source: src/ResolvExpr/CandidateFinder.cpp@ 0843ba6

Last change on this file since 0843ba6 was 0b6c1c9, checked in by JiadaL <j82liang@…>, 17 months ago

Merge branch 'master' of plg.uwaterloo.ca:software/cfa/cfa-cc
  • Property mode set to 100644
File size: 78.3 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// CandidateFinder.cpp --
8//
9// Author : Aaron B. Moss
10// Created On : Wed Jun 5 14:30:00 2019
11// Last Modified By : Andrew Beach
12// Last Modified On : Wed Mar 16 11:58:00 2022
13// Update Count : 3
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 "AdjustExprType.hpp"
26#include "Candidate.hpp"
27#include "CastCost.hpp" // for castCost
28#include "CompilationState.hpp"
29#include "ConversionCost.h" // for conversionCast
30#include "Cost.h"
31#include "ExplodedArg.hpp"
32#include "PolyCost.hpp"
33#include "RenameVars.h" // for renameTyVars
34#include "Resolver.h"
35#include "ResolveTypeof.h"
36#include "SatisfyAssertions.hpp"
37#include "SpecCost.hpp"
38#include "typeops.h" // for combos
39#include "Unify.h"
40#include "WidenMode.h"
41#include "AST/Expr.hpp"
42#include "AST/Node.hpp"
43#include "AST/Pass.hpp"
44#include "AST/Print.hpp"
45#include "AST/SymbolTable.hpp"
46#include "AST/Type.hpp"
47#include "Common/utility.h" // for move, copy
48#include "SymTab/Mangler.h"
49#include "Tuples/Tuples.h" // for handleTupleAssignment
50#include "InitTweak/InitTweak.h" // for getPointerBase
51
52#include "Common/Stats/Counter.h"
53
54#include "AST/Inspect.hpp" // for getFunctionName
55
56#define PRINT( text ) if ( resolvep ) { text }
57
58namespace ResolvExpr {
59
60/// Unique identifier for matching expression resolutions to their requesting expression
61ast::UniqueId globalResnSlot = 0;
62
63namespace {
64 /// First index is which argument, second is which alternative, third is which exploded element
65 using ExplodedArgs = std::deque< std::vector< ExplodedArg > >;
66
67 /// Returns a list of alternatives with the minimum cost in the given list
68 CandidateList findMinCost( const CandidateList & candidates ) {
69 CandidateList out;
70 Cost minCost = Cost::infinity;
71 for ( const CandidateRef & r : candidates ) {
72 if ( r->cost < minCost ) {
73 minCost = r->cost;
74 out.clear();
75 out.emplace_back( r );
76 } else if ( r->cost == minCost ) {
77 out.emplace_back( r );
78 }
79 }
80 return out;
81 }
82
83 /// Computes conversion cost for a given expression to a given type
84 const ast::Expr * computeExpressionConversionCost(
85 const ast::Expr * arg, const ast::Type * paramType, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env, Cost & outCost
86 ) {
87 Cost convCost = computeConversionCost(
88 arg->result, paramType, arg->get_lvalue(), symtab, env );
89 outCost += convCost;
90
91 // If there is a non-zero conversion cost, ignoring poly cost, then the expression requires
92 // conversion. Ignore poly cost for now, since this requires resolution of the cast to
93 // infer parameters and this does not currently work for the reason stated below
94 Cost tmpCost = convCost;
95 tmpCost.incPoly( -tmpCost.get_polyCost() );
96 if ( tmpCost != Cost::zero ) {
97 ast::ptr< ast::Type > newType = paramType;
98 env.apply( newType );
99 return new ast::CastExpr{ arg, newType };
100
101 // xxx - *should* be able to resolve this cast, but at the moment pointers are not
102 // castable to zero_t, but are implicitly convertible. This is clearly inconsistent,
103 // once this is fixed it should be possible to resolve the cast.
104 // xxx - this isn't working, it appears because type1 (parameter) is seen as widenable,
105 // but it shouldn't be because this makes the conversion from DT* to DT* since
106 // commontype(zero_t, DT*) is DT*, rather than nothing
107
108 // CandidateFinder finder{ symtab, env };
109 // finder.find( arg, ResolveMode::withAdjustment() );
110 // assertf( finder.candidates.size() > 0,
111 // "Somehow castable expression failed to find alternatives." );
112 // assertf( finder.candidates.size() == 1,
113 // "Somehow got multiple alternatives for known cast expression." );
114 // return finder.candidates.front()->expr;
115 }
116
117 return arg;
118 }
119
120 /// Computes conversion cost for a given candidate
121 Cost computeApplicationConversionCost(
122 CandidateRef cand, const ast::SymbolTable & symtab
123 ) {
124 auto appExpr = cand->expr.strict_as< ast::ApplicationExpr >();
125 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
126 auto function = pointer->base.strict_as< ast::FunctionType >();
127
128 Cost convCost = Cost::zero;
129 const auto & params = function->params;
130 auto param = params.begin();
131 auto & args = appExpr->args;
132
133 for ( unsigned i = 0; i < args.size(); ++i ) {
134 const ast::Type * argType = args[i]->result;
135 PRINT(
136 std::cerr << "arg expression:" << std::endl;
137 ast::print( std::cerr, args[i], 2 );
138 std::cerr << "--- results are" << std::endl;
139 ast::print( std::cerr, argType, 2 );
140 )
141
142 if ( param == params.end() ) {
143 if ( function->isVarArgs ) {
144 convCost.incUnsafe();
145 PRINT( std::cerr << "end of params with varargs function: inc unsafe: "
146 << convCost << std::endl; ; )
147 // convert reference-typed expressions into value-typed expressions
148 cand->expr = ast::mutate_field_index(
149 appExpr, &ast::ApplicationExpr::args, i,
150 referenceToRvalueConversion( args[i], convCost ) );
151 continue;
152 } else return Cost::infinity;
153 }
154
155 if ( auto def = args[i].as< ast::DefaultArgExpr >() ) {
156 // Default arguments should be free - don't include conversion cost.
157 // Unwrap them here because they are not relevant to the rest of the system
158 cand->expr = ast::mutate_field_index(
159 appExpr, &ast::ApplicationExpr::args, i, def->expr );
160 ++param;
161 continue;
162 }
163
164 // mark conversion cost and also specialization cost of param type
165 // const ast::Type * paramType = (*param)->get_type();
166 cand->expr = ast::mutate_field_index(
167 appExpr, &ast::ApplicationExpr::args, i,
168 computeExpressionConversionCost(
169 args[i], *param, symtab, cand->env, convCost ) );
170 convCost.decSpec( specCost( *param ) );
171 ++param; // can't be in for-loop update because of the continue
172 }
173
174 if ( param != params.end() ) return Cost::infinity;
175
176 // specialization cost of return types can't be accounted for directly, it disables
177 // otherwise-identical calls, like this example based on auto-newline in the I/O lib:
178 //
179 // forall(otype OS) {
180 // void ?|?(OS&, int); // with newline
181 // OS& ?|?(OS&, int); // no newline, always chosen due to more specialization
182 // }
183
184 // mark type variable and specialization cost of forall clause
185 convCost.incVar( function->forall.size() );
186 convCost.decSpec( function->assertions.size() );
187
188 return convCost;
189 }
190
191 void makeUnifiableVars(
192 const ast::FunctionType * type, ast::OpenVarSet & unifiableVars,
193 ast::AssertionSet & need
194 ) {
195 for ( auto & tyvar : type->forall ) {
196 unifiableVars[ *tyvar ] = ast::TypeData{ tyvar->base };
197 }
198 for ( auto & assn : type->assertions ) {
199 need[ assn ].isUsed = true;
200 }
201 }
202
203 /// Gets a default value from an initializer, nullptr if not present
204 const ast::ConstantExpr * getDefaultValue( const ast::Init * init ) {
205 if ( auto si = dynamic_cast< const ast::SingleInit * >( init ) ) {
206 if ( auto ce = si->value.as< ast::CastExpr >() ) {
207 return ce->arg.as< ast::ConstantExpr >();
208 } else {
209 return si->value.as< ast::ConstantExpr >();
210 }
211 }
212 return nullptr;
213 }
214
215 /// State to iteratively build a match of parameter expressions to arguments
216 struct ArgPack {
217 std::size_t parent; ///< Index of parent pack
218 ast::ptr< ast::Expr > expr; ///< The argument stored here
219 Cost cost; ///< The cost of this argument
220 ast::TypeEnvironment env; ///< Environment for this pack
221 ast::AssertionSet need; ///< Assertions outstanding for this pack
222 ast::AssertionSet have; ///< Assertions found for this pack
223 ast::OpenVarSet open; ///< Open variables for this pack
224 unsigned nextArg; ///< Index of next argument in arguments list
225 unsigned tupleStart; ///< Number of tuples that start at this index
226 unsigned nextExpl; ///< Index of next exploded element
227 unsigned explAlt; ///< Index of alternative for nextExpl > 0
228
229 ArgPack()
230 : parent( 0 ), expr(), cost( Cost::zero ), env(), need(), have(), open(), nextArg( 0 ),
231 tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
232
233 ArgPack(
234 const ast::TypeEnvironment & env, const ast::AssertionSet & need,
235 const ast::AssertionSet & have, const ast::OpenVarSet & open )
236 : parent( 0 ), expr(), cost( Cost::zero ), env( env ), need( need ), have( have ),
237 open( open ), nextArg( 0 ), tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
238
239 ArgPack(
240 std::size_t parent, const ast::Expr * expr, ast::TypeEnvironment && env,
241 ast::AssertionSet && need, ast::AssertionSet && have, ast::OpenVarSet && open,
242 unsigned nextArg, unsigned tupleStart = 0, Cost cost = Cost::zero,
243 unsigned nextExpl = 0, unsigned explAlt = 0 )
244 : parent(parent), expr( expr ), cost( cost ), env( std::move( env ) ), need( std::move( need ) ),
245 have( std::move( have ) ), open( std::move( open ) ), nextArg( nextArg ), tupleStart( tupleStart ),
246 nextExpl( nextExpl ), explAlt( explAlt ) {}
247
248 ArgPack(
249 const ArgPack & o, ast::TypeEnvironment && env, ast::AssertionSet && need,
250 ast::AssertionSet && have, ast::OpenVarSet && open, unsigned nextArg, Cost added )
251 : parent( o.parent ), expr( o.expr ), cost( o.cost + added ), env( std::move( env ) ),
252 need( std::move( need ) ), have( std::move( have ) ), open( std::move( open ) ), nextArg( nextArg ),
253 tupleStart( o.tupleStart ), nextExpl( 0 ), explAlt( 0 ) {}
254
255 /// true if this pack is in the middle of an exploded argument
256 bool hasExpl() const { return nextExpl > 0; }
257
258 /// Gets the list of exploded candidates for this pack
259 const ExplodedArg & getExpl( const ExplodedArgs & args ) const {
260 return args[ nextArg-1 ][ explAlt ];
261 }
262
263 /// Ends a tuple expression, consolidating the appropriate args
264 void endTuple( const std::vector< ArgPack > & packs ) {
265 // add all expressions in tuple to list, summing cost
266 std::deque< const ast::Expr * > exprs;
267 const ArgPack * pack = this;
268 if ( expr ) { exprs.emplace_front( expr ); }
269 while ( pack->tupleStart == 0 ) {
270 pack = &packs[pack->parent];
271 exprs.emplace_front( pack->expr );
272 cost += pack->cost;
273 }
274 // reset pack to appropriate tuple
275 std::vector< ast::ptr< ast::Expr > > exprv( exprs.begin(), exprs.end() );
276 expr = new ast::TupleExpr{ expr->location, std::move( exprv ) };
277 tupleStart = pack->tupleStart - 1;
278 parent = pack->parent;
279 }
280 };
281
282 /// Instantiates an argument to match a parameter, returns false if no matching results left
283 bool instantiateArgument(
284 const CodeLocation & location,
285 const ast::Type * paramType, const ast::Init * init, const ExplodedArgs & args,
286 std::vector< ArgPack > & results, std::size_t & genStart, const ResolveContext & context,
287 unsigned nTuples = 0
288 ) {
289 if ( auto tupleType = dynamic_cast< const ast::TupleType * >( paramType ) ) {
290 // paramType is a TupleType -- group args into a TupleExpr
291 ++nTuples;
292 for ( const ast::Type * type : *tupleType ) {
293 // xxx - dropping initializer changes behaviour from previous, but seems correct
294 // ^^^ need to handle the case where a tuple has a default argument
295 if ( ! instantiateArgument( location,
296 type, nullptr, args, results, genStart, context, nTuples ) ) return false;
297 nTuples = 0;
298 }
299 // re-constitute tuples for final generation
300 for ( auto i = genStart; i < results.size(); ++i ) {
301 results[i].endTuple( results );
302 }
303 return true;
304 } else if ( const ast::TypeInstType * ttype = Tuples::isTtype( paramType ) ) {
305 // paramType is a ttype, consumes all remaining arguments
306
307 // completed tuples; will be spliced to end of results to finish
308 std::vector< ArgPack > finalResults{};
309
310 // iterate until all results completed
311 std::size_t genEnd;
312 ++nTuples;
313 do {
314 genEnd = results.size();
315
316 // add another argument to results
317 for ( std::size_t i = genStart; i < genEnd; ++i ) {
318 unsigned nextArg = results[i].nextArg;
319
320 // use next element of exploded tuple if present
321 if ( results[i].hasExpl() ) {
322 const ExplodedArg & expl = results[i].getExpl( args );
323
324 unsigned nextExpl = results[i].nextExpl + 1;
325 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
326
327 results.emplace_back(
328 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
329 copy( results[i].need ), copy( results[i].have ),
330 copy( results[i].open ), nextArg, nTuples, Cost::zero, nextExpl,
331 results[i].explAlt );
332
333 continue;
334 }
335
336 // finish result when out of arguments
337 if ( nextArg >= args.size() ) {
338 ArgPack newResult{
339 results[i].env, results[i].need, results[i].have, results[i].open };
340 newResult.nextArg = nextArg;
341 const ast::Type * argType = nullptr;
342
343 if ( nTuples > 0 || ! results[i].expr ) {
344 // first iteration or no expression to clone,
345 // push empty tuple expression
346 newResult.parent = i;
347 newResult.expr = new ast::TupleExpr( location, {} );
348 argType = newResult.expr->result;
349 } else {
350 // clone result to collect tuple
351 newResult.parent = results[i].parent;
352 newResult.cost = results[i].cost;
353 newResult.tupleStart = results[i].tupleStart;
354 newResult.expr = results[i].expr;
355 argType = newResult.expr->result;
356
357 if ( results[i].tupleStart > 0 && Tuples::isTtype( argType ) ) {
358 // the case where a ttype value is passed directly is special,
359 // e.g. for argument forwarding purposes
360 // xxx - what if passing multiple arguments, last of which is
361 // ttype?
362 // xxx - what would happen if unify was changed so that unifying
363 // tuple
364 // types flattened both before unifying lists? then pass in
365 // TupleType (ttype) below.
366 --newResult.tupleStart;
367 } else {
368 // collapse leftover arguments into tuple
369 newResult.endTuple( results );
370 argType = newResult.expr->result;
371 }
372 }
373
374 // check unification for ttype before adding to final
375 if (
376 unify(
377 ttype, argType, newResult.env, newResult.need, newResult.have,
378 newResult.open )
379 ) {
380 finalResults.emplace_back( std::move( newResult ) );
381 }
382
383 continue;
384 }
385
386 // add each possible next argument
387 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
388 const ExplodedArg & expl = args[nextArg][j];
389
390 // fresh copies of parent parameters for this iteration
391 ast::TypeEnvironment env = results[i].env;
392 ast::OpenVarSet open = results[i].open;
393
394 env.addActual( expl.env, open );
395
396 // skip empty tuple arguments by (nearly) cloning parent into next gen
397 if ( expl.exprs.empty() ) {
398 results.emplace_back(
399 results[i], std::move( env ), copy( results[i].need ),
400 copy( results[i].have ), std::move( open ), nextArg + 1, expl.cost );
401
402 continue;
403 }
404
405 // add new result
406 results.emplace_back(
407 i, expl.exprs.front(), std::move( env ), copy( results[i].need ),
408 copy( results[i].have ), std::move( open ), nextArg + 1, nTuples,
409 expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
410 }
411 }
412
413 // reset for next round
414 genStart = genEnd;
415 nTuples = 0;
416 } while ( genEnd != results.size() );
417
418 // splice final results onto results
419 for ( std::size_t i = 0; i < finalResults.size(); ++i ) {
420 results.emplace_back( std::move( finalResults[i] ) );
421 }
422 return ! finalResults.empty();
423 }
424
425 // iterate each current subresult
426 std::size_t genEnd = results.size();
427 for ( std::size_t i = genStart; i < genEnd; ++i ) {
428 unsigned nextArg = results[i].nextArg;
429
430 // use remainder of exploded tuple if present
431 if ( results[i].hasExpl() ) {
432 const ExplodedArg & expl = results[i].getExpl( args );
433 const ast::Expr * expr = expl.exprs[ results[i].nextExpl ];
434
435 ast::TypeEnvironment env = results[i].env;
436 ast::AssertionSet need = results[i].need, have = results[i].have;
437 ast::OpenVarSet open = results[i].open;
438
439 const ast::Type * argType = expr->result;
440
441 PRINT(
442 std::cerr << "param type is ";
443 ast::print( std::cerr, paramType );
444 std::cerr << std::endl << "arg type is ";
445 ast::print( std::cerr, argType );
446 std::cerr << std::endl;
447 )
448
449 if ( unify( paramType, argType, env, need, have, open ) ) {
450 unsigned nextExpl = results[i].nextExpl + 1;
451 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
452
453 results.emplace_back(
454 i, expr, std::move( env ), std::move( need ), std::move( have ), std::move( open ), nextArg,
455 nTuples, Cost::zero, nextExpl, results[i].explAlt );
456 }
457
458 continue;
459 }
460
461 // use default initializers if out of arguments
462 if ( nextArg >= args.size() ) {
463 if ( const ast::ConstantExpr * cnst = getDefaultValue( init ) ) {
464 ast::TypeEnvironment env = results[i].env;
465 ast::AssertionSet need = results[i].need, have = results[i].have;
466 ast::OpenVarSet open = results[i].open;
467
468 if ( unify( paramType, cnst->result, env, need, have, open ) ) {
469 results.emplace_back(
470 i, new ast::DefaultArgExpr{ cnst->location, cnst }, std::move( env ),
471 std::move( need ), std::move( have ), std::move( open ), nextArg, nTuples );
472 }
473 }
474
475 continue;
476 }
477
478 // Check each possible next argument
479 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
480 const ExplodedArg & expl = args[nextArg][j];
481
482 // fresh copies of parent parameters for this iteration
483 ast::TypeEnvironment env = results[i].env;
484 ast::AssertionSet need = results[i].need, have = results[i].have;
485 ast::OpenVarSet open = results[i].open;
486
487 env.addActual( expl.env, open );
488
489 // skip empty tuple arguments by (nearly) cloning parent into next gen
490 if ( expl.exprs.empty() ) {
491 results.emplace_back(
492 results[i], std::move( env ), std::move( need ), std::move( have ), std::move( open ),
493 nextArg + 1, expl.cost );
494
495 continue;
496 }
497
498 // consider only first exploded arg
499 const ast::Expr * expr = expl.exprs.front();
500 const ast::Type * argType = expr->result;
501
502 PRINT(
503 std::cerr << "param type is ";
504 ast::print( std::cerr, paramType );
505 std::cerr << std::endl << "arg type is ";
506 ast::print( std::cerr, argType );
507 std::cerr << std::endl;
508 )
509
510 // attempt to unify types
511 ast::ptr<ast::Type> common;
512 if ( unify( paramType, argType, env, need, have, open, common ) ) {
513 // add new result
514 assert( common );
515 results.emplace_back(
516 i, expr, std::move( env ), std::move( need ), std::move( have ), std::move( open ),
517 nextArg + 1, nTuples, expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
518 //}
519 }
520 }
521 }
522
523 // reset for next parameter
524 genStart = genEnd;
525
526 return genEnd != results.size(); // were any new results added?
527 }
528
529 /// Generate a cast expression from `arg` to `toType`
530 const ast::Expr * restructureCast(
531 ast::ptr< ast::Expr > & arg, const ast::Type * toType, ast::GeneratedFlag isGenerated = ast::GeneratedCast
532 ) {
533 if (
534 arg->result->size() > 1
535 && ! toType->isVoid()
536 && ! dynamic_cast< const ast::ReferenceType * >( toType )
537 ) {
538 // Argument is a tuple and the target type is neither void nor a reference. Cast each
539 // member of the tuple to its corresponding target type, producing the tuple of those
540 // cast expressions. If there are more components of the tuple than components in the
541 // target type, then excess components do not come out in the result expression (but
542 // UniqueExpr ensures that the side effects will still be produced)
543 if ( Tuples::maybeImpureIgnoreUnique( arg ) ) {
544 // expressions which may contain side effects require a single unique instance of
545 // the expression
546 arg = new ast::UniqueExpr{ arg->location, arg };
547 }
548 std::vector< ast::ptr< ast::Expr > > components;
549 for ( unsigned i = 0; i < toType->size(); ++i ) {
550 // cast each component
551 ast::ptr< ast::Expr > idx = new ast::TupleIndexExpr{ arg->location, arg, i };
552 components.emplace_back(
553 restructureCast( idx, toType->getComponent( i ), isGenerated ) );
554 }
555 return new ast::TupleExpr{ arg->location, std::move( components ) };
556 } else {
557 // handle normally
558 return new ast::CastExpr{ arg->location, arg, toType, isGenerated };
559 }
560 }
561
562 /// Gets the name from an untyped member expression (must be NameExpr)
563 const std::string & getMemberName( const ast::UntypedMemberExpr * memberExpr ) {
564 if ( memberExpr->member.as< ast::ConstantExpr >() ) {
565 SemanticError( memberExpr, "Indexed access to struct fields unsupported: " );
566 }
567
568 return memberExpr->member.strict_as< ast::NameExpr >()->name;
569 }
570
571 /// Actually visits expressions to find their candidate interpretations
572 class Finder final : public ast::WithShortCircuiting {
573 const ResolveContext & context;
574 const ast::SymbolTable & symtab;
575 public:
576 // static size_t traceId;
577 CandidateFinder & selfFinder;
578 CandidateList & candidates;
579 const ast::TypeEnvironment & tenv;
580 ast::ptr< ast::Type > & targetType;
581
582 enum Errors {
583 NotFound,
584 NoMatch,
585 ArgsToFew,
586 ArgsToMany,
587 RetsToFew,
588 RetsToMany,
589 NoReason
590 };
591
592 struct {
593 Errors code = NotFound;
594 } reason;
595
596 Finder( CandidateFinder & f )
597 : context( f.context ), symtab( context.symtab ), selfFinder( f ),
598 candidates( f.candidates ), tenv( f.env ), targetType( f.targetType ) {}
599
600 void previsit( const ast::Node * ) { visit_children = false; }
601
602 /// Convenience to add candidate to list
603 template<typename... Args>
604 void addCandidate( Args &&... args ) {
605 candidates.emplace_back( new Candidate{ std::forward<Args>( args )... } );
606 reason.code = NoReason;
607 }
608
609 void postvisit( const ast::ApplicationExpr * applicationExpr ) {
610 addCandidate( applicationExpr, tenv );
611 }
612
613 /// Set up candidate assertions for inference
614 void inferParameters( CandidateRef & newCand, CandidateList & out );
615
616 /// Completes a function candidate with arguments located
617 void validateFunctionCandidate(
618 const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results,
619 CandidateList & out );
620
621 /// Builds a list of candidates for a function, storing them in out
622 void makeFunctionCandidates(
623 const CodeLocation & location,
624 const CandidateRef & func, const ast::FunctionType * funcType,
625 const ExplodedArgs & args, CandidateList & out );
626
627 /// Adds implicit struct-conversions to the alternative list
628 void addAnonConversions( const CandidateRef & cand );
629
630 /// Adds aggregate member interpretations
631 void addAggMembers(
632 const ast::BaseInstType * aggrInst, const ast::Expr * expr,
633 const Candidate & cand, const Cost & addedCost, const std::string & name
634 );
635
636 /// Adds tuple member interpretations
637 void addTupleMembers(
638 const ast::TupleType * tupleType, const ast::Expr * expr, const Candidate & cand,
639 const Cost & addedCost, const ast::Expr * member
640 );
641
642 /// true if expression is an lvalue
643 static bool isLvalue( const ast::Expr * x ) {
644 return x->result && ( x->get_lvalue() || x->result.as< ast::ReferenceType >() );
645 }
646
647 void postvisit( const ast::UntypedExpr * untypedExpr );
648 void postvisit( const ast::VariableExpr * variableExpr );
649 void postvisit( const ast::ConstantExpr * constantExpr );
650 void postvisit( const ast::SizeofExpr * sizeofExpr );
651 void postvisit( const ast::AlignofExpr * alignofExpr );
652 void postvisit( const ast::AddressExpr * addressExpr );
653 void postvisit( const ast::LabelAddressExpr * labelExpr );
654 void postvisit( const ast::CastExpr * castExpr );
655 void postvisit( const ast::VirtualCastExpr * castExpr );
656 void postvisit( const ast::KeywordCastExpr * castExpr );
657 void postvisit( const ast::UntypedMemberExpr * memberExpr );
658 void postvisit( const ast::MemberExpr * memberExpr );
659 void postvisit( const ast::NameExpr * nameExpr );
660 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr );
661 void postvisit( const ast::OffsetofExpr * offsetofExpr );
662 void postvisit( const ast::OffsetPackExpr * offsetPackExpr );
663 void postvisit( const ast::LogicalExpr * logicalExpr );
664 void postvisit( const ast::ConditionalExpr * conditionalExpr );
665 void postvisit( const ast::CommaExpr * commaExpr );
666 void postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr );
667 void postvisit( const ast::ConstructorExpr * ctorExpr );
668 void postvisit( const ast::RangeExpr * rangeExpr );
669 void postvisit( const ast::UntypedTupleExpr * tupleExpr );
670 void postvisit( const ast::TupleExpr * tupleExpr );
671 void postvisit( const ast::TupleIndexExpr * tupleExpr );
672 void postvisit( const ast::TupleAssignExpr * tupleExpr );
673 void postvisit( const ast::UniqueExpr * unqExpr );
674 void postvisit( const ast::StmtExpr * stmtExpr );
675 void postvisit( const ast::UntypedInitExpr * initExpr );
676 void postvisit( const ast::QualifiedNameExpr * qualifiedExpr );
677
678 void postvisit( const ast::InitExpr * ) {
679 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
680 }
681
682 void postvisit( const ast::DeletedExpr * ) {
683 assertf( false, "CandidateFinder should never see a DeletedExpr." );
684 }
685
686 void postvisit( const ast::GenericExpr * ) {
687 assertf( false, "_Generic is not yet supported." );
688 }
689 };
690
691 /// Set up candidate assertions for inference
692 void Finder::inferParameters( CandidateRef & newCand, CandidateList & out ) {
693 // Set need bindings for any unbound assertions
694 ast::UniqueId crntResnSlot = 0; // matching ID for this expression's assertions
695 for ( auto & assn : newCand->need ) {
696 // skip already-matched assertions
697 if ( assn.second.resnSlot != 0 ) continue;
698 // assign slot for expression if needed
699 if ( crntResnSlot == 0 ) { crntResnSlot = ++globalResnSlot; }
700 // fix slot to assertion
701 assn.second.resnSlot = crntResnSlot;
702 }
703 // pair slot to expression
704 if ( crntResnSlot != 0 ) {
705 newCand->expr.get_and_mutate()->inferred.resnSlots().emplace_back( crntResnSlot );
706 }
707
708 // add to output list; assertion satisfaction will occur later
709 out.emplace_back( newCand );
710 }
711
712 /// Completes a function candidate with arguments located
713 void Finder::validateFunctionCandidate(
714 const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results,
715 CandidateList & out
716 ) {
717 ast::ApplicationExpr * appExpr =
718 new ast::ApplicationExpr{ func->expr->location, func->expr };
719 // sum cost and accumulate arguments
720 std::deque< const ast::Expr * > args;
721 Cost cost = func->cost;
722 const ArgPack * pack = &result;
723 while ( pack->expr ) {
724 args.emplace_front( pack->expr );
725 cost += pack->cost;
726 pack = &results[pack->parent];
727 }
728 std::vector< ast::ptr< ast::Expr > > vargs( args.begin(), args.end() );
729 appExpr->args = std::move( vargs );
730 // build and validate new candidate
731 auto newCand =
732 std::make_shared<Candidate>( appExpr, result.env, result.open, result.need, cost );
733 PRINT(
734 std::cerr << "instantiate function success: " << appExpr << std::endl;
735 std::cerr << "need assertions:" << std::endl;
736 ast::print( std::cerr, result.need, 2 );
737 )
738 inferParameters( newCand, out );
739 }
740
741 /// Builds a list of candidates for a function, storing them in out
742 void Finder::makeFunctionCandidates(
743 const CodeLocation & location,
744 const CandidateRef & func, const ast::FunctionType * funcType,
745 const ExplodedArgs & args, CandidateList & out
746 ) {
747 ast::OpenVarSet funcOpen;
748 ast::AssertionSet funcNeed, funcHave;
749 ast::TypeEnvironment funcEnv{ func->env };
750 makeUnifiableVars( funcType, funcOpen, funcNeed );
751 // add all type variables as open variables now so that those not used in the
752 // parameter list are still considered open
753 funcEnv.add( funcType->forall );
754
755 if ( targetType && ! targetType->isVoid() && ! funcType->returns.empty() ) {
756 // attempt to narrow based on expected target type
757 const ast::Type * returnType = funcType->returns.front();
758 if ( selfFinder.strictMode ) {
759 if ( !unifyExact(
760 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, noWiden() ) // xxx - is no widening correct?
761 ) {
762 // unification failed, do not pursue this candidate
763 return;
764 }
765 } else {
766 if ( !unify(
767 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen )
768 ) {
769 // unification failed, do not pursue this candidate
770 return;
771 }
772 }
773 }
774
775 // iteratively build matches, one parameter at a time
776 std::vector< ArgPack > results;
777 results.emplace_back( funcEnv, funcNeed, funcHave, funcOpen );
778 std::size_t genStart = 0;
779
780 // xxx - how to handle default arg after change to ftype representation?
781 if (const ast::VariableExpr * varExpr = func->expr.as<ast::VariableExpr>()) {
782 if (const ast::FunctionDecl * funcDecl = varExpr->var.as<ast::FunctionDecl>()) {
783 // function may have default args only if directly calling by name
784 // must use types on candidate however, due to RenameVars substitution
785 auto nParams = funcType->params.size();
786
787 for (size_t i=0; i<nParams; ++i) {
788 auto obj = funcDecl->params[i].strict_as<ast::ObjectDecl>();
789 if ( !instantiateArgument( location,
790 funcType->params[i], obj->init, args, results, genStart, context)) return;
791 }
792 goto endMatch;
793 }
794 }
795 for ( const auto & param : funcType->params ) {
796 // Try adding the arguments corresponding to the current parameter to the existing
797 // matches
798 // no default args for indirect calls
799 if ( !instantiateArgument( location,
800 param, nullptr, args, results, genStart, context ) ) return;
801 }
802
803 endMatch:
804 if ( funcType->isVarArgs ) {
805 // append any unused arguments to vararg pack
806 std::size_t genEnd;
807 do {
808 genEnd = results.size();
809
810 // iterate results
811 for ( std::size_t i = genStart; i < genEnd; ++i ) {
812 unsigned nextArg = results[i].nextArg;
813
814 // use remainder of exploded tuple if present
815 if ( results[i].hasExpl() ) {
816 const ExplodedArg & expl = results[i].getExpl( args );
817
818 unsigned nextExpl = results[i].nextExpl + 1;
819 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
820
821 results.emplace_back(
822 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
823 copy( results[i].need ), copy( results[i].have ),
824 copy( results[i].open ), nextArg, 0, Cost::zero, nextExpl,
825 results[i].explAlt );
826
827 continue;
828 }
829
830 // finish result when out of arguments
831 if ( nextArg >= args.size() ) {
832 validateFunctionCandidate( func, results[i], results, out );
833
834 continue;
835 }
836
837 // add each possible next argument
838 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
839 const ExplodedArg & expl = args[nextArg][j];
840
841 // fresh copies of parent parameters for this iteration
842 ast::TypeEnvironment env = results[i].env;
843 ast::OpenVarSet open = results[i].open;
844
845 env.addActual( expl.env, open );
846
847 // skip empty tuple arguments by (nearly) cloning parent into next gen
848 if ( expl.exprs.empty() ) {
849 results.emplace_back(
850 results[i], std::move( env ), copy( results[i].need ),
851 copy( results[i].have ), std::move( open ), nextArg + 1,
852 expl.cost );
853
854 continue;
855 }
856
857 // add new result
858 results.emplace_back(
859 i, expl.exprs.front(), std::move( env ), copy( results[i].need ),
860 copy( results[i].have ), std::move( open ), nextArg + 1, 0, expl.cost,
861 expl.exprs.size() == 1 ? 0 : 1, j );
862 }
863 }
864
865 genStart = genEnd;
866 } while( genEnd != results.size() );
867 } else {
868 // filter out the results that don't use all the arguments
869 for ( std::size_t i = genStart; i < results.size(); ++i ) {
870 ArgPack & result = results[i];
871 if ( ! result.hasExpl() && result.nextArg >= args.size() ) {
872 validateFunctionCandidate( func, result, results, out );
873 }
874 }
875 }
876 }
877
878 /// Adds implicit struct-conversions to the alternative list
879 void Finder::addAnonConversions( const CandidateRef & cand ) {
880 // adds anonymous member interpretations whenever an aggregate value type is seen.
881 // it's okay for the aggregate expression to have reference type -- cast it to the
882 // base type to treat the aggregate as the referenced value
883 ast::ptr< ast::Expr > aggrExpr( cand->expr );
884 ast::ptr< ast::Type > & aggrType = aggrExpr.get_and_mutate()->result;
885 cand->env.apply( aggrType );
886
887 if ( aggrType.as< ast::ReferenceType >() ) {
888 aggrExpr = new ast::CastExpr{ aggrExpr, aggrType->stripReferences() };
889 }
890
891 if ( auto structInst = aggrExpr->result.as< ast::StructInstType >() ) {
892 addAggMembers( structInst, aggrExpr, *cand, Cost::unsafe, "" );
893 } else if ( auto unionInst = aggrExpr->result.as< ast::UnionInstType >() ) {
894 addAggMembers( unionInst, aggrExpr, *cand, Cost::unsafe, "" );
895 } else if ( auto enumInst = aggrExpr->result.as< ast::EnumInstType >() ) {
896 if ( enumInst->base->base ) {
897 CandidateFinder finder( context, tenv );
898 auto location = aggrExpr->location;
899 auto callExpr = new ast::UntypedExpr(
900 location, new ast::NameExpr( location, "valueE" ), {aggrExpr}
901 );
902 finder.find( callExpr );
903 CandidateList winners = findMinCost( finder.candidates );
904 if (winners.size() != 1) {
905 SemanticError( callExpr, "Ambiguous expression in valueE..." );
906 }
907 CandidateRef & choice = winners.front();
908 choice->cost.incSafe();
909 candidates.emplace_back( std::move(choice) );
910 }
911
912 }
913 }
914
915 /// Adds aggregate member interpretations
916 void Finder::addAggMembers(
917 const ast::BaseInstType * aggrInst, const ast::Expr * expr,
918 const Candidate & cand, const Cost & addedCost, const std::string & name
919 ) {
920 for ( const ast::Decl * decl : aggrInst->lookup( name ) ) {
921 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( decl );
922 CandidateRef newCand = std::make_shared<Candidate>(
923 cand, new ast::MemberExpr{ expr->location, dwt, expr }, addedCost );
924 // add anonymous member interpretations whenever an aggregate value type is seen
925 // as a member expression
926 addAnonConversions( newCand );
927 candidates.emplace_back( std::move( newCand ) );
928 }
929 }
930
931 /// Adds tuple member interpretations
932 void Finder::addTupleMembers(
933 const ast::TupleType * tupleType, const ast::Expr * expr, const Candidate & cand,
934 const Cost & addedCost, const ast::Expr * member
935 ) {
936 if ( auto constantExpr = dynamic_cast< const ast::ConstantExpr * >( member ) ) {
937 // get the value of the constant expression as an int, must be between 0 and the
938 // length of the tuple to have meaning
939 long long val = constantExpr->intValue();
940 if ( val >= 0 && (unsigned long long)val < tupleType->size() ) {
941 addCandidate(
942 cand, new ast::TupleIndexExpr{ expr->location, expr, (unsigned)val },
943 addedCost );
944 }
945 }
946 }
947
948 void Finder::postvisit( const ast::UntypedExpr * untypedExpr ) {
949 std::vector< CandidateFinder > argCandidates =
950 selfFinder.findSubExprs( untypedExpr->args );
951
952 // take care of possible tuple assignments
953 // if not tuple assignment, handled as normal function call
954 Tuples::handleTupleAssignment( selfFinder, untypedExpr, argCandidates );
955
956 CandidateFinder funcFinder( context, tenv );
957 if (auto nameExpr = untypedExpr->func.as<ast::NameExpr>()) {
958 auto kind = ast::SymbolTable::getSpecialFunctionKind(nameExpr->name);
959 if (kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS) {
960 assertf(!argCandidates.empty(), "special function call without argument");
961 for (auto & firstArgCand: argCandidates[0]) {
962 ast::ptr<ast::Type> argType = firstArgCand->expr->result;
963 firstArgCand->env.apply(argType);
964 // strip references
965 // xxx - is this correct?
966 while (argType.as<ast::ReferenceType>()) argType = argType.as<ast::ReferenceType>()->base;
967
968 // convert 1-tuple to plain type
969 if (auto tuple = argType.as<ast::TupleType>()) {
970 if (tuple->size() == 1) {
971 argType = tuple->types[0];
972 }
973 }
974
975 // if argType is an unbound type parameter, all special functions need to be searched.
976 if (isUnboundType(argType)) {
977 funcFinder.otypeKeys.clear();
978 break;
979 }
980
981 if (argType.as<ast::PointerType>()) funcFinder.otypeKeys.insert(Mangle::Encoding::pointer);
982 else funcFinder.otypeKeys.insert(Mangle::mangle(argType, Mangle::NoGenericParams | Mangle::Type));
983 }
984 }
985 }
986 // if candidates are already produced, do not fail
987 // xxx - is it possible that handleTupleAssignment and main finder both produce candidates?
988 // this means there exists ctor/assign functions with a tuple as first parameter.
989 ResolveMode mode = {
990 true, // adjust
991 !untypedExpr->func.as<ast::NameExpr>(), // prune if not calling by name
992 selfFinder.candidates.empty() // failfast if other options are not found
993 };
994 funcFinder.find( untypedExpr->func, mode );
995 // short-circuit if no candidates
996 // if ( funcFinder.candidates.empty() ) return;
997
998 reason.code = NoMatch;
999
1000 // find function operators
1001 ast::ptr< ast::Expr > opExpr = new ast::NameExpr{ untypedExpr->location, "?()" }; // ??? why not ?{}
1002 CandidateFinder opFinder( context, tenv );
1003 // okay if there aren't any function operations
1004 opFinder.find( opExpr, ResolveMode::withoutFailFast() );
1005 PRINT(
1006 std::cerr << "known function ops:" << std::endl;
1007 print( std::cerr, opFinder.candidates, 1 );
1008 )
1009
1010 // pre-explode arguments
1011 ExplodedArgs argExpansions;
1012 for ( const CandidateFinder & args : argCandidates ) {
1013 argExpansions.emplace_back();
1014 auto & argE = argExpansions.back();
1015 for ( const CandidateRef & arg : args ) { argE.emplace_back( *arg, symtab ); }
1016 }
1017
1018 // Find function matches
1019 CandidateList found;
1020 SemanticErrorException errors;
1021 for ( CandidateRef & func : funcFinder ) {
1022 try {
1023 PRINT(
1024 std::cerr << "working on alternative:" << std::endl;
1025 print( std::cerr, *func, 2 );
1026 )
1027
1028 // check if the type is a pointer to function
1029 const ast::Type * funcResult = func->expr->result->stripReferences();
1030 if ( auto pointer = dynamic_cast< const ast::PointerType * >( funcResult ) ) {
1031 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
1032 // if (!selfFinder.allowVoid && function->returns.empty()) continue;
1033 CandidateRef newFunc{ new Candidate{ *func } };
1034 newFunc->expr =
1035 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
1036 makeFunctionCandidates( untypedExpr->location,
1037 newFunc, function, argExpansions, found );
1038 }
1039 } else if (
1040 auto inst = dynamic_cast< const ast::TypeInstType * >( funcResult )
1041 ) {
1042 if ( const ast::EqvClass * clz = func->env.lookup( *inst ) ) {
1043 if ( auto function = clz->bound.as< ast::FunctionType >() ) {
1044 CandidateRef newFunc( new Candidate( *func ) );
1045 newFunc->expr =
1046 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
1047 makeFunctionCandidates( untypedExpr->location,
1048 newFunc, function, argExpansions, found );
1049 }
1050 }
1051 }
1052 } catch ( SemanticErrorException & e ) { errors.append( e ); }
1053 }
1054
1055 // Find matches on function operators `?()`
1056 if ( ! opFinder.candidates.empty() ) {
1057 // add exploded function alternatives to front of argument list
1058 std::vector< ExplodedArg > funcE;
1059 funcE.reserve( funcFinder.candidates.size() );
1060 for ( const CandidateRef & func : funcFinder ) {
1061 funcE.emplace_back( *func, symtab );
1062 }
1063 argExpansions.emplace_front( std::move( funcE ) );
1064
1065 for ( const CandidateRef & op : opFinder ) {
1066 try {
1067 // check if type is pointer-to-function
1068 const ast::Type * opResult = op->expr->result->stripReferences();
1069 if ( auto pointer = dynamic_cast< const ast::PointerType * >( opResult ) ) {
1070 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
1071 CandidateRef newOp{ new Candidate{ *op} };
1072 newOp->expr =
1073 referenceToRvalueConversion( newOp->expr, newOp->cost );
1074 makeFunctionCandidates( untypedExpr->location,
1075 newOp, function, argExpansions, found );
1076 }
1077 }
1078 } catch ( SemanticErrorException & e ) { errors.append( e ); }
1079 }
1080 }
1081
1082 // Implement SFINAE; resolution errors are only errors if there aren't any non-error
1083 // candidates
1084 if ( found.empty() && ! errors.isEmpty() ) { throw errors; }
1085
1086 // only keep the best matching intrinsic result to match C semantics (no unexpected narrowing/widening)
1087 // TODO: keep one for each set of argument candidates?
1088 Cost intrinsicCost = Cost::infinity;
1089 CandidateList intrinsicResult;
1090
1091 // Compute conversion costs
1092 for ( CandidateRef & withFunc : found ) {
1093 Cost cvtCost = computeApplicationConversionCost( withFunc, symtab );
1094
1095 PRINT(
1096 auto appExpr = withFunc->expr.strict_as< ast::ApplicationExpr >();
1097 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
1098 auto function = pointer->base.strict_as< ast::FunctionType >();
1099
1100 std::cerr << "Case +++++++++++++ " << appExpr->func << std::endl;
1101 std::cerr << "parameters are:" << std::endl;
1102 ast::printAll( std::cerr, function->params, 2 );
1103 std::cerr << "arguments are:" << std::endl;
1104 ast::printAll( std::cerr, appExpr->args, 2 );
1105 std::cerr << "bindings are:" << std::endl;
1106 ast::print( std::cerr, withFunc->env, 2 );
1107 std::cerr << "cost is: " << withFunc->cost << std::endl;
1108 std::cerr << "cost of conversion is:" << cvtCost << std::endl;
1109 )
1110
1111 if ( cvtCost != Cost::infinity ) {
1112 withFunc->cvtCost = cvtCost;
1113 withFunc->cost += cvtCost;
1114 auto func = withFunc->expr.strict_as<ast::ApplicationExpr>()->func.as<ast::VariableExpr>();
1115 if (func && func->var->linkage == ast::Linkage::Intrinsic) {
1116 if (withFunc->cost < intrinsicCost) {
1117 intrinsicResult.clear();
1118 intrinsicCost = withFunc->cost;
1119 }
1120 if (withFunc->cost == intrinsicCost) {
1121 intrinsicResult.emplace_back(std::move(withFunc));
1122 }
1123 } else {
1124 candidates.emplace_back( std::move( withFunc ) );
1125 }
1126 }
1127 }
1128 spliceBegin( candidates, intrinsicResult );
1129 found = std::move( candidates );
1130
1131 // use a new list so that candidates are not examined by addAnonConversions twice
1132 // CandidateList winners = findMinCost( found );
1133 // promoteCvtCost( winners );
1134
1135 // function may return a struct/union value, in which case we need to add candidates
1136 // for implicit conversions to each of the anonymous members, which must happen after
1137 // `findMinCost`, since anon conversions are never the cheapest
1138 for ( const CandidateRef & c : found ) {
1139 addAnonConversions( c );
1140 }
1141 // would this be too slow when we don't check cost anymore?
1142 spliceBegin( candidates, found );
1143
1144 if ( candidates.empty() && targetType && ! targetType->isVoid() && !selfFinder.strictMode ) {
1145 // If resolution is unsuccessful with a target type, try again without, since it
1146 // will sometimes succeed when it wouldn't with a target type binding.
1147 // For example:
1148 // forall( otype T ) T & ?[]( T *, ptrdiff_t );
1149 // const char * x = "hello world";
1150 // unsigned char ch = x[0];
1151 // Fails with simple return type binding (xxx -- check this!) as follows:
1152 // * T is bound to unsigned char
1153 // * (x: const char *) is unified with unsigned char *, which fails
1154 // xxx -- fix this better
1155 targetType = nullptr;
1156 postvisit( untypedExpr );
1157 }
1158 }
1159
1160 void Finder::postvisit( const ast::AddressExpr * addressExpr ) {
1161 CandidateFinder finder( context, tenv );
1162 finder.find( addressExpr->arg );
1163
1164 if ( finder.candidates.empty() ) return;
1165
1166 reason.code = NoMatch;
1167
1168 for ( CandidateRef & r : finder.candidates ) {
1169 if ( !isLvalue( r->expr ) ) continue;
1170 addCandidate( *r, new ast::AddressExpr{ addressExpr->location, r->expr } );
1171 }
1172 }
1173
1174 void Finder::postvisit( const ast::LabelAddressExpr * labelExpr ) {
1175 addCandidate( labelExpr, tenv );
1176 }
1177
1178 void Finder::postvisit( const ast::CastExpr * castExpr ) {
1179 ast::ptr< ast::Type > toType = castExpr->result;
1180 assert( toType );
1181 toType = resolveTypeof( toType, context );
1182 toType = adjustExprType( toType, tenv, symtab );
1183
1184 CandidateFinder finder( context, tenv, toType );
1185 if (toType->isVoid()) {
1186 finder.allowVoid = true;
1187 }
1188 if ( castExpr->kind == ast::CastExpr::Return ) {
1189 finder.strictMode = true;
1190 finder.find( castExpr->arg, ResolveMode::withAdjustment() );
1191
1192 // return casts are eliminated (merely selecting an overload, no actual operation)
1193 candidates = std::move(finder.candidates);
1194 }
1195 finder.find( castExpr->arg, ResolveMode::withAdjustment() );
1196
1197 if ( !finder.candidates.empty() ) reason.code = NoMatch;
1198
1199 CandidateList matches;
1200 Cost minExprCost = Cost::infinity;
1201 Cost minCastCost = Cost::infinity;
1202 for ( CandidateRef & cand : finder.candidates ) {
1203 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1204 ast::OpenVarSet open( cand->open );
1205
1206 cand->env.extractOpenVars( open );
1207
1208 // It is possible that a cast can throw away some values in a multiply-valued
1209 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of the
1210 // subexpression results that are cast directly. The candidate is invalid if it
1211 // has fewer results than there are types to cast to.
1212 int discardedValues = cand->expr->result->size() - toType->size();
1213 if ( discardedValues < 0 ) continue;
1214
1215 // unification run for side-effects
1216 unify( toType, cand->expr->result, cand->env, need, have, open );
1217 Cost thisCost =
1218 (castExpr->isGenerated == ast::GeneratedFlag::GeneratedCast)
1219 ? conversionCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env )
1220 : castCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env );
1221
1222 PRINT(
1223 std::cerr << "working on cast with result: " << toType << std::endl;
1224 std::cerr << "and expr type: " << cand->expr->result << std::endl;
1225 std::cerr << "env: " << cand->env << std::endl;
1226 )
1227 if ( thisCost != Cost::infinity ) {
1228 PRINT(
1229 std::cerr << "has finite cost." << std::endl;
1230 )
1231 // count one safe conversion for each value that is thrown away
1232 thisCost.incSafe( discardedValues );
1233 // select first on argument cost, then conversion cost
1234 if ( cand->cost < minExprCost || ( cand->cost == minExprCost && thisCost < minCastCost ) ) {
1235 minExprCost = cand->cost;
1236 minCastCost = thisCost;
1237 matches.clear();
1238
1239
1240 }
1241 // ambiguous case, still output candidates to print in error message
1242 if ( cand->cost == minExprCost && thisCost == minCastCost ) {
1243 CandidateRef newCand = std::make_shared<Candidate>(
1244 restructureCast( cand->expr, toType, castExpr->isGenerated ),
1245 copy( cand->env ), std::move( open ), std::move( need ), cand->cost + thisCost);
1246 // currently assertions are always resolved immediately so this should have no effect.
1247 // if this somehow changes in the future (e.g. delayed by indeterminate return type)
1248 // we may need to revisit the logic.
1249 inferParameters( newCand, matches );
1250 }
1251 // else skip, better alternatives found
1252
1253 }
1254 }
1255 candidates = std::move(matches);
1256
1257 //CandidateList minArgCost = findMinCost( matches );
1258 //promoteCvtCost( minArgCost );
1259 //candidates = findMinCost( minArgCost );
1260 }
1261
1262 void Finder::postvisit( const ast::VirtualCastExpr * castExpr ) {
1263 assertf( castExpr->result, "Implicit virtual cast targets not yet supported." );
1264 CandidateFinder finder( context, tenv );
1265 // don't prune here, all alternatives guaranteed to have same type
1266 finder.find( castExpr->arg, ResolveMode::withoutPrune() );
1267 for ( CandidateRef & r : finder.candidates ) {
1268 addCandidate(
1269 *r,
1270 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
1271 }
1272 }
1273
1274 void Finder::postvisit( const ast::KeywordCastExpr * castExpr ) {
1275 const auto & loc = castExpr->location;
1276 assertf( castExpr->result, "Cast target should have been set in Validate." );
1277 auto ref = castExpr->result.strict_as<ast::ReferenceType>();
1278 auto inst = ref->base.strict_as<ast::StructInstType>();
1279 auto target = inst->base.get();
1280
1281 CandidateFinder finder( context, tenv );
1282
1283 auto pick_alternatives = [target, this](CandidateList & found, bool expect_ref) {
1284 for (auto & cand : found) {
1285 const ast::Type * expr = cand->expr->result.get();
1286 if (expect_ref) {
1287 auto res = dynamic_cast<const ast::ReferenceType*>(expr);
1288 if (!res) { continue; }
1289 expr = res->base.get();
1290 }
1291
1292 if (auto insttype = dynamic_cast<const ast::TypeInstType*>(expr)) {
1293 auto td = cand->env.lookup(*insttype);
1294 if (!td) { continue; }
1295 expr = td->bound.get();
1296 }
1297
1298 if (auto base = dynamic_cast<const ast::StructInstType*>(expr)) {
1299 if (base->base == target) {
1300 candidates.push_back( std::move(cand) );
1301 reason.code = NoReason;
1302 }
1303 }
1304 }
1305 };
1306
1307 try {
1308 // Attempt 1 : turn (thread&)X into (thread$&)X.__thrd
1309 // Clone is purely for memory management
1310 std::unique_ptr<const ast::Expr> tech1 { new ast::UntypedMemberExpr(loc, new ast::NameExpr(loc, castExpr->concrete_target.field), castExpr->arg) };
1311
1312 // don't prune here, since it's guaranteed all alternatives will have the same type
1313 finder.find( tech1.get(), ResolveMode::withoutPrune() );
1314 pick_alternatives(finder.candidates, false);
1315
1316 return;
1317 } catch(SemanticErrorException & ) {}
1318
1319 // Fallback : turn (thread&)X into (thread$&)get_thread(X)
1320 std::unique_ptr<const ast::Expr> fallback { ast::UntypedExpr::createDeref(loc, new ast::UntypedExpr(loc, new ast::NameExpr(loc, castExpr->concrete_target.getter), { castExpr->arg })) };
1321 // don't prune here, since it's guaranteed all alternatives will have the same type
1322 finder.find( fallback.get(), ResolveMode::withoutPrune() );
1323
1324 pick_alternatives(finder.candidates, true);
1325
1326 // Whatever happens here, we have no more fallbacks
1327 }
1328
1329 void Finder::postvisit( const ast::UntypedMemberExpr * memberExpr ) {
1330 CandidateFinder aggFinder( context, tenv );
1331 aggFinder.find( memberExpr->aggregate, ResolveMode::withAdjustment() );
1332 for ( CandidateRef & agg : aggFinder.candidates ) {
1333 // it's okay for the aggregate expression to have reference type -- cast it to the
1334 // base type to treat the aggregate as the referenced value
1335 Cost addedCost = Cost::zero;
1336 agg->expr = referenceToRvalueConversion( agg->expr, addedCost );
1337
1338 // find member of the given type
1339 if ( auto structInst = agg->expr->result.as< ast::StructInstType >() ) {
1340 addAggMembers(
1341 structInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1342 } else if ( auto unionInst = agg->expr->result.as< ast::UnionInstType >() ) {
1343 addAggMembers(
1344 unionInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1345 } else if ( auto tupleType = agg->expr->result.as< ast::TupleType >() ) {
1346 addTupleMembers( tupleType, agg->expr, *agg, addedCost, memberExpr->member );
1347 }
1348 }
1349 }
1350
1351 void Finder::postvisit( const ast::MemberExpr * memberExpr ) {
1352 addCandidate( memberExpr, tenv );
1353 }
1354
1355 void Finder::postvisit( const ast::NameExpr * nameExpr ) {
1356 std::vector< ast::SymbolTable::IdData > declList;
1357 if (!selfFinder.otypeKeys.empty()) {
1358 auto kind = ast::SymbolTable::getSpecialFunctionKind(nameExpr->name);
1359 assertf(kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS, "special lookup with non-special target: %s", nameExpr->name.c_str());
1360
1361 for (auto & otypeKey: selfFinder.otypeKeys) {
1362 auto result = symtab.specialLookupId(kind, otypeKey);
1363 declList.insert(declList.end(), std::make_move_iterator(result.begin()), std::make_move_iterator(result.end()));
1364 }
1365 } else {
1366 declList = symtab.lookupId( nameExpr->name );
1367 }
1368 PRINT( std::cerr << "nameExpr is " << nameExpr->name << std::endl; )
1369
1370 if ( declList.empty() ) return;
1371
1372 reason.code = NoMatch;
1373
1374 for ( auto & data : declList ) {
1375 Cost cost = Cost::zero;
1376 ast::Expr * newExpr = data.combine( nameExpr->location, cost );
1377
1378 // bool bentConversion = false;
1379 // if ( auto inst = newExpr->result.as<ast::EnumInstType>() ) {
1380 // if ( inst->base && inst->base->base ) {
1381 // bentConversion = true;
1382 // }
1383 // }
1384
1385 // CandidateRef newCand = std::make_shared<Candidate>(
1386 // newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, bentConversion? Cost::safe: Cost::zero,
1387 // cost );
1388 CandidateRef newCand = std::make_shared<Candidate>(
1389 newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, Cost::zero,
1390 cost );
1391 if (newCand->expr->env) {
1392 newCand->env.add(*newCand->expr->env);
1393 auto mutExpr = newCand->expr.get_and_mutate();
1394 mutExpr->env = nullptr;
1395 newCand->expr = mutExpr;
1396 }
1397
1398 PRINT(
1399 std::cerr << "decl is ";
1400 ast::print( std::cerr, data.id );
1401 std::cerr << std::endl;
1402 std::cerr << "newExpr is ";
1403 ast::print( std::cerr, newExpr );
1404 std::cerr << std::endl;
1405 )
1406 newCand->expr = ast::mutate_field(
1407 newCand->expr.get(), &ast::Expr::result,
1408 renameTyVars( newCand->expr->result ) );
1409 // add anonymous member interpretations whenever an aggregate value type is seen
1410 // as a name expression
1411 addAnonConversions( newCand );
1412 candidates.emplace_back( std::move( newCand ) );
1413 }
1414 }
1415
1416 void Finder::postvisit(const ast::VariableExpr *variableExpr) {
1417 // not sufficient to just pass `variableExpr` here, type might have changed
1418
1419 auto cand = new Candidate(variableExpr, tenv);
1420 candidates.emplace_back(cand);
1421 }
1422
1423 void Finder::postvisit( const ast::ConstantExpr * constantExpr ) {
1424 addCandidate( constantExpr, tenv );
1425 }
1426
1427 void Finder::postvisit( const ast::SizeofExpr * sizeofExpr ) {
1428 if ( sizeofExpr->type ) {
1429 addCandidate(
1430 new ast::SizeofExpr{
1431 sizeofExpr->location, resolveTypeof( sizeofExpr->type, context ) },
1432 tenv );
1433 } else {
1434 // find all candidates for the argument to sizeof
1435 CandidateFinder finder( context, tenv );
1436 finder.find( sizeofExpr->expr );
1437 // find the lowest-cost candidate, otherwise ambiguous
1438 CandidateList winners = findMinCost( finder.candidates );
1439 if ( winners.size() != 1 ) {
1440 SemanticError(
1441 sizeofExpr->expr.get(), "Ambiguous expression in sizeof operand: " );
1442 }
1443 // return the lowest-cost candidate
1444 CandidateRef & choice = winners.front();
1445 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1446 choice->cost = Cost::zero;
1447 addCandidate( *choice, new ast::SizeofExpr{ sizeofExpr->location, choice->expr } );
1448 }
1449 }
1450
1451 void Finder::postvisit( const ast::AlignofExpr * alignofExpr ) {
1452 if ( alignofExpr->type ) {
1453 addCandidate(
1454 new ast::AlignofExpr{
1455 alignofExpr->location, resolveTypeof( alignofExpr->type, context ) },
1456 tenv );
1457 } else {
1458 // find all candidates for the argument to alignof
1459 CandidateFinder finder( context, tenv );
1460 finder.find( alignofExpr->expr );
1461 // find the lowest-cost candidate, otherwise ambiguous
1462 CandidateList winners = findMinCost( finder.candidates );
1463 if ( winners.size() != 1 ) {
1464 SemanticError(
1465 alignofExpr->expr.get(), "Ambiguous expression in alignof operand: " );
1466 }
1467 // return the lowest-cost candidate
1468 CandidateRef & choice = winners.front();
1469 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1470 choice->cost = Cost::zero;
1471 addCandidate(
1472 *choice, new ast::AlignofExpr{ alignofExpr->location, choice->expr } );
1473 }
1474 }
1475
1476 void Finder::postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
1477 const ast::BaseInstType * aggInst;
1478 if (( aggInst = offsetofExpr->type.as< ast::StructInstType >() )) ;
1479 else if (( aggInst = offsetofExpr->type.as< ast::UnionInstType >() )) ;
1480 else return;
1481
1482 for ( const ast::Decl * member : aggInst->lookup( offsetofExpr->member ) ) {
1483 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( member );
1484 addCandidate(
1485 new ast::OffsetofExpr{ offsetofExpr->location, aggInst, dwt }, tenv );
1486 }
1487 }
1488
1489 void Finder::postvisit( const ast::OffsetofExpr * offsetofExpr ) {
1490 addCandidate( offsetofExpr, tenv );
1491 }
1492
1493 void Finder::postvisit( const ast::OffsetPackExpr * offsetPackExpr ) {
1494 addCandidate( offsetPackExpr, tenv );
1495 }
1496
1497 void Finder::postvisit( const ast::LogicalExpr * logicalExpr ) {
1498 CandidateFinder finder1( context, tenv );
1499 ast::ptr<ast::Expr> arg1 = createCondExpr( logicalExpr->arg1 );
1500 finder1.find( arg1, ResolveMode::withAdjustment() );
1501 if ( finder1.candidates.empty() ) return;
1502
1503 CandidateFinder finder2( context, tenv );
1504 ast::ptr<ast::Expr> arg2 = createCondExpr( logicalExpr->arg2 );
1505 finder2.find( arg2, ResolveMode::withAdjustment() );
1506 if ( finder2.candidates.empty() ) return;
1507
1508 reason.code = NoMatch;
1509
1510 for ( const CandidateRef & r1 : finder1.candidates ) {
1511 for ( const CandidateRef & r2 : finder2.candidates ) {
1512 ast::TypeEnvironment env{ r1->env };
1513 env.simpleCombine( r2->env );
1514 ast::OpenVarSet open{ r1->open };
1515 mergeOpenVars( open, r2->open );
1516 ast::AssertionSet need;
1517 mergeAssertionSet( need, r1->need );
1518 mergeAssertionSet( need, r2->need );
1519
1520 addCandidate(
1521 new ast::LogicalExpr{
1522 logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
1523 std::move( env ), std::move( open ), std::move( need ), r1->cost + r2->cost );
1524 }
1525 }
1526 }
1527
1528 void Finder::postvisit( const ast::ConditionalExpr * conditionalExpr ) {
1529 // candidates for condition
1530 ast::ptr<ast::Expr> arg1 = createCondExpr( conditionalExpr->arg1 );
1531 CandidateFinder finder1( context, tenv );
1532 finder1.find( arg1, ResolveMode::withAdjustment() );
1533 if ( finder1.candidates.empty() ) return;
1534
1535 // candidates for true result
1536 // FIX ME: resolves and runs arg1 twice when arg2 is missing.
1537 ast::Expr const * arg2 = conditionalExpr->arg2;
1538 arg2 = arg2 ? arg2 : conditionalExpr->arg1.get();
1539 CandidateFinder finder2( context, tenv );
1540 finder2.allowVoid = true;
1541 finder2.find( arg2, ResolveMode::withAdjustment() );
1542 if ( finder2.candidates.empty() ) return;
1543
1544 // candidates for false result
1545 CandidateFinder finder3( context, tenv );
1546 finder3.allowVoid = true;
1547 finder3.find( conditionalExpr->arg3, ResolveMode::withAdjustment() );
1548 if ( finder3.candidates.empty() ) return;
1549
1550 reason.code = NoMatch;
1551
1552 for ( const CandidateRef & r1 : finder1.candidates ) {
1553 for ( const CandidateRef & r2 : finder2.candidates ) {
1554 for ( const CandidateRef & r3 : finder3.candidates ) {
1555 ast::TypeEnvironment env{ r1->env };
1556 env.simpleCombine( r2->env );
1557 env.simpleCombine( r3->env );
1558 ast::OpenVarSet open{ r1->open };
1559 mergeOpenVars( open, r2->open );
1560 mergeOpenVars( open, r3->open );
1561 ast::AssertionSet need;
1562 mergeAssertionSet( need, r1->need );
1563 mergeAssertionSet( need, r2->need );
1564 mergeAssertionSet( need, r3->need );
1565 ast::AssertionSet have;
1566
1567 // unify true and false results, then infer parameters to produce new
1568 // candidates
1569 ast::ptr< ast::Type > common;
1570 if (
1571 unify(
1572 r2->expr->result, r3->expr->result, env, need, have, open,
1573 common )
1574 ) {
1575 // generate typed expression
1576 ast::ConditionalExpr * newExpr = new ast::ConditionalExpr{
1577 conditionalExpr->location, r1->expr, r2->expr, r3->expr };
1578 newExpr->result = common ? common : r2->expr->result;
1579 // convert both options to result type
1580 Cost cost = r1->cost + r2->cost + r3->cost;
1581 newExpr->arg2 = computeExpressionConversionCost(
1582 newExpr->arg2, newExpr->result, symtab, env, cost );
1583 newExpr->arg3 = computeExpressionConversionCost(
1584 newExpr->arg3, newExpr->result, symtab, env, cost );
1585 // output candidate
1586 CandidateRef newCand = std::make_shared<Candidate>(
1587 newExpr, std::move( env ), std::move( open ), std::move( need ), cost );
1588 inferParameters( newCand, candidates );
1589 }
1590 }
1591 }
1592 }
1593 }
1594
1595 void Finder::postvisit( const ast::CommaExpr * commaExpr ) {
1596 ast::TypeEnvironment env{ tenv };
1597 ast::ptr< ast::Expr > arg1 = resolveInVoidContext( commaExpr->arg1, context, env );
1598
1599 CandidateFinder finder2( context, env );
1600 finder2.find( commaExpr->arg2, ResolveMode::withAdjustment() );
1601
1602 for ( const CandidateRef & r2 : finder2.candidates ) {
1603 addCandidate( *r2, new ast::CommaExpr{ commaExpr->location, arg1, r2->expr } );
1604 }
1605 }
1606
1607 void Finder::postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr ) {
1608 addCandidate( ctorExpr, tenv );
1609 }
1610
1611 void Finder::postvisit( const ast::ConstructorExpr * ctorExpr ) {
1612 CandidateFinder finder( context, tenv );
1613 finder.allowVoid = true;
1614 finder.find( ctorExpr->callExpr, ResolveMode::withoutPrune() );
1615 for ( CandidateRef & r : finder.candidates ) {
1616 addCandidate( *r, new ast::ConstructorExpr{ ctorExpr->location, r->expr } );
1617 }
1618 }
1619
1620 void Finder::postvisit( const ast::RangeExpr * rangeExpr ) {
1621 // resolve low and high, accept candidates where low and high types unify
1622 CandidateFinder finder1( context, tenv );
1623 finder1.find( rangeExpr->low, ResolveMode::withAdjustment() );
1624 if ( finder1.candidates.empty() ) return;
1625
1626 CandidateFinder finder2( context, tenv );
1627 finder2.find( rangeExpr->high, ResolveMode::withAdjustment() );
1628 if ( finder2.candidates.empty() ) return;
1629
1630 reason.code = NoMatch;
1631
1632 for ( const CandidateRef & r1 : finder1.candidates ) {
1633 for ( const CandidateRef & r2 : finder2.candidates ) {
1634 ast::TypeEnvironment env{ r1->env };
1635 env.simpleCombine( r2->env );
1636 ast::OpenVarSet open{ r1->open };
1637 mergeOpenVars( open, r2->open );
1638 ast::AssertionSet need;
1639 mergeAssertionSet( need, r1->need );
1640 mergeAssertionSet( need, r2->need );
1641 ast::AssertionSet have;
1642
1643 ast::ptr< ast::Type > common;
1644 if (
1645 unify(
1646 r1->expr->result, r2->expr->result, env, need, have, open,
1647 common )
1648 ) {
1649 // generate new expression
1650 ast::RangeExpr * newExpr =
1651 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1652 newExpr->result = common ? common : r1->expr->result;
1653 // add candidate
1654 CandidateRef newCand = std::make_shared<Candidate>(
1655 newExpr, std::move( env ), std::move( open ), std::move( need ),
1656 r1->cost + r2->cost );
1657 inferParameters( newCand, candidates );
1658 }
1659 }
1660 }
1661 }
1662
1663 void Finder::postvisit( const ast::UntypedTupleExpr * tupleExpr ) {
1664 std::vector< CandidateFinder > subCandidates =
1665 selfFinder.findSubExprs( tupleExpr->exprs );
1666 std::vector< CandidateList > possibilities;
1667 combos( subCandidates.begin(), subCandidates.end(), back_inserter( possibilities ) );
1668
1669 for ( const CandidateList & subs : possibilities ) {
1670 std::vector< ast::ptr< ast::Expr > > exprs;
1671 exprs.reserve( subs.size() );
1672 for ( const CandidateRef & sub : subs ) { exprs.emplace_back( sub->expr ); }
1673
1674 ast::TypeEnvironment env;
1675 ast::OpenVarSet open;
1676 ast::AssertionSet need;
1677 for ( const CandidateRef & sub : subs ) {
1678 env.simpleCombine( sub->env );
1679 mergeOpenVars( open, sub->open );
1680 mergeAssertionSet( need, sub->need );
1681 }
1682
1683 addCandidate(
1684 new ast::TupleExpr{ tupleExpr->location, std::move( exprs ) },
1685 std::move( env ), std::move( open ), std::move( need ), sumCost( subs ) );
1686 }
1687 }
1688
1689 void Finder::postvisit( const ast::TupleExpr * tupleExpr ) {
1690 addCandidate( tupleExpr, tenv );
1691 }
1692
1693 void Finder::postvisit( const ast::TupleIndexExpr * tupleExpr ) {
1694 addCandidate( tupleExpr, tenv );
1695 }
1696
1697 void Finder::postvisit( const ast::TupleAssignExpr * tupleExpr ) {
1698 addCandidate( tupleExpr, tenv );
1699 }
1700
1701 void Finder::postvisit( const ast::UniqueExpr * unqExpr ) {
1702 CandidateFinder finder( context, tenv );
1703 finder.find( unqExpr->expr, ResolveMode::withAdjustment() );
1704 for ( CandidateRef & r : finder.candidates ) {
1705 // ensure that the the id is passed on so that the expressions are "linked"
1706 addCandidate( *r, new ast::UniqueExpr{ unqExpr->location, r->expr, unqExpr->id } );
1707 }
1708 }
1709
1710 void Finder::postvisit( const ast::StmtExpr * stmtExpr ) {
1711 addCandidate( resolveStmtExpr( stmtExpr, context ), tenv );
1712 }
1713
1714 void Finder::postvisit( const ast::UntypedInitExpr * initExpr ) {
1715 // handle each option like a cast
1716 CandidateList matches;
1717 PRINT(
1718 std::cerr << "untyped init expr: " << initExpr << std::endl;
1719 )
1720 // O(n^2) checks of d-types with e-types
1721 for ( const ast::InitAlternative & initAlt : initExpr->initAlts ) {
1722 // calculate target type
1723 const ast::Type * toType = resolveTypeof( initAlt.type, context );
1724 toType = adjustExprType( toType, tenv, symtab );
1725 // The call to find must occur inside this loop, otherwise polymorphic return
1726 // types are not bound to the initialization type, since return type variables are
1727 // only open for the duration of resolving the UntypedExpr.
1728 CandidateFinder finder( context, tenv, toType );
1729 finder.find( initExpr->expr, ResolveMode::withAdjustment() );
1730
1731 Cost minExprCost = Cost::infinity;
1732 Cost minCastCost = Cost::infinity;
1733 for ( CandidateRef & cand : finder.candidates ) {
1734 if (reason.code == NotFound) reason.code = NoMatch;
1735
1736 ast::TypeEnvironment env{ cand->env };
1737 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1738 ast::OpenVarSet open{ cand->open };
1739
1740 PRINT(
1741 std::cerr << " @ " << toType << " " << initAlt.designation << std::endl;
1742 )
1743
1744 // It is possible that a cast can throw away some values in a multiply-valued
1745 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of
1746 // the subexpression results that are cast directly. The candidate is invalid
1747 // if it has fewer results than there are types to cast to.
1748 int discardedValues = cand->expr->result->size() - toType->size();
1749 if ( discardedValues < 0 ) continue;
1750
1751 // unification run for side-effects
1752 ast::ptr<ast::Type> common;
1753 bool canUnify = unify( toType, cand->expr->result, env, need, have, open, common );
1754 (void) canUnify;
1755 Cost thisCost = computeConversionCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1756 symtab, env );
1757 PRINT(
1758 Cost legacyCost = castCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1759 symtab, env );
1760 std::cerr << "Considering initialization:";
1761 std::cerr << std::endl << " FROM: " << cand->expr->result << std::endl;
1762 std::cerr << std::endl << " TO: " << toType << std::endl;
1763 std::cerr << std::endl << " Unification " << (canUnify ? "succeeded" : "failed");
1764 std::cerr << std::endl << " Legacy cost " << legacyCost;
1765 std::cerr << std::endl << " New cost " << thisCost;
1766 std::cerr << std::endl;
1767 )
1768 if ( thisCost != Cost::infinity ) {
1769 // count one safe conversion for each value that is thrown away
1770 thisCost.incSafe( discardedValues );
1771 if ( cand->cost < minExprCost || ( cand->cost == minExprCost && thisCost < minCastCost ) ) {
1772 minExprCost = cand->cost;
1773 minCastCost = thisCost;
1774 matches.clear();
1775 }
1776 // ambiguous case, still output candidates to print in error message
1777 if ( cand->cost == minExprCost && thisCost == minCastCost ) {
1778 auto commonAsEnumAttr = common.as<ast::EnumAttrType>();
1779 if ( commonAsEnumAttr && commonAsEnumAttr->attr == ast::EnumAttribute::Value ) {
1780 auto callExpr = new ast::UntypedExpr(
1781 cand->expr->location, new ast::NameExpr( cand->expr->location, "valueE"), {cand->expr} );
1782 CandidateFinder finder( context, env );
1783 finder.find( callExpr );
1784 CandidateList winners = findMinCost( finder.candidates );
1785 if (winners.size() != 1) {
1786 SemanticError( callExpr, "Ambiguous expression in valueE..." );
1787 }
1788 CandidateRef & choice = winners.front();
1789 // assert( valueCall->result );
1790 CandidateRef newCand = std::make_shared<Candidate>(
1791 new ast::InitExpr{
1792 initExpr->location,
1793 // restructureCast( cand->expr, toType ),
1794 choice->expr,
1795 initAlt.designation },
1796 std::move(env), std::move( open ), std::move( need ), cand->cost + thisCost );
1797 inferParameters( newCand, matches );
1798 } else {
1799 CandidateRef newCand = std::make_shared<Candidate>(
1800 new ast::InitExpr{
1801 initExpr->location,
1802 restructureCast( cand->expr, toType ),
1803 initAlt.designation },
1804 std::move(env), std::move( open ), std::move( need ), cand->cost + thisCost );
1805 // currently assertions are always resolved immediately so this should have no effect.
1806 // if this somehow changes in the future (e.g. delayed by indeterminate return type)
1807 // we may need to revisit the logic.
1808 inferParameters( newCand, matches );
1809 }
1810 }
1811 }
1812 }
1813 }
1814
1815 // select first on argument cost, then conversion cost
1816 // CandidateList minArgCost = findMinCost( matches );
1817 // promoteCvtCost( minArgCost );
1818 // candidates = findMinCost( minArgCost );
1819 candidates = std::move(matches);
1820 }
1821
1822 void Finder::postvisit( const ast::QualifiedNameExpr * expr ) {
1823 std::vector< ast::SymbolTable::IdData > declList = symtab.lookupId( expr->name );
1824 if ( declList.empty() ) return;
1825
1826 for ( ast::SymbolTable::IdData & data: declList ) {
1827 const ast::Type * t = data.id->get_type()->stripReferences();
1828 if ( const ast::EnumInstType * enumInstType =
1829 dynamic_cast<const ast::EnumInstType *>( t ) ) {
1830 if ( enumInstType->base->name == expr->type_decl->name ) {
1831 Cost cost = Cost::zero;
1832 ast::Expr * newExpr = data.combine( expr->location, cost );
1833 // CandidateRef newCand =
1834 // std::make_shared<Candidate>(
1835 // newExpr, copy( tenv ), ast::OpenVarSet{},
1836 // ast::AssertionSet{}, Cost::safe, cost
1837 // );
1838 CandidateRef newCand =
1839 std::make_shared<Candidate>(
1840 newExpr, copy( tenv ), ast::OpenVarSet{},
1841 ast::AssertionSet{}, Cost::zero, cost
1842 );
1843 if (newCand->expr->env) {
1844 newCand->env.add(*newCand->expr->env);
1845 auto mutExpr = newCand->expr.get_and_mutate();
1846 mutExpr->env = nullptr;
1847 newCand->expr = mutExpr;
1848 }
1849
1850 newCand->expr = ast::mutate_field(
1851 newCand->expr.get(), &ast::Expr::result,
1852 renameTyVars( newCand->expr->result ) );
1853 addAnonConversions( newCand );
1854 candidates.emplace_back( std::move( newCand ) );
1855 }
1856 }
1857 }
1858 }
1859 // size_t Finder::traceId = Stats::Heap::new_stacktrace_id("Finder");
1860 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1861 /// return type. Skips ambiguous candidates.
1862
1863} // anonymous namespace
1864
1865bool CandidateFinder::pruneCandidates( CandidateList & candidates, CandidateList & out, std::vector<std::string> & errors ) {
1866 struct PruneStruct {
1867 CandidateRef candidate;
1868 bool ambiguous;
1869
1870 PruneStruct() = default;
1871 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1872 };
1873
1874 // find lowest-cost candidate for each type
1875 std::unordered_map< std::string, PruneStruct > selected;
1876 // attempt to skip satisfyAssertions on more expensive alternatives if better options have been found
1877 std::sort(candidates.begin(), candidates.end(), [](const CandidateRef & x, const CandidateRef & y){return x->cost < y->cost;});
1878 for ( CandidateRef & candidate : candidates ) {
1879 std::string mangleName;
1880 {
1881 ast::ptr< ast::Type > newType = candidate->expr->result;
1882 assertf(candidate->expr->result, "Result of expression %p for candidate is null", candidate->expr.get());
1883 candidate->env.apply( newType );
1884 mangleName = Mangle::mangle( newType );
1885 }
1886
1887 auto found = selected.find( mangleName );
1888 if (found != selected.end() && found->second.candidate->cost < candidate->cost) {
1889 PRINT(
1890 std::cerr << "cost " << candidate->cost << " loses to "
1891 << found->second.candidate->cost << std::endl;
1892 )
1893 continue;
1894 }
1895
1896 // xxx - when do satisfyAssertions produce more than 1 result?
1897 // this should only happen when initial result type contains
1898 // unbound type parameters, then it should never be pruned by
1899 // the previous step, since renameTyVars guarantees the mangled name
1900 // is unique.
1901 CandidateList satisfied;
1902 bool needRecomputeKey = false;
1903 if (candidate->need.empty()) {
1904 satisfied.emplace_back(candidate);
1905 }
1906 else {
1907 satisfyAssertions(candidate, context.symtab, satisfied, errors);
1908 needRecomputeKey = true;
1909 }
1910
1911 for (auto & newCand : satisfied) {
1912 // recomputes type key, if satisfyAssertions changed it
1913 if (needRecomputeKey)
1914 {
1915 ast::ptr< ast::Type > newType = newCand->expr->result;
1916 assertf(newCand->expr->result, "Result of expression %p for candidate is null", newCand->expr.get());
1917 newCand->env.apply( newType );
1918 mangleName = Mangle::mangle( newType );
1919 }
1920 auto found = selected.find( mangleName );
1921 if ( found != selected.end() ) {
1922 // tiebreaking by picking the lower cost on CURRENT expression
1923 // NOTE: this behavior is different from C semantics.
1924 // Specific remediations are performed for C operators at postvisit(UntypedExpr).
1925 // Further investigations may take place.
1926 if ( newCand->cost < found->second.candidate->cost
1927 || (newCand->cost == found->second.candidate->cost && newCand->cvtCost < found->second.candidate->cvtCost) ) {
1928 PRINT(
1929 std::cerr << "cost " << newCand->cost << " beats "
1930 << found->second.candidate->cost << std::endl;
1931 )
1932
1933 found->second = PruneStruct{ newCand };
1934 } else if ( newCand->cost == found->second.candidate->cost && newCand->cvtCost == found->second.candidate->cvtCost ) {
1935 // if one of the candidates contains a deleted identifier, can pick the other,
1936 // since deleted expressions should not be ambiguous if there is another option
1937 // that is at least as good
1938 if ( findDeletedExpr( newCand->expr ) ) {
1939 // do nothing
1940 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1941 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1942 PRINT( std::cerr << "current is deleted" << std::endl; )
1943 found->second = PruneStruct{ newCand };
1944 } else {
1945 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1946 found->second.ambiguous = true;
1947 }
1948 } else {
1949 // xxx - can satisfyAssertions increase the cost?
1950 PRINT(
1951 std::cerr << "cost " << newCand->cost << " loses to "
1952 << found->second.candidate->cost << std::endl;
1953 )
1954 }
1955 } else {
1956 selected.emplace_hint( found, mangleName, newCand );
1957 }
1958 }
1959 }
1960
1961 // report unambiguous min-cost candidates
1962 // CandidateList out;
1963 for ( auto & target : selected ) {
1964 if ( target.second.ambiguous ) continue;
1965
1966 CandidateRef cand = target.second.candidate;
1967
1968 ast::ptr< ast::Type > newResult = cand->expr->result;
1969 cand->env.applyFree( newResult );
1970 cand->expr = ast::mutate_field(
1971 cand->expr.get(), &ast::Expr::result, std::move( newResult ) );
1972
1973 out.emplace_back( cand );
1974 }
1975 // if everything is lost in satisfyAssertions, report the error
1976 return !selected.empty();
1977}
1978
1979void CandidateFinder::find( const ast::Expr * expr, ResolveMode mode ) {
1980 // Find alternatives for expression
1981 ast::Pass<Finder> finder{ *this };
1982 expr->accept( finder );
1983
1984 if ( mode.failFast && candidates.empty() ) {
1985 switch(finder.core.reason.code) {
1986 case Finder::NotFound:
1987 { SemanticError( expr, "No alternatives for expression " ); break; }
1988 case Finder::NoMatch:
1989 { SemanticError( expr, "Invalid application of existing declaration(s) in expression " ); break; }
1990 case Finder::ArgsToFew:
1991 case Finder::ArgsToMany:
1992 case Finder::RetsToFew:
1993 case Finder::RetsToMany:
1994 case Finder::NoReason:
1995 default:
1996 { SemanticError( expr->location, "No reasonable alternatives for expression : reasons unkown" ); }
1997 }
1998 }
1999
2000 /*
2001 if ( mode.satisfyAssns || mode.prune ) {
2002 // trim candidates to just those where the assertions are satisfiable
2003 // - necessary pre-requisite to pruning
2004 CandidateList satisfied;
2005 std::vector< std::string > errors;
2006 for ( CandidateRef & candidate : candidates ) {
2007 satisfyAssertions( candidate, localSyms, satisfied, errors );
2008 }
2009
2010 // fail early if none such
2011 if ( mode.failFast && satisfied.empty() ) {
2012 std::ostringstream stream;
2013 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
2014 for ( const auto& err : errors ) {
2015 stream << err;
2016 }
2017 SemanticError( expr->location, stream.str() );
2018 }
2019
2020 // reset candidates
2021 candidates = move( satisfied );
2022 }
2023 */
2024
2025 // optimization: don't prune for NameExpr since it never has cost
2026 if ( mode.prune && !dynamic_cast<const ast::NameExpr *>(expr) ) {
2027 // trim candidates to single best one
2028 PRINT(
2029 std::cerr << "alternatives before prune:" << std::endl;
2030 print( std::cerr, candidates );
2031 )
2032
2033 CandidateList pruned;
2034 std::vector<std::string> errors;
2035 bool found = pruneCandidates( candidates, pruned, errors );
2036
2037 if ( mode.failFast && pruned.empty() ) {
2038 std::ostringstream stream;
2039 if (found) {
2040 CandidateList winners = findMinCost( candidates );
2041 stream << "Cannot choose between " << winners.size() << " alternatives for "
2042 "expression\n";
2043 ast::print( stream, expr );
2044 stream << " Alternatives are:\n";
2045 print( stream, winners, 1 );
2046 SemanticError( expr->location, stream.str() );
2047 }
2048 else {
2049 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
2050 for ( const auto& err : errors ) {
2051 stream << err;
2052 }
2053 SemanticError( expr->location, stream.str() );
2054 }
2055 }
2056
2057 auto oldsize = candidates.size();
2058 candidates = std::move( pruned );
2059
2060 PRINT(
2061 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
2062 )
2063 PRINT(
2064 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
2065 << std::endl;
2066 )
2067 }
2068
2069 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
2070 // adjusted
2071 if ( mode.adjust ) {
2072 for ( CandidateRef & r : candidates ) {
2073 r->expr = ast::mutate_field(
2074 r->expr.get(), &ast::Expr::result,
2075 adjustExprType( r->expr->result, r->env, context.symtab ) );
2076 }
2077 }
2078
2079 // Central location to handle gcc extension keyword, etc. for all expressions
2080 for ( CandidateRef & r : candidates ) {
2081 if ( r->expr->extension != expr->extension ) {
2082 r->expr.get_and_mutate()->extension = expr->extension;
2083 }
2084 }
2085}
2086
2087std::vector< CandidateFinder > CandidateFinder::findSubExprs(
2088 const std::vector< ast::ptr< ast::Expr > > & xs
2089) {
2090 std::vector< CandidateFinder > out;
2091
2092 for ( const auto & x : xs ) {
2093 out.emplace_back( context, env );
2094 out.back().find( x, ResolveMode::withAdjustment() );
2095
2096 PRINT(
2097 std::cerr << "findSubExprs" << std::endl;
2098 print( std::cerr, out.back().candidates );
2099 )
2100 }
2101
2102 return out;
2103}
2104
2105const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
2106 if ( expr->result.as< ast::ReferenceType >() ) {
2107 // cast away reference from expr
2108 cost.incReference();
2109 return new ast::CastExpr{ expr, expr->result->stripReferences() };
2110 }
2111
2112 return expr;
2113}
2114
2115Cost computeConversionCost(
2116 const ast::Type * argType, const ast::Type * paramType, bool argIsLvalue,
2117 const ast::SymbolTable & symtab, const ast::TypeEnvironment & env
2118) {
2119 PRINT(
2120 std::cerr << std::endl << "converting ";
2121 ast::print( std::cerr, argType, 2 );
2122 std::cerr << std::endl << " to ";
2123 ast::print( std::cerr, paramType, 2 );
2124 std::cerr << std::endl << "environment is: ";
2125 ast::print( std::cerr, env, 2 );
2126 std::cerr << std::endl;
2127 )
2128 Cost convCost = conversionCost( argType, paramType, argIsLvalue, symtab, env );
2129 PRINT(
2130 std::cerr << std::endl << "cost is " << convCost << std::endl;
2131 )
2132 if ( convCost == Cost::infinity ) return convCost;
2133 convCost.incPoly( polyCost( paramType, symtab, env ) + polyCost( argType, symtab, env ) );
2134 PRINT(
2135 std::cerr << "cost with polycost is " << convCost << std::endl;
2136 )
2137 return convCost;
2138}
2139
2140const ast::Expr * createCondExpr( const ast::Expr * expr ) {
2141 assert( expr );
2142 return new ast::CastExpr( expr->location,
2143 ast::UntypedExpr::createCall( expr->location,
2144 "?!=?",
2145 {
2146 expr,
2147 new ast::ConstantExpr( expr->location,
2148 new ast::ZeroType(), "0", std::make_optional( 0ull )
2149 ),
2150 }
2151 ),
2152 new ast::BasicType( ast::BasicKind::SignedInt )
2153 );
2154}
2155
2156} // namespace ResolvExpr
2157
2158// Local Variables: //
2159// tab-width: 4 //
2160// mode: c++ //
2161// compile-command: "make install" //
2162// End: //
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