source: src/ResolvExpr/SatisfyAssertions.cpp@ 5936244

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 5936244 was e5c3811, checked in by Fangren Yu <f37yu@…>, 5 years ago

create dedicated symbol tables for big 3 operators
note: arbitrary this param type is not supported; it is currently allowed although never used
  • Property mode set to 100644
File size: 18.8 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 <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 "Common/FilterCombos.h"
39#include "Common/Indenter.h"
40#include "GenPoly/GenPoly.h"
41#include "SymTab/Mangler.h"
42
43namespace ResolvExpr {
44
45// in CandidateFinder.cpp; unique ID for assertion satisfaction
46extern UniqueId globalResnSlot;
47
48namespace {
49 /// Post-unification assertion satisfaction candidate
50 struct AssnCandidate {
51 ast::SymbolTable::IdData cdata; ///< Satisfying declaration
52 ast::ptr< ast::Type > adjType; ///< Satisfying type
53 ast::TypeEnvironment env; ///< Post-unification environment
54 ast::AssertionSet have; ///< Post-unification have-set
55 ast::AssertionSet need; ///< Post-unification need-set
56 ast::OpenVarSet open; ///< Post-unification open-var-set
57 ast::UniqueId resnSlot; ///< Slot for any recursive assertion IDs
58
59 AssnCandidate(
60 const ast::SymbolTable::IdData c, const ast::Type * at, ast::TypeEnvironment && e,
61 ast::AssertionSet && h, ast::AssertionSet && n, ast::OpenVarSet && o, ast::UniqueId rs )
62 : cdata( c ), adjType( at ), env( std::move( e ) ), have( std::move( h ) ),
63 need( std::move( n ) ), open( std::move( o ) ), resnSlot( rs ) {}
64 };
65
66 /// List of assertion satisfaction candidates
67 using AssnCandidateList = std::vector< AssnCandidate >;
68
69 /// Reference to a single deferred item
70 struct DeferRef {
71 const ast::DeclWithType * decl;
72 const ast::AssertionSetValue & info;
73 const AssnCandidate & match;
74 };
75
76 /// Wrapper for the deferred items from a single assertion satisfaction.
77 /// Acts like an indexed list of DeferRef
78 struct DeferItem {
79 const ast::DeclWithType * decl;
80 const ast::AssertionSetValue & info;
81 AssnCandidateList matches;
82
83 DeferItem(
84 const ast::DeclWithType * d, const ast::AssertionSetValue & i, AssnCandidateList && ms )
85 : decl( d ), info( i ), matches( std::move( ms ) ) {}
86
87 bool empty() const { return matches.empty(); }
88
89 AssnCandidateList::size_type size() const { return matches.size(); }
90
91 DeferRef operator[] ( unsigned i ) const { return { decl, info, matches[i] }; }
92 };
93
94 /// List of deferred satisfaction items
95 using DeferList = std::vector< DeferItem >;
96
97 /// Set of assertion satisfactions, grouped by resolution ID
98 using InferCache = std::unordered_map< ast::UniqueId, ast::InferredParams >;
99
100 /// Lexicographically-ordered vector of costs.
101 /// Lexicographic order comes from default operator< on std::vector.
102 using CostVec = std::vector< Cost >;
103
104 /// Flag for state iteration
105 enum IterateFlag { IterateState };
106
107 /// Intermediate state for satisfying a set of assertions
108 struct SatState {
109 CandidateRef cand; ///< Candidate assertion is rooted on
110 ast::AssertionList need; ///< Assertions to find
111 ast::AssertionSet newNeed; ///< Recursive assertions from current satisfied assertions
112 DeferList deferred; ///< Deferred matches
113 InferCache inferred; ///< Cache of already-inferred assertions
114 CostVec costs; ///< Disambiguating costs of recursive assertion satisfaction
115 ast::SymbolTable symtab; ///< Name lookup (depends on previous assertions)
116
117 /// Initial satisfaction state for a candidate
118 SatState( CandidateRef & c, const ast::SymbolTable & syms )
119 : cand( c ), need(), newNeed(), deferred(), inferred(), costs{ Cost::zero },
120 symtab( syms ) { need.swap( c->need ); }
121
122 /// Update satisfaction state for next step after previous state
123 SatState( SatState && o, IterateFlag )
124 : cand( std::move( o.cand ) ), need( o.newNeed.begin(), o.newNeed.end() ), newNeed(),
125 deferred(), inferred( std::move( o.inferred ) ), costs( std::move( o.costs ) ),
126 symtab( o.symtab ) { costs.emplace_back( Cost::zero ); }
127
128 /// Field-wise next step constructor
129 SatState(
130 CandidateRef && c, ast::AssertionSet && nn, InferCache && i, CostVec && cs,
131 ast::SymbolTable && syms )
132 : cand( std::move( c ) ), need( nn.begin(), nn.end() ), newNeed(), deferred(),
133 inferred( std::move( i ) ), costs( std::move( cs ) ), symtab( std::move( syms ) )
134 { costs.emplace_back( Cost::zero ); }
135 };
136
137 /// Adds a captured assertion to the symbol table
138 void addToSymbolTable( const ast::AssertionSet & have, ast::SymbolTable & symtab ) {
139 for ( auto & i : have ) {
140 if ( i.second.isUsed ) { symtab.addId( i.first ); }
141 }
142 }
143
144 /// Binds a single assertion, updating satisfaction state
145 void bindAssertion(
146 const ast::DeclWithType * decl, const ast::AssertionSetValue & info, CandidateRef & cand,
147 AssnCandidate & match, InferCache & inferred
148 ) {
149 const ast::DeclWithType * candidate = match.cdata.id;
150 assertf( candidate->uniqueId,
151 "Assertion candidate does not have a unique ID: %s", toString( candidate ).c_str() );
152
153 ast::Expr * varExpr = match.cdata.combine( cand->expr->location, cand->cvtCost );
154 varExpr->result = match.adjType;
155 if ( match.resnSlot ) { varExpr->inferred.resnSlots().emplace_back( match.resnSlot ); }
156
157 // place newly-inferred assertion in proper location in cache
158 inferred[ info.resnSlot ][ decl->uniqueId ] = ast::ParamEntry{
159 candidate->uniqueId, candidate, match.adjType, decl->get_type(), varExpr };
160 }
161
162 /// Satisfy a single assertion
163 bool satisfyAssertion( ast::AssertionList::value_type & assn, SatState & sat ) {
164 // skip unused assertions
165 if ( ! assn.second.isUsed ) return true;
166
167 // find candidates that unify with the desired type
168 AssnCandidateList matches;
169
170 std::vector<ast::SymbolTable::IdData> candidates;
171 auto kind = ast::SymbolTable::getSpecialFunctionKind(assn.first->name);
172 if (kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS) {
173 // prefilter special decls by argument type, if already known
174 ast::ptr<ast::Type> thisArgType = strict_dynamic_cast<const ast::PointerType *>(assn.first->get_type())->base
175 .strict_as<ast::FunctionType>()->params[0]
176 .strict_as<ast::ReferenceType>()->base;
177 sat.cand->env.apply(thisArgType);
178
179 std::string otypeKey = "";
180 if (thisArgType.as<ast::PointerType>()) otypeKey = Mangle::Encoding::pointer;
181 else if (!isUnboundType(thisArgType)) otypeKey = Mangle::mangle(thisArgType, Mangle::Type | Mangle::NoGenericParams);
182
183 candidates = sat.symtab.specialLookupId(kind, otypeKey);
184 }
185 else {
186 candidates = sat.symtab.lookupId(assn.first->name);
187 }
188 for ( const ast::SymbolTable::IdData & cdata : candidates ) {
189 const ast::DeclWithType * candidate = cdata.id;
190
191 // ignore deleted candidates.
192 // NOTE: this behavior is different from main resolver.
193 // further investigations might be needed to determine
194 // if we should implement the same rule here
195 // (i.e. error if unique best match is deleted)
196 if (candidate->isDeleted) continue;
197
198 // build independent unification context for candidate
199 ast::AssertionSet have, newNeed;
200 ast::TypeEnvironment newEnv{ sat.cand->env };
201 ast::OpenVarSet newOpen{ sat.cand->open };
202 ast::ptr< ast::Type > toType = assn.first->get_type();
203 ast::ptr< ast::Type > adjType =
204 renameTyVars( adjustExprType( candidate->get_type(), newEnv, sat.symtab ) );
205
206 // only keep candidates which unify
207 if ( unify( toType, adjType, newEnv, newNeed, have, newOpen, sat.symtab ) ) {
208 // set up binding slot for recursive assertions
209 ast::UniqueId crntResnSlot = 0;
210 if ( ! newNeed.empty() ) {
211 crntResnSlot = ++globalResnSlot;
212 for ( auto & a : newNeed ) { a.second.resnSlot = crntResnSlot; }
213 }
214
215 matches.emplace_back(
216 cdata, adjType, std::move( newEnv ), std::move( have ), std::move( newNeed ),
217 std::move( newOpen ), crntResnSlot );
218 }
219 }
220
221 // break if no satisfying match
222 if ( matches.empty() ) return false;
223
224 // defer if too many satisfying matches
225 if ( matches.size() > 1 ) {
226 sat.deferred.emplace_back( assn.first, assn.second, std::move( matches ) );
227 return true;
228 }
229
230 // otherwise bind unique match in ongoing scope
231 AssnCandidate & match = matches.front();
232 addToSymbolTable( match.have, sat.symtab );
233 sat.newNeed.insert( match.need.begin(), match.need.end() );
234 sat.cand->env = std::move( match.env );
235 sat.cand->open = std::move( match.open );
236
237 bindAssertion( assn.first, assn.second, sat.cand, match, sat.inferred );
238 return true;
239 }
240
241 /// Map of candidate return types to recursive assertion satisfaction costs
242 using PruneMap = std::unordered_map< std::string, CostVec >;
243
244 /// Gets the pruning key for a candidate (derived from environment-adjusted return type)
245 std::string pruneKey( const Candidate & cand ) {
246 ast::ptr< ast::Type > resType = cand.expr->result;
247 cand.env.apply( resType );
248 return Mangle::mangle( resType, Mangle::typeMode() );
249 }
250
251 /// Associates inferred parameters with an expression
252 struct InferMatcher final {
253 InferCache & inferred;
254
255 InferMatcher( InferCache & inferred ) : inferred( inferred ) {}
256
257 const ast::Expr * postvisit( const ast::Expr * expr ) {
258 // Skip if no slots to find
259 if ( !expr->inferred.hasSlots() ) return expr;
260 // if ( expr->inferred.mode != ast::Expr::InferUnion::Slots ) return expr;
261 std::vector<UniqueId> missingSlots;
262 // find inferred parameters for resolution slots
263 ast::InferredParams * newInferred = new ast::InferredParams();
264 for ( UniqueId slot : expr->inferred.resnSlots() ) {
265 // fail if no matching assertions found
266 auto it = inferred.find( slot );
267 if ( it == inferred.end() ) {
268 // std::cerr << "missing assertion " << slot << std::endl;
269 missingSlots.push_back(slot);
270 continue;
271 }
272
273 // place inferred parameters into new map
274 for ( auto & entry : it->second ) {
275 // recurse on inferParams of resolved expressions
276 entry.second.expr = postvisit( entry.second.expr );
277 auto res = newInferred->emplace( entry );
278 assert( res.second && "all assertions newly placed" );
279 }
280 }
281
282 ast::Expr * ret = mutate( expr );
283 ret->inferred.set_inferParams( newInferred );
284 if (!missingSlots.empty()) ret->inferred.resnSlots() = missingSlots;
285 return ret;
286 }
287 };
288
289 /// Replace ResnSlots with InferParams and add alternative to output list, if it meets pruning
290 /// threshold.
291 void finalizeAssertions(
292 CandidateRef & cand, InferCache & inferred, PruneMap & thresholds, CostVec && costs,
293 CandidateList & out
294 ) {
295 // prune if cheaper alternative for same key has already been generated
296 std::string key = pruneKey( *cand );
297 auto it = thresholds.find( key );
298 if ( it != thresholds.end() ) {
299 if ( it->second < costs ) return;
300 } else {
301 thresholds.emplace_hint( it, key, std::move( costs ) );
302 }
303
304 // replace resolution slots with inferred parameters, add to output
305 ast::Pass< InferMatcher > matcher{ inferred };
306 cand->expr = cand->expr->accept( matcher );
307 out.emplace_back( cand );
308 }
309
310 /// Combo iterator that combines candidates into an output list, merging their environments.
311 /// Rejects an appended candidate if environments cannot be merged. See `Common/FilterCombos.h`
312 /// for description of "combo iterator".
313 class CandidateEnvMerger {
314 /// Current list of merged candidates
315 std::vector< DeferRef > crnt;
316 /// Stack of environments to support backtracking
317 std::vector< ast::TypeEnvironment > envs;
318 /// Stack of open variables to support backtracking
319 std::vector< ast::OpenVarSet > opens;
320 /// Symbol table to use for merges
321 const ast::SymbolTable & symtab;
322
323 public:
324 /// The merged environment/open variables and the list of candidates
325 struct OutType {
326 ast::TypeEnvironment env;
327 ast::OpenVarSet open;
328 std::vector< DeferRef > assns;
329 Cost cost;
330
331 OutType(
332 const ast::TypeEnvironment & e, const ast::OpenVarSet & o,
333 const std::vector< DeferRef > & as, const ast::SymbolTable & symtab )
334 : env( e ), open( o ), assns( as ), cost( Cost::zero ) {
335 // compute combined conversion cost
336 for ( const DeferRef & assn : assns ) {
337 // compute conversion cost from satisfying decl to assertion
338 cost += computeConversionCost(
339 assn.match.adjType, assn.decl->get_type(), false, symtab, env );
340
341 // mark vars+specialization on function-type assertions
342 const ast::FunctionType * func =
343 GenPoly::getFunctionType( assn.match.cdata.id->get_type() );
344 if ( ! func ) continue;
345
346 for ( const auto & param : func->params ) {
347 cost.decSpec( specCost( param ) );
348 }
349
350 cost.incVar( func->forall.size() );
351
352 for ( const ast::TypeDecl * td : func->forall ) {
353 cost.decSpec( td->assertions.size() );
354 }
355 }
356 }
357
358 bool operator< ( const OutType & o ) const { return cost < o.cost; }
359 };
360
361 CandidateEnvMerger(
362 const ast::TypeEnvironment & env, const ast::OpenVarSet & open,
363 const ast::SymbolTable & syms )
364 : crnt(), envs{ env }, opens{ open }, symtab( syms ) {}
365
366 bool append( DeferRef i ) {
367 ast::TypeEnvironment env = envs.back();
368 ast::OpenVarSet open = opens.back();
369 mergeOpenVars( open, i.match.open );
370
371 if ( ! env.combine( i.match.env, open, symtab ) ) return false;
372
373 crnt.emplace_back( i );
374 envs.emplace_back( std::move( env ) );
375 opens.emplace_back( std::move( open ) );
376 return true;
377 }
378
379 void backtrack() {
380 crnt.pop_back();
381 envs.pop_back();
382 opens.pop_back();
383 }
384
385 OutType finalize() { return { envs.back(), opens.back(), crnt, symtab }; }
386 };
387
388 /// Limit to depth of recursion of assertion satisfaction
389 static const int recursionLimit = 4;
390 /// Maximum number of simultaneously-deferred assertions to attempt concurrent satisfaction of
391 static const int deferLimit = 10;
392} // anonymous namespace
393
394void satisfyAssertions(
395 CandidateRef & cand, const ast::SymbolTable & symtab, CandidateList & out,
396 std::vector<std::string> & errors
397) {
398 // finish early if no assertions to satisfy
399 if ( cand->need.empty() ) {
400 out.emplace_back( cand );
401 return;
402 }
403
404 // build list of possible combinations of satisfying declarations
405 std::vector< SatState > sats{ SatState{ cand, symtab } };
406 std::vector< SatState > nextSats{};
407
408 // pruning thresholds by result type of output candidates.
409 // Candidates *should* be generated in sorted order, so no need to retroactively prune
410 PruneMap thresholds;
411
412 // satisfy assertions in breadth-first order over the recursion tree of assertion satisfaction.
413 // Stop recursion at a limited number of levels deep to avoid infinite loops.
414 for ( unsigned level = 0; level < recursionLimit; ++level ) {
415 // for each current mutually-compatible set of assertions
416 for ( SatState & sat : sats ) {
417 // stop this branch if a better option is already found
418 auto it = thresholds.find( pruneKey( *sat.cand ) );
419 if ( it != thresholds.end() && it->second < sat.costs ) goto nextSat;
420
421 // make initial pass at matching assertions
422 for ( auto & assn : sat.need ) {
423 // fail early if any assertion is not satisfiable
424 if ( ! satisfyAssertion( assn, sat ) ) {
425 Indenter tabs{ 3 };
426 std::ostringstream ss;
427 ss << tabs << "Unsatisfiable alternative:\n";
428 print( ss, *sat.cand, ++tabs );
429 ss << (tabs-1) << "Could not satisfy assertion:\n";
430 ast::print( ss, assn.first, tabs );
431
432 errors.emplace_back( ss.str() );
433 goto nextSat;
434 }
435 }
436
437 if ( sat.deferred.empty() ) {
438 // either add successful match or push back next state
439 if ( sat.newNeed.empty() ) {
440 finalizeAssertions(
441 sat.cand, sat.inferred, thresholds, std::move( sat.costs ), out );
442 } else {
443 nextSats.emplace_back( std::move( sat ), IterateState );
444 }
445 } else if ( sat.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 print( ss, *sat.cand, ++tabs );
451 ss << (tabs-1) << "Too many non-unique satisfying assignments for assertions:\n";
452 for ( const auto & d : sat.deferred ) {
453 ast::print( ss, d.decl, tabs );
454 }
455
456 errors.emplace_back( ss.str() );
457 goto nextSat;
458 } else {
459 // combine deferred assertions by mutual compatibility
460 std::vector< CandidateEnvMerger::OutType > compatible = filterCombos(
461 sat.deferred, CandidateEnvMerger{ sat.cand->env, sat.cand->open, sat.symtab } );
462
463 // fail early if no mutually-compatible assertion satisfaction
464 if ( compatible.empty() ) {
465 Indenter tabs{ 3 };
466 std::ostringstream ss;
467 ss << tabs << "Unsatisfiable alternative:\n";
468 print( ss, *sat.cand, ++tabs );
469 ss << (tabs-1) << "No mutually-compatible satisfaction for assertions:\n";
470 for ( const auto& d : sat.deferred ) {
471 ast::print( ss, d.decl, tabs );
472 }
473
474 errors.emplace_back( ss.str() );
475 goto nextSat;
476 }
477
478 // sort by cost (for overall pruning order)
479 std::sort( compatible.begin(), compatible.end() );
480
481 // process mutually-compatible combinations
482 for ( auto & compat : compatible ) {
483 // set up next satisfaction state
484 CandidateRef nextCand = std::make_shared<Candidate>(
485 sat.cand->expr, std::move( compat.env ), std::move( compat.open ),
486 ast::AssertionSet{} /* need moved into satisfaction state */,
487 sat.cand->cost, sat.cand->cvtCost );
488
489 ast::AssertionSet nextNewNeed{ sat.newNeed };
490 InferCache nextInferred{ sat.inferred };
491
492 CostVec nextCosts{ sat.costs };
493 nextCosts.back() += compat.cost;
494
495 ast::SymbolTable nextSymtab{ sat.symtab };
496
497 // add compatible assertions to new satisfaction state
498 for ( DeferRef r : compat.assns ) {
499 AssnCandidate match = r.match;
500 addToSymbolTable( match.have, nextSymtab );
501 nextNewNeed.insert( match.need.begin(), match.need.end() );
502
503 bindAssertion( r.decl, r.info, nextCand, match, nextInferred );
504 }
505
506 // either add successful match or push back next state
507 if ( nextNewNeed.empty() ) {
508 finalizeAssertions(
509 nextCand, nextInferred, thresholds, std::move( nextCosts ), out );
510 } else {
511 nextSats.emplace_back(
512 std::move( nextCand ), std::move( nextNewNeed ),
513 std::move( nextInferred ), std::move( nextCosts ),
514 std::move( nextSymtab ) );
515 }
516 }
517 }
518 nextSat:; }
519
520 // finish or reset for next round
521 if ( nextSats.empty() ) return;
522 sats.swap( nextSats );
523 nextSats.clear();
524 }
525
526 // exceeded recursion limit if reaches here
527 if ( out.empty() ) {
528 SemanticError( cand->expr->location, "Too many recursive assertions" );
529 }
530}
531
532} // namespace ResolvExpr
533
534// Local Variables: //
535// tab-width: 4 //
536// mode: c++ //
537// compile-command: "make install" //
538// End: //
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