source: src/GenPoly/Lvalue.cc@ fc56cdbf

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 fc56cdbf was fc56cdbf, checked in by Rob Schluntz <rschlunt@…>, 8 years ago

Handle conversions between reference types of different depths
  • Property mode set to 100644
File size: 18.4 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>
17
18#include "Lvalue.h"
19
20#include "GenPoly.h"
21
22#include "SynTree/Declaration.h"
23#include "SynTree/Type.h"
24#include "SynTree/Expression.h"
25#include "SynTree/Statement.h"
26#include "SynTree/Visitor.h"
27#include "SynTree/Mutator.h"
28#include "SymTab/Indexer.h"
29#include "SymTab/Autogen.h"
30
31#include "ResolvExpr/Resolver.h"
32#include "ResolvExpr/TypeEnvironment.h"
33#include "ResolvExpr/typeops.h"
34#include "ResolvExpr/Unify.h"
35
36#include "Common/UniqueName.h"
37#include "Common/utility.h"
38#include "Common/PassVisitor.h"
39
40#include "InitTweak/InitTweak.h"
41
42#if 0
43#define PRINT(x) x
44#else
45#define PRINT(x)
46#endif
47
48namespace GenPoly {
49 namespace {
50 // TODO: fold this into the general createDeref function??
51 Expression * mkDeref( Expression * arg ) {
52 if ( SymTab::dereferenceOperator ) {
53 VariableExpr * deref = new VariableExpr( SymTab::dereferenceOperator );
54 deref->set_result( new PointerType( Type::Qualifiers(), deref->get_result() ) );
55 Type * base = InitTweak::getPointerBase( arg->get_result() );
56 assertf( base, "expected pointer type in dereference (type was %s)", toString( arg->get_result() ).c_str() );
57 ApplicationExpr * ret = new ApplicationExpr( deref, { arg } );
58 delete ret->get_result();
59 ret->set_result( base->clone() );
60 ret->get_result()->set_lvalue( true );
61 return ret;
62 } else {
63 return UntypedExpr::createDeref( arg );
64 }
65 }
66
67 struct ReferenceConversions final {
68 Expression * postmutate( CastExpr * castExpr );
69 Expression * postmutate( AddressExpr * addrExpr );
70 };
71
72 /// Intrinsic functions that take reference parameters don't REALLY take reference parameters -- their reference arguments must always be implicitly dereferenced.
73 struct FixIntrinsicArgs final {
74 Expression * postmutate( ApplicationExpr * appExpr );
75 };
76
77 struct FixIntrinsicResult final {
78 Expression * postmutate( ApplicationExpr * appExpr );
79 };
80
81 /// Replace reference types with pointer types
82 struct ReferenceTypeElimination final {
83 Type * postmutate( ReferenceType * refType );
84 };
85
86 /// GCC-like Generalized Lvalues (which have since been removed from GCC)
87 /// https://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Lvalues.html#Lvalues
88 /// Replaces &(a,b) with (a, &b), &(a ? b : c) with (a ? &b : &c)
89 struct GeneralizedLvalue final : public WithVisitorRef<GeneralizedLvalue> {
90 Expression * postmutate( AddressExpr * addressExpr );
91 Expression * postmutate( MemberExpr * memExpr );
92
93 template<typename Func>
94 Expression * applyTransformation( Expression * expr, Expression * arg, Func mkExpr );
95 };
96
97 /// Removes redundant &*/*& pattern that this pass can generate
98 struct CollapseAddrDeref final {
99 Expression * postmutate( AddressExpr * addressExpr );
100 Expression * postmutate( ApplicationExpr * appExpr );
101 };
102
103 struct AddrRef final : public WithGuards {
104 void premutate( AddressExpr * addrExpr );
105 Expression * postmutate( AddressExpr * addrExpr );
106 void premutate( Expression * expr );
107
108 bool first = true;
109 bool current = false;
110 int refDepth = 0;
111 };
112 } // namespace
113
114 static bool referencesEliminated = false;
115 // used by UntypedExpr::createDeref to determine whether result type of dereference should be ReferenceType or value type.
116 bool referencesPermissable() {
117 return ! referencesEliminated;
118 }
119
120 void convertLvalue( std::list< Declaration* >& translationUnit ) {
121 PassVisitor<ReferenceConversions> refCvt;
122 PassVisitor<ReferenceTypeElimination> elim;
123 PassVisitor<GeneralizedLvalue> genLval;
124 PassVisitor<FixIntrinsicArgs> fixer;
125 PassVisitor<CollapseAddrDeref> collapser;
126 PassVisitor<AddrRef> addrRef;
127 PassVisitor<FixIntrinsicResult> intrinsicResults;
128 mutateAll( translationUnit, intrinsicResults );
129 mutateAll( translationUnit, addrRef );
130 mutateAll( translationUnit, refCvt );
131 mutateAll( translationUnit, fixer );
132 mutateAll( translationUnit, collapser );
133 mutateAll( translationUnit, genLval );
134 mutateAll( translationUnit, elim ); // last because other passes need reference types to work
135
136 // from this point forward, no other pass should create reference types.
137 referencesEliminated = true;
138 }
139
140 Expression * generalizedLvalue( Expression * expr ) {
141 PassVisitor<GeneralizedLvalue> genLval;
142 return expr->acceptMutator( genLval );
143 }
144
145 namespace {
146 // true for intrinsic function calls that return a reference
147 bool isIntrinsicReference( Expression * expr ) {
148 if ( UntypedExpr * untyped = dynamic_cast< UntypedExpr * >( expr ) ) {
149 std::string fname = InitTweak::getFunctionName( untyped );
150 // known intrinsic-reference prelude functions
151 return fname == "*?" || fname == "?[?]";
152 } else if ( ApplicationExpr * appExpr = dynamic_cast< ApplicationExpr * > ( expr ) ) {
153 if ( DeclarationWithType * func = InitTweak::getFunction( appExpr ) ) {
154 // use type of return variable rather than expr result type, since it may have been changed to a pointer type
155 FunctionType * ftype = GenPoly::getFunctionType( func->get_type() );
156 Type * ret = ftype->get_returnVals().empty() ? nullptr : ftype->get_returnVals().front()->get_type();
157 return func->get_linkage() == LinkageSpec::Intrinsic && dynamic_cast<ReferenceType *>( ret );
158 }
159 }
160 return false;
161 }
162
163 Expression * FixIntrinsicResult::postmutate( ApplicationExpr * appExpr ) {
164 if ( isIntrinsicReference( appExpr ) ) {
165 // eliminate reference types from intrinsic applications - now they return lvalues
166 Type * result = appExpr->get_result();
167 appExpr->set_result( result->stripReferences()->clone() );
168 appExpr->get_result()->set_lvalue( true );
169 Expression * ret = new CastExpr( appExpr, result );
170 ret->set_env( appExpr->get_env() );
171 appExpr->set_env( nullptr );
172 return ret;
173 }
174 return appExpr;
175 }
176
177 Expression * FixIntrinsicArgs::postmutate( ApplicationExpr * appExpr ) {
178 // intrinsic functions don't really take reference-typed parameters, so they require an implicit dereference on their arguments.
179 if ( DeclarationWithType * function = InitTweak::getFunction( appExpr ) ) {
180 FunctionType * ftype = GenPoly::getFunctionType( function->get_type() );
181 assertf( ftype, "Function declaration does not have function type." );
182 // can be of differing lengths only when function is variadic
183 assertf( ftype->get_parameters().size() == appExpr->get_args().size() || ftype->get_isVarArgs(), "ApplicationExpr args do not match formal parameter type." );
184
185
186 unsigned int i = 0;
187 const unsigned int end = ftype->get_parameters().size();
188 for ( auto p : unsafe_group_iterate( appExpr->get_args(), ftype->get_parameters() ) ) {
189 if (i == end) break;
190 Expression *& arg = std::get<0>( p );
191 Type * formal = std::get<1>( p )->get_type();
192 PRINT(
193 std::cerr << "pair<0>: " << arg << std::endl;
194 std::cerr << "pair<1>: " << formal << std::endl;
195 )
196 if ( dynamic_cast<ReferenceType*>( formal ) ) {
197 if ( isIntrinsicReference( arg ) ) { // do not combine conditions, because that changes the meaning of the else if
198 if ( function->get_linkage() != LinkageSpec::Intrinsic ) { // intrinsic functions that turn pointers into references
199 // if argument is dereference or array subscript, the result isn't REALLY a reference, so it's not necessary to fix the argument
200 PRINT(
201 std::cerr << "===is intrinsic arg in non-intrinsic call - adding address" << std::endl;
202 )
203 arg = new AddressExpr( arg );
204 }
205 } else if ( function->get_linkage() == LinkageSpec::Intrinsic ) {
206 // std::cerr << "===adding deref to arg" << std::endl;
207 // if the parameter is a reference, add a dereference to the reference-typed argument.
208 Type * baseType = InitTweak::getPointerBase( arg->get_result() );
209 assertf( baseType, "parameter is reference, arg must be pointer or reference: %s", toString( arg->get_result() ).c_str() );
210 PointerType * ptrType = new PointerType( Type::Qualifiers(), baseType->clone() );
211 delete arg->get_result();
212 arg->set_result( ptrType );
213 arg = mkDeref( arg );
214 }
215 }
216 ++i;
217 }
218 }
219 return appExpr;
220 }
221
222 // idea: &&&E: get outer &, inner &
223 // at inner &, record depth D of reference type
224 // at outer &, add D derefs.
225 void AddrRef::premutate( Expression * expr ) {
226 GuardValue( current );
227 GuardValue( first );
228 current = false;
229 first = true;
230 }
231
232 void AddrRef::premutate( AddressExpr * addrExpr ) {
233 GuardValue( current );
234 GuardValue( first );
235 current = first;
236 first = false;
237 if ( current ) {
238 GuardValue( refDepth );
239 refDepth = 0;
240 }
241 }
242
243 Expression * AddrRef::postmutate( AddressExpr * addrExpr ) {
244 if ( refDepth == 0 ) {
245 if ( ! isIntrinsicReference( addrExpr->get_arg() ) ) {
246 // try to avoid ?[?]
247 refDepth = addrExpr->get_arg()->get_result()->referenceDepth();
248 }
249 }
250 if ( current ) {
251 Expression * ret = addrExpr;
252 while ( refDepth ) {
253 ret = mkDeref( ret );
254 refDepth--;
255 }
256 return ret;
257 }
258 return addrExpr;
259 }
260
261 Expression * ReferenceConversions::postmutate( AddressExpr * addrExpr ) {
262 // Inner expression may have been lvalue to reference conversion, which becomes an address expression.
263 // In this case, remove the outer address expression and return the argument.
264 // TODO: It's possible that this might catch too much and require a more sophisticated check.
265 return addrExpr;
266 }
267
268 Expression * ReferenceConversions::postmutate( CastExpr * castExpr ) {
269 // xxx - is it possible to convert directly between reference types with a different base? E.g.,
270 // int x;
271 // (double&)x;
272 // At the moment, I am working off of the assumption that this is illegal, thus the cast becomes redundant
273 // after this pass, so trash the cast altogether. If that changes, care must be taken to insert the correct
274 // pointer casts in the right places.
275
276 // conversion to reference type
277 if ( ReferenceType * refType = dynamic_cast< ReferenceType * >( castExpr->get_result() ) ) {
278 (void)refType;
279 if ( ReferenceType * otherRef = dynamic_cast< ReferenceType * >( castExpr->get_arg()->get_result() ) ) {
280 // nothing to do if casting from reference to reference.
281 (void)otherRef;
282 PRINT( std::cerr << "convert reference to reference -- nop" << std::endl; )
283 if ( isIntrinsicReference( castExpr->get_arg() ) ) {
284 Expression * callExpr = castExpr->get_arg();
285 PRINT(
286 std::cerr << "but arg is deref -- &" << std::endl;
287 std::cerr << callExpr << std::endl;
288 )
289 callExpr = new AddressExpr( callExpr ); // this doesn't work properly for multiple casts
290 delete callExpr->get_result();
291 callExpr->set_result( refType->clone() );
292 // move environment out to new top-level
293 callExpr->set_env( castExpr->get_env() );
294 castExpr->set_arg( nullptr );
295 castExpr->set_env( nullptr );
296 delete castExpr;
297 return callExpr;
298 }
299 int depth1 = refType->referenceDepth();
300 int depth2 = otherRef->referenceDepth();
301 int diff = depth1-depth2;
302 if ( diff == 0 ) {
303 assertf( depth1 == depth2, "non-intrinsic reference with cast of reference to reference not yet supported: %d %d %s", depth1, depth2, toString( castExpr ).c_str() );
304 PRINT( std::cerr << castExpr << std::endl; )
305 return castExpr;
306 } else if ( diff < 0 ) {
307 Expression * ret = castExpr->get_arg();
308 for ( int i = 0; i < diff; ++i ) {
309 ret = mkDeref( ret );
310 }
311 ret->set_env( castExpr->get_env() );
312 delete ret->get_result();
313 ret->set_result( castExpr->get_result() );
314 castExpr->set_env( nullptr );
315 castExpr->set_arg( nullptr );
316 castExpr->set_result( nullptr );
317 delete castExpr;
318 return ret;
319 } else if ( diff > 0 ) {
320 Expression * ret = castExpr->get_arg();
321 for ( int i = 0; i < diff; ++i ) {
322 ret = new AddressExpr( ret );
323 }
324 ret->set_env( castExpr->get_env() );
325 delete ret->get_result();
326 ret->set_result( castExpr->get_result() );
327 castExpr->set_env( nullptr );
328 castExpr->set_arg( nullptr );
329 castExpr->set_result( nullptr );
330 delete castExpr;
331 return ret;
332 }
333
334 assertf( depth1 == depth2, "non-intrinsic reference with cast of reference to reference not yet supported: %d %d %s", depth1, depth2, toString( castExpr ).c_str() );
335 PRINT( std::cerr << castExpr << std::endl; )
336 return castExpr;
337 } else if ( castExpr->get_arg()->get_result()->get_lvalue() ) {
338 // conversion from lvalue to reference
339 // xxx - keep cast, but turn into pointer cast??
340 // xxx - memory
341 PRINT(
342 std::cerr << "convert lvalue to reference -- &" << std::endl;
343 std::cerr << castExpr->get_arg() << std::endl;
344 )
345 AddressExpr * ret = new AddressExpr( castExpr->get_arg() );
346 if ( refType->get_base()->get_qualifiers() != castExpr->get_arg()->get_result()->get_qualifiers() ) {
347 // must keep cast if cast-to type is different from the actual type
348 castExpr->set_arg( ret );
349 return castExpr;
350 }
351 ret->set_env( castExpr->get_env() );
352 delete ret->get_result();
353 ret->set_result( castExpr->get_result() );
354 castExpr->set_env( nullptr );
355 castExpr->set_arg( nullptr );
356 castExpr->set_result( nullptr );
357 delete castExpr;
358 return ret;
359 } else {
360 // rvalue to reference conversion -- introduce temporary
361 }
362 assertf( false, "Only conversions to reference from lvalue are currently supported: %s", toString( castExpr ).c_str() );
363 } else if ( ReferenceType * refType = dynamic_cast< ReferenceType * >( castExpr->get_arg()->get_result() ) ) {
364 (void)refType;
365 // conversion from reference to rvalue
366 PRINT(
367 std::cerr << "convert reference to rvalue -- *" << std::endl;
368 std::cerr << "was = " << castExpr << std::endl;
369 )
370 Expression * ret = castExpr->get_arg();
371 TypeSubstitution * env = castExpr->get_env();
372 castExpr->set_env( nullptr );
373 if ( ! isIntrinsicReference( ret ) ) {
374 // dereference if not already dereferenced
375 ret = mkDeref( ret );
376 }
377 if ( ResolvExpr::typesCompatibleIgnoreQualifiers( castExpr->get_result(), castExpr->get_arg()->get_result()->stripReferences(), SymTab::Indexer() ) ) {
378 // can remove cast if types are compatible, changing expression type to value type
379 ret->set_result( castExpr->get_result()->clone() );
380 castExpr->set_arg( nullptr );
381 delete castExpr;
382 } else {
383 // must keep cast if types are different
384 castExpr->set_arg( ret );
385 ret = castExpr;
386 }
387 ret->set_env( env );
388 PRINT( std::cerr << "now: " << ret << std::endl; )
389 return ret;
390 }
391 return castExpr;
392 }
393
394 Type * ReferenceTypeElimination::postmutate( ReferenceType * refType ) {
395 Type * base = refType->get_base();
396 Type::Qualifiers qualifiers = refType->get_qualifiers();
397 refType->set_base( nullptr );
398 delete refType;
399 return new PointerType( qualifiers, base );
400 }
401
402 template<typename Func>
403 Expression * GeneralizedLvalue::applyTransformation( Expression * expr, Expression * arg, Func mkExpr ) {
404 if ( CommaExpr * commaExpr = dynamic_cast< CommaExpr * >( arg ) ) {
405 Expression * arg1 = commaExpr->get_arg1()->clone();
406 Expression * arg2 = commaExpr->get_arg2()->clone();
407 Expression * ret = new CommaExpr( arg1, mkExpr( arg2 )->acceptMutator( *visitor ) );
408 ret->set_env( expr->get_env() );
409 expr->set_env( nullptr );
410 delete expr;
411 return ret;
412 } else if ( ConditionalExpr * condExpr = dynamic_cast< ConditionalExpr * >( arg ) ) {
413 Expression * arg1 = condExpr->get_arg1()->clone();
414 Expression * arg2 = condExpr->get_arg2()->clone();
415 Expression * arg3 = condExpr->get_arg3()->clone();
416 ConditionalExpr * ret = new ConditionalExpr( arg1, mkExpr( arg2 )->acceptMutator( *visitor ), mkExpr( arg3 )->acceptMutator( *visitor ) );
417 ret->set_env( expr->get_env() );
418 expr->set_env( nullptr );
419 delete expr;
420
421 // conditional expr type may not be either of the argument types, need to unify
422 using namespace ResolvExpr;
423 Type* commonType = nullptr;
424 TypeEnvironment newEnv;
425 AssertionSet needAssertions, haveAssertions;
426 OpenVarSet openVars;
427 unify( ret->get_arg2()->get_result(), ret->get_arg3()->get_result(), newEnv, needAssertions, haveAssertions, openVars, SymTab::Indexer(), commonType );
428 ret->set_result( commonType ? commonType : ret->get_arg2()->get_result()->clone() );
429 return ret;
430 }
431 return expr;
432 }
433
434 Expression * GeneralizedLvalue::postmutate( MemberExpr * memExpr ) {
435 return applyTransformation( memExpr, memExpr->get_aggregate(), [=]( Expression * aggr ) { return new MemberExpr( memExpr->get_member(), aggr ); } );
436 }
437
438 Expression * GeneralizedLvalue::postmutate( AddressExpr * addrExpr ) {
439 return applyTransformation( addrExpr, addrExpr->get_arg(), []( Expression * arg ) { return new AddressExpr( arg ); } );
440 }
441
442 Expression * CollapseAddrDeref::postmutate( AddressExpr * addrExpr ) {
443 Expression * arg = addrExpr->get_arg();
444 if ( isIntrinsicReference( arg ) ) {
445 std::string fname = InitTweak::getFunctionName( arg );
446 if ( fname == "*?" ) {
447 Expression *& arg0 = InitTweak::getCallArg( arg, 0 );
448 Expression * ret = arg0;
449 ret->set_env( addrExpr->get_env() );
450 arg0 = nullptr;
451 addrExpr->set_env( nullptr );
452 delete addrExpr;
453 return ret;
454 }
455 }
456 return addrExpr;
457 }
458
459 Expression * CollapseAddrDeref::postmutate( ApplicationExpr * appExpr ) {
460 if ( isIntrinsicReference( appExpr ) ) {
461 std::string fname = InitTweak::getFunctionName( appExpr );
462 if ( fname == "*?" ) {
463 Expression * arg = InitTweak::getCallArg( appExpr, 0 );
464 // xxx - this isn't right, because it can remove casts that should be there...
465 // while ( CastExpr * castExpr = dynamic_cast< CastExpr * >( arg ) ) {
466 // arg = castExpr->get_arg();
467 // }
468 if ( AddressExpr * addrExpr = dynamic_cast< AddressExpr * >( arg ) ) {
469 Expression * ret = addrExpr->get_arg();
470 ret->set_env( appExpr->get_env() );
471 addrExpr->set_arg( nullptr );
472 appExpr->set_env( nullptr );
473 delete appExpr;
474 return ret;
475 }
476 }
477 }
478 return appExpr;
479 }
480 } // namespace
481} // namespace GenPoly
482
483// Local Variables: //
484// tab-width: 4 //
485// mode: c++ //
486// compile-command: "make install" //
487// End: //
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