source: src/ResolvExpr/CandidateFinder.cpp@ 7d0881c

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 7d0881c was e0e9a0b, checked in by Aaron Moss <a3moss@…>, 6 years ago

Somewhat deeper clone for types with forall qualifiers.
  • Property mode set to 100644
File size: 59.4 KB
RevLine 
[99d4584]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
[432ce7a]18#include <deque>
[4b7cce6]19#include <iterator> // for back_inserter
[396037d]20#include <sstream>
[d57e349]21#include <string>
22#include <unordered_map>
[432ce7a]23#include <vector>
[396037d]24
25#include "Candidate.hpp"
26#include "CompilationState.h"
[d57e349]27#include "Cost.h"
[432ce7a]28#include "ExplodedArg.hpp"
[898ae07]29#include "RenameVars.h" // for renameTyVars
[d57e349]30#include "Resolver.h"
[c8e4d2f8]31#include "ResolveTypeof.h"
[396037d]32#include "SatisfyAssertions.hpp"
[9d5089e]33#include "typeops.h" // for adjustExprType, conversionCost, polyCost, specCost
[4b7cce6]34#include "Unify.h"
[99d4584]35#include "AST/Expr.hpp"
[396037d]36#include "AST/Node.hpp"
37#include "AST/Pass.hpp"
[d57e349]38#include "AST/Print.hpp"
[4b7cce6]39#include "AST/SymbolTable.hpp"
[432ce7a]40#include "AST/Type.hpp"
[c1ed2ee]41#include "Common/utility.h" // for move, copy
[d57e349]42#include "SymTab/Mangler.h"
[c8e4d2f8]43#include "SymTab/Validate.h" // for validateType
[432ce7a]44#include "Tuples/Tuples.h" // for handleTupleAssignment
[396037d]45
46#define PRINT( text ) if ( resolvep ) { text }
[99d4584]47
48namespace ResolvExpr {
49
[9d5089e]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();
[b8524ca]54 return new ast::CastExpr{ expr, expr->result->stripReferences() };
[9d5089e]55 }
56
57 return expr;
58}
59
60/// Unique identifier for matching expression resolutions to their requesting expression
61UniqueId globalResnSlot = 0;
[396037d]62
[b69233ac]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
[9d5089e]88namespace {
[432ce7a]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
[9d5089e]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 );
[b8524ca]123 return new ast::CastExpr{ arg, newType };
[9d5089e]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
[432ce7a]144 /// Computes conversion cost for a given candidate
145 Cost computeApplicationConversionCost(
[9d5089e]146 CandidateRef cand, const ast::SymbolTable & symtab
[432ce7a]147 ) {
[9d5089e]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
[e0e9a0b]550 return genEnd != results.size(); // were any new results added?
[432ce7a]551 }
552
[c8e4d2f8]553 /// Generate a cast expression from `arg` to `toType`
[898ae07]554 const ast::Expr * restructureCast(
[17a0ede2]555 ast::ptr< ast::Expr > & arg, const ast::Type * toType, ast::GeneratedFlag isGenerated = ast::GeneratedCast
[898ae07]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;
[c8e4d2f8]593 }
594
[396037d]595 /// Actually visits expressions to find their candidate interpretations
[9ea38de]596 class Finder final : public ast::WithShortCircuiting {
[396037d]597 const ast::SymbolTable & symtab;
[9ea38de]598 public:
599 CandidateFinder & selfFinder;
[396037d]600 CandidateList & candidates;
601 const ast::TypeEnvironment & tenv;
602 ast::ptr< ast::Type > & targetType;
603
604 Finder( CandidateFinder & f )
[9ea38de]605 : symtab( f.localSyms ), selfFinder( f ), candidates( f.candidates ), tenv( f.env ),
[396037d]606 targetType( f.targetType ) {}
607
[4b7cce6]608 void previsit( const ast::Node * ) { visit_children = false; }
609
610 /// Convenience to add candidate to list
611 template<typename... Args>
612 void addCandidate( Args &&... args ) {
613 candidates.emplace_back( new Candidate{ std::forward<Args>( args )... } );
614 }
615
616 void postvisit( const ast::ApplicationExpr * applicationExpr ) {
617 addCandidate( applicationExpr, tenv );
618 }
619
[9d5089e]620 /// Set up candidate assertions for inference
621 void inferParameters( CandidateRef & newCand, CandidateList & out ) {
622 // Set need bindings for any unbound assertions
623 UniqueId crntResnSlot = 0; // matching ID for this expression's assertions
624 for ( auto & assn : newCand->need ) {
625 // skip already-matched assertions
626 if ( assn.second.resnSlot != 0 ) continue;
627 // assign slot for expression if needed
628 if ( crntResnSlot == 0 ) { crntResnSlot = ++globalResnSlot; }
629 // fix slot to assertion
630 assn.second.resnSlot = crntResnSlot;
631 }
632 // pair slot to expression
633 if ( crntResnSlot != 0 ) {
634 newCand->expr.get_and_mutate()->inferred.resnSlots().emplace_back( crntResnSlot );
635 }
636
637 // add to output list; assertion satisfaction will occur later
638 out.emplace_back( newCand );
639 }
640
641 /// Completes a function candidate with arguments located
642 void validateFunctionCandidate(
643 const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results,
644 CandidateList & out
645 ) {
646 ast::ApplicationExpr * appExpr =
647 new ast::ApplicationExpr{ func->expr->location, func->expr };
648 // sum cost and accumulate arguments
649 std::deque< const ast::Expr * > args;
650 Cost cost = func->cost;
651 const ArgPack * pack = &result;
652 while ( pack->expr ) {
653 args.emplace_front( pack->expr );
654 cost += pack->cost;
655 pack = &results[pack->parent];
656 }
657 std::vector< ast::ptr< ast::Expr > > vargs( args.begin(), args.end() );
658 appExpr->args = move( vargs );
659 // build and validate new candidate
660 auto newCand =
661 std::make_shared<Candidate>( appExpr, result.env, result.open, result.need, cost );
662 PRINT(
663 std::cerr << "instantiate function success: " << appExpr << std::endl;
664 std::cerr << "need assertions:" << std::endl;
665 ast::print( std::cerr, result.need, 2 );
666 )
667 inferParameters( newCand, out );
668 }
669
[432ce7a]670 /// Builds a list of candidates for a function, storing them in out
671 void makeFunctionCandidates(
672 const CandidateRef & func, const ast::FunctionType * funcType,
673 const ExplodedArgs_new & args, CandidateList & out
674 ) {
[9d5089e]675 ast::OpenVarSet funcOpen;
676 ast::AssertionSet funcNeed, funcHave;
677 ast::TypeEnvironment funcEnv{ func->env };
678 makeUnifiableVars( funcType, funcOpen, funcNeed );
[e0e9a0b]679 // add all type variables as open variables now so that those not used in the
680 // parameter list are still considered open
[9d5089e]681 funcEnv.add( funcType->forall );
682
683 if ( targetType && ! targetType->isVoid() && ! funcType->returns.empty() ) {
684 // attempt to narrow based on expected target type
685 const ast::Type * returnType = funcType->returns.front()->get_type();
686 if ( ! unify(
687 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, symtab )
688 ) {
689 // unification failed, do not pursue this candidate
690 return;
691 }
692 }
693
694 // iteratively build matches, one parameter at a time
695 std::vector< ArgPack > results;
696 results.emplace_back( funcEnv, funcNeed, funcHave, funcOpen );
697 std::size_t genStart = 0;
698
699 for ( const ast::DeclWithType * param : funcType->params ) {
700 auto obj = strict_dynamic_cast< const ast::ObjectDecl * >( param );
701 // Try adding the arguments corresponding to the current parameter to the existing
702 // matches
703 if ( ! instantiateArgument(
704 obj->type, obj->init, args, results, genStart, symtab ) ) return;
705 }
706
707 if ( funcType->isVarArgs ) {
708 // append any unused arguments to vararg pack
709 std::size_t genEnd;
710 do {
711 genEnd = results.size();
712
713 // iterate results
714 for ( std::size_t i = genStart; i < genEnd; ++i ) {
715 unsigned nextArg = results[i].nextArg;
716
717 // use remainder of exploded tuple if present
718 if ( results[i].hasExpl() ) {
719 const ExplodedArg & expl = results[i].getExpl( args );
720
721 unsigned nextExpl = results[i].nextExpl + 1;
722 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
723
724 results.emplace_back(
725 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
726 copy( results[i].need ), copy( results[i].have ),
727 copy( results[i].open ), nextArg, 0, Cost::zero, nextExpl,
728 results[i].explAlt );
729
730 continue;
731 }
732
733 // finish result when out of arguments
734 if ( nextArg >= args.size() ) {
735 validateFunctionCandidate( func, results[i], results, out );
736
737 continue;
738 }
739
740 // add each possible next argument
741 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
742 const ExplodedArg & expl = args[nextArg][j];
743
744 // fresh copies of parent parameters for this iteration
745 ast::TypeEnvironment env = results[i].env;
746 ast::OpenVarSet open = results[i].open;
747
748 env.addActual( expl.env, open );
749
750 // skip empty tuple arguments by (nearly) cloning parent into next gen
751 if ( expl.exprs.empty() ) {
752 results.emplace_back(
753 results[i], move( env ), copy( results[i].need ),
754 copy( results[i].have ), move( open ), nextArg + 1,
755 expl.cost );
756
757 continue;
758 }
759
760 // add new result
761 results.emplace_back(
762 i, expl.exprs.front(), move( env ), copy( results[i].need ),
763 copy( results[i].have ), move( open ), nextArg + 1, 0, expl.cost,
764 expl.exprs.size() == 1 ? 0 : 1, j );
765 }
766 }
767
768 genStart = genEnd;
769 } while( genEnd != results.size() );
770 } else {
771 // filter out the results that don't use all the arguments
772 for ( std::size_t i = genStart; i < results.size(); ++i ) {
773 ArgPack & result = results[i];
774 if ( ! result.hasExpl() && result.nextArg >= args.size() ) {
775 validateFunctionCandidate( func, result, results, out );
776 }
777 }
778 }
[4b7cce6]779 }
780
[432ce7a]781 /// Adds implicit struct-conversions to the alternative list
782 void addAnonConversions( const CandidateRef & cand ) {
[c8e4d2f8]783 // adds anonymous member interpretations whenever an aggregate value type is seen.
784 // it's okay for the aggregate expression to have reference type -- cast it to the
785 // base type to treat the aggregate as the referenced value
786 ast::ptr< ast::Expr > aggrExpr( cand->expr );
787 ast::ptr< ast::Type > & aggrType = aggrExpr.get_and_mutate()->result;
788 cand->env.apply( aggrType );
789
790 if ( aggrType.as< ast::ReferenceType >() ) {
[b8524ca]791 aggrExpr = new ast::CastExpr{ aggrExpr, aggrType->stripReferences() };
[c8e4d2f8]792 }
793
794 if ( auto structInst = aggrExpr->result.as< ast::StructInstType >() ) {
[898ae07]795 addAggMembers( structInst, aggrExpr, *cand, Cost::safe, "" );
[c8e4d2f8]796 } else if ( auto unionInst = aggrExpr->result.as< ast::UnionInstType >() ) {
[898ae07]797 addAggMembers( unionInst, aggrExpr, *cand, Cost::safe, "" );
[c8e4d2f8]798 }
799 }
800
801 /// Adds aggregate member interpretations
802 void addAggMembers(
803 const ast::ReferenceToType * aggrInst, const ast::Expr * expr,
[898ae07]804 const Candidate & cand, const Cost & addedCost, const std::string & name
[c8e4d2f8]805 ) {
806 for ( const ast::Decl * decl : aggrInst->lookup( name ) ) {
807 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( decl );
808 CandidateRef newCand = std::make_shared<Candidate>(
[898ae07]809 cand, new ast::MemberExpr{ expr->location, dwt, expr }, addedCost );
[c8e4d2f8]810 // add anonymous member interpretations whenever an aggregate value type is seen
811 // as a member expression
812 addAnonConversions( newCand );
813 candidates.emplace_back( move( newCand ) );
814 }
[432ce7a]815 }
816
[898ae07]817 /// Adds tuple member interpretations
818 void addTupleMembers(
819 const ast::TupleType * tupleType, const ast::Expr * expr, const Candidate & cand,
820 const Cost & addedCost, const ast::Expr * member
821 ) {
822 if ( auto constantExpr = dynamic_cast< const ast::ConstantExpr * >( member ) ) {
823 // get the value of the constant expression as an int, must be between 0 and the
824 // length of the tuple to have meaning
825 long long val = constantExpr->intValue();
826 if ( val >= 0 && (unsigned long long)val < tupleType->size() ) {
827 addCandidate(
828 cand, new ast::TupleIndexExpr{ expr->location, expr, (unsigned)val },
829 addedCost );
830 }
831 }
832 }
833
[432ce7a]834 void postvisit( const ast::UntypedExpr * untypedExpr ) {
835 CandidateFinder funcFinder{ symtab, tenv };
836 funcFinder.find( untypedExpr->func, ResolvMode::withAdjustment() );
837 // short-circuit if no candidates
838 if ( funcFinder.candidates.empty() ) return;
839
840 std::vector< CandidateFinder > argCandidates =
841 selfFinder.findSubExprs( untypedExpr->args );
842
843 // take care of possible tuple assignments
844 // if not tuple assignment, handled as normal function call
845 Tuples::handleTupleAssignment( selfFinder, untypedExpr, argCandidates );
846
847 // find function operators
848 ast::ptr< ast::Expr > opExpr = new ast::NameExpr{ untypedExpr->location, "?()" };
849 CandidateFinder opFinder{ symtab, tenv };
850 // okay if there aren't any function operations
851 opFinder.find( opExpr, ResolvMode::withoutFailFast() );
852 PRINT(
853 std::cerr << "known function ops:" << std::endl;
854 print( std::cerr, opFinder.candidates, 1 );
855 )
856
857 // pre-explode arguments
858 ExplodedArgs_new argExpansions;
859 for ( const CandidateFinder & args : argCandidates ) {
860 argExpansions.emplace_back();
861 auto & argE = argExpansions.back();
862 for ( const CandidateRef & arg : args ) { argE.emplace_back( *arg, symtab ); }
863 }
864
865 // Find function matches
866 CandidateList found;
867 SemanticErrorException errors;
868 for ( CandidateRef & func : funcFinder ) {
869 try {
870 PRINT(
871 std::cerr << "working on alternative:" << std::endl;
872 print( std::cerr, *func, 2 );
873 )
874
875 // check if the type is a pointer to function
876 const ast::Type * funcResult = func->expr->result->stripReferences();
877 if ( auto pointer = dynamic_cast< const ast::PointerType * >( funcResult ) ) {
878 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
879 CandidateRef newFunc{ new Candidate{ *func } };
880 newFunc->expr =
881 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
882 makeFunctionCandidates( newFunc, function, argExpansions, found );
883 }
884 } else if (
885 auto inst = dynamic_cast< const ast::TypeInstType * >( funcResult )
886 ) {
887 if ( const ast::EqvClass * clz = func->env.lookup( inst->name ) ) {
888 if ( auto function = clz->bound.as< ast::FunctionType >() ) {
889 CandidateRef newFunc{ new Candidate{ *func } };
890 newFunc->expr =
891 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
892 makeFunctionCandidates( newFunc, function, argExpansions, found );
893 }
894 }
895 }
896 } catch ( SemanticErrorException & e ) { errors.append( e ); }
897 }
898
899 // Find matches on function operators `?()`
900 if ( ! opFinder.candidates.empty() ) {
901 // add exploded function alternatives to front of argument list
902 std::vector< ExplodedArg > funcE;
903 funcE.reserve( funcFinder.candidates.size() );
904 for ( const CandidateRef & func : funcFinder ) {
905 funcE.emplace_back( *func, symtab );
906 }
[9d5089e]907 argExpansions.emplace_front( move( funcE ) );
[432ce7a]908
909 for ( const CandidateRef & op : opFinder ) {
910 try {
911 // check if type is pointer-to-function
912 const ast::Type * opResult = op->expr->result->stripReferences();
913 if ( auto pointer = dynamic_cast< const ast::PointerType * >( opResult ) ) {
914 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
915 CandidateRef newOp{ new Candidate{ *op} };
916 newOp->expr =
917 referenceToRvalueConversion( newOp->expr, newOp->cost );
918 makeFunctionCandidates( newOp, function, argExpansions, found );
919 }
920 }
921 } catch ( SemanticErrorException & e ) { errors.append( e ); }
922 }
923 }
924
925 // Implement SFINAE; resolution errors are only errors if there aren't any non-error
926 // candidates
927 if ( found.empty() && ! errors.isEmpty() ) { throw errors; }
928
929 // Compute conversion costs
930 for ( CandidateRef & withFunc : found ) {
931 Cost cvtCost = computeApplicationConversionCost( withFunc, symtab );
932
933 PRINT(
934 auto appExpr = withFunc->expr.strict_as< ast::ApplicationExpr >();
935 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
936 auto function = pointer->base.strict_as< ast::FunctionType >();
937
938 std::cerr << "Case +++++++++++++ " << appExpr->func << std::endl;
939 std::cerr << "parameters are:" << std::endl;
940 ast::printAll( std::cerr, function->params, 2 );
941 std::cerr << "arguments are:" << std::endl;
942 ast::printAll( std::cerr, appExpr->args, 2 );
943 std::cerr << "bindings are:" << std::endl;
944 ast::print( std::cerr, withFunc->env, 2 );
945 std::cerr << "cost is: " << withFunc->cost << std::endl;
946 std::cerr << "cost of conversion is:" << cvtCost << std::endl;
947 )
948
949 if ( cvtCost != Cost::infinity ) {
950 withFunc->cvtCost = cvtCost;
[9d5089e]951 candidates.emplace_back( move( withFunc ) );
[432ce7a]952 }
953 }
[9d5089e]954 found = move( candidates );
[432ce7a]955
956 // use a new list so that candidates are not examined by addAnonConversions twice
957 CandidateList winners = findMinCost( found );
958 promoteCvtCost( winners );
959
960 // function may return a struct/union value, in which case we need to add candidates
961 // for implicit conversions to each of the anonymous members, which must happen after
962 // `findMinCost`, since anon conversions are never the cheapest
963 for ( const CandidateRef & c : winners ) {
964 addAnonConversions( c );
965 }
966 spliceBegin( candidates, winners );
967
968 if ( candidates.empty() && targetType && ! targetType->isVoid() ) {
969 // If resolution is unsuccessful with a target type, try again without, since it
970 // will sometimes succeed when it wouldn't with a target type binding.
971 // For example:
972 // forall( otype T ) T & ?[]( T *, ptrdiff_t );
973 // const char * x = "hello world";
974 // unsigned char ch = x[0];
975 // Fails with simple return type binding (xxx -- check this!) as follows:
976 // * T is bound to unsigned char
977 // * (x: const char *) is unified with unsigned char *, which fails
978 // xxx -- fix this better
979 targetType = nullptr;
980 postvisit( untypedExpr );
981 }
982 }
983
[4b7cce6]984 /// true if expression is an lvalue
985 static bool isLvalue( const ast::Expr * x ) {
986 return x->result && ( x->result->is_lvalue() || x->result.as< ast::ReferenceType >() );
987 }
988
989 void postvisit( const ast::AddressExpr * addressExpr ) {
990 CandidateFinder finder{ symtab, tenv };
991 finder.find( addressExpr->arg );
992 for ( CandidateRef & r : finder.candidates ) {
993 if ( ! isLvalue( r->expr ) ) continue;
994 addCandidate( *r, new ast::AddressExpr{ addressExpr->location, r->expr } );
995 }
996 }
997
998 void postvisit( const ast::LabelAddressExpr * labelExpr ) {
999 addCandidate( labelExpr, tenv );
1000 }
1001
1002 void postvisit( const ast::CastExpr * castExpr ) {
[c8e4d2f8]1003 ast::ptr< ast::Type > toType = castExpr->result;
1004 assert( toType );
1005 toType = resolveTypeof( toType, symtab );
[18e683b]1006 toType = SymTab::validateType( castExpr->location, toType, symtab );
[c8e4d2f8]1007 toType = adjustExprType( toType, tenv, symtab );
1008
1009 CandidateFinder finder{ symtab, tenv, toType };
1010 finder.find( castExpr->arg, ResolvMode::withAdjustment() );
1011
1012 CandidateList matches;
1013 for ( CandidateRef & cand : finder.candidates ) {
1014 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1015 ast::OpenVarSet open( cand->open );
1016
1017 cand->env.extractOpenVars( open );
1018
1019 // It is possible that a cast can throw away some values in a multiply-valued
1020 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of the
1021 // subexpression results that are cast directly. The candidate is invalid if it
1022 // has fewer results than there are types to cast to.
1023 int discardedValues = cand->expr->result->size() - toType->size();
1024 if ( discardedValues < 0 ) continue;
1025
1026 // unification run for side-effects
1027 unify( toType, cand->expr->result, cand->env, need, have, open, symtab );
1028 Cost thisCost = castCost( cand->expr->result, toType, 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
[898ae07]1048 // select first on argument cost, then conversion cost
1049 CandidateList minArgCost = findMinCost( matches );
1050 promoteCvtCost( minArgCost );
1051 candidates = findMinCost( minArgCost );
[4b7cce6]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(
[c8e4d2f8]1061 *r,
1062 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
[4b7cce6]1063 }
1064 }
1065
1066 void postvisit( const ast::UntypedMemberExpr * memberExpr ) {
[898ae07]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 }
[4b7cce6]1086 }
1087
1088 void postvisit( const ast::MemberExpr * memberExpr ) {
1089 addCandidate( memberExpr, tenv );
1090 }
1091
[898ae07]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 }
[4b7cce6]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 ) {
[898ae07]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 }
[4b7cce6]1153 }
1154
1155 void postvisit( const ast::AlignofExpr * alignofExpr ) {
[898ae07]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 }
[4b7cce6]1178 }
1179
1180 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
[898ae07]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 }
[4b7cce6]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 },
[9d5089e]1223 move( env ), move( open ), move( need ), r1->cost + r2->cost );
[4b7cce6]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 ) {
[898ae07]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 );
[4b7cce6]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 ) {
[898ae07]1338 // generate new expression
[4b7cce6]1339 ast::RangeExpr * newExpr =
1340 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1341 newExpr->result = common ? common : r1->expr->result;
[898ae07]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 );
[4b7cce6]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(
[9d5089e]1373 new ast::TupleExpr{ tupleExpr->location, move( exprs ) },
1374 move( env ), move( open ), move( need ), sumCost( subs ) );
[4b7cce6]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 ) {
[17a0ede2]1400 addCandidate( resolveStmtExpr( stmtExpr, symtab ), tenv );
[4b7cce6]1401 }
1402
1403 void postvisit( const ast::UntypedInitExpr * initExpr ) {
[17a0ede2]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 );
[18e683b]1413 toType = SymTab::validateType( initExpr->location, toType, symtab );
[17a0ede2]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, symtab, env );
1439
1440 if ( thisCost != Cost::infinity ) {
1441 // count one safe conversion for each value that is thrown away
1442 thisCost.incSafe( discardedValues );
1443 CandidateRef newCand = std::make_shared<Candidate>(
1444 new ast::InitExpr{
1445 initExpr->location, restructureCast( cand->expr, toType ),
1446 initAlt.designation },
1447 copy( cand->env ), move( open ), move( need ), cand->cost, thisCost );
1448 inferParameters( newCand, matches );
1449 }
1450 }
1451 }
1452
1453 // select first on argument cost, then conversion cost
1454 CandidateList minArgCost = findMinCost( matches );
1455 promoteCvtCost( minArgCost );
1456 candidates = findMinCost( minArgCost );
[4b7cce6]1457 }
1458
1459 void postvisit( const ast::InitExpr * ) {
1460 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
1461 }
1462
1463 void postvisit( const ast::DeletedExpr * ) {
1464 assertf( false, "CandidateFinder should never see a DeletedExpr." );
1465 }
1466
1467 void postvisit( const ast::GenericExpr * ) {
1468 assertf( false, "_Generic is not yet supported." );
1469 }
[396037d]1470 };
1471
1472 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1473 /// return type. Skips ambiguous candidates.
1474 CandidateList pruneCandidates( CandidateList & candidates ) {
[d57e349]1475 struct PruneStruct {
1476 CandidateRef candidate;
1477 bool ambiguous;
1478
1479 PruneStruct() = default;
1480 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1481 };
1482
1483 // find lowest-cost candidate for each type
1484 std::unordered_map< std::string, PruneStruct > selected;
1485 for ( CandidateRef & candidate : candidates ) {
1486 std::string mangleName;
1487 {
1488 ast::ptr< ast::Type > newType = candidate->expr->result;
1489 candidate->env.apply( newType );
1490 mangleName = Mangle::mangle( newType );
1491 }
1492
1493 auto found = selected.find( mangleName );
1494 if ( found != selected.end() ) {
1495 if ( candidate->cost < found->second.candidate->cost ) {
1496 PRINT(
1497 std::cerr << "cost " << candidate->cost << " beats "
1498 << found->second.candidate->cost << std::endl;
1499 )
1500
1501 found->second = PruneStruct{ candidate };
1502 } else if ( candidate->cost == found->second.candidate->cost ) {
1503 // if one of the candidates contains a deleted identifier, can pick the other,
1504 // since deleted expressions should not be ambiguous if there is another option
1505 // that is at least as good
1506 if ( findDeletedExpr( candidate->expr ) ) {
1507 // do nothing
1508 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1509 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1510 PRINT( std::cerr << "current is deleted" << std::endl; )
1511 found->second = PruneStruct{ candidate };
1512 } else {
1513 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1514 found->second.ambiguous = true;
1515 }
1516 } else {
1517 PRINT(
1518 std::cerr << "cost " << candidate->cost << " loses to "
1519 << found->second.candidate->cost << std::endl;
1520 )
1521 }
1522 } else {
1523 selected.emplace_hint( found, mangleName, candidate );
1524 }
1525 }
1526
1527 // report unambiguous min-cost candidates
1528 CandidateList out;
1529 for ( auto & target : selected ) {
1530 if ( target.second.ambiguous ) continue;
1531
1532 CandidateRef cand = target.second.candidate;
1533
1534 ast::ptr< ast::Type > newResult = cand->expr->result;
1535 cand->env.applyFree( newResult );
1536 cand->expr = ast::mutate_field(
[9d5089e]1537 cand->expr.get(), &ast::Expr::result, move( newResult ) );
[d57e349]1538
1539 out.emplace_back( cand );
1540 }
1541 return out;
1542 }
1543
[396037d]1544} // anonymous namespace
1545
[99d4584]1546void CandidateFinder::find( const ast::Expr * expr, ResolvMode mode ) {
[396037d]1547 // Find alternatives for expression
1548 ast::Pass<Finder> finder{ *this };
1549 expr->accept( finder );
1550
1551 if ( mode.failFast && candidates.empty() ) {
1552 SemanticError( expr, "No reasonable alternatives for expression " );
1553 }
1554
1555 if ( mode.satisfyAssns || mode.prune ) {
1556 // trim candidates to just those where the assertions are satisfiable
1557 // - necessary pre-requisite to pruning
1558 CandidateList satisfied;
1559 std::vector< std::string > errors;
[b69233ac]1560 for ( CandidateRef & candidate : candidates ) {
[9ea38de]1561 satisfyAssertions( candidate, localSyms, satisfied, errors );
[396037d]1562 }
1563
1564 // fail early if none such
1565 if ( mode.failFast && satisfied.empty() ) {
1566 std::ostringstream stream;
1567 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1568 for ( const auto& err : errors ) {
1569 stream << err;
1570 }
1571 SemanticError( expr->location, stream.str() );
1572 }
1573
1574 // reset candidates
[9d5089e]1575 candidates = move( satisfied );
[396037d]1576 }
1577
1578 if ( mode.prune ) {
1579 // trim candidates to single best one
1580 PRINT(
1581 std::cerr << "alternatives before prune:" << std::endl;
1582 print( std::cerr, candidates );
1583 )
1584
1585 CandidateList pruned = pruneCandidates( candidates );
[d57e349]1586
[396037d]1587 if ( mode.failFast && pruned.empty() ) {
1588 std::ostringstream stream;
[d57e349]1589 CandidateList winners = findMinCost( candidates );
1590 stream << "Cannot choose between " << winners.size() << " alternatives for "
1591 "expression\n";
1592 ast::print( stream, expr );
1593 stream << " Alternatives are:\n";
1594 print( stream, winners, 1 );
1595 SemanticError( expr->location, stream.str() );
[396037d]1596 }
[d57e349]1597
1598 auto oldsize = candidates.size();
[9d5089e]1599 candidates = move( pruned );
[d57e349]1600
1601 PRINT(
1602 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
1603 )
1604 PRINT(
1605 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
1606 << std::endl;
1607 )
[396037d]1608 }
1609
[d57e349]1610 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
1611 // adjusted
1612 if ( mode.adjust ) {
1613 for ( CandidateRef & r : candidates ) {
1614 r->expr = ast::mutate_field(
1615 r->expr.get(), &ast::Expr::result,
[9ea38de]1616 adjustExprType( r->expr->result, r->env, localSyms ) );
[d57e349]1617 }
1618 }
1619
1620 // Central location to handle gcc extension keyword, etc. for all expressions
1621 for ( CandidateRef & r : candidates ) {
1622 if ( r->expr->extension != expr->extension ) {
1623 r->expr.get_and_mutate()->extension = expr->extension;
1624 }
1625 }
[99d4584]1626}
1627
[2773ab8]1628std::vector< CandidateFinder > CandidateFinder::findSubExprs(
1629 const std::vector< ast::ptr< ast::Expr > > & xs
1630) {
1631 std::vector< CandidateFinder > out;
1632
[396037d]1633 for ( const auto & x : xs ) {
[9ea38de]1634 out.emplace_back( localSyms, env );
[396037d]1635 out.back().find( x, ResolvMode::withAdjustment() );
1636
1637 PRINT(
1638 std::cerr << "findSubExprs" << std::endl;
1639 print( std::cerr, out.back().candidates );
1640 )
1641 }
[2773ab8]1642
1643 return out;
1644}
1645
[99d4584]1646} // namespace ResolvExpr
1647
1648// Local Variables: //
1649// tab-width: 4 //
1650// mode: c++ //
1651// compile-command: "make install" //
1652// End: //
Note: See TracBrowser for help on using the repository browser.