source: src/GenPoly/Lvalue.cc@ 8135d4c

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 8135d4c was 8135d4c, checked in by Rob Schluntz <rschlunt@…>, 8 years ago

Merge branch 'master' into references
  • Property mode set to 100644
File size: 18.9 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 safe_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->set_result( new PointerType( Type::Qualifiers(), deref->get_result() ) );
50 Type * base = InitTweak::getPointerBase( arg->get_result() );
51 assertf( base, "expected pointer type in dereference (type was %s)", toString( arg->get_result() ).c_str() );
52 ApplicationExpr * ret = new ApplicationExpr( deref, { arg } );
53 delete ret->get_result();
54 ret->set_result( base->clone() );
55 ret->get_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 {
73 Expression * postmutate( ApplicationExpr * appExpr );
74 };
75
76 /// Replace reference types with pointer types
77 struct ReferenceTypeElimination final {
78 Type * postmutate( ReferenceType * refType );
79 };
80
81 /// GCC-like Generalized Lvalues (which have since been removed from GCC)
82 /// https://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Lvalues.html#Lvalues
83 /// Replaces &(a,b) with (a, &b), &(a ? b : c) with (a ? &b : &c)
84 struct GeneralizedLvalue final : public WithVisitorRef<GeneralizedLvalue> {
85 Expression * postmutate( AddressExpr * addressExpr );
86 Expression * postmutate( MemberExpr * memExpr );
87
88 template<typename Func>
89 Expression * applyTransformation( Expression * expr, Expression * arg, Func mkExpr );
90 };
91
92 /// Removes redundant &*/*& pattern that this pass can generate
93 struct CollapseAddrDeref final {
94 Expression * postmutate( AddressExpr * addressExpr );
95 Expression * postmutate( ApplicationExpr * appExpr );
96 };
97
98 struct AddrRef final : public WithGuards {
99 void premutate( AddressExpr * addrExpr );
100 Expression * postmutate( AddressExpr * addrExpr );
101 void premutate( Expression * expr );
102
103 bool first = true;
104 bool current = false;
105 int refDepth = 0;
106 };
107 } // namespace
108
109 static bool referencesEliminated = false;
110 // used by UntypedExpr::createDeref to determine whether result type of dereference should be ReferenceType or value type.
111 bool referencesPermissable() {
112 return ! referencesEliminated;
113 }
114
115 void convertLvalue( std::list< Declaration* >& translationUnit ) {
116 PassVisitor<ReferenceConversions> refCvt;
117 PassVisitor<ReferenceTypeElimination> elim;
118 PassVisitor<GeneralizedLvalue> genLval;
119 PassVisitor<FixIntrinsicArgs> fixer;
120 PassVisitor<CollapseAddrDeref> collapser;
121 PassVisitor<AddrRef> addrRef;
122 PassVisitor<FixIntrinsicResult> intrinsicResults;
123 mutateAll( translationUnit, intrinsicResults );
124 mutateAll( translationUnit, addrRef );
125 mutateAll( translationUnit, refCvt );
126 mutateAll( translationUnit, fixer );
127 mutateAll( translationUnit, collapser );
128 mutateAll( translationUnit, genLval );
129 mutateAll( translationUnit, elim ); // last because other passes need reference types to work
130
131 // from this point forward, no other pass should create reference types.
132 referencesEliminated = true;
133 }
134
135 Expression * generalizedLvalue( Expression * expr ) {
136 PassVisitor<GeneralizedLvalue> genLval;
137 return expr->acceptMutator( genLval );
138 }
139
140 namespace {
141 // true for intrinsic function calls that return a reference
142 bool isIntrinsicReference( Expression * expr ) {
143 if ( UntypedExpr * untyped = dynamic_cast< UntypedExpr * >( expr ) ) {
144 std::string fname = InitTweak::getFunctionName( untyped );
145 // known intrinsic-reference prelude functions
146 return fname == "*?" || fname == "?[?]";
147 } else if ( ApplicationExpr * appExpr = dynamic_cast< ApplicationExpr * > ( expr ) ) {
148 if ( DeclarationWithType * func = InitTweak::getFunction( appExpr ) ) {
149 // use type of return variable rather than expr result type, since it may have been changed to a pointer type
150 FunctionType * ftype = GenPoly::getFunctionType( func->get_type() );
151 Type * ret = ftype->get_returnVals().empty() ? nullptr : ftype->get_returnVals().front()->get_type();
152 return func->get_linkage() == LinkageSpec::Intrinsic && dynamic_cast<ReferenceType *>( ret );
153 }
154 }
155 return false;
156 }
157
158 Expression * FixIntrinsicResult::postmutate( ApplicationExpr * appExpr ) {
159 if ( isIntrinsicReference( appExpr ) ) {
160 // eliminate reference types from intrinsic applications - now they return lvalues
161 Type * result = appExpr->get_result();
162 appExpr->set_result( result->stripReferences()->clone() );
163 appExpr->get_result()->set_lvalue( true );
164 Expression * ret = new CastExpr( appExpr, result );
165 ret->set_env( appExpr->get_env() );
166 appExpr->set_env( nullptr );
167 return ret;
168 }
169 return appExpr;
170 }
171
172 Expression * FixIntrinsicArgs::postmutate( ApplicationExpr * appExpr ) {
173 // intrinsic functions don't really take reference-typed parameters, so they require an implicit dereference on their arguments.
174 if ( DeclarationWithType * function = InitTweak::getFunction( appExpr ) ) {
175 FunctionType * ftype = GenPoly::getFunctionType( function->get_type() );
176 assertf( ftype, "Function declaration does not have function type." );
177 // can be of differing lengths only when function is variadic
178 assertf( ftype->get_parameters().size() == appExpr->get_args().size() || ftype->get_isVarArgs(), "ApplicationExpr args do not match formal parameter type." );
179
180
181 unsigned int i = 0;
182 const unsigned int end = ftype->get_parameters().size();
183 for ( auto p : unsafe_group_iterate( appExpr->get_args(), ftype->get_parameters() ) ) {
184 if (i == end) break;
185 Expression *& arg = std::get<0>( p );
186 Type * formal = std::get<1>( p )->get_type();
187 PRINT(
188 std::cerr << "pair<0>: " << arg << std::endl;
189 std::cerr << "pair<1>: " << formal << std::endl;
190 )
191 if ( dynamic_cast<ReferenceType*>( formal ) ) {
192 if ( isIntrinsicReference( arg ) ) { // do not combine conditions, because that changes the meaning of the else if
193 if ( function->get_linkage() != LinkageSpec::Intrinsic ) { // intrinsic functions that turn pointers into references
194 // if argument is dereference or array subscript, the result isn't REALLY a reference, so it's not necessary to fix the argument
195 PRINT(
196 std::cerr << "===is intrinsic arg in non-intrinsic call - adding address" << std::endl;
197 )
198 arg = new AddressExpr( arg );
199 }
200 } else if ( function->get_linkage() == LinkageSpec::Intrinsic ) {
201 // std::cerr << "===adding deref to arg" << std::endl;
202 // if the parameter is a reference, add a dereference to the reference-typed argument.
203 Type * baseType = InitTweak::getPointerBase( arg->get_result() );
204 assertf( baseType, "parameter is reference, arg must be pointer or reference: %s", toString( arg->get_result() ).c_str() );
205 PointerType * ptrType = new PointerType( Type::Qualifiers(), baseType->clone() );
206 delete arg->get_result();
207 arg->set_result( ptrType );
208 arg = mkDeref( arg );
209 }
210 }
211 ++i;
212 }
213 }
214 return appExpr;
215 }
216
217 // idea: &&&E: get outer &, inner &
218 // at inner &, record depth D of reference type
219 // at outer &, add D derefs.
220 void AddrRef::premutate( Expression * ) {
221 GuardValue( current );
222 GuardValue( first );
223 current = false;
224 first = true;
225 }
226
227 void AddrRef::premutate( AddressExpr * ) {
228 GuardValue( current );
229 GuardValue( first );
230 current = first;
231 first = false;
232 if ( current ) {
233 GuardValue( refDepth );
234 refDepth = 0;
235 }
236 }
237
238 Expression * AddrRef::postmutate( AddressExpr * addrExpr ) {
239 if ( refDepth == 0 ) {
240 if ( ! isIntrinsicReference( addrExpr->get_arg() ) ) {
241 // try to avoid ?[?]
242 refDepth = addrExpr->get_arg()->get_result()->referenceDepth();
243 }
244 }
245 if ( current ) {
246 Expression * ret = addrExpr;
247 while ( refDepth ) {
248 ret = mkDeref( ret );
249 refDepth--;
250 }
251 return ret;
252 }
253 return addrExpr;
254 }
255
256 Expression * ReferenceConversions::postmutate( AddressExpr * addrExpr ) {
257 // Inner expression may have been lvalue to reference conversion, which becomes an address expression.
258 // In this case, remove the outer address expression and return the argument.
259 // TODO: It's possible that this might catch too much and require a more sophisticated check.
260 return addrExpr;
261 }
262
263 Expression * ReferenceConversions::postmutate( CastExpr * castExpr ) {
264 // xxx - is it possible to convert directly between reference types with a different base? E.g.,
265 // int x;
266 // (double&)x;
267 // At the moment, I am working off of the assumption that this is illegal, thus the cast becomes redundant
268 // after this pass, so trash the cast altogether. If that changes, care must be taken to insert the correct
269 // pointer casts in the right places.
270
271 // conversion to reference type
272 if ( ReferenceType * refType = dynamic_cast< ReferenceType * >( castExpr->get_result() ) ) {
273 (void)refType;
274 if ( ReferenceType * otherRef = dynamic_cast< ReferenceType * >( castExpr->get_arg()->get_result() ) ) {
275 // nothing to do if casting from reference to reference.
276 (void)otherRef;
277 PRINT( std::cerr << "convert reference to reference -- nop" << std::endl; )
278 if ( isIntrinsicReference( castExpr->get_arg() ) ) {
279 Expression * callExpr = castExpr->get_arg();
280 PRINT(
281 std::cerr << "but arg is deref -- &" << std::endl;
282 std::cerr << callExpr << std::endl;
283 )
284 callExpr = new AddressExpr( callExpr ); // this doesn't work properly for multiple casts
285 delete callExpr->get_result();
286 callExpr->set_result( refType->clone() );
287 // move environment out to new top-level
288 callExpr->set_env( castExpr->get_env() );
289 castExpr->set_arg( nullptr );
290 castExpr->set_env( nullptr );
291 delete castExpr;
292 return callExpr;
293 }
294 int depth1 = refType->referenceDepth();
295 int depth2 = otherRef->referenceDepth();
296 int diff = depth1-depth2;
297 if ( diff == 0 ) {
298 assertf( depth1 == depth2, "non-intrinsic reference with cast of reference to reference not yet supported: %d %d %s", depth1, depth2, toString( castExpr ).c_str() );
299 PRINT( std::cerr << castExpr << std::endl; )
300 return castExpr;
301 } else if ( diff < 0 ) {
302 Expression * ret = castExpr->get_arg();
303 for ( int i = 0; i < diff; ++i ) {
304 ret = mkDeref( ret );
305 }
306 ret->set_env( castExpr->get_env() );
307 delete ret->get_result();
308 ret->set_result( castExpr->get_result() );
309 castExpr->set_env( nullptr );
310 castExpr->set_arg( nullptr );
311 castExpr->set_result( nullptr );
312 delete castExpr;
313 return ret;
314 } else if ( diff > 0 ) {
315 Expression * ret = castExpr->get_arg();
316 for ( int i = 0; i < diff; ++i ) {
317 ret = new AddressExpr( ret );
318 }
319 ret->set_env( castExpr->get_env() );
320 delete ret->get_result();
321 ret->set_result( castExpr->get_result() );
322 castExpr->set_env( nullptr );
323 castExpr->set_arg( nullptr );
324 castExpr->set_result( nullptr );
325 delete castExpr;
326 return ret;
327 }
328
329 assertf( depth1 == depth2, "non-intrinsic reference with cast of reference to reference not yet supported: %d %d %s", depth1, depth2, toString( castExpr ).c_str() );
330 PRINT( std::cerr << castExpr << std::endl; )
331 return castExpr;
332 } else if ( castExpr->get_arg()->get_result()->get_lvalue() ) {
333 // conversion from lvalue to reference
334 // xxx - keep cast, but turn into pointer cast??
335 // xxx - memory
336 PRINT(
337 std::cerr << "convert lvalue to reference -- &" << std::endl;
338 std::cerr << castExpr->get_arg() << std::endl;
339 )
340 AddressExpr * ret = new AddressExpr( castExpr->get_arg() );
341 if ( refType->get_base()->get_qualifiers() != castExpr->get_arg()->get_result()->get_qualifiers() ) {
342 // must keep cast if cast-to type is different from the actual type
343 castExpr->set_arg( ret );
344 return castExpr;
345 }
346 ret->set_env( castExpr->get_env() );
347 delete ret->get_result();
348 ret->set_result( castExpr->get_result() );
349 castExpr->set_env( nullptr );
350 castExpr->set_arg( nullptr );
351 castExpr->set_result( nullptr );
352 delete castExpr;
353 return ret;
354 } else {
355 // rvalue to reference conversion -- introduce temporary
356 }
357 assertf( false, "Only conversions to reference from lvalue are currently supported: %s", toString( castExpr ).c_str() );
358 } else if ( ReferenceType * refType = dynamic_cast< ReferenceType * >( castExpr->get_arg()->get_result() ) ) {
359 (void)refType;
360 // conversion from reference to rvalue
361 PRINT(
362 std::cerr << "convert reference to rvalue -- *" << std::endl;
363 std::cerr << "was = " << castExpr << std::endl;
364 )
365 Expression * ret = castExpr->get_arg();
366 TypeSubstitution * env = castExpr->get_env();
367 castExpr->set_env( nullptr );
368 if ( ! isIntrinsicReference( ret ) ) {
369 // dereference if not already dereferenced
370 ret = mkDeref( ret );
371 }
372 if ( ResolvExpr::typesCompatibleIgnoreQualifiers( castExpr->get_result(), castExpr->get_arg()->get_result()->stripReferences(), SymTab::Indexer() ) ) {
373 // can remove cast if types are compatible, changing expression type to value type
374 ret->set_result( castExpr->get_result()->clone() );
375 castExpr->set_arg( nullptr );
376 delete castExpr;
377 } else {
378 // must keep cast if types are different
379 castExpr->set_arg( ret );
380 ret = castExpr;
381 }
382 ret->set_env( env );
383 PRINT( std::cerr << "now: " << ret << std::endl; )
384 return ret;
385 }
386 return castExpr;
387 }
388
389 Type * ReferenceTypeElimination::postmutate( ReferenceType * refType ) {
390 Type * base = refType->get_base();
391 Type::Qualifiers qualifiers = refType->get_qualifiers();
392 refType->set_base( nullptr );
393 delete refType;
394 return new PointerType( qualifiers, base );
395 }
396
397 template<typename Func>
398 Expression * GeneralizedLvalue::applyTransformation( Expression * expr, Expression * arg, Func mkExpr ) {
399 if ( CommaExpr * commaExpr = dynamic_cast< CommaExpr * >( arg ) ) {
400 Expression * arg1 = commaExpr->get_arg1()->clone();
401 Expression * arg2 = commaExpr->get_arg2()->clone();
402 Expression * ret = new CommaExpr( arg1, mkExpr( arg2 )->acceptMutator( *visitor ) );
403 ret->set_env( expr->get_env() );
404 expr->set_env( nullptr );
405 delete expr;
406 return ret;
407 } else if ( ConditionalExpr * condExpr = dynamic_cast< ConditionalExpr * >( arg ) ) {
408 Expression * arg1 = condExpr->get_arg1()->clone();
409 Expression * arg2 = condExpr->get_arg2()->clone();
410 Expression * arg3 = condExpr->get_arg3()->clone();
411 ConditionalExpr * ret = new ConditionalExpr( arg1, mkExpr( arg2 )->acceptMutator( *visitor ), mkExpr( arg3 )->acceptMutator( *visitor ) );
412 ret->set_env( expr->get_env() );
413 expr->set_env( nullptr );
414 delete expr;
415
416 // conditional expr type may not be either of the argument types, need to unify
417 using namespace ResolvExpr;
418 Type* commonType = nullptr;
419 TypeEnvironment newEnv;
420 AssertionSet needAssertions, haveAssertions;
421 OpenVarSet openVars;
422 unify( ret->get_arg2()->get_result(), ret->get_arg3()->get_result(), newEnv, needAssertions, haveAssertions, openVars, SymTab::Indexer(), commonType );
423 ret->set_result( commonType ? commonType : ret->get_arg2()->get_result()->clone() );
424 return ret;
425 }
426 return expr;
427 }
428
429 Expression * GeneralizedLvalue::postmutate( MemberExpr * memExpr ) {
430 return applyTransformation( memExpr, memExpr->get_aggregate(), [=]( Expression * aggr ) { return new MemberExpr( memExpr->get_member(), aggr ); } );
431 }
432
433 Expression * GeneralizedLvalue::postmutate( AddressExpr * addrExpr ) {
434 return applyTransformation( addrExpr, addrExpr->get_arg(), []( Expression * arg ) { return new AddressExpr( arg ); } );
435 }
436
437 Expression * CollapseAddrDeref::postmutate( AddressExpr * addrExpr ) {
438 Expression * arg = addrExpr->get_arg();
439 if ( isIntrinsicReference( arg ) ) {
440 std::string fname = InitTweak::getFunctionName( arg );
441 if ( fname == "*?" ) {
442 Expression *& arg0 = InitTweak::getCallArg( arg, 0 );
443 Expression * ret = arg0;
444 ret->set_env( addrExpr->get_env() );
445 arg0 = nullptr;
446 addrExpr->set_env( nullptr );
447 delete addrExpr;
448 return ret;
449 }
450 }
451 return addrExpr;
452 }
453
454 Expression * CollapseAddrDeref::postmutate( ApplicationExpr * appExpr ) {
455 if ( isIntrinsicReference( appExpr ) ) {
456 std::string fname = InitTweak::getFunctionName( appExpr );
457 if ( fname == "*?" ) {
458 Expression * arg = InitTweak::getCallArg( appExpr, 0 );
459 // xxx - this isn't right, because it can remove casts that should be there...
460 // while ( CastExpr * castExpr = dynamic_cast< CastExpr * >( arg ) ) {
461 // arg = castExpr->get_arg();
462 // }
463 if ( AddressExpr * addrExpr = dynamic_cast< AddressExpr * >( arg ) ) {
464 Expression * ret = addrExpr->get_arg();
465 ret->set_env( appExpr->get_env() );
466 addrExpr->set_arg( nullptr );
467 appExpr->set_env( nullptr );
468 delete appExpr;
469 return ret;
470 }
471 }
472 }
473 return appExpr;
474 }
475 } // namespace
476} // namespace GenPoly
477
478// Local Variables: //
479// tab-width: 4 //
480// mode: c++ //
481// compile-command: "make install" //
482// End: //
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