source: src/ResolvExpr/CandidateFinder.cpp@ 0f19f5e5

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation jenkins-sandbox new-ast new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 0f19f5e5 was 18e683b, checked in by Aaron Moss <a3moss@…>, 6 years ago

Port LinkReferenceToTypes pass
  • 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 : Aaron B. Moss
12// Last Modified On : Wed Jun 5 14:30:00 2019
13// Update Count : 1
14//
15
16#include "CandidateFinder.hpp"
17
18#include <deque>
19#include <iterator> // for back_inserter
20#include <sstream>
21#include <string>
22#include <unordered_map>
23#include <vector>
24
25#include "Candidate.hpp"
26#include "CompilationState.h"
27#include "Cost.h"
28#include "ExplodedArg.hpp"
29#include "RenameVars.h" // for renameTyVars
30#include "Resolver.h"
31#include "ResolveTypeof.h"
32#include "SatisfyAssertions.hpp"
33#include "typeops.h" // for adjustExprType, conversionCost, polyCost, specCost
34#include "Unify.h"
35#include "AST/Expr.hpp"
36#include "AST/Node.hpp"
37#include "AST/Pass.hpp"
38#include "AST/Print.hpp"
39#include "AST/SymbolTable.hpp"
40#include "AST/Type.hpp"
41#include "Common/utility.h" // for move, copy
42#include "SymTab/Mangler.h"
43#include "SymTab/Validate.h" // for validateType
44#include "Tuples/Tuples.h" // for handleTupleAssignment
45
46#define PRINT( text ) if ( resolvep ) { text }
47
48namespace ResolvExpr {
49
50const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
51 if ( expr->result.as< ast::ReferenceType >() ) {
52 // cast away reference from expr
53 cost.incReference();
54 return new ast::CastExpr{ expr, expr->result->stripReferences() };
55 }
56
57 return expr;
58}
59
60/// Unique identifier for matching expression resolutions to their requesting expression
61UniqueId globalResnSlot = 0;
62
63Cost computeConversionCost(
64 const ast::Type * argType, const ast::Type * paramType, const ast::SymbolTable & symtab,
65 const ast::TypeEnvironment & env
66) {
67 PRINT(
68 std::cerr << std::endl << "converting ";
69 ast::print( std::cerr, argType, 2 );
70 std::cerr << std::endl << " to ";
71 ast::print( std::cerr, paramType, 2 );
72 std::cerr << std::endl << "environment is: ";
73 ast::print( std::cerr, env, 2 );
74 std::cerr << std::endl;
75 )
76 Cost convCost = conversionCost( argType, paramType, symtab, env );
77 PRINT(
78 std::cerr << std::endl << "cost is " << convCost << std::endl;
79 )
80 if ( convCost == Cost::infinity ) return convCost;
81 convCost.incPoly( polyCost( paramType, symtab, env ) + polyCost( argType, symtab, env ) );
82 PRINT(
83 std::cerr << "cost with polycost is " << convCost << std::endl;
84 )
85 return convCost;
86}
87
88namespace {
89 /// First index is which argument, second is which alternative, third is which exploded element
90 using ExplodedArgs_new = std::deque< std::vector< ExplodedArg > >;
91
92 /// Returns a list of alternatives with the minimum cost in the given list
93 CandidateList findMinCost( const CandidateList & candidates ) {
94 CandidateList out;
95 Cost minCost = Cost::infinity;
96 for ( const CandidateRef & r : candidates ) {
97 if ( r->cost < minCost ) {
98 minCost = r->cost;
99 out.clear();
100 out.emplace_back( r );
101 } else if ( r->cost == minCost ) {
102 out.emplace_back( r );
103 }
104 }
105 return out;
106 }
107
108 /// Computes conversion cost for a given expression to a given type
109 const ast::Expr * computeExpressionConversionCost(
110 const ast::Expr * arg, const ast::Type * paramType, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env, Cost & outCost
111 ) {
112 Cost convCost = computeConversionCost( arg->result, paramType, symtab, env );
113 outCost += convCost;
114
115 // If there is a non-zero conversion cost, ignoring poly cost, then the expression requires
116 // conversion. Ignore poly cost for now, since this requires resolution of the cast to
117 // infer parameters and this does not currently work for the reason stated below
118 Cost tmpCost = convCost;
119 tmpCost.incPoly( -tmpCost.get_polyCost() );
120 if ( tmpCost != Cost::zero ) {
121 ast::ptr< ast::Type > newType = paramType;
122 env.apply( newType );
123 return new ast::CastExpr{ arg, newType };
124
125 // xxx - *should* be able to resolve this cast, but at the moment pointers are not
126 // castable to zero_t, but are implicitly convertible. This is clearly inconsistent,
127 // once this is fixed it should be possible to resolve the cast.
128 // xxx - this isn't working, it appears because type1 (parameter) is seen as widenable,
129 // but it shouldn't be because this makes the conversion from DT* to DT* since
130 // commontype(zero_t, DT*) is DT*, rather than nothing
131
132 // CandidateFinder finder{ symtab, env };
133 // finder.find( arg, ResolvMode::withAdjustment() );
134 // assertf( finder.candidates.size() > 0,
135 // "Somehow castable expression failed to find alternatives." );
136 // assertf( finder.candidates.size() == 1,
137 // "Somehow got multiple alternatives for known cast expression." );
138 // return finder.candidates.front()->expr;
139 }
140
141 return arg;
142 }
143
144 /// Computes conversion cost for a given candidate
145 Cost computeApplicationConversionCost(
146 CandidateRef cand, const ast::SymbolTable & symtab
147 ) {
148 auto appExpr = cand->expr.strict_as< ast::ApplicationExpr >();
149 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
150 auto function = pointer->base.strict_as< ast::FunctionType >();
151
152 Cost convCost = Cost::zero;
153 const auto & params = function->params;
154 auto param = params.begin();
155 auto & args = appExpr->args;
156
157 for ( unsigned i = 0; i < args.size(); ++i ) {
158 const ast::Type * argType = args[i]->result;
159 PRINT(
160 std::cerr << "arg expression:" << std::endl;
161 ast::print( std::cerr, args[i], 2 );
162 std::cerr << "--- results are" << std::endl;
163 ast::print( std::cerr, argType, 2 );
164 )
165
166 if ( param == params.end() ) {
167 if ( function->isVarArgs ) {
168 convCost.incUnsafe();
169 PRINT( std::cerr << "end of params with varargs function: inc unsafe: "
170 << convCost << std::endl; ; )
171 // convert reference-typed expressions into value-typed expressions
172 cand->expr = ast::mutate_field_index(
173 appExpr, &ast::ApplicationExpr::args, i,
174 referenceToRvalueConversion( args[i], convCost ) );
175 continue;
176 } else return Cost::infinity;
177 }
178
179 if ( auto def = args[i].as< ast::DefaultArgExpr >() ) {
180 // Default arguments should be free - don't include conversion cost.
181 // Unwrap them here because they are not relevant to the rest of the system
182 cand->expr = ast::mutate_field_index(
183 appExpr, &ast::ApplicationExpr::args, i, def->expr );
184 ++param;
185 continue;
186 }
187
188 // mark conversion cost and also specialization cost of param type
189 const ast::Type * paramType = (*param)->get_type();
190 cand->expr = ast::mutate_field_index(
191 appExpr, &ast::ApplicationExpr::args, i,
192 computeExpressionConversionCost(
193 args[i], paramType, symtab, cand->env, convCost ) );
194 convCost.decSpec( specCost( paramType ) );
195 ++param; // can't be in for-loop update because of the continue
196 }
197
198 if ( param != params.end() ) return Cost::infinity;
199
200 // specialization cost of return types can't be accounted for directly, it disables
201 // otherwise-identical calls, like this example based on auto-newline in the I/O lib:
202 //
203 // forall(otype OS) {
204 // void ?|?(OS&, int); // with newline
205 // OS& ?|?(OS&, int); // no newline, always chosen due to more specialization
206 // }
207
208 // mark type variable and specialization cost of forall clause
209 convCost.incVar( function->forall.size() );
210 for ( const ast::TypeDecl * td : function->forall ) {
211 convCost.decSpec( td->assertions.size() );
212 }
213
214 return convCost;
215 }
216
217 void makeUnifiableVars(
218 const ast::ParameterizedType * type, ast::OpenVarSet & unifiableVars,
219 ast::AssertionSet & need
220 ) {
221 for ( const ast::TypeDecl * tyvar : type->forall ) {
222 unifiableVars[ tyvar->name ] = ast::TypeDecl::Data{ tyvar };
223 for ( const ast::DeclWithType * assn : tyvar->assertions ) {
224 need[ assn ].isUsed = true;
225 }
226 }
227 }
228
229 /// Gets a default value from an initializer, nullptr if not present
230 const ast::ConstantExpr * getDefaultValue( const ast::Init * init ) {
231 if ( auto si = dynamic_cast< const ast::SingleInit * >( init ) ) {
232 if ( auto ce = si->value.as< ast::CastExpr >() ) {
233 return ce->arg.as< ast::ConstantExpr >();
234 } else {
235 return si->value.as< ast::ConstantExpr >();
236 }
237 }
238 return nullptr;
239 }
240
241 /// State to iteratively build a match of parameter expressions to arguments
242 struct ArgPack {
243 std::size_t parent; ///< Index of parent pack
244 ast::ptr< ast::Expr > expr; ///< The argument stored here
245 Cost cost; ///< The cost of this argument
246 ast::TypeEnvironment env; ///< Environment for this pack
247 ast::AssertionSet need; ///< Assertions outstanding for this pack
248 ast::AssertionSet have; ///< Assertions found for this pack
249 ast::OpenVarSet open; ///< Open variables for this pack
250 unsigned nextArg; ///< Index of next argument in arguments list
251 unsigned tupleStart; ///< Number of tuples that start at this index
252 unsigned nextExpl; ///< Index of next exploded element
253 unsigned explAlt; ///< Index of alternative for nextExpl > 0
254
255 ArgPack()
256 : parent( 0 ), expr(), cost( Cost::zero ), env(), need(), have(), open(), nextArg( 0 ),
257 tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
258
259 ArgPack(
260 const ast::TypeEnvironment & env, const ast::AssertionSet & need,
261 const ast::AssertionSet & have, const ast::OpenVarSet & open )
262 : parent( 0 ), expr(), cost( Cost::zero ), env( env ), need( need ), have( have ),
263 open( open ), nextArg( 0 ), tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
264
265 ArgPack(
266 std::size_t parent, const ast::Expr * expr, ast::TypeEnvironment && env,
267 ast::AssertionSet && need, ast::AssertionSet && have, ast::OpenVarSet && open,
268 unsigned nextArg, unsigned tupleStart = 0, Cost cost = Cost::zero,
269 unsigned nextExpl = 0, unsigned explAlt = 0 )
270 : parent(parent), expr( expr ), cost( cost ), env( move( env ) ), need( move( need ) ),
271 have( move( have ) ), open( move( open ) ), nextArg( nextArg ), tupleStart( tupleStart ),
272 nextExpl( nextExpl ), explAlt( explAlt ) {}
273
274 ArgPack(
275 const ArgPack & o, ast::TypeEnvironment && env, ast::AssertionSet && need,
276 ast::AssertionSet && have, ast::OpenVarSet && open, unsigned nextArg, Cost added )
277 : parent( o.parent ), expr( o.expr ), cost( o.cost + added ), env( move( env ) ),
278 need( move( need ) ), have( move( have ) ), open( move( open ) ), nextArg( nextArg ),
279 tupleStart( o.tupleStart ), nextExpl( 0 ), explAlt( 0 ) {}
280
281 /// true if this pack is in the middle of an exploded argument
282 bool hasExpl() const { return nextExpl > 0; }
283
284 /// Gets the list of exploded candidates for this pack
285 const ExplodedArg & getExpl( const ExplodedArgs_new & args ) const {
286 return args[ nextArg-1 ][ explAlt ];
287 }
288
289 /// Ends a tuple expression, consolidating the appropriate args
290 void endTuple( const std::vector< ArgPack > & packs ) {
291 // add all expressions in tuple to list, summing cost
292 std::deque< const ast::Expr * > exprs;
293 const ArgPack * pack = this;
294 if ( expr ) { exprs.emplace_front( expr ); }
295 while ( pack->tupleStart == 0 ) {
296 pack = &packs[pack->parent];
297 exprs.emplace_front( pack->expr );
298 cost += pack->cost;
299 }
300 // reset pack to appropriate tuple
301 std::vector< ast::ptr< ast::Expr > > exprv( exprs.begin(), exprs.end() );
302 expr = new ast::TupleExpr{ expr->location, move( exprv ) };
303 tupleStart = pack->tupleStart - 1;
304 parent = pack->parent;
305 }
306 };
307
308 /// Instantiates an argument to match a parameter, returns false if no matching results left
309 bool instantiateArgument(
310 const ast::Type * paramType, const ast::Init * init, const ExplodedArgs_new & args,
311 std::vector< ArgPack > & results, std::size_t & genStart, const ast::SymbolTable & symtab,
312 unsigned nTuples = 0
313 ) {
314 if ( auto tupleType = dynamic_cast< const ast::TupleType * >( paramType ) ) {
315 // paramType is a TupleType -- group args into a TupleExpr
316 ++nTuples;
317 for ( const ast::Type * type : *tupleType ) {
318 // xxx - dropping initializer changes behaviour from previous, but seems correct
319 // ^^^ need to handle the case where a tuple has a default argument
320 if ( ! instantiateArgument(
321 type, nullptr, args, results, genStart, symtab, nTuples ) ) return false;
322 nTuples = 0;
323 }
324 // re-constitute tuples for final generation
325 for ( auto i = genStart; i < results.size(); ++i ) {
326 results[i].endTuple( results );
327 }
328 return true;
329 } else if ( const ast::TypeInstType * ttype = Tuples::isTtype( paramType ) ) {
330 // paramType is a ttype, consumes all remaining arguments
331
332 // completed tuples; will be spliced to end of results to finish
333 std::vector< ArgPack > finalResults{};
334
335 // iterate until all results completed
336 std::size_t genEnd;
337 ++nTuples;
338 do {
339 genEnd = results.size();
340
341 // add another argument to results
342 for ( std::size_t i = genStart; i < genEnd; ++i ) {
343 unsigned nextArg = results[i].nextArg;
344
345 // use next element of exploded tuple if present
346 if ( results[i].hasExpl() ) {
347 const ExplodedArg & expl = results[i].getExpl( args );
348
349 unsigned nextExpl = results[i].nextExpl + 1;
350 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
351
352 results.emplace_back(
353 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
354 copy( results[i].need ), copy( results[i].have ),
355 copy( results[i].open ), nextArg, nTuples, Cost::zero, nextExpl,
356 results[i].explAlt );
357
358 continue;
359 }
360
361 // finish result when out of arguments
362 if ( nextArg >= args.size() ) {
363 ArgPack newResult{
364 results[i].env, results[i].need, results[i].have, results[i].open };
365 newResult.nextArg = nextArg;
366 const ast::Type * argType = nullptr;
367
368 if ( nTuples > 0 || ! results[i].expr ) {
369 // first iteration or no expression to clone,
370 // push empty tuple expression
371 newResult.parent = i;
372 std::vector< ast::ptr< ast::Expr > > emptyList;
373 newResult.expr =
374 new ast::TupleExpr{ CodeLocation{}, move( emptyList ) };
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( 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], move( env ), copy( results[i].need ),
427 copy( results[i].have ), move( open ), nextArg + 1, expl.cost );
428
429 continue;
430 }
431
432 // add new result
433 results.emplace_back(
434 i, expl.exprs.front(), move( env ), copy( results[i].need ),
435 copy( results[i].have ), 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( 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, move( env ), move( need ), move( have ), 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 }, move( env ),
498 move( need ), move( have ), 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], move( env ), move( need ), move( have ), 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, move( env ), move( need ), move( have ), 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();
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, 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 struct Finder final : public ast::WithShortCircuiting {
597 CandidateFinder & selfFinder;
598 const ast::SymbolTable & symtab;
599 CandidateList & candidates;
600 const ast::TypeEnvironment & tenv;
601 ast::ptr< ast::Type > & targetType;
602
603 Finder( CandidateFinder & f )
604 : selfFinder( f ), symtab( f.symtab ), 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 parameter
679 // 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->result->is_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, symtab, cand->env );
1028 PRINT(
1029 std::cerr << "working on cast with result: " << toType << std::endl;
1030 std::cerr << "and expr type: " << cand->expr->result << std::endl;
1031 std::cerr << "env: " << cand->env << std::endl;
1032 )
1033 if ( thisCost != Cost::infinity ) {
1034 PRINT(
1035 std::cerr << "has finite cost." << std::endl;
1036 )
1037 // count one safe conversion for each value that is thrown away
1038 thisCost.incSafe( discardedValues );
1039 CandidateRef newCand = std::make_shared<Candidate>(
1040 restructureCast( cand->expr, toType, castExpr->isGenerated ),
1041 copy( cand->env ), move( open ), move( need ), cand->cost,
1042 cand->cost + thisCost );
1043 inferParameters( newCand, matches );
1044 }
1045 }
1046
1047 // select first on argument cost, then conversion cost
1048 CandidateList minArgCost = findMinCost( matches );
1049 promoteCvtCost( minArgCost );
1050 candidates = findMinCost( minArgCost );
1051 }
1052
1053 void postvisit( const ast::VirtualCastExpr * castExpr ) {
1054 assertf( castExpr->result, "Implicit virtual cast targets not yet supported." );
1055 CandidateFinder finder{ symtab, tenv };
1056 // don't prune here, all alternatives guaranteed to have same type
1057 finder.find( castExpr->arg, ResolvMode::withoutPrune() );
1058 for ( CandidateRef & r : finder.candidates ) {
1059 addCandidate(
1060 *r,
1061 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
1062 }
1063 }
1064
1065 void postvisit( const ast::UntypedMemberExpr * memberExpr ) {
1066 CandidateFinder aggFinder{ symtab, tenv };
1067 aggFinder.find( memberExpr->aggregate, ResolvMode::withAdjustment() );
1068 for ( CandidateRef & agg : aggFinder.candidates ) {
1069 // it's okay for the aggregate expression to have reference type -- cast it to the
1070 // base type to treat the aggregate as the referenced value
1071 Cost addedCost = Cost::zero;
1072 agg->expr = referenceToRvalueConversion( agg->expr, addedCost );
1073
1074 // find member of the given type
1075 if ( auto structInst = agg->expr->result.as< ast::StructInstType >() ) {
1076 addAggMembers(
1077 structInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1078 } else if ( auto unionInst = agg->expr->result.as< ast::UnionInstType >() ) {
1079 addAggMembers(
1080 unionInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1081 } else if ( auto tupleType = agg->expr->result.as< ast::TupleType >() ) {
1082 addTupleMembers( tupleType, agg->expr, *agg, addedCost, memberExpr->member );
1083 }
1084 }
1085 }
1086
1087 void postvisit( const ast::MemberExpr * memberExpr ) {
1088 addCandidate( memberExpr, tenv );
1089 }
1090
1091 void postvisit( const ast::NameExpr * nameExpr ) {
1092 std::vector< ast::SymbolTable::IdData > declList = symtab.lookupId( nameExpr->name );
1093 PRINT( std::cerr << "nameExpr is " << nameExpr->name << std::endl; )
1094 for ( auto & data : declList ) {
1095 Cost cost = Cost::zero;
1096 ast::Expr * newExpr = data.combine( nameExpr->location, cost );
1097
1098 CandidateRef newCand = std::make_shared<Candidate>(
1099 newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, Cost::zero,
1100 cost );
1101 PRINT(
1102 std::cerr << "decl is ";
1103 ast::print( std::cerr, data.id );
1104 std::cerr << std::endl;
1105 std::cerr << "newExpr is ";
1106 ast::print( std::cerr, newExpr );
1107 std::cerr << std::endl;
1108 )
1109 newCand->expr = ast::mutate_field(
1110 newCand->expr.get(), &ast::Expr::result,
1111 renameTyVars( newCand->expr->result ) );
1112 // add anonymous member interpretations whenever an aggregate value type is seen
1113 // as a name expression
1114 addAnonConversions( newCand );
1115 candidates.emplace_back( move( newCand ) );
1116 }
1117 }
1118
1119 void postvisit( const ast::VariableExpr * variableExpr ) {
1120 // not sufficient to just pass `variableExpr` here, type might have changed since
1121 // creation
1122 addCandidate(
1123 new ast::VariableExpr{ variableExpr->location, variableExpr->var }, tenv );
1124 }
1125
1126 void postvisit( const ast::ConstantExpr * constantExpr ) {
1127 addCandidate( constantExpr, tenv );
1128 }
1129
1130 void postvisit( const ast::SizeofExpr * sizeofExpr ) {
1131 if ( sizeofExpr->type ) {
1132 addCandidate(
1133 new ast::SizeofExpr{
1134 sizeofExpr->location, resolveTypeof( sizeofExpr->type, symtab ) },
1135 tenv );
1136 } else {
1137 // find all candidates for the argument to sizeof
1138 CandidateFinder finder{ symtab, tenv };
1139 finder.find( sizeofExpr->expr );
1140 // find the lowest-cost candidate, otherwise ambiguous
1141 CandidateList winners = findMinCost( finder.candidates );
1142 if ( winners.size() != 1 ) {
1143 SemanticError(
1144 sizeofExpr->expr.get(), "Ambiguous expression in sizeof operand: " );
1145 }
1146 // return the lowest-cost candidate
1147 CandidateRef & choice = winners.front();
1148 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1149 choice->cost = Cost::zero;
1150 addCandidate( *choice, new ast::SizeofExpr{ sizeofExpr->location, choice->expr } );
1151 }
1152 }
1153
1154 void postvisit( const ast::AlignofExpr * alignofExpr ) {
1155 if ( alignofExpr->type ) {
1156 addCandidate(
1157 new ast::AlignofExpr{
1158 alignofExpr->location, resolveTypeof( alignofExpr->type, symtab ) },
1159 tenv );
1160 } else {
1161 // find all candidates for the argument to alignof
1162 CandidateFinder finder{ symtab, tenv };
1163 finder.find( alignofExpr->expr );
1164 // find the lowest-cost candidate, otherwise ambiguous
1165 CandidateList winners = findMinCost( finder.candidates );
1166 if ( winners.size() != 1 ) {
1167 SemanticError(
1168 alignofExpr->expr.get(), "Ambiguous expression in alignof operand: " );
1169 }
1170 // return the lowest-cost candidate
1171 CandidateRef & choice = winners.front();
1172 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1173 choice->cost = Cost::zero;
1174 addCandidate(
1175 *choice, new ast::AlignofExpr{ alignofExpr->location, choice->expr } );
1176 }
1177 }
1178
1179 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
1180 const ast::ReferenceToType * aggInst;
1181 if (( aggInst = offsetofExpr->type.as< ast::StructInstType >() )) ;
1182 else if (( aggInst = offsetofExpr->type.as< ast::UnionInstType >() )) ;
1183 else return;
1184
1185 for ( const ast::Decl * member : aggInst->lookup( offsetofExpr->member ) ) {
1186 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( member );
1187 addCandidate(
1188 new ast::OffsetofExpr{ offsetofExpr->location, aggInst, dwt }, tenv );
1189 }
1190 }
1191
1192 void postvisit( const ast::OffsetofExpr * offsetofExpr ) {
1193 addCandidate( offsetofExpr, tenv );
1194 }
1195
1196 void postvisit( const ast::OffsetPackExpr * offsetPackExpr ) {
1197 addCandidate( offsetPackExpr, tenv );
1198 }
1199
1200 void postvisit( const ast::LogicalExpr * logicalExpr ) {
1201 CandidateFinder finder1{ symtab, tenv };
1202 finder1.find( logicalExpr->arg1, ResolvMode::withAdjustment() );
1203 if ( finder1.candidates.empty() ) return;
1204
1205 CandidateFinder finder2{ symtab, tenv };
1206 finder2.find( logicalExpr->arg2, ResolvMode::withAdjustment() );
1207 if ( finder2.candidates.empty() ) return;
1208
1209 for ( const CandidateRef & r1 : finder1.candidates ) {
1210 for ( const CandidateRef & r2 : finder2.candidates ) {
1211 ast::TypeEnvironment env{ r1->env };
1212 env.simpleCombine( r2->env );
1213 ast::OpenVarSet open{ r1->open };
1214 mergeOpenVars( open, r2->open );
1215 ast::AssertionSet need;
1216 mergeAssertionSet( need, r1->need );
1217 mergeAssertionSet( need, r2->need );
1218
1219 addCandidate(
1220 new ast::LogicalExpr{
1221 logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
1222 move( env ), move( open ), move( need ), r1->cost + r2->cost );
1223 }
1224 }
1225 }
1226
1227 void postvisit( const ast::ConditionalExpr * conditionalExpr ) {
1228 // candidates for condition
1229 CandidateFinder finder1{ symtab, tenv };
1230 finder1.find( conditionalExpr->arg1, ResolvMode::withAdjustment() );
1231 if ( finder1.candidates.empty() ) return;
1232
1233 // candidates for true result
1234 CandidateFinder finder2{ symtab, tenv };
1235 finder2.find( conditionalExpr->arg2, ResolvMode::withAdjustment() );
1236 if ( finder2.candidates.empty() ) return;
1237
1238 // candidates for false result
1239 CandidateFinder finder3{ symtab, tenv };
1240 finder3.find( conditionalExpr->arg3, ResolvMode::withAdjustment() );
1241 if ( finder3.candidates.empty() ) return;
1242
1243 for ( const CandidateRef & r1 : finder1.candidates ) {
1244 for ( const CandidateRef & r2 : finder2.candidates ) {
1245 for ( const CandidateRef & r3 : finder3.candidates ) {
1246 ast::TypeEnvironment env{ r1->env };
1247 env.simpleCombine( r2->env );
1248 env.simpleCombine( r3->env );
1249 ast::OpenVarSet open{ r1->open };
1250 mergeOpenVars( open, r2->open );
1251 mergeOpenVars( open, r3->open );
1252 ast::AssertionSet need;
1253 mergeAssertionSet( need, r1->need );
1254 mergeAssertionSet( need, r2->need );
1255 mergeAssertionSet( need, r3->need );
1256 ast::AssertionSet have;
1257
1258 // unify true and false results, then infer parameters to produce new
1259 // candidates
1260 ast::ptr< ast::Type > common;
1261 if (
1262 unify(
1263 r2->expr->result, r3->expr->result, env, need, have, open, symtab,
1264 common )
1265 ) {
1266 // generate typed expression
1267 ast::ConditionalExpr * newExpr = new ast::ConditionalExpr{
1268 conditionalExpr->location, r1->expr, r2->expr, r3->expr };
1269 newExpr->result = common ? common : r2->expr->result;
1270 // convert both options to result type
1271 Cost cost = r1->cost + r2->cost + r3->cost;
1272 newExpr->arg2 = computeExpressionConversionCost(
1273 newExpr->arg2, newExpr->result, symtab, env, cost );
1274 newExpr->arg3 = computeExpressionConversionCost(
1275 newExpr->arg3, newExpr->result, symtab, env, cost );
1276 // output candidate
1277 CandidateRef newCand = std::make_shared<Candidate>(
1278 newExpr, move( env ), move( open ), move( need ), cost );
1279 inferParameters( newCand, candidates );
1280 }
1281 }
1282 }
1283 }
1284 }
1285
1286 void postvisit( const ast::CommaExpr * commaExpr ) {
1287 ast::TypeEnvironment env{ tenv };
1288 ast::ptr< ast::Expr > arg1 = resolveInVoidContext( commaExpr->arg1, symtab, env );
1289
1290 CandidateFinder finder2{ symtab, env };
1291 finder2.find( commaExpr->arg2, ResolvMode::withAdjustment() );
1292
1293 for ( const CandidateRef & r2 : finder2.candidates ) {
1294 addCandidate( *r2, new ast::CommaExpr{ commaExpr->location, arg1, r2->expr } );
1295 }
1296 }
1297
1298 void postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr ) {
1299 addCandidate( ctorExpr, tenv );
1300 }
1301
1302 void postvisit( const ast::ConstructorExpr * ctorExpr ) {
1303 CandidateFinder finder{ symtab, tenv };
1304 finder.find( ctorExpr->callExpr, ResolvMode::withoutPrune() );
1305 for ( CandidateRef & r : finder.candidates ) {
1306 addCandidate( *r, new ast::ConstructorExpr{ ctorExpr->location, r->expr } );
1307 }
1308 }
1309
1310 void postvisit( const ast::RangeExpr * rangeExpr ) {
1311 // resolve low and high, accept candidates where low and high types unify
1312 CandidateFinder finder1{ symtab, tenv };
1313 finder1.find( rangeExpr->low, ResolvMode::withAdjustment() );
1314 if ( finder1.candidates.empty() ) return;
1315
1316 CandidateFinder finder2{ symtab, tenv };
1317 finder2.find( rangeExpr->high, ResolvMode::withAdjustment() );
1318 if ( finder2.candidates.empty() ) return;
1319
1320 for ( const CandidateRef & r1 : finder1.candidates ) {
1321 for ( const CandidateRef & r2 : finder2.candidates ) {
1322 ast::TypeEnvironment env{ r1->env };
1323 env.simpleCombine( r2->env );
1324 ast::OpenVarSet open{ r1->open };
1325 mergeOpenVars( open, r2->open );
1326 ast::AssertionSet need;
1327 mergeAssertionSet( need, r1->need );
1328 mergeAssertionSet( need, r2->need );
1329 ast::AssertionSet have;
1330
1331 ast::ptr< ast::Type > common;
1332 if (
1333 unify(
1334 r1->expr->result, r2->expr->result, env, need, have, open, symtab,
1335 common )
1336 ) {
1337 // generate new expression
1338 ast::RangeExpr * newExpr =
1339 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1340 newExpr->result = common ? common : r1->expr->result;
1341 // add candidate
1342 CandidateRef newCand = std::make_shared<Candidate>(
1343 newExpr, move( env ), move( open ), move( need ),
1344 r1->cost + r2->cost );
1345 inferParameters( newCand, candidates );
1346 }
1347 }
1348 }
1349 }
1350
1351 void postvisit( const ast::UntypedTupleExpr * tupleExpr ) {
1352 std::vector< CandidateFinder > subCandidates =
1353 selfFinder.findSubExprs( tupleExpr->exprs );
1354 std::vector< CandidateList > possibilities;
1355 combos( subCandidates.begin(), subCandidates.end(), back_inserter( possibilities ) );
1356
1357 for ( const CandidateList & subs : possibilities ) {
1358 std::vector< ast::ptr< ast::Expr > > exprs;
1359 exprs.reserve( subs.size() );
1360 for ( const CandidateRef & sub : subs ) { exprs.emplace_back( sub->expr ); }
1361
1362 ast::TypeEnvironment env;
1363 ast::OpenVarSet open;
1364 ast::AssertionSet need;
1365 for ( const CandidateRef & sub : subs ) {
1366 env.simpleCombine( sub->env );
1367 mergeOpenVars( open, sub->open );
1368 mergeAssertionSet( need, sub->need );
1369 }
1370
1371 addCandidate(
1372 new ast::TupleExpr{ tupleExpr->location, move( exprs ) },
1373 move( env ), move( open ), move( need ), sumCost( subs ) );
1374 }
1375 }
1376
1377 void postvisit( const ast::TupleExpr * tupleExpr ) {
1378 addCandidate( tupleExpr, tenv );
1379 }
1380
1381 void postvisit( const ast::TupleIndexExpr * tupleExpr ) {
1382 addCandidate( tupleExpr, tenv );
1383 }
1384
1385 void postvisit( const ast::TupleAssignExpr * tupleExpr ) {
1386 addCandidate( tupleExpr, tenv );
1387 }
1388
1389 void postvisit( const ast::UniqueExpr * unqExpr ) {
1390 CandidateFinder finder{ symtab, tenv };
1391 finder.find( unqExpr->expr, ResolvMode::withAdjustment() );
1392 for ( CandidateRef & r : finder.candidates ) {
1393 // ensure that the the id is passed on so that the expressions are "linked"
1394 addCandidate( *r, new ast::UniqueExpr{ unqExpr->location, r->expr, unqExpr->id } );
1395 }
1396 }
1397
1398 void postvisit( const ast::StmtExpr * stmtExpr ) {
1399 addCandidate( resolveStmtExpr( stmtExpr, symtab ), tenv );
1400 }
1401
1402 void postvisit( const ast::UntypedInitExpr * initExpr ) {
1403 // handle each option like a cast
1404 CandidateList matches;
1405 PRINT(
1406 std::cerr << "untyped init expr: " << initExpr << std::endl;
1407 )
1408 // O(n^2) checks of d-types with e-types
1409 for ( const ast::InitAlternative & initAlt : initExpr->initAlts ) {
1410 // calculate target type
1411 const ast::Type * toType = resolveTypeof( initAlt.type, symtab );
1412 toType = SymTab::validateType( initExpr->location, toType, symtab );
1413 toType = adjustExprType( toType, tenv, symtab );
1414 // The call to find must occur inside this loop, otherwise polymorphic return
1415 // types are not bound to the initialization type, since return type variables are
1416 // only open for the duration of resolving the UntypedExpr.
1417 CandidateFinder finder{ symtab, tenv, toType };
1418 finder.find( initExpr->expr, ResolvMode::withAdjustment() );
1419 for ( CandidateRef & cand : finder.candidates ) {
1420 ast::TypeEnvironment env{ cand->env };
1421 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1422 ast::OpenVarSet open{ cand->open };
1423
1424 PRINT(
1425 std::cerr << " @ " << toType << " " << initAlt.designation << std::endl;
1426 )
1427
1428 // It is possible that a cast can throw away some values in a multiply-valued
1429 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of
1430 // the subexpression results that are cast directly. The candidate is invalid
1431 // if it has fewer results than there are types to cast to.
1432 int discardedValues = cand->expr->result->size() - toType->size();
1433 if ( discardedValues < 0 ) continue;
1434
1435 // unification run for side-effects
1436 unify( toType, cand->expr->result, env, need, have, open, symtab );
1437 Cost thisCost = castCost( cand->expr->result, toType, symtab, env );
1438
1439 if ( thisCost != Cost::infinity ) {
1440 // count one safe conversion for each value that is thrown away
1441 thisCost.incSafe( discardedValues );
1442 CandidateRef newCand = std::make_shared<Candidate>(
1443 new ast::InitExpr{
1444 initExpr->location, restructureCast( cand->expr, toType ),
1445 initAlt.designation },
1446 copy( cand->env ), move( open ), move( need ), cand->cost, thisCost );
1447 inferParameters( newCand, matches );
1448 }
1449 }
1450 }
1451
1452 // select first on argument cost, then conversion cost
1453 CandidateList minArgCost = findMinCost( matches );
1454 promoteCvtCost( minArgCost );
1455 candidates = findMinCost( minArgCost );
1456 }
1457
1458 void postvisit( const ast::InitExpr * ) {
1459 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
1460 }
1461
1462 void postvisit( const ast::DeletedExpr * ) {
1463 assertf( false, "CandidateFinder should never see a DeletedExpr." );
1464 }
1465
1466 void postvisit( const ast::GenericExpr * ) {
1467 assertf( false, "_Generic is not yet supported." );
1468 }
1469 };
1470
1471 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1472 /// return type. Skips ambiguous candidates.
1473 CandidateList pruneCandidates( CandidateList & candidates ) {
1474 struct PruneStruct {
1475 CandidateRef candidate;
1476 bool ambiguous;
1477
1478 PruneStruct() = default;
1479 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1480 };
1481
1482 // find lowest-cost candidate for each type
1483 std::unordered_map< std::string, PruneStruct > selected;
1484 for ( CandidateRef & candidate : candidates ) {
1485 std::string mangleName;
1486 {
1487 ast::ptr< ast::Type > newType = candidate->expr->result;
1488 candidate->env.apply( newType );
1489 mangleName = Mangle::mangle( newType );
1490 }
1491
1492 auto found = selected.find( mangleName );
1493 if ( found != selected.end() ) {
1494 if ( candidate->cost < found->second.candidate->cost ) {
1495 PRINT(
1496 std::cerr << "cost " << candidate->cost << " beats "
1497 << found->second.candidate->cost << std::endl;
1498 )
1499
1500 found->second = PruneStruct{ candidate };
1501 } else if ( candidate->cost == found->second.candidate->cost ) {
1502 // if one of the candidates contains a deleted identifier, can pick the other,
1503 // since deleted expressions should not be ambiguous if there is another option
1504 // that is at least as good
1505 if ( findDeletedExpr( candidate->expr ) ) {
1506 // do nothing
1507 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1508 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1509 PRINT( std::cerr << "current is deleted" << std::endl; )
1510 found->second = PruneStruct{ candidate };
1511 } else {
1512 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1513 found->second.ambiguous = true;
1514 }
1515 } else {
1516 PRINT(
1517 std::cerr << "cost " << candidate->cost << " loses to "
1518 << found->second.candidate->cost << std::endl;
1519 )
1520 }
1521 } else {
1522 selected.emplace_hint( found, mangleName, candidate );
1523 }
1524 }
1525
1526 // report unambiguous min-cost candidates
1527 CandidateList out;
1528 for ( auto & target : selected ) {
1529 if ( target.second.ambiguous ) continue;
1530
1531 CandidateRef cand = target.second.candidate;
1532
1533 ast::ptr< ast::Type > newResult = cand->expr->result;
1534 cand->env.applyFree( newResult );
1535 cand->expr = ast::mutate_field(
1536 cand->expr.get(), &ast::Expr::result, move( newResult ) );
1537
1538 out.emplace_back( cand );
1539 }
1540 return out;
1541 }
1542
1543} // anonymous namespace
1544
1545void CandidateFinder::find( const ast::Expr * expr, ResolvMode mode ) {
1546 // Find alternatives for expression
1547 ast::Pass<Finder> finder{ *this };
1548 expr->accept( finder );
1549
1550 if ( mode.failFast && candidates.empty() ) {
1551 SemanticError( expr, "No reasonable alternatives for expression " );
1552 }
1553
1554 if ( mode.satisfyAssns || mode.prune ) {
1555 // trim candidates to just those where the assertions are satisfiable
1556 // - necessary pre-requisite to pruning
1557 CandidateList satisfied;
1558 std::vector< std::string > errors;
1559 for ( CandidateRef & candidate : candidates ) {
1560 satisfyAssertions( candidate, symtab, satisfied, errors );
1561 }
1562
1563 // fail early if none such
1564 if ( mode.failFast && satisfied.empty() ) {
1565 std::ostringstream stream;
1566 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1567 for ( const auto& err : errors ) {
1568 stream << err;
1569 }
1570 SemanticError( expr->location, stream.str() );
1571 }
1572
1573 // reset candidates
1574 candidates = move( satisfied );
1575 }
1576
1577 if ( mode.prune ) {
1578 // trim candidates to single best one
1579 PRINT(
1580 std::cerr << "alternatives before prune:" << std::endl;
1581 print( std::cerr, candidates );
1582 )
1583
1584 CandidateList pruned = pruneCandidates( candidates );
1585
1586 if ( mode.failFast && pruned.empty() ) {
1587 std::ostringstream stream;
1588 CandidateList winners = findMinCost( candidates );
1589 stream << "Cannot choose between " << winners.size() << " alternatives for "
1590 "expression\n";
1591 ast::print( stream, expr );
1592 stream << " Alternatives are:\n";
1593 print( stream, winners, 1 );
1594 SemanticError( expr->location, stream.str() );
1595 }
1596
1597 auto oldsize = candidates.size();
1598 candidates = move( pruned );
1599
1600 PRINT(
1601 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
1602 )
1603 PRINT(
1604 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
1605 << std::endl;
1606 )
1607 }
1608
1609 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
1610 // adjusted
1611 if ( mode.adjust ) {
1612 for ( CandidateRef & r : candidates ) {
1613 r->expr = ast::mutate_field(
1614 r->expr.get(), &ast::Expr::result,
1615 adjustExprType( r->expr->result, r->env, symtab ) );
1616 }
1617 }
1618
1619 // Central location to handle gcc extension keyword, etc. for all expressions
1620 for ( CandidateRef & r : candidates ) {
1621 if ( r->expr->extension != expr->extension ) {
1622 r->expr.get_and_mutate()->extension = expr->extension;
1623 }
1624 }
1625}
1626
1627std::vector< CandidateFinder > CandidateFinder::findSubExprs(
1628 const std::vector< ast::ptr< ast::Expr > > & xs
1629) {
1630 std::vector< CandidateFinder > out;
1631
1632 for ( const auto & x : xs ) {
1633 out.emplace_back( symtab, env );
1634 out.back().find( x, ResolvMode::withAdjustment() );
1635
1636 PRINT(
1637 std::cerr << "findSubExprs" << std::endl;
1638 print( std::cerr, out.back().candidates );
1639 )
1640 }
1641
1642 return out;
1643}
1644
1645} // namespace ResolvExpr
1646
1647// Local Variables: //
1648// tab-width: 4 //
1649// mode: c++ //
1650// compile-command: "make install" //
1651// End: //
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