source: src/ResolvExpr/SatisfyAssertions.cpp@ 42a99b0

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation jenkins-sandbox new-ast new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 42a99b0 was b69233ac, checked in by Aaron Moss <a3moss@…>, 6 years ago

Port assertion satisfaction to new AST
  • Property mode set to 100644
File size: 17.5 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 : Aaron B. Moss
12// Last Modified On : Mon Jun 10 17:45:00 2019
13// Update Count : 1
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 for ( const ast::SymbolTable::IdData & cdata : sat.symtab.lookupId( assn.first->name ) ) {
170 const ast::DeclWithType * candidate = cdata.id;
171
172 // build independent unification context for candidate
173 ast::AssertionSet have, newNeed;
174 ast::TypeEnvironment newEnv{ sat.cand->env };
175 ast::OpenVarSet newOpen{ sat.cand->open };
176 ast::ptr< ast::Type > toType = assn.first->get_type();
177 ast::ptr< ast::Type > adjType =
178 renameTyVars( adjustExprType( candidate->get_type(), newEnv, sat.symtab ) );
179
180 // only keep candidates which unify
181 if ( unify( toType, adjType, newEnv, newNeed, have, newOpen, sat.symtab ) ) {
182 // set up binding slot for recursive assertions
183 ast::UniqueId crntResnSlot = 0;
184 if ( ! newNeed.empty() ) {
185 crntResnSlot = ++globalResnSlot;
186 for ( auto & a : newNeed ) { a.second.resnSlot = crntResnSlot; }
187 }
188
189 matches.emplace_back(
190 cdata, adjType, std::move( newEnv ), std::move( newNeed ), std::move( have ),
191 std::move( newOpen ), crntResnSlot );
192 }
193 }
194
195 // break if no satisfying match
196 if ( matches.empty() ) return false;
197
198 // defer if too many satisfying matches
199 if ( matches.size() > 1 ) {
200 sat.deferred.emplace_back( assn.first, assn.second, std::move( matches ) );
201 return true;
202 }
203
204 // otherwise bind unique match in ongoing scope
205 AssnCandidate & match = matches.front();
206 addToSymbolTable( match.have, sat.symtab );
207 sat.newNeed.insert( match.need.begin(), match.need.end() );
208 sat.cand->env = std::move( match.env );
209 sat.cand->open = std::move( match.open );
210
211 bindAssertion( assn.first, assn.second, sat.cand, match, sat.inferred );
212 return true;
213 }
214
215 /// Map of candidate return types to recursive assertion satisfaction costs
216 using PruneMap = std::unordered_map< std::string, CostVec >;
217
218 /// Gets the pruning key for a candidate (derived from environment-adjusted return type)
219 std::string pruneKey( const Candidate & cand ) {
220 ast::ptr< ast::Type > resType = cand.expr->result;
221 cand.env.apply( resType );
222 return Mangle::mangle( resType, Mangle::typeMode() );
223 }
224
225 /// Associates inferred parameters with an expression
226 struct InferMatcher final {
227 InferCache & inferred;
228
229 InferMatcher( InferCache & inferred ) : inferred( inferred ) {}
230
231 const ast::Expr * postmutate( const ast::Expr * expr ) {
232 // Skip if no slots to find
233 if ( expr->inferred.mode != ast::Expr::InferUnion::Slots ) return expr;
234
235 // find inferred parameters for resolution slots
236 ast::InferredParams newInferred;
237 for ( UniqueId slot : expr->inferred.resnSlots() ) {
238 // fail if no matching assertions found
239 auto it = inferred.find( slot );
240 if ( it == inferred.end() ) {
241 assert(!"missing assertion");
242 }
243
244 // place inferred parameters into new map
245 for ( auto & entry : it->second ) {
246 // recurse on inferParams of resolved expressions
247 entry.second.expr = postmutate( entry.second.expr );
248 auto res = newInferred.emplace( entry );
249 assert( res.second && "all assertions newly placed" );
250 }
251 }
252
253 ast::Expr * ret = mutate( expr );
254 ret->inferred.set_inferParams( std::move( newInferred ) );
255 return ret;
256 }
257 };
258
259 /// Replace ResnSlots with InferParams and add alternative to output list, if it meets pruning
260 /// threshold.
261 void finalizeAssertions(
262 CandidateRef & cand, InferCache & inferred, PruneMap & thresholds, CostVec && costs,
263 CandidateList & out
264 ) {
265 // prune if cheaper alternative for same key has already been generated
266 std::string key = pruneKey( *cand );
267 auto it = thresholds.find( key );
268 if ( it != thresholds.end() ) {
269 if ( it->second < costs ) return;
270 } else {
271 thresholds.emplace_hint( it, key, std::move( costs ) );
272 }
273
274 // replace resolution slots with inferred parameters, add to output
275 ast::Pass< InferMatcher > matcher{ inferred };
276 cand->expr = cand->expr->accept( matcher );
277 out.emplace_back( cand );
278 }
279
280 /// Combo iterator that combines candidates into an output list, merging their environments.
281 /// Rejects an appended candidate if environments cannot be merged. See `Common/FilterCombos.h`
282 /// for description of "combo iterator".
283 class CandidateEnvMerger {
284 /// Current list of merged candidates
285 std::vector< DeferRef > crnt;
286 /// Stack of environments to support backtracking
287 std::vector< ast::TypeEnvironment > envs;
288 /// Stack of open variables to support backtracking
289 std::vector< ast::OpenVarSet > opens;
290 /// Symbol table to use for merges
291 const ast::SymbolTable & symtab;
292
293 public:
294 /// The merged environment/open variables and the list of candidates
295 struct OutType {
296 ast::TypeEnvironment env;
297 ast::OpenVarSet open;
298 std::vector< DeferRef > assns;
299 Cost cost;
300
301 OutType(
302 const ast::TypeEnvironment & e, const ast::OpenVarSet & o,
303 const std::vector< DeferRef > & as, const ast::SymbolTable & symtab )
304 : env( e ), open( o ), assns( as ), cost( Cost::zero ) {
305 // compute combined conversion cost
306 for ( const DeferRef & assn : assns ) {
307 // compute conversion cost from satisfying decl to assertion
308 cost += computeConversionCost(
309 assn.match.adjType, assn.decl->get_type(), symtab, env );
310
311 // mark vars+specialization on function-type assertions
312 const ast::FunctionType * func =
313 GenPoly::getFunctionType( assn.match.cdata.id->get_type() );
314 if ( ! func ) continue;
315
316 for ( const ast::DeclWithType * param : func->params ) {
317 cost.decSpec( specCost( param->get_type() ) );
318 }
319
320 cost.incVar( func->forall.size() );
321
322 for ( const ast::TypeDecl * td : func->forall ) {
323 cost.decSpec( td->assertions.size() );
324 }
325 }
326 }
327
328 bool operator< ( const OutType & o ) const { return cost < o.cost; }
329 };
330
331 CandidateEnvMerger(
332 const ast::TypeEnvironment & env, const ast::OpenVarSet & open,
333 const ast::SymbolTable & syms )
334 : crnt(), envs{ env }, opens{ open }, symtab( syms ) {}
335
336 bool append( DeferRef i ) {
337 ast::TypeEnvironment env = envs.back();
338 ast::OpenVarSet open = opens.back();
339 mergeOpenVars( open, i.match.open );
340
341 if ( ! env.combine( i.match.env, open, symtab ) ) return false;
342
343 crnt.emplace_back( i );
344 envs.emplace_back( std::move( env ) );
345 opens.emplace_back( std::move( open ) );
346 return true;
347 }
348
349 void backtrack() {
350 crnt.pop_back();
351 envs.pop_back();
352 opens.pop_back();
353 }
354
355 OutType finalize() { return { envs.back(), opens.back(), crnt, symtab }; }
356 };
357
358 /// Limit to depth of recursion of assertion satisfaction
359 static const int recursionLimit = 4;
360 /// Maximum number of simultaneously-deferred assertions to attempt concurrent satisfaction of
361 static const int deferLimit = 10;
362} // anonymous namespace
363
364void satisfyAssertions(
365 CandidateRef & cand, const ast::SymbolTable & symtab, CandidateList & out,
366 std::vector<std::string> & errors
367) {
368 // finish early if no assertions to satisfy
369 if ( cand->need.empty() ) {
370 out.emplace_back( cand );
371 return;
372 }
373
374 // build list of possible combinations of satisfying declarations
375 std::vector< SatState > sats{ SatState{ cand, symtab } };
376 std::vector< SatState > nextSats{};
377
378 // pruning thresholds by result type of output candidates.
379 // Candidates *should* be generated in sorted order, so no need to retroactively prune
380 PruneMap thresholds;
381
382 // satisfy assertions in breadth-first order over the recursion tree of assertion satisfaction.
383 // Stop recursion at a limited number of levels deep to avoid infinite loops.
384 for ( unsigned level = 0; level < recursionLimit; ++level ) {
385 // for each current mutually-compatible set of assertions
386 for ( SatState & sat : sats ) {
387 // stop this branch if a better option is already found
388 auto it = thresholds.find( pruneKey( *sat.cand ) );
389 if ( it != thresholds.end() && it->second < sat.costs ) goto nextSat;
390
391 // make initial pass at matching assertions
392 for ( auto & assn : sat.need ) {
393 // fail early if any assertion is not satisfiable
394 if ( ! satisfyAssertion( assn, sat ) ) {
395 Indenter tabs{ 3 };
396 std::ostringstream ss;
397 ss << tabs << "Unsatisfiable alternative:\n";
398 print( ss, *sat.cand, ++tabs );
399 ss << (tabs-1) << "Could not satisfy assertion:\n";
400 ast::print( ss, assn.first, tabs );
401
402 errors.emplace_back( ss.str() );
403 goto nextSat;
404 }
405 }
406
407 if ( sat.deferred.empty() ) {
408 // either add successful match or push back next state
409 if ( sat.newNeed.empty() ) {
410 finalizeAssertions(
411 sat.cand, sat.inferred, thresholds, std::move( sat.costs ), out );
412 } else {
413 nextSats.emplace_back( std::move( sat ), IterateState );
414 }
415 } else if ( sat.deferred.size() > deferLimit ) {
416 // too many deferred assertions to attempt mutual compatibility
417 Indenter tabs{ 3 };
418 std::ostringstream ss;
419 ss << tabs << "Unsatisfiable alternative:\n";
420 print( ss, *sat.cand, ++tabs );
421 ss << (tabs-1) << "Too many non-unique satisfying assignments for assertions:\n";
422 for ( const auto & d : sat.deferred ) {
423 ast::print( ss, d.decl, tabs );
424 }
425
426 errors.emplace_back( ss.str() );
427 goto nextSat;
428 } else {
429 // combine deferred assertions by mutual compatibility
430 std::vector< CandidateEnvMerger::OutType > compatible = filterCombos(
431 sat.deferred, CandidateEnvMerger{ sat.cand->env, sat.cand->open, sat.symtab } );
432
433 // fail early if no mutually-compatible assertion satisfaction
434 if ( compatible.empty() ) {
435 Indenter tabs{ 3 };
436 std::ostringstream ss;
437 ss << tabs << "Unsatisfiable alternative:\n";
438 print( ss, *sat.cand, ++tabs );
439 ss << (tabs-1) << "No mutually-compatible satisfaction for assertions:\n";
440 for ( const auto& d : sat.deferred ) {
441 ast::print( ss, d.decl, tabs );
442 }
443
444 errors.emplace_back( ss.str() );
445 goto nextSat;
446 }
447
448 // sort by cost (for overall pruning order)
449 std::sort( compatible.begin(), compatible.end() );
450
451 // process mutually-compatible combinations
452 for ( auto & compat : compatible ) {
453 // set up next satisfaction state
454 CandidateRef nextCand = std::make_shared<Candidate>(
455 sat.cand->expr, std::move( compat.env ), std::move( compat.open ),
456 ast::AssertionSet{} /* need moved into satisfaction state */,
457 sat.cand->cost, sat.cand->cvtCost );
458
459 ast::AssertionSet nextNewNeed{ sat.newNeed };
460 InferCache nextInferred{ sat.inferred };
461
462 CostVec nextCosts{ sat.costs };
463 nextCosts.back() += compat.cost;
464
465 ast::SymbolTable nextSymtab{ sat.symtab };
466
467 // add compatible assertions to new satisfaction state
468 for ( DeferRef r : compat.assns ) {
469 AssnCandidate match = r.match;
470 addToSymbolTable( match.have, nextSymtab );
471 nextNewNeed.insert( match.need.begin(), match.need.end() );
472
473 bindAssertion( r.decl, r.info, nextCand, match, nextInferred );
474 }
475
476 // either add successful match or push back next state
477 if ( nextNewNeed.empty() ) {
478 finalizeAssertions(
479 nextCand, nextInferred, thresholds, std::move( nextCosts ), out );
480 } else {
481 nextSats.emplace_back(
482 std::move( nextCand ), std::move( nextNewNeed ),
483 std::move( nextInferred ), std::move( nextCosts ),
484 std::move( nextSymtab ) );
485 }
486 }
487 }
488 nextSat:; }
489
490 // finish or reset for next round
491 if ( nextSats.empty() ) return;
492 sats.swap( nextSats );
493 nextSats.clear();
494 }
495
496 // exceeded recursion limit if reaches here
497 if ( out.empty() ) {
498 SemanticError( cand->expr->location, "Too many recursive assertions" );
499 }
500}
501
502} // namespace ResolvExpr
503
504// Local Variables: //
505// tab-width: 4 //
506// mode: c++ //
507// compile-command: "make install" //
508// End: //
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