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source: src/ResolvExpr/ResolveAssertions.cc @ e99e43f

ADTaaron-thesisarm-ehast-experimentalcleanup-dtorsdeferred_resnenumforall-pointer-decayjacob/cs343-translationjenkins-sandboxnew-astnew-ast-unique-exprno_listpersistent-indexerpthread-emulationqualifiedEnum

Last change on this file since e99e43f was aeb8f70, checked in by Aaron Moss <a3moss@…>, 5 years ago
Fix memory leaks in assertion resolution
Property mode set to `100644`
File size: 15.5 KB

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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	// ResolveAssertions.cc --
8	//
9	// Author : Aaron B. Moss
10	// Created On : Fri Oct 05 13:46:00 2018
11	// Last Modified By : Aaron B. Moss
12	// Last Modified On : Fri Oct 05 13:46:00 2018
13	// Update Count : 1
14	//
15
16	#include "ResolveAssertions.h"
17
18	#include <algorithm> // for sort
19	#include <cassert> // for assertf
20	#include <list> // for list
21	#include <memory> // for unique_ptr
22	#include <unordered_map> // for unordered_map, unordered_multimap
23	#include <utility> // for move
24	#include <vector> // for vector
25
26	#include "Alternative.h" // for Alternative, AssertionItem, AssertionList
27	#include "Common/FilterCombos.h" // for filterCombos
28	#include "Common/utility.h" // for sort_mins
29	#include "ResolvExpr/RenameVars.h" // for renameTyVars
30	#include "SymTab/Indexer.h" // for Indexer
31	#include "SymTab/Mangler.h" // for Mangler
32	#include "SynTree/Expression.h" // for InferredParams
33	#include "TypeEnvironment.h" // for TypeEnvironment, etc.
34	#include "typeops.h" // for adjustExprType
35	#include "Unify.h" // for unify
36
37	namespace ResolvExpr {
38	/// Unified assertion candidate
39	struct AssnCandidate {
40	SymTab::Indexer::IdData cdata; ///< Satisfying declaration
41	Type* adjType; ///< Satisfying type
42	TypeEnvironment env; ///< Post-unification environment
43	AssertionSet have; ///< Post-unification have-set
44	AssertionSet need; ///< Post-unification need-set
45	OpenVarSet openVars; ///< Post-unification open-var set
46	UniqueId resnSlot; ///< Slot for any recursive assertion IDs
47
48	AssnCandidate( const SymTab::Indexer::IdData& cdata, Type* adjType, TypeEnvironment&& env,
49	AssertionSet&& have, AssertionSet&& need, OpenVarSet&& openVars, UniqueId resnSlot )
50	: cdata(cdata), adjType(adjType), env(std::move(env)), have(std::move(have)),
51	need(std::move(need)), openVars(std::move(openVars)), resnSlot(resnSlot) {}
52	};
53
54	/// List of candidate assertion resolutions
55	using CandidateList = std::vector<AssnCandidate>;
56
57	/// Reference to single deferred item
58	struct DeferRef {
59	const DeclarationWithType* decl;
60	const AssertionSetValue& info;
61	const AssnCandidate& match;
62	};
63
64	/// Wrapper for the deferred items from a single assertion resolution.
65	/// Acts like indexed list of DeferRef
66	struct DeferItem {
67	DeclarationWithType* decl;
68	AssertionSetValue info;
69	CandidateList matches;
70
71	DeferItem( DeclarationWithType* decl, const AssertionSetValue& info,
72	CandidateList&& matches )
73	: decl(decl), info(info), matches(std::move(matches)) {}
74
75	bool empty() const { return matches.empty(); }
76
77	CandidateList::size_type size() const { return matches.size(); }
78
79	DeferRef operator[] ( unsigned i ) const { return { decl, info, matches[i] }; }
80	};
81
82	/// List of deferred resolution items
83	using DeferList = std::vector<DeferItem>;
84
85	/// Combo iterator that combines candidates into an output list, merging their environments.
86	/// Rejects an appended candidate if the environments cannot be merged.
87	class CandidateEnvMerger {
88	/// Current list of merged candidates
89	std::vector<DeferRef> crnt;
90	/// Stack of environments to support backtracking
91	std::vector<TypeEnvironment> envs;
92	/// Stack of open variables to support backtracking
93	std::vector<OpenVarSet> varSets;
94	/// Indexer to use for merges
95	const SymTab::Indexer& indexer;
96
97	public:
98	/// The merged environment/open variables and the list of candidates
99	struct OutType {
100	TypeEnvironment env;
101	OpenVarSet openVars;
102	std::vector<DeferRef> assns;
103
104	OutType( const TypeEnvironment& env, const OpenVarSet& openVars,
105	const std::vector<DeferRef>& assns )
106	: env(env), openVars(openVars), assns(assns) {}
107	};
108
109	CandidateEnvMerger( const TypeEnvironment& env, const OpenVarSet& openVars,
110	const SymTab::Indexer& indexer )
111	: crnt(), envs{ env }, varSets{ openVars }, indexer(indexer) {}
112
113	bool append( DeferRef i ) {
114	TypeEnvironment env = envs.back();
115	OpenVarSet openVars = varSets.back();
116	mergeOpenVars( openVars, i.match.openVars );
117
118	if ( ! env.combine( i.match.env, openVars, indexer ) ) return false;
119
120	crnt.emplace_back( i );
121	envs.emplace_back( env );
122	varSets.emplace_back( openVars );
123	return true;
124	}
125
126	void backtrack() {
127	crnt.pop_back();
128	envs.pop_back();
129	varSets.pop_back();
130	}
131
132	OutType finalize() { return { envs.back(), varSets.back(), crnt }; }
133	};
134
135	/// Comparator for CandidateEnvMerger outputs that sums their costs and caches the stored
136	/// sums
137	struct CandidateCost {
138	using Element = CandidateEnvMerger::OutType;
139	private:
140	using Memo = std::unordered_map<const Element*, Cost>;
141	mutable Memo cache; ///< cache of element costs
142	const SymTab::Indexer& indexer; ///< Indexer for costing
143
144	public:
145	CandidateCost( const SymTab::Indexer& indexer ) : indexer(indexer) {}
146
147	/// reports the cost of an element
148	Cost get( const Element& x ) const {
149	Memo::const_iterator it = cache.find( &x );
150	if ( it == cache.end() ) {
151	Cost k = Cost::zero;
152	for ( const auto& assn : x.assns ) {
153	k += computeConversionCost(
154	assn.match.adjType, assn.decl->get_type(), indexer, x.env );
155	}
156	it = cache.emplace_hint( it, &x, k );
157	}
158	return it->second;
159	}
160
161	/// compares elements by cost
162	bool operator() ( const Element& a, const Element& b ) const {
163	return get( a ) < get( b );
164	}
165	};
166
167	/// Set of assertion resolutions, grouped by resolution ID
168	using InferCache = std::unordered_map< UniqueId, InferredParams >;
169
170	/// Flag for state iteration
171	enum IterateFlag { IterateState };
172
173	/// State needed to resolve a set of assertions
174	struct ResnState {
175	Alternative alt; ///< Alternative assertion is rooted on
176	AssertionList need; ///< Assertions to find
177	AssertionSet newNeed; ///< New assertions for current resolutions
178	DeferList deferred; ///< Deferred matches
179	InferCache inferred; ///< Cache of already-inferred parameters
180	SymTab::Indexer& indexer; ///< Name lookup (depends on previous assertions)
181
182	/// Initial resolution state for an alternative
183	ResnState( Alternative& a, SymTab::Indexer& indexer )
184	: alt(a), need(), newNeed(), deferred(), inferred(), indexer(indexer) {
185	need.swap( a.need );
186	}
187
188	/// Updated resolution state with new need-list
189	ResnState( ResnState&& o, IterateFlag )
190	: alt(std::move(o.alt)), need(o.newNeed.begin(), o.newNeed.end()), newNeed(), deferred(),
191	inferred(std::move(o.inferred)), indexer(o.indexer) {}
192	};
193
194	/// Binds a single assertion, updating resolution state
195	void bindAssertion( const DeclarationWithType* decl, AssertionSetValue info, Alternative& alt,
196	AssnCandidate& match, InferCache& inferred ) {
197
198	DeclarationWithType* candidate = match.cdata.id;
199	assertf( candidate->get_uniqueId(), "Assertion candidate does not have a unique ID: %s", toString( candidate ).c_str() );
200
201	Expression* varExpr = match.cdata.combine( alt.cvtCost );
202	delete varExpr->result;
203	varExpr->result = match.adjType->clone();
204	if ( match.resnSlot ) { varExpr->resnSlots.push_back( match.resnSlot ); }
205
206	// place newly-inferred assertion in proper place in cache
207	inferred[ info.resnSlot ][ decl->get_uniqueId() ] = ParamEntry{
208	candidate->get_uniqueId(), match.adjType->clone(), decl->get_type()->clone(),
209	varExpr };
210
211	// // follow the current assertion's ID chain to find the correct set of inferred parameters
212	// // to add the candidate o (i.e. the set of inferred parameters belonging to the entity
213	// // which requested the assertion parameter)
214	// InferredParams* inferParams = &alt.expr->inferParams;
215	// for ( UniqueId id : info.idChain ) {
216	// inferParams = (*inferParams)[ id ].inferParams.get();
217	// }
218
219	// (*inferParams)[ decl->get_uniqueId() ] = ParamEntry{
220	// candidate->get_uniqueId(), match.adjType, decl->get_type()->clone(), varExpr };
221	}
222
223	/// Adds a captured assertion to the symbol table
224	void addToIndexer( AssertionSet &assertSet, SymTab::Indexer &indexer ) {
225	for ( AssertionSet::iterator i = assertSet.begin(); i != assertSet.end(); ++i ) {
226	if ( i->second.isUsed ) {
227	indexer.addId( i->first );
228	}
229	}
230	}
231
232	// in AlternativeFinder.cc; unique ID for assertion resolutions
233	extern UniqueId globalResnSlot;
234
235	/// Resolve a single assertion, in context
236	bool resolveAssertion( AssertionItem& assn, ResnState& resn ) {
237	// skip unused assertions
238	if ( ! assn.info.isUsed ) return true;
239
240	// lookup candidates for this assertion
241	std::list< SymTab::Indexer::IdData > candidates;
242	resn.indexer.lookupId( assn.decl->name, candidates );
243
244	// find the candidates that unify with the desired type
245	CandidateList matches;
246	for ( const auto& cdata : candidates ) {
247	DeclarationWithType* candidate = cdata.id;
248
249	// build independent unification context for candidate
250	AssertionSet have, newNeed;
251	TypeEnvironment newEnv{ resn.alt.env };
252	OpenVarSet newOpenVars{ resn.alt.openVars };
253	Type* adjType = candidate->get_type()->clone();
254	adjustExprType( adjType, newEnv, resn.indexer );
255	renameTyVars( adjType );
256
257	// keep unifying candidates
258	if ( unify( assn.decl->get_type(), adjType, newEnv, newNeed, have, newOpenVars,
259	resn.indexer ) ) {
260	// set up binding slot for recursive assertions
261	UniqueId crntResnSlot = 0;
262	if ( ! newNeed.empty() ) {
263	crntResnSlot = ++globalResnSlot;
264	for ( auto& a : newNeed ) {
265	a.second.resnSlot = crntResnSlot;
266	}
267	}
268	// // set up idChain on new assertions
269	// for ( auto& a : newNeed ) {
270	// a.second.idChain = assn.info.idChain;
271	// a.second.idChain.push_back( assn.decl->get_uniqueId() );
272	// }
273
274	matches.emplace_back( cdata, adjType, std::move(newEnv), std::move(have),
275	std::move(newNeed), std::move(newOpenVars), crntResnSlot );
276	} else {
277	delete adjType;
278	}
279	}
280
281	// break if no suitable assertion
282	if ( matches.empty() ) return false;
283
284	// defer if too many suitable assertions
285	if ( matches.size() > 1 ) {
286	resn.deferred.emplace_back( assn.decl, assn.info, std::move(matches) );
287	return true;
288	}
289
290	// otherwise bind current match in ongoing scope
291	AssnCandidate& match = matches.front();
292	addToIndexer( match.have, resn.indexer );
293	resn.newNeed.insert( match.need.begin(), match.need.end() );
294	resn.alt.env = std::move(match.env);
295	resn.alt.openVars = std::move(match.openVars);
296
297	bindAssertion( assn.decl, assn.info, resn.alt, match, resn.inferred );
298	return true;
299	}
300
301	/// Associates inferred parameters with an expression
302	struct InferMatcher {
303	InferCache& inferred;
304
305	InferMatcher( InferCache& inferred ) : inferred( inferred ) {}
306
307	Expression* postmutate( Expression* expr ) {
308	// defer missing inferred parameters until they are hopefully found later
309	std::vector<UniqueId> missingSlots;
310	// place inferred parameters into resolution slots
311	for ( UniqueId slot : expr->resnSlots ) {
312	// fail if no matching parameters found
313	auto it = inferred.find( slot );
314	if ( it == inferred.end() ) {
315	missingSlots.push_back( slot );
316	continue;
317	}
318	InferredParams& inferParams = it->second;
319
320	// place inferred parameters into proper place in expression
321	for ( auto& entry : inferParams ) {
322	// recurse on inferParams of resolved expressions
323	entry.second.expr = postmutate( entry.second.expr );
324	// xxx - look at entry.second.inferParams?
325	expr->inferParams[ entry.first ] = entry.second;
326	}
327	}
328
329	// clear resolution slots and return
330	expr->resnSlots.swap( missingSlots );
331	return expr;
332	}
333	};
334
335	void finalizeAssertions( Alternative& alt, InferCache& inferred, AltList& out ) {
336	PassVisitor<InferMatcher> matcher{ inferred };
337	alt.expr = alt.expr->acceptMutator( matcher );
338	out.emplace_back( alt );
339	}
340
341	/// Limit to depth of recursion of assertion satisfaction
342	static const int recursionLimit = /* 10 */ 4;
343
344	void resolveAssertions( Alternative& alt, const SymTab::Indexer& indexer, AltList& out ) {
345	// finish early if no assertions to resolve
346	if ( alt.need.empty() ) {
347	out.emplace_back( alt );
348	return;
349	}
350
351	// build list of possible resolutions
352	using ResnList = std::vector<ResnState>;
353	SymTab::Indexer root_indexer{ indexer };
354	ResnList resns{ ResnState{ alt, root_indexer } };
355	ResnList new_resns{};
356
357	// resolve assertions in breadth-first-order up to a limited number of levels deep
358	for ( unsigned level = 0; level < recursionLimit; ++level ) {
359	// scan over all mutually-compatible resolutions
360	for ( auto& resn : resns ) {
361	// make initial pass at matching assertions
362	for ( auto& assn : resn.need ) {
363	// fail early if any assertion is not resolvable
364	if ( ! resolveAssertion( assn, resn ) ) goto nextResn;
365	}
366
367	if ( resn.deferred.empty() ) {
368	// either add successful match or push back next state
369	if ( resn.newNeed.empty() ) {
370	finalizeAssertions( resn.alt, resn.inferred, out );
371	} else {
372	new_resns.emplace_back( std::move(resn), IterateState );
373	}
374	} else {
375	// resolve deferred assertions by mutual compatibility
376	std::vector<CandidateEnvMerger::OutType> compatible = filterCombos(
377	resn.deferred,
378	CandidateEnvMerger{ resn.alt.env, resn.alt.openVars, resn.indexer } );
379	// sort by cost
380	CandidateCost coster{ resn.indexer };
381	std::sort( compatible.begin(), compatible.end(), coster );
382	// // sort by cost if pruning
383	// if ( pruneAssertions ) {
384	// auto lmin = sort_mins( compatible.begin(), compatible.end(),
385	// CandidateCost{resn.indexer} );
386	// compatible.erase( lmin, compatible.end() );
387	// }
388
389	// keep map of detected options
390	std::unordered_map<std::string, Cost> found;
391	for ( auto& compat : compatible ) {
392	// filter by environment-adjusted result type, keep only cheapest option
393	Type* resType = alt.expr->result->clone();
394	compat.env.apply( resType );
395	// skip if cheaper alternative already processed with same result type
396	Cost resCost = coster.get( compat );
397	auto it = found.emplace( SymTab::Mangler::mangleType( resType ), resCost );
398	delete resType;
399	if ( it.second == false && it.first->second < resCost ) continue;
400
401	// proceed with resolution step
402	ResnState new_resn = resn;
403
404	// add compatible assertions to new resolution state
405	for ( DeferRef r : compat.assns ) {
406	AssnCandidate match = r.match;
407	addToIndexer( match.have, new_resn.indexer );
408	new_resn.newNeed.insert( match.need.begin(), match.need.end() );
409
410	bindAssertion( r.decl, r.info, new_resn.alt, match, new_resn.inferred );
411	}
412
413	// set mutual environment into resolution state
414	new_resn.alt.env = std::move(compat.env);
415	new_resn.alt.openVars = std::move(compat.openVars);
416
417	// either add sucessful match or push back next state
418	if ( new_resn.newNeed.empty() ) {
419	finalizeAssertions( new_resn.alt, new_resn.inferred, out );
420	} else {
421	new_resns.emplace_back( std::move(new_resn), IterateState );
422	}
423	}
424	}
425	nextResn:; }
426
427	// finish or reset for next round
428	if ( new_resns.empty() ) return;
429	resns.swap( new_resns );
430	new_resns.clear();
431	}
432
433	// exceeded recursion limit if reaches here
434	if ( out.empty() ) {
435	SemanticError( alt.expr->location, "Too many recursive assertions" );
436	}
437	}
438	} // namespace ResolvExpr
439
440	// Local Variables: //
441	// tab-width: 4 //
442	// mode: c++ //
443	// compile-command: "make install" //
444	// End: //

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