source: src/GenPoly/Lvalue.cc@ 24ed606

ADT aaron-thesis arm-eh ast-experimental cleanup-dtors deferred_resn demangler enum forall-pointer-decay jacob/cs343-translation jenkins-sandbox new-ast new-ast-unique-expr new-env no_list persistent-indexer pthread-emulation qualifiedEnum resolv-new with_gc
Last change on this file since 24ed606 was 1a4bef3, checked in by Rob Schluntz <rschlunt@…>, 8 years ago

Ensure that dereference type is marked as lvalue after reference conversion [fixes #74]
  • Property mode set to 100644
File size: 19.4 KB
Line 
1//
2// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
3//
4// The contents of this file are covered under the licence agreement in the
5// file "LICENCE" distributed with Cforall.
6//
7// Lvalue.cc --
8//
9// Author : Richard C. Bilson
10// Created On : Mon May 18 07:44:20 2015
11// Last Modified By : Peter A. Buhr
12// Last Modified On : Fri Mar 17 09:11:18 2017
13// Update Count : 5
14//
15
16#include <cassert> // for strict_dynamic_cast
17#include <string> // for string
18
19#include "Common/PassVisitor.h"
20#include "Common/SemanticError.h" // for SemanticError
21#include "GenPoly.h" // for isPolyType
22#include "Lvalue.h"
23
24#include "Parser/LinkageSpec.h" // for Spec, isBuiltin, Intrinsic
25#include "ResolvExpr/TypeEnvironment.h" // for AssertionSet, OpenVarSet
26#include "ResolvExpr/Unify.h" // for unify
27#include "ResolvExpr/typeops.h"
28#include "SymTab/Autogen.h"
29#include "SymTab/Indexer.h" // for Indexer
30#include "SynTree/Declaration.h" // for Declaration, FunctionDecl
31#include "SynTree/Expression.h" // for Expression, ConditionalExpr
32#include "SynTree/Mutator.h" // for mutateAll, Mutator
33#include "SynTree/Statement.h" // for ReturnStmt, Statement (ptr o...
34#include "SynTree/Type.h" // for PointerType, Type, FunctionType
35#include "SynTree/Visitor.h" // for Visitor, acceptAll
36
37#if 0
38#define PRINT(x) x
39#else
40#define PRINT(x)
41#endif
42
43namespace GenPoly {
44 namespace {
45 // TODO: fold this into the general createDeref function??
46 Expression * mkDeref( Expression * arg ) {
47 if ( SymTab::dereferenceOperator ) {
48 VariableExpr * deref = new VariableExpr( SymTab::dereferenceOperator );
49 deref->result = new PointerType( Type::Qualifiers(), deref->result );
50 Type * base = InitTweak::getPointerBase( arg->result );
51 assertf( base, "expected pointer type in dereference (type was %s)", toString( arg->result ).c_str() );
52 ApplicationExpr * ret = new ApplicationExpr( deref, { arg } );
53 delete ret->result;
54 ret->result = base->clone();
55 ret->result->set_lvalue( true );
56 return ret;
57 } else {
58 return UntypedExpr::createDeref( arg );
59 }
60 }
61
62 struct ReferenceConversions final {
63 Expression * postmutate( CastExpr * castExpr );
64 Expression * postmutate( AddressExpr * addrExpr );
65 };
66
67 /// Intrinsic functions that take reference parameters don't REALLY take reference parameters -- their reference arguments must always be implicitly dereferenced.
68 struct FixIntrinsicArgs final {
69 Expression * postmutate( ApplicationExpr * appExpr );
70 };
71
72 struct FixIntrinsicResult final : public WithGuards {
73 Expression * postmutate( ApplicationExpr * appExpr );
74 void premutate( FunctionDecl * funcDecl );
75 bool inIntrinsic = false;
76 };
77
78 /// Replace reference types with pointer types
79 struct ReferenceTypeElimination final {
80 Type * postmutate( ReferenceType * refType );
81 };
82
83 /// GCC-like Generalized Lvalues (which have since been removed from GCC)
84 /// https://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Lvalues.html#Lvalues
85 /// Replaces &(a,b) with (a, &b), &(a ? b : c) with (a ? &b : &c)
86 struct GeneralizedLvalue final : public WithVisitorRef<GeneralizedLvalue> {
87 Expression * postmutate( AddressExpr * addressExpr );
88 Expression * postmutate( MemberExpr * memExpr );
89
90 template<typename Func>
91 Expression * applyTransformation( Expression * expr, Expression * arg, Func mkExpr );
92 };
93
94 /// Removes redundant &*/*& pattern that this pass can generate
95 struct CollapseAddrDeref final {
96 Expression * postmutate( AddressExpr * addressExpr );
97 Expression * postmutate( ApplicationExpr * appExpr );
98 };
99
100 struct AddrRef final : public WithGuards {
101 void premutate( AddressExpr * addrExpr );
102 Expression * postmutate( AddressExpr * addrExpr );
103 void premutate( Expression * expr );
104
105 bool first = true;
106 bool current = false;
107 int refDepth = 0;
108 };
109 } // namespace
110
111 static bool referencesEliminated = false;
112 // used by UntypedExpr::createDeref to determine whether result type of dereference should be ReferenceType or value type.
113 bool referencesPermissable() {
114 return ! referencesEliminated;
115 }
116
117 void convertLvalue( std::list< Declaration* >& translationUnit ) {
118 PassVisitor<ReferenceConversions> refCvt;
119 PassVisitor<ReferenceTypeElimination> elim;
120 PassVisitor<GeneralizedLvalue> genLval;
121 PassVisitor<FixIntrinsicArgs> fixer;
122 PassVisitor<CollapseAddrDeref> collapser;
123 PassVisitor<AddrRef> addrRef;
124 PassVisitor<FixIntrinsicResult> intrinsicResults;
125 mutateAll( translationUnit, intrinsicResults );
126 mutateAll( translationUnit, addrRef );
127 mutateAll( translationUnit, refCvt );
128 mutateAll( translationUnit, fixer );
129 mutateAll( translationUnit, collapser );
130 mutateAll( translationUnit, genLval );
131 mutateAll( translationUnit, elim ); // last because other passes need reference types to work
132
133 // from this point forward, no other pass should create reference types.
134 referencesEliminated = true;
135 }
136
137 Expression * generalizedLvalue( Expression * expr ) {
138 PassVisitor<GeneralizedLvalue> genLval;
139 return expr->acceptMutator( genLval );
140 }
141
142 namespace {
143 // true for intrinsic function calls that return a reference
144 bool isIntrinsicReference( Expression * expr ) {
145 if ( UntypedExpr * untyped = dynamic_cast< UntypedExpr * >( expr ) ) {
146 std::string fname = InitTweak::getFunctionName( untyped );
147 // known intrinsic-reference prelude functions
148 return fname == "*?" || fname == "?[?]";
149 } else if ( ApplicationExpr * appExpr = dynamic_cast< ApplicationExpr * > ( expr ) ) {
150 if ( DeclarationWithType * func = InitTweak::getFunction( appExpr ) ) {
151 // use type of return variable rather than expr result type, since it may have been changed to a pointer type
152 FunctionType * ftype = GenPoly::getFunctionType( func->get_type() );
153 Type * ret = ftype->get_returnVals().empty() ? nullptr : ftype->get_returnVals().front()->get_type();
154 return func->get_linkage() == LinkageSpec::Intrinsic && dynamic_cast<ReferenceType *>( ret );
155 }
156 }
157 return false;
158 }
159
160 Expression * FixIntrinsicResult::postmutate( ApplicationExpr * appExpr ) {
161 if ( isIntrinsicReference( appExpr ) ) {
162 // eliminate reference types from intrinsic applications - now they return lvalues
163 Type * result = appExpr->get_result();
164 appExpr->set_result( result->stripReferences()->clone() );
165 appExpr->get_result()->set_lvalue( true );
166 if ( ! inIntrinsic ) {
167 // when not in an intrinsic function, add a cast to
168 // don't add cast when in an intrinsic function, since they already have the cast
169 Expression * ret = new CastExpr( appExpr, result );
170 ret->set_env( appExpr->get_env() );
171 appExpr->set_env( nullptr );
172 return ret;
173 }
174 delete result;
175 }
176 return appExpr;
177 }
178
179 void FixIntrinsicResult::premutate( FunctionDecl * funcDecl ) {
180 GuardValue( inIntrinsic );
181 inIntrinsic = funcDecl->linkage == LinkageSpec::Intrinsic;
182 }
183
184 Expression * FixIntrinsicArgs::postmutate( ApplicationExpr * appExpr ) {
185 // intrinsic functions don't really take reference-typed parameters, so they require an implicit dereference on their arguments.
186 if ( DeclarationWithType * function = InitTweak::getFunction( appExpr ) ) {
187 FunctionType * ftype = GenPoly::getFunctionType( function->get_type() );
188 assertf( ftype, "Function declaration does not have function type." );
189 // can be of differing lengths only when function is variadic
190 assertf( ftype->get_parameters().size() == appExpr->get_args().size() || ftype->get_isVarArgs(), "ApplicationExpr args do not match formal parameter type." );
191
192
193 unsigned int i = 0;
194 const unsigned int end = ftype->get_parameters().size();
195 for ( auto p : unsafe_group_iterate( appExpr->get_args(), ftype->get_parameters() ) ) {
196 if (i == end) break;
197 Expression *& arg = std::get<0>( p );
198 Type * formal = std::get<1>( p )->get_type();
199 PRINT(
200 std::cerr << "pair<0>: " << arg << std::endl;
201 std::cerr << "pair<1>: " << formal << std::endl;
202 )
203 if ( dynamic_cast<ReferenceType*>( formal ) ) {
204 if ( isIntrinsicReference( arg ) ) { // do not combine conditions, because that changes the meaning of the else if
205 if ( function->get_linkage() != LinkageSpec::Intrinsic ) { // intrinsic functions that turn pointers into references
206 // if argument is dereference or array subscript, the result isn't REALLY a reference, so it's not necessary to fix the argument
207 PRINT(
208 std::cerr << "===is intrinsic arg in non-intrinsic call - adding address" << std::endl;
209 )
210 arg = new AddressExpr( arg );
211 }
212 } else if ( function->get_linkage() == LinkageSpec::Intrinsic ) {
213 // std::cerr << "===adding deref to arg" << std::endl;
214 // if the parameter is a reference, add a dereference to the reference-typed argument.
215 Type * baseType = InitTweak::getPointerBase( arg->get_result() );
216 assertf( baseType, "parameter is reference, arg must be pointer or reference: %s", toString( arg->get_result() ).c_str() );
217 PointerType * ptrType = new PointerType( Type::Qualifiers(), baseType->clone() );
218 delete arg->get_result();
219 arg->set_result( ptrType );
220 arg = mkDeref( arg );
221 }
222 }
223 ++i;
224 }
225 }
226 return appExpr;
227 }
228
229 // idea: &&&E: get outer &, inner &
230 // at inner &, record depth D of reference type
231 // at outer &, add D derefs.
232 void AddrRef::premutate( Expression * ) {
233 GuardValue( current );
234 GuardValue( first );
235 current = false;
236 first = true;
237 }
238
239 void AddrRef::premutate( AddressExpr * ) {
240 GuardValue( current );
241 GuardValue( first );
242 current = first;
243 first = false;
244 if ( current ) {
245 GuardValue( refDepth );
246 refDepth = 0;
247 }
248 }
249
250 Expression * AddrRef::postmutate( AddressExpr * addrExpr ) {
251 if ( refDepth == 0 ) {
252 if ( ! isIntrinsicReference( addrExpr->get_arg() ) ) {
253 // try to avoid ?[?]
254 refDepth = addrExpr->get_arg()->get_result()->referenceDepth();
255 }
256 }
257 if ( current ) {
258 Expression * ret = addrExpr;
259 while ( refDepth ) {
260 ret = mkDeref( ret );
261 refDepth--;
262 }
263 return ret;
264 }
265 return addrExpr;
266 }
267
268 Expression * ReferenceConversions::postmutate( AddressExpr * addrExpr ) {
269 // Inner expression may have been lvalue to reference conversion, which becomes an address expression.
270 // In this case, remove the outer address expression and return the argument.
271 // TODO: It's possible that this might catch too much and require a more sophisticated check.
272 return addrExpr;
273 }
274
275 Expression * ReferenceConversions::postmutate( CastExpr * castExpr ) {
276 // xxx - is it possible to convert directly between reference types with a different base? E.g.,
277 // int x;
278 // (double&)x;
279 // At the moment, I am working off of the assumption that this is illegal, thus the cast becomes redundant
280 // after this pass, so trash the cast altogether. If that changes, care must be taken to insert the correct
281 // pointer casts in the right places.
282
283 // conversion to reference type
284 if ( ReferenceType * refType = dynamic_cast< ReferenceType * >( castExpr->get_result() ) ) {
285 (void)refType;
286 if ( ReferenceType * otherRef = dynamic_cast< ReferenceType * >( castExpr->get_arg()->get_result() ) ) {
287 // nothing to do if casting from reference to reference.
288 (void)otherRef;
289 PRINT( std::cerr << "convert reference to reference -- nop" << std::endl; )
290 if ( isIntrinsicReference( castExpr->get_arg() ) ) {
291 Expression * callExpr = castExpr->get_arg();
292 PRINT(
293 std::cerr << "but arg is deref -- &" << std::endl;
294 std::cerr << callExpr << std::endl;
295 )
296 callExpr = new AddressExpr( callExpr ); // this doesn't work properly for multiple casts
297 delete callExpr->get_result();
298 callExpr->set_result( refType->clone() );
299 // move environment out to new top-level
300 callExpr->set_env( castExpr->get_env() );
301 castExpr->set_arg( nullptr );
302 castExpr->set_env( nullptr );
303 delete castExpr;
304 return callExpr;
305 }
306 int depth1 = refType->referenceDepth();
307 int depth2 = otherRef->referenceDepth();
308 int diff = depth1-depth2;
309 if ( diff == 0 ) {
310 // conversion between references of the same depth
311 assertf( depth1 == depth2, "non-intrinsic reference with cast of reference to reference not yet supported: %d %d %s", depth1, depth2, toString( castExpr ).c_str() );
312 PRINT( std::cerr << castExpr << std::endl; )
313 return castExpr;
314 } else if ( diff < 0 ) {
315 // conversion from reference to reference with less depth (e.g. int && -> int &): add dereferences
316 Expression * ret = castExpr->arg;
317 for ( int i = 0; i < diff; ++i ) {
318 ret = mkDeref( ret );
319 }
320 ret->env = castExpr->env;
321 delete ret->result;
322 ret->result = castExpr->result;
323 ret->result->set_lvalue( true ); // ensure result is lvalue
324 castExpr->env = nullptr;
325 castExpr->arg = nullptr;
326 castExpr->result = nullptr;
327 delete castExpr;
328 return ret;
329 } else if ( diff > 0 ) {
330 // conversion from reference to reference with more depth (e.g. int & -> int &&): add address-of
331 Expression * ret = castExpr->arg;
332 for ( int i = 0; i < diff; ++i ) {
333 ret = new AddressExpr( ret );
334 }
335 ret->env = castExpr->env;
336 delete ret->result;
337 ret->result = castExpr->result;
338 castExpr->env = nullptr;
339 castExpr->arg = nullptr;
340 castExpr->result = nullptr;
341 delete castExpr;
342 return ret;
343 }
344
345 assertf( depth1 == depth2, "non-intrinsic reference with cast of reference to reference not yet supported: %d %d %s", depth1, depth2, toString( castExpr ).c_str() );
346 PRINT( std::cerr << castExpr << std::endl; )
347 return castExpr;
348 } else if ( castExpr->arg->result->get_lvalue() ) {
349 // conversion from lvalue to reference
350 // xxx - keep cast, but turn into pointer cast??
351 // xxx - memory
352 PRINT(
353 std::cerr << "convert lvalue to reference -- &" << std::endl;
354 std::cerr << castExpr->arg << std::endl;
355 )
356 AddressExpr * ret = new AddressExpr( castExpr->arg );
357 if ( refType->base->get_qualifiers() != castExpr->arg->result->get_qualifiers() ) {
358 // must keep cast if cast-to type is different from the actual type
359 castExpr->arg = ret;
360 return castExpr;
361 }
362 ret->env = castExpr->env;
363 delete ret->result;
364 ret->result = castExpr->result;
365 castExpr->env = nullptr;
366 castExpr->arg = nullptr;
367 castExpr->result = nullptr;
368 delete castExpr;
369 return ret;
370 } else {
371 // rvalue to reference conversion -- introduce temporary
372 }
373 assertf( false, "Only conversions to reference from lvalue are currently supported: %s", toString( castExpr ).c_str() );
374 } else if ( ReferenceType * refType = dynamic_cast< ReferenceType * >( castExpr->arg->result ) ) {
375 (void)refType;
376 // conversion from reference to rvalue
377 PRINT(
378 std::cerr << "convert reference to rvalue -- *" << std::endl;
379 std::cerr << "was = " << castExpr << std::endl;
380 )
381 Expression * ret = castExpr->arg;
382 TypeSubstitution * env = castExpr->env;
383 castExpr->set_env( nullptr );
384 if ( ! isIntrinsicReference( ret ) ) {
385 // dereference if not already dereferenced
386 ret = mkDeref( ret );
387 }
388 if ( ResolvExpr::typesCompatibleIgnoreQualifiers( castExpr->result, castExpr->arg->result->stripReferences(), SymTab::Indexer() ) ) {
389 // can remove cast if types are compatible, changing expression type to value type
390 ret->result = castExpr->result->clone();
391 ret->result->set_lvalue( true ); // ensure result is lvalue
392 castExpr->arg = nullptr;
393 delete castExpr;
394 } else {
395 // must keep cast if types are different
396 castExpr->arg = ret;
397 ret = castExpr;
398 }
399 ret->set_env( env );
400 PRINT( std::cerr << "now: " << ret << std::endl; )
401 return ret;
402 }
403 return castExpr;
404 }
405
406 Type * ReferenceTypeElimination::postmutate( ReferenceType * refType ) {
407 Type * base = refType->get_base();
408 Type::Qualifiers qualifiers = refType->get_qualifiers();
409 refType->set_base( nullptr );
410 delete refType;
411 return new PointerType( qualifiers, base );
412 }
413
414 template<typename Func>
415 Expression * GeneralizedLvalue::applyTransformation( Expression * expr, Expression * arg, Func mkExpr ) {
416 if ( CommaExpr * commaExpr = dynamic_cast< CommaExpr * >( arg ) ) {
417 Expression * arg1 = commaExpr->get_arg1()->clone();
418 Expression * arg2 = commaExpr->get_arg2()->clone();
419 Expression * ret = new CommaExpr( arg1, mkExpr( arg2 )->acceptMutator( *visitor ) );
420 ret->set_env( expr->get_env() );
421 expr->set_env( nullptr );
422 delete expr;
423 return ret;
424 } else if ( ConditionalExpr * condExpr = dynamic_cast< ConditionalExpr * >( arg ) ) {
425 Expression * arg1 = condExpr->get_arg1()->clone();
426 Expression * arg2 = condExpr->get_arg2()->clone();
427 Expression * arg3 = condExpr->get_arg3()->clone();
428 ConditionalExpr * ret = new ConditionalExpr( arg1, mkExpr( arg2 )->acceptMutator( *visitor ), mkExpr( arg3 )->acceptMutator( *visitor ) );
429 ret->set_env( expr->get_env() );
430 expr->set_env( nullptr );
431 delete expr;
432
433 // conditional expr type may not be either of the argument types, need to unify
434 using namespace ResolvExpr;
435 Type* commonType = nullptr;
436 TypeEnvironment newEnv;
437 AssertionSet needAssertions, haveAssertions;
438 OpenVarSet openVars;
439 unify( ret->get_arg2()->get_result(), ret->get_arg3()->get_result(), newEnv, needAssertions, haveAssertions, openVars, SymTab::Indexer(), commonType );
440 ret->set_result( commonType ? commonType : ret->get_arg2()->get_result()->clone() );
441 return ret;
442 }
443 return expr;
444 }
445
446 Expression * GeneralizedLvalue::postmutate( MemberExpr * memExpr ) {
447 return applyTransformation( memExpr, memExpr->get_aggregate(), [=]( Expression * aggr ) { return new MemberExpr( memExpr->get_member(), aggr ); } );
448 }
449
450 Expression * GeneralizedLvalue::postmutate( AddressExpr * addrExpr ) {
451 return applyTransformation( addrExpr, addrExpr->get_arg(), []( Expression * arg ) { return new AddressExpr( arg ); } );
452 }
453
454 Expression * CollapseAddrDeref::postmutate( AddressExpr * addrExpr ) {
455 Expression * arg = addrExpr->get_arg();
456 if ( isIntrinsicReference( arg ) ) {
457 std::string fname = InitTweak::getFunctionName( arg );
458 if ( fname == "*?" ) {
459 Expression *& arg0 = InitTweak::getCallArg( arg, 0 );
460 Expression * ret = arg0;
461 ret->set_env( addrExpr->get_env() );
462 arg0 = nullptr;
463 addrExpr->set_env( nullptr );
464 delete addrExpr;
465 return ret;
466 }
467 }
468 return addrExpr;
469 }
470
471 Expression * CollapseAddrDeref::postmutate( ApplicationExpr * appExpr ) {
472 if ( isIntrinsicReference( appExpr ) ) {
473 std::string fname = InitTweak::getFunctionName( appExpr );
474 if ( fname == "*?" ) {
475 Expression * arg = InitTweak::getCallArg( appExpr, 0 );
476 // xxx - this isn't right, because it can remove casts that should be there...
477 // while ( CastExpr * castExpr = dynamic_cast< CastExpr * >( arg ) ) {
478 // arg = castExpr->get_arg();
479 // }
480 if ( AddressExpr * addrExpr = dynamic_cast< AddressExpr * >( arg ) ) {
481 Expression * ret = addrExpr->get_arg();
482 ret->set_env( appExpr->get_env() );
483 addrExpr->set_arg( nullptr );
484 appExpr->set_env( nullptr );
485 delete appExpr;
486 return ret;
487 }
488 }
489 }
490 return appExpr;
491 }
492 } // namespace
493} // namespace GenPoly
494
495// Local Variables: //
496// tab-width: 4 //
497// mode: c++ //
498// compile-command: "make install" //
499// End: //
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