source: src/ResolvExpr/CandidateFinder.cpp@ aca144e

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 aca144e was b8524ca, checked in by Aaron Moss <a3moss@…>, 6 years ago

new AST porting

  • mostly InitTweak autogeneration
  • added some convenience methods
    • nullptr assignment for ast::ptr
    • convenience wrapper ctors for AddressExpr, CastExpr that draw location from first arg
  • 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"
[d57e349]41#include "SymTab/Mangler.h"
[c8e4d2f8]42#include "SymTab/Validate.h" // for validateType
[432ce7a]43#include "Tuples/Tuples.h" // for handleTupleAssignment
[396037d]44
45#define PRINT( text ) if ( resolvep ) { text }
[99d4584]46
47namespace ResolvExpr {
48
[9d5089e]49using std::move;
50
51/// partner to move that copies any copyable type
52template<typename T>
53T copy( const T & x ) { return x; }
54
55const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
56 if ( expr->result.as< ast::ReferenceType >() ) {
57 // cast away reference from expr
58 cost.incReference();
[b8524ca]59 return new ast::CastExpr{ expr, expr->result->stripReferences() };
[9d5089e]60 }
61
62 return expr;
63}
64
65/// Unique identifier for matching expression resolutions to their requesting expression
66UniqueId globalResnSlot = 0;
[396037d]67
[b69233ac]68Cost computeConversionCost(
69 const ast::Type * argType, const ast::Type * paramType, const ast::SymbolTable & symtab,
70 const ast::TypeEnvironment & env
71) {
72 PRINT(
73 std::cerr << std::endl << "converting ";
74 ast::print( std::cerr, argType, 2 );
75 std::cerr << std::endl << " to ";
76 ast::print( std::cerr, paramType, 2 );
77 std::cerr << std::endl << "environment is: ";
78 ast::print( std::cerr, env, 2 );
79 std::cerr << std::endl;
80 )
81 Cost convCost = conversionCost( argType, paramType, symtab, env );
82 PRINT(
83 std::cerr << std::endl << "cost is " << convCost << std::endl;
84 )
85 if ( convCost == Cost::infinity ) return convCost;
86 convCost.incPoly( polyCost( paramType, symtab, env ) + polyCost( argType, symtab, env ) );
87 PRINT(
88 std::cerr << "cost with polycost is " << convCost << std::endl;
89 )
90 return convCost;
91}
92
[9d5089e]93namespace {
[432ce7a]94 /// First index is which argument, second is which alternative, third is which exploded element
95 using ExplodedArgs_new = std::deque< std::vector< ExplodedArg > >;
96
97 /// Returns a list of alternatives with the minimum cost in the given list
98 CandidateList findMinCost( const CandidateList & candidates ) {
99 CandidateList out;
100 Cost minCost = Cost::infinity;
101 for ( const CandidateRef & r : candidates ) {
102 if ( r->cost < minCost ) {
103 minCost = r->cost;
104 out.clear();
105 out.emplace_back( r );
106 } else if ( r->cost == minCost ) {
107 out.emplace_back( r );
108 }
109 }
110 return out;
111 }
112
[9d5089e]113 /// Computes conversion cost for a given expression to a given type
114 const ast::Expr * computeExpressionConversionCost(
115 const ast::Expr * arg, const ast::Type * paramType, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env, Cost & outCost
116 ) {
117 Cost convCost = computeConversionCost( arg->result, paramType, symtab, env );
118 outCost += convCost;
119
120 // If there is a non-zero conversion cost, ignoring poly cost, then the expression requires
121 // conversion. Ignore poly cost for now, since this requires resolution of the cast to
122 // infer parameters and this does not currently work for the reason stated below
123 Cost tmpCost = convCost;
124 tmpCost.incPoly( -tmpCost.get_polyCost() );
125 if ( tmpCost != Cost::zero ) {
126 ast::ptr< ast::Type > newType = paramType;
127 env.apply( newType );
[b8524ca]128 return new ast::CastExpr{ arg, newType };
[9d5089e]129
130 // xxx - *should* be able to resolve this cast, but at the moment pointers are not
131 // castable to zero_t, but are implicitly convertible. This is clearly inconsistent,
132 // once this is fixed it should be possible to resolve the cast.
133 // xxx - this isn't working, it appears because type1 (parameter) is seen as widenable,
134 // but it shouldn't be because this makes the conversion from DT* to DT* since
135 // commontype(zero_t, DT*) is DT*, rather than nothing
136
137 // CandidateFinder finder{ symtab, env };
138 // finder.find( arg, ResolvMode::withAdjustment() );
139 // assertf( finder.candidates.size() > 0,
140 // "Somehow castable expression failed to find alternatives." );
141 // assertf( finder.candidates.size() == 1,
142 // "Somehow got multiple alternatives for known cast expression." );
143 // return finder.candidates.front()->expr;
144 }
145
146 return arg;
147 }
148
[432ce7a]149 /// Computes conversion cost for a given candidate
150 Cost computeApplicationConversionCost(
[9d5089e]151 CandidateRef cand, const ast::SymbolTable & symtab
[432ce7a]152 ) {
[9d5089e]153 auto appExpr = cand->expr.strict_as< ast::ApplicationExpr >();
154 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
155 auto function = pointer->base.strict_as< ast::FunctionType >();
156
157 Cost convCost = Cost::zero;
158 const auto & params = function->params;
159 auto param = params.begin();
160 auto & args = appExpr->args;
161
162 for ( unsigned i = 0; i < args.size(); ++i ) {
163 const ast::Type * argType = args[i]->result;
164 PRINT(
165 std::cerr << "arg expression:" << std::endl;
166 ast::print( std::cerr, args[i], 2 );
167 std::cerr << "--- results are" << std::endl;
168 ast::print( std::cerr, argType, 2 );
169 )
170
171 if ( param == params.end() ) {
172 if ( function->isVarArgs ) {
173 convCost.incUnsafe();
174 PRINT( std::cerr << "end of params with varargs function: inc unsafe: "
175 << convCost << std::endl; ; )
176 // convert reference-typed expressions into value-typed expressions
177 cand->expr = ast::mutate_field_index(
178 appExpr, &ast::ApplicationExpr::args, i,
179 referenceToRvalueConversion( args[i], convCost ) );
180 continue;
181 } else return Cost::infinity;
182 }
183
184 if ( auto def = args[i].as< ast::DefaultArgExpr >() ) {
185 // Default arguments should be free - don't include conversion cost.
186 // Unwrap them here because they are not relevant to the rest of the system
187 cand->expr = ast::mutate_field_index(
188 appExpr, &ast::ApplicationExpr::args, i, def->expr );
189 ++param;
190 continue;
191 }
192
193 // mark conversion cost and also specialization cost of param type
194 const ast::Type * paramType = (*param)->get_type();
195 cand->expr = ast::mutate_field_index(
196 appExpr, &ast::ApplicationExpr::args, i,
197 computeExpressionConversionCost(
198 args[i], paramType, symtab, cand->env, convCost ) );
199 convCost.decSpec( specCost( paramType ) );
200 ++param; // can't be in for-loop update because of the continue
201 }
202
203 if ( param != params.end() ) return Cost::infinity;
204
205 // specialization cost of return types can't be accounted for directly, it disables
206 // otherwise-identical calls, like this example based on auto-newline in the I/O lib:
207 //
208 // forall(otype OS) {
209 // void ?|?(OS&, int); // with newline
210 // OS& ?|?(OS&, int); // no newline, always chosen due to more specialization
211 // }
212
213 // mark type variable and specialization cost of forall clause
214 convCost.incVar( function->forall.size() );
215 for ( const ast::TypeDecl * td : function->forall ) {
216 convCost.decSpec( td->assertions.size() );
217 }
218
219 return convCost;
220 }
221
222 void makeUnifiableVars(
223 const ast::ParameterizedType * type, ast::OpenVarSet & unifiableVars,
224 ast::AssertionSet & need
225 ) {
226 for ( const ast::TypeDecl * tyvar : type->forall ) {
227 unifiableVars[ tyvar->name ] = ast::TypeDecl::Data{ tyvar };
228 for ( const ast::DeclWithType * assn : tyvar->assertions ) {
229 need[ assn ].isUsed = true;
230 }
231 }
232 }
233
234 /// Gets a default value from an initializer, nullptr if not present
235 const ast::ConstantExpr * getDefaultValue( const ast::Init * init ) {
236 if ( auto si = dynamic_cast< const ast::SingleInit * >( init ) ) {
237 if ( auto ce = si->value.as< ast::CastExpr >() ) {
238 return ce->arg.as< ast::ConstantExpr >();
239 } else {
240 return si->value.as< ast::ConstantExpr >();
241 }
242 }
243 return nullptr;
244 }
245
246 /// State to iteratively build a match of parameter expressions to arguments
247 struct ArgPack {
248 std::size_t parent; ///< Index of parent pack
249 ast::ptr< ast::Expr > expr; ///< The argument stored here
250 Cost cost; ///< The cost of this argument
251 ast::TypeEnvironment env; ///< Environment for this pack
252 ast::AssertionSet need; ///< Assertions outstanding for this pack
253 ast::AssertionSet have; ///< Assertions found for this pack
254 ast::OpenVarSet open; ///< Open variables for this pack
255 unsigned nextArg; ///< Index of next argument in arguments list
256 unsigned tupleStart; ///< Number of tuples that start at this index
257 unsigned nextExpl; ///< Index of next exploded element
258 unsigned explAlt; ///< Index of alternative for nextExpl > 0
259
260 ArgPack()
261 : parent( 0 ), expr(), cost( Cost::zero ), env(), need(), have(), open(), nextArg( 0 ),
262 tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
263
264 ArgPack(
265 const ast::TypeEnvironment & env, const ast::AssertionSet & need,
266 const ast::AssertionSet & have, const ast::OpenVarSet & open )
267 : parent( 0 ), expr(), cost( Cost::zero ), env( env ), need( need ), have( have ),
268 open( open ), nextArg( 0 ), tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
269
270 ArgPack(
271 std::size_t parent, const ast::Expr * expr, ast::TypeEnvironment && env,
272 ast::AssertionSet && need, ast::AssertionSet && have, ast::OpenVarSet && open,
273 unsigned nextArg, unsigned tupleStart = 0, Cost cost = Cost::zero,
274 unsigned nextExpl = 0, unsigned explAlt = 0 )
275 : parent(parent), expr( expr ), cost( cost ), env( move( env ) ), need( move( need ) ),
276 have( move( have ) ), open( move( open ) ), nextArg( nextArg ), tupleStart( tupleStart ),
277 nextExpl( nextExpl ), explAlt( explAlt ) {}
278
279 ArgPack(
280 const ArgPack & o, ast::TypeEnvironment && env, ast::AssertionSet && need,
281 ast::AssertionSet && have, ast::OpenVarSet && open, unsigned nextArg, Cost added )
282 : parent( o.parent ), expr( o.expr ), cost( o.cost + added ), env( move( env ) ),
283 need( move( need ) ), have( move( have ) ), open( move( open ) ), nextArg( nextArg ),
284 tupleStart( o.tupleStart ), nextExpl( 0 ), explAlt( 0 ) {}
285
286 /// true if this pack is in the middle of an exploded argument
287 bool hasExpl() const { return nextExpl > 0; }
288
289 /// Gets the list of exploded candidates for this pack
290 const ExplodedArg & getExpl( const ExplodedArgs_new & args ) const {
291 return args[ nextArg-1 ][ explAlt ];
292 }
293
294 /// Ends a tuple expression, consolidating the appropriate args
295 void endTuple( const std::vector< ArgPack > & packs ) {
296 // add all expressions in tuple to list, summing cost
297 std::deque< const ast::Expr * > exprs;
298 const ArgPack * pack = this;
299 if ( expr ) { exprs.emplace_front( expr ); }
300 while ( pack->tupleStart == 0 ) {
301 pack = &packs[pack->parent];
302 exprs.emplace_front( pack->expr );
303 cost += pack->cost;
304 }
305 // reset pack to appropriate tuple
306 std::vector< ast::ptr< ast::Expr > > exprv( exprs.begin(), exprs.end() );
307 expr = new ast::TupleExpr{ expr->location, move( exprv ) };
308 tupleStart = pack->tupleStart - 1;
309 parent = pack->parent;
310 }
311 };
312
313 /// Instantiates an argument to match a parameter, returns false if no matching results left
314 bool instantiateArgument(
315 const ast::Type * paramType, const ast::Init * init, const ExplodedArgs_new & args,
316 std::vector< ArgPack > & results, std::size_t & genStart, const ast::SymbolTable & symtab,
317 unsigned nTuples = 0
318 ) {
319 if ( auto tupleType = dynamic_cast< const ast::TupleType * >( paramType ) ) {
320 // paramType is a TupleType -- group args into a TupleExpr
321 ++nTuples;
322 for ( const ast::Type * type : *tupleType ) {
323 // xxx - dropping initializer changes behaviour from previous, but seems correct
324 // ^^^ need to handle the case where a tuple has a default argument
325 if ( ! instantiateArgument(
326 type, nullptr, args, results, genStart, symtab, nTuples ) ) return false;
327 nTuples = 0;
328 }
329 // re-constitute tuples for final generation
330 for ( auto i = genStart; i < results.size(); ++i ) {
331 results[i].endTuple( results );
332 }
333 return true;
334 } else if ( const ast::TypeInstType * ttype = Tuples::isTtype( paramType ) ) {
335 // paramType is a ttype, consumes all remaining arguments
336
337 // completed tuples; will be spliced to end of results to finish
338 std::vector< ArgPack > finalResults{};
339
340 // iterate until all results completed
341 std::size_t genEnd;
342 ++nTuples;
343 do {
344 genEnd = results.size();
345
346 // add another argument to results
347 for ( std::size_t i = genStart; i < genEnd; ++i ) {
348 unsigned nextArg = results[i].nextArg;
349
350 // use next element of exploded tuple if present
351 if ( results[i].hasExpl() ) {
352 const ExplodedArg & expl = results[i].getExpl( args );
353
354 unsigned nextExpl = results[i].nextExpl + 1;
355 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
356
357 results.emplace_back(
358 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
359 copy( results[i].need ), copy( results[i].have ),
360 copy( results[i].open ), nextArg, nTuples, Cost::zero, nextExpl,
361 results[i].explAlt );
362
363 continue;
364 }
365
366 // finish result when out of arguments
367 if ( nextArg >= args.size() ) {
368 ArgPack newResult{
369 results[i].env, results[i].need, results[i].have, results[i].open };
370 newResult.nextArg = nextArg;
371 const ast::Type * argType = nullptr;
372
373 if ( nTuples > 0 || ! results[i].expr ) {
374 // first iteration or no expression to clone,
375 // push empty tuple expression
376 newResult.parent = i;
377 std::vector< ast::ptr< ast::Expr > > emptyList;
378 newResult.expr =
379 new ast::TupleExpr{ CodeLocation{}, move( emptyList ) };
380 argType = newResult.expr->result;
381 } else {
382 // clone result to collect tuple
383 newResult.parent = results[i].parent;
384 newResult.cost = results[i].cost;
385 newResult.tupleStart = results[i].tupleStart;
386 newResult.expr = results[i].expr;
387 argType = newResult.expr->result;
388
389 if ( results[i].tupleStart > 0 && Tuples::isTtype( argType ) ) {
390 // the case where a ttype value is passed directly is special,
391 // e.g. for argument forwarding purposes
392 // xxx - what if passing multiple arguments, last of which is
393 // ttype?
394 // xxx - what would happen if unify was changed so that unifying
395 // tuple
396 // types flattened both before unifying lists? then pass in
397 // TupleType (ttype) below.
398 --newResult.tupleStart;
399 } else {
400 // collapse leftover arguments into tuple
401 newResult.endTuple( results );
402 argType = newResult.expr->result;
403 }
404 }
405
406 // check unification for ttype before adding to final
407 if (
408 unify(
409 ttype, argType, newResult.env, newResult.need, newResult.have,
410 newResult.open, symtab )
411 ) {
412 finalResults.emplace_back( move( newResult ) );
413 }
414
415 continue;
416 }
417
418 // add each possible next argument
419 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
420 const ExplodedArg & expl = args[nextArg][j];
421
422 // fresh copies of parent parameters for this iteration
423 ast::TypeEnvironment env = results[i].env;
424 ast::OpenVarSet open = results[i].open;
425
426 env.addActual( expl.env, open );
427
428 // skip empty tuple arguments by (nearly) cloning parent into next gen
429 if ( expl.exprs.empty() ) {
430 results.emplace_back(
431 results[i], move( env ), copy( results[i].need ),
432 copy( results[i].have ), move( open ), nextArg + 1, expl.cost );
433
434 continue;
435 }
436
437 // add new result
438 results.emplace_back(
439 i, expl.exprs.front(), move( env ), copy( results[i].need ),
440 copy( results[i].have ), move( open ), nextArg + 1, nTuples,
441 expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
442 }
443 }
444
445 // reset for next round
446 genStart = genEnd;
447 nTuples = 0;
448 } while ( genEnd != results.size() );
449
450 // splice final results onto results
451 for ( std::size_t i = 0; i < finalResults.size(); ++i ) {
452 results.emplace_back( move( finalResults[i] ) );
453 }
454 return ! finalResults.empty();
455 }
456
457 // iterate each current subresult
458 std::size_t genEnd = results.size();
459 for ( std::size_t i = genStart; i < genEnd; ++i ) {
460 unsigned nextArg = results[i].nextArg;
461
462 // use remainder of exploded tuple if present
463 if ( results[i].hasExpl() ) {
464 const ExplodedArg & expl = results[i].getExpl( args );
465 const ast::Expr * expr = expl.exprs[ results[i].nextExpl ];
466
467 ast::TypeEnvironment env = results[i].env;
468 ast::AssertionSet need = results[i].need, have = results[i].have;
469 ast::OpenVarSet open = results[i].open;
470
471 const ast::Type * argType = expr->result;
472
473 PRINT(
474 std::cerr << "param type is ";
475 ast::print( std::cerr, paramType );
476 std::cerr << std::endl << "arg type is ";
477 ast::print( std::cerr, argType );
478 std::cerr << std::endl;
479 )
480
481 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
482 unsigned nextExpl = results[i].nextExpl + 1;
483 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
484
485 results.emplace_back(
486 i, expr, move( env ), move( need ), move( have ), move( open ), nextArg,
487 nTuples, Cost::zero, nextExpl, results[i].explAlt );
488 }
489
490 continue;
491 }
492
493 // use default initializers if out of arguments
494 if ( nextArg >= args.size() ) {
495 if ( const ast::ConstantExpr * cnst = getDefaultValue( init ) ) {
496 ast::TypeEnvironment env = results[i].env;
497 ast::AssertionSet need = results[i].need, have = results[i].have;
498 ast::OpenVarSet open = results[i].open;
499
500 if ( unify( paramType, cnst->result, env, need, have, open, symtab ) ) {
501 results.emplace_back(
502 i, new ast::DefaultArgExpr{ cnst->location, cnst }, move( env ),
503 move( need ), move( have ), move( open ), nextArg, nTuples );
504 }
505 }
506
507 continue;
508 }
509
510 // Check each possible next argument
511 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
512 const ExplodedArg & expl = args[nextArg][j];
513
514 // fresh copies of parent parameters for this iteration
515 ast::TypeEnvironment env = results[i].env;
516 ast::AssertionSet need = results[i].need, have = results[i].have;
517 ast::OpenVarSet open = results[i].open;
518
519 env.addActual( expl.env, open );
520
521 // skip empty tuple arguments by (nearly) cloning parent into next gen
522 if ( expl.exprs.empty() ) {
523 results.emplace_back(
524 results[i], move( env ), move( need ), move( have ), move( open ),
525 nextArg + 1, expl.cost );
526
527 continue;
528 }
529
530 // consider only first exploded arg
531 const ast::Expr * expr = expl.exprs.front();
532 const ast::Type * argType = expr->result;
533
534 PRINT(
535 std::cerr << "param type is ";
536 ast::print( std::cerr, paramType );
537 std::cerr << std::endl << "arg type is ";
538 ast::print( std::cerr, argType );
539 std::cerr << std::endl;
540 )
541
542 // attempt to unify types
543 if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
544 // add new result
545 results.emplace_back(
546 i, expr, move( env ), move( need ), move( have ), move( open ),
547 nextArg + 1, nTuples, expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
548 }
549 }
550 }
551
552 // reset for next parameter
553 genStart = genEnd;
554
555 return genEnd != results.size();
[432ce7a]556 }
557
[c8e4d2f8]558 /// Generate a cast expression from `arg` to `toType`
[898ae07]559 const ast::Expr * restructureCast(
[17a0ede2]560 ast::ptr< ast::Expr > & arg, const ast::Type * toType, ast::GeneratedFlag isGenerated = ast::GeneratedCast
[898ae07]561 ) {
562 if (
563 arg->result->size() > 1
564 && ! toType->isVoid()
565 && ! dynamic_cast< const ast::ReferenceType * >( toType )
566 ) {
567 // Argument is a tuple and the target type is neither void nor a reference. Cast each
568 // member of the tuple to its corresponding target type, producing the tuple of those
569 // cast expressions. If there are more components of the tuple than components in the
570 // target type, then excess components do not come out in the result expression (but
571 // UniqueExpr ensures that the side effects will still be produced)
572 if ( Tuples::maybeImpureIgnoreUnique( arg ) ) {
573 // expressions which may contain side effects require a single unique instance of
574 // the expression
575 arg = new ast::UniqueExpr{ arg->location, arg };
576 }
577 std::vector< ast::ptr< ast::Expr > > components;
578 for ( unsigned i = 0; i < toType->size(); ++i ) {
579 // cast each component
580 ast::ptr< ast::Expr > idx = new ast::TupleIndexExpr{ arg->location, arg, i };
581 components.emplace_back(
582 restructureCast( idx, toType->getComponent( i ), isGenerated ) );
583 }
584 return new ast::TupleExpr{ arg->location, move( components ) };
585 } else {
586 // handle normally
587 return new ast::CastExpr{ arg->location, arg, toType, isGenerated };
588 }
589 }
590
591 /// Gets the name from an untyped member expression (must be NameExpr)
592 const std::string & getMemberName( const ast::UntypedMemberExpr * memberExpr ) {
593 if ( memberExpr->member.as< ast::ConstantExpr >() ) {
594 SemanticError( memberExpr, "Indexed access to struct fields unsupported: " );
595 }
596
597 return memberExpr->member.strict_as< ast::NameExpr >()->name;
[c8e4d2f8]598 }
599
[396037d]600 /// Actually visits expressions to find their candidate interpretations
[4b7cce6]601 struct Finder final : public ast::WithShortCircuiting {
602 CandidateFinder & selfFinder;
[396037d]603 const ast::SymbolTable & symtab;
604 CandidateList & candidates;
605 const ast::TypeEnvironment & tenv;
606 ast::ptr< ast::Type > & targetType;
607
608 Finder( CandidateFinder & f )
[4b7cce6]609 : selfFinder( f ), symtab( f.symtab ), candidates( f.candidates ), tenv( f.env ),
[396037d]610 targetType( f.targetType ) {}
611
[4b7cce6]612 void previsit( const ast::Node * ) { visit_children = false; }
613
614 /// Convenience to add candidate to list
615 template<typename... Args>
616 void addCandidate( Args &&... args ) {
617 candidates.emplace_back( new Candidate{ std::forward<Args>( args )... } );
618 }
619
620 void postvisit( const ast::ApplicationExpr * applicationExpr ) {
621 addCandidate( applicationExpr, tenv );
622 }
623
[9d5089e]624 /// Set up candidate assertions for inference
625 void inferParameters( CandidateRef & newCand, CandidateList & out ) {
626 // Set need bindings for any unbound assertions
627 UniqueId crntResnSlot = 0; // matching ID for this expression's assertions
628 for ( auto & assn : newCand->need ) {
629 // skip already-matched assertions
630 if ( assn.second.resnSlot != 0 ) continue;
631 // assign slot for expression if needed
632 if ( crntResnSlot == 0 ) { crntResnSlot = ++globalResnSlot; }
633 // fix slot to assertion
634 assn.second.resnSlot = crntResnSlot;
635 }
636 // pair slot to expression
637 if ( crntResnSlot != 0 ) {
638 newCand->expr.get_and_mutate()->inferred.resnSlots().emplace_back( crntResnSlot );
639 }
640
641 // add to output list; assertion satisfaction will occur later
642 out.emplace_back( newCand );
643 }
644
645 /// Completes a function candidate with arguments located
646 void validateFunctionCandidate(
647 const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results,
648 CandidateList & out
649 ) {
650 ast::ApplicationExpr * appExpr =
651 new ast::ApplicationExpr{ func->expr->location, func->expr };
652 // sum cost and accumulate arguments
653 std::deque< const ast::Expr * > args;
654 Cost cost = func->cost;
655 const ArgPack * pack = &result;
656 while ( pack->expr ) {
657 args.emplace_front( pack->expr );
658 cost += pack->cost;
659 pack = &results[pack->parent];
660 }
661 std::vector< ast::ptr< ast::Expr > > vargs( args.begin(), args.end() );
662 appExpr->args = move( vargs );
663 // build and validate new candidate
664 auto newCand =
665 std::make_shared<Candidate>( appExpr, result.env, result.open, result.need, cost );
666 PRINT(
667 std::cerr << "instantiate function success: " << appExpr << std::endl;
668 std::cerr << "need assertions:" << std::endl;
669 ast::print( std::cerr, result.need, 2 );
670 )
671 inferParameters( newCand, out );
672 }
673
[432ce7a]674 /// Builds a list of candidates for a function, storing them in out
675 void makeFunctionCandidates(
676 const CandidateRef & func, const ast::FunctionType * funcType,
677 const ExplodedArgs_new & args, CandidateList & out
678 ) {
[9d5089e]679 ast::OpenVarSet funcOpen;
680 ast::AssertionSet funcNeed, funcHave;
681 ast::TypeEnvironment funcEnv{ func->env };
682 makeUnifiableVars( funcType, funcOpen, funcNeed );
683 // add all type variables as open variables now so that those not used in the parameter
684 // list are still considered open
685 funcEnv.add( funcType->forall );
686
687 if ( targetType && ! targetType->isVoid() && ! funcType->returns.empty() ) {
688 // attempt to narrow based on expected target type
689 const ast::Type * returnType = funcType->returns.front()->get_type();
690 if ( ! unify(
691 returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, symtab )
692 ) {
693 // unification failed, do not pursue this candidate
694 return;
695 }
696 }
697
698 // iteratively build matches, one parameter at a time
699 std::vector< ArgPack > results;
700 results.emplace_back( funcEnv, funcNeed, funcHave, funcOpen );
701 std::size_t genStart = 0;
702
703 for ( const ast::DeclWithType * param : funcType->params ) {
704 auto obj = strict_dynamic_cast< const ast::ObjectDecl * >( param );
705 // Try adding the arguments corresponding to the current parameter to the existing
706 // matches
707 if ( ! instantiateArgument(
708 obj->type, obj->init, args, results, genStart, symtab ) ) return;
709 }
710
711 if ( funcType->isVarArgs ) {
712 // append any unused arguments to vararg pack
713 std::size_t genEnd;
714 do {
715 genEnd = results.size();
716
717 // iterate results
718 for ( std::size_t i = genStart; i < genEnd; ++i ) {
719 unsigned nextArg = results[i].nextArg;
720
721 // use remainder of exploded tuple if present
722 if ( results[i].hasExpl() ) {
723 const ExplodedArg & expl = results[i].getExpl( args );
724
725 unsigned nextExpl = results[i].nextExpl + 1;
726 if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
727
728 results.emplace_back(
729 i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
730 copy( results[i].need ), copy( results[i].have ),
731 copy( results[i].open ), nextArg, 0, Cost::zero, nextExpl,
732 results[i].explAlt );
733
734 continue;
735 }
736
737 // finish result when out of arguments
738 if ( nextArg >= args.size() ) {
739 validateFunctionCandidate( func, results[i], results, out );
740
741 continue;
742 }
743
744 // add each possible next argument
745 for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
746 const ExplodedArg & expl = args[nextArg][j];
747
748 // fresh copies of parent parameters for this iteration
749 ast::TypeEnvironment env = results[i].env;
750 ast::OpenVarSet open = results[i].open;
751
752 env.addActual( expl.env, open );
753
754 // skip empty tuple arguments by (nearly) cloning parent into next gen
755 if ( expl.exprs.empty() ) {
756 results.emplace_back(
757 results[i], move( env ), copy( results[i].need ),
758 copy( results[i].have ), move( open ), nextArg + 1,
759 expl.cost );
760
761 continue;
762 }
763
764 // add new result
765 results.emplace_back(
766 i, expl.exprs.front(), move( env ), copy( results[i].need ),
767 copy( results[i].have ), move( open ), nextArg + 1, 0, expl.cost,
768 expl.exprs.size() == 1 ? 0 : 1, j );
769 }
770 }
771
772 genStart = genEnd;
773 } while( genEnd != results.size() );
774 } else {
775 // filter out the results that don't use all the arguments
776 for ( std::size_t i = genStart; i < results.size(); ++i ) {
777 ArgPack & result = results[i];
778 if ( ! result.hasExpl() && result.nextArg >= args.size() ) {
779 validateFunctionCandidate( func, result, results, out );
780 }
781 }
782 }
[4b7cce6]783 }
784
[432ce7a]785 /// Adds implicit struct-conversions to the alternative list
786 void addAnonConversions( const CandidateRef & cand ) {
[c8e4d2f8]787 // adds anonymous member interpretations whenever an aggregate value type is seen.
788 // it's okay for the aggregate expression to have reference type -- cast it to the
789 // base type to treat the aggregate as the referenced value
790 ast::ptr< ast::Expr > aggrExpr( cand->expr );
791 ast::ptr< ast::Type > & aggrType = aggrExpr.get_and_mutate()->result;
792 cand->env.apply( aggrType );
793
794 if ( aggrType.as< ast::ReferenceType >() ) {
[b8524ca]795 aggrExpr = new ast::CastExpr{ aggrExpr, aggrType->stripReferences() };
[c8e4d2f8]796 }
797
798 if ( auto structInst = aggrExpr->result.as< ast::StructInstType >() ) {
[898ae07]799 addAggMembers( structInst, aggrExpr, *cand, Cost::safe, "" );
[c8e4d2f8]800 } else if ( auto unionInst = aggrExpr->result.as< ast::UnionInstType >() ) {
[898ae07]801 addAggMembers( unionInst, aggrExpr, *cand, Cost::safe, "" );
[c8e4d2f8]802 }
803 }
804
805 /// Adds aggregate member interpretations
806 void addAggMembers(
807 const ast::ReferenceToType * aggrInst, const ast::Expr * expr,
[898ae07]808 const Candidate & cand, const Cost & addedCost, const std::string & name
[c8e4d2f8]809 ) {
810 for ( const ast::Decl * decl : aggrInst->lookup( name ) ) {
811 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( decl );
812 CandidateRef newCand = std::make_shared<Candidate>(
[898ae07]813 cand, new ast::MemberExpr{ expr->location, dwt, expr }, addedCost );
[c8e4d2f8]814 // add anonymous member interpretations whenever an aggregate value type is seen
815 // as a member expression
816 addAnonConversions( newCand );
817 candidates.emplace_back( move( newCand ) );
818 }
[432ce7a]819 }
820
[898ae07]821 /// Adds tuple member interpretations
822 void addTupleMembers(
823 const ast::TupleType * tupleType, const ast::Expr * expr, const Candidate & cand,
824 const Cost & addedCost, const ast::Expr * member
825 ) {
826 if ( auto constantExpr = dynamic_cast< const ast::ConstantExpr * >( member ) ) {
827 // get the value of the constant expression as an int, must be between 0 and the
828 // length of the tuple to have meaning
829 long long val = constantExpr->intValue();
830 if ( val >= 0 && (unsigned long long)val < tupleType->size() ) {
831 addCandidate(
832 cand, new ast::TupleIndexExpr{ expr->location, expr, (unsigned)val },
833 addedCost );
834 }
835 }
836 }
837
[432ce7a]838 void postvisit( const ast::UntypedExpr * untypedExpr ) {
839 CandidateFinder funcFinder{ symtab, tenv };
840 funcFinder.find( untypedExpr->func, ResolvMode::withAdjustment() );
841 // short-circuit if no candidates
842 if ( funcFinder.candidates.empty() ) return;
843
844 std::vector< CandidateFinder > argCandidates =
845 selfFinder.findSubExprs( untypedExpr->args );
846
847 // take care of possible tuple assignments
848 // if not tuple assignment, handled as normal function call
849 Tuples::handleTupleAssignment( selfFinder, untypedExpr, argCandidates );
850
851 // find function operators
852 ast::ptr< ast::Expr > opExpr = new ast::NameExpr{ untypedExpr->location, "?()" };
853 CandidateFinder opFinder{ symtab, tenv };
854 // okay if there aren't any function operations
855 opFinder.find( opExpr, ResolvMode::withoutFailFast() );
856 PRINT(
857 std::cerr << "known function ops:" << std::endl;
858 print( std::cerr, opFinder.candidates, 1 );
859 )
860
861 // pre-explode arguments
862 ExplodedArgs_new argExpansions;
863 for ( const CandidateFinder & args : argCandidates ) {
864 argExpansions.emplace_back();
865 auto & argE = argExpansions.back();
866 for ( const CandidateRef & arg : args ) { argE.emplace_back( *arg, symtab ); }
867 }
868
869 // Find function matches
870 CandidateList found;
871 SemanticErrorException errors;
872 for ( CandidateRef & func : funcFinder ) {
873 try {
874 PRINT(
875 std::cerr << "working on alternative:" << std::endl;
876 print( std::cerr, *func, 2 );
877 )
878
879 // check if the type is a pointer to function
880 const ast::Type * funcResult = func->expr->result->stripReferences();
881 if ( auto pointer = dynamic_cast< const ast::PointerType * >( funcResult ) ) {
882 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
883 CandidateRef newFunc{ new Candidate{ *func } };
884 newFunc->expr =
885 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
886 makeFunctionCandidates( newFunc, function, argExpansions, found );
887 }
888 } else if (
889 auto inst = dynamic_cast< const ast::TypeInstType * >( funcResult )
890 ) {
891 if ( const ast::EqvClass * clz = func->env.lookup( inst->name ) ) {
892 if ( auto function = clz->bound.as< ast::FunctionType >() ) {
893 CandidateRef newFunc{ new Candidate{ *func } };
894 newFunc->expr =
895 referenceToRvalueConversion( newFunc->expr, newFunc->cost );
896 makeFunctionCandidates( newFunc, function, argExpansions, found );
897 }
898 }
899 }
900 } catch ( SemanticErrorException & e ) { errors.append( e ); }
901 }
902
903 // Find matches on function operators `?()`
904 if ( ! opFinder.candidates.empty() ) {
905 // add exploded function alternatives to front of argument list
906 std::vector< ExplodedArg > funcE;
907 funcE.reserve( funcFinder.candidates.size() );
908 for ( const CandidateRef & func : funcFinder ) {
909 funcE.emplace_back( *func, symtab );
910 }
[9d5089e]911 argExpansions.emplace_front( move( funcE ) );
[432ce7a]912
913 for ( const CandidateRef & op : opFinder ) {
914 try {
915 // check if type is pointer-to-function
916 const ast::Type * opResult = op->expr->result->stripReferences();
917 if ( auto pointer = dynamic_cast< const ast::PointerType * >( opResult ) ) {
918 if ( auto function = pointer->base.as< ast::FunctionType >() ) {
919 CandidateRef newOp{ new Candidate{ *op} };
920 newOp->expr =
921 referenceToRvalueConversion( newOp->expr, newOp->cost );
922 makeFunctionCandidates( newOp, function, argExpansions, found );
923 }
924 }
925 } catch ( SemanticErrorException & e ) { errors.append( e ); }
926 }
927 }
928
929 // Implement SFINAE; resolution errors are only errors if there aren't any non-error
930 // candidates
931 if ( found.empty() && ! errors.isEmpty() ) { throw errors; }
932
933 // Compute conversion costs
934 for ( CandidateRef & withFunc : found ) {
935 Cost cvtCost = computeApplicationConversionCost( withFunc, symtab );
936
937 PRINT(
938 auto appExpr = withFunc->expr.strict_as< ast::ApplicationExpr >();
939 auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
940 auto function = pointer->base.strict_as< ast::FunctionType >();
941
942 std::cerr << "Case +++++++++++++ " << appExpr->func << std::endl;
943 std::cerr << "parameters are:" << std::endl;
944 ast::printAll( std::cerr, function->params, 2 );
945 std::cerr << "arguments are:" << std::endl;
946 ast::printAll( std::cerr, appExpr->args, 2 );
947 std::cerr << "bindings are:" << std::endl;
948 ast::print( std::cerr, withFunc->env, 2 );
949 std::cerr << "cost is: " << withFunc->cost << std::endl;
950 std::cerr << "cost of conversion is:" << cvtCost << std::endl;
951 )
952
953 if ( cvtCost != Cost::infinity ) {
954 withFunc->cvtCost = cvtCost;
[9d5089e]955 candidates.emplace_back( move( withFunc ) );
[432ce7a]956 }
957 }
[9d5089e]958 found = move( candidates );
[432ce7a]959
960 // use a new list so that candidates are not examined by addAnonConversions twice
961 CandidateList winners = findMinCost( found );
962 promoteCvtCost( winners );
963
964 // function may return a struct/union value, in which case we need to add candidates
965 // for implicit conversions to each of the anonymous members, which must happen after
966 // `findMinCost`, since anon conversions are never the cheapest
967 for ( const CandidateRef & c : winners ) {
968 addAnonConversions( c );
969 }
970 spliceBegin( candidates, winners );
971
972 if ( candidates.empty() && targetType && ! targetType->isVoid() ) {
973 // If resolution is unsuccessful with a target type, try again without, since it
974 // will sometimes succeed when it wouldn't with a target type binding.
975 // For example:
976 // forall( otype T ) T & ?[]( T *, ptrdiff_t );
977 // const char * x = "hello world";
978 // unsigned char ch = x[0];
979 // Fails with simple return type binding (xxx -- check this!) as follows:
980 // * T is bound to unsigned char
981 // * (x: const char *) is unified with unsigned char *, which fails
982 // xxx -- fix this better
983 targetType = nullptr;
984 postvisit( untypedExpr );
985 }
986 }
987
[4b7cce6]988 /// true if expression is an lvalue
989 static bool isLvalue( const ast::Expr * x ) {
990 return x->result && ( x->result->is_lvalue() || x->result.as< ast::ReferenceType >() );
991 }
992
993 void postvisit( const ast::AddressExpr * addressExpr ) {
994 CandidateFinder finder{ symtab, tenv };
995 finder.find( addressExpr->arg );
996 for ( CandidateRef & r : finder.candidates ) {
997 if ( ! isLvalue( r->expr ) ) continue;
998 addCandidate( *r, new ast::AddressExpr{ addressExpr->location, r->expr } );
999 }
1000 }
1001
1002 void postvisit( const ast::LabelAddressExpr * labelExpr ) {
1003 addCandidate( labelExpr, tenv );
1004 }
1005
1006 void postvisit( const ast::CastExpr * castExpr ) {
[c8e4d2f8]1007 ast::ptr< ast::Type > toType = castExpr->result;
1008 assert( toType );
1009 toType = resolveTypeof( toType, symtab );
1010 toType = SymTab::validateType( toType, symtab );
1011 toType = adjustExprType( toType, tenv, symtab );
1012
1013 CandidateFinder finder{ symtab, tenv, toType };
1014 finder.find( castExpr->arg, ResolvMode::withAdjustment() );
1015
1016 CandidateList matches;
1017 for ( CandidateRef & cand : finder.candidates ) {
1018 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1019 ast::OpenVarSet open( cand->open );
1020
1021 cand->env.extractOpenVars( open );
1022
1023 // It is possible that a cast can throw away some values in a multiply-valued
1024 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of the
1025 // subexpression results that are cast directly. The candidate is invalid if it
1026 // has fewer results than there are types to cast to.
1027 int discardedValues = cand->expr->result->size() - toType->size();
1028 if ( discardedValues < 0 ) continue;
1029
1030 // unification run for side-effects
1031 unify( toType, cand->expr->result, cand->env, need, have, open, symtab );
1032 Cost thisCost = castCost( cand->expr->result, toType, symtab, cand->env );
1033 PRINT(
1034 std::cerr << "working on cast with result: " << toType << std::endl;
1035 std::cerr << "and expr type: " << cand->expr->result << std::endl;
1036 std::cerr << "env: " << cand->env << std::endl;
1037 )
1038 if ( thisCost != Cost::infinity ) {
1039 PRINT(
1040 std::cerr << "has finite cost." << std::endl;
1041 )
1042 // count one safe conversion for each value that is thrown away
1043 thisCost.incSafe( discardedValues );
1044 CandidateRef newCand = std::make_shared<Candidate>(
1045 restructureCast( cand->expr, toType, castExpr->isGenerated ),
1046 copy( cand->env ), move( open ), move( need ), cand->cost,
1047 cand->cost + thisCost );
1048 inferParameters( newCand, matches );
1049 }
1050 }
1051
[898ae07]1052 // select first on argument cost, then conversion cost
1053 CandidateList minArgCost = findMinCost( matches );
1054 promoteCvtCost( minArgCost );
1055 candidates = findMinCost( minArgCost );
[4b7cce6]1056 }
1057
1058 void postvisit( const ast::VirtualCastExpr * castExpr ) {
1059 assertf( castExpr->result, "Implicit virtual cast targets not yet supported." );
1060 CandidateFinder finder{ symtab, tenv };
1061 // don't prune here, all alternatives guaranteed to have same type
1062 finder.find( castExpr->arg, ResolvMode::withoutPrune() );
1063 for ( CandidateRef & r : finder.candidates ) {
1064 addCandidate(
[c8e4d2f8]1065 *r,
1066 new ast::VirtualCastExpr{ castExpr->location, r->expr, castExpr->result } );
[4b7cce6]1067 }
1068 }
1069
1070 void postvisit( const ast::UntypedMemberExpr * memberExpr ) {
[898ae07]1071 CandidateFinder aggFinder{ symtab, tenv };
1072 aggFinder.find( memberExpr->aggregate, ResolvMode::withAdjustment() );
1073 for ( CandidateRef & agg : aggFinder.candidates ) {
1074 // it's okay for the aggregate expression to have reference type -- cast it to the
1075 // base type to treat the aggregate as the referenced value
1076 Cost addedCost = Cost::zero;
1077 agg->expr = referenceToRvalueConversion( agg->expr, addedCost );
1078
1079 // find member of the given type
1080 if ( auto structInst = agg->expr->result.as< ast::StructInstType >() ) {
1081 addAggMembers(
1082 structInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1083 } else if ( auto unionInst = agg->expr->result.as< ast::UnionInstType >() ) {
1084 addAggMembers(
1085 unionInst, agg->expr, *agg, addedCost, getMemberName( memberExpr ) );
1086 } else if ( auto tupleType = agg->expr->result.as< ast::TupleType >() ) {
1087 addTupleMembers( tupleType, agg->expr, *agg, addedCost, memberExpr->member );
1088 }
1089 }
[4b7cce6]1090 }
1091
1092 void postvisit( const ast::MemberExpr * memberExpr ) {
1093 addCandidate( memberExpr, tenv );
1094 }
1095
[898ae07]1096 void postvisit( const ast::NameExpr * nameExpr ) {
1097 std::vector< ast::SymbolTable::IdData > declList = symtab.lookupId( nameExpr->name );
1098 PRINT( std::cerr << "nameExpr is " << nameExpr->name << std::endl; )
1099 for ( auto & data : declList ) {
1100 Cost cost = Cost::zero;
1101 ast::Expr * newExpr = data.combine( nameExpr->location, cost );
1102
1103 CandidateRef newCand = std::make_shared<Candidate>(
1104 newExpr, copy( tenv ), ast::OpenVarSet{}, ast::AssertionSet{}, Cost::zero,
1105 cost );
1106 PRINT(
1107 std::cerr << "decl is ";
1108 ast::print( std::cerr, data.id );
1109 std::cerr << std::endl;
1110 std::cerr << "newExpr is ";
1111 ast::print( std::cerr, newExpr );
1112 std::cerr << std::endl;
1113 )
1114 newCand->expr = ast::mutate_field(
1115 newCand->expr.get(), &ast::Expr::result,
1116 renameTyVars( newCand->expr->result ) );
1117 // add anonymous member interpretations whenever an aggregate value type is seen
1118 // as a name expression
1119 addAnonConversions( newCand );
1120 candidates.emplace_back( move( newCand ) );
1121 }
[4b7cce6]1122 }
1123
1124 void postvisit( const ast::VariableExpr * variableExpr ) {
1125 // not sufficient to just pass `variableExpr` here, type might have changed since
1126 // creation
1127 addCandidate(
1128 new ast::VariableExpr{ variableExpr->location, variableExpr->var }, tenv );
1129 }
1130
1131 void postvisit( const ast::ConstantExpr * constantExpr ) {
1132 addCandidate( constantExpr, tenv );
1133 }
1134
1135 void postvisit( const ast::SizeofExpr * sizeofExpr ) {
[898ae07]1136 if ( sizeofExpr->type ) {
1137 addCandidate(
1138 new ast::SizeofExpr{
1139 sizeofExpr->location, resolveTypeof( sizeofExpr->type, symtab ) },
1140 tenv );
1141 } else {
1142 // find all candidates for the argument to sizeof
1143 CandidateFinder finder{ symtab, tenv };
1144 finder.find( sizeofExpr->expr );
1145 // find the lowest-cost candidate, otherwise ambiguous
1146 CandidateList winners = findMinCost( finder.candidates );
1147 if ( winners.size() != 1 ) {
1148 SemanticError(
1149 sizeofExpr->expr.get(), "Ambiguous expression in sizeof operand: " );
1150 }
1151 // return the lowest-cost candidate
1152 CandidateRef & choice = winners.front();
1153 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1154 choice->cost = Cost::zero;
1155 addCandidate( *choice, new ast::SizeofExpr{ sizeofExpr->location, choice->expr } );
1156 }
[4b7cce6]1157 }
1158
1159 void postvisit( const ast::AlignofExpr * alignofExpr ) {
[898ae07]1160 if ( alignofExpr->type ) {
1161 addCandidate(
1162 new ast::AlignofExpr{
1163 alignofExpr->location, resolveTypeof( alignofExpr->type, symtab ) },
1164 tenv );
1165 } else {
1166 // find all candidates for the argument to alignof
1167 CandidateFinder finder{ symtab, tenv };
1168 finder.find( alignofExpr->expr );
1169 // find the lowest-cost candidate, otherwise ambiguous
1170 CandidateList winners = findMinCost( finder.candidates );
1171 if ( winners.size() != 1 ) {
1172 SemanticError(
1173 alignofExpr->expr.get(), "Ambiguous expression in alignof operand: " );
1174 }
1175 // return the lowest-cost candidate
1176 CandidateRef & choice = winners.front();
1177 choice->expr = referenceToRvalueConversion( choice->expr, choice->cost );
1178 choice->cost = Cost::zero;
1179 addCandidate(
1180 *choice, new ast::AlignofExpr{ alignofExpr->location, choice->expr } );
1181 }
[4b7cce6]1182 }
1183
1184 void postvisit( const ast::UntypedOffsetofExpr * offsetofExpr ) {
[898ae07]1185 const ast::ReferenceToType * aggInst;
1186 if (( aggInst = offsetofExpr->type.as< ast::StructInstType >() )) ;
1187 else if (( aggInst = offsetofExpr->type.as< ast::UnionInstType >() )) ;
1188 else return;
1189
1190 for ( const ast::Decl * member : aggInst->lookup( offsetofExpr->member ) ) {
1191 auto dwt = strict_dynamic_cast< const ast::DeclWithType * >( member );
1192 addCandidate(
1193 new ast::OffsetofExpr{ offsetofExpr->location, aggInst, dwt }, tenv );
1194 }
[4b7cce6]1195 }
1196
1197 void postvisit( const ast::OffsetofExpr * offsetofExpr ) {
1198 addCandidate( offsetofExpr, tenv );
1199 }
1200
1201 void postvisit( const ast::OffsetPackExpr * offsetPackExpr ) {
1202 addCandidate( offsetPackExpr, tenv );
1203 }
1204
1205 void postvisit( const ast::LogicalExpr * logicalExpr ) {
1206 CandidateFinder finder1{ symtab, tenv };
1207 finder1.find( logicalExpr->arg1, ResolvMode::withAdjustment() );
1208 if ( finder1.candidates.empty() ) return;
1209
1210 CandidateFinder finder2{ symtab, tenv };
1211 finder2.find( logicalExpr->arg2, ResolvMode::withAdjustment() );
1212 if ( finder2.candidates.empty() ) return;
1213
1214 for ( const CandidateRef & r1 : finder1.candidates ) {
1215 for ( const CandidateRef & r2 : finder2.candidates ) {
1216 ast::TypeEnvironment env{ r1->env };
1217 env.simpleCombine( r2->env );
1218 ast::OpenVarSet open{ r1->open };
1219 mergeOpenVars( open, r2->open );
1220 ast::AssertionSet need;
1221 mergeAssertionSet( need, r1->need );
1222 mergeAssertionSet( need, r2->need );
1223
1224 addCandidate(
1225 new ast::LogicalExpr{
1226 logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
[9d5089e]1227 move( env ), move( open ), move( need ), r1->cost + r2->cost );
[4b7cce6]1228 }
1229 }
1230 }
1231
1232 void postvisit( const ast::ConditionalExpr * conditionalExpr ) {
1233 // candidates for condition
1234 CandidateFinder finder1{ symtab, tenv };
1235 finder1.find( conditionalExpr->arg1, ResolvMode::withAdjustment() );
1236 if ( finder1.candidates.empty() ) return;
1237
1238 // candidates for true result
1239 CandidateFinder finder2{ symtab, tenv };
1240 finder2.find( conditionalExpr->arg2, ResolvMode::withAdjustment() );
1241 if ( finder2.candidates.empty() ) return;
1242
1243 // candidates for false result
1244 CandidateFinder finder3{ symtab, tenv };
1245 finder3.find( conditionalExpr->arg3, ResolvMode::withAdjustment() );
1246 if ( finder3.candidates.empty() ) return;
1247
1248 for ( const CandidateRef & r1 : finder1.candidates ) {
1249 for ( const CandidateRef & r2 : finder2.candidates ) {
1250 for ( const CandidateRef & r3 : finder3.candidates ) {
1251 ast::TypeEnvironment env{ r1->env };
1252 env.simpleCombine( r2->env );
1253 env.simpleCombine( r3->env );
1254 ast::OpenVarSet open{ r1->open };
1255 mergeOpenVars( open, r2->open );
1256 mergeOpenVars( open, r3->open );
1257 ast::AssertionSet need;
1258 mergeAssertionSet( need, r1->need );
1259 mergeAssertionSet( need, r2->need );
1260 mergeAssertionSet( need, r3->need );
1261 ast::AssertionSet have;
1262
1263 // unify true and false results, then infer parameters to produce new
1264 // candidates
1265 ast::ptr< ast::Type > common;
1266 if (
1267 unify(
1268 r2->expr->result, r3->expr->result, env, need, have, open, symtab,
1269 common )
1270 ) {
[898ae07]1271 // generate typed expression
1272 ast::ConditionalExpr * newExpr = new ast::ConditionalExpr{
1273 conditionalExpr->location, r1->expr, r2->expr, r3->expr };
1274 newExpr->result = common ? common : r2->expr->result;
1275 // convert both options to result type
1276 Cost cost = r1->cost + r2->cost + r3->cost;
1277 newExpr->arg2 = computeExpressionConversionCost(
1278 newExpr->arg2, newExpr->result, symtab, env, cost );
1279 newExpr->arg3 = computeExpressionConversionCost(
1280 newExpr->arg3, newExpr->result, symtab, env, cost );
1281 // output candidate
1282 CandidateRef newCand = std::make_shared<Candidate>(
1283 newExpr, move( env ), move( open ), move( need ), cost );
1284 inferParameters( newCand, candidates );
[4b7cce6]1285 }
1286 }
1287 }
1288 }
1289 }
1290
1291 void postvisit( const ast::CommaExpr * commaExpr ) {
1292 ast::TypeEnvironment env{ tenv };
1293 ast::ptr< ast::Expr > arg1 = resolveInVoidContext( commaExpr->arg1, symtab, env );
1294
1295 CandidateFinder finder2{ symtab, env };
1296 finder2.find( commaExpr->arg2, ResolvMode::withAdjustment() );
1297
1298 for ( const CandidateRef & r2 : finder2.candidates ) {
1299 addCandidate( *r2, new ast::CommaExpr{ commaExpr->location, arg1, r2->expr } );
1300 }
1301 }
1302
1303 void postvisit( const ast::ImplicitCopyCtorExpr * ctorExpr ) {
1304 addCandidate( ctorExpr, tenv );
1305 }
1306
1307 void postvisit( const ast::ConstructorExpr * ctorExpr ) {
1308 CandidateFinder finder{ symtab, tenv };
1309 finder.find( ctorExpr->callExpr, ResolvMode::withoutPrune() );
1310 for ( CandidateRef & r : finder.candidates ) {
1311 addCandidate( *r, new ast::ConstructorExpr{ ctorExpr->location, r->expr } );
1312 }
1313 }
1314
1315 void postvisit( const ast::RangeExpr * rangeExpr ) {
1316 // resolve low and high, accept candidates where low and high types unify
1317 CandidateFinder finder1{ symtab, tenv };
1318 finder1.find( rangeExpr->low, ResolvMode::withAdjustment() );
1319 if ( finder1.candidates.empty() ) return;
1320
1321 CandidateFinder finder2{ symtab, tenv };
1322 finder2.find( rangeExpr->high, ResolvMode::withAdjustment() );
1323 if ( finder2.candidates.empty() ) return;
1324
1325 for ( const CandidateRef & r1 : finder1.candidates ) {
1326 for ( const CandidateRef & r2 : finder2.candidates ) {
1327 ast::TypeEnvironment env{ r1->env };
1328 env.simpleCombine( r2->env );
1329 ast::OpenVarSet open{ r1->open };
1330 mergeOpenVars( open, r2->open );
1331 ast::AssertionSet need;
1332 mergeAssertionSet( need, r1->need );
1333 mergeAssertionSet( need, r2->need );
1334 ast::AssertionSet have;
1335
1336 ast::ptr< ast::Type > common;
1337 if (
1338 unify(
1339 r1->expr->result, r2->expr->result, env, need, have, open, symtab,
1340 common )
1341 ) {
[898ae07]1342 // generate new expression
[4b7cce6]1343 ast::RangeExpr * newExpr =
1344 new ast::RangeExpr{ rangeExpr->location, r1->expr, r2->expr };
1345 newExpr->result = common ? common : r1->expr->result;
[898ae07]1346 // add candidate
1347 CandidateRef newCand = std::make_shared<Candidate>(
1348 newExpr, move( env ), move( open ), move( need ),
1349 r1->cost + r2->cost );
1350 inferParameters( newCand, candidates );
[4b7cce6]1351 }
1352 }
1353 }
1354 }
1355
1356 void postvisit( const ast::UntypedTupleExpr * tupleExpr ) {
1357 std::vector< CandidateFinder > subCandidates =
1358 selfFinder.findSubExprs( tupleExpr->exprs );
1359 std::vector< CandidateList > possibilities;
1360 combos( subCandidates.begin(), subCandidates.end(), back_inserter( possibilities ) );
1361
1362 for ( const CandidateList & subs : possibilities ) {
1363 std::vector< ast::ptr< ast::Expr > > exprs;
1364 exprs.reserve( subs.size() );
1365 for ( const CandidateRef & sub : subs ) { exprs.emplace_back( sub->expr ); }
1366
1367 ast::TypeEnvironment env;
1368 ast::OpenVarSet open;
1369 ast::AssertionSet need;
1370 for ( const CandidateRef & sub : subs ) {
1371 env.simpleCombine( sub->env );
1372 mergeOpenVars( open, sub->open );
1373 mergeAssertionSet( need, sub->need );
1374 }
1375
1376 addCandidate(
[9d5089e]1377 new ast::TupleExpr{ tupleExpr->location, move( exprs ) },
1378 move( env ), move( open ), move( need ), sumCost( subs ) );
[4b7cce6]1379 }
1380 }
1381
1382 void postvisit( const ast::TupleExpr * tupleExpr ) {
1383 addCandidate( tupleExpr, tenv );
1384 }
1385
1386 void postvisit( const ast::TupleIndexExpr * tupleExpr ) {
1387 addCandidate( tupleExpr, tenv );
1388 }
1389
1390 void postvisit( const ast::TupleAssignExpr * tupleExpr ) {
1391 addCandidate( tupleExpr, tenv );
1392 }
1393
1394 void postvisit( const ast::UniqueExpr * unqExpr ) {
1395 CandidateFinder finder{ symtab, tenv };
1396 finder.find( unqExpr->expr, ResolvMode::withAdjustment() );
1397 for ( CandidateRef & r : finder.candidates ) {
1398 // ensure that the the id is passed on so that the expressions are "linked"
1399 addCandidate( *r, new ast::UniqueExpr{ unqExpr->location, r->expr, unqExpr->id } );
1400 }
1401 }
1402
1403 void postvisit( const ast::StmtExpr * stmtExpr ) {
[17a0ede2]1404 addCandidate( resolveStmtExpr( stmtExpr, symtab ), tenv );
[4b7cce6]1405 }
1406
1407 void postvisit( const ast::UntypedInitExpr * initExpr ) {
[17a0ede2]1408 // handle each option like a cast
1409 CandidateList matches;
1410 PRINT(
1411 std::cerr << "untyped init expr: " << initExpr << std::endl;
1412 )
1413 // O(n^2) checks of d-types with e-types
1414 for ( const ast::InitAlternative & initAlt : initExpr->initAlts ) {
1415 // calculate target type
1416 const ast::Type * toType = resolveTypeof( initAlt.type, symtab );
1417 toType = SymTab::validateType( toType, symtab );
1418 toType = adjustExprType( toType, tenv, symtab );
1419 // The call to find must occur inside this loop, otherwise polymorphic return
1420 // types are not bound to the initialization type, since return type variables are
1421 // only open for the duration of resolving the UntypedExpr.
1422 CandidateFinder finder{ symtab, tenv, toType };
1423 finder.find( initExpr->expr, ResolvMode::withAdjustment() );
1424 for ( CandidateRef & cand : finder.candidates ) {
1425 ast::TypeEnvironment env{ cand->env };
1426 ast::AssertionSet need( cand->need.begin(), cand->need.end() ), have;
1427 ast::OpenVarSet open{ cand->open };
1428
1429 PRINT(
1430 std::cerr << " @ " << toType << " " << initAlt.designation << std::endl;
1431 )
1432
1433 // It is possible that a cast can throw away some values in a multiply-valued
1434 // expression, e.g. cast-to-void, one value to zero. Figure out the prefix of
1435 // the subexpression results that are cast directly. The candidate is invalid
1436 // if it has fewer results than there are types to cast to.
1437 int discardedValues = cand->expr->result->size() - toType->size();
1438 if ( discardedValues < 0 ) continue;
1439
1440 // unification run for side-effects
1441 unify( toType, cand->expr->result, env, need, have, open, symtab );
1442 Cost thisCost = castCost( cand->expr->result, toType, symtab, env );
1443
1444 if ( thisCost != Cost::infinity ) {
1445 // count one safe conversion for each value that is thrown away
1446 thisCost.incSafe( discardedValues );
1447 CandidateRef newCand = std::make_shared<Candidate>(
1448 new ast::InitExpr{
1449 initExpr->location, restructureCast( cand->expr, toType ),
1450 initAlt.designation },
1451 copy( cand->env ), move( open ), move( need ), cand->cost, thisCost );
1452 inferParameters( newCand, matches );
1453 }
1454 }
1455 }
1456
1457 // select first on argument cost, then conversion cost
1458 CandidateList minArgCost = findMinCost( matches );
1459 promoteCvtCost( minArgCost );
1460 candidates = findMinCost( minArgCost );
[4b7cce6]1461 }
1462
1463 void postvisit( const ast::InitExpr * ) {
1464 assertf( false, "CandidateFinder should never see a resolved InitExpr." );
1465 }
1466
1467 void postvisit( const ast::DeletedExpr * ) {
1468 assertf( false, "CandidateFinder should never see a DeletedExpr." );
1469 }
1470
1471 void postvisit( const ast::GenericExpr * ) {
1472 assertf( false, "_Generic is not yet supported." );
1473 }
[396037d]1474 };
1475
1476 /// Prunes a list of candidates down to those that have the minimum conversion cost for a given
1477 /// return type. Skips ambiguous candidates.
1478 CandidateList pruneCandidates( CandidateList & candidates ) {
[d57e349]1479 struct PruneStruct {
1480 CandidateRef candidate;
1481 bool ambiguous;
1482
1483 PruneStruct() = default;
1484 PruneStruct( const CandidateRef & c ) : candidate( c ), ambiguous( false ) {}
1485 };
1486
1487 // find lowest-cost candidate for each type
1488 std::unordered_map< std::string, PruneStruct > selected;
1489 for ( CandidateRef & candidate : candidates ) {
1490 std::string mangleName;
1491 {
1492 ast::ptr< ast::Type > newType = candidate->expr->result;
1493 candidate->env.apply( newType );
1494 mangleName = Mangle::mangle( newType );
1495 }
1496
1497 auto found = selected.find( mangleName );
1498 if ( found != selected.end() ) {
1499 if ( candidate->cost < found->second.candidate->cost ) {
1500 PRINT(
1501 std::cerr << "cost " << candidate->cost << " beats "
1502 << found->second.candidate->cost << std::endl;
1503 )
1504
1505 found->second = PruneStruct{ candidate };
1506 } else if ( candidate->cost == found->second.candidate->cost ) {
1507 // if one of the candidates contains a deleted identifier, can pick the other,
1508 // since deleted expressions should not be ambiguous if there is another option
1509 // that is at least as good
1510 if ( findDeletedExpr( candidate->expr ) ) {
1511 // do nothing
1512 PRINT( std::cerr << "candidate is deleted" << std::endl; )
1513 } else if ( findDeletedExpr( found->second.candidate->expr ) ) {
1514 PRINT( std::cerr << "current is deleted" << std::endl; )
1515 found->second = PruneStruct{ candidate };
1516 } else {
1517 PRINT( std::cerr << "marking ambiguous" << std::endl; )
1518 found->second.ambiguous = true;
1519 }
1520 } else {
1521 PRINT(
1522 std::cerr << "cost " << candidate->cost << " loses to "
1523 << found->second.candidate->cost << std::endl;
1524 )
1525 }
1526 } else {
1527 selected.emplace_hint( found, mangleName, candidate );
1528 }
1529 }
1530
1531 // report unambiguous min-cost candidates
1532 CandidateList out;
1533 for ( auto & target : selected ) {
1534 if ( target.second.ambiguous ) continue;
1535
1536 CandidateRef cand = target.second.candidate;
1537
1538 ast::ptr< ast::Type > newResult = cand->expr->result;
1539 cand->env.applyFree( newResult );
1540 cand->expr = ast::mutate_field(
[9d5089e]1541 cand->expr.get(), &ast::Expr::result, move( newResult ) );
[d57e349]1542
1543 out.emplace_back( cand );
1544 }
1545 return out;
1546 }
1547
[396037d]1548} // anonymous namespace
1549
[99d4584]1550void CandidateFinder::find( const ast::Expr * expr, ResolvMode mode ) {
[396037d]1551 // Find alternatives for expression
1552 ast::Pass<Finder> finder{ *this };
1553 expr->accept( finder );
1554
1555 if ( mode.failFast && candidates.empty() ) {
1556 SemanticError( expr, "No reasonable alternatives for expression " );
1557 }
1558
1559 if ( mode.satisfyAssns || mode.prune ) {
1560 // trim candidates to just those where the assertions are satisfiable
1561 // - necessary pre-requisite to pruning
1562 CandidateList satisfied;
1563 std::vector< std::string > errors;
[b69233ac]1564 for ( CandidateRef & candidate : candidates ) {
1565 satisfyAssertions( candidate, symtab, satisfied, errors );
[396037d]1566 }
1567
1568 // fail early if none such
1569 if ( mode.failFast && satisfied.empty() ) {
1570 std::ostringstream stream;
1571 stream << "No alternatives with satisfiable assertions for " << expr << "\n";
1572 for ( const auto& err : errors ) {
1573 stream << err;
1574 }
1575 SemanticError( expr->location, stream.str() );
1576 }
1577
1578 // reset candidates
[9d5089e]1579 candidates = move( satisfied );
[396037d]1580 }
1581
1582 if ( mode.prune ) {
1583 // trim candidates to single best one
1584 PRINT(
1585 std::cerr << "alternatives before prune:" << std::endl;
1586 print( std::cerr, candidates );
1587 )
1588
1589 CandidateList pruned = pruneCandidates( candidates );
[d57e349]1590
[396037d]1591 if ( mode.failFast && pruned.empty() ) {
1592 std::ostringstream stream;
[d57e349]1593 CandidateList winners = findMinCost( candidates );
1594 stream << "Cannot choose between " << winners.size() << " alternatives for "
1595 "expression\n";
1596 ast::print( stream, expr );
1597 stream << " Alternatives are:\n";
1598 print( stream, winners, 1 );
1599 SemanticError( expr->location, stream.str() );
[396037d]1600 }
[d57e349]1601
1602 auto oldsize = candidates.size();
[9d5089e]1603 candidates = move( pruned );
[d57e349]1604
1605 PRINT(
1606 std::cerr << "there are " << oldsize << " alternatives before elimination" << std::endl;
1607 )
1608 PRINT(
1609 std::cerr << "there are " << candidates.size() << " alternatives after elimination"
1610 << std::endl;
1611 )
[396037d]1612 }
1613
[d57e349]1614 // adjust types after pruning so that types substituted by pruneAlternatives are correctly
1615 // adjusted
1616 if ( mode.adjust ) {
1617 for ( CandidateRef & r : candidates ) {
1618 r->expr = ast::mutate_field(
1619 r->expr.get(), &ast::Expr::result,
1620 adjustExprType( r->expr->result, r->env, symtab ) );
1621 }
1622 }
1623
1624 // Central location to handle gcc extension keyword, etc. for all expressions
1625 for ( CandidateRef & r : candidates ) {
1626 if ( r->expr->extension != expr->extension ) {
1627 r->expr.get_and_mutate()->extension = expr->extension;
1628 }
1629 }
[99d4584]1630}
1631
[2773ab8]1632std::vector< CandidateFinder > CandidateFinder::findSubExprs(
1633 const std::vector< ast::ptr< ast::Expr > > & xs
1634) {
1635 std::vector< CandidateFinder > out;
1636
[396037d]1637 for ( const auto & x : xs ) {
1638 out.emplace_back( symtab, env );
1639 out.back().find( x, ResolvMode::withAdjustment() );
1640
1641 PRINT(
1642 std::cerr << "findSubExprs" << std::endl;
1643 print( std::cerr, out.back().candidates );
1644 )
1645 }
[2773ab8]1646
1647 return out;
1648}
1649
[99d4584]1650} // namespace ResolvExpr
1651
1652// Local Variables: //
1653// tab-width: 4 //
1654// mode: c++ //
1655// compile-command: "make install" //
1656// End: //
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