source: src/ResolvExpr/CandidateFinder.cpp@ 2890212

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation new-ast new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 2890212 was 2890212, checked in by Thierry Delisle <tdelisle@…>, 6 years ago

Startup.cfa now compiles with new ast
  • Property mode set to 100644
File size: 59.1 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// CandidateFinder.cpp --
8//
9// Author : Aaron B. Moss
10// Created On : Wed Jun 5 14:30:00 2019
11// Last Modified By : Aaron B. Moss
12// Last Modified On : Wed Jun 5 14:30:00 2019
13// Update Count : 1
14//
15
16#include "CandidateFinder.hpp"
17
18#include <deque>
19#include <iterator> // for back_inserter
20#include <sstream>
21#include <string>
22#include <unordered_map>
23#include <vector>
24
25#include "Candidate.hpp"
26#include "CompilationState.h"
27#include "Cost.h"
28#include "ExplodedArg.hpp"
29#include "RenameVars.h" // for renameTyVars
30#include "Resolver.h"
31#include "ResolveTypeof.h"
32#include "SatisfyAssertions.hpp"
33#include "typeops.h" // for adjustExprType, conversionCost, polyCost, specCost
34#include "Unify.h"
35#include "AST/Expr.hpp"
36#include "AST/Node.hpp"
37#include "AST/Pass.hpp"
38#include "AST/Print.hpp"
39#include "AST/SymbolTable.hpp"
40#include "AST/Type.hpp"
41#include "Common/utility.h" // for move, copy
42#include "SymTab/Mangler.h"
43#include "SymTab/Validate.h" // for validateType
44#include "Tuples/Tuples.h" // for handleTupleAssignment
45
46#define PRINT( text ) if ( resolvep ) { text }
47
48namespace ResolvExpr {
49
50const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
51 if ( expr->result.as< ast::ReferenceType >() ) {
52 // cast away reference from expr
53 cost.incReference();
54 return new ast::CastExpr{ expr, expr->result->stripReferences() };
55 }
56
57 return expr;
58}
59
60/// Unique identifier for matching expression resolutions to their requesting expression
61UniqueId globalResnSlot = 0;
62
63Cost computeConversionCost(
64 const ast::Type * argType, const ast::Type * paramType, const ast::SymbolTable & symtab,
65 const ast::TypeEnvironment & env
66) {
67 PRINT(
68 std::cerr << std::endl << "converting ";
69 ast::print( std::cerr, argType, 2 );
70 std::cerr << std::endl << " to ";
71 ast::print( std::cerr, paramType, 2 );
72 std::cerr << std::endl << "environment is: ";
73 ast::print( std::cerr, env, 2 );
74 std::cerr << std::endl;
75 )
76 Cost convCost = conversionCost( argType, paramType, symtab, env );
77 PRINT(
78 std::cerr << std::endl << "cost is " << convCost << std::endl;
79 )
80 if ( convCost == Cost::infinity ) return convCost;
81 convCost.incPoly( polyCost( paramType, symtab, env ) + polyCost( argType, symtab, env ) );
82 PRINT(
83 std::cerr << "cost with polycost is " << convCost << std::endl;
84 )
85 return convCost;
86}
87
88namespace {
89 /// First index is which argument, second is which alternative, third is which exploded element
90 using ExplodedArgs_new = std::deque< std::vector< ExplodedArg > >;
91
92 /// Returns a list of alternatives with the minimum cost in the given list
93 CandidateList findMinCost( const CandidateList & candidates ) {
94 CandidateList out;
95 Cost minCost = Cost::infinity;
96 for ( const CandidateRef & r : candidates ) {
97 if ( r->cost < minCost ) {
98 minCost = r->cost;
99 out.clear();
100 out.emplace_back( r );
101 } else if ( r->cost == minCost ) {
102 out.emplace_back( r );
103 }
104 }
105 return out;
106 }
107
108 /// Computes conversion cost for a given expression to a given type
109 const ast::Expr * computeExpressionConversionCost(
110 const ast::Expr * arg, const ast::Type * paramType, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env, Cost & outCost
111 ) {
112 Cost convCost = computeConversionCost( arg->result, paramType, symtab, env );
113 outCost += convCost;
114
115 // If there is a non-zero conversion cost, ignoring poly cost, then the expression requires
116 // conversion. Ignore poly cost for now, since this requires resolution of the cast to
117 // infer parameters and this does not currently work for the reason stated below
118 Cost tmpCost = convCost;
119 tmpCost.incPoly( -tmpCost.get_polyCost() );
120 if ( tmpCost != Cost::zero ) {
121 ast::ptr< ast::Type > newType = paramType;
122 env.apply( newType );
123 return new ast::CastExpr{ arg, newType };
124
125 // xxx - *should* be able to resolve this cast, but at the moment pointers are not
126 // castable to zero_t, but are implicitly convertible. This is clearly inconsistent,
127 // once this is fixed it should be possible to resolve the cast.
128 // xxx - this isn't working, it appears because type1 (parameter) is seen as widenable,
129 // but it shouldn't be because this makes the conversion from DT* to DT* since
130 // commontype(zero_t, DT*) is DT*, rather than nothing
131
132 // CandidateFinder finder{ symtab, env };
133 // finder.find( arg, ResolvMode::withAdjustment() );
134 // assertf( finder.candidates.size() > 0,
135 // "Somehow castable expression failed to find alternatives." );
136 // assertf( finder.candidates.size() == 1,
137 // "Somehow got multiple alternatives for known cast expression." );
138 // return finder.candidates.front()->expr;
139 }
140
141 return arg;
142 }
143
144 /// Computes conversion cost for a given candidate
145 Cost computeApplicationConversionCost(
146 CandidateRef cand, const ast::SymbolTable & symtab
147 ) {
148 auto appExpr = cand->expr.strict_as< ast::ApplicationExpr >();
149 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
150 auto function = pointer->base.strict_as< ast::FunctionType >();
151
152 Cost convCost = Cost::zero;
153 const auto & params = function->params;
154 auto param = params.begin();
155 auto & args = appExpr->args;
156
157 for ( unsigned i = 0; i < args.size(); ++i ) {
158 const ast::Type * argType = args[i]->result;
159 PRINT(
160 std::cerr << "arg expression:" << std::endl;
161 ast::print( std::cerr, args[i], 2 );
162 std::cerr << "--- results are" << std::endl;
163 ast::print( std::cerr, argType, 2 );
164 )
165
166 if ( param == params.end() ) {
167 if ( function->isVarArgs ) {
168 convCost.incUnsafe();
169 PRINT( std::cerr << "end of params with varargs function: inc unsafe: "
170 << convCost << std::endl; ; )
171 // convert reference-typed expressions into value-typed expressions
172 cand->expr = ast::mutate_field_index(
173 appExpr, &ast::ApplicationExpr::args, i,
174 referenceToRvalueConversion( args[i], convCost ) );
175 continue;
176 } else return Cost::infinity;
177 }
178
179 if ( auto def = args[i].as< ast::DefaultArgExpr >() ) {
180 // Default arguments should be free - don't include conversion cost.
181 // Unwrap them here because they are not relevant to the rest of the system
182 cand->expr = ast::mutate_field_index(
183 appExpr, &ast::ApplicationExpr::args, i, def->expr );
184 ++param;
185 continue;
186 }
187
188 // mark conversion cost and also specialization cost of param type
189 const ast::Type * paramType = (*param)->get_type();
190 cand->expr = ast::mutate_field_index(
191 appExpr, &ast::ApplicationExpr::args, i,
192 computeExpressionConversionCost(
193 args[i], paramType, symtab, cand->env, convCost ) );
194 convCost.decSpec( specCost( paramType ) );
195 ++param; // can't be in for-loop update because of the continue
196 }
197
198 if ( param != params.end() ) return Cost::infinity;
199
200 // specialization cost of return types can't be accounted for directly, it disables
201 // otherwise-identical calls, like this example based on auto-newline in the I/O lib:
202 //
203 // forall(otype OS) {
204 // void ?|?(OS&, int); // with newline
205 // OS& ?|?(OS&, int); // no newline, always chosen due to more specialization
206 // }
207
208 // mark type variable and specialization cost of forall clause
209 convCost.incVar( function->forall.size() );
210 for ( const ast::TypeDecl * td : function->forall ) {
211 convCost.decSpec( td->assertions.size() );
212 }
213
214 return convCost;
215 }
216
217 void makeUnifiableVars(
218 const ast::ParameterizedType * type, ast::OpenVarSet & unifiableVars,
219 ast::AssertionSet & need
220 ) {
221 for ( const ast::TypeDecl * tyvar : type->forall ) {
222 unifiableVars[ tyvar->name ] = ast::TypeDecl::Data{ tyvar };
223 for ( const ast::DeclWithType * assn : tyvar->assertions ) {
224 need[ assn ].isUsed = true;
225 }
226 }
227 }
228
229 /// Gets a default value from an initializer, nullptr if not present
230 const ast::ConstantExpr * getDefaultValue( const ast::Init * init ) {
231 if ( auto si = dynamic_cast< const ast::SingleInit * >( init ) ) {
232 if ( auto ce = si->value.as< ast::CastExpr >() ) {
233 return ce->arg.as< ast::ConstantExpr >();
234 } else {
235 return si->value.as< ast::ConstantExpr >();
236 }
237 }
238 return nullptr;
239 }
240
241 /// State to iteratively build a match of parameter expressions to arguments
242 struct ArgPack {
243 std::size_t parent; ///< Index of parent pack
244 ast::ptr< ast::Expr > expr; ///< The argument stored here
245 Cost cost; ///< The cost of this argument
246 ast::TypeEnvironment env; ///< Environment for this pack
247 ast::AssertionSet need; ///< Assertions outstanding for this pack
248 ast::AssertionSet have; ///< Assertions found for this pack
249 ast::OpenVarSet open; ///< Open variables for this pack
250 unsigned nextArg; ///< Index of next argument in arguments list
251 unsigned tupleStart; ///< Number of tuples that start at this index
252 unsigned nextExpl; ///< Index of next exploded element
253 unsigned explAlt; ///< Index of alternative for nextExpl > 0
254
255 ArgPack()
256 : parent( 0 ), expr(), cost( Cost::zero ), env(), need(), have(), open(), nextArg( 0 ),
257 tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
258
259 ArgPack(
260 const ast::TypeEnvironment & env, const ast::AssertionSet & need,
261 const ast::AssertionSet & have, const ast::OpenVarSet & open )
262 : parent( 0 ), expr(), cost( Cost::zero ), env( env ), need( need ), have( have ),
263 open( open ), nextArg( 0 ), tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
264
265 ArgPack(
266 std::size_t parent, const ast::Expr * expr, ast::TypeEnvironment && env,
267 ast::AssertionSet && need, ast::AssertionSet && have, ast::OpenVarSet && open,
268 unsigned nextArg, unsigned tupleStart = 0, Cost cost = Cost::zero,
269 unsigned nextExpl = 0, unsigned explAlt = 0 )
270 : parent(parent), expr( expr ), cost( cost ), env( move( env ) ), need( move( need ) ),
271 have( move( have ) ), open( move( open ) ), nextArg( nextArg ), tupleStart( tupleStart ),
272 nextExpl( nextExpl ), explAlt( explAlt ) {}
273
274 ArgPack(
275 const ArgPack & o, ast::TypeEnvironment && env, ast::AssertionSet && need,
276 ast::AssertionSet && have, ast::OpenVarSet && open, unsigned nextArg, Cost added )
277 : parent( o.parent ), expr( o.expr ), cost( o.cost + added ), env( move( env ) ),
278 need( move( need ) ), have( move( have ) ), open( move( open ) ), nextArg( nextArg ),
279 tupleStart( o.tupleStart ), nextExpl( 0 ), explAlt( 0 ) {}
280
281 /// true if this pack is in the middle of an exploded argument
282 bool hasExpl() const { return nextExpl > 0; }
283
284 /// Gets the list of exploded candidates for this pack
285 const ExplodedArg & getExpl( const ExplodedArgs_new & args ) const {
286 return args[ nextArg-1 ][ explAlt ];
287 }
288
289 /// Ends a tuple expression, consolidating the appropriate args
290 void endTuple( const std::vector< ArgPack > & packs ) {
291 // add all expressions in tuple to list, summing cost
292 std::deque< const ast::Expr * > exprs;
293 const ArgPack * pack = this;
294 if ( expr ) { exprs.emplace_front( expr ); }
295 while ( pack->tupleStart == 0 ) {
296 pack = &packs[pack->parent];
297 exprs.emplace_front( pack->expr );
298 cost += pack->cost;
299 }
300 // reset pack to appropriate tuple
301 std::vector< ast::ptr< ast::Expr > > exprv( exprs.begin(), exprs.end() );
302 expr = new ast::TupleExpr{ expr->location, move( exprv ) };
303 tupleStart = pack->tupleStart - 1;
304 parent = pack->parent;
305 }
306 };
307
308 /// Instantiates an argument to match a parameter, returns false if no matching results left
309 bool instantiateArgument(
310 const ast::Type * paramType, const ast::Init * init, const ExplodedArgs_new & args,
311 std::vector< ArgPack > & results, std::size_t & genStart, const ast::SymbolTable & symtab,
312 unsigned nTuples = 0
313 ) {
314 if ( auto tupleType = dynamic_cast< const ast::TupleType * >( paramType ) ) {
315 // paramType is a TupleType -- group args into a TupleExpr
316 ++nTuples;
317 for ( const ast::Type * type : *tupleType ) {
318 // xxx - dropping initializer changes behaviour from previous, but seems correct
319 // ^^^ need to handle the case where a tuple has a default argument
320 if ( ! instantiateArgument(
321 type, nullptr, args, results, genStart, symtab, nTuples ) ) return false;
322 nTuples = 0;
323 }
324 // re-constitute tuples for final generation
325 for ( auto i = genStart; i < results.size(); ++i ) {
326 results[i].endTuple( results );
327 }
328 return true;
329 } else if ( const ast::TypeInstType * ttype = Tuples::isTtype( paramType ) ) {
330 // paramType is a ttype, consumes all remaining arguments
331
332 // completed tuples; will be spliced to end of results to finish
333 std::vector< ArgPack > finalResults{};
334
335 // iterate until all results completed
336 std::size_t genEnd;
337 ++nTuples;
338 do {
339 genEnd = results.size();
340
341 // add another argument to results
342 for ( std::size_t i = genStart; i < genEnd; ++i ) {
343 unsigned nextArg = results[i].nextArg;
344
345 // use next element of exploded tuple if present
346 if ( results[i].hasExpl() ) {
347 const ExplodedArg & expl = results[i].getExpl( args );
348
349 unsigned nextExpl = results[i].nextExpl + 1;
350 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
351
352 results.emplace_back(
353 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
354 copy( results[i].need ), copy( results[i].have ),
355 copy( results[i].open ), nextArg, nTuples, Cost::zero, nextExpl,
356 results[i].explAlt );
357
358 continue;
359 }
360
361 // finish result when out of arguments
362 if ( nextArg >= args.size() ) {
363 ArgPack newResult{
364 results[i].env, results[i].need, results[i].have, results[i].open };
365 newResult.nextArg = nextArg;
366 const ast::Type * argType = nullptr;
367
368 if ( nTuples > 0 || ! results[i].expr ) {
369 // first iteration or no expression to clone,
370 // push empty tuple expression
371 newResult.parent = i;
372 newResult.expr = new ast::TupleExpr{ CodeLocation{}, {} };
373 argType = newResult.expr->result;
374 } else {
375 // clone result to collect tuple
376 newResult.parent = results[i].parent;
377 newResult.cost = results[i].cost;
378 newResult.tupleStart = results[i].tupleStart;
379 newResult.expr = results[i].expr;
380 argType = newResult.expr->result;
381
382 if ( results[i].tupleStart > 0 && Tuples::isTtype( argType ) ) {
383 // the case where a ttype value is passed directly is special,
384 // e.g. for argument forwarding purposes
385 // xxx - what if passing multiple arguments, last of which is
386 // ttype?
387 // xxx - what would happen if unify was changed so that unifying
388 // tuple
389 // types flattened both before unifying lists? then pass in
390 // TupleType (ttype) below.
391 --newResult.tupleStart;
392 } else {
393 // collapse leftover arguments into tuple
394 newResult.endTuple( results );
395 argType = newResult.expr->result;
396 }
397 }
398
399 // check unification for ttype before adding to final
400 if (
401 unify(
402 ttype, argType, newResult.env, newResult.need, newResult.have,
403 newResult.open, symtab )
404 ) {
405 finalResults.emplace_back( move( newResult ) );
406 }
407
408 continue;
409 }
410
411 // add each possible next argument
412 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
413 const ExplodedArg & expl = args[nextArg][j];
414
415 // fresh copies of parent parameters for this iteration
416 ast::TypeEnvironment env = results[i].env;
417 ast::OpenVarSet open = results[i].open;
418
419 env.addActual( expl.env, open );
420
421 // skip empty tuple arguments by (nearly) cloning parent into next gen
422 if ( expl.exprs.empty() ) {
423 results.emplace_back(
424 results[i], move( env ), copy( results[i].need ),
425 copy( results[i].have ), move( open ), nextArg + 1, expl.cost );
426
427 continue;
428 }
429
430 // add new result
431 results.emplace_back(
432 i, expl.exprs.front(), move( env ), copy( results[i].need ),
433 copy( results[i].have ), move( open ), nextArg + 1, nTuples,
434 expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
435 }
436 }
437
438 // reset for next round
439 genStart = genEnd;
440 nTuples = 0;
441 } while ( genEnd != results.size() );
442
443 // splice final results onto results
444 for ( std::size_t i = 0; i < finalResults.size(); ++i ) {
445 results.emplace_back( move( finalResults[i] ) );
446 }
447 return ! finalResults.empty();
448 }
449
450 // iterate each current subresult
451 std::size_t genEnd = results.size();
452 for ( std::size_t i = genStart; i < genEnd; ++i ) {
453 unsigned nextArg = results[i].nextArg;
454
455 // use remainder of exploded tuple if present
456 if ( results[i].hasExpl() ) {
457 const ExplodedArg & expl = results[i].getExpl( args );
458 const ast::Expr * expr = expl.exprs[ results[i].nextExpl ];
459
460 ast::TypeEnvironment env = results[i].env;
461 ast::AssertionSet need = results[i].need, have = results[i].have;
462 ast::OpenVarSet open = results[i].open;
463
464 const ast::Type * argType = expr->result;
465
466 PRINT(
467 std::cerr << "param type is ";
468 ast::print( std::cerr, paramType );
469 std::cerr << std::endl << "arg type is ";
470 ast::print( std::cerr, argType );
471 std::cerr << std::endl;
472 )
473
474 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
475 unsigned nextExpl = results[i].nextExpl + 1;
476 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
477
478 results.emplace_back(
479 i, expr, move( env ), move( need ), move( have ), move( open ), nextArg,
480 nTuples, Cost::zero, nextExpl, results[i].explAlt );
481 }
482
483 continue;
484 }
485
486 // use default initializers if out of arguments
487 if ( nextArg >= args.size() ) {
488 if ( const ast::ConstantExpr * cnst = getDefaultValue( init ) ) {
489 ast::TypeEnvironment env = results[i].env;
490 ast::AssertionSet need = results[i].need, have = results[i].have;
491 ast::OpenVarSet open = results[i].open;
492
493 if ( unify( paramType, cnst->result, env, need, have, open, symtab ) ) {
494 results.emplace_back(
495 i, new ast::DefaultArgExpr{ cnst->location, cnst }, move( env ),
496 move( need ), move( have ), move( open ), nextArg, nTuples );
497 }
498 }
499
500 continue;
501 }
502
503 // Check each possible next argument
504 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
505 const ExplodedArg & expl = args[nextArg][j];
506
507 // fresh copies of parent parameters for this iteration
508 ast::TypeEnvironment env = results[i].env;
509 ast::AssertionSet need = results[i].need, have = results[i].have;
510 ast::OpenVarSet open = results[i].open;
511
512 env.addActual( expl.env, open );
513
514 // skip empty tuple arguments by (nearly) cloning parent into next gen
515 if ( expl.exprs.empty() ) {
516 results.emplace_back(
517 results[i], move( env ), move( need ), move( have ), move( open ),
518 nextArg + 1, expl.cost );
519
520 continue;
521 }
522
523 // consider only first exploded arg
524 const ast::Expr * expr = expl.exprs.front();
525 const ast::Type * argType = expr->result;
526
527 PRINT(
528 std::cerr << "param type is ";
529 ast::print( std::cerr, paramType );
530 std::cerr << std::endl << "arg type is ";
531 ast::print( std::cerr, argType );
532 std::cerr << std::endl;
533 )
534
535 // attempt to unify types
536 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
537 // add new result
538 results.emplace_back(
539 i, expr, move( env ), move( need ), move( have ), move( open ),
540 nextArg + 1, nTuples, expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
541 }
542 }
543 }
544
545 // reset for next parameter
546 genStart = genEnd;
547
548 return genEnd != results.size(); // were any new results added?
549 }
550
551 /// Generate a cast expression from `arg` to `toType`
552 const ast::Expr * restructureCast(
553 ast::ptr< ast::Expr > & arg, const ast::Type * toType, ast::GeneratedFlag isGenerated = ast::GeneratedCast
554 ) {
555 if (
556 arg->result->size() > 1
557 && ! toType->isVoid()
558 && ! dynamic_cast< const ast::ReferenceType * >( toType )
559 ) {
560 // Argument is a tuple and the target type is neither void nor a reference. Cast each
561 // member of the tuple to its corresponding target type, producing the tuple of those
562 // cast expressions. If there are more components of the tuple than components in the
563 // target type, then excess components do not come out in the result expression (but
564 // UniqueExpr ensures that the side effects will still be produced)
565 if ( Tuples::maybeImpureIgnoreUnique( arg ) ) {
566 // expressions which may contain side effects require a single unique instance of
567 // the expression
568 arg = new ast::UniqueExpr{ arg->location, arg };
569 }
570 std::vector< ast::ptr< ast::Expr > > components;
571 for ( unsigned i = 0; i < toType->size(); ++i ) {
572 // cast each component
573 ast::ptr< ast::Expr > idx = new ast::TupleIndexExpr{ arg->location, arg, i };
574 components.emplace_back(
575 restructureCast( idx, toType->getComponent( i ), isGenerated ) );
576 }
577 return new ast::TupleExpr{ arg->location, move( components ) };
578 } else {
579 // handle normally
580 return new ast::CastExpr{ arg->location, arg, toType, isGenerated };
581 }
582 }
583
584 /// Gets the name from an untyped member expression (must be NameExpr)
585 const std::string & getMemberName( const ast::UntypedMemberExpr * memberExpr ) {
586 if ( memberExpr->member.as< ast::ConstantExpr >() ) {
587 SemanticError( memberExpr, "Indexed access to struct fields unsupported: " );
588 }
589
590 return memberExpr->member.strict_as< ast::NameExpr >()->name;
591 }
592
593 /// Actually visits expressions to find their candidate interpretations
594 class Finder final : public ast::WithShortCircuiting {
595 const ast::SymbolTable & symtab;
596 public:
597 CandidateFinder & selfFinder;
598 CandidateList & candidates;
599 const ast::TypeEnvironment & tenv;
600 ast::ptr< ast::Type > & targetType;
601
602 Finder( CandidateFinder & f )
603 : symtab( f.localSyms ), selfFinder( f ), candidates( f.candidates ), tenv( f.env ),
604 targetType( f.targetType ) {}
605
606 void previsit( const ast::Node * ) { visit_children = false; }
607
608 /// Convenience to add candidate to list
609 template<typename... Args>
610 void addCandidate( Args &&... args ) {
611 candidates.emplace_back( new Candidate{ std::forward<Args>( args )... } );
612 }
613
614 void postvisit( const ast::ApplicationExpr * applicationExpr ) {
615 addCandidate( applicationExpr, tenv );
616 }
617
618 /// Set up candidate assertions for inference
619 void inferParameters( CandidateRef & newCand, CandidateList & out ) {
620 // Set need bindings for any unbound assertions
621 UniqueId crntResnSlot = 0; // matching ID for this expression's assertions
622 for ( auto & assn : newCand->need ) {
623 // skip already-matched assertions
624 if ( assn.second.resnSlot != 0 ) continue;
625 // assign slot for expression if needed
626 if ( crntResnSlot == 0 ) { crntResnSlot = ++globalResnSlot; }
627 // fix slot to assertion
628 assn.second.resnSlot = crntResnSlot;
629 }
630 // pair slot to expression
631 if ( crntResnSlot != 0 ) {
632 newCand->expr.get_and_mutate()->inferred.resnSlots().emplace_back( crntResnSlot );
633 }
634
635 // add to output list; assertion satisfaction will occur later
636 out.emplace_back( newCand );
637 }
638
639 /// Completes a function candidate with arguments located
640 void validateFunctionCandidate(
641 const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results,
642 CandidateList & out
643 ) {
644 ast::ApplicationExpr * appExpr =
645 new ast::ApplicationExpr{ func->expr->location, func->expr };
646 // sum cost and accumulate arguments
647 std::deque< const ast::Expr * > args;
648 Cost cost = func->cost;
649 const ArgPack * pack = &result;
650 while ( pack->expr ) {
651 args.emplace_front( pack->expr );
652 cost += pack->cost;
653 pack = &results[pack->parent];
654 }
655 std::vector< ast::ptr< ast::Expr > > vargs( args.begin(), args.end() );
656 appExpr->args = move( vargs );
657 // build and validate new candidate
658 auto newCand =
659 std::make_shared<Candidate>( appExpr, result.env, result.open, result.need, cost );
660 PRINT(
661 std::cerr << "instantiate function success: " << appExpr << std::endl;
662 std::cerr << "need assertions:" << std::endl;
663 ast::print( std::cerr, result.need, 2 );
664 )
665 inferParameters( newCand, out );
666 }
667
668 /// Builds a list of candidates for a function, storing them in out
669 void makeFunctionCandidates(
670 const CandidateRef & func, const ast::FunctionType * funcType,
671 const ExplodedArgs_new & args, CandidateList & out
672 ) {
673 ast::OpenVarSet funcOpen;
674 ast::AssertionSet funcNeed, funcHave;
675 ast::TypeEnvironment funcEnv{ func->env };
676 makeUnifiableVars( funcType, funcOpen, funcNeed );
677 // add all type variables as open variables now so that those not used in the
678 // parameter list are still considered open
679 funcEnv.add( funcType->forall );
680
681 if ( targetType && ! targetType->isVoid() && ! funcType->returns.empty() ) {
682 // attempt to narrow based on expected target type
683 const ast::Type * returnType = funcType->returns.front()->get_type();
684 if ( ! unify(
685 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, symtab )
686 ) {
687 // unification failed, do not pursue this candidate
688 return;
689 }
690 }
691
692 // iteratively build matches, one parameter at a time
693 std::vector< ArgPack > results;
694 results.emplace_back( funcEnv, funcNeed, funcHave, funcOpen );
695 std::size_t genStart = 0;
696
697 for ( const ast::DeclWithType * param : funcType->params ) {
698 auto obj = strict_dynamic_cast< const ast::ObjectDecl * >( param );
699 // Try adding the arguments corresponding to the current parameter to the existing
700 // matches
701 if ( ! instantiateArgument(
702 obj->type, obj->init, args, results, genStart, symtab ) ) return;
703 }
704
705 if ( funcType->isVarArgs ) {
706 // append any unused arguments to vararg pack
707 std::size_t genEnd;
708 do {
709 genEnd = results.size();
710
711 // iterate results
712 for ( std::size_t i = genStart; i < genEnd; ++i ) {
713 unsigned nextArg = results[i].nextArg;
714
715 // use remainder of exploded tuple if present
716 if ( results[i].hasExpl() ) {
717 const ExplodedArg & expl = results[i].getExpl( args );
718
719 unsigned nextExpl = results[i].nextExpl + 1;
720 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
721
722 results.emplace_back(
723 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
724 copy( results[i].need ), copy( results[i].have ),
725 copy( results[i].open ), nextArg, 0, Cost::zero, nextExpl,
726 results[i].explAlt );
727
728 continue;
729 }
730
731 // finish result when out of arguments
732 if ( nextArg >= args.size() ) {
733 validateFunctionCandidate( func, results[i], results, out );
734
735 continue;
736 }
737
738 // add each possible next argument
739 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
740 const ExplodedArg & expl = args[nextArg][j];
741
742 // fresh copies of parent parameters for this iteration
743 ast::TypeEnvironment env = results[i].env;
744 ast::OpenVarSet open = results[i].open;
745
746 env.addActual( expl.env, open );
747
748 // skip empty tuple arguments by (nearly) cloning parent into next gen
749 if ( expl.exprs.empty() ) {
750 results.emplace_back(
751 results[i], move( env ), copy( results[i].need ),
752 copy( results[i].have ), move( open ), nextArg + 1,
753 expl.cost );
754
755 continue;
756 }
757
758 // add new result
759 results.emplace_back(
760 i, expl.exprs.front(), move( env ), copy( results[i].need ),
761 copy( results[i].have ), move( open ), nextArg + 1, 0, expl.cost,
762 expl.exprs.size() == 1 ? 0 : 1, j );
763 }
764 }
765
766 genStart = genEnd;
767 } while( genEnd != results.size() );
768 } else {
769 // filter out the results that don't use all the arguments
770 for ( std::size_t i = genStart; i < results.size(); ++i ) {
771 ArgPack & result = results[i];
772 if ( ! result.hasExpl() && result.nextArg >= args.size() ) {
773 validateFunctionCandidate( func, result, results, out );
774 }
775 }
776 }
777 }
778
779 /// Adds implicit struct-conversions to the alternative list
780 void addAnonConversions( const CandidateRef & cand ) {
781 // adds anonymous member interpretations whenever an aggregate value type is seen.
782 // it's okay for the aggregate expression to have reference type -- cast it to the
783 // base type to treat the aggregate as the referenced value
784 ast::ptr< ast::Expr > aggrExpr( cand->expr );
785 ast::ptr< ast::Type > & aggrType = aggrExpr.get_and_mutate()->result;
786 cand->env.apply( aggrType );
787
788 if ( aggrType.as< ast::ReferenceType >() ) {
789 aggrExpr = new ast::CastExpr{ aggrExpr, aggrType->stripReferences() };
790 }
791
792 if ( auto structInst = aggrExpr->result.as< ast::StructInstType >() ) {
793 addAggMembers( structInst, aggrExpr, *cand, Cost::safe, "" );
794 } else if ( auto unionInst = aggrExpr->result.as< ast::UnionInstType >() ) {
795 addAggMembers( unionInst, aggrExpr, *cand, Cost::safe, "" );
796 }
797 }
798
799 /// Adds aggregate member interpretations
800 void addAggMembers(
801 const ast::ReferenceToType * aggrInst, const ast::Expr * expr,
802 const Candidate & cand, const Cost & addedCost, const std::string & name
803 ) {
804 for ( const ast::Decl * decl : aggrInst->lookup( name ) ) {
805 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( decl );
806 CandidateRef newCand = std::make_shared<Candidate>(
807 cand, new ast::MemberExpr{ expr->location, dwt, expr }, addedCost );
808 // add anonymous member interpretations whenever an aggregate value type is seen
809 // as a member expression
810 addAnonConversions( newCand );
811 candidates.emplace_back( move( newCand ) );
812 }
813 }
814
815 /// Adds tuple member interpretations
816 void addTupleMembers(
817 const ast::TupleType * tupleType, const ast::Expr * expr, const Candidate & cand,
818 const Cost & addedCost, const ast::Expr * member
819 ) {
820 if ( auto constantExpr = dynamic_cast< const ast::ConstantExpr * >( member ) ) {
821 // get the value of the constant expression as an int, must be between 0 and the
822 // length of the tuple to have meaning
823 long long val = constantExpr->intValue();
824 if ( val >= 0 && (unsigned long long)val < tupleType->size() ) {
825 addCandidate(
826 cand, new ast::TupleIndexExpr{ expr->location, expr, (unsigned)val },
827 addedCost );
828 }
829 }
830 }
831
832 void postvisit( const ast::UntypedExpr * untypedExpr ) {
833 CandidateFinder funcFinder{ symtab, tenv };
834 funcFinder.find( untypedExpr->func, ResolvMode::withAdjustment() );
835 // short-circuit if no candidates
836 if ( funcFinder.candidates.empty() ) return;
837
838 std::vector< CandidateFinder > argCandidates =
839 selfFinder.findSubExprs( untypedExpr->args );
840
841 // take care of possible tuple assignments
842 // if not tuple assignment, handled as normal function call
843 Tuples::handleTupleAssignment( selfFinder, untypedExpr, argCandidates );
844
845 // find function operators
846 ast::ptr< ast::Expr > opExpr = new ast::NameExpr{ untypedExpr->location, "?()" };
847 CandidateFinder opFinder{ symtab, tenv };
848 // okay if there aren't any function operations
849 opFinder.find( opExpr, ResolvMode::withoutFailFast() );
850 PRINT(
851 std::cerr << "known function ops:" << std::endl;
852 print( std::cerr, opFinder.candidates, 1 );
853 )
854
855 // pre-explode arguments
856 ExplodedArgs_new argExpansions;
857 for ( const CandidateFinder & args : argCandidates ) {
858 argExpansions.emplace_back();
859 auto & argE = argExpansions.back();
860 for ( const CandidateRef & arg : args ) { argE.emplace_back( *arg, symtab ); }
861 }
862
863 // Find function matches
864 CandidateList found;
865 SemanticErrorException errors;
866 for ( CandidateRef & func : funcFinder ) {
867 try {
868 PRINT(
869 std::cerr << "working on alternative:" << std::endl;
870 print( std::cerr, *func, 2 );
871 )
872
873 // check if the type is a pointer to function
874 const ast::Type * funcResult = func->expr->result->stripReferences();
875 if ( auto pointer = dynamic_cast< const ast::PointerType * >( funcResult ) ) {
876 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
877 CandidateRef newFunc{ new Candidate{ *func } };
878 newFunc->expr =
879 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
880 makeFunctionCandidates( newFunc, function, argExpansions, found );
881 }
882 } else if (
883 auto inst = dynamic_cast< const ast::TypeInstType * >( funcResult )
884 ) {
885 if ( const ast::EqvClass * clz = func->env.lookup( inst->name ) ) {
886 if ( auto function = clz->bound.as< ast::FunctionType >() ) {
887 CandidateRef newFunc{ new Candidate{ *func } };
888 newFunc->expr =
889 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
890 makeFunctionCandidates( newFunc, function, argExpansions, found );
891 }
892 }
893 }
894 } catch ( SemanticErrorException & e ) { errors.append( e ); }
895 }
896
897 // Find matches on function operators `?()`
898 if ( ! opFinder.candidates.empty() ) {
899 // add exploded function alternatives to front of argument list
900 std::vector< ExplodedArg > funcE;
901 funcE.reserve( funcFinder.candidates.size() );
902 for ( const CandidateRef & func : funcFinder ) {
903 funcE.emplace_back( *func, symtab );
904 }
905 argExpansions.emplace_front( move( funcE ) );
906
907 for ( const CandidateRef & op : opFinder ) {
908 try {
909 // check if type is pointer-to-function
910 const ast::Type * opResult = op->expr->result->stripReferences();
911 if ( auto pointer = dynamic_cast< const ast::PointerType * >( opResult ) ) {
912 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
913 CandidateRef newOp{ new Candidate{ *op} };
914 newOp->expr =
915 referenceToRvalueConversion( newOp->expr, newOp->cost );
916 makeFunctionCandidates( newOp, function, argExpansions, found );
917 }
918 }
919 } catch ( SemanticErrorException & e ) { errors.append( e ); }
920 }
921 }
922
923 // Implement SFINAE; resolution errors are only errors if there aren't any non-error
924 // candidates
925 if ( found.empty() && ! errors.isEmpty() ) { throw errors; }
926
927 // Compute conversion costs
928 for ( CandidateRef & withFunc : found ) {
929 Cost cvtCost = computeApplicationConversionCost( withFunc, symtab );
930
931 PRINT(
932 auto appExpr = withFunc->expr.strict_as< ast::ApplicationExpr >();
933 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
934 auto function = pointer->base.strict_as< ast::FunctionType >();
935
936 std::cerr << "Case +++++++++++++ " << appExpr->func << std::endl;
937 std::cerr << "parameters are:" << std::endl;
938 ast::printAll( std::cerr, function->params, 2 );
939 std::cerr << "arguments are:" << std::endl;
940 ast::printAll( std::cerr, appExpr->args, 2 );
941 std::cerr << "bindings are:" << std::endl;
942 ast::print( std::cerr, withFunc->env, 2 );
943 std::cerr << "cost is: " << withFunc->cost << std::endl;
944 std::cerr << "cost of conversion is:" << cvtCost << std::endl;
945 )
946
947 if ( cvtCost != Cost::infinity ) {
948 withFunc->cvtCost = cvtCost;
949 candidates.emplace_back( move( withFunc ) );
950 }
951 }
952 found = move( candidates );
953
954 // use a new list so that candidates are not examined by addAnonConversions twice
955 CandidateList winners = findMinCost( found );
956 promoteCvtCost( winners );
957
958 // function may return a struct/union value, in which case we need to add candidates
959 // for implicit conversions to each of the anonymous members, which must happen after
960 // `findMinCost`, since anon conversions are never the cheapest
961 for ( const CandidateRef & c : winners ) {
962 addAnonConversions( c );
963 }
964 spliceBegin( candidates, winners );
965
966 if ( candidates.empty() && targetType && ! targetType->isVoid() ) {
967 // If resolution is unsuccessful with a target type, try again without, since it
968 // will sometimes succeed when it wouldn't with a target type binding.
969 // For example:
970 // forall( otype T ) T & ?[]( T *, ptrdiff_t );
971 // const char * x = "hello world";
972 // unsigned char ch = x[0];
973 // Fails with simple return type binding (xxx -- check this!) as follows:
974 // * T is bound to unsigned char
975 // * (x: const char *) is unified with unsigned char *, which fails
976 // xxx -- fix this better
977 targetType = nullptr;
978 postvisit( untypedExpr );
979 }
980 }
981
982 /// true if expression is an lvalue
983 static bool isLvalue( const ast::Expr * x ) {
984 return x->result && ( x->result->is_lvalue() || x->result.as< ast::ReferenceType >() );
985 }
986
987 void postvisit( const ast::AddressExpr * addressExpr ) {
988 CandidateFinder finder{ symtab, tenv };
989 finder.find( addressExpr->arg );
990 for ( CandidateRef & r : finder.candidates ) {
991 if ( ! isLvalue( r->expr ) ) continue;
992 addCandidate( *r, new ast::AddressExpr{ addressExpr->location, r->expr } );
993 }
994 }
995
996 void postvisit( const ast::LabelAddressExpr * labelExpr ) {
997 addCandidate( labelExpr, tenv );
998 }
999
1000 void postvisit( const ast::CastExpr * castExpr ) {
1001 ast::ptr< ast::Type > toType = castExpr->result;
1002 assert( toType );
1003 toType = resolveTypeof( toType, symtab );
1004 toType = SymTab::validateType( castExpr->location, toType, symtab );
1005 toType = adjustExprType( toType, tenv, symtab );
1006
1007 CandidateFinder finder{ symtab, tenv, toType };
1008 finder.find( castExpr->arg, ResolvMode::withAdjustment() );
1009
1010 CandidateList matches;
1011 for ( CandidateRef & cand : finder.candidates ) {
1012 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1013 ast::OpenVarSet open( cand->open );
1014
1015 cand->env.extractOpenVars( open );
1016
1017 // It is possible that a cast can throw away some values in a multiply-valued
1018 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of the
1019 // subexpression results that are cast directly. The candidate is invalid if it
1020 // has fewer results than there are types to cast to.
1021 int discardedValues = cand->expr->result->size() - toType->size();
1022 if ( discardedValues < 0 ) continue;
1023
1024 // unification run for side-effects
1025 unify( toType, cand->expr->result, cand->env, need, have, open, symtab );
1026 Cost thisCost = castCost( cand->expr->result, toType, symtab, cand->env );
1027 PRINT(
1028 std::cerr << "working on cast with result: " << toType << std::endl;
1029 std::cerr << "and expr type: " << cand->expr->result << std::endl;
1030 std::cerr << "env: " << cand->env << std::endl;
1031 )
1032 if ( thisCost != Cost::infinity ) {
1033 PRINT(
1034 std::cerr << "has finite cost." << std::endl;
1035 )
1036 // count one safe conversion for each value that is thrown away
1037 thisCost.incSafe( discardedValues );
1038 CandidateRef newCand = std::make_shared<Candidate>(
1039 restructureCast( cand->expr, toType, castExpr->isGenerated ),
1040 copy( cand->env ), move( open ), move( need ), cand->cost,
1041 cand->cost + thisCost );
1042 inferParameters( newCand, matches );
1043 }
1044 }
1045
1046 // select first on argument cost, then conversion cost
1047 CandidateList minArgCost = findMinCost( matches );
1048 promoteCvtCost( minArgCost );
1049 candidates = findMinCost( minArgCost );
1050 }
1051
1052 void postvisit( const ast::VirtualCastExpr * castExpr ) {
1053 assertf( castExpr->result, "Implicit virtual cast targets not yet supported." );
1054 CandidateFinder finder{ symtab, tenv };
1055 // don't prune here, all alternatives guaranteed to have same type
1056 finder.find( castExpr->arg, ResolvMode::withoutPrune() );
1057 for ( CandidateRef & r : finder.candidates ) {
1058 addCandidate(
1059 *r,
1060 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
1061 }
1062 }
1063
1064 void postvisit( const ast::UntypedMemberExpr * memberExpr ) {
1065 CandidateFinder aggFinder{ symtab, tenv };
1066 aggFinder.find( memberExpr->aggregate, ResolvMode::withAdjustment() );
1067 for ( CandidateRef & agg : aggFinder.candidates ) {
1068 // it's okay for the aggregate expression to have reference type -- cast it to the
1069 // base type to treat the aggregate as the referenced value
1070 Cost addedCost = Cost::zero;
1071 agg->expr = referenceToRvalueConversion( agg->expr, addedCost );
1072
1073 // find member of the given type
1074 if ( auto structInst = agg->expr->result.as< ast::StructInstType >() ) {
1075 addAggMembers(
1076 structInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1077 } else if ( auto unionInst = agg->expr->result.as< ast::UnionInstType >() ) {
1078 addAggMembers(
1079 unionInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1080 } else if ( auto tupleType = agg->expr->result.as< ast::TupleType >() ) {
1081 addTupleMembers( tupleType, agg->expr, *agg, addedCost, memberExpr->member );
1082 }
1083 }
1084 }
1085
1086 void postvisit( const ast::MemberExpr * memberExpr ) {
1087 addCandidate( memberExpr, tenv );
1088 }
1089
1090 void postvisit( const ast::NameExpr * nameExpr ) {
1091 std::vector< ast::SymbolTable::IdData > declList = symtab.lookupId( nameExpr->name );
1092 PRINT( std::cerr << "nameExpr is " << nameExpr->name << std::endl; )
1093 for ( auto & data : declList ) {
1094 Cost cost = Cost::zero;
1095 ast::Expr * newExpr = data.combine( nameExpr->location, cost );
1096
1097 CandidateRef newCand = std::make_shared<Candidate>(
1098 newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, Cost::zero,
1099 cost );
1100 PRINT(
1101 std::cerr << "decl is ";
1102 ast::print( std::cerr, data.id );
1103 std::cerr << std::endl;
1104 std::cerr << "newExpr is ";
1105 ast::print( std::cerr, newExpr );
1106 std::cerr << std::endl;
1107 )
1108 newCand->expr = ast::mutate_field(
1109 newCand->expr.get(), &ast::Expr::result,
1110 renameTyVars( newCand->expr->result ) );
1111 // add anonymous member interpretations whenever an aggregate value type is seen
1112 // as a name expression
1113 addAnonConversions( newCand );
1114 candidates.emplace_back( move( newCand ) );
1115 }
1116 }
1117
1118 void postvisit( const ast::VariableExpr * variableExpr ) {
1119 // not sufficient to just pass `variableExpr` here, type might have changed since
1120 // creation
1121 addCandidate(
1122 new ast::VariableExpr{ variableExpr->location, variableExpr->var }, tenv );
1123 }
1124
1125 void postvisit( const ast::ConstantExpr * constantExpr ) {
1126 addCandidate( constantExpr, tenv );
1127 }
1128
1129 void postvisit( const ast::SizeofExpr * sizeofExpr ) {
1130 if ( sizeofExpr->type ) {
1131 addCandidate(
1132 new ast::SizeofExpr{
1133 sizeofExpr->location, resolveTypeof( sizeofExpr->type, symtab ) },
1134 tenv );
1135 } else {
1136 // find all candidates for the argument to sizeof
1137 CandidateFinder finder{ symtab, tenv };
1138 finder.find( sizeofExpr->expr );
1139 // find the lowest-cost candidate, otherwise ambiguous
1140 CandidateList winners = findMinCost( finder.candidates );
1141 if ( winners.size() != 1 ) {
1142 SemanticError(
1143 sizeofExpr->expr.get(), "Ambiguous expression in sizeof operand: " );
1144 }
1145 // return the lowest-cost candidate
1146 CandidateRef & choice = winners.front();
1147 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1148 choice->cost = Cost::zero;
1149 addCandidate( *choice, new ast::SizeofExpr{ sizeofExpr->location, choice->expr } );
1150 }
1151 }
1152
1153 void postvisit( const ast::AlignofExpr * alignofExpr ) {
1154 if ( alignofExpr->type ) {
1155 addCandidate(
1156 new ast::AlignofExpr{
1157 alignofExpr->location, resolveTypeof( alignofExpr->type, symtab ) },
1158 tenv );
1159 } else {
1160 // find all candidates for the argument to alignof
1161 CandidateFinder finder{ symtab, tenv };
1162 finder.find( alignofExpr->expr );
1163 // find the lowest-cost candidate, otherwise ambiguous
1164 CandidateList winners = findMinCost( finder.candidates );
1165 if ( winners.size() != 1 ) {
1166 SemanticError(
1167 alignofExpr->expr.get(), "Ambiguous expression in alignof operand: " );
1168 }
1169 // return the lowest-cost candidate
1170 CandidateRef & choice = winners.front();
1171 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1172 choice->cost = Cost::zero;
1173 addCandidate(
1174 *choice, new ast::AlignofExpr{ alignofExpr->location, choice->expr } );
1175 }
1176 }
1177
1178 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
1179 const ast::ReferenceToType * aggInst;
1180 if (( aggInst = offsetofExpr->type.as< ast::StructInstType >() )) ;
1181 else if (( aggInst = offsetofExpr->type.as< ast::UnionInstType >() )) ;
1182 else return;
1183
1184 for ( const ast::Decl * member : aggInst->lookup( offsetofExpr->member ) ) {
1185 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( member );
1186 addCandidate(
1187 new ast::OffsetofExpr{ offsetofExpr->location, aggInst, dwt }, tenv );
1188 }
1189 }
1190
1191 void postvisit( const ast::OffsetofExpr * offsetofExpr ) {
1192 addCandidate( offsetofExpr, tenv );
1193 }
1194
1195 void postvisit( const ast::OffsetPackExpr * offsetPackExpr ) {
1196 addCandidate( offsetPackExpr, tenv );
1197 }
1198
1199 void postvisit( const ast::LogicalExpr * logicalExpr ) {
1200 CandidateFinder finder1{ symtab, tenv };
1201 finder1.find( logicalExpr->arg1, ResolvMode::withAdjustment() );
1202 if ( finder1.candidates.empty() ) return;
1203
1204 CandidateFinder finder2{ symtab, tenv };
1205 finder2.find( logicalExpr->arg2, ResolvMode::withAdjustment() );
1206 if ( finder2.candidates.empty() ) return;
1207
1208 for ( const CandidateRef & r1 : finder1.candidates ) {
1209 for ( const CandidateRef & r2 : finder2.candidates ) {
1210 ast::TypeEnvironment env{ r1->env };
1211 env.simpleCombine( r2->env );
1212 ast::OpenVarSet open{ r1->open };
1213 mergeOpenVars( open, r2->open );
1214 ast::AssertionSet need;
1215 mergeAssertionSet( need, r1->need );
1216 mergeAssertionSet( need, r2->need );
1217
1218 addCandidate(
1219 new ast::LogicalExpr{
1220 logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
1221 move( env ), move( open ), move( need ), r1->cost + r2->cost );
1222 }
1223 }
1224 }
1225
1226 void postvisit( const ast::ConditionalExpr * conditionalExpr ) {
1227 // candidates for condition
1228 CandidateFinder finder1{ symtab, tenv };
1229 finder1.find( conditionalExpr->arg1, ResolvMode::withAdjustment() );
1230 if ( finder1.candidates.empty() ) return;
1231
1232 // candidates for true result
1233 CandidateFinder finder2{ symtab, tenv };
1234 finder2.find( conditionalExpr->arg2, ResolvMode::withAdjustment() );
1235 if ( finder2.candidates.empty() ) return;
1236
1237 // candidates for false result
1238 CandidateFinder finder3{ symtab, tenv };
1239 finder3.find( conditionalExpr->arg3, ResolvMode::withAdjustment() );
1240 if ( finder3.candidates.empty() ) return;
1241
1242 for ( const CandidateRef & r1 : finder1.candidates ) {
1243 for ( const CandidateRef & r2 : finder2.candidates ) {
1244 for ( const CandidateRef & r3 : finder3.candidates ) {
1245 ast::TypeEnvironment env{ r1->env };
1246 env.simpleCombine( r2->env );
1247 env.simpleCombine( r3->env );
1248 ast::OpenVarSet open{ r1->open };
1249 mergeOpenVars( open, r2->open );
1250 mergeOpenVars( open, r3->open );
1251 ast::AssertionSet need;
1252 mergeAssertionSet( need, r1->need );
1253 mergeAssertionSet( need, r2->need );
1254 mergeAssertionSet( need, r3->need );
1255 ast::AssertionSet have;
1256
1257 // unify true and false results, then infer parameters to produce new
1258 // candidates
1259 ast::ptr< ast::Type > common;
1260 if (
1261 unify(
1262 r2->expr->result, r3->expr->result, env, need, have, open, symtab,
1263 common )
1264 ) {
1265 // generate typed expression
1266 ast::ConditionalExpr * newExpr = new ast::ConditionalExpr{
1267 conditionalExpr->location, r1->expr, r2->expr, r3->expr };
1268 newExpr->result = common ? common : r2->expr->result;
1269 // convert both options to result type
1270 Cost cost = r1->cost + r2->cost + r3->cost;
1271 newExpr->arg2 = computeExpressionConversionCost(
1272 newExpr->arg2, newExpr->result, symtab, env, cost );
1273 newExpr->arg3 = computeExpressionConversionCost(
1274 newExpr->arg3, newExpr->result, symtab, env, cost );
1275 // output candidate
1276 CandidateRef newCand = std::make_shared<Candidate>(
1277 newExpr, move( env ), move( open ), move( need ), cost );
1278 inferParameters( newCand, candidates );
1279 }
1280 }
1281 }
1282 }
1283 }
1284
1285 void postvisit( const ast::CommaExpr * commaExpr ) {
1286 ast::TypeEnvironment env{ tenv };
1287 ast::ptr< ast::Expr > arg1 = resolveInVoidContext( commaExpr->arg1, symtab, env );
1288
1289 CandidateFinder finder2{ symtab, env };
1290 finder2.find( commaExpr->arg2, ResolvMode::withAdjustment() );
1291
1292 for ( const CandidateRef & r2 : finder2.candidates ) {
1293 addCandidate( *r2, new ast::CommaExpr{ commaExpr->location, arg1, r2->expr } );
1294 }
1295 }
1296
1297 void postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr ) {
1298 addCandidate( ctorExpr, tenv );
1299 }
1300
1301 void postvisit( const ast::ConstructorExpr * ctorExpr ) {
1302 CandidateFinder finder{ symtab, tenv };
1303 finder.find( ctorExpr->callExpr, ResolvMode::withoutPrune() );
1304 for ( CandidateRef & r : finder.candidates ) {
1305 addCandidate( *r, new ast::ConstructorExpr{ ctorExpr->location, r->expr } );
1306 }
1307 }
1308
1309 void postvisit( const ast::RangeExpr * rangeExpr ) {
1310 // resolve low and high, accept candidates where low and high types unify
1311 CandidateFinder finder1{ symtab, tenv };
1312 finder1.find( rangeExpr->low, ResolvMode::withAdjustment() );
1313 if ( finder1.candidates.empty() ) return;
1314
1315 CandidateFinder finder2{ symtab, tenv };
1316 finder2.find( rangeExpr->high, ResolvMode::withAdjustment() );
1317 if ( finder2.candidates.empty() ) return;
1318
1319 for ( const CandidateRef & r1 : finder1.candidates ) {
1320 for ( const CandidateRef & r2 : finder2.candidates ) {
1321 ast::TypeEnvironment env{ r1->env };
1322 env.simpleCombine( r2->env );
1323 ast::OpenVarSet open{ r1->open };
1324 mergeOpenVars( open, r2->open );
1325 ast::AssertionSet need;
1326 mergeAssertionSet( need, r1->need );
1327 mergeAssertionSet( need, r2->need );
1328 ast::AssertionSet have;
1329
1330 ast::ptr< ast::Type > common;
1331 if (
1332 unify(
1333 r1->expr->result, r2->expr->result, env, need, have, open, symtab,
1334 common )
1335 ) {
1336 // generate new expression
1337 ast::RangeExpr * newExpr =
1338 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1339 newExpr->result = common ? common : r1->expr->result;
1340 // add candidate
1341 CandidateRef newCand = std::make_shared<Candidate>(
1342 newExpr, move( env ), move( open ), move( need ),
1343 r1->cost + r2->cost );
1344 inferParameters( newCand, candidates );
1345 }
1346 }
1347 }
1348 }
1349
1350 void postvisit( const ast::UntypedTupleExpr * tupleExpr ) {
1351 std::vector< CandidateFinder > subCandidates =
1352 selfFinder.findSubExprs( tupleExpr->exprs );
1353 std::vector< CandidateList > possibilities;
1354 combos( subCandidates.begin(), subCandidates.end(), back_inserter( possibilities ) );
1355
1356 for ( const CandidateList & subs : possibilities ) {
1357 std::vector< ast::ptr< ast::Expr > > exprs;
1358 exprs.reserve( subs.size() );
1359 for ( const CandidateRef & sub : subs ) { exprs.emplace_back( sub->expr ); }
1360
1361 ast::TypeEnvironment env;
1362 ast::OpenVarSet open;
1363 ast::AssertionSet need;
1364 for ( const CandidateRef & sub : subs ) {
1365 env.simpleCombine( sub->env );
1366 mergeOpenVars( open, sub->open );
1367 mergeAssertionSet( need, sub->need );
1368 }
1369
1370 addCandidate(
1371 new ast::TupleExpr{ tupleExpr->location, move( exprs ) },
1372 move( env ), move( open ), move( need ), sumCost( subs ) );
1373 }
1374 }
1375
1376 void postvisit( const ast::TupleExpr * tupleExpr ) {
1377 addCandidate( tupleExpr, tenv );
1378 }
1379
1380 void postvisit( const ast::TupleIndexExpr * tupleExpr ) {
1381 addCandidate( tupleExpr, tenv );
1382 }
1383
1384 void postvisit( const ast::TupleAssignExpr * tupleExpr ) {
1385 addCandidate( tupleExpr, tenv );
1386 }
1387
1388 void postvisit( const ast::UniqueExpr * unqExpr ) {
1389 CandidateFinder finder{ symtab, tenv };
1390 finder.find( unqExpr->expr, ResolvMode::withAdjustment() );
1391 for ( CandidateRef & r : finder.candidates ) {
1392 // ensure that the the id is passed on so that the expressions are "linked"
1393 addCandidate( *r, new ast::UniqueExpr{ unqExpr->location, r->expr, unqExpr->id } );
1394 }
1395 }
1396
1397 void postvisit( const ast::StmtExpr * stmtExpr ) {
1398 addCandidate( resolveStmtExpr( stmtExpr, symtab ), tenv );
1399 }
1400
1401 void postvisit( const ast::UntypedInitExpr * initExpr ) {
1402 // handle each option like a cast
1403 CandidateList matches;
1404 PRINT(
1405 std::cerr << "untyped init expr: " << initExpr << std::endl;
1406 )
1407 // O(n^2) checks of d-types with e-types
1408 for ( const ast::InitAlternative & initAlt : initExpr->initAlts ) {
1409 // calculate target type
1410 const ast::Type * toType = resolveTypeof( initAlt.type, symtab );
1411 toType = SymTab::validateType( initExpr->location, toType, symtab );
1412 toType = adjustExprType( toType, tenv, symtab );
1413 // The call to find must occur inside this loop, otherwise polymorphic return
1414 // types are not bound to the initialization type, since return type variables are
1415 // only open for the duration of resolving the UntypedExpr.
1416 CandidateFinder finder{ symtab, tenv, toType };
1417 finder.find( initExpr->expr, ResolvMode::withAdjustment() );
1418 for ( CandidateRef & cand : finder.candidates ) {
1419 ast::TypeEnvironment env{ cand->env };
1420 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1421 ast::OpenVarSet open{ cand->open };
1422
1423 PRINT(
1424 std::cerr << " @ " << toType << " " << initAlt.designation << std::endl;
1425 )
1426
1427 // It is possible that a cast can throw away some values in a multiply-valued
1428 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of
1429 // the subexpression results that are cast directly. The candidate is invalid
1430 // if it has fewer results than there are types to cast to.
1431 int discardedValues = cand->expr->result->size() - toType->size();
1432 if ( discardedValues < 0 ) continue;
1433
1434 // unification run for side-effects
1435 unify( toType, cand->expr->result, env, need, have, open, symtab );
1436 Cost thisCost = castCost( cand->expr->result, toType, symtab, env );
1437
1438 if ( thisCost != Cost::infinity ) {
1439 // count one safe conversion for each value that is thrown away
1440 thisCost.incSafe( discardedValues );
1441 CandidateRef newCand = std::make_shared<Candidate>(
1442 new ast::InitExpr{
1443 initExpr->location, restructureCast( cand->expr, toType ),
1444 initAlt.designation },
1445 copy( cand->env ), move( open ), move( need ), cand->cost, thisCost );
1446 inferParameters( newCand, matches );
1447 }
1448 }
1449 }
1450
1451 // select first on argument cost, then conversion cost
1452 CandidateList minArgCost = findMinCost( matches );
1453 promoteCvtCost( minArgCost );
1454 candidates = findMinCost( minArgCost );
1455 }
1456
1457 void postvisit( const ast::InitExpr * ) {
1458 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
1459 }
1460
1461 void postvisit( const ast::DeletedExpr * ) {
1462 assertf( false, "CandidateFinder should never see a DeletedExpr." );
1463 }
1464
1465 void postvisit( const ast::GenericExpr * ) {
1466 assertf( false, "_Generic is not yet supported." );
1467 }
1468 };
1469
1470 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1471 /// return type. Skips ambiguous candidates.
1472 CandidateList pruneCandidates( CandidateList & candidates ) {
1473 struct PruneStruct {
1474 CandidateRef candidate;
1475 bool ambiguous;
1476
1477 PruneStruct() = default;
1478 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1479 };
1480
1481 // find lowest-cost candidate for each type
1482 std::unordered_map< std::string, PruneStruct > selected;
1483 for ( CandidateRef & candidate : candidates ) {
1484 std::string mangleName;
1485 {
1486 ast::ptr< ast::Type > newType = candidate->expr->result;
1487 candidate->env.apply( newType );
1488 mangleName = Mangle::mangle( newType );
1489 }
1490
1491 auto found = selected.find( mangleName );
1492 if ( found != selected.end() ) {
1493 if ( candidate->cost < found->second.candidate->cost ) {
1494 PRINT(
1495 std::cerr << "cost " << candidate->cost << " beats "
1496 << found->second.candidate->cost << std::endl;
1497 )
1498
1499 found->second = PruneStruct{ candidate };
1500 } else if ( candidate->cost == found->second.candidate->cost ) {
1501 // if one of the candidates contains a deleted identifier, can pick the other,
1502 // since deleted expressions should not be ambiguous if there is another option
1503 // that is at least as good
1504 if ( findDeletedExpr( candidate->expr ) ) {
1505 // do nothing
1506 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1507 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1508 PRINT( std::cerr << "current is deleted" << std::endl; )
1509 found->second = PruneStruct{ candidate };
1510 } else {
1511 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1512 found->second.ambiguous = true;
1513 }
1514 } else {
1515 PRINT(
1516 std::cerr << "cost " << candidate->cost << " loses to "
1517 << found->second.candidate->cost << std::endl;
1518 )
1519 }
1520 } else {
1521 selected.emplace_hint( found, mangleName, candidate );
1522 }
1523 }
1524
1525 // report unambiguous min-cost candidates
1526 CandidateList out;
1527 for ( auto & target : selected ) {
1528 if ( target.second.ambiguous ) continue;
1529
1530 CandidateRef cand = target.second.candidate;
1531
1532 ast::ptr< ast::Type > newResult = cand->expr->result;
1533 cand->env.applyFree( newResult );
1534 cand->expr = ast::mutate_field(
1535 cand->expr.get(), &ast::Expr::result, move( newResult ) );
1536
1537 out.emplace_back( cand );
1538 }
1539 return out;
1540 }
1541
1542} // anonymous namespace
1543
1544void CandidateFinder::find( const ast::Expr * expr, ResolvMode mode ) {
1545 // Find alternatives for expression
1546 ast::Pass<Finder> finder{ *this };
1547 expr->accept( finder );
1548
1549 if ( mode.failFast && candidates.empty() ) {
1550 SemanticError( expr, "No reasonable alternatives for expression " );
1551 }
1552
1553 if ( mode.satisfyAssns || mode.prune ) {
1554 // trim candidates to just those where the assertions are satisfiable
1555 // - necessary pre-requisite to pruning
1556 CandidateList satisfied;
1557 std::vector< std::string > errors;
1558 for ( CandidateRef & candidate : candidates ) {
1559 satisfyAssertions( candidate, localSyms, satisfied, errors );
1560 }
1561
1562 // fail early if none such
1563 if ( mode.failFast && satisfied.empty() ) {
1564 std::ostringstream stream;
1565 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1566 for ( const auto& err : errors ) {
1567 stream << err;
1568 }
1569 SemanticError( expr->location, stream.str() );
1570 }
1571
1572 // reset candidates
1573 candidates = move( satisfied );
1574 }
1575
1576 if ( mode.prune ) {
1577 // trim candidates to single best one
1578 PRINT(
1579 std::cerr << "alternatives before prune:" << std::endl;
1580 print( std::cerr, candidates );
1581 )
1582
1583 CandidateList pruned = pruneCandidates( candidates );
1584
1585 if ( mode.failFast && pruned.empty() ) {
1586 std::ostringstream stream;
1587 CandidateList winners = findMinCost( candidates );
1588 stream << "Cannot choose between " << winners.size() << " alternatives for "
1589 "expression\n";
1590 ast::print( stream, expr );
1591 stream << " Alternatives are:\n";
1592 print( stream, winners, 1 );
1593 SemanticError( expr->location, stream.str() );
1594 }
1595
1596 auto oldsize = candidates.size();
1597 candidates = move( pruned );
1598
1599 PRINT(
1600 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
1601 )
1602 PRINT(
1603 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
1604 << std::endl;
1605 )
1606 }
1607
1608 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
1609 // adjusted
1610 if ( mode.adjust ) {
1611 for ( CandidateRef & r : candidates ) {
1612 r->expr = ast::mutate_field(
1613 r->expr.get(), &ast::Expr::result,
1614 adjustExprType( r->expr->result, r->env, localSyms ) );
1615 }
1616 }
1617
1618 // Central location to handle gcc extension keyword, etc. for all expressions
1619 for ( CandidateRef & r : candidates ) {
1620 if ( r->expr->extension != expr->extension ) {
1621 r->expr.get_and_mutate()->extension = expr->extension;
1622 }
1623 }
1624}
1625
1626std::vector< CandidateFinder > CandidateFinder::findSubExprs(
1627 const std::vector< ast::ptr< ast::Expr > > & xs
1628) {
1629 std::vector< CandidateFinder > out;
1630
1631 for ( const auto & x : xs ) {
1632 out.emplace_back( localSyms, env );
1633 out.back().find( x, ResolvMode::withAdjustment() );
1634
1635 PRINT(
1636 std::cerr << "findSubExprs" << std::endl;
1637 print( std::cerr, out.back().candidates );
1638 )
1639 }
1640
1641 return out;
1642}
1643
1644} // namespace ResolvExpr
1645
1646// Local Variables: //
1647// tab-width: 4 //
1648// mode: c++ //
1649// compile-command: "make install" //
1650// End: //
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