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source: src/ResolvExpr/ResolveAssertions.cc @ 686f731

ADTarm-ehast-experimentalcleanup-dtorsenumforall-pointer-decayjacob/cs343-translationjenkins-sandboxnew-astnew-ast-unique-exprpthread-emulationqualifiedEnum

Last change on this file since 686f731 was 493a992, checked in by Aaron Moss <a3moss@…>, 6 years ago
Add specialization cost to assertion disambiguation
Property mode set to `100644`
File size: 16.0 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 <sstream> // for ostringstream
23	#include <string> // for string
24	#include <unordered_map> // for unordered_map, unordered_multimap
25	#include <utility> // for move
26	#include <vector> // for vector
27
28	#include "Alternative.h" // for Alternative, AssertionItem, AssertionList
29	#include "Common/FilterCombos.h" // for filterCombos
30	#include "Common/Indenter.h" // for Indenter
31	#include "Common/utility.h" // for sort_mins
32	#include "ResolvExpr/RenameVars.h" // for renameTyVars
33	#include "SymTab/Indexer.h" // for Indexer
34	#include "SymTab/Mangler.h" // for Mangler
35	#include "SynTree/Expression.h" // for InferredParams
36	#include "TypeEnvironment.h" // for TypeEnvironment, etc.
37	#include "typeops.h" // for adjustExprType, specCost
38	#include "Unify.h" // for unify
39
40	namespace ResolvExpr {
41	/// Unified assertion candidate
42	struct AssnCandidate {
43	SymTab::Indexer::IdData cdata; ///< Satisfying declaration
44	Type* adjType; ///< Satisfying type
45	TypeEnvironment env; ///< Post-unification environment
46	AssertionSet have; ///< Post-unification have-set
47	AssertionSet need; ///< Post-unification need-set
48	OpenVarSet openVars; ///< Post-unification open-var set
49	UniqueId resnSlot; ///< Slot for any recursive assertion IDs
50
51	AssnCandidate( const SymTab::Indexer::IdData& cdata, Type* adjType, TypeEnvironment&& env,
52	AssertionSet&& have, AssertionSet&& need, OpenVarSet&& openVars, UniqueId resnSlot )
53	: cdata(cdata), adjType(adjType), env(std::move(env)), have(std::move(have)),
54	need(std::move(need)), openVars(std::move(openVars)), resnSlot(resnSlot) {}
55	};
56
57	/// List of candidate assertion resolutions
58	using CandidateList = std::vector<AssnCandidate>;
59
60	/// Reference to single deferred item
61	struct DeferRef {
62	const DeclarationWithType* decl;
63	const AssertionSetValue& info;
64	const AssnCandidate& match;
65	};
66
67	/// Wrapper for the deferred items from a single assertion resolution.
68	/// Acts like indexed list of DeferRef
69	struct DeferItem {
70	const DeclarationWithType* decl;
71	const AssertionSetValue& info;
72	CandidateList matches;
73
74	DeferItem( DeclarationWithType* decl, const AssertionSetValue& info, CandidateList&& matches )
75	: decl(decl), info(info), matches(std::move(matches)) {}
76
77	bool empty() const { return matches.empty(); }
78
79	CandidateList::size_type size() const { return matches.size(); }
80
81	DeferRef operator[] ( unsigned i ) const { return { decl, info, matches[i] }; }
82	};
83
84	/// List of deferred resolution items
85	using DeferList = std::vector<DeferItem>;
86
87	/// Combo iterator that combines candidates into an output list, merging their environments.
88	/// Rejects an appended candidate if the environments cannot be merged.
89	class CandidateEnvMerger {
90	/// Current list of merged candidates
91	std::vector<DeferRef> crnt;
92	/// Stack of environments to support backtracking
93	std::vector<TypeEnvironment> envs;
94	/// Stack of open variables to support backtracking
95	std::vector<OpenVarSet> varSets;
96	/// Indexer to use for merges
97	const SymTab::Indexer& indexer;
98
99	public:
100	/// The merged environment/open variables and the list of candidates
101	struct OutType {
102	TypeEnvironment env;
103	OpenVarSet openVars;
104	std::vector<DeferRef> assns;
105
106	OutType( const TypeEnvironment& env, const OpenVarSet& openVars,
107	const std::vector<DeferRef>& assns )
108	: env(env), openVars(openVars), assns(assns) {}
109	};
110
111	CandidateEnvMerger( const TypeEnvironment& env, const OpenVarSet& openVars,
112	const SymTab::Indexer& indexer )
113	: crnt(), envs{ env }, varSets{ openVars }, indexer(indexer) {}
114
115	bool append( DeferRef i ) {
116	TypeEnvironment env = envs.back();
117	OpenVarSet openVars = varSets.back();
118	mergeOpenVars( openVars, i.match.openVars );
119
120	if ( ! env.combine( i.match.env, openVars, indexer ) ) return false;
121
122	crnt.emplace_back( i );
123	envs.emplace_back( env );
124	varSets.emplace_back( openVars );
125	return true;
126	}
127
128	void backtrack() {
129	crnt.pop_back();
130	envs.pop_back();
131	varSets.pop_back();
132	}
133
134	OutType finalize() { return { envs.back(), varSets.back(), crnt }; }
135	};
136
137	/// Comparator for CandidateEnvMerger outputs that sums their costs and caches the stored
138	/// sums
139	struct CandidateCost {
140	using Element = CandidateEnvMerger::OutType;
141	private:
142	using Memo = std::unordered_map<const Element*, Cost>;
143	mutable Memo cache; ///< cache of element costs
144	const SymTab::Indexer& indexer; ///< Indexer for costing
145
146	public:
147	CandidateCost( const SymTab::Indexer& indexer ) : indexer(indexer) {}
148
149	/// reports the cost of an element
150	Cost get( const Element& x ) const {
151	Memo::const_iterator it = cache.find( &x );
152	if ( it == cache.end() ) {
153	Cost k = Cost::zero;
154	for ( const auto& assn : x.assns ) {
155	k += computeConversionCost(
156	assn.match.adjType, assn.decl->get_type(), indexer, x.env );
157
158	// mark vars+specialization cost on function-type assertions
159	PointerType* ptr = dynamic_cast< PointerType* >( assn.decl->get_type() );
160	if ( ! ptr ) continue;
161	FunctionType* func = dynamic_cast< FunctionType* >( ptr->base );
162	if ( ! func ) continue;
163
164	for ( DeclarationWithType* formal : func->parameters ) {
165	k.decSpec( specCost( formal->get_type() ) );
166	}
167	k.incVar( func->forall.size() );
168	for ( TypeDecl* td : func->forall ) {
169	k.decSpec( td->assertions.size() );
170	}
171	}
172	it = cache.emplace_hint( it, &x, k );
173	}
174	return it->second;
175	}
176
177	/// compares elements by cost
178	bool operator() ( const Element& a, const Element& b ) const {
179	return get( a ) < get( b );
180	}
181	};
182
183	/// Set of assertion resolutions, grouped by resolution ID
184	using InferCache = std::unordered_map< UniqueId, InferredParams >;
185
186	/// Flag for state iteration
187	enum IterateFlag { IterateState };
188
189	/// State needed to resolve a set of assertions
190	struct ResnState {
191	Alternative alt; ///< Alternative assertion is rooted on
192	AssertionList need; ///< Assertions to find
193	AssertionSet newNeed; ///< New assertions for current resolutions
194	DeferList deferred; ///< Deferred matches
195	InferCache inferred; ///< Cache of already-inferred parameters
196	SymTab::Indexer& indexer; ///< Name lookup (depends on previous assertions)
197
198	/// Initial resolution state for an alternative
199	ResnState( Alternative& a, SymTab::Indexer& indexer )
200	: alt(a), need(), newNeed(), deferred(), inferred(), indexer(indexer) {
201	need.swap( a.need );
202	}
203
204	/// Updated resolution state with new need-list
205	ResnState( ResnState&& o, IterateFlag )
206	: alt(std::move(o.alt)), need(o.newNeed.begin(), o.newNeed.end()), newNeed(), deferred(),
207	inferred(std::move(o.inferred)), indexer(o.indexer) {}
208	};
209
210	/// Binds a single assertion, updating resolution state
211	void bindAssertion( const DeclarationWithType* decl, AssertionSetValue info, Alternative& alt,
212	AssnCandidate& match, InferCache& inferred ) {
213
214	DeclarationWithType* candidate = match.cdata.id;
215	assertf( candidate->get_uniqueId(), "Assertion candidate does not have a unique ID: %s", toString( candidate ).c_str() );
216
217	Expression* varExpr = match.cdata.combine( alt.cvtCost );
218	delete varExpr->result;
219	varExpr->result = match.adjType->clone();
220	if ( match.resnSlot ) { varExpr->resnSlots.push_back( match.resnSlot ); }
221
222	// place newly-inferred assertion in proper place in cache
223	inferred[ info.resnSlot ][ decl->get_uniqueId() ] = ParamEntry{
224	candidate->get_uniqueId(), match.adjType->clone(), decl->get_type()->clone(),
225	varExpr };
226	}
227
228	/// Adds a captured assertion to the symbol table
229	void addToIndexer( AssertionSet &assertSet, SymTab::Indexer &indexer ) {
230	for ( auto& i : assertSet ) {
231	if ( i.second.isUsed ) {
232	indexer.addId( i.first );
233	}
234	}
235	}
236
237	// in AlternativeFinder.cc; unique ID for assertion resolutions
238	extern UniqueId globalResnSlot;
239
240	/// Resolve a single assertion, in context
241	bool resolveAssertion( AssertionItem& assn, ResnState& resn ) {
242	// skip unused assertions
243	if ( ! assn.info.isUsed ) return true;
244
245	// lookup candidates for this assertion
246	std::list< SymTab::Indexer::IdData > candidates;
247	resn.indexer.lookupId( assn.decl->name, candidates );
248
249	// find the candidates that unify with the desired type
250	CandidateList matches;
251	for ( const auto& cdata : candidates ) {
252	DeclarationWithType* candidate = cdata.id;
253
254	// build independent unification context for candidate
255	AssertionSet have, newNeed;
256	TypeEnvironment newEnv{ resn.alt.env };
257	OpenVarSet newOpenVars{ resn.alt.openVars };
258	Type* adjType = candidate->get_type()->clone();
259	adjustExprType( adjType, newEnv, resn.indexer );
260	renameTyVars( adjType );
261
262	// keep unifying candidates
263	if ( unify( assn.decl->get_type(), adjType, newEnv, newNeed, have, newOpenVars,
264	resn.indexer ) ) {
265	// set up binding slot for recursive assertions
266	UniqueId crntResnSlot = 0;
267	if ( ! newNeed.empty() ) {
268	crntResnSlot = ++globalResnSlot;
269	for ( auto& a : newNeed ) {
270	a.second.resnSlot = crntResnSlot;
271	}
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, std::list<std::string>& errors ) {
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 ) ) {
365	Indenter tabs{ Indenter::tabsize, 3 };
366	std::ostringstream ss;
367	ss << tabs << "Unsatisfiable alternative:\n";
368	resn.alt.print( ss, ++tabs );
369	ss << --tabs << "Could not satisfy assertion:\n";
370	assn.decl->print( ss, ++tabs );
371
372	errors.emplace_back( ss.str() );
373	goto nextResn;
374	}
375	}
376
377	if ( resn.deferred.empty() ) {
378	// either add successful match or push back next state
379	if ( resn.newNeed.empty() ) {
380	finalizeAssertions( resn.alt, resn.inferred, out );
381	} else {
382	new_resns.emplace_back( std::move(resn), IterateState );
383	}
384	} else {
385	// resolve deferred assertions by mutual compatibility
386	std::vector<CandidateEnvMerger::OutType> compatible = filterCombos(
387	resn.deferred,
388	CandidateEnvMerger{ resn.alt.env, resn.alt.openVars, resn.indexer } );
389	// fail early if no mutually-compatible assertion satisfaction
390	if ( compatible.empty() ) {
391	Indenter tabs{ Indenter::tabsize, 3 };
392	std::ostringstream ss;
393	ss << tabs << "Unsatisfiable alternative:\n";
394	resn.alt.print( ss, ++tabs );
395	ss << --tabs << "No mutually-compatible satisfaction for assertions:\n";
396	++tabs;
397	for ( const auto& d : resn.deferred ) {
398	d.decl->print( ss, tabs );
399	}
400
401	errors.emplace_back( ss.str() );
402	goto nextResn;
403	}
404	// sort by cost
405	CandidateCost coster{ resn.indexer };
406	std::sort( compatible.begin(), compatible.end(), coster );
407
408	// keep map of detected options
409	std::unordered_map<std::string, Cost> found;
410	for ( auto& compat : compatible ) {
411	// filter by environment-adjusted result type, keep only cheapest option
412	Type* resType = alt.expr->result->clone();
413	compat.env.apply( resType );
414	// skip if cheaper alternative already processed with same result type
415	Cost resCost = coster.get( compat );
416	auto it = found.emplace( SymTab::Mangler::mangleType( resType ), resCost );
417	delete resType;
418	if ( it.second == false && it.first->second < resCost ) continue;
419
420	// proceed with resolution step
421	ResnState new_resn = resn;
422
423	// add compatible assertions to new resolution state
424	for ( DeferRef r : compat.assns ) {
425	AssnCandidate match = r.match;
426	addToIndexer( match.have, new_resn.indexer );
427	new_resn.newNeed.insert( match.need.begin(), match.need.end() );
428
429	bindAssertion( r.decl, r.info, new_resn.alt, match, new_resn.inferred );
430	}
431
432	// set mutual environment into resolution state
433	new_resn.alt.env = std::move(compat.env);
434	new_resn.alt.openVars = std::move(compat.openVars);
435
436	// either add sucessful match or push back next state
437	if ( new_resn.newNeed.empty() ) {
438	finalizeAssertions( new_resn.alt, new_resn.inferred, out );
439	} else {
440	new_resns.emplace_back( std::move(new_resn), IterateState );
441	}
442	}
443	}
444	nextResn:; }
445
446	// finish or reset for next round
447	if ( new_resns.empty() ) return;
448	resns.swap( new_resns );
449	new_resns.clear();
450	}
451
452	// exceeded recursion limit if reaches here
453	if ( out.empty() ) {
454	SemanticError( alt.expr->location, "Too many recursive assertions" );
455	}
456	}
457	} // namespace ResolvExpr
458
459	// Local Variables: //
460	// tab-width: 4 //
461	// mode: c++ //
462	// compile-command: "make install" //
463	// End: //

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