source: src/ResolvExpr/SatisfyAssertions.cpp@ 03c56f6

ADT ast-experimental
Last change on this file since 03c56f6 was 0026d67, checked in by Andrew Beach <ajbeach@…>, 3 years ago

Replaced Mangle::typeMode() with Mangle::mangleType(...), as it is how typeMode() was always used and it is shorter. Various other clean-up in the Mangler files.
  • Property mode set to 100644
File size: 20.3 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 <algorithm>
19#include <cassert>
20#include <sstream>
21#include <string>
22#include <unordered_map>
23#include <vector>
24
25#include "Candidate.hpp"
26#include "CandidateFinder.hpp"
27#include "Cost.h"
28#include "RenameVars.h"
29#include "typeops.h"
30#include "Unify.h"
31#include "AST/Decl.hpp"
32#include "AST/Expr.hpp"
33#include "AST/Node.hpp"
34#include "AST/Pass.hpp"
35#include "AST/Print.hpp"
36#include "AST/SymbolTable.hpp"
37#include "AST/TypeEnvironment.hpp"
38#include "FindOpenVars.h"
39#include "Common/FilterCombos.h"
40#include "Common/Indenter.h"
41#include "GenPoly/GenPoly.h"
42#include "SymTab/Mangler.h"
43
44namespace ResolvExpr {
45
46// in CandidateFinder.cpp; unique ID for assertion satisfaction
47extern UniqueId globalResnSlot;
48
49namespace {
50 /// Post-unification assertion satisfaction candidate
51 struct AssnCandidate {
52 ast::SymbolTable::IdData cdata; ///< Satisfying declaration
53 ast::ptr< ast::Type > adjType; ///< Satisfying type
54 ast::TypeEnvironment env; ///< Post-unification environment
55 ast::AssertionSet have; ///< Post-unification have-set
56 ast::AssertionSet need; ///< Post-unification need-set
57 ast::OpenVarSet open; ///< Post-unification open-var-set
58 ast::UniqueId resnSlot; ///< Slot for any recursive assertion IDs
59
60 AssnCandidate(
61 const ast::SymbolTable::IdData c, const ast::Type * at, ast::TypeEnvironment && e,
62 ast::AssertionSet && h, ast::AssertionSet && n, ast::OpenVarSet && o, ast::UniqueId rs )
63 : cdata( c ), adjType( at ), env( std::move( e ) ), have( std::move( h ) ),
64 need( std::move( n ) ), open( std::move( o ) ), resnSlot( rs ) {}
65 };
66
67 /// List of assertion satisfaction candidates
68 using AssnCandidateList = std::vector< AssnCandidate >;
69
70 /// Reference to a single deferred item
71 struct DeferRef {
72 const ast::VariableExpr * expr;
73 const ast::AssertionSetValue & info;
74 const AssnCandidate & match;
75 };
76
77 /// Wrapper for the deferred items from a single assertion satisfaction.
78 /// Acts like an indexed list of DeferRef
79 struct DeferItem {
80 const ast::VariableExpr * expr;
81 const ast::AssertionSetValue & info;
82 AssnCandidateList matches;
83
84 DeferItem(
85 const ast::VariableExpr * d, const ast::AssertionSetValue & i, AssnCandidateList && ms )
86 : expr( d ), info( i ), matches( std::move( ms ) ) {}
87
88 bool empty() const { return matches.empty(); }
89
90 AssnCandidateList::size_type size() const { return matches.size(); }
91
92 DeferRef operator[] ( unsigned i ) const { return { expr, info, matches[i] }; }
93 };
94
95 /// List of deferred satisfaction items
96 using DeferList = std::vector< DeferItem >;
97
98 /// Set of assertion satisfactions, grouped by resolution ID
99 using InferCache = std::unordered_map< ast::UniqueId, ast::InferredParams >;
100
101 /// Lexicographically-ordered vector of costs.
102 /// Lexicographic order comes from default operator< on std::vector.
103 using CostVec = std::vector< Cost >;
104
105 /// Flag for state iteration
106 enum IterateFlag { IterateState };
107
108 /// Intermediate state for satisfying a set of assertions
109 struct SatState {
110 CandidateRef cand; ///< Candidate assertion is rooted on
111 ast::AssertionList need; ///< Assertions to find
112 ast::AssertionSet newNeed; ///< Recursive assertions from current satisfied assertions
113 DeferList deferred; ///< Deferred matches
114 InferCache inferred; ///< Cache of already-inferred assertions
115 CostVec costs; ///< Disambiguating costs of recursive assertion satisfaction
116 ast::SymbolTable symtab; ///< Name lookup (depends on previous assertions)
117
118 /// Initial satisfaction state for a candidate
119 SatState( CandidateRef & c, const ast::SymbolTable & syms )
120 : cand( c ), need(), newNeed(), deferred(), inferred(), costs{ Cost::zero },
121 symtab( syms ) { need.swap( c->need ); }
122
123 /// Update satisfaction state for next step after previous state
124 SatState( SatState && o, IterateFlag )
125 : cand( std::move( o.cand ) ), need( o.newNeed.begin(), o.newNeed.end() ), newNeed(),
126 deferred(), inferred( std::move( o.inferred ) ), costs( std::move( o.costs ) ),
127 symtab( o.symtab ) { costs.emplace_back( Cost::zero ); }
128
129 /// Field-wise next step constructor
130 SatState(
131 CandidateRef && c, ast::AssertionSet && nn, InferCache && i, CostVec && cs,
132 ast::SymbolTable && syms )
133 : cand( std::move( c ) ), need( nn.begin(), nn.end() ), newNeed(), deferred(),
134 inferred( std::move( i ) ), costs( std::move( cs ) ), symtab( std::move( syms ) )
135 { costs.emplace_back( Cost::zero ); }
136 };
137
138 /// Adds a captured assertion to the symbol table
139 void addToSymbolTable( const ast::AssertionSet & have, ast::SymbolTable & symtab ) {
140 for ( auto & i : have ) {
141 if ( i.second.isUsed ) { symtab.addId( i.first->var ); }
142 }
143 }
144
145 /// Binds a single assertion, updating satisfaction state
146 void bindAssertion(
147 const ast::VariableExpr * expr, const ast::AssertionSetValue & info, CandidateRef & cand,
148 AssnCandidate & match, InferCache & inferred
149 ) {
150 const ast::DeclWithType * candidate = match.cdata.id;
151 assertf( candidate->uniqueId,
152 "Assertion candidate does not have a unique ID: %s", toString( candidate ).c_str() );
153
154 ast::Expr * varExpr = match.cdata.combine( cand->expr->location, cand->cvtCost );
155 varExpr->result = match.adjType;
156 if ( match.resnSlot ) { varExpr->inferred.resnSlots().emplace_back( match.resnSlot ); }
157
158 // place newly-inferred assertion in proper location in cache
159 inferred[ info.resnSlot ][ expr->var->uniqueId ] = ast::ParamEntry{
160 candidate->uniqueId, candidate, match.adjType, expr->result, varExpr };
161 }
162
163 /// Satisfy a single assertion
164 bool satisfyAssertion( ast::AssertionList::value_type & assn, SatState & sat, bool allowConversion = false, bool skipUnbound = false) {
165 // skip unused assertions
166 if ( ! assn.second.isUsed ) return true;
167
168 // find candidates that unify with the desired type
169 AssnCandidateList matches;
170
171 std::vector<ast::SymbolTable::IdData> candidates;
172 auto kind = ast::SymbolTable::getSpecialFunctionKind(assn.first->var->name);
173 if (kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS) {
174 // prefilter special decls by argument type, if already known
175 ast::ptr<ast::Type> thisArgType = assn.first->result.strict_as<ast::PointerType>()->base
176 .strict_as<ast::FunctionType>()->params[0]
177 .strict_as<ast::ReferenceType>()->base;
178 sat.cand->env.apply(thisArgType);
179
180 std::string otypeKey = "";
181 if (thisArgType.as<ast::PointerType>()) otypeKey = Mangle::Encoding::pointer;
182 else if (!isUnboundType(thisArgType)) otypeKey = Mangle::mangle(thisArgType, Mangle::Type | Mangle::NoGenericParams);
183 else if (skipUnbound) return false;
184
185 candidates = sat.symtab.specialLookupId(kind, otypeKey);
186 }
187 else {
188 candidates = sat.symtab.lookupId(assn.first->var->name);
189 }
190 for ( const ast::SymbolTable::IdData & cdata : candidates ) {
191 const ast::DeclWithType * candidate = cdata.id;
192
193 // ignore deleted candidates.
194 // NOTE: this behavior is different from main resolver.
195 // further investigations might be needed to determine
196 // if we should implement the same rule here
197 // (i.e. error if unique best match is deleted)
198 if (candidate->isDeleted && candidate->linkage == ast::Linkage::AutoGen) continue;
199
200 // build independent unification context for candidate
201 ast::AssertionSet have, newNeed;
202 ast::TypeEnvironment newEnv{ sat.cand->env };
203 ast::OpenVarSet newOpen{ sat.cand->open };
204 ast::ptr< ast::Type > toType = assn.first->result;
205 ast::ptr< ast::Type > adjType =
206 renameTyVars( adjustExprType( candidate->get_type(), newEnv, sat.symtab ), GEN_USAGE, false );
207
208 // only keep candidates which unify
209
210 ast::OpenVarSet closed;
211 findOpenVars( toType, newOpen, closed, newNeed, have, FirstClosed );
212 findOpenVars( adjType, newOpen, closed, newNeed, have, FirstOpen );
213 if ( allowConversion ) {
214 if ( auto c = commonType( toType, adjType, newEnv, newNeed, have, newOpen, WidenMode {true, true}, sat.symtab ) ) {
215 // set up binding slot for recursive assertions
216 ast::UniqueId crntResnSlot = 0;
217 if ( ! newNeed.empty() ) {
218 crntResnSlot = ++globalResnSlot;
219 for ( auto & a : newNeed ) { a.second.resnSlot = crntResnSlot; }
220 }
221
222 matches.emplace_back(
223 cdata, adjType, std::move( newEnv ), std::move( have ), std::move( newNeed ),
224 std::move( newOpen ), crntResnSlot );
225 }
226 }
227 else {
228 if ( unifyExact( toType, adjType, newEnv, newNeed, have, newOpen, WidenMode {true, true}, sat.symtab ) ) {
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( newEnv ), std::move( have ), std::move( newNeed ),
238 std::move( newOpen ), crntResnSlot );
239 }
240 }
241 }
242
243 // break if no satisfying match
244 if ( matches.empty() ) return false;
245
246 // defer if too many satisfying matches
247 if ( matches.size() > 1 ) {
248 sat.deferred.emplace_back( assn.first, assn.second, std::move( matches ) );
249 return true;
250 }
251
252 // otherwise bind unique match in ongoing scope
253 AssnCandidate & match = matches.front();
254 addToSymbolTable( match.have, sat.symtab );
255 sat.newNeed.insert( match.need.begin(), match.need.end() );
256 sat.cand->env = std::move( match.env );
257 sat.cand->open = std::move( match.open );
258
259 bindAssertion( assn.first, assn.second, sat.cand, match, sat.inferred );
260 return true;
261 }
262
263 /// Map of candidate return types to recursive assertion satisfaction costs
264 using PruneMap = std::unordered_map< std::string, CostVec >;
265
266 /// Gets the pruning key for a candidate (derived from environment-adjusted return type)
267 std::string pruneKey( const Candidate & cand ) {
268 ast::ptr< ast::Type > resType = cand.expr->result;
269 cand.env.apply( resType );
270 return Mangle::mangleType( resType );
271 }
272
273 /// Associates inferred parameters with an expression
274 struct InferMatcher final {
275 InferCache & inferred;
276
277 InferMatcher( InferCache & inferred ) : inferred( inferred ) {}
278
279 const ast::Expr * postvisit( const ast::Expr * expr ) {
280 // Skip if no slots to find
281 if ( !expr->inferred.hasSlots() ) return expr;
282 // if ( expr->inferred.mode != ast::Expr::InferUnion::Slots ) return expr;
283 std::vector<UniqueId> missingSlots;
284 // find inferred parameters for resolution slots
285 ast::InferredParams * newInferred = new ast::InferredParams();
286 for ( UniqueId slot : expr->inferred.resnSlots() ) {
287 // fail if no matching assertions found
288 auto it = inferred.find( slot );
289 if ( it == inferred.end() ) {
290 // std::cerr << "missing assertion " << slot << std::endl;
291 missingSlots.push_back(slot);
292 continue;
293 }
294
295 // place inferred parameters into new map
296 for ( auto & entry : it->second ) {
297 // recurse on inferParams of resolved expressions
298 entry.second.expr = postvisit( entry.second.expr );
299 auto res = newInferred->emplace( entry );
300 assert( res.second && "all assertions newly placed" );
301 }
302 }
303
304 ast::Expr * ret = mutate( expr );
305 ret->inferred.set_inferParams( newInferred );
306 if (!missingSlots.empty()) ret->inferred.resnSlots() = missingSlots;
307 return ret;
308 }
309 };
310
311 /// Replace ResnSlots with InferParams and add alternative to output list, if it meets pruning
312 /// threshold.
313 void finalizeAssertions(
314 CandidateRef & cand, InferCache & inferred, PruneMap & thresholds, CostVec && costs,
315 CandidateList & out
316 ) {
317 // prune if cheaper alternative for same key has already been generated
318 std::string key = pruneKey( *cand );
319 auto it = thresholds.find( key );
320 if ( it != thresholds.end() ) {
321 if ( it->second < costs ) return;
322 } else {
323 thresholds.emplace_hint( it, key, std::move( costs ) );
324 }
325
326 // replace resolution slots with inferred parameters, add to output
327 ast::Pass< InferMatcher > matcher{ inferred };
328 cand->expr = cand->expr->accept( matcher );
329 out.emplace_back( cand );
330 }
331
332 /// Combo iterator that combines candidates into an output list, merging their environments.
333 /// Rejects an appended candidate if environments cannot be merged. See `Common/FilterCombos.h`
334 /// for description of "combo iterator".
335 class CandidateEnvMerger {
336 /// Current list of merged candidates
337 std::vector< DeferRef > crnt;
338 /// Stack of environments to support backtracking
339 std::vector< ast::TypeEnvironment > envs;
340 /// Stack of open variables to support backtracking
341 std::vector< ast::OpenVarSet > opens;
342 /// Symbol table to use for merges
343 const ast::SymbolTable & symtab;
344
345 public:
346 /// The merged environment/open variables and the list of candidates
347 struct OutType {
348 ast::TypeEnvironment env;
349 ast::OpenVarSet open;
350 std::vector< DeferRef > assns;
351 Cost cost;
352
353 OutType(
354 const ast::TypeEnvironment & e, const ast::OpenVarSet & o,
355 const std::vector< DeferRef > & as, const ast::SymbolTable & symtab )
356 : env( e ), open( o ), assns( as ), cost( Cost::zero ) {
357 // compute combined conversion cost
358 for ( const DeferRef & assn : assns ) {
359 // compute conversion cost from satisfying decl to assertion
360 cost += computeConversionCost(
361 assn.match.adjType, assn.expr->result, false, symtab, env );
362
363 // mark vars+specialization on function-type assertions
364 const ast::FunctionType * func =
365 GenPoly::getFunctionType( assn.match.cdata.id->get_type() );
366 if ( ! func ) continue;
367
368 for ( const auto & param : func->params ) {
369 cost.decSpec( specCost( param ) );
370 }
371
372 cost.incVar( func->forall.size() );
373
374 cost.decSpec( func->assertions.size() );
375 }
376 }
377
378 bool operator< ( const OutType & o ) const { return cost < o.cost; }
379 };
380
381 CandidateEnvMerger(
382 const ast::TypeEnvironment & env, const ast::OpenVarSet & open,
383 const ast::SymbolTable & syms )
384 : crnt(), envs{ env }, opens{ open }, symtab( syms ) {}
385
386 bool append( DeferRef i ) {
387 ast::TypeEnvironment env = envs.back();
388 ast::OpenVarSet open = opens.back();
389 mergeOpenVars( open, i.match.open );
390
391 if ( ! env.combine( i.match.env, open, symtab ) ) return false;
392
393 crnt.emplace_back( i );
394 envs.emplace_back( std::move( env ) );
395 opens.emplace_back( std::move( open ) );
396 return true;
397 }
398
399 void backtrack() {
400 crnt.pop_back();
401 envs.pop_back();
402 opens.pop_back();
403 }
404
405 OutType finalize() { return { envs.back(), opens.back(), crnt, symtab }; }
406 };
407
408 /// Limit to depth of recursion of assertion satisfaction
409 static const int recursionLimit = 8;
410 /// Maximum number of simultaneously-deferred assertions to attempt concurrent satisfaction of
411 static const int deferLimit = 10;
412} // anonymous namespace
413
414void satisfyAssertions(
415 CandidateRef & cand, const ast::SymbolTable & symtab, CandidateList & out,
416 std::vector<std::string> & errors
417) {
418 // finish early if no assertions to satisfy
419 if ( cand->need.empty() ) {
420 out.emplace_back( cand );
421 return;
422 }
423
424 // build list of possible combinations of satisfying declarations
425 std::vector< SatState > sats{ SatState{ cand, symtab } };
426 std::vector< SatState > nextSats{};
427
428 // pruning thresholds by result type of output candidates.
429 // Candidates *should* be generated in sorted order, so no need to retroactively prune
430 PruneMap thresholds;
431
432 // satisfy assertions in breadth-first order over the recursion tree of assertion satisfaction.
433 // Stop recursion at a limited number of levels deep to avoid infinite loops.
434 for ( unsigned level = 0; level < recursionLimit; ++level ) {
435 // for each current mutually-compatible set of assertions
436 for ( SatState & sat : sats ) {
437 bool allowConversion = false;
438 // stop this branch if a better option is already found
439 auto it = thresholds.find( pruneKey( *sat.cand ) );
440 if ( it != thresholds.end() && it->second < sat.costs ) goto nextSat;
441
442 // should a limit be imposed? worst case here is O(n^2) but very unlikely to happen.
443
444 for (unsigned resetCount = 0; ; ++resetCount) {
445 ast::AssertionList next;
446 resetTyVarRenaming();
447 // make initial pass at matching assertions
448 for ( auto & assn : sat.need ) {
449 // fail early if any assertion is not satisfiable
450 if ( ! satisfyAssertion( assn, sat, allowConversion, !next.empty() ) ) {
451 next.emplace_back(assn);
452 // goto nextSat;
453 }
454 }
455 // success
456 if (next.empty()) break;
457 // fail if nothing resolves
458 else if (next.size() == sat.need.size()) {
459 if (allowConversion) {
460 Indenter tabs{ 3 };
461 std::ostringstream ss;
462 ss << tabs << "Unsatisfiable alternative:\n";
463 print( ss, *sat.cand, ++tabs );
464 ss << (tabs-1) << "Could not satisfy assertion:\n";
465 ast::print( ss, next[0].first, tabs );
466
467 errors.emplace_back( ss.str() );
468 goto nextSat;
469 }
470
471 else {
472 allowConversion = true;
473 continue;
474 }
475 }
476 allowConversion = false;
477 sat.need = std::move(next);
478 }
479
480 if ( sat.deferred.empty() ) {
481 // either add successful match or push back next state
482 if ( sat.newNeed.empty() ) {
483 finalizeAssertions(
484 sat.cand, sat.inferred, thresholds, std::move( sat.costs ), out );
485 } else {
486 nextSats.emplace_back( std::move( sat ), IterateState );
487 }
488 } else if ( sat.deferred.size() > deferLimit ) {
489 // too many deferred assertions to attempt mutual compatibility
490 Indenter tabs{ 3 };
491 std::ostringstream ss;
492 ss << tabs << "Unsatisfiable alternative:\n";
493 print( ss, *sat.cand, ++tabs );
494 ss << (tabs-1) << "Too many non-unique satisfying assignments for assertions:\n";
495 for ( const auto & d : sat.deferred ) {
496 ast::print( ss, d.expr, tabs );
497 }
498
499 errors.emplace_back( ss.str() );
500 goto nextSat;
501 } else {
502 // combine deferred assertions by mutual compatibility
503 std::vector< CandidateEnvMerger::OutType > compatible = filterCombos(
504 sat.deferred, CandidateEnvMerger{ sat.cand->env, sat.cand->open, sat.symtab } );
505
506 // fail early if no mutually-compatible assertion satisfaction
507 if ( compatible.empty() ) {
508 Indenter tabs{ 3 };
509 std::ostringstream ss;
510 ss << tabs << "Unsatisfiable alternative:\n";
511 print( ss, *sat.cand, ++tabs );
512 ss << (tabs-1) << "No mutually-compatible satisfaction for assertions:\n";
513 for ( const auto& d : sat.deferred ) {
514 ast::print( ss, d.expr, tabs );
515 }
516
517 errors.emplace_back( ss.str() );
518 goto nextSat;
519 }
520
521 // sort by cost (for overall pruning order)
522 std::sort( compatible.begin(), compatible.end() );
523
524 // process mutually-compatible combinations
525 for ( auto & compat : compatible ) {
526 // set up next satisfaction state
527 CandidateRef nextCand = std::make_shared<Candidate>(
528 sat.cand->expr, std::move( compat.env ), std::move( compat.open ),
529 ast::AssertionSet{} /* need moved into satisfaction state */,
530 sat.cand->cost, sat.cand->cvtCost );
531
532 ast::AssertionSet nextNewNeed{ sat.newNeed };
533 InferCache nextInferred{ sat.inferred };
534
535 CostVec nextCosts{ sat.costs };
536 nextCosts.back() += compat.cost;
537
538 ast::SymbolTable nextSymtab{ sat.symtab };
539
540 // add compatible assertions to new satisfaction state
541 for ( DeferRef r : compat.assns ) {
542 AssnCandidate match = r.match;
543 addToSymbolTable( match.have, nextSymtab );
544 nextNewNeed.insert( match.need.begin(), match.need.end() );
545
546 bindAssertion( r.expr, r.info, nextCand, match, nextInferred );
547 }
548
549 // either add successful match or push back next state
550 if ( nextNewNeed.empty() ) {
551 finalizeAssertions(
552 nextCand, nextInferred, thresholds, std::move( nextCosts ), out );
553 } else {
554 nextSats.emplace_back(
555 std::move( nextCand ), std::move( nextNewNeed ),
556 std::move( nextInferred ), std::move( nextCosts ),
557 std::move( nextSymtab ) );
558 }
559 }
560 }
561 nextSat:; }
562
563 // finish or reset for next round
564 if ( nextSats.empty() ) return;
565 sats.swap( nextSats );
566 nextSats.clear();
567 }
568
569 // exceeded recursion limit if reaches here
570 if ( out.empty() ) {
571 SemanticError( cand->expr->location, "Too many recursive assertions" );
572 }
573}
574
575} // namespace ResolvExpr
576
577// Local Variables: //
578// tab-width: 4 //
579// mode: c++ //
580// compile-command: "make install" //
581// End: //
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