source: src/ResolvExpr/CandidateFinder.cpp@ 0c840fc

ast-experimental
Last change on this file since 0c840fc was 46da46b, checked in by Fangren Yu <f37yu@…>, 2 years ago

current progress
  • Property mode set to 100644
File size: 72.4 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 "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 "WidenMode.h"
33#include "SatisfyAssertions.hpp"
34#include "typeops.h" // for adjustExprType, conversionCost, polyCost, specCost
35#include "Unify.h"
36#include "AST/Expr.hpp"
37#include "AST/Node.hpp"
38#include "AST/Pass.hpp"
39#include "AST/Print.hpp"
40#include "AST/SymbolTable.hpp"
41#include "AST/Type.hpp"
42#include "Common/utility.h" // for move, copy
43#include "SymTab/Mangler.h"
44#include "Tuples/Tuples.h" // for handleTupleAssignment
45#include "InitTweak/InitTweak.h" // for getPointerBase
46
47#include "Common/Stats/Counter.h"
48
49#define PRINT( text ) if ( resolvep ) { text }
50
51namespace ResolvExpr {
52
53const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
54 if ( expr->result.as< ast::ReferenceType >() ) {
55 // cast away reference from expr
56 cost.incReference();
57 return new ast::CastExpr{ expr, expr->result->stripReferences() };
58 }
59
60 return expr;
61}
62
63/// Unique identifier for matching expression resolutions to their requesting expression
64UniqueId globalResnSlot = 0;
65
66Cost computeConversionCost(
67 const ast::Type * argType, const ast::Type * paramType, bool argIsLvalue,
68 const ast::SymbolTable & symtab, const ast::TypeEnvironment & env
69) {
70 PRINT(
71 std::cerr << std::endl << "converting ";
72 ast::print( std::cerr, argType, 2 );
73 std::cerr << std::endl << " to ";
74 ast::print( std::cerr, paramType, 2 );
75 std::cerr << std::endl << "environment is: ";
76 ast::print( std::cerr, env, 2 );
77 std::cerr << std::endl;
78 )
79 Cost convCost = conversionCost( argType, paramType, argIsLvalue, symtab, env );
80 PRINT(
81 std::cerr << std::endl << "cost is " << convCost << std::endl;
82 )
83 if ( convCost == Cost::infinity ) return convCost;
84 convCost.incPoly( polyCost( paramType, symtab, env ) + polyCost( argType, symtab, env ) );
85 PRINT(
86 std::cerr << "cost with polycost is " << convCost << std::endl;
87 )
88 return convCost;
89}
90
91namespace {
92 /// First index is which argument, second is which alternative, third is which exploded element
93 using ExplodedArgs_new = std::deque< std::vector< ExplodedArg > >;
94
95 /// Returns a list of alternatives with the minimum cost in the given list
96 CandidateList findMinCost( const CandidateList & candidates ) {
97 CandidateList out;
98 Cost minCost = Cost::infinity;
99 for ( const CandidateRef & r : candidates ) {
100 if ( r->cost < minCost ) {
101 minCost = r->cost;
102 out.clear();
103 out.emplace_back( r );
104 } else if ( r->cost == minCost ) {
105 out.emplace_back( r );
106 }
107 }
108 return out;
109 }
110
111 /// Computes conversion cost for a given expression to a given type
112 const ast::Expr * computeExpressionConversionCost(
113 const ast::Expr * arg, const ast::Type * paramType, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env, Cost & outCost
114 ) {
115 Cost convCost = computeConversionCost(
116 arg->result, paramType, arg->get_lvalue(), symtab, env );
117 outCost += convCost;
118
119 // If there is a non-zero conversion cost, ignoring poly cost, then the expression requires
120 // conversion. Ignore poly cost for now, since this requires resolution of the cast to
121 // infer parameters and this does not currently work for the reason stated below
122 Cost tmpCost = convCost;
123 tmpCost.incPoly( -tmpCost.get_polyCost() );
124 if ( tmpCost != Cost::zero ) {
125 ast::ptr< ast::Type > newType = paramType;
126 env.apply( newType );
127 return new ast::CastExpr{ arg, newType };
128
129 // xxx - *should* be able to resolve this cast, but at the moment pointers are not
130 // castable to zero_t, but are implicitly convertible. This is clearly inconsistent,
131 // once this is fixed it should be possible to resolve the cast.
132 // xxx - this isn't working, it appears because type1 (parameter) is seen as widenable,
133 // but it shouldn't be because this makes the conversion from DT* to DT* since
134 // commontype(zero_t, DT*) is DT*, rather than nothing
135
136 // CandidateFinder finder{ symtab, env };
137 // finder.find( arg, ResolvMode::withAdjustment() );
138 // assertf( finder.candidates.size() > 0,
139 // "Somehow castable expression failed to find alternatives." );
140 // assertf( finder.candidates.size() == 1,
141 // "Somehow got multiple alternatives for known cast expression." );
142 // return finder.candidates.front()->expr;
143 }
144
145 return arg;
146 }
147
148 /// Computes conversion cost for a given candidate
149 Cost computeApplicationConversionCost(
150 CandidateRef cand, const ast::SymbolTable & symtab
151 ) {
152 auto appExpr = cand->expr.strict_as< ast::ApplicationExpr >();
153 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
154 auto function = pointer->base.strict_as< ast::FunctionType >();
155
156 Cost convCost = Cost::zero;
157 const auto & params = function->params;
158 auto param = params.begin();
159 auto & args = appExpr->args;
160
161 for ( unsigned i = 0; i < args.size(); ++i ) {
162 const ast::Type * argType = args[i]->result;
163 PRINT(
164 std::cerr << "arg expression:" << std::endl;
165 ast::print( std::cerr, args[i], 2 );
166 std::cerr << "--- results are" << std::endl;
167 ast::print( std::cerr, argType, 2 );
168 )
169
170 if ( param == params.end() ) {
171 if ( function->isVarArgs ) {
172 convCost.incUnsafe();
173 PRINT( std::cerr << "end of params with varargs function: inc unsafe: "
174 << convCost << std::endl; ; )
175 // convert reference-typed expressions into value-typed expressions
176 cand->expr = ast::mutate_field_index(
177 appExpr, &ast::ApplicationExpr::args, i,
178 referenceToRvalueConversion( args[i], convCost ) );
179 continue;
180 } else return Cost::infinity;
181 }
182
183 if ( auto def = args[i].as< ast::DefaultArgExpr >() ) {
184 // Default arguments should be free - don't include conversion cost.
185 // Unwrap them here because they are not relevant to the rest of the system
186 cand->expr = ast::mutate_field_index(
187 appExpr, &ast::ApplicationExpr::args, i, def->expr );
188 ++param;
189 continue;
190 }
191
192 // mark conversion cost and also specialization cost of param type
193 // const ast::Type * paramType = (*param)->get_type();
194 cand->expr = ast::mutate_field_index(
195 appExpr, &ast::ApplicationExpr::args, i,
196 computeExpressionConversionCost(
197 args[i], *param, symtab, cand->env, convCost ) );
198 convCost.decSpec( specCost( *param ) );
199 ++param; // can't be in for-loop update because of the continue
200 }
201
202 if ( param != params.end() ) return Cost::infinity;
203
204 // specialization cost of return types can't be accounted for directly, it disables
205 // otherwise-identical calls, like this example based on auto-newline in the I/O lib:
206 //
207 // forall(otype OS) {
208 // void ?|?(OS&, int); // with newline
209 // OS& ?|?(OS&, int); // no newline, always chosen due to more specialization
210 // }
211
212 // mark type variable and specialization cost of forall clause
213 convCost.incVar( function->forall.size() );
214 convCost.decSpec( function->assertions.size() );
215
216 return convCost;
217 }
218
219 void makeUnifiableVars(
220 const ast::FunctionType * type, ast::OpenVarSet & unifiableVars,
221 ast::AssertionSet & need
222 ) {
223 for ( auto & tyvar : type->forall ) {
224 unifiableVars[ *tyvar ] = ast::TypeData{ tyvar->base };
225 }
226 for ( auto & assn : type->assertions ) {
227 need[ assn ].isUsed = true;
228 }
229 }
230
231 /// Gets a default value from an initializer, nullptr if not present
232 const ast::ConstantExpr * getDefaultValue( const ast::Init * init ) {
233 if ( auto si = dynamic_cast< const ast::SingleInit * >( init ) ) {
234 if ( auto ce = si->value.as< ast::CastExpr >() ) {
235 return ce->arg.as< ast::ConstantExpr >();
236 } else {
237 return si->value.as< ast::ConstantExpr >();
238 }
239 }
240 return nullptr;
241 }
242
243 /// State to iteratively build a match of parameter expressions to arguments
244 struct ArgPack {
245 std::size_t parent; ///< Index of parent pack
246 ast::ptr< ast::Expr > expr; ///< The argument stored here
247 Cost cost; ///< The cost of this argument
248 ast::TypeEnvironment env; ///< Environment for this pack
249 ast::AssertionSet need; ///< Assertions outstanding for this pack
250 ast::AssertionSet have; ///< Assertions found for this pack
251 ast::OpenVarSet open; ///< Open variables for this pack
252 unsigned nextArg; ///< Index of next argument in arguments list
253 unsigned tupleStart; ///< Number of tuples that start at this index
254 unsigned nextExpl; ///< Index of next exploded element
255 unsigned explAlt; ///< Index of alternative for nextExpl > 0
256
257 ArgPack()
258 : parent( 0 ), expr(), cost( Cost::zero ), env(), need(), have(), open(), nextArg( 0 ),
259 tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
260
261 ArgPack(
262 const ast::TypeEnvironment & env, const ast::AssertionSet & need,
263 const ast::AssertionSet & have, const ast::OpenVarSet & open )
264 : parent( 0 ), expr(), cost( Cost::zero ), env( env ), need( need ), have( have ),
265 open( open ), nextArg( 0 ), tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
266
267 ArgPack(
268 std::size_t parent, const ast::Expr * expr, ast::TypeEnvironment && env,
269 ast::AssertionSet && need, ast::AssertionSet && have, ast::OpenVarSet && open,
270 unsigned nextArg, unsigned tupleStart = 0, Cost cost = Cost::zero,
271 unsigned nextExpl = 0, unsigned explAlt = 0 )
272 : parent(parent), expr( expr ), cost( cost ), env( std::move( env ) ), need( std::move( need ) ),
273 have( std::move( have ) ), open( std::move( open ) ), nextArg( nextArg ), tupleStart( tupleStart ),
274 nextExpl( nextExpl ), explAlt( explAlt ) {}
275
276 ArgPack(
277 const ArgPack & o, ast::TypeEnvironment && env, ast::AssertionSet && need,
278 ast::AssertionSet && have, ast::OpenVarSet && open, unsigned nextArg, Cost added )
279 : parent( o.parent ), expr( o.expr ), cost( o.cost + added ), env( std::move( env ) ),
280 need( std::move( need ) ), have( std::move( have ) ), open( std::move( open ) ), nextArg( nextArg ),
281 tupleStart( o.tupleStart ), nextExpl( 0 ), explAlt( 0 ) {}
282
283 /// true if this pack is in the middle of an exploded argument
284 bool hasExpl() const { return nextExpl > 0; }
285
286 /// Gets the list of exploded candidates for this pack
287 const ExplodedArg & getExpl( const ExplodedArgs_new & args ) const {
288 return args[ nextArg-1 ][ explAlt ];
289 }
290
291 /// Ends a tuple expression, consolidating the appropriate args
292 void endTuple( const std::vector< ArgPack > & packs ) {
293 // add all expressions in tuple to list, summing cost
294 std::deque< const ast::Expr * > exprs;
295 const ArgPack * pack = this;
296 if ( expr ) { exprs.emplace_front( expr ); }
297 while ( pack->tupleStart == 0 ) {
298 pack = &packs[pack->parent];
299 exprs.emplace_front( pack->expr );
300 cost += pack->cost;
301 }
302 // reset pack to appropriate tuple
303 std::vector< ast::ptr< ast::Expr > > exprv( exprs.begin(), exprs.end() );
304 expr = new ast::TupleExpr{ expr->location, std::move( exprv ) };
305 tupleStart = pack->tupleStart - 1;
306 parent = pack->parent;
307 }
308 };
309
310 /// Instantiates an argument to match a parameter, returns false if no matching results left
311 bool instantiateArgument(
312 const ast::Type * paramType, const ast::Init * init, const ExplodedArgs_new & args,
313 std::vector< ArgPack > & results, std::size_t & genStart, const ast::SymbolTable & symtab,
314 unsigned nTuples = 0
315 ) {
316 if ( auto tupleType = dynamic_cast< const ast::TupleType * >( paramType ) ) {
317 // paramType is a TupleType -- group args into a TupleExpr
318 ++nTuples;
319 for ( const ast::Type * type : *tupleType ) {
320 // xxx - dropping initializer changes behaviour from previous, but seems correct
321 // ^^^ need to handle the case where a tuple has a default argument
322 if ( ! instantiateArgument(
323 type, nullptr, args, results, genStart, symtab, nTuples ) ) return false;
324 nTuples = 0;
325 }
326 // re-constitute tuples for final generation
327 for ( auto i = genStart; i < results.size(); ++i ) {
328 results[i].endTuple( results );
329 }
330 return true;
331 } else if ( const ast::TypeInstType * ttype = Tuples::isTtype( paramType ) ) {
332 // paramType is a ttype, consumes all remaining arguments
333
334 // completed tuples; will be spliced to end of results to finish
335 std::vector< ArgPack > finalResults{};
336
337 // iterate until all results completed
338 std::size_t genEnd;
339 ++nTuples;
340 do {
341 genEnd = results.size();
342
343 // add another argument to results
344 for ( std::size_t i = genStart; i < genEnd; ++i ) {
345 unsigned nextArg = results[i].nextArg;
346
347 // use next element of exploded tuple if present
348 if ( results[i].hasExpl() ) {
349 const ExplodedArg & expl = results[i].getExpl( args );
350
351 unsigned nextExpl = results[i].nextExpl + 1;
352 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
353
354 results.emplace_back(
355 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
356 copy( results[i].need ), copy( results[i].have ),
357 copy( results[i].open ), nextArg, nTuples, Cost::zero, nextExpl,
358 results[i].explAlt );
359
360 continue;
361 }
362
363 // finish result when out of arguments
364 if ( nextArg >= args.size() ) {
365 ArgPack newResult{
366 results[i].env, results[i].need, results[i].have, results[i].open };
367 newResult.nextArg = nextArg;
368 const ast::Type * argType = nullptr;
369
370 if ( nTuples > 0 || ! results[i].expr ) {
371 // first iteration or no expression to clone,
372 // push empty tuple expression
373 newResult.parent = i;
374 newResult.expr = new ast::TupleExpr{ CodeLocation{}, {} };
375 argType = newResult.expr->result;
376 } else {
377 // clone result to collect tuple
378 newResult.parent = results[i].parent;
379 newResult.cost = results[i].cost;
380 newResult.tupleStart = results[i].tupleStart;
381 newResult.expr = results[i].expr;
382 argType = newResult.expr->result;
383
384 if ( results[i].tupleStart > 0 && Tuples::isTtype( argType ) ) {
385 // the case where a ttype value is passed directly is special,
386 // e.g. for argument forwarding purposes
387 // xxx - what if passing multiple arguments, last of which is
388 // ttype?
389 // xxx - what would happen if unify was changed so that unifying
390 // tuple
391 // types flattened both before unifying lists? then pass in
392 // TupleType (ttype) below.
393 --newResult.tupleStart;
394 } else {
395 // collapse leftover arguments into tuple
396 newResult.endTuple( results );
397 argType = newResult.expr->result;
398 }
399 }
400
401 // check unification for ttype before adding to final
402 if (
403 unify(
404 ttype, argType, newResult.env, newResult.need, newResult.have,
405 newResult.open, symtab )
406 ) {
407 finalResults.emplace_back( std::move( newResult ) );
408 }
409
410 continue;
411 }
412
413 // add each possible next argument
414 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
415 const ExplodedArg & expl = args[nextArg][j];
416
417 // fresh copies of parent parameters for this iteration
418 ast::TypeEnvironment env = results[i].env;
419 ast::OpenVarSet open = results[i].open;
420
421 env.addActual( expl.env, open );
422
423 // skip empty tuple arguments by (nearly) cloning parent into next gen
424 if ( expl.exprs.empty() ) {
425 results.emplace_back(
426 results[i], std::move( env ), copy( results[i].need ),
427 copy( results[i].have ), std::move( open ), nextArg + 1, expl.cost );
428
429 continue;
430 }
431
432 // add new result
433 results.emplace_back(
434 i, expl.exprs.front(), std::move( env ), copy( results[i].need ),
435 copy( results[i].have ), std::move( open ), nextArg + 1, nTuples,
436 expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
437 }
438 }
439
440 // reset for next round
441 genStart = genEnd;
442 nTuples = 0;
443 } while ( genEnd != results.size() );
444
445 // splice final results onto results
446 for ( std::size_t i = 0; i < finalResults.size(); ++i ) {
447 results.emplace_back( std::move( finalResults[i] ) );
448 }
449 return ! finalResults.empty();
450 }
451
452 // iterate each current subresult
453 std::size_t genEnd = results.size();
454 for ( std::size_t i = genStart; i < genEnd; ++i ) {
455 unsigned nextArg = results[i].nextArg;
456
457 // use remainder of exploded tuple if present
458 if ( results[i].hasExpl() ) {
459 const ExplodedArg & expl = results[i].getExpl( args );
460 const ast::Expr * expr = expl.exprs[ results[i].nextExpl ];
461
462 ast::TypeEnvironment env = results[i].env;
463 ast::AssertionSet need = results[i].need, have = results[i].have;
464 ast::OpenVarSet open = results[i].open;
465
466 const ast::Type * argType = expr->result;
467
468 PRINT(
469 std::cerr << "param type is ";
470 ast::print( std::cerr, paramType );
471 std::cerr << std::endl << "arg type is ";
472 ast::print( std::cerr, argType );
473 std::cerr << std::endl;
474 )
475
476 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
477 unsigned nextExpl = results[i].nextExpl + 1;
478 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
479
480 results.emplace_back(
481 i, expr, std::move( env ), std::move( need ), std::move( have ), std::move( open ), nextArg,
482 nTuples, Cost::zero, nextExpl, results[i].explAlt );
483 }
484
485 continue;
486 }
487
488 // use default initializers if out of arguments
489 if ( nextArg >= args.size() ) {
490 if ( const ast::ConstantExpr * cnst = getDefaultValue( init ) ) {
491 ast::TypeEnvironment env = results[i].env;
492 ast::AssertionSet need = results[i].need, have = results[i].have;
493 ast::OpenVarSet open = results[i].open;
494
495 if ( unify( paramType, cnst->result, env, need, have, open, symtab ) ) {
496 results.emplace_back(
497 i, new ast::DefaultArgExpr{ cnst->location, cnst }, std::move( env ),
498 std::move( need ), std::move( have ), std::move( open ), nextArg, nTuples );
499 }
500 }
501
502 continue;
503 }
504
505 // Check each possible next argument
506 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
507 const ExplodedArg & expl = args[nextArg][j];
508
509 // fresh copies of parent parameters for this iteration
510 ast::TypeEnvironment env = results[i].env;
511 ast::AssertionSet need = results[i].need, have = results[i].have;
512 ast::OpenVarSet open = results[i].open;
513
514 env.addActual( expl.env, open );
515
516 // skip empty tuple arguments by (nearly) cloning parent into next gen
517 if ( expl.exprs.empty() ) {
518 results.emplace_back(
519 results[i], std::move( env ), std::move( need ), std::move( have ), std::move( open ),
520 nextArg + 1, expl.cost );
521
522 continue;
523 }
524
525 // consider only first exploded arg
526 const ast::Expr * expr = expl.exprs.front();
527 const ast::Type * argType = expr->result;
528
529 PRINT(
530 std::cerr << "param type is ";
531 ast::print( std::cerr, paramType );
532 std::cerr << std::endl << "arg type is ";
533 ast::print( std::cerr, argType );
534 std::cerr << std::endl;
535 )
536
537 // attempt to unify types
538 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
539 // add new result
540 results.emplace_back(
541 i, expr, std::move( env ), std::move( need ), std::move( have ), std::move( open ),
542 nextArg + 1, nTuples, expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
543 }
544 }
545 }
546
547 // reset for next parameter
548 genStart = genEnd;
549
550 return genEnd != results.size(); // were any new results added?
551 }
552
553 /// Generate a cast expression from `arg` to `toType`
554 const ast::Expr * restructureCast(
555 ast::ptr< ast::Expr > & arg, const ast::Type * toType, ast::GeneratedFlag isGenerated = ast::GeneratedCast
556 ) {
557 if (
558 arg->result->size() > 1
559 && ! toType->isVoid()
560 && ! dynamic_cast< const ast::ReferenceType * >( toType )
561 ) {
562 // Argument is a tuple and the target type is neither void nor a reference. Cast each
563 // member of the tuple to its corresponding target type, producing the tuple of those
564 // cast expressions. If there are more components of the tuple than components in the
565 // target type, then excess components do not come out in the result expression (but
566 // UniqueExpr ensures that the side effects will still be produced)
567 if ( Tuples::maybeImpureIgnoreUnique( arg ) ) {
568 // expressions which may contain side effects require a single unique instance of
569 // the expression
570 arg = new ast::UniqueExpr{ arg->location, arg };
571 }
572 std::vector< ast::ptr< ast::Expr > > components;
573 for ( unsigned i = 0; i < toType->size(); ++i ) {
574 // cast each component
575 ast::ptr< ast::Expr > idx = new ast::TupleIndexExpr{ arg->location, arg, i };
576 components.emplace_back(
577 restructureCast( idx, toType->getComponent( i ), isGenerated ) );
578 }
579 return new ast::TupleExpr{ arg->location, std::move( components ) };
580 } else {
581 // handle normally
582 return new ast::CastExpr{ arg->location, arg, toType, isGenerated };
583 }
584 }
585
586 /// Gets the name from an untyped member expression (must be NameExpr)
587 const std::string & getMemberName( const ast::UntypedMemberExpr * memberExpr ) {
588 if ( memberExpr->member.as< ast::ConstantExpr >() ) {
589 SemanticError( memberExpr, "Indexed access to struct fields unsupported: " );
590 }
591
592 return memberExpr->member.strict_as< ast::NameExpr >()->name;
593 }
594
595 /// Actually visits expressions to find their candidate interpretations
596 class Finder final : public ast::WithShortCircuiting {
597 const ResolveContext & context;
598 const ast::SymbolTable & symtab;
599 public:
600 // static size_t traceId;
601 CandidateFinder & selfFinder;
602 CandidateList & candidates;
603 const ast::TypeEnvironment & tenv;
604 ast::ptr< ast::Type > & targetType;
605
606 enum Errors {
607 NotFound,
608 NoMatch,
609 ArgsToFew,
610 ArgsToMany,
611 RetsToFew,
612 RetsToMany,
613 NoReason
614 };
615
616 struct {
617 Errors code = NotFound;
618 } reason;
619
620 Finder( CandidateFinder & f )
621 : context( f.context ), symtab( context.symtab ), selfFinder( f ),
622 candidates( f.candidates ), tenv( f.env ), targetType( f.targetType ) {}
623
624 void previsit( const ast::Node * ) { visit_children = false; }
625
626 /// Convenience to add candidate to list
627 template<typename... Args>
628 void addCandidate( Args &&... args ) {
629 candidates.emplace_back( new Candidate{ std::forward<Args>( args )... } );
630 reason.code = NoReason;
631 }
632
633 void postvisit( const ast::ApplicationExpr * applicationExpr ) {
634 addCandidate( applicationExpr, tenv );
635 }
636
637 /// Set up candidate assertions for inference
638 void inferParameters( CandidateRef & newCand, CandidateList & out ) {
639 // Set need bindings for any unbound assertions
640 UniqueId crntResnSlot = 0; // matching ID for this expression's assertions
641 for ( auto & assn : newCand->need ) {
642 // skip already-matched assertions
643 if ( assn.second.resnSlot != 0 ) continue;
644 // assign slot for expression if needed
645 if ( crntResnSlot == 0 ) { crntResnSlot = ++globalResnSlot; }
646 // fix slot to assertion
647 assn.second.resnSlot = crntResnSlot;
648 }
649 // pair slot to expression
650 if ( crntResnSlot != 0 ) {
651 newCand->expr.get_and_mutate()->inferred.resnSlots().emplace_back( crntResnSlot );
652 }
653
654 // add to output list; assertion satisfaction will occur later
655 out.emplace_back( newCand );
656 }
657
658 /// Completes a function candidate with arguments located
659 void validateFunctionCandidate(
660 const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results,
661 CandidateList & out
662 ) {
663 ast::ApplicationExpr * appExpr =
664 new ast::ApplicationExpr{ func->expr->location, func->expr };
665 // sum cost and accumulate arguments
666 std::deque< const ast::Expr * > args;
667 Cost cost = func->cost;
668 const ArgPack * pack = &result;
669 while ( pack->expr ) {
670 args.emplace_front( pack->expr );
671 cost += pack->cost;
672 pack = &results[pack->parent];
673 }
674 std::vector< ast::ptr< ast::Expr > > vargs( args.begin(), args.end() );
675 appExpr->args = std::move( vargs );
676 // build and validate new candidate
677 auto newCand =
678 std::make_shared<Candidate>( appExpr, result.env, result.open, result.need, cost );
679 PRINT(
680 std::cerr << "instantiate function success: " << appExpr << std::endl;
681 std::cerr << "need assertions:" << std::endl;
682 ast::print( std::cerr, result.need, 2 );
683 )
684 inferParameters( newCand, out );
685 }
686
687 /// Builds a list of candidates for a function, storing them in out
688 void makeFunctionCandidates(
689 const CandidateRef & func, const ast::FunctionType * funcType,
690 const ExplodedArgs_new & args, CandidateList & out
691 ) {
692 ast::OpenVarSet funcOpen;
693 ast::AssertionSet funcNeed, funcHave;
694 ast::TypeEnvironment funcEnv{ func->env };
695 makeUnifiableVars( funcType, funcOpen, funcNeed );
696 // add all type variables as open variables now so that those not used in the
697 // parameter list are still considered open
698 funcEnv.add( funcType->forall );
699
700 if ( targetType && ! targetType->isVoid() && ! funcType->returns.empty() ) {
701 // attempt to narrow based on expected target type
702 const ast::Type * returnType = funcType->returns.front();
703 if ( selfFinder.strictMode ) {
704 if ( ! unifyExact(
705 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, noWiden(), symtab ) // xxx - is no widening correct?
706 ) {
707 // unification failed, do not pursue this candidate
708 return;
709 }
710 }
711 else {
712 if ( ! unify(
713 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, symtab )
714 ) {
715 // unification failed, do not pursue this candidate
716 return;
717 }
718 }
719 }
720
721 // iteratively build matches, one parameter at a time
722 std::vector< ArgPack > results;
723 results.emplace_back( funcEnv, funcNeed, funcHave, funcOpen );
724 std::size_t genStart = 0;
725
726 // xxx - how to handle default arg after change to ftype representation?
727 if (const ast::VariableExpr * varExpr = func->expr.as<ast::VariableExpr>()) {
728 if (const ast::FunctionDecl * funcDecl = varExpr->var.as<ast::FunctionDecl>()) {
729 // function may have default args only if directly calling by name
730 // must use types on candidate however, due to RenameVars substitution
731 auto nParams = funcType->params.size();
732
733 for (size_t i=0; i<nParams; ++i) {
734 auto obj = funcDecl->params[i].strict_as<ast::ObjectDecl>();
735 if (!instantiateArgument(
736 funcType->params[i], obj->init, args, results, genStart, symtab)) return;
737 }
738 goto endMatch;
739 }
740 }
741 for ( const auto & param : funcType->params ) {
742 // Try adding the arguments corresponding to the current parameter to the existing
743 // matches
744 // no default args for indirect calls
745 if ( ! instantiateArgument(
746 param, nullptr, args, results, genStart, symtab ) ) return;
747 }
748
749 endMatch:
750 if ( funcType->isVarArgs ) {
751 // append any unused arguments to vararg pack
752 std::size_t genEnd;
753 do {
754 genEnd = results.size();
755
756 // iterate results
757 for ( std::size_t i = genStart; i < genEnd; ++i ) {
758 unsigned nextArg = results[i].nextArg;
759
760 // use remainder of exploded tuple if present
761 if ( results[i].hasExpl() ) {
762 const ExplodedArg & expl = results[i].getExpl( args );
763
764 unsigned nextExpl = results[i].nextExpl + 1;
765 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
766
767 results.emplace_back(
768 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
769 copy( results[i].need ), copy( results[i].have ),
770 copy( results[i].open ), nextArg, 0, Cost::zero, nextExpl,
771 results[i].explAlt );
772
773 continue;
774 }
775
776 // finish result when out of arguments
777 if ( nextArg >= args.size() ) {
778 validateFunctionCandidate( func, results[i], results, out );
779
780 continue;
781 }
782
783 // add each possible next argument
784 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
785 const ExplodedArg & expl = args[nextArg][j];
786
787 // fresh copies of parent parameters for this iteration
788 ast::TypeEnvironment env = results[i].env;
789 ast::OpenVarSet open = results[i].open;
790
791 env.addActual( expl.env, open );
792
793 // skip empty tuple arguments by (nearly) cloning parent into next gen
794 if ( expl.exprs.empty() ) {
795 results.emplace_back(
796 results[i], std::move( env ), copy( results[i].need ),
797 copy( results[i].have ), std::move( open ), nextArg + 1,
798 expl.cost );
799
800 continue;
801 }
802
803 // add new result
804 results.emplace_back(
805 i, expl.exprs.front(), std::move( env ), copy( results[i].need ),
806 copy( results[i].have ), std::move( open ), nextArg + 1, 0, expl.cost,
807 expl.exprs.size() == 1 ? 0 : 1, j );
808 }
809 }
810
811 genStart = genEnd;
812 } while( genEnd != results.size() );
813 } else {
814 // filter out the results that don't use all the arguments
815 for ( std::size_t i = genStart; i < results.size(); ++i ) {
816 ArgPack & result = results[i];
817 if ( ! result.hasExpl() && result.nextArg >= args.size() ) {
818 validateFunctionCandidate( func, result, results, out );
819 }
820 }
821 }
822 }
823
824 /// Adds implicit struct-conversions to the alternative list
825 void addAnonConversions( const CandidateRef & cand ) {
826 // adds anonymous member interpretations whenever an aggregate value type is seen.
827 // it's okay for the aggregate expression to have reference type -- cast it to the
828 // base type to treat the aggregate as the referenced value
829 ast::ptr< ast::Expr > aggrExpr( cand->expr );
830 ast::ptr< ast::Type > & aggrType = aggrExpr.get_and_mutate()->result;
831 cand->env.apply( aggrType );
832
833 if ( aggrType.as< ast::ReferenceType >() ) {
834 aggrExpr = new ast::CastExpr{ aggrExpr, aggrType->stripReferences() };
835 }
836
837 if ( auto structInst = aggrExpr->result.as< ast::StructInstType >() ) {
838 addAggMembers( structInst, aggrExpr, *cand, Cost::unsafe, "" );
839 } else if ( auto unionInst = aggrExpr->result.as< ast::UnionInstType >() ) {
840 addAggMembers( unionInst, aggrExpr, *cand, Cost::unsafe, "" );
841 }
842 }
843
844 /// Adds aggregate member interpretations
845 void addAggMembers(
846 const ast::BaseInstType * aggrInst, const ast::Expr * expr,
847 const Candidate & cand, const Cost & addedCost, const std::string & name
848 ) {
849 for ( const ast::Decl * decl : aggrInst->lookup( name ) ) {
850 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( decl );
851 CandidateRef newCand = std::make_shared<Candidate>(
852 cand, new ast::MemberExpr{ expr->location, dwt, expr }, addedCost );
853 // add anonymous member interpretations whenever an aggregate value type is seen
854 // as a member expression
855 addAnonConversions( newCand );
856 candidates.emplace_back( std::move( newCand ) );
857 }
858 }
859
860 /// Adds tuple member interpretations
861 void addTupleMembers(
862 const ast::TupleType * tupleType, const ast::Expr * expr, const Candidate & cand,
863 const Cost & addedCost, const ast::Expr * member
864 ) {
865 if ( auto constantExpr = dynamic_cast< const ast::ConstantExpr * >( member ) ) {
866 // get the value of the constant expression as an int, must be between 0 and the
867 // length of the tuple to have meaning
868 long long val = constantExpr->intValue();
869 if ( val >= 0 && (unsigned long long)val < tupleType->size() ) {
870 addCandidate(
871 cand, new ast::TupleIndexExpr{ expr->location, expr, (unsigned)val },
872 addedCost );
873 }
874 }
875 }
876
877 void postvisit( const ast::UntypedExpr * untypedExpr ) {
878 std::vector< CandidateFinder > argCandidates =
879 selfFinder.findSubExprs( untypedExpr->args );
880
881 // take care of possible tuple assignments
882 // if not tuple assignment, handled as normal function call
883 Tuples::handleTupleAssignment( selfFinder, untypedExpr, argCandidates );
884
885 CandidateFinder funcFinder( context, tenv );
886 if (auto nameExpr = untypedExpr->func.as<ast::NameExpr>()) {
887 auto kind = ast::SymbolTable::getSpecialFunctionKind(nameExpr->name);
888 if (kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS) {
889 assertf(!argCandidates.empty(), "special function call without argument");
890 for (auto & firstArgCand: argCandidates[0]) {
891 ast::ptr<ast::Type> argType = firstArgCand->expr->result;
892 firstArgCand->env.apply(argType);
893 // strip references
894 // xxx - is this correct?
895 while (argType.as<ast::ReferenceType>()) argType = argType.as<ast::ReferenceType>()->base;
896
897 // convert 1-tuple to plain type
898 if (auto tuple = argType.as<ast::TupleType>()) {
899 if (tuple->size() == 1) {
900 argType = tuple->types[0];
901 }
902 }
903
904 // if argType is an unbound type parameter, all special functions need to be searched.
905 if (isUnboundType(argType)) {
906 funcFinder.otypeKeys.clear();
907 break;
908 }
909
910 if (argType.as<ast::PointerType>()) funcFinder.otypeKeys.insert(Mangle::Encoding::pointer);
911 // else if (const ast::EnumInstType * enumInst = argType.as<ast::EnumInstType>()) {
912 // const ast::EnumDecl * enumDecl = enumInst->base; // Here
913 // if ( const ast::Type* enumType = enumDecl->base ) {
914 // // instance of enum (T) is a instance of type (T)
915 // funcFinder.otypeKeys.insert(Mangle::mangle(enumType, Mangle::NoGenericParams | Mangle::Type));
916 // } else {
917 // // instance of an untyped enum is techically int
918 // funcFinder.otypeKeys.insert(Mangle::mangle(enumDecl, Mangle::NoGenericParams | Mangle::Type));
919 // }
920 // }
921 else funcFinder.otypeKeys.insert(Mangle::mangle(argType, Mangle::NoGenericParams | Mangle::Type));
922 }
923 }
924 }
925 // if candidates are already produced, do not fail
926 // xxx - is it possible that handleTupleAssignment and main finder both produce candidates?
927 // this means there exists ctor/assign functions with a tuple as first parameter.
928 ResolvMode mode = {
929 true, // adjust
930 !untypedExpr->func.as<ast::NameExpr>(), // prune if not calling by name
931 selfFinder.candidates.empty() // failfast if other options are not found
932 };
933 funcFinder.find( untypedExpr->func, mode );
934 // short-circuit if no candidates
935 // if ( funcFinder.candidates.empty() ) return;
936
937 reason.code = NoMatch;
938
939 // find function operators
940 ast::ptr< ast::Expr > opExpr = new ast::NameExpr{ untypedExpr->location, "?()" }; // ??? why not ?{}
941 CandidateFinder opFinder( context, tenv );
942 // okay if there aren't any function operations
943 opFinder.find( opExpr, ResolvMode::withoutFailFast() );
944 PRINT(
945 std::cerr << "known function ops:" << std::endl;
946 print( std::cerr, opFinder.candidates, 1 );
947 )
948
949 // pre-explode arguments
950 ExplodedArgs_new argExpansions;
951 for ( const CandidateFinder & args : argCandidates ) {
952 argExpansions.emplace_back();
953 auto & argE = argExpansions.back();
954 for ( const CandidateRef & arg : args ) { argE.emplace_back( *arg, symtab ); }
955 }
956
957 // Find function matches
958 CandidateList found;
959 SemanticErrorException errors;
960 for ( CandidateRef & func : funcFinder ) {
961 try {
962 PRINT(
963 std::cerr << "working on alternative:" << std::endl;
964 print( std::cerr, *func, 2 );
965 )
966
967 // check if the type is a pointer to function
968 const ast::Type * funcResult = func->expr->result->stripReferences();
969 if ( auto pointer = dynamic_cast< const ast::PointerType * >( funcResult ) ) {
970 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
971 // if (!selfFinder.allowVoid && function->returns.empty()) continue;
972 CandidateRef newFunc{ new Candidate{ *func } };
973 newFunc->expr =
974 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
975 makeFunctionCandidates( newFunc, function, argExpansions, found );
976 }
977 } else if (
978 auto inst = dynamic_cast< const ast::TypeInstType * >( funcResult )
979 ) {
980 if ( const ast::EqvClass * clz = func->env.lookup( *inst ) ) {
981 if ( auto function = clz->bound.as< ast::FunctionType >() ) {
982 CandidateRef newFunc{ new Candidate{ *func } };
983 newFunc->expr =
984 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
985 makeFunctionCandidates( newFunc, function, argExpansions, found );
986 }
987 }
988 }
989 } catch ( SemanticErrorException & e ) { errors.append( e ); }
990 }
991
992 // Find matches on function operators `?()`
993 if ( ! opFinder.candidates.empty() ) {
994 // add exploded function alternatives to front of argument list
995 std::vector< ExplodedArg > funcE;
996 funcE.reserve( funcFinder.candidates.size() );
997 for ( const CandidateRef & func : funcFinder ) {
998 funcE.emplace_back( *func, symtab );
999 }
1000 argExpansions.emplace_front( std::move( funcE ) );
1001
1002 for ( const CandidateRef & op : opFinder ) {
1003 try {
1004 // check if type is pointer-to-function
1005 const ast::Type * opResult = op->expr->result->stripReferences();
1006 if ( auto pointer = dynamic_cast< const ast::PointerType * >( opResult ) ) {
1007 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
1008 CandidateRef newOp{ new Candidate{ *op} };
1009 newOp->expr =
1010 referenceToRvalueConversion( newOp->expr, newOp->cost );
1011 makeFunctionCandidates( newOp, function, argExpansions, found );
1012 }
1013 }
1014 } catch ( SemanticErrorException & e ) { errors.append( e ); }
1015 }
1016 }
1017
1018 // Implement SFINAE; resolution errors are only errors if there aren't any non-error
1019 // candidates
1020 if ( found.empty() && ! errors.isEmpty() ) { throw errors; }
1021
1022 // only keep the best matching intrinsic result to match C semantics (no unexpected narrowing/widening)
1023 // TODO: keep one for each set of argument candidates?
1024 Cost intrinsicCost = Cost::infinity;
1025 CandidateList intrinsicResult;
1026
1027 // Compute conversion costs
1028 for ( CandidateRef & withFunc : found ) {
1029 Cost cvtCost = computeApplicationConversionCost( withFunc, symtab );
1030
1031 PRINT(
1032 auto appExpr = withFunc->expr.strict_as< ast::ApplicationExpr >();
1033 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
1034 auto function = pointer->base.strict_as< ast::FunctionType >();
1035
1036 std::cerr << "Case +++++++++++++ " << appExpr->func << std::endl;
1037 std::cerr << "parameters are:" << std::endl;
1038 ast::printAll( std::cerr, function->params, 2 );
1039 std::cerr << "arguments are:" << std::endl;
1040 ast::printAll( std::cerr, appExpr->args, 2 );
1041 std::cerr << "bindings are:" << std::endl;
1042 ast::print( std::cerr, withFunc->env, 2 );
1043 std::cerr << "cost is: " << withFunc->cost << std::endl;
1044 std::cerr << "cost of conversion is:" << cvtCost << std::endl;
1045 )
1046
1047 if ( cvtCost != Cost::infinity ) {
1048 withFunc->cvtCost = cvtCost;
1049 withFunc->cost += cvtCost;
1050 auto func = withFunc->expr.strict_as<ast::ApplicationExpr>()->func.as<ast::VariableExpr>();
1051 if (func && func->var->linkage == ast::Linkage::Intrinsic) {
1052 if (withFunc->cost < intrinsicCost) {
1053 intrinsicResult.clear();
1054 intrinsicCost = withFunc->cost;
1055 }
1056 if (withFunc->cost == intrinsicCost) {
1057 intrinsicResult.emplace_back(std::move(withFunc));
1058 }
1059 }
1060 else {
1061 candidates.emplace_back( std::move( withFunc ) );
1062 }
1063 }
1064 }
1065 spliceBegin( candidates, intrinsicResult );
1066 found = std::move( candidates );
1067
1068 // use a new list so that candidates are not examined by addAnonConversions twice
1069 // CandidateList winners = findMinCost( found );
1070 // promoteCvtCost( winners );
1071
1072 // function may return a struct/union value, in which case we need to add candidates
1073 // for implicit conversions to each of the anonymous members, which must happen after
1074 // `findMinCost`, since anon conversions are never the cheapest
1075 for ( const CandidateRef & c : found ) {
1076 addAnonConversions( c );
1077 }
1078 // would this be too slow when we don't check cost anymore?
1079 spliceBegin( candidates, found );
1080
1081 if ( candidates.empty() && targetType && ! targetType->isVoid() && !selfFinder.strictMode ) {
1082 // If resolution is unsuccessful with a target type, try again without, since it
1083 // will sometimes succeed when it wouldn't with a target type binding.
1084 // For example:
1085 // forall( otype T ) T & ?[]( T *, ptrdiff_t );
1086 // const char * x = "hello world";
1087 // unsigned char ch = x[0];
1088 // Fails with simple return type binding (xxx -- check this!) as follows:
1089 // * T is bound to unsigned char
1090 // * (x: const char *) is unified with unsigned char *, which fails
1091 // xxx -- fix this better
1092 targetType = nullptr;
1093 postvisit( untypedExpr );
1094 }
1095 }
1096
1097 /// true if expression is an lvalue
1098 static bool isLvalue( const ast::Expr * x ) {
1099 return x->result && ( x->get_lvalue() || x->result.as< ast::ReferenceType >() );
1100 }
1101
1102 void postvisit( const ast::AddressExpr * addressExpr ) {
1103 CandidateFinder finder( context, tenv );
1104 finder.find( addressExpr->arg );
1105
1106 if( finder.candidates.empty() ) return;
1107
1108 reason.code = NoMatch;
1109
1110 for ( CandidateRef & r : finder.candidates ) {
1111 if ( ! isLvalue( r->expr ) ) continue;
1112 addCandidate( *r, new ast::AddressExpr{ addressExpr->location, r->expr } );
1113 }
1114 }
1115
1116 void postvisit( const ast::LabelAddressExpr * labelExpr ) {
1117 addCandidate( labelExpr, tenv );
1118 }
1119
1120 void postvisit( const ast::CastExpr * castExpr ) {
1121 ast::ptr< ast::Type > toType = castExpr->result;
1122 assert( toType );
1123 toType = resolveTypeof( toType, context );
1124 toType = adjustExprType( toType, tenv, symtab );
1125
1126 CandidateFinder finder( context, tenv, toType );
1127 if (toType->isVoid()) {
1128 finder.allowVoid = true;
1129 }
1130 if ( castExpr->kind == ast::CastExpr::Return ) {
1131 finder.strictMode = true;
1132 finder.find( castExpr->arg, ResolvMode::withAdjustment() );
1133
1134 // return casts are eliminated (merely selecting an overload, no actual operation)
1135 candidates = std::move(finder.candidates);
1136 }
1137 finder.find( castExpr->arg, ResolvMode::withAdjustment() );
1138
1139 if( !finder.candidates.empty() ) reason.code = NoMatch;
1140
1141 CandidateList matches;
1142 Cost minExprCost = Cost::infinity;
1143 Cost minCastCost = Cost::infinity;
1144 for ( CandidateRef & cand : finder.candidates ) {
1145 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1146 ast::OpenVarSet open( cand->open );
1147
1148 cand->env.extractOpenVars( open );
1149
1150 // It is possible that a cast can throw away some values in a multiply-valued
1151 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of the
1152 // subexpression results that are cast directly. The candidate is invalid if it
1153 // has fewer results than there are types to cast to.
1154 int discardedValues = cand->expr->result->size() - toType->size();
1155 if ( discardedValues < 0 ) continue;
1156
1157 // unification run for side-effects
1158 unify( toType, cand->expr->result, cand->env, need, have, open, symtab );
1159 Cost thisCost =
1160 (castExpr->isGenerated == ast::GeneratedFlag::GeneratedCast)
1161 ? conversionCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env )
1162 : castCost( cand->expr->result, toType, cand->expr->get_lvalue(), symtab, cand->env );
1163
1164 PRINT(
1165 std::cerr << "working on cast with result: " << toType << std::endl;
1166 std::cerr << "and expr type: " << cand->expr->result << std::endl;
1167 std::cerr << "env: " << cand->env << std::endl;
1168 )
1169 if ( thisCost != Cost::infinity ) {
1170 PRINT(
1171 std::cerr << "has finite cost." << std::endl;
1172 )
1173 // count one safe conversion for each value that is thrown away
1174 thisCost.incSafe( discardedValues );
1175 // select first on argument cost, then conversion cost
1176 if (cand->cost < minExprCost || cand->cost == minExprCost && thisCost < minCastCost) {
1177 minExprCost = cand->cost;
1178 minCastCost = thisCost;
1179 matches.clear();
1180
1181
1182 }
1183 // ambiguous case, still output candidates to print in error message
1184 if (cand->cost == minExprCost && thisCost == minCastCost) {
1185 CandidateRef newCand = std::make_shared<Candidate>(
1186 restructureCast( cand->expr, toType, castExpr->isGenerated ),
1187 copy( cand->env ), std::move( open ), std::move( need ), cand->cost + thisCost);
1188 // currently assertions are always resolved immediately so this should have no effect.
1189 // if this somehow changes in the future (e.g. delayed by indeterminate return type)
1190 // we may need to revisit the logic.
1191 inferParameters( newCand, matches );
1192 }
1193 // else skip, better alternatives found
1194
1195 }
1196 }
1197 candidates = std::move(matches);
1198
1199 //CandidateList minArgCost = findMinCost( matches );
1200 //promoteCvtCost( minArgCost );
1201 //candidates = findMinCost( minArgCost );
1202 }
1203
1204 void postvisit( const ast::VirtualCastExpr * castExpr ) {
1205 assertf( castExpr->result, "Implicit virtual cast targets not yet supported." );
1206 CandidateFinder finder( context, tenv );
1207 // don't prune here, all alternatives guaranteed to have same type
1208 finder.find( castExpr->arg, ResolvMode::withoutPrune() );
1209 for ( CandidateRef & r : finder.candidates ) {
1210 addCandidate(
1211 *r,
1212 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
1213 }
1214 }
1215
1216 void postvisit( const ast::KeywordCastExpr * castExpr ) {
1217 const auto & loc = castExpr->location;
1218 assertf( castExpr->result, "Cast target should have been set in Validate." );
1219 auto ref = castExpr->result.strict_as<ast::ReferenceType>();
1220 auto inst = ref->base.strict_as<ast::StructInstType>();
1221 auto target = inst->base.get();
1222
1223 CandidateFinder finder( context, tenv );
1224
1225 auto pick_alternatives = [target, this](CandidateList & found, bool expect_ref) {
1226 for(auto & cand : found) {
1227 const ast::Type * expr = cand->expr->result.get();
1228 if(expect_ref) {
1229 auto res = dynamic_cast<const ast::ReferenceType*>(expr);
1230 if(!res) { continue; }
1231 expr = res->base.get();
1232 }
1233
1234 if(auto insttype = dynamic_cast<const ast::TypeInstType*>(expr)) {
1235 auto td = cand->env.lookup(*insttype);
1236 if(!td) { continue; }
1237 expr = td->bound.get();
1238 }
1239
1240 if(auto base = dynamic_cast<const ast::StructInstType*>(expr)) {
1241 if(base->base == target) {
1242 candidates.push_back( std::move(cand) );
1243 reason.code = NoReason;
1244 }
1245 }
1246 }
1247 };
1248
1249 try {
1250 // Attempt 1 : turn (thread&)X into (thread$&)X.__thrd
1251 // Clone is purely for memory management
1252 std::unique_ptr<const ast::Expr> tech1 { new ast::UntypedMemberExpr(loc, new ast::NameExpr(loc, castExpr->concrete_target.field), castExpr->arg) };
1253
1254 // don't prune here, since it's guaranteed all alternatives will have the same type
1255 finder.find( tech1.get(), ResolvMode::withoutPrune() );
1256 pick_alternatives(finder.candidates, false);
1257
1258 return;
1259 } catch(SemanticErrorException & ) {}
1260
1261 // Fallback : turn (thread&)X into (thread$&)get_thread(X)
1262 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 })) };
1263 // don't prune here, since it's guaranteed all alternatives will have the same type
1264 finder.find( fallback.get(), ResolvMode::withoutPrune() );
1265
1266 pick_alternatives(finder.candidates, true);
1267
1268 // Whatever happens here, we have no more fallbacks
1269 }
1270
1271 void postvisit( const ast::UntypedMemberExpr * memberExpr ) {
1272 CandidateFinder aggFinder( context, tenv );
1273 aggFinder.find( memberExpr->aggregate, ResolvMode::withAdjustment() );
1274 for ( CandidateRef & agg : aggFinder.candidates ) {
1275 // it's okay for the aggregate expression to have reference type -- cast it to the
1276 // base type to treat the aggregate as the referenced value
1277 Cost addedCost = Cost::zero;
1278 agg->expr = referenceToRvalueConversion( agg->expr, addedCost );
1279
1280 // find member of the given type
1281 if ( auto structInst = agg->expr->result.as< ast::StructInstType >() ) {
1282 addAggMembers(
1283 structInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1284 } else if ( auto unionInst = agg->expr->result.as< ast::UnionInstType >() ) {
1285 addAggMembers(
1286 unionInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1287 } else if ( auto tupleType = agg->expr->result.as< ast::TupleType >() ) {
1288 addTupleMembers( tupleType, agg->expr, *agg, addedCost, memberExpr->member );
1289 }
1290 }
1291 }
1292
1293 void postvisit( const ast::MemberExpr * memberExpr ) {
1294 addCandidate( memberExpr, tenv );
1295 }
1296
1297 void postvisit( const ast::NameExpr * nameExpr ) {
1298 std::vector< ast::SymbolTable::IdData > declList;
1299 if (!selfFinder.otypeKeys.empty()) {
1300 auto kind = ast::SymbolTable::getSpecialFunctionKind(nameExpr->name);
1301 assertf(kind != ast::SymbolTable::SpecialFunctionKind::NUMBER_OF_KINDS, "special lookup with non-special target: %s", nameExpr->name.c_str());
1302
1303 for (auto & otypeKey: selfFinder.otypeKeys) {
1304 auto result = symtab.specialLookupId(kind, otypeKey);
1305 declList.insert(declList.end(), std::make_move_iterator(result.begin()), std::make_move_iterator(result.end()));
1306 }
1307 }
1308 else {
1309 declList = symtab.lookupId( nameExpr->name );
1310 }
1311 PRINT( std::cerr << "nameExpr is " << nameExpr->name << std::endl; )
1312
1313 if( declList.empty() ) return;
1314
1315 reason.code = NoMatch;
1316
1317 for ( auto & data : declList ) {
1318 Cost cost = Cost::zero;
1319 ast::Expr * newExpr = data.combine( nameExpr->location, cost );
1320
1321 CandidateRef newCand = std::make_shared<Candidate>(
1322 newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, cost );
1323
1324 if (newCand->expr->env) {
1325 newCand->env.add(*newCand->expr->env);
1326 auto mutExpr = newCand->expr.get_and_mutate();
1327 mutExpr->env = nullptr;
1328 newCand->expr = mutExpr;
1329 }
1330
1331 PRINT(
1332 std::cerr << "decl is ";
1333 ast::print( std::cerr, data.id );
1334 std::cerr << std::endl;
1335 std::cerr << "newExpr is ";
1336 ast::print( std::cerr, newExpr );
1337 std::cerr << std::endl;
1338 )
1339 newCand->expr = ast::mutate_field(
1340 newCand->expr.get(), &ast::Expr::result,
1341 renameTyVars( newCand->expr->result ) );
1342 // add anonymous member interpretations whenever an aggregate value type is seen
1343 // as a name expression
1344 addAnonConversions( newCand );
1345 candidates.emplace_back( std::move( newCand ) );
1346 }
1347 }
1348
1349 void postvisit( const ast::VariableExpr * variableExpr ) {
1350 // not sufficient to just pass `variableExpr` here, type might have changed since
1351 // creation
1352 addCandidate(
1353 new ast::VariableExpr{ variableExpr->location, variableExpr->var }, tenv );
1354 }
1355
1356 void postvisit( const ast::ConstantExpr * constantExpr ) {
1357 addCandidate( constantExpr, tenv );
1358 }
1359
1360 void postvisit( const ast::SizeofExpr * sizeofExpr ) {
1361 if ( sizeofExpr->type ) {
1362 addCandidate(
1363 new ast::SizeofExpr{
1364 sizeofExpr->location, resolveTypeof( sizeofExpr->type, context ) },
1365 tenv );
1366 } else {
1367 // find all candidates for the argument to sizeof
1368 CandidateFinder finder( context, tenv );
1369 finder.find( sizeofExpr->expr );
1370 // find the lowest-cost candidate, otherwise ambiguous
1371 CandidateList winners = findMinCost( finder.candidates );
1372 if ( winners.size() != 1 ) {
1373 SemanticError(
1374 sizeofExpr->expr.get(), "Ambiguous expression in sizeof operand: " );
1375 }
1376 // return the lowest-cost candidate
1377 CandidateRef & choice = winners.front();
1378 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1379 choice->cost = Cost::zero;
1380 addCandidate( *choice, new ast::SizeofExpr{ sizeofExpr->location, choice->expr } );
1381 }
1382 }
1383
1384 void postvisit( const ast::AlignofExpr * alignofExpr ) {
1385 if ( alignofExpr->type ) {
1386 addCandidate(
1387 new ast::AlignofExpr{
1388 alignofExpr->location, resolveTypeof( alignofExpr->type, context ) },
1389 tenv );
1390 } else {
1391 // find all candidates for the argument to alignof
1392 CandidateFinder finder( context, tenv );
1393 finder.find( alignofExpr->expr );
1394 // find the lowest-cost candidate, otherwise ambiguous
1395 CandidateList winners = findMinCost( finder.candidates );
1396 if ( winners.size() != 1 ) {
1397 SemanticError(
1398 alignofExpr->expr.get(), "Ambiguous expression in alignof operand: " );
1399 }
1400 // return the lowest-cost candidate
1401 CandidateRef & choice = winners.front();
1402 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1403 choice->cost = Cost::zero;
1404 addCandidate(
1405 *choice, new ast::AlignofExpr{ alignofExpr->location, choice->expr } );
1406 }
1407 }
1408
1409 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
1410 const ast::BaseInstType * aggInst;
1411 if (( aggInst = offsetofExpr->type.as< ast::StructInstType >() )) ;
1412 else if (( aggInst = offsetofExpr->type.as< ast::UnionInstType >() )) ;
1413 else return;
1414
1415 for ( const ast::Decl * member : aggInst->lookup( offsetofExpr->member ) ) {
1416 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( member );
1417 addCandidate(
1418 new ast::OffsetofExpr{ offsetofExpr->location, aggInst, dwt }, tenv );
1419 }
1420 }
1421
1422 void postvisit( const ast::OffsetofExpr * offsetofExpr ) {
1423 addCandidate( offsetofExpr, tenv );
1424 }
1425
1426 void postvisit( const ast::OffsetPackExpr * offsetPackExpr ) {
1427 addCandidate( offsetPackExpr, tenv );
1428 }
1429
1430 void postvisit( const ast::LogicalExpr * logicalExpr ) {
1431 CandidateFinder finder1( context, tenv );
1432 finder1.find( logicalExpr->arg1, ResolvMode::withAdjustment() );
1433 if ( finder1.candidates.empty() ) return;
1434
1435 CandidateFinder finder2( context, tenv );
1436 finder2.find( logicalExpr->arg2, ResolvMode::withAdjustment() );
1437 if ( finder2.candidates.empty() ) return;
1438
1439 reason.code = NoMatch;
1440
1441 for ( const CandidateRef & r1 : finder1.candidates ) {
1442 for ( const CandidateRef & r2 : finder2.candidates ) {
1443 ast::TypeEnvironment env{ r1->env };
1444 env.simpleCombine( r2->env );
1445 ast::OpenVarSet open{ r1->open };
1446 mergeOpenVars( open, r2->open );
1447 ast::AssertionSet need;
1448 mergeAssertionSet( need, r1->need );
1449 mergeAssertionSet( need, r2->need );
1450
1451 addCandidate(
1452 new ast::LogicalExpr{
1453 logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
1454 std::move( env ), std::move( open ), std::move( need ), r1->cost + r2->cost );
1455 }
1456 }
1457 }
1458
1459 void postvisit( const ast::ConditionalExpr * conditionalExpr ) {
1460 // candidates for condition
1461 CandidateFinder finder1( context, tenv );
1462 finder1.find( conditionalExpr->arg1, ResolvMode::withAdjustment() );
1463 if ( finder1.candidates.empty() ) return;
1464
1465 // candidates for true result
1466 CandidateFinder finder2( context, tenv );
1467 finder2.allowVoid = true;
1468 finder2.find( conditionalExpr->arg2, ResolvMode::withAdjustment() );
1469 if ( finder2.candidates.empty() ) return;
1470
1471 // candidates for false result
1472 CandidateFinder finder3( context, tenv );
1473 finder3.allowVoid = true;
1474 finder3.find( conditionalExpr->arg3, ResolvMode::withAdjustment() );
1475 if ( finder3.candidates.empty() ) return;
1476
1477 reason.code = NoMatch;
1478
1479 for ( const CandidateRef & r1 : finder1.candidates ) {
1480 for ( const CandidateRef & r2 : finder2.candidates ) {
1481 for ( const CandidateRef & r3 : finder3.candidates ) {
1482 ast::TypeEnvironment env{ r1->env };
1483 env.simpleCombine( r2->env );
1484 env.simpleCombine( r3->env );
1485 ast::OpenVarSet open{ r1->open };
1486 mergeOpenVars( open, r2->open );
1487 mergeOpenVars( open, r3->open );
1488 ast::AssertionSet need;
1489 mergeAssertionSet( need, r1->need );
1490 mergeAssertionSet( need, r2->need );
1491 mergeAssertionSet( need, r3->need );
1492 ast::AssertionSet have;
1493
1494 // unify true and false results, then infer parameters to produce new
1495 // candidates
1496 ast::ptr< ast::Type > common;
1497 if (
1498 unify(
1499 r2->expr->result, r3->expr->result, env, need, have, open, symtab,
1500 common )
1501 ) {
1502 // generate typed expression
1503 ast::ConditionalExpr * newExpr = new ast::ConditionalExpr{
1504 conditionalExpr->location, r1->expr, r2->expr, r3->expr };
1505 newExpr->result = common ? common : r2->expr->result;
1506 // convert both options to result type
1507 Cost cost = r1->cost + r2->cost + r3->cost;
1508 newExpr->arg2 = computeExpressionConversionCost(
1509 newExpr->arg2, newExpr->result, symtab, env, cost );
1510 newExpr->arg3 = computeExpressionConversionCost(
1511 newExpr->arg3, newExpr->result, symtab, env, cost );
1512 // output candidate
1513 CandidateRef newCand = std::make_shared<Candidate>(
1514 newExpr, std::move( env ), std::move( open ), std::move( need ), cost );
1515 inferParameters( newCand, candidates );
1516 }
1517 }
1518 }
1519 }
1520 }
1521
1522 void postvisit( const ast::CommaExpr * commaExpr ) {
1523 ast::TypeEnvironment env{ tenv };
1524 ast::ptr< ast::Expr > arg1 = resolveInVoidContext( commaExpr->arg1, context, env );
1525
1526 CandidateFinder finder2( context, env );
1527 finder2.find( commaExpr->arg2, ResolvMode::withAdjustment() );
1528
1529 for ( const CandidateRef & r2 : finder2.candidates ) {
1530 addCandidate( *r2, new ast::CommaExpr{ commaExpr->location, arg1, r2->expr } );
1531 }
1532 }
1533
1534 void postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr ) {
1535 addCandidate( ctorExpr, tenv );
1536 }
1537
1538 void postvisit( const ast::ConstructorExpr * ctorExpr ) {
1539 CandidateFinder finder( context, tenv );
1540 finder.allowVoid = true;
1541 finder.find( ctorExpr->callExpr, ResolvMode::withoutPrune() );
1542 for ( CandidateRef & r : finder.candidates ) {
1543 addCandidate( *r, new ast::ConstructorExpr{ ctorExpr->location, r->expr } );
1544 }
1545 }
1546
1547 void postvisit( const ast::RangeExpr * rangeExpr ) {
1548 // resolve low and high, accept candidates where low and high types unify
1549 CandidateFinder finder1( context, tenv );
1550 finder1.find( rangeExpr->low, ResolvMode::withAdjustment() );
1551 if ( finder1.candidates.empty() ) return;
1552
1553 CandidateFinder finder2( context, tenv );
1554 finder2.find( rangeExpr->high, ResolvMode::withAdjustment() );
1555 if ( finder2.candidates.empty() ) return;
1556
1557 reason.code = NoMatch;
1558
1559 for ( const CandidateRef & r1 : finder1.candidates ) {
1560 for ( const CandidateRef & r2 : finder2.candidates ) {
1561 ast::TypeEnvironment env{ r1->env };
1562 env.simpleCombine( r2->env );
1563 ast::OpenVarSet open{ r1->open };
1564 mergeOpenVars( open, r2->open );
1565 ast::AssertionSet need;
1566 mergeAssertionSet( need, r1->need );
1567 mergeAssertionSet( need, r2->need );
1568 ast::AssertionSet have;
1569
1570 ast::ptr< ast::Type > common;
1571 if (
1572 unify(
1573 r1->expr->result, r2->expr->result, env, need, have, open, symtab,
1574 common )
1575 ) {
1576 // generate new expression
1577 ast::RangeExpr * newExpr =
1578 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1579 newExpr->result = common ? common : r1->expr->result;
1580 // add candidate
1581 CandidateRef newCand = std::make_shared<Candidate>(
1582 newExpr, std::move( env ), std::move( open ), std::move( need ),
1583 r1->cost + r2->cost );
1584 inferParameters( newCand, candidates );
1585 }
1586 }
1587 }
1588 }
1589
1590 void postvisit( const ast::UntypedTupleExpr * tupleExpr ) {
1591 std::vector< CandidateFinder > subCandidates =
1592 selfFinder.findSubExprs( tupleExpr->exprs );
1593 std::vector< CandidateList > possibilities;
1594 combos( subCandidates.begin(), subCandidates.end(), back_inserter( possibilities ) );
1595
1596 for ( const CandidateList & subs : possibilities ) {
1597 std::vector< ast::ptr< ast::Expr > > exprs;
1598 exprs.reserve( subs.size() );
1599 for ( const CandidateRef & sub : subs ) { exprs.emplace_back( sub->expr ); }
1600
1601 ast::TypeEnvironment env;
1602 ast::OpenVarSet open;
1603 ast::AssertionSet need;
1604 for ( const CandidateRef & sub : subs ) {
1605 env.simpleCombine( sub->env );
1606 mergeOpenVars( open, sub->open );
1607 mergeAssertionSet( need, sub->need );
1608 }
1609
1610 addCandidate(
1611 new ast::TupleExpr{ tupleExpr->location, std::move( exprs ) },
1612 std::move( env ), std::move( open ), std::move( need ), sumCost( subs ) );
1613 }
1614 }
1615
1616 void postvisit( const ast::TupleExpr * tupleExpr ) {
1617 addCandidate( tupleExpr, tenv );
1618 }
1619
1620 void postvisit( const ast::TupleIndexExpr * tupleExpr ) {
1621 addCandidate( tupleExpr, tenv );
1622 }
1623
1624 void postvisit( const ast::TupleAssignExpr * tupleExpr ) {
1625 addCandidate( tupleExpr, tenv );
1626 }
1627
1628 void postvisit( const ast::UniqueExpr * unqExpr ) {
1629 CandidateFinder finder( context, tenv );
1630 finder.find( unqExpr->expr, ResolvMode::withAdjustment() );
1631 for ( CandidateRef & r : finder.candidates ) {
1632 // ensure that the the id is passed on so that the expressions are "linked"
1633 addCandidate( *r, new ast::UniqueExpr{ unqExpr->location, r->expr, unqExpr->id } );
1634 }
1635 }
1636
1637 void postvisit( const ast::StmtExpr * stmtExpr ) {
1638 addCandidate( resolveStmtExpr( stmtExpr, context ), tenv );
1639 }
1640
1641 void postvisit( const ast::UntypedInitExpr * initExpr ) {
1642 // handle each option like a cast
1643 CandidateList matches;
1644 PRINT(
1645 std::cerr << "untyped init expr: " << initExpr << std::endl;
1646 )
1647 // O(n^2) checks of d-types with e-types
1648 for ( const ast::InitAlternative & initAlt : initExpr->initAlts ) {
1649 // calculate target type
1650 const ast::Type * toType = resolveTypeof( initAlt.type, context );
1651 toType = adjustExprType( toType, tenv, symtab );
1652 // The call to find must occur inside this loop, otherwise polymorphic return
1653 // types are not bound to the initialization type, since return type variables are
1654 // only open for the duration of resolving the UntypedExpr.
1655 CandidateFinder finder( context, tenv, toType );
1656 finder.find( initExpr->expr, ResolvMode::withAdjustment() );
1657
1658 Cost minExprCost = Cost::infinity;
1659 Cost minCastCost = Cost::infinity;
1660 for ( CandidateRef & cand : finder.candidates ) {
1661 if(reason.code == NotFound) reason.code = NoMatch;
1662
1663 ast::TypeEnvironment env{ cand->env };
1664 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1665 ast::OpenVarSet open{ cand->open };
1666
1667 PRINT(
1668 std::cerr << " @ " << toType << " " << initAlt.designation << std::endl;
1669 )
1670
1671 // It is possible that a cast can throw away some values in a multiply-valued
1672 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of
1673 // the subexpression results that are cast directly. The candidate is invalid
1674 // if it has fewer results than there are types to cast to.
1675 int discardedValues = cand->expr->result->size() - toType->size();
1676 if ( discardedValues < 0 ) continue;
1677
1678 // unification run for side-effects
1679 bool canUnify = unify( toType, cand->expr->result, env, need, have, open, symtab );
1680 (void) canUnify;
1681 Cost thisCost = computeConversionCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1682 symtab, env );
1683 PRINT(
1684 Cost legacyCost = castCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1685 symtab, env );
1686 std::cerr << "Considering initialization:";
1687 std::cerr << std::endl << " FROM: " << cand->expr->result << std::endl;
1688 std::cerr << std::endl << " TO: " << toType << std::endl;
1689 std::cerr << std::endl << " Unification " << (canUnify ? "succeeded" : "failed");
1690 std::cerr << std::endl << " Legacy cost " << legacyCost;
1691 std::cerr << std::endl << " New cost " << thisCost;
1692 std::cerr << std::endl;
1693 )
1694 if ( thisCost != Cost::infinity ) {
1695 // count one safe conversion for each value that is thrown away
1696 thisCost.incSafe( discardedValues );
1697 if (cand->cost < minExprCost || cand->cost == minExprCost && thisCost < minCastCost) {
1698 minExprCost = cand->cost;
1699 minCastCost = thisCost;
1700 matches.clear();
1701 }
1702 // ambiguous case, still output candidates to print in error message
1703 if (cand->cost == minExprCost && thisCost == minCastCost) {
1704 CandidateRef newCand = std::make_shared<Candidate>(
1705 new ast::InitExpr{
1706 initExpr->location, restructureCast( cand->expr, toType ),
1707 initAlt.designation },
1708 std::move(env), std::move( open ), std::move( need ), cand->cost + thisCost );
1709 // currently assertions are always resolved immediately so this should have no effect.
1710 // if this somehow changes in the future (e.g. delayed by indeterminate return type)
1711 // we may need to revisit the logic.
1712 inferParameters( newCand, matches );
1713 }
1714
1715 }
1716
1717 }
1718
1719 }
1720
1721 // select first on argument cost, then conversion cost
1722 // CandidateList minArgCost = findMinCost( matches );
1723 // promoteCvtCost( minArgCost );
1724 // candidates = findMinCost( minArgCost );
1725 candidates = std::move(matches);
1726 }
1727
1728 void postvisit( const ast::InitExpr * ) {
1729 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
1730 }
1731
1732 void postvisit( const ast::DeletedExpr * ) {
1733 assertf( false, "CandidateFinder should never see a DeletedExpr." );
1734 }
1735
1736 void postvisit( const ast::GenericExpr * ) {
1737 assertf( false, "_Generic is not yet supported." );
1738 }
1739 };
1740
1741 // size_t Finder::traceId = Stats::Heap::new_stacktrace_id("Finder");
1742 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1743 /// return type. Skips ambiguous candidates.
1744
1745} // anonymous namespace
1746
1747bool CandidateFinder::pruneCandidates( CandidateList & candidates, CandidateList & out, std::vector<std::string> & errors ) {
1748 struct PruneStruct {
1749 CandidateRef candidate;
1750 bool ambiguous;
1751
1752 PruneStruct() = default;
1753 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1754 };
1755
1756 // find lowest-cost candidate for each type
1757 std::unordered_map< std::string, PruneStruct > selected;
1758 // attempt to skip satisfyAssertions on more expensive alternatives if better options have been found
1759 std::sort(candidates.begin(), candidates.end(), [](const CandidateRef & x, const CandidateRef & y){return x->cost < y->cost;});
1760 for ( CandidateRef & candidate : candidates ) {
1761 std::string mangleName;
1762 {
1763 ast::ptr< ast::Type > newType = candidate->expr->result;
1764 assertf(candidate->expr->result, "Result of expression %p for candidate is null", candidate->expr.get());
1765 candidate->env.apply( newType );
1766 mangleName = Mangle::mangle( newType );
1767 }
1768
1769 auto found = selected.find( mangleName );
1770 if (found != selected.end() && found->second.candidate->cost < candidate->cost) {
1771 PRINT(
1772 std::cerr << "cost " << candidate->cost << " loses to "
1773 << found->second.candidate->cost << std::endl;
1774 )
1775 continue;
1776 }
1777
1778 // xxx - when do satisfyAssertions produce more than 1 result?
1779 // this should only happen when initial result type contains
1780 // unbound type parameters, then it should never be pruned by
1781 // the previous step, since renameTyVars guarantees the mangled name
1782 // is unique.
1783 CandidateList satisfied;
1784 bool needRecomputeKey = false;
1785 if (candidate->need.empty()) {
1786 satisfied.emplace_back(candidate);
1787 }
1788 else {
1789 satisfyAssertions(candidate, context.symtab, satisfied, errors);
1790 needRecomputeKey = true;
1791 }
1792
1793 for (auto & newCand : satisfied) {
1794 // recomputes type key, if satisfyAssertions changed it
1795 if (needRecomputeKey)
1796 {
1797 ast::ptr< ast::Type > newType = newCand->expr->result;
1798 assertf(newCand->expr->result, "Result of expression %p for candidate is null", newCand->expr.get());
1799 newCand->env.apply( newType );
1800 mangleName = Mangle::mangle( newType );
1801 }
1802 auto found = selected.find( mangleName );
1803 if ( found != selected.end() ) {
1804 // tiebreaking by picking the lower cost on CURRENT expression
1805 // NOTE: this behavior is different from C semantics.
1806 // Specific remediations are performed for C operators at postvisit(UntypedExpr).
1807 // Further investigations may take place.
1808 if ( newCand->cost < found->second.candidate->cost
1809 || (newCand->cost == found->second.candidate->cost && newCand->cvtCost < found->second.candidate->cvtCost) ) {
1810 PRINT(
1811 std::cerr << "cost " << newCand->cost << " beats "
1812 << found->second.candidate->cost << std::endl;
1813 )
1814
1815 found->second = PruneStruct{ newCand };
1816 } else if ( newCand->cost == found->second.candidate->cost && newCand->cvtCost == found->second.candidate->cvtCost) {
1817 // if one of the candidates contains a deleted identifier, can pick the other,
1818 // since deleted expressions should not be ambiguous if there is another option
1819 // that is at least as good
1820 if ( findDeletedExpr( newCand->expr ) ) {
1821 // do nothing
1822 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1823 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1824 PRINT( std::cerr << "current is deleted" << std::endl; )
1825 found->second = PruneStruct{ newCand };
1826 } else {
1827 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1828 found->second.ambiguous = true;
1829 }
1830 } else {
1831 // xxx - can satisfyAssertions increase the cost?
1832 PRINT(
1833 std::cerr << "cost " << newCand->cost << " loses to "
1834 << found->second.candidate->cost << std::endl;
1835 )
1836 }
1837 } else {
1838 selected.emplace_hint( found, mangleName, newCand );
1839 }
1840 }
1841 }
1842
1843 // report unambiguous min-cost candidates
1844 // CandidateList out;
1845 for ( auto & target : selected ) {
1846 if ( target.second.ambiguous ) continue;
1847
1848 CandidateRef cand = target.second.candidate;
1849
1850 ast::ptr< ast::Type > newResult = cand->expr->result;
1851 cand->env.applyFree( newResult );
1852 cand->expr = ast::mutate_field(
1853 cand->expr.get(), &ast::Expr::result, std::move( newResult ) );
1854
1855 out.emplace_back( cand );
1856 }
1857 // if everything is lost in satisfyAssertions, report the error
1858 return !selected.empty();
1859}
1860
1861void CandidateFinder::find( const ast::Expr * expr, ResolvMode mode ) {
1862 // Find alternatives for expression
1863 ast::Pass<Finder> finder{ *this };
1864 expr->accept( finder );
1865
1866 if ( mode.failFast && candidates.empty() ) {
1867 switch(finder.core.reason.code) {
1868 case Finder::NotFound:
1869 { SemanticError( expr, "No alternatives for expression " ); break; }
1870 case Finder::NoMatch:
1871 { SemanticError( expr, "Invalid application of existing declaration(s) in expression " ); break; }
1872 case Finder::ArgsToFew:
1873 case Finder::ArgsToMany:
1874 case Finder::RetsToFew:
1875 case Finder::RetsToMany:
1876 case Finder::NoReason:
1877 default:
1878 { SemanticError( expr->location, "No reasonable alternatives for expression : reasons unkown" ); }
1879 }
1880 }
1881
1882 /*
1883 if ( mode.satisfyAssns || mode.prune ) {
1884 // trim candidates to just those where the assertions are satisfiable
1885 // - necessary pre-requisite to pruning
1886 CandidateList satisfied;
1887 std::vector< std::string > errors;
1888 for ( CandidateRef & candidate : candidates ) {
1889 satisfyAssertions( candidate, localSyms, satisfied, errors );
1890 }
1891
1892 // fail early if none such
1893 if ( mode.failFast && satisfied.empty() ) {
1894 std::ostringstream stream;
1895 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1896 for ( const auto& err : errors ) {
1897 stream << err;
1898 }
1899 SemanticError( expr->location, stream.str() );
1900 }
1901
1902 // reset candidates
1903 candidates = move( satisfied );
1904 }
1905 */
1906
1907 // if ( mode.prune ) {
1908 // optimization: don't prune for NameExpr since it never has cost
1909 if ( mode.prune && !dynamic_cast<const ast::NameExpr *>(expr)) {
1910 // trim candidates to single best one
1911 PRINT(
1912 std::cerr << "alternatives before prune:" << std::endl;
1913 print( std::cerr, candidates );
1914 )
1915
1916 CandidateList pruned;
1917 std::vector<std::string> errors;
1918 bool found = pruneCandidates( candidates, pruned, errors );
1919
1920 if ( mode.failFast && pruned.empty() ) {
1921 std::ostringstream stream;
1922 if (found) {
1923 CandidateList winners = findMinCost( candidates );
1924 stream << "Cannot choose between " << winners.size() << " alternatives for "
1925 "expression\n";
1926 ast::print( stream, expr );
1927 stream << " Alternatives are:\n";
1928 print( stream, winners, 1 );
1929 SemanticError( expr->location, stream.str() );
1930 }
1931 else {
1932 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1933 for ( const auto& err : errors ) {
1934 stream << err;
1935 }
1936 SemanticError( expr->location, stream.str() );
1937 }
1938 }
1939
1940 auto oldsize = candidates.size();
1941 candidates = std::move( pruned );
1942
1943 PRINT(
1944 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
1945 )
1946 PRINT(
1947 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
1948 << std::endl;
1949 )
1950 }
1951
1952 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
1953 // adjusted
1954 if ( mode.adjust ) {
1955 for ( CandidateRef & r : candidates ) {
1956 r->expr = ast::mutate_field(
1957 r->expr.get(), &ast::Expr::result,
1958 adjustExprType( r->expr->result, r->env, context.symtab ) );
1959 }
1960 }
1961
1962 // Central location to handle gcc extension keyword, etc. for all expressions
1963 for ( CandidateRef & r : candidates ) {
1964 if ( r->expr->extension != expr->extension ) {
1965 r->expr.get_and_mutate()->extension = expr->extension;
1966 }
1967 }
1968}
1969
1970std::vector< CandidateFinder > CandidateFinder::findSubExprs(
1971 const std::vector< ast::ptr< ast::Expr > > & xs
1972) {
1973 std::vector< CandidateFinder > out;
1974
1975 for ( const auto & x : xs ) {
1976 out.emplace_back( context, env );
1977 out.back().find( x, ResolvMode::withAdjustment() );
1978
1979 PRINT(
1980 std::cerr << "findSubExprs" << std::endl;
1981 print( std::cerr, out.back().candidates );
1982 )
1983 }
1984
1985 return out;
1986}
1987
1988} // namespace ResolvExpr
1989
1990// Local Variables: //
1991// tab-width: 4 //
1992// mode: c++ //
1993// compile-command: "make install" //
1994// End: //
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