source: src/ResolvExpr/SatisfyAssertions.cpp@ 09a767e

Last change on this file since 09a767e was da4a570, checked in by caparsons <caparson@…>, 2 years ago

commented out some debugging code
  • Property mode set to 100644
File size: 20.8 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// SatisfyAssertions.cpp --
8//
9// Author : Aaron B. Moss
10// Created On : Mon Jun 10 17:45:00 2019
11// Last Modified By : Andrew Beach
12// Last Modified On : Tue Oct 1 13:56:00 2019
13// Update Count : 2
14//
15
16#include "SatisfyAssertions.hpp"
17
18#include <iostream>
19#include <algorithm>
20#include <cassert>
21#include <sstream>
22#include <string>
23#include <unordered_map>
24#include <vector>
25
26#include "AdjustExprType.hpp"
27#include "Candidate.hpp"
28#include "CandidateFinder.hpp"
29#include "CommonType.hpp"
30#include "Cost.h"
31#include "RenameVars.h"
32#include "SpecCost.hpp"
33#include "typeops.h"
34#include "Unify.h"
35#include "AST/Decl.hpp"
36#include "AST/Expr.hpp"
37#include "AST/Node.hpp"
38#include "AST/Pass.hpp"
39#include "AST/Print.hpp"
40#include "AST/SymbolTable.hpp"
41#include "AST/TypeEnvironment.hpp"
42#include "FindOpenVars.h"
43#include "Common/FilterCombos.h"
44#include "Common/Indenter.h"
45#include "GenPoly/GenPoly.h"
46#include "SymTab/Mangler.h"
47
48
49
50namespace ResolvExpr {
51
52// in CandidateFinder.cpp; unique ID for assertion satisfaction
53extern UniqueId globalResnSlot;
54
55namespace {
56 /// Post-unification assertion satisfaction candidate
57 struct AssnCandidate {
58 ast::SymbolTable::IdData cdata; ///< Satisfying declaration
59 ast::ptr< ast::Type > adjType; ///< Satisfying type
60 ast::TypeEnvironment env; ///< Post-unification environment
61 ast::AssertionSet have; ///< Post-unification have-set
62 ast::AssertionSet need; ///< Post-unification need-set
63 ast::OpenVarSet open; ///< Post-unification open-var-set
64 ast::UniqueId resnSlot; ///< Slot for any recursive assertion IDs
65
66 AssnCandidate(
67 const ast::SymbolTable::IdData c, const ast::Type * at, ast::TypeEnvironment && e,
68 ast::AssertionSet && h, ast::AssertionSet && n, ast::OpenVarSet && o, ast::UniqueId rs )
69 : cdata( c ), adjType( at ), env( std::move( e ) ), have( std::move( h ) ),
70 need( std::move( n ) ), open( std::move( o ) ), resnSlot( rs ) {
71 if (!have.empty()) {
72 // std::cerr << c.id->location << ':' << c.id->name << std::endl; // I think this was debugging code so I commented it
73 }
74 }
75 };
76
77 /// List of assertion satisfaction candidates
78 using AssnCandidateList = std::vector< AssnCandidate >;
79
80 /// Reference to a single deferred item
81 struct DeferRef {
82 const ast::VariableExpr * expr;
83 const ast::AssertionSetValue & info;
84 const AssnCandidate & match;
85 };
86
87 /// Wrapper for the deferred items from a single assertion satisfaction.
88 /// Acts like an indexed list of DeferRef
89 struct DeferItem {
90 const ast::VariableExpr * expr;
91 const ast::AssertionSetValue & info;
92 AssnCandidateList matches;
93
94 DeferItem(
95 const ast::VariableExpr * d, const ast::AssertionSetValue & i, AssnCandidateList && ms )
96 : expr( d ), info( i ), matches( std::move( ms ) ) {}
97
98 bool empty() const { return matches.empty(); }
99
100 AssnCandidateList::size_type size() const { return matches.size(); }
101
102 DeferRef operator[] ( unsigned i ) const { return { expr, info, matches[i] }; }
103 };
104
105 /// List of deferred satisfaction items
106 using DeferList = std::vector< DeferItem >;
107
108 /// Set of assertion satisfactions, grouped by resolution ID
109 using InferCache = std::unordered_map< ast::UniqueId, ast::InferredParams >;
110
111 /// Lexicographically-ordered vector of costs.
112 /// Lexicographic order comes from default operator< on std::vector.
113 using CostVec = std::vector< Cost >;
114
115 /// Flag for state iteration
116 enum IterateFlag { IterateState };
117
118 /// Intermediate state for satisfying a set of assertions
119 struct SatState {
120 CandidateRef cand; ///< Candidate assertion is rooted on
121 ast::AssertionList need; ///< Assertions to find
122 ast::AssertionSet newNeed; ///< Recursive assertions from current satisfied assertions
123 DeferList deferred; ///< Deferred matches
124 InferCache inferred; ///< Cache of already-inferred assertions
125 CostVec costs; ///< Disambiguating costs of recursive assertion satisfaction
126 ast::SymbolTable symtab; ///< Name lookup (depends on previous assertions)
127
128 /// Initial satisfaction state for a candidate
129 SatState( CandidateRef & c, const ast::SymbolTable & syms )
130 : cand( c ), need(), newNeed(), deferred(), inferred(), costs{ Cost::zero },
131 symtab( syms ) { need.swap( c->need ); }
132
133 /// Update satisfaction state for next step after previous state
134 SatState( SatState && o, IterateFlag )
135 : cand( std::move( o.cand ) ), need( o.newNeed.begin(), o.newNeed.end() ), newNeed(),
136 deferred(), inferred( std::move( o.inferred ) ), costs( std::move( o.costs ) ),
137 symtab( o.symtab ) { costs.emplace_back( Cost::zero ); }
138
139 /// Field-wise next step constructor
140 SatState(
141 CandidateRef && c, ast::AssertionSet && nn, InferCache && i, CostVec && cs,
142 ast::SymbolTable && syms )
143 : cand( std::move( c ) ), need( nn.begin(), nn.end() ), newNeed(), deferred(),
144 inferred( std::move( i ) ), costs( std::move( cs ) ), symtab( std::move( syms ) )
145 { costs.emplace_back( Cost::zero ); }
146 };
147
148 enum AssertionResult {Fail, Skip, Success} ;
149
150 /// Binds a single assertion, updating satisfaction state
151 void bindAssertion(
152 const ast::VariableExpr * expr, const ast::AssertionSetValue & info, CandidateRef & cand,
153 AssnCandidate & match, InferCache & inferred
154 ) {
155 const ast::DeclWithType * candidate = match.cdata.id;
156 assertf( candidate->uniqueId,
157 "Assertion candidate does not have a unique ID: %s", toString( candidate ).c_str() );
158
159 ast::Expr * varExpr = match.cdata.combine( cand->expr->location, cand->cost );
160 varExpr->result = match.adjType;
161 if ( match.resnSlot ) { varExpr->inferred.resnSlots().emplace_back( match.resnSlot ); }
162
163 // place newly-inferred assertion in proper location in cache
164 inferred[ info.resnSlot ][ expr->var->uniqueId ] = ast::ParamEntry{
165 candidate->uniqueId, candidate, match.adjType, expr->result, varExpr };
166 }
167
168 /// Satisfy a single assertion
169 AssertionResult satisfyAssertion( ast::AssertionList::value_type & assn, SatState & sat, bool skipUnbound = false) {
170 // skip unused assertions
171 // static unsigned int cnt = 0; // I think this was debugging code so I commented it
172 if ( ! assn.second.isUsed ) return AssertionResult::Success;
173
174 // if (assn.first->var->name[1] == '|') std::cerr << ++cnt << std::endl; // I think this was debugging code so I commented it
175
176 // find candidates that unify with the desired type
177 AssnCandidateList matches, inexactMatches;
178
179 std::vector<ast::SymbolTable::IdData> candidates;
180 auto kind = ast::SymbolTable::getSpecialFunctionKind(assn.first->var->name);
181 if (kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS) {
182 // prefilter special decls by argument type, if already known
183 ast::ptr<ast::Type> thisArgType = assn.first->result.strict_as<ast::PointerType>()->base
184 .strict_as<ast::FunctionType>()->params[0]
185 .strict_as<ast::ReferenceType>()->base;
186 // sat.cand->env.apply(thisArgType);
187
188 if (auto inst = thisArgType.as<ast::TypeInstType>()) {
189 auto cls = sat.cand->env.lookup(*inst);
190 if (cls && cls->bound) thisArgType = cls->bound;
191 }
192
193 std::string otypeKey = "";
194 if (thisArgType.as<ast::PointerType>()) otypeKey = Mangle::Encoding::pointer;
195 else if (!isUnboundType(thisArgType)) otypeKey = Mangle::mangle(thisArgType, Mangle::Type | Mangle::NoGenericParams);
196 else if (skipUnbound) return AssertionResult::Skip;
197
198 candidates = sat.symtab.specialLookupId(kind, otypeKey);
199 }
200 else {
201 candidates = sat.symtab.lookupId(assn.first->var->name);
202 }
203 for ( const ast::SymbolTable::IdData & cdata : candidates ) {
204 const ast::DeclWithType * candidate = cdata.id;
205
206 // ignore deleted candidates.
207 // NOTE: this behavior is different from main resolver.
208 // further investigations might be needed to determine
209 // if we should implement the same rule here
210 // (i.e. error if unique best match is deleted)
211 if (candidate->isDeleted && candidate->linkage == ast::Linkage::AutoGen) continue;
212
213 // build independent unification context for candidate
214 ast::AssertionSet have, newNeed;
215 ast::TypeEnvironment newEnv{ sat.cand->env };
216 ast::OpenVarSet newOpen{ sat.cand->open };
217 ast::ptr< ast::Type > toType = assn.first->result;
218 ast::ptr< ast::Type > adjType =
219 renameTyVars( adjustExprType( candidate->get_type(), newEnv, sat.symtab ), GEN_USAGE, false );
220
221 // only keep candidates which unify
222
223 ast::OpenVarSet closed;
224 // findOpenVars( toType, newOpen, closed, newNeed, have, FirstClosed );
225 findOpenVars( adjType, newOpen, closed, newNeed, have, newEnv, FirstOpen );
226 ast::TypeEnvironment tempNewEnv {newEnv};
227
228 if ( unifyExact( toType, adjType, tempNewEnv, newNeed, have, newOpen, WidenMode {true, true} ) ) {
229 // set up binding slot for recursive assertions
230 ast::UniqueId crntResnSlot = 0;
231 if ( ! newNeed.empty() ) {
232 crntResnSlot = ++globalResnSlot;
233 for ( auto & a : newNeed ) { a.second.resnSlot = crntResnSlot; }
234 }
235
236 matches.emplace_back(
237 cdata, adjType, std::move( tempNewEnv ), std::move( have ), std::move( newNeed ),
238 std::move( newOpen ), crntResnSlot );
239 }
240 else if ( matches.empty() ) {
241 // restore invalidated env
242 // newEnv = sat.cand->env;
243 // newNeed.clear();
244 if ( auto c = commonType( toType, adjType, newEnv, newNeed, have, newOpen, WidenMode {true, true} ) ) {
245 // set up binding slot for recursive assertions
246 ast::UniqueId crntResnSlot = 0;
247 if ( ! newNeed.empty() ) {
248 crntResnSlot = ++globalResnSlot;
249 for ( auto & a : newNeed ) { a.second.resnSlot = crntResnSlot; }
250 }
251
252 inexactMatches.emplace_back(
253 cdata, adjType, std::move( newEnv ), std::move( have ), std::move( newNeed ),
254 std::move( newOpen ), crntResnSlot );
255 }
256 }
257 }
258
259 // break if no satisfying match
260 if ( matches.empty() ) matches = std::move(inexactMatches);
261 if ( matches.empty() ) return AssertionResult::Fail;
262
263 // defer if too many satisfying matches
264 if ( matches.size() > 1 ) {
265 sat.deferred.emplace_back( assn.first, assn.second, std::move( matches ) );
266 return AssertionResult::Success;
267 }
268
269 // otherwise bind unique match in ongoing scope
270 AssnCandidate & match = matches.front();
271 // addToSymbolTable( match.have, sat.symtab );
272 sat.newNeed.insert( match.need.begin(), match.need.end() );
273 sat.cand->env = std::move( match.env );
274 sat.cand->open = std::move( match.open );
275
276 bindAssertion( assn.first, assn.second, sat.cand, match, sat.inferred );
277 return AssertionResult::Success;
278 }
279
280 /// Map of candidate return types to recursive assertion satisfaction costs
281 using PruneMap = std::unordered_map< std::string, CostVec >;
282
283 /// Gets the pruning key for a candidate (derived from environment-adjusted return type)
284 std::string pruneKey( const Candidate & cand ) {
285 ast::ptr< ast::Type > resType = cand.expr->result;
286 cand.env.apply( resType );
287 return Mangle::mangleType( resType );
288 }
289
290 /// Associates inferred parameters with an expression
291 struct InferMatcher final {
292 InferCache & inferred;
293
294 InferMatcher( InferCache & inferred ) : inferred( inferred ) {}
295
296 const ast::Expr * postvisit( const ast::Expr * expr ) {
297 // Skip if no slots to find
298 if ( !expr->inferred.hasSlots() ) return expr;
299 // if ( expr->inferred.mode != ast::Expr::InferUnion::Slots ) return expr;
300 std::vector<UniqueId> missingSlots;
301 // find inferred parameters for resolution slots
302 ast::InferredParams * newInferred = new ast::InferredParams();
303 for ( UniqueId slot : expr->inferred.resnSlots() ) {
304 // fail if no matching assertions found
305 auto it = inferred.find( slot );
306 if ( it == inferred.end() ) {
307 // std::cerr << "missing assertion " << slot << std::endl;
308 missingSlots.push_back(slot);
309 continue;
310 }
311
312 // place inferred parameters into new map
313 for ( auto & entry : it->second ) {
314 // recurse on inferParams of resolved expressions
315 entry.second.expr = postvisit( entry.second.expr );
316 auto res = newInferred->emplace( entry );
317 assert( res.second && "all assertions newly placed" );
318 }
319 }
320
321 ast::Expr * ret = mutate( expr );
322 ret->inferred.set_inferParams( newInferred );
323 if (!missingSlots.empty()) ret->inferred.resnSlots() = missingSlots;
324 return ret;
325 }
326 };
327
328 /// Replace ResnSlots with InferParams and add alternative to output list, if it meets pruning
329 /// threshold.
330 void finalizeAssertions(
331 CandidateRef & cand, InferCache & inferred, PruneMap & thresholds, CostVec && costs,
332 CandidateList & out
333 ) {
334 // prune if cheaper alternative for same key has already been generated
335 std::string key = pruneKey( *cand );
336 auto it = thresholds.find( key );
337 if ( it != thresholds.end() ) {
338 if ( it->second < costs ) return;
339 } else {
340 thresholds.emplace_hint( it, key, std::move( costs ) );
341 }
342
343 // replace resolution slots with inferred parameters, add to output
344 ast::Pass< InferMatcher > matcher{ inferred };
345 cand->expr = cand->expr->accept( matcher );
346 out.emplace_back( cand );
347 }
348
349 /// Combo iterator that combines candidates into an output list, merging their environments.
350 /// Rejects an appended candidate if environments cannot be merged. See `Common/FilterCombos.h`
351 /// for description of "combo iterator".
352 class CandidateEnvMerger {
353 /// Current list of merged candidates
354 std::vector< DeferRef > crnt;
355 /// Stack of environments to support backtracking
356 std::vector< ast::TypeEnvironment > envs;
357 /// Stack of open variables to support backtracking
358 std::vector< ast::OpenVarSet > opens;
359 /// Symbol table to use for merges
360 const ast::SymbolTable & symtab;
361
362 public:
363 /// The merged environment/open variables and the list of candidates
364 struct OutType {
365 ast::TypeEnvironment env;
366 ast::OpenVarSet open;
367 std::vector< DeferRef > assns;
368 Cost cost;
369
370 OutType(
371 const ast::TypeEnvironment & e, const ast::OpenVarSet & o,
372 const std::vector< DeferRef > & as, const ast::SymbolTable & symtab )
373 : env( e ), open( o ), assns( as ), cost( Cost::zero ) {
374 // compute combined conversion cost
375 for ( const DeferRef & assn : assns ) {
376 // compute conversion cost from satisfying decl to assertion
377 cost += computeConversionCost(
378 assn.match.adjType, assn.expr->result, false, symtab, env );
379
380 // mark vars+specialization on function-type assertions
381 const ast::FunctionType * func =
382 GenPoly::getFunctionType( assn.match.cdata.id->get_type() );
383 if ( ! func ) continue;
384
385 for ( const auto & param : func->params ) {
386 cost.decSpec( specCost( param ) );
387 }
388
389 cost.incVar( func->forall.size() );
390
391 cost.decSpec( func->assertions.size() );
392 }
393 }
394
395 bool operator< ( const OutType & o ) const { return cost < o.cost; }
396 };
397
398 CandidateEnvMerger(
399 const ast::TypeEnvironment & env, const ast::OpenVarSet & open,
400 const ast::SymbolTable & syms )
401 : crnt(), envs{ env }, opens{ open }, symtab( syms ) {}
402
403 bool append( DeferRef i ) {
404 ast::TypeEnvironment env = envs.back();
405 ast::OpenVarSet open = opens.back();
406 mergeOpenVars( open, i.match.open );
407
408 if ( ! env.combine( i.match.env, open ) ) return false;
409
410 crnt.emplace_back( i );
411 envs.emplace_back( std::move( env ) );
412 opens.emplace_back( std::move( open ) );
413 return true;
414 }
415
416 void backtrack() {
417 crnt.pop_back();
418 envs.pop_back();
419 opens.pop_back();
420 }
421
422 OutType finalize() { return { envs.back(), opens.back(), crnt, symtab }; }
423 };
424
425 /// Limit to depth of recursion of assertion satisfaction
426 static const int recursionLimit = 8;
427 /// Maximum number of simultaneously-deferred assertions to attempt concurrent satisfaction of
428 static const int deferLimit = 10;
429} // anonymous namespace
430
431void satisfyAssertions(
432 CandidateRef & cand, const ast::SymbolTable & symtab, CandidateList & out,
433 std::vector<std::string> & errors
434) {
435 // finish early if no assertions to satisfy
436 if ( cand->need.empty() ) {
437 out.emplace_back( cand );
438 return;
439 }
440
441 // build list of possible combinations of satisfying declarations
442 std::vector< SatState > sats{ SatState{ cand, symtab } };
443 std::vector< SatState > nextSats{};
444
445 // pruning thresholds by result type of output candidates.
446 // Candidates *should* be generated in sorted order, so no need to retroactively prune
447 PruneMap thresholds;
448
449 // satisfy assertions in breadth-first order over the recursion tree of assertion satisfaction.
450 // Stop recursion at a limited number of levels deep to avoid infinite loops.
451 for ( unsigned level = 0; level < recursionLimit; ++level ) {
452 // for each current mutually-compatible set of assertions
453 for ( SatState & sat : sats ) {
454 // stop this branch if a better option is already found
455 auto it = thresholds.find( pruneKey( *sat.cand ) );
456 if ( it != thresholds.end() && it->second < sat.costs ) goto nextSat;
457
458 // should a limit be imposed? worst case here is O(n^2) but very unlikely to happen.
459
460 for (unsigned resetCount = 0; ; ++resetCount) {
461 ast::AssertionList next;
462 // make initial pass at matching assertions
463 for ( auto & assn : sat.need ) {
464 resetTyVarRenaming();
465 // fail early if any assertion is not satisfiable
466 auto result = satisfyAssertion( assn, sat, !next.empty() );
467 if ( result == AssertionResult::Fail ) {
468 Indenter tabs{ 3 };
469 std::ostringstream ss;
470 ss << tabs << "Unsatisfiable alternative:\n";
471 print( ss, *sat.cand, ++tabs );
472 ss << (tabs-1) << "Could not satisfy assertion:\n";
473 ast::print( ss, assn.first, tabs );
474
475 errors.emplace_back( ss.str() );
476 goto nextSat;
477 }
478 else if ( result == AssertionResult::Skip ) {
479 next.emplace_back(assn);
480 // goto nextSat;
481 }
482 }
483 // success
484 if (next.empty()) break;
485
486 sat.need = std::move(next);
487 }
488
489 if ( sat.deferred.empty() ) {
490 // either add successful match or push back next state
491 if ( sat.newNeed.empty() ) {
492 finalizeAssertions(
493 sat.cand, sat.inferred, thresholds, std::move( sat.costs ), out );
494 } else {
495 nextSats.emplace_back( std::move( sat ), IterateState );
496 }
497 } else if ( sat.deferred.size() > deferLimit ) {
498 // too many deferred assertions to attempt mutual compatibility
499 Indenter tabs{ 3 };
500 std::ostringstream ss;
501 ss << tabs << "Unsatisfiable alternative:\n";
502 print( ss, *sat.cand, ++tabs );
503 ss << (tabs-1) << "Too many non-unique satisfying assignments for assertions:\n";
504 for ( const auto & d : sat.deferred ) {
505 ast::print( ss, d.expr, tabs );
506 }
507
508 errors.emplace_back( ss.str() );
509 goto nextSat;
510 } else {
511 // combine deferred assertions by mutual compatibility
512 std::vector< CandidateEnvMerger::OutType > compatible = filterCombos(
513 sat.deferred, CandidateEnvMerger{ sat.cand->env, sat.cand->open, sat.symtab } );
514
515 // fail early if no mutually-compatible assertion satisfaction
516 if ( compatible.empty() ) {
517 Indenter tabs{ 3 };
518 std::ostringstream ss;
519 ss << tabs << "Unsatisfiable alternative:\n";
520 print( ss, *sat.cand, ++tabs );
521 ss << (tabs-1) << "No mutually-compatible satisfaction for assertions:\n";
522 for ( const auto& d : sat.deferred ) {
523 ast::print( ss, d.expr, tabs );
524 }
525
526 errors.emplace_back( ss.str() );
527 goto nextSat;
528 }
529
530 // sort by cost (for overall pruning order)
531 std::sort( compatible.begin(), compatible.end() );
532
533 // process mutually-compatible combinations
534 for ( auto & compat : compatible ) {
535 // set up next satisfaction state
536 CandidateRef nextCand = std::make_shared<Candidate>(
537 sat.cand->expr, std::move( compat.env ), std::move( compat.open ),
538 ast::AssertionSet{} /* need moved into satisfaction state */,
539 sat.cand->cost );
540
541 ast::AssertionSet nextNewNeed{ sat.newNeed };
542 InferCache nextInferred{ sat.inferred };
543
544 CostVec nextCosts{ sat.costs };
545 nextCosts.back() += compat.cost;
546
547 ast::SymbolTable nextSymtab{ sat.symtab };
548
549 // add compatible assertions to new satisfaction state
550 for ( DeferRef r : compat.assns ) {
551 AssnCandidate match = r.match;
552 // addToSymbolTable( match.have, nextSymtab );
553 nextNewNeed.insert( match.need.begin(), match.need.end() );
554
555 bindAssertion( r.expr, r.info, nextCand, match, nextInferred );
556 }
557
558 // either add successful match or push back next state
559 if ( nextNewNeed.empty() ) {
560 finalizeAssertions(
561 nextCand, nextInferred, thresholds, std::move( nextCosts ), out );
562 } else {
563 nextSats.emplace_back(
564 std::move( nextCand ), std::move( nextNewNeed ),
565 std::move( nextInferred ), std::move( nextCosts ),
566 std::move( nextSymtab ) );
567 }
568 }
569 }
570 nextSat:; }
571
572 // finish or reset for next round
573 if ( nextSats.empty() ) return;
574 sats.swap( nextSats );
575 nextSats.clear();
576 }
577
578 // exceeded recursion limit if reaches here
579 if ( out.empty() ) {
580 SemanticError( cand->expr->location, "Too many recursive assertions" );
581 }
582}
583
584} // namespace ResolvExpr
585
586// Local Variables: //
587// tab-width: 4 //
588// mode: c++ //
589// compile-command: "make install" //
590// End: //
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