source: src/ResolvExpr/SatisfyAssertions.cpp@ 50202fa

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 50202fa was eef8dfb, checked in by Thierry Delisle <tdelisle@…>, 5 years ago

Merge branch 'master' into dkobets-vector
  • Property mode set to 100644
File size: 19.2 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::VariableExpr * expr;
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::VariableExpr * expr;
80 const ast::AssertionSetValue & info;
81 AssnCandidateList matches;
82
83 DeferItem(
84 const ast::VariableExpr * d, const ast::AssertionSetValue & i, AssnCandidateList && ms )
85 : expr( 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 { expr, 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->var ); }
141 }
142 }
143
144 /// Binds a single assertion, updating satisfaction state
145 void bindAssertion(
146 const ast::VariableExpr * expr, 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 ][ expr->var->uniqueId ] = ast::ParamEntry{
159 candidate->uniqueId, candidate, match.adjType, expr->result, 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->var->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 = assn.first->result.strict_as<ast::PointerType>()->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->var->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 && candidate->linkage == ast::Linkage::AutoGen) 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->result;
203 ast::ptr< ast::Type > adjType =
204 renameTyVars( adjustExprType( candidate->get_type(), newEnv, sat.symtab ), GEN_USAGE, false );
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.expr->result, 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 cost.decSpec( func->assertions.size() );
353 }
354 }
355
356 bool operator< ( const OutType & o ) const { return cost < o.cost; }
357 };
358
359 CandidateEnvMerger(
360 const ast::TypeEnvironment & env, const ast::OpenVarSet & open,
361 const ast::SymbolTable & syms )
362 : crnt(), envs{ env }, opens{ open }, symtab( syms ) {}
363
364 bool append( DeferRef i ) {
365 ast::TypeEnvironment env = envs.back();
366 ast::OpenVarSet open = opens.back();
367 mergeOpenVars( open, i.match.open );
368
369 if ( ! env.combine( i.match.env, open, symtab ) ) return false;
370
371 crnt.emplace_back( i );
372 envs.emplace_back( std::move( env ) );
373 opens.emplace_back( std::move( open ) );
374 return true;
375 }
376
377 void backtrack() {
378 crnt.pop_back();
379 envs.pop_back();
380 opens.pop_back();
381 }
382
383 OutType finalize() { return { envs.back(), opens.back(), crnt, symtab }; }
384 };
385
386 /// Limit to depth of recursion of assertion satisfaction
387 static const int recursionLimit = 8;
388 /// Maximum number of simultaneously-deferred assertions to attempt concurrent satisfaction of
389 static const int deferLimit = 10;
390} // anonymous namespace
391
392void satisfyAssertions(
393 CandidateRef & cand, const ast::SymbolTable & symtab, CandidateList & out,
394 std::vector<std::string> & errors
395) {
396 // finish early if no assertions to satisfy
397 if ( cand->need.empty() ) {
398 out.emplace_back( cand );
399 return;
400 }
401
402 // build list of possible combinations of satisfying declarations
403 std::vector< SatState > sats{ SatState{ cand, symtab } };
404 std::vector< SatState > nextSats{};
405
406 // pruning thresholds by result type of output candidates.
407 // Candidates *should* be generated in sorted order, so no need to retroactively prune
408 PruneMap thresholds;
409
410 // satisfy assertions in breadth-first order over the recursion tree of assertion satisfaction.
411 // Stop recursion at a limited number of levels deep to avoid infinite loops.
412 for ( unsigned level = 0; level < recursionLimit; ++level ) {
413 // for each current mutually-compatible set of assertions
414 for ( SatState & sat : sats ) {
415 // stop this branch if a better option is already found
416 auto it = thresholds.find( pruneKey( *sat.cand ) );
417 if ( it != thresholds.end() && it->second < sat.costs ) goto nextSat;
418
419 // should a limit be imposed? worst case here is O(n^2) but very unlikely to happen.
420 for (unsigned resetCount = 0; ; ++resetCount) {
421 ast::AssertionList next;
422 resetTyVarRenaming();
423 // make initial pass at matching assertions
424 for ( auto & assn : sat.need ) {
425 // fail early if any assertion is not satisfiable
426 if ( ! satisfyAssertion( assn, sat ) ) {
427 next.emplace_back(assn);
428 // goto nextSat;
429 }
430 }
431 // success
432 if (next.empty()) break;
433 // fail if nothing resolves
434 else if (next.size() == sat.need.size()) {
435 Indenter tabs{ 3 };
436 std::ostringstream ss;
437 ss << tabs << "Unsatisfiable alternative:\n";
438 print( ss, *sat.cand, ++tabs );
439 ss << (tabs-1) << "Could not satisfy assertion:\n";
440 ast::print( ss, next[0].first, tabs );
441
442 errors.emplace_back( ss.str() );
443 goto nextSat;
444 }
445 sat.need = std::move(next);
446 }
447
448 if ( sat.deferred.empty() ) {
449 // either add successful match or push back next state
450 if ( sat.newNeed.empty() ) {
451 finalizeAssertions(
452 sat.cand, sat.inferred, thresholds, std::move( sat.costs ), out );
453 } else {
454 nextSats.emplace_back( std::move( sat ), IterateState );
455 }
456 } else if ( sat.deferred.size() > deferLimit ) {
457 // too many deferred assertions to attempt mutual compatibility
458 Indenter tabs{ 3 };
459 std::ostringstream ss;
460 ss << tabs << "Unsatisfiable alternative:\n";
461 print( ss, *sat.cand, ++tabs );
462 ss << (tabs-1) << "Too many non-unique satisfying assignments for assertions:\n";
463 for ( const auto & d : sat.deferred ) {
464 ast::print( ss, d.expr, tabs );
465 }
466
467 errors.emplace_back( ss.str() );
468 goto nextSat;
469 } else {
470 // combine deferred assertions by mutual compatibility
471 std::vector< CandidateEnvMerger::OutType > compatible = filterCombos(
472 sat.deferred, CandidateEnvMerger{ sat.cand->env, sat.cand->open, sat.symtab } );
473
474 // fail early if no mutually-compatible assertion satisfaction
475 if ( compatible.empty() ) {
476 Indenter tabs{ 3 };
477 std::ostringstream ss;
478 ss << tabs << "Unsatisfiable alternative:\n";
479 print( ss, *sat.cand, ++tabs );
480 ss << (tabs-1) << "No mutually-compatible satisfaction for assertions:\n";
481 for ( const auto& d : sat.deferred ) {
482 ast::print( ss, d.expr, tabs );
483 }
484
485 errors.emplace_back( ss.str() );
486 goto nextSat;
487 }
488
489 // sort by cost (for overall pruning order)
490 std::sort( compatible.begin(), compatible.end() );
491
492 // process mutually-compatible combinations
493 for ( auto & compat : compatible ) {
494 // set up next satisfaction state
495 CandidateRef nextCand = std::make_shared<Candidate>(
496 sat.cand->expr, std::move( compat.env ), std::move( compat.open ),
497 ast::AssertionSet{} /* need moved into satisfaction state */,
498 sat.cand->cost, sat.cand->cvtCost );
499
500 ast::AssertionSet nextNewNeed{ sat.newNeed };
501 InferCache nextInferred{ sat.inferred };
502
503 CostVec nextCosts{ sat.costs };
504 nextCosts.back() += compat.cost;
505
506 ast::SymbolTable nextSymtab{ sat.symtab };
507
508 // add compatible assertions to new satisfaction state
509 for ( DeferRef r : compat.assns ) {
510 AssnCandidate match = r.match;
511 addToSymbolTable( match.have, nextSymtab );
512 nextNewNeed.insert( match.need.begin(), match.need.end() );
513
514 bindAssertion( r.expr, r.info, nextCand, match, nextInferred );
515 }
516
517 // either add successful match or push back next state
518 if ( nextNewNeed.empty() ) {
519 finalizeAssertions(
520 nextCand, nextInferred, thresholds, std::move( nextCosts ), out );
521 } else {
522 nextSats.emplace_back(
523 std::move( nextCand ), std::move( nextNewNeed ),
524 std::move( nextInferred ), std::move( nextCosts ),
525 std::move( nextSymtab ) );
526 }
527 }
528 }
529 nextSat:; }
530
531 // finish or reset for next round
532 if ( nextSats.empty() ) return;
533 sats.swap( nextSats );
534 nextSats.clear();
535 }
536
537 // exceeded recursion limit if reaches here
538 if ( out.empty() ) {
539 SemanticError( cand->expr->location, "Too many recursive assertions" );
540 }
541}
542
543} // namespace ResolvExpr
544
545// Local Variables: //
546// tab-width: 4 //
547// mode: c++ //
548// compile-command: "make install" //
549// End: //
Note: See TracBrowser for help on using the repository browser.