177 return k;
178 }
179
180 /// compares elements by cost
181 bool operator() ( Element& a, Element& b ) const {
182 return get( a ) < get( b );
183 }
184 };
185
186 /// Set of assertion resolutions, grouped by resolution ID
187 using InferCache = std::unordered_map< UniqueId, InferredParams >;
188
189 /// Lexicographically-ordered vector of costs
190 using CostVec = std::vector< Cost >;
191
192 int compare( const CostVec & a, const CostVec & b ) {
193 unsigned i = 0;
194 do {
195 // lex-compare where shorter one is less
196 if ( i == a.size() ) {
197 return i == b.size() ? 0 : -1;
198 }
199 if ( i == b.size() /* && i < a.size() */ ) return 1;
200
201 int c = a[i].compare( b[i] );
202 if ( c != 0 ) return c;
203 } while ( ++i );
204 assert(!"unreachable");
205 }
206
207 bool operator< ( const CostVec & a, const CostVec & b ) { return compare( a, b ) < 0; }
208
209 /// Flag for state iteration
210 enum IterateFlag { IterateState };
211
212 /// State needed to resolve a set of assertions
213 struct ResnState {
214 Alternative alt; ///< Alternative assertion is rooted on
215 AssertionList need; ///< Assertions to find
216 AssertionSet newNeed; ///< New assertions for current resolutions
217 DeferList deferred; ///< Deferred matches
218 InferCache inferred; ///< Cache of already-inferred parameters
219 CostVec costs; ///< Costs of recursive assertion satisfaction for disambiguation
220 SymTab::Indexer& indexer; ///< Name lookup (depends on previous assertions)
221
222 /// Initial resolution state for an alternative
223 ResnState( Alternative & a, SymTab::Indexer & indexer )
224 : alt(a), need(), newNeed(), deferred(), inferred(), costs{ Cost::zero }, indexer(indexer) {
225 need.swap( a.need );
226 }
227
228 /// Updated resolution state with new need-list
229 ResnState( ResnState && o, IterateFlag )
230 : alt(std::move(o.alt)), need(o.newNeed.begin(), o.newNeed.end()), newNeed(), deferred(),
231 inferred(std::move(o.inferred)), costs(o.costs), indexer(o.indexer) {
232 costs.emplace_back( Cost::zero );
233 }
234 };
235
236 /// Binds a single assertion, updating resolution state
237 void bindAssertion( const DeclarationWithType * decl, AssertionSetValue info, Alternative & alt,
238 AssnCandidate & match, InferCache & inferred ) {
239
240 const DeclarationWithType * candidate = match.cdata.id;
241 assertf( candidate->uniqueId, "Assertion candidate does not have a unique ID: %s", toString( candidate ).c_str() );
242
243 Expression * varExpr = match.cdata.combine( alt.cvtCost );
244 delete varExpr->result;
245 varExpr->result = match.adjType->clone();
246 if ( match.resnSlot ) { varExpr->resnSlots.push_back( match.resnSlot ); }
247
248 // place newly-inferred assertion in proper place in cache
249 inferred[ info.resnSlot ][ decl->get_uniqueId() ] = ParamEntry{
250 candidate->uniqueId, candidate->clone(), match.adjType->clone(), decl->get_type()->clone(),
251 varExpr };
252 }
253
254 /// Adds a captured assertion to the symbol table
255 void addToIndexer( AssertionSet & assertSet, SymTab::Indexer & indexer ) {
256 for ( auto& i : assertSet ) {
257 if ( i.second.isUsed ) {
258 indexer.addId( i.first );
259 }
260 }
261 }
262
263 // in AlternativeFinder.cc; unique ID for assertion resolutions
264 extern UniqueId globalResnSlot;
265
266 /// Resolve a single assertion, in context
267 bool resolveAssertion( AssertionItem & assn, ResnState & resn ) {
268 // skip unused assertions
269 if ( ! assn.info.isUsed ) return true;
270
271 // lookup candidates for this assertion
272 std::list< SymTab::Indexer::IdData > candidates;
273 resn.indexer.lookupId( assn.decl->name, candidates );
274
275 // find the candidates that unify with the desired type
276 CandidateList matches;
277 for ( const auto & cdata : candidates ) {
278 const DeclarationWithType * candidate = cdata.id;
279
280 // build independent unification context for candidate
281 AssertionSet have, newNeed;
282 TypeEnvironment newEnv{ resn.alt.env };
283 OpenVarSet newOpenVars{ resn.alt.openVars };
284 Type * adjType = candidate->get_type()->clone();
285 adjustExprType( adjType, newEnv, resn.indexer );
286 renameTyVars( adjType );
287
288 // keep unifying candidates
289 if ( unify( assn.decl->get_type(), adjType, newEnv, newNeed, have, newOpenVars,
290 resn.indexer ) ) {
291 // set up binding slot for recursive assertions
292 UniqueId crntResnSlot = 0;
293 if ( ! newNeed.empty() ) {
294 crntResnSlot = ++globalResnSlot;
295 for ( auto& a : newNeed ) {
296 a.second.resnSlot = crntResnSlot;
297 }
298 }
299
300 matches.emplace_back( cdata, adjType, std::move(newEnv), std::move(have),
301 std::move(newNeed), std::move(newOpenVars), crntResnSlot );
302 } else {
303 delete adjType;
304 }
305 }
306
307 // break if no suitable assertion
308 if ( matches.empty() ) return false;
309
310 // defer if too many suitable assertions
311 if ( matches.size() > 1 ) {
312 resn.deferred.emplace_back( assn.decl, assn.info, std::move(matches) );
313 return true;
314 }
315
316 // otherwise bind current match in ongoing scope
317 AssnCandidate& match = matches.front();
318 addToIndexer( match.have, resn.indexer );
319 resn.newNeed.insert( match.need.begin(), match.need.end() );
320 resn.alt.env = std::move(match.env);
321 resn.alt.openVars = std::move(match.openVars);
322
323 bindAssertion( assn.decl, assn.info, resn.alt, match, resn.inferred );
324 return true;
325 }
326
327 /// Associates inferred parameters with an expression
328 struct InferMatcher {
329 InferCache& inferred;
330
331 InferMatcher( InferCache& inferred ) : inferred( inferred ) {}
332
333 Expression* postmutate( Expression* expr ) {
334 // defer missing inferred parameters until they are hopefully found later
335 std::vector<UniqueId> missingSlots;
336 // place inferred parameters into resolution slots
337 for ( UniqueId slot : expr->resnSlots ) {
338 // fail if no matching parameters found
339 auto it = inferred.find( slot );
340 if ( it == inferred.end() ) {
341 missingSlots.push_back( slot );
342 continue;
343 }
344 InferredParams& inferParams = it->second;
345
346 // place inferred parameters into proper place in expression
347 for ( auto& entry : inferParams ) {
348 // recurse on inferParams of resolved expressions
349 entry.second.expr = postmutate( entry.second.expr );
350 // xxx - look at entry.second.inferParams?
351 auto res = expr->inferParams.emplace( entry.first, entry.second );
352 assert(res.second);
353 }
354 }
355
356 // clear resolution slots and return
357 expr->resnSlots.swap( missingSlots );
358 return expr;
359 }
360 };
361
362 /// Map of alternative return types to recursive assertion satisfaction costs
363 using PruneMap = std::unordered_map<std::string, CostVec>;
364
365 /// Gets the pruning key for an alternative
366 std::string pruneKey( const Alternative & alt ) {
367 Type* resType = alt.expr->result->clone();
368 alt.env.apply( resType );
369 std::string resKey = SymTab::Mangler::mangleType( resType );
370 delete resType;
371 return resKey;
372 }
373
374 /// Replace resnSlots with inferParams and add alternative to output list, if meets pruning
375 /// threshold.
376 void finalizeAssertions( ResnState& resn, PruneMap & pruneThresholds, AltList& out ) {
377 // prune if cheaper alternative for same key has already been generated
378 std::string resKey = pruneKey( resn.alt );
379 auto it = pruneThresholds.find( resKey );
380 if ( it != pruneThresholds.end() ) {
381 if ( it->second < resn.costs ) return;
382 } else {
383 pruneThresholds.emplace_hint( it, resKey, resn.costs );
384 }
385
386 // replace resolution slots with inferred params, add to output
387 PassVisitor<InferMatcher> matcher{ resn.inferred };
388 resn.alt.expr = resn.alt.expr->acceptMutator( matcher );
389 out.emplace_back( resn.alt );
390 }
391
392 /// Limit to depth of recursion of assertion satisfaction
393 static const int recursionLimit = 4;
394 /// Maximum number of simultaneously-deferred assertions to attempt concurrent satisfaction of
395 static const int deferLimit = 10;
396
397 void resolveAssertions( Alternative& alt, const SymTab::Indexer& indexer, AltList& out, std::list<std::string>& errors ) {
398 // finish early if no assertions to resolve
399 if ( alt.need.empty() ) {
400 out.emplace_back( alt );
401 return;
402 }
403
404 // build list of possible resolutions
405 using ResnList = std::vector<ResnState>;
406 SymTab::Indexer root_indexer{ indexer };
407 ResnList resns{ ResnState{ alt, root_indexer } };
408 ResnList new_resns{};
409
410 // Pruning thresholds by result type of the output alternatives.
411 // Alternatives *should* be generated in sorted order, so no need to retroactively prune
412 PruneMap thresholds;
413
414 // resolve assertions in breadth-first-order up to a limited number of levels deep
415 for ( unsigned level = 0; level < recursionLimit; ++level ) {
416 // scan over all mutually-compatible resolutions
417 for ( auto& resn : resns ) {
418 // stop this branch if already found a better option
419 auto it = thresholds.find( pruneKey( resn.alt ) );
420 if ( it != thresholds.end() && it->second < resn.costs ) goto nextResn;
421
422 // make initial pass at matching assertions
423 for ( auto& assn : resn.need ) {
424 // fail early if any assertion is not resolvable
425 if ( ! resolveAssertion( assn, resn ) ) {
426 Indenter tabs{ 3 };
427 std::ostringstream ss;
428 ss << tabs << "Unsatisfiable alternative:\n";
429 resn.alt.print( ss, ++tabs );
430 ss << (tabs-1) << "Could not satisfy assertion:\n";
431 assn.decl->print( ss, tabs );
432
433 errors.emplace_back( ss.str() );
434 goto nextResn;
435 }
436 }
437
438 if ( resn.deferred.empty() ) {
439 // either add successful match or push back next state
440 if ( resn.newNeed.empty() ) {
441 finalizeAssertions( resn, thresholds, out );
442 } else {
443 new_resns.emplace_back( std::move(resn), IterateState );
444 }
445 } else if ( resn.deferred.size() > deferLimit ) {
446 // too many deferred assertions to attempt mutual compatibility
447 Indenter tabs{ 3 };
448 std::ostringstream ss;
449 ss << tabs << "Unsatisfiable alternative:\n";
450 resn.alt.print( ss, ++tabs );
451 ss << (tabs-1) << "Too many non-unique satisfying assignments for "
452 "assertions:\n";
453 for ( const auto& d : resn.deferred ) {
454 d.decl->print( ss, tabs );
455 }
456
457 errors.emplace_back( ss.str() );
458 goto nextResn;
459 } else {
460 // resolve deferred assertions by mutual compatibility
461 std::vector<CandidateEnvMerger::OutType> compatible = filterCombos(
462 resn.deferred,
463 CandidateEnvMerger{ resn.alt.env, resn.alt.openVars, resn.indexer } );
464 // fail early if no mutually-compatible assertion satisfaction
465 if ( compatible.empty() ) {
466 Indenter tabs{ 3 };
467 std::ostringstream ss;
468 ss << tabs << "Unsatisfiable alternative:\n";
469 resn.alt.print( ss, ++tabs );
470 ss << (tabs-1) << "No mutually-compatible satisfaction for assertions:\n";
471 for ( const auto& d : resn.deferred ) {
472 d.decl->print( ss, tabs );
473 }
474
475 errors.emplace_back( ss.str() );
476 goto nextResn;
477 }
478 // sort by cost for overall pruning
479 CandidateCost coster{ resn.indexer };
480 std::sort( compatible.begin(), compatible.end(), coster );
481
482 for ( auto& compat : compatible ) {
483 ResnState new_resn = resn;
484
485 // add compatible assertions to new resolution state
486 for ( DeferRef r : compat.assns ) {
487 AssnCandidate match = r.match;
488 addToIndexer( match.have, new_resn.indexer );
489 new_resn.newNeed.insert( match.need.begin(), match.need.end() );
490
491 bindAssertion( r.decl, r.info, new_resn.alt, match, new_resn.inferred );
492 }
493
494 // set mutual environment into resolution state
495 new_resn.alt.env = std::move(compat.env);
496 new_resn.alt.openVars = std::move(compat.openVars);
497
498 // mark cost of this path
499 new_resn.costs.back() += compat.cost;
500
501 // either add sucessful match or push back next state
502 if ( new_resn.newNeed.empty() ) {
503 finalizeAssertions( new_resn, thresholds, out );
504 } else {
505 new_resns.emplace_back( std::move(new_resn), IterateState );
506 }
507 }
508 }
509 nextResn:; }
510
511 // finish or reset for next round
512 if ( new_resns.empty() ) return;
513 resns.swap( new_resns );
514 new_resns.clear();
515 }
516
517 // exceeded recursion limit if reaches here
518 if ( out.empty() ) {
519 SemanticError( alt.expr->location, "Too many recursive assertions" );
520 }
521 }
522} // namespace ResolvExpr
523
524// Local Variables: //
525// tab-width: 4 //
526// mode: c++ //
527// compile-command: "make install" //
528// End: //
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