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source: src/GenPoly/Lvalue.cc @ fc56cdbf

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Last change on this file since fc56cdbf was fc56cdbf, checked in by Rob Schluntz <rschlunt@…>, 7 years ago
Handle conversions between reference types of different depths
Property mode set to `100644`
File size: 18.4 KB

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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
48	namespace 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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