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source: src/ResolvExpr/SatisfyAssertions.cpp @ 41870a5

ADTast-experimentalenumpthread-emulationqualifiedEnum

Last change on this file since 41870a5 was eef8dfb, checked in by Thierry Delisle <tdelisle@…>, 4 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
43	namespace ResolvExpr {
44
45	// in CandidateFinder.cpp; unique ID for assertion satisfaction
46	extern UniqueId globalResnSlot;
47
48	namespace {
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
392	void 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: //

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