source: src/ResolvExpr/CandidateFinder.cpp@ 396b830

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation new-ast new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 396b830 was cf32116, checked in by Andrew Beach <ajbeach@…>, 6 years ago

Implemented expression based lvalue resolution on new ast.
  • Property mode set to 100644
File size: 59.4 KB
Line 
1//
2// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
3//
4// The contents of this file are covered under the licence agreement in the
5// file "LICENCE" distributed with Cforall.
6//
7// CandidateFinder.cpp --
8//
9// Author : Aaron B. Moss
10// Created On : Wed Jun 5 14:30:00 2019
11// Last Modified By : Andrew Beach
12// Last Modified On : Tue Oct 1 14:55:00 2019
13// Update Count : 2
14//
15
16#include "CandidateFinder.hpp"
17
18#include <deque>
19#include <iterator> // for back_inserter
20#include <sstream>
21#include <string>
22#include <unordered_map>
23#include <vector>
24
25#include "Candidate.hpp"
26#include "CompilationState.h"
27#include "Cost.h"
28#include "ExplodedArg.hpp"
29#include "RenameVars.h" // for renameTyVars
30#include "Resolver.h"
31#include "ResolveTypeof.h"
32#include "SatisfyAssertions.hpp"
33#include "typeops.h" // for adjustExprType, conversionCost, polyCost, specCost
34#include "Unify.h"
35#include "AST/Expr.hpp"
36#include "AST/Node.hpp"
37#include "AST/Pass.hpp"
38#include "AST/Print.hpp"
39#include "AST/SymbolTable.hpp"
40#include "AST/Type.hpp"
41#include "Common/utility.h" // for move, copy
42#include "SymTab/Mangler.h"
43#include "SymTab/Validate.h" // for validateType
44#include "Tuples/Tuples.h" // for handleTupleAssignment
45
46#define PRINT( text ) if ( resolvep ) { text }
47
48namespace ResolvExpr {
49
50const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
51 if ( expr->result.as< ast::ReferenceType >() ) {
52 // cast away reference from expr
53 cost.incReference();
54 return new ast::CastExpr{ expr, expr->result->stripReferences() };
55 }
56
57 return expr;
58}
59
60/// Unique identifier for matching expression resolutions to their requesting expression
61UniqueId globalResnSlot = 0;
62
63Cost computeConversionCost(
64 const ast::Type * argType, const ast::Type * paramType, bool argIsLvalue,
65 const ast::SymbolTable & symtab, const ast::TypeEnvironment & env
66) {
67 PRINT(
68 std::cerr << std::endl << "converting ";
69 ast::print( std::cerr, argType, 2 );
70 std::cerr << std::endl << " to ";
71 ast::print( std::cerr, paramType, 2 );
72 std::cerr << std::endl << "environment is: ";
73 ast::print( std::cerr, env, 2 );
74 std::cerr << std::endl;
75 )
76 Cost convCost = conversionCost( argType, paramType, argIsLvalue, symtab, env );
77 PRINT(
78 std::cerr << std::endl << "cost is " << convCost << std::endl;
79 )
80 if ( convCost == Cost::infinity ) return convCost;
81 convCost.incPoly( polyCost( paramType, symtab, env ) + polyCost( argType, symtab, env ) );
82 PRINT(
83 std::cerr << "cost with polycost is " << convCost << std::endl;
84 )
85 return convCost;
86}
87
88namespace {
89 /// First index is which argument, second is which alternative, third is which exploded element
90 using ExplodedArgs_new = std::deque< std::vector< ExplodedArg > >;
91
92 /// Returns a list of alternatives with the minimum cost in the given list
93 CandidateList findMinCost( const CandidateList & candidates ) {
94 CandidateList out;
95 Cost minCost = Cost::infinity;
96 for ( const CandidateRef & r : candidates ) {
97 if ( r->cost < minCost ) {
98 minCost = r->cost;
99 out.clear();
100 out.emplace_back( r );
101 } else if ( r->cost == minCost ) {
102 out.emplace_back( r );
103 }
104 }
105 return out;
106 }
107
108 /// Computes conversion cost for a given expression to a given type
109 const ast::Expr * computeExpressionConversionCost(
110 const ast::Expr * arg, const ast::Type * paramType, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env, Cost & outCost
111 ) {
112 Cost convCost = computeConversionCost(
113 arg->result, paramType, arg->get_lvalue(), symtab, env );
114 outCost += convCost;
115
116 // If there is a non-zero conversion cost, ignoring poly cost, then the expression requires
117 // conversion. Ignore poly cost for now, since this requires resolution of the cast to
118 // infer parameters and this does not currently work for the reason stated below
119 Cost tmpCost = convCost;
120 tmpCost.incPoly( -tmpCost.get_polyCost() );
121 if ( tmpCost != Cost::zero ) {
122 ast::ptr< ast::Type > newType = paramType;
123 env.apply( newType );
124 return new ast::CastExpr{ arg, newType };
125
126 // xxx - *should* be able to resolve this cast, but at the moment pointers are not
127 // castable to zero_t, but are implicitly convertible. This is clearly inconsistent,
128 // once this is fixed it should be possible to resolve the cast.
129 // xxx - this isn't working, it appears because type1 (parameter) is seen as widenable,
130 // but it shouldn't be because this makes the conversion from DT* to DT* since
131 // commontype(zero_t, DT*) is DT*, rather than nothing
132
133 // CandidateFinder finder{ symtab, env };
134 // finder.find( arg, ResolvMode::withAdjustment() );
135 // assertf( finder.candidates.size() > 0,
136 // "Somehow castable expression failed to find alternatives." );
137 // assertf( finder.candidates.size() == 1,
138 // "Somehow got multiple alternatives for known cast expression." );
139 // return finder.candidates.front()->expr;
140 }
141
142 return arg;
143 }
144
145 /// Computes conversion cost for a given candidate
146 Cost computeApplicationConversionCost(
147 CandidateRef cand, const ast::SymbolTable & symtab
148 ) {
149 auto appExpr = cand->expr.strict_as< ast::ApplicationExpr >();
150 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
151 auto function = pointer->base.strict_as< ast::FunctionType >();
152
153 Cost convCost = Cost::zero;
154 const auto & params = function->params;
155 auto param = params.begin();
156 auto & args = appExpr->args;
157
158 for ( unsigned i = 0; i < args.size(); ++i ) {
159 const ast::Type * argType = args[i]->result;
160 PRINT(
161 std::cerr << "arg expression:" << std::endl;
162 ast::print( std::cerr, args[i], 2 );
163 std::cerr << "--- results are" << std::endl;
164 ast::print( std::cerr, argType, 2 );
165 )
166
167 if ( param == params.end() ) {
168 if ( function->isVarArgs ) {
169 convCost.incUnsafe();
170 PRINT( std::cerr << "end of params with varargs function: inc unsafe: "
171 << convCost << std::endl; ; )
172 // convert reference-typed expressions into value-typed expressions
173 cand->expr = ast::mutate_field_index(
174 appExpr, &ast::ApplicationExpr::args, i,
175 referenceToRvalueConversion( args[i], convCost ) );
176 continue;
177 } else return Cost::infinity;
178 }
179
180 if ( auto def = args[i].as< ast::DefaultArgExpr >() ) {
181 // Default arguments should be free - don't include conversion cost.
182 // Unwrap them here because they are not relevant to the rest of the system
183 cand->expr = ast::mutate_field_index(
184 appExpr, &ast::ApplicationExpr::args, i, def->expr );
185 ++param;
186 continue;
187 }
188
189 // mark conversion cost and also specialization cost of param type
190 const ast::Type * paramType = (*param)->get_type();
191 cand->expr = ast::mutate_field_index(
192 appExpr, &ast::ApplicationExpr::args, i,
193 computeExpressionConversionCost(
194 args[i], paramType, symtab, cand->env, convCost ) );
195 convCost.decSpec( specCost( paramType ) );
196 ++param; // can't be in for-loop update because of the continue
197 }
198
199 if ( param != params.end() ) return Cost::infinity;
200
201 // specialization cost of return types can't be accounted for directly, it disables
202 // otherwise-identical calls, like this example based on auto-newline in the I/O lib:
203 //
204 // forall(otype OS) {
205 // void ?|?(OS&, int); // with newline
206 // OS& ?|?(OS&, int); // no newline, always chosen due to more specialization
207 // }
208
209 // mark type variable and specialization cost of forall clause
210 convCost.incVar( function->forall.size() );
211 for ( const ast::TypeDecl * td : function->forall ) {
212 convCost.decSpec( td->assertions.size() );
213 }
214
215 return convCost;
216 }
217
218 void makeUnifiableVars(
219 const ast::ParameterizedType * type, ast::OpenVarSet & unifiableVars,
220 ast::AssertionSet & need
221 ) {
222 for ( const ast::TypeDecl * tyvar : type->forall ) {
223 unifiableVars[ tyvar->name ] = ast::TypeDecl::Data{ tyvar };
224 for ( const ast::DeclWithType * assn : tyvar->assertions ) {
225 need[ assn ].isUsed = true;
226 }
227 }
228 }
229
230 /// Gets a default value from an initializer, nullptr if not present
231 const ast::ConstantExpr * getDefaultValue( const ast::Init * init ) {
232 if ( auto si = dynamic_cast< const ast::SingleInit * >( init ) ) {
233 if ( auto ce = si->value.as< ast::CastExpr >() ) {
234 return ce->arg.as< ast::ConstantExpr >();
235 } else {
236 return si->value.as< ast::ConstantExpr >();
237 }
238 }
239 return nullptr;
240 }
241
242 /// State to iteratively build a match of parameter expressions to arguments
243 struct ArgPack {
244 std::size_t parent; ///< Index of parent pack
245 ast::ptr< ast::Expr > expr; ///< The argument stored here
246 Cost cost; ///< The cost of this argument
247 ast::TypeEnvironment env; ///< Environment for this pack
248 ast::AssertionSet need; ///< Assertions outstanding for this pack
249 ast::AssertionSet have; ///< Assertions found for this pack
250 ast::OpenVarSet open; ///< Open variables for this pack
251 unsigned nextArg; ///< Index of next argument in arguments list
252 unsigned tupleStart; ///< Number of tuples that start at this index
253 unsigned nextExpl; ///< Index of next exploded element
254 unsigned explAlt; ///< Index of alternative for nextExpl > 0
255
256 ArgPack()
257 : parent( 0 ), expr(), cost( Cost::zero ), env(), need(), have(), open(), nextArg( 0 ),
258 tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
259
260 ArgPack(
261 const ast::TypeEnvironment & env, const ast::AssertionSet & need,
262 const ast::AssertionSet & have, const ast::OpenVarSet & open )
263 : parent( 0 ), expr(), cost( Cost::zero ), env( env ), need( need ), have( have ),
264 open( open ), nextArg( 0 ), tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
265
266 ArgPack(
267 std::size_t parent, const ast::Expr * expr, ast::TypeEnvironment && env,
268 ast::AssertionSet && need, ast::AssertionSet && have, ast::OpenVarSet && open,
269 unsigned nextArg, unsigned tupleStart = 0, Cost cost = Cost::zero,
270 unsigned nextExpl = 0, unsigned explAlt = 0 )
271 : parent(parent), expr( expr ), cost( cost ), env( move( env ) ), need( move( need ) ),
272 have( move( have ) ), open( move( open ) ), nextArg( nextArg ), tupleStart( tupleStart ),
273 nextExpl( nextExpl ), explAlt( explAlt ) {}
274
275 ArgPack(
276 const ArgPack & o, ast::TypeEnvironment && env, ast::AssertionSet && need,
277 ast::AssertionSet && have, ast::OpenVarSet && open, unsigned nextArg, Cost added )
278 : parent( o.parent ), expr( o.expr ), cost( o.cost + added ), env( move( env ) ),
279 need( move( need ) ), have( move( have ) ), open( move( open ) ), nextArg( nextArg ),
280 tupleStart( o.tupleStart ), nextExpl( 0 ), explAlt( 0 ) {}
281
282 /// true if this pack is in the middle of an exploded argument
283 bool hasExpl() const { return nextExpl > 0; }
284
285 /// Gets the list of exploded candidates for this pack
286 const ExplodedArg & getExpl( const ExplodedArgs_new & args ) const {
287 return args[ nextArg-1 ][ explAlt ];
288 }
289
290 /// Ends a tuple expression, consolidating the appropriate args
291 void endTuple( const std::vector< ArgPack > & packs ) {
292 // add all expressions in tuple to list, summing cost
293 std::deque< const ast::Expr * > exprs;
294 const ArgPack * pack = this;
295 if ( expr ) { exprs.emplace_front( expr ); }
296 while ( pack->tupleStart == 0 ) {
297 pack = &packs[pack->parent];
298 exprs.emplace_front( pack->expr );
299 cost += pack->cost;
300 }
301 // reset pack to appropriate tuple
302 std::vector< ast::ptr< ast::Expr > > exprv( exprs.begin(), exprs.end() );
303 expr = new ast::TupleExpr{ expr->location, move( exprv ) };
304 tupleStart = pack->tupleStart - 1;
305 parent = pack->parent;
306 }
307 };
308
309 /// Instantiates an argument to match a parameter, returns false if no matching results left
310 bool instantiateArgument(
311 const ast::Type * paramType, const ast::Init * init, const ExplodedArgs_new & args,
312 std::vector< ArgPack > & results, std::size_t & genStart, const ast::SymbolTable & symtab,
313 unsigned nTuples = 0
314 ) {
315 if ( auto tupleType = dynamic_cast< const ast::TupleType * >( paramType ) ) {
316 // paramType is a TupleType -- group args into a TupleExpr
317 ++nTuples;
318 for ( const ast::Type * type : *tupleType ) {
319 // xxx - dropping initializer changes behaviour from previous, but seems correct
320 // ^^^ need to handle the case where a tuple has a default argument
321 if ( ! instantiateArgument(
322 type, nullptr, args, results, genStart, symtab, nTuples ) ) return false;
323 nTuples = 0;
324 }
325 // re-constitute tuples for final generation
326 for ( auto i = genStart; i < results.size(); ++i ) {
327 results[i].endTuple( results );
328 }
329 return true;
330 } else if ( const ast::TypeInstType * ttype = Tuples::isTtype( paramType ) ) {
331 // paramType is a ttype, consumes all remaining arguments
332
333 // completed tuples; will be spliced to end of results to finish
334 std::vector< ArgPack > finalResults{};
335
336 // iterate until all results completed
337 std::size_t genEnd;
338 ++nTuples;
339 do {
340 genEnd = results.size();
341
342 // add another argument to results
343 for ( std::size_t i = genStart; i < genEnd; ++i ) {
344 unsigned nextArg = results[i].nextArg;
345
346 // use next element of exploded tuple if present
347 if ( results[i].hasExpl() ) {
348 const ExplodedArg & expl = results[i].getExpl( args );
349
350 unsigned nextExpl = results[i].nextExpl + 1;
351 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
352
353 results.emplace_back(
354 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
355 copy( results[i].need ), copy( results[i].have ),
356 copy( results[i].open ), nextArg, nTuples, Cost::zero, nextExpl,
357 results[i].explAlt );
358
359 continue;
360 }
361
362 // finish result when out of arguments
363 if ( nextArg >= args.size() ) {
364 ArgPack newResult{
365 results[i].env, results[i].need, results[i].have, results[i].open };
366 newResult.nextArg = nextArg;
367 const ast::Type * argType = nullptr;
368
369 if ( nTuples > 0 || ! results[i].expr ) {
370 // first iteration or no expression to clone,
371 // push empty tuple expression
372 newResult.parent = i;
373 newResult.expr = new ast::TupleExpr{ CodeLocation{}, {} };
374 argType = newResult.expr->result;
375 } else {
376 // clone result to collect tuple
377 newResult.parent = results[i].parent;
378 newResult.cost = results[i].cost;
379 newResult.tupleStart = results[i].tupleStart;
380 newResult.expr = results[i].expr;
381 argType = newResult.expr->result;
382
383 if ( results[i].tupleStart > 0 && Tuples::isTtype( argType ) ) {
384 // the case where a ttype value is passed directly is special,
385 // e.g. for argument forwarding purposes
386 // xxx - what if passing multiple arguments, last of which is
387 // ttype?
388 // xxx - what would happen if unify was changed so that unifying
389 // tuple
390 // types flattened both before unifying lists? then pass in
391 // TupleType (ttype) below.
392 --newResult.tupleStart;
393 } else {
394 // collapse leftover arguments into tuple
395 newResult.endTuple( results );
396 argType = newResult.expr->result;
397 }
398 }
399
400 // check unification for ttype before adding to final
401 if (
402 unify(
403 ttype, argType, newResult.env, newResult.need, newResult.have,
404 newResult.open, symtab )
405 ) {
406 finalResults.emplace_back( move( newResult ) );
407 }
408
409 continue;
410 }
411
412 // add each possible next argument
413 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
414 const ExplodedArg & expl = args[nextArg][j];
415
416 // fresh copies of parent parameters for this iteration
417 ast::TypeEnvironment env = results[i].env;
418 ast::OpenVarSet open = results[i].open;
419
420 env.addActual( expl.env, open );
421
422 // skip empty tuple arguments by (nearly) cloning parent into next gen
423 if ( expl.exprs.empty() ) {
424 results.emplace_back(
425 results[i], move( env ), copy( results[i].need ),
426 copy( results[i].have ), move( open ), nextArg + 1, expl.cost );
427
428 continue;
429 }
430
431 // add new result
432 results.emplace_back(
433 i, expl.exprs.front(), move( env ), copy( results[i].need ),
434 copy( results[i].have ), move( open ), nextArg + 1, nTuples,
435 expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
436 }
437 }
438
439 // reset for next round
440 genStart = genEnd;
441 nTuples = 0;
442 } while ( genEnd != results.size() );
443
444 // splice final results onto results
445 for ( std::size_t i = 0; i < finalResults.size(); ++i ) {
446 results.emplace_back( move( finalResults[i] ) );
447 }
448 return ! finalResults.empty();
449 }
450
451 // iterate each current subresult
452 std::size_t genEnd = results.size();
453 for ( std::size_t i = genStart; i < genEnd; ++i ) {
454 unsigned nextArg = results[i].nextArg;
455
456 // use remainder of exploded tuple if present
457 if ( results[i].hasExpl() ) {
458 const ExplodedArg & expl = results[i].getExpl( args );
459 const ast::Expr * expr = expl.exprs[ results[i].nextExpl ];
460
461 ast::TypeEnvironment env = results[i].env;
462 ast::AssertionSet need = results[i].need, have = results[i].have;
463 ast::OpenVarSet open = results[i].open;
464
465 const ast::Type * argType = expr->result;
466
467 PRINT(
468 std::cerr << "param type is ";
469 ast::print( std::cerr, paramType );
470 std::cerr << std::endl << "arg type is ";
471 ast::print( std::cerr, argType );
472 std::cerr << std::endl;
473 )
474
475 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
476 unsigned nextExpl = results[i].nextExpl + 1;
477 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
478
479 results.emplace_back(
480 i, expr, move( env ), move( need ), move( have ), move( open ), nextArg,
481 nTuples, Cost::zero, nextExpl, results[i].explAlt );
482 }
483
484 continue;
485 }
486
487 // use default initializers if out of arguments
488 if ( nextArg >= args.size() ) {
489 if ( const ast::ConstantExpr * cnst = getDefaultValue( init ) ) {
490 ast::TypeEnvironment env = results[i].env;
491 ast::AssertionSet need = results[i].need, have = results[i].have;
492 ast::OpenVarSet open = results[i].open;
493
494 if ( unify( paramType, cnst->result, env, need, have, open, symtab ) ) {
495 results.emplace_back(
496 i, new ast::DefaultArgExpr{ cnst->location, cnst }, move( env ),
497 move( need ), move( have ), move( open ), nextArg, nTuples );
498 }
499 }
500
501 continue;
502 }
503
504 // Check each possible next argument
505 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
506 const ExplodedArg & expl = args[nextArg][j];
507
508 // fresh copies of parent parameters for this iteration
509 ast::TypeEnvironment env = results[i].env;
510 ast::AssertionSet need = results[i].need, have = results[i].have;
511 ast::OpenVarSet open = results[i].open;
512
513 env.addActual( expl.env, open );
514
515 // skip empty tuple arguments by (nearly) cloning parent into next gen
516 if ( expl.exprs.empty() ) {
517 results.emplace_back(
518 results[i], move( env ), move( need ), move( have ), move( open ),
519 nextArg + 1, expl.cost );
520
521 continue;
522 }
523
524 // consider only first exploded arg
525 const ast::Expr * expr = expl.exprs.front();
526 const ast::Type * argType = expr->result;
527
528 PRINT(
529 std::cerr << "param type is ";
530 ast::print( std::cerr, paramType );
531 std::cerr << std::endl << "arg type is ";
532 ast::print( std::cerr, argType );
533 std::cerr << std::endl;
534 )
535
536 // attempt to unify types
537 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
538 // add new result
539 results.emplace_back(
540 i, expr, move( env ), move( need ), move( have ), move( open ),
541 nextArg + 1, nTuples, expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
542 }
543 }
544 }
545
546 // reset for next parameter
547 genStart = genEnd;
548
549 return genEnd != results.size(); // were any new results added?
550 }
551
552 /// Generate a cast expression from `arg` to `toType`
553 const ast::Expr * restructureCast(
554 ast::ptr< ast::Expr > & arg, const ast::Type * toType, ast::GeneratedFlag isGenerated = ast::GeneratedCast
555 ) {
556 if (
557 arg->result->size() > 1
558 && ! toType->isVoid()
559 && ! dynamic_cast< const ast::ReferenceType * >( toType )
560 ) {
561 // Argument is a tuple and the target type is neither void nor a reference. Cast each
562 // member of the tuple to its corresponding target type, producing the tuple of those
563 // cast expressions. If there are more components of the tuple than components in the
564 // target type, then excess components do not come out in the result expression (but
565 // UniqueExpr ensures that the side effects will still be produced)
566 if ( Tuples::maybeImpureIgnoreUnique( arg ) ) {
567 // expressions which may contain side effects require a single unique instance of
568 // the expression
569 arg = new ast::UniqueExpr{ arg->location, arg };
570 }
571 std::vector< ast::ptr< ast::Expr > > components;
572 for ( unsigned i = 0; i < toType->size(); ++i ) {
573 // cast each component
574 ast::ptr< ast::Expr > idx = new ast::TupleIndexExpr{ arg->location, arg, i };
575 components.emplace_back(
576 restructureCast( idx, toType->getComponent( i ), isGenerated ) );
577 }
578 return new ast::TupleExpr{ arg->location, move( components ) };
579 } else {
580 // handle normally
581 return new ast::CastExpr{ arg->location, arg, toType, isGenerated };
582 }
583 }
584
585 /// Gets the name from an untyped member expression (must be NameExpr)
586 const std::string & getMemberName( const ast::UntypedMemberExpr * memberExpr ) {
587 if ( memberExpr->member.as< ast::ConstantExpr >() ) {
588 SemanticError( memberExpr, "Indexed access to struct fields unsupported: " );
589 }
590
591 return memberExpr->member.strict_as< ast::NameExpr >()->name;
592 }
593
594 /// Actually visits expressions to find their candidate interpretations
595 class Finder final : public ast::WithShortCircuiting {
596 const ast::SymbolTable & symtab;
597 public:
598 CandidateFinder & selfFinder;
599 CandidateList & candidates;
600 const ast::TypeEnvironment & tenv;
601 ast::ptr< ast::Type > & targetType;
602
603 Finder( CandidateFinder & f )
604 : symtab( f.localSyms ), selfFinder( f ), candidates( f.candidates ), tenv( f.env ),
605 targetType( f.targetType ) {}
606
607 void previsit( const ast::Node * ) { visit_children = false; }
608
609 /// Convenience to add candidate to list
610 template<typename... Args>
611 void addCandidate( Args &&... args ) {
612 candidates.emplace_back( new Candidate{ std::forward<Args>( args )... } );
613 }
614
615 void postvisit( const ast::ApplicationExpr * applicationExpr ) {
616 addCandidate( applicationExpr, tenv );
617 }
618
619 /// Set up candidate assertions for inference
620 void inferParameters( CandidateRef & newCand, CandidateList & out ) {
621 // Set need bindings for any unbound assertions
622 UniqueId crntResnSlot = 0; // matching ID for this expression's assertions
623 for ( auto & assn : newCand->need ) {
624 // skip already-matched assertions
625 if ( assn.second.resnSlot != 0 ) continue;
626 // assign slot for expression if needed
627 if ( crntResnSlot == 0 ) { crntResnSlot = ++globalResnSlot; }
628 // fix slot to assertion
629 assn.second.resnSlot = crntResnSlot;
630 }
631 // pair slot to expression
632 if ( crntResnSlot != 0 ) {
633 newCand->expr.get_and_mutate()->inferred.resnSlots().emplace_back( crntResnSlot );
634 }
635
636 // add to output list; assertion satisfaction will occur later
637 out.emplace_back( newCand );
638 }
639
640 /// Completes a function candidate with arguments located
641 void validateFunctionCandidate(
642 const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results,
643 CandidateList & out
644 ) {
645 ast::ApplicationExpr * appExpr =
646 new ast::ApplicationExpr{ func->expr->location, func->expr };
647 // sum cost and accumulate arguments
648 std::deque< const ast::Expr * > args;
649 Cost cost = func->cost;
650 const ArgPack * pack = &result;
651 while ( pack->expr ) {
652 args.emplace_front( pack->expr );
653 cost += pack->cost;
654 pack = &results[pack->parent];
655 }
656 std::vector< ast::ptr< ast::Expr > > vargs( args.begin(), args.end() );
657 appExpr->args = move( vargs );
658 // build and validate new candidate
659 auto newCand =
660 std::make_shared<Candidate>( appExpr, result.env, result.open, result.need, cost );
661 PRINT(
662 std::cerr << "instantiate function success: " << appExpr << std::endl;
663 std::cerr << "need assertions:" << std::endl;
664 ast::print( std::cerr, result.need, 2 );
665 )
666 inferParameters( newCand, out );
667 }
668
669 /// Builds a list of candidates for a function, storing them in out
670 void makeFunctionCandidates(
671 const CandidateRef & func, const ast::FunctionType * funcType,
672 const ExplodedArgs_new & args, CandidateList & out
673 ) {
674 ast::OpenVarSet funcOpen;
675 ast::AssertionSet funcNeed, funcHave;
676 ast::TypeEnvironment funcEnv{ func->env };
677 makeUnifiableVars( funcType, funcOpen, funcNeed );
678 // add all type variables as open variables now so that those not used in the
679 // parameter list are still considered open
680 funcEnv.add( funcType->forall );
681
682 if ( targetType && ! targetType->isVoid() && ! funcType->returns.empty() ) {
683 // attempt to narrow based on expected target type
684 const ast::Type * returnType = funcType->returns.front()->get_type();
685 if ( ! unify(
686 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, symtab )
687 ) {
688 // unification failed, do not pursue this candidate
689 return;
690 }
691 }
692
693 // iteratively build matches, one parameter at a time
694 std::vector< ArgPack > results;
695 results.emplace_back( funcEnv, funcNeed, funcHave, funcOpen );
696 std::size_t genStart = 0;
697
698 for ( const ast::DeclWithType * param : funcType->params ) {
699 auto obj = strict_dynamic_cast< const ast::ObjectDecl * >( param );
700 // Try adding the arguments corresponding to the current parameter to the existing
701 // matches
702 if ( ! instantiateArgument(
703 obj->type, obj->init, args, results, genStart, symtab ) ) return;
704 }
705
706 if ( funcType->isVarArgs ) {
707 // append any unused arguments to vararg pack
708 std::size_t genEnd;
709 do {
710 genEnd = results.size();
711
712 // iterate results
713 for ( std::size_t i = genStart; i < genEnd; ++i ) {
714 unsigned nextArg = results[i].nextArg;
715
716 // use remainder of exploded tuple if present
717 if ( results[i].hasExpl() ) {
718 const ExplodedArg & expl = results[i].getExpl( args );
719
720 unsigned nextExpl = results[i].nextExpl + 1;
721 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
722
723 results.emplace_back(
724 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
725 copy( results[i].need ), copy( results[i].have ),
726 copy( results[i].open ), nextArg, 0, Cost::zero, nextExpl,
727 results[i].explAlt );
728
729 continue;
730 }
731
732 // finish result when out of arguments
733 if ( nextArg >= args.size() ) {
734 validateFunctionCandidate( func, results[i], results, out );
735
736 continue;
737 }
738
739 // add each possible next argument
740 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
741 const ExplodedArg & expl = args[nextArg][j];
742
743 // fresh copies of parent parameters for this iteration
744 ast::TypeEnvironment env = results[i].env;
745 ast::OpenVarSet open = results[i].open;
746
747 env.addActual( expl.env, open );
748
749 // skip empty tuple arguments by (nearly) cloning parent into next gen
750 if ( expl.exprs.empty() ) {
751 results.emplace_back(
752 results[i], move( env ), copy( results[i].need ),
753 copy( results[i].have ), move( open ), nextArg + 1,
754 expl.cost );
755
756 continue;
757 }
758
759 // add new result
760 results.emplace_back(
761 i, expl.exprs.front(), move( env ), copy( results[i].need ),
762 copy( results[i].have ), move( open ), nextArg + 1, 0, expl.cost,
763 expl.exprs.size() == 1 ? 0 : 1, j );
764 }
765 }
766
767 genStart = genEnd;
768 } while( genEnd != results.size() );
769 } else {
770 // filter out the results that don't use all the arguments
771 for ( std::size_t i = genStart; i < results.size(); ++i ) {
772 ArgPack & result = results[i];
773 if ( ! result.hasExpl() && result.nextArg >= args.size() ) {
774 validateFunctionCandidate( func, result, results, out );
775 }
776 }
777 }
778 }
779
780 /// Adds implicit struct-conversions to the alternative list
781 void addAnonConversions( const CandidateRef & cand ) {
782 // adds anonymous member interpretations whenever an aggregate value type is seen.
783 // it's okay for the aggregate expression to have reference type -- cast it to the
784 // base type to treat the aggregate as the referenced value
785 ast::ptr< ast::Expr > aggrExpr( cand->expr );
786 ast::ptr< ast::Type > & aggrType = aggrExpr.get_and_mutate()->result;
787 cand->env.apply( aggrType );
788
789 if ( aggrType.as< ast::ReferenceType >() ) {
790 aggrExpr = new ast::CastExpr{ aggrExpr, aggrType->stripReferences() };
791 }
792
793 if ( auto structInst = aggrExpr->result.as< ast::StructInstType >() ) {
794 addAggMembers( structInst, aggrExpr, *cand, Cost::safe, "" );
795 } else if ( auto unionInst = aggrExpr->result.as< ast::UnionInstType >() ) {
796 addAggMembers( unionInst, aggrExpr, *cand, Cost::safe, "" );
797 }
798 }
799
800 /// Adds aggregate member interpretations
801 void addAggMembers(
802 const ast::ReferenceToType * aggrInst, const ast::Expr * expr,
803 const Candidate & cand, const Cost & addedCost, const std::string & name
804 ) {
805 for ( const ast::Decl * decl : aggrInst->lookup( name ) ) {
806 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( decl );
807 CandidateRef newCand = std::make_shared<Candidate>(
808 cand, new ast::MemberExpr{ expr->location, dwt, expr }, addedCost );
809 // add anonymous member interpretations whenever an aggregate value type is seen
810 // as a member expression
811 addAnonConversions( newCand );
812 candidates.emplace_back( move( newCand ) );
813 }
814 }
815
816 /// Adds tuple member interpretations
817 void addTupleMembers(
818 const ast::TupleType * tupleType, const ast::Expr * expr, const Candidate & cand,
819 const Cost & addedCost, const ast::Expr * member
820 ) {
821 if ( auto constantExpr = dynamic_cast< const ast::ConstantExpr * >( member ) ) {
822 // get the value of the constant expression as an int, must be between 0 and the
823 // length of the tuple to have meaning
824 long long val = constantExpr->intValue();
825 if ( val >= 0 && (unsigned long long)val < tupleType->size() ) {
826 addCandidate(
827 cand, new ast::TupleIndexExpr{ expr->location, expr, (unsigned)val },
828 addedCost );
829 }
830 }
831 }
832
833 void postvisit( const ast::UntypedExpr * untypedExpr ) {
834 CandidateFinder funcFinder{ symtab, tenv };
835 funcFinder.find( untypedExpr->func, ResolvMode::withAdjustment() );
836 // short-circuit if no candidates
837 if ( funcFinder.candidates.empty() ) return;
838
839 std::vector< CandidateFinder > argCandidates =
840 selfFinder.findSubExprs( untypedExpr->args );
841
842 // take care of possible tuple assignments
843 // if not tuple assignment, handled as normal function call
844 Tuples::handleTupleAssignment( selfFinder, untypedExpr, argCandidates );
845
846 // find function operators
847 ast::ptr< ast::Expr > opExpr = new ast::NameExpr{ untypedExpr->location, "?()" };
848 CandidateFinder opFinder{ symtab, tenv };
849 // okay if there aren't any function operations
850 opFinder.find( opExpr, ResolvMode::withoutFailFast() );
851 PRINT(
852 std::cerr << "known function ops:" << std::endl;
853 print( std::cerr, opFinder.candidates, 1 );
854 )
855
856 // pre-explode arguments
857 ExplodedArgs_new argExpansions;
858 for ( const CandidateFinder & args : argCandidates ) {
859 argExpansions.emplace_back();
860 auto & argE = argExpansions.back();
861 for ( const CandidateRef & arg : args ) { argE.emplace_back( *arg, symtab ); }
862 }
863
864 // Find function matches
865 CandidateList found;
866 SemanticErrorException errors;
867 for ( CandidateRef & func : funcFinder ) {
868 try {
869 PRINT(
870 std::cerr << "working on alternative:" << std::endl;
871 print( std::cerr, *func, 2 );
872 )
873
874 // check if the type is a pointer to function
875 const ast::Type * funcResult = func->expr->result->stripReferences();
876 if ( auto pointer = dynamic_cast< const ast::PointerType * >( funcResult ) ) {
877 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
878 CandidateRef newFunc{ new Candidate{ *func } };
879 newFunc->expr =
880 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
881 makeFunctionCandidates( newFunc, function, argExpansions, found );
882 }
883 } else if (
884 auto inst = dynamic_cast< const ast::TypeInstType * >( funcResult )
885 ) {
886 if ( const ast::EqvClass * clz = func->env.lookup( inst->name ) ) {
887 if ( auto function = clz->bound.as< ast::FunctionType >() ) {
888 CandidateRef newFunc{ new Candidate{ *func } };
889 newFunc->expr =
890 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
891 makeFunctionCandidates( newFunc, function, argExpansions, found );
892 }
893 }
894 }
895 } catch ( SemanticErrorException & e ) { errors.append( e ); }
896 }
897
898 // Find matches on function operators `?()`
899 if ( ! opFinder.candidates.empty() ) {
900 // add exploded function alternatives to front of argument list
901 std::vector< ExplodedArg > funcE;
902 funcE.reserve( funcFinder.candidates.size() );
903 for ( const CandidateRef & func : funcFinder ) {
904 funcE.emplace_back( *func, symtab );
905 }
906 argExpansions.emplace_front( move( funcE ) );
907
908 for ( const CandidateRef & op : opFinder ) {
909 try {
910 // check if type is pointer-to-function
911 const ast::Type * opResult = op->expr->result->stripReferences();
912 if ( auto pointer = dynamic_cast< const ast::PointerType * >( opResult ) ) {
913 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
914 CandidateRef newOp{ new Candidate{ *op} };
915 newOp->expr =
916 referenceToRvalueConversion( newOp->expr, newOp->cost );
917 makeFunctionCandidates( newOp, function, argExpansions, found );
918 }
919 }
920 } catch ( SemanticErrorException & e ) { errors.append( e ); }
921 }
922 }
923
924 // Implement SFINAE; resolution errors are only errors if there aren't any non-error
925 // candidates
926 if ( found.empty() && ! errors.isEmpty() ) { throw errors; }
927
928 // Compute conversion costs
929 for ( CandidateRef & withFunc : found ) {
930 Cost cvtCost = computeApplicationConversionCost( withFunc, symtab );
931
932 PRINT(
933 auto appExpr = withFunc->expr.strict_as< ast::ApplicationExpr >();
934 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
935 auto function = pointer->base.strict_as< ast::FunctionType >();
936
937 std::cerr << "Case +++++++++++++ " << appExpr->func << std::endl;
938 std::cerr << "parameters are:" << std::endl;
939 ast::printAll( std::cerr, function->params, 2 );
940 std::cerr << "arguments are:" << std::endl;
941 ast::printAll( std::cerr, appExpr->args, 2 );
942 std::cerr << "bindings are:" << std::endl;
943 ast::print( std::cerr, withFunc->env, 2 );
944 std::cerr << "cost is: " << withFunc->cost << std::endl;
945 std::cerr << "cost of conversion is:" << cvtCost << std::endl;
946 )
947
948 if ( cvtCost != Cost::infinity ) {
949 withFunc->cvtCost = cvtCost;
950 candidates.emplace_back( move( withFunc ) );
951 }
952 }
953 found = move( candidates );
954
955 // use a new list so that candidates are not examined by addAnonConversions twice
956 CandidateList winners = findMinCost( found );
957 promoteCvtCost( winners );
958
959 // function may return a struct/union value, in which case we need to add candidates
960 // for implicit conversions to each of the anonymous members, which must happen after
961 // `findMinCost`, since anon conversions are never the cheapest
962 for ( const CandidateRef & c : winners ) {
963 addAnonConversions( c );
964 }
965 spliceBegin( candidates, winners );
966
967 if ( candidates.empty() && targetType && ! targetType->isVoid() ) {
968 // If resolution is unsuccessful with a target type, try again without, since it
969 // will sometimes succeed when it wouldn't with a target type binding.
970 // For example:
971 // forall( otype T ) T & ?[]( T *, ptrdiff_t );
972 // const char * x = "hello world";
973 // unsigned char ch = x[0];
974 // Fails with simple return type binding (xxx -- check this!) as follows:
975 // * T is bound to unsigned char
976 // * (x: const char *) is unified with unsigned char *, which fails
977 // xxx -- fix this better
978 targetType = nullptr;
979 postvisit( untypedExpr );
980 }
981 }
982
983 /// true if expression is an lvalue
984 static bool isLvalue( const ast::Expr * x ) {
985 return x->result && ( x->get_lvalue() || x->result.as< ast::ReferenceType >() );
986 }
987
988 void postvisit( const ast::AddressExpr * addressExpr ) {
989 CandidateFinder finder{ symtab, tenv };
990 finder.find( addressExpr->arg );
991 for ( CandidateRef & r : finder.candidates ) {
992 if ( ! isLvalue( r->expr ) ) continue;
993 addCandidate( *r, new ast::AddressExpr{ addressExpr->location, r->expr } );
994 }
995 }
996
997 void postvisit( const ast::LabelAddressExpr * labelExpr ) {
998 addCandidate( labelExpr, tenv );
999 }
1000
1001 void postvisit( const ast::CastExpr * castExpr ) {
1002 ast::ptr< ast::Type > toType = castExpr->result;
1003 assert( toType );
1004 toType = resolveTypeof( toType, symtab );
1005 toType = SymTab::validateType( castExpr->location, toType, symtab );
1006 toType = adjustExprType( toType, tenv, symtab );
1007
1008 CandidateFinder finder{ symtab, tenv, toType };
1009 finder.find( castExpr->arg, ResolvMode::withAdjustment() );
1010
1011 CandidateList matches;
1012 for ( CandidateRef & cand : finder.candidates ) {
1013 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1014 ast::OpenVarSet open( cand->open );
1015
1016 cand->env.extractOpenVars( open );
1017
1018 // It is possible that a cast can throw away some values in a multiply-valued
1019 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of the
1020 // subexpression results that are cast directly. The candidate is invalid if it
1021 // has fewer results than there are types to cast to.
1022 int discardedValues = cand->expr->result->size() - toType->size();
1023 if ( discardedValues < 0 ) continue;
1024
1025 // unification run for side-effects
1026 unify( toType, cand->expr->result, cand->env, need, have, open, symtab );
1027 Cost thisCost = castCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1028 symtab, cand->env );
1029 PRINT(
1030 std::cerr << "working on cast with result: " << toType << std::endl;
1031 std::cerr << "and expr type: " << cand->expr->result << std::endl;
1032 std::cerr << "env: " << cand->env << std::endl;
1033 )
1034 if ( thisCost != Cost::infinity ) {
1035 PRINT(
1036 std::cerr << "has finite cost." << std::endl;
1037 )
1038 // count one safe conversion for each value that is thrown away
1039 thisCost.incSafe( discardedValues );
1040 CandidateRef newCand = std::make_shared<Candidate>(
1041 restructureCast( cand->expr, toType, castExpr->isGenerated ),
1042 copy( cand->env ), move( open ), move( need ), cand->cost,
1043 cand->cost + thisCost );
1044 inferParameters( newCand, matches );
1045 }
1046 }
1047
1048 // select first on argument cost, then conversion cost
1049 CandidateList minArgCost = findMinCost( matches );
1050 promoteCvtCost( minArgCost );
1051 candidates = findMinCost( minArgCost );
1052 }
1053
1054 void postvisit( const ast::VirtualCastExpr * castExpr ) {
1055 assertf( castExpr->result, "Implicit virtual cast targets not yet supported." );
1056 CandidateFinder finder{ symtab, tenv };
1057 // don't prune here, all alternatives guaranteed to have same type
1058 finder.find( castExpr->arg, ResolvMode::withoutPrune() );
1059 for ( CandidateRef & r : finder.candidates ) {
1060 addCandidate(
1061 *r,
1062 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
1063 }
1064 }
1065
1066 void postvisit( const ast::UntypedMemberExpr * memberExpr ) {
1067 CandidateFinder aggFinder{ symtab, tenv };
1068 aggFinder.find( memberExpr->aggregate, ResolvMode::withAdjustment() );
1069 for ( CandidateRef & agg : aggFinder.candidates ) {
1070 // it's okay for the aggregate expression to have reference type -- cast it to the
1071 // base type to treat the aggregate as the referenced value
1072 Cost addedCost = Cost::zero;
1073 agg->expr = referenceToRvalueConversion( agg->expr, addedCost );
1074
1075 // find member of the given type
1076 if ( auto structInst = agg->expr->result.as< ast::StructInstType >() ) {
1077 addAggMembers(
1078 structInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1079 } else if ( auto unionInst = agg->expr->result.as< ast::UnionInstType >() ) {
1080 addAggMembers(
1081 unionInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1082 } else if ( auto tupleType = agg->expr->result.as< ast::TupleType >() ) {
1083 addTupleMembers( tupleType, agg->expr, *agg, addedCost, memberExpr->member );
1084 }
1085 }
1086 }
1087
1088 void postvisit( const ast::MemberExpr * memberExpr ) {
1089 addCandidate( memberExpr, tenv );
1090 }
1091
1092 void postvisit( const ast::NameExpr * nameExpr ) {
1093 std::vector< ast::SymbolTable::IdData > declList = symtab.lookupId( nameExpr->name );
1094 PRINT( std::cerr << "nameExpr is " << nameExpr->name << std::endl; )
1095 for ( auto & data : declList ) {
1096 Cost cost = Cost::zero;
1097 ast::Expr * newExpr = data.combine( nameExpr->location, cost );
1098
1099 CandidateRef newCand = std::make_shared<Candidate>(
1100 newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, Cost::zero,
1101 cost );
1102 PRINT(
1103 std::cerr << "decl is ";
1104 ast::print( std::cerr, data.id );
1105 std::cerr << std::endl;
1106 std::cerr << "newExpr is ";
1107 ast::print( std::cerr, newExpr );
1108 std::cerr << std::endl;
1109 )
1110 newCand->expr = ast::mutate_field(
1111 newCand->expr.get(), &ast::Expr::result,
1112 renameTyVars( newCand->expr->result ) );
1113 // add anonymous member interpretations whenever an aggregate value type is seen
1114 // as a name expression
1115 addAnonConversions( newCand );
1116 candidates.emplace_back( move( newCand ) );
1117 }
1118 }
1119
1120 void postvisit( const ast::VariableExpr * variableExpr ) {
1121 // not sufficient to just pass `variableExpr` here, type might have changed since
1122 // creation
1123 addCandidate(
1124 new ast::VariableExpr{ variableExpr->location, variableExpr->var }, tenv );
1125 }
1126
1127 void postvisit( const ast::ConstantExpr * constantExpr ) {
1128 addCandidate( constantExpr, tenv );
1129 }
1130
1131 void postvisit( const ast::SizeofExpr * sizeofExpr ) {
1132 if ( sizeofExpr->type ) {
1133 addCandidate(
1134 new ast::SizeofExpr{
1135 sizeofExpr->location, resolveTypeof( sizeofExpr->type, symtab ) },
1136 tenv );
1137 } else {
1138 // find all candidates for the argument to sizeof
1139 CandidateFinder finder{ symtab, tenv };
1140 finder.find( sizeofExpr->expr );
1141 // find the lowest-cost candidate, otherwise ambiguous
1142 CandidateList winners = findMinCost( finder.candidates );
1143 if ( winners.size() != 1 ) {
1144 SemanticError(
1145 sizeofExpr->expr.get(), "Ambiguous expression in sizeof operand: " );
1146 }
1147 // return the lowest-cost candidate
1148 CandidateRef & choice = winners.front();
1149 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1150 choice->cost = Cost::zero;
1151 addCandidate( *choice, new ast::SizeofExpr{ sizeofExpr->location, choice->expr } );
1152 }
1153 }
1154
1155 void postvisit( const ast::AlignofExpr * alignofExpr ) {
1156 if ( alignofExpr->type ) {
1157 addCandidate(
1158 new ast::AlignofExpr{
1159 alignofExpr->location, resolveTypeof( alignofExpr->type, symtab ) },
1160 tenv );
1161 } else {
1162 // find all candidates for the argument to alignof
1163 CandidateFinder finder{ symtab, tenv };
1164 finder.find( alignofExpr->expr );
1165 // find the lowest-cost candidate, otherwise ambiguous
1166 CandidateList winners = findMinCost( finder.candidates );
1167 if ( winners.size() != 1 ) {
1168 SemanticError(
1169 alignofExpr->expr.get(), "Ambiguous expression in alignof operand: " );
1170 }
1171 // return the lowest-cost candidate
1172 CandidateRef & choice = winners.front();
1173 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1174 choice->cost = Cost::zero;
1175 addCandidate(
1176 *choice, new ast::AlignofExpr{ alignofExpr->location, choice->expr } );
1177 }
1178 }
1179
1180 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
1181 const ast::ReferenceToType * aggInst;
1182 if (( aggInst = offsetofExpr->type.as< ast::StructInstType >() )) ;
1183 else if (( aggInst = offsetofExpr->type.as< ast::UnionInstType >() )) ;
1184 else return;
1185
1186 for ( const ast::Decl * member : aggInst->lookup( offsetofExpr->member ) ) {
1187 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( member );
1188 addCandidate(
1189 new ast::OffsetofExpr{ offsetofExpr->location, aggInst, dwt }, tenv );
1190 }
1191 }
1192
1193 void postvisit( const ast::OffsetofExpr * offsetofExpr ) {
1194 addCandidate( offsetofExpr, tenv );
1195 }
1196
1197 void postvisit( const ast::OffsetPackExpr * offsetPackExpr ) {
1198 addCandidate( offsetPackExpr, tenv );
1199 }
1200
1201 void postvisit( const ast::LogicalExpr * logicalExpr ) {
1202 CandidateFinder finder1{ symtab, tenv };
1203 finder1.find( logicalExpr->arg1, ResolvMode::withAdjustment() );
1204 if ( finder1.candidates.empty() ) return;
1205
1206 CandidateFinder finder2{ symtab, tenv };
1207 finder2.find( logicalExpr->arg2, ResolvMode::withAdjustment() );
1208 if ( finder2.candidates.empty() ) return;
1209
1210 for ( const CandidateRef & r1 : finder1.candidates ) {
1211 for ( const CandidateRef & r2 : finder2.candidates ) {
1212 ast::TypeEnvironment env{ r1->env };
1213 env.simpleCombine( r2->env );
1214 ast::OpenVarSet open{ r1->open };
1215 mergeOpenVars( open, r2->open );
1216 ast::AssertionSet need;
1217 mergeAssertionSet( need, r1->need );
1218 mergeAssertionSet( need, r2->need );
1219
1220 addCandidate(
1221 new ast::LogicalExpr{
1222 logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
1223 move( env ), move( open ), move( need ), r1->cost + r2->cost );
1224 }
1225 }
1226 }
1227
1228 void postvisit( const ast::ConditionalExpr * conditionalExpr ) {
1229 // candidates for condition
1230 CandidateFinder finder1{ symtab, tenv };
1231 finder1.find( conditionalExpr->arg1, ResolvMode::withAdjustment() );
1232 if ( finder1.candidates.empty() ) return;
1233
1234 // candidates for true result
1235 CandidateFinder finder2{ symtab, tenv };
1236 finder2.find( conditionalExpr->arg2, ResolvMode::withAdjustment() );
1237 if ( finder2.candidates.empty() ) return;
1238
1239 // candidates for false result
1240 CandidateFinder finder3{ symtab, tenv };
1241 finder3.find( conditionalExpr->arg3, ResolvMode::withAdjustment() );
1242 if ( finder3.candidates.empty() ) return;
1243
1244 for ( const CandidateRef & r1 : finder1.candidates ) {
1245 for ( const CandidateRef & r2 : finder2.candidates ) {
1246 for ( const CandidateRef & r3 : finder3.candidates ) {
1247 ast::TypeEnvironment env{ r1->env };
1248 env.simpleCombine( r2->env );
1249 env.simpleCombine( r3->env );
1250 ast::OpenVarSet open{ r1->open };
1251 mergeOpenVars( open, r2->open );
1252 mergeOpenVars( open, r3->open );
1253 ast::AssertionSet need;
1254 mergeAssertionSet( need, r1->need );
1255 mergeAssertionSet( need, r2->need );
1256 mergeAssertionSet( need, r3->need );
1257 ast::AssertionSet have;
1258
1259 // unify true and false results, then infer parameters to produce new
1260 // candidates
1261 ast::ptr< ast::Type > common;
1262 if (
1263 unify(
1264 r2->expr->result, r3->expr->result, env, need, have, open, symtab,
1265 common )
1266 ) {
1267 // generate typed expression
1268 ast::ConditionalExpr * newExpr = new ast::ConditionalExpr{
1269 conditionalExpr->location, r1->expr, r2->expr, r3->expr };
1270 newExpr->result = common ? common : r2->expr->result;
1271 // convert both options to result type
1272 Cost cost = r1->cost + r2->cost + r3->cost;
1273 newExpr->arg2 = computeExpressionConversionCost(
1274 newExpr->arg2, newExpr->result, symtab, env, cost );
1275 newExpr->arg3 = computeExpressionConversionCost(
1276 newExpr->arg3, newExpr->result, symtab, env, cost );
1277 // output candidate
1278 CandidateRef newCand = std::make_shared<Candidate>(
1279 newExpr, move( env ), move( open ), move( need ), cost );
1280 inferParameters( newCand, candidates );
1281 }
1282 }
1283 }
1284 }
1285 }
1286
1287 void postvisit( const ast::CommaExpr * commaExpr ) {
1288 ast::TypeEnvironment env{ tenv };
1289 ast::ptr< ast::Expr > arg1 = resolveInVoidContext( commaExpr->arg1, symtab, env );
1290
1291 CandidateFinder finder2{ symtab, env };
1292 finder2.find( commaExpr->arg2, ResolvMode::withAdjustment() );
1293
1294 for ( const CandidateRef & r2 : finder2.candidates ) {
1295 addCandidate( *r2, new ast::CommaExpr{ commaExpr->location, arg1, r2->expr } );
1296 }
1297 }
1298
1299 void postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr ) {
1300 addCandidate( ctorExpr, tenv );
1301 }
1302
1303 void postvisit( const ast::ConstructorExpr * ctorExpr ) {
1304 CandidateFinder finder{ symtab, tenv };
1305 finder.find( ctorExpr->callExpr, ResolvMode::withoutPrune() );
1306 for ( CandidateRef & r : finder.candidates ) {
1307 addCandidate( *r, new ast::ConstructorExpr{ ctorExpr->location, r->expr } );
1308 }
1309 }
1310
1311 void postvisit( const ast::RangeExpr * rangeExpr ) {
1312 // resolve low and high, accept candidates where low and high types unify
1313 CandidateFinder finder1{ symtab, tenv };
1314 finder1.find( rangeExpr->low, ResolvMode::withAdjustment() );
1315 if ( finder1.candidates.empty() ) return;
1316
1317 CandidateFinder finder2{ symtab, tenv };
1318 finder2.find( rangeExpr->high, ResolvMode::withAdjustment() );
1319 if ( finder2.candidates.empty() ) return;
1320
1321 for ( const CandidateRef & r1 : finder1.candidates ) {
1322 for ( const CandidateRef & r2 : finder2.candidates ) {
1323 ast::TypeEnvironment env{ r1->env };
1324 env.simpleCombine( r2->env );
1325 ast::OpenVarSet open{ r1->open };
1326 mergeOpenVars( open, r2->open );
1327 ast::AssertionSet need;
1328 mergeAssertionSet( need, r1->need );
1329 mergeAssertionSet( need, r2->need );
1330 ast::AssertionSet have;
1331
1332 ast::ptr< ast::Type > common;
1333 if (
1334 unify(
1335 r1->expr->result, r2->expr->result, env, need, have, open, symtab,
1336 common )
1337 ) {
1338 // generate new expression
1339 ast::RangeExpr * newExpr =
1340 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1341 newExpr->result = common ? common : r1->expr->result;
1342 // add candidate
1343 CandidateRef newCand = std::make_shared<Candidate>(
1344 newExpr, move( env ), move( open ), move( need ),
1345 r1->cost + r2->cost );
1346 inferParameters( newCand, candidates );
1347 }
1348 }
1349 }
1350 }
1351
1352 void postvisit( const ast::UntypedTupleExpr * tupleExpr ) {
1353 std::vector< CandidateFinder > subCandidates =
1354 selfFinder.findSubExprs( tupleExpr->exprs );
1355 std::vector< CandidateList > possibilities;
1356 combos( subCandidates.begin(), subCandidates.end(), back_inserter( possibilities ) );
1357
1358 for ( const CandidateList & subs : possibilities ) {
1359 std::vector< ast::ptr< ast::Expr > > exprs;
1360 exprs.reserve( subs.size() );
1361 for ( const CandidateRef & sub : subs ) { exprs.emplace_back( sub->expr ); }
1362
1363 ast::TypeEnvironment env;
1364 ast::OpenVarSet open;
1365 ast::AssertionSet need;
1366 for ( const CandidateRef & sub : subs ) {
1367 env.simpleCombine( sub->env );
1368 mergeOpenVars( open, sub->open );
1369 mergeAssertionSet( need, sub->need );
1370 }
1371
1372 addCandidate(
1373 new ast::TupleExpr{ tupleExpr->location, move( exprs ) },
1374 move( env ), move( open ), move( need ), sumCost( subs ) );
1375 }
1376 }
1377
1378 void postvisit( const ast::TupleExpr * tupleExpr ) {
1379 addCandidate( tupleExpr, tenv );
1380 }
1381
1382 void postvisit( const ast::TupleIndexExpr * tupleExpr ) {
1383 addCandidate( tupleExpr, tenv );
1384 }
1385
1386 void postvisit( const ast::TupleAssignExpr * tupleExpr ) {
1387 addCandidate( tupleExpr, tenv );
1388 }
1389
1390 void postvisit( const ast::UniqueExpr * unqExpr ) {
1391 CandidateFinder finder{ symtab, tenv };
1392 finder.find( unqExpr->expr, ResolvMode::withAdjustment() );
1393 for ( CandidateRef & r : finder.candidates ) {
1394 // ensure that the the id is passed on so that the expressions are "linked"
1395 addCandidate( *r, new ast::UniqueExpr{ unqExpr->location, r->expr, unqExpr->id } );
1396 }
1397 }
1398
1399 void postvisit( const ast::StmtExpr * stmtExpr ) {
1400 addCandidate( resolveStmtExpr( stmtExpr, symtab ), tenv );
1401 }
1402
1403 void postvisit( const ast::UntypedInitExpr * initExpr ) {
1404 // handle each option like a cast
1405 CandidateList matches;
1406 PRINT(
1407 std::cerr << "untyped init expr: " << initExpr << std::endl;
1408 )
1409 // O(n^2) checks of d-types with e-types
1410 for ( const ast::InitAlternative & initAlt : initExpr->initAlts ) {
1411 // calculate target type
1412 const ast::Type * toType = resolveTypeof( initAlt.type, symtab );
1413 toType = SymTab::validateType( initExpr->location, toType, symtab );
1414 toType = adjustExprType( toType, tenv, symtab );
1415 // The call to find must occur inside this loop, otherwise polymorphic return
1416 // types are not bound to the initialization type, since return type variables are
1417 // only open for the duration of resolving the UntypedExpr.
1418 CandidateFinder finder{ symtab, tenv, toType };
1419 finder.find( initExpr->expr, ResolvMode::withAdjustment() );
1420 for ( CandidateRef & cand : finder.candidates ) {
1421 ast::TypeEnvironment env{ cand->env };
1422 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1423 ast::OpenVarSet open{ cand->open };
1424
1425 PRINT(
1426 std::cerr << " @ " << toType << " " << initAlt.designation << std::endl;
1427 )
1428
1429 // It is possible that a cast can throw away some values in a multiply-valued
1430 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of
1431 // the subexpression results that are cast directly. The candidate is invalid
1432 // if it has fewer results than there are types to cast to.
1433 int discardedValues = cand->expr->result->size() - toType->size();
1434 if ( discardedValues < 0 ) continue;
1435
1436 // unification run for side-effects
1437 unify( toType, cand->expr->result, env, need, have, open, symtab );
1438 Cost thisCost = castCost( cand->expr->result, toType, cand->expr->get_lvalue(),
1439 symtab, env );
1440
1441 if ( thisCost != Cost::infinity ) {
1442 // count one safe conversion for each value that is thrown away
1443 thisCost.incSafe( discardedValues );
1444 CandidateRef newCand = std::make_shared<Candidate>(
1445 new ast::InitExpr{
1446 initExpr->location, restructureCast( cand->expr, toType ),
1447 initAlt.designation },
1448 copy( cand->env ), move( open ), move( need ), cand->cost, thisCost );
1449 inferParameters( newCand, matches );
1450 }
1451 }
1452 }
1453
1454 // select first on argument cost, then conversion cost
1455 CandidateList minArgCost = findMinCost( matches );
1456 promoteCvtCost( minArgCost );
1457 candidates = findMinCost( minArgCost );
1458 }
1459
1460 void postvisit( const ast::InitExpr * ) {
1461 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
1462 }
1463
1464 void postvisit( const ast::DeletedExpr * ) {
1465 assertf( false, "CandidateFinder should never see a DeletedExpr." );
1466 }
1467
1468 void postvisit( const ast::GenericExpr * ) {
1469 assertf( false, "_Generic is not yet supported." );
1470 }
1471 };
1472
1473 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1474 /// return type. Skips ambiguous candidates.
1475 CandidateList pruneCandidates( CandidateList & candidates ) {
1476 struct PruneStruct {
1477 CandidateRef candidate;
1478 bool ambiguous;
1479
1480 PruneStruct() = default;
1481 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1482 };
1483
1484 // find lowest-cost candidate for each type
1485 std::unordered_map< std::string, PruneStruct > selected;
1486 for ( CandidateRef & candidate : candidates ) {
1487 std::string mangleName;
1488 {
1489 ast::ptr< ast::Type > newType = candidate->expr->result;
1490 assertf(candidate->expr->result, "Result of expression %p for candidate is null", candidate->expr.get());
1491 candidate->env.apply( newType );
1492 mangleName = Mangle::mangle( newType );
1493 }
1494
1495 auto found = selected.find( mangleName );
1496 if ( found != selected.end() ) {
1497 if ( candidate->cost < found->second.candidate->cost ) {
1498 PRINT(
1499 std::cerr << "cost " << candidate->cost << " beats "
1500 << found->second.candidate->cost << std::endl;
1501 )
1502
1503 found->second = PruneStruct{ candidate };
1504 } else if ( candidate->cost == found->second.candidate->cost ) {
1505 // if one of the candidates contains a deleted identifier, can pick the other,
1506 // since deleted expressions should not be ambiguous if there is another option
1507 // that is at least as good
1508 if ( findDeletedExpr( candidate->expr ) ) {
1509 // do nothing
1510 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1511 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1512 PRINT( std::cerr << "current is deleted" << std::endl; )
1513 found->second = PruneStruct{ candidate };
1514 } else {
1515 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1516 found->second.ambiguous = true;
1517 }
1518 } else {
1519 PRINT(
1520 std::cerr << "cost " << candidate->cost << " loses to "
1521 << found->second.candidate->cost << std::endl;
1522 )
1523 }
1524 } else {
1525 selected.emplace_hint( found, mangleName, candidate );
1526 }
1527 }
1528
1529 // report unambiguous min-cost candidates
1530 CandidateList out;
1531 for ( auto & target : selected ) {
1532 if ( target.second.ambiguous ) continue;
1533
1534 CandidateRef cand = target.second.candidate;
1535
1536 ast::ptr< ast::Type > newResult = cand->expr->result;
1537 cand->env.applyFree( newResult );
1538 cand->expr = ast::mutate_field(
1539 cand->expr.get(), &ast::Expr::result, move( newResult ) );
1540
1541 out.emplace_back( cand );
1542 }
1543 return out;
1544 }
1545
1546} // anonymous namespace
1547
1548void CandidateFinder::find( const ast::Expr * expr, ResolvMode mode ) {
1549 // Find alternatives for expression
1550 ast::Pass<Finder> finder{ *this };
1551 expr->accept( finder );
1552
1553 if ( mode.failFast && candidates.empty() ) {
1554 SemanticError( expr, "No reasonable alternatives for expression " );
1555 }
1556
1557 if ( mode.satisfyAssns || mode.prune ) {
1558 // trim candidates to just those where the assertions are satisfiable
1559 // - necessary pre-requisite to pruning
1560 CandidateList satisfied;
1561 std::vector< std::string > errors;
1562 for ( CandidateRef & candidate : candidates ) {
1563 satisfyAssertions( candidate, localSyms, satisfied, errors );
1564 }
1565
1566 // fail early if none such
1567 if ( mode.failFast && satisfied.empty() ) {
1568 std::ostringstream stream;
1569 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1570 for ( const auto& err : errors ) {
1571 stream << err;
1572 }
1573 SemanticError( expr->location, stream.str() );
1574 }
1575
1576 // reset candidates
1577 candidates = move( satisfied );
1578 }
1579
1580 if ( mode.prune ) {
1581 // trim candidates to single best one
1582 PRINT(
1583 std::cerr << "alternatives before prune:" << std::endl;
1584 print( std::cerr, candidates );
1585 )
1586
1587 CandidateList pruned = pruneCandidates( candidates );
1588
1589 if ( mode.failFast && pruned.empty() ) {
1590 std::ostringstream stream;
1591 CandidateList winners = findMinCost( candidates );
1592 stream << "Cannot choose between " << winners.size() << " alternatives for "
1593 "expression\n";
1594 ast::print( stream, expr );
1595 stream << " Alternatives are:\n";
1596 print( stream, winners, 1 );
1597 SemanticError( expr->location, stream.str() );
1598 }
1599
1600 auto oldsize = candidates.size();
1601 candidates = move( pruned );
1602
1603 PRINT(
1604 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
1605 )
1606 PRINT(
1607 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
1608 << std::endl;
1609 )
1610 }
1611
1612 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
1613 // adjusted
1614 if ( mode.adjust ) {
1615 for ( CandidateRef & r : candidates ) {
1616 r->expr = ast::mutate_field(
1617 r->expr.get(), &ast::Expr::result,
1618 adjustExprType( r->expr->result, r->env, localSyms ) );
1619 }
1620 }
1621
1622 // Central location to handle gcc extension keyword, etc. for all expressions
1623 for ( CandidateRef & r : candidates ) {
1624 if ( r->expr->extension != expr->extension ) {
1625 r->expr.get_and_mutate()->extension = expr->extension;
1626 }
1627 }
1628}
1629
1630std::vector< CandidateFinder > CandidateFinder::findSubExprs(
1631 const std::vector< ast::ptr< ast::Expr > > & xs
1632) {
1633 std::vector< CandidateFinder > out;
1634
1635 for ( const auto & x : xs ) {
1636 out.emplace_back( localSyms, env );
1637 out.back().find( x, ResolvMode::withAdjustment() );
1638
1639 PRINT(
1640 std::cerr << "findSubExprs" << std::endl;
1641 print( std::cerr, out.back().candidates );
1642 )
1643 }
1644
1645 return out;
1646}
1647
1648} // namespace ResolvExpr
1649
1650// Local Variables: //
1651// tab-width: 4 //
1652// mode: c++ //
1653// compile-command: "make install" //
1654// End: //
Note: See TracBrowser for help on using the repository browser.