source: src/GenPoly/Lvalue.cc@ bc03be3

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 with_gc
Last change on this file since bc03be3 was a4d188f, checked in by Rob Schluntz <rschlunt@…>, 8 years ago

Remove commented code in Lvalue.cc
  • Property mode set to 100644
File size: 18.7 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 "GenPoly.h" // for isPolyType
21#include "Lvalue.h"
22
23#include "Parser/LinkageSpec.h" // for Spec, isBuiltin, Intrinsic
24#include "ResolvExpr/TypeEnvironment.h" // for AssertionSet, OpenVarSet
25#include "ResolvExpr/Unify.h" // for unify
26#include "ResolvExpr/typeops.h"
27#include "SymTab/Autogen.h"
28#include "SymTab/Indexer.h" // for Indexer
29#include "SynTree/Declaration.h" // for Declaration, FunctionDecl
30#include "SynTree/Expression.h" // for Expression, ConditionalExpr
31#include "SynTree/Mutator.h" // for mutateAll, Mutator
32#include "SynTree/Statement.h" // for ReturnStmt, Statement (ptr o...
33#include "SynTree/Type.h" // for PointerType, Type, FunctionType
34#include "SynTree/Visitor.h" // for Visitor, acceptAll
35
36#if 0
37#define PRINT(x) x
38#else
39#define PRINT(x)
40#endif
41
42namespace GenPoly {
43 namespace {
44 // TODO: fold this into the general createDeref function??
45 Expression * mkDeref( Expression * arg ) {
46 if ( SymTab::dereferenceOperator ) {
47 VariableExpr * deref = new VariableExpr( SymTab::dereferenceOperator );
48 deref->result = new PointerType( Type::Qualifiers(), deref->result );
49 Type * base = InitTweak::getPointerBase( arg->result );
50 assertf( base, "expected pointer type in dereference (type was %s)", toString( arg->result ).c_str() );
51 ApplicationExpr * ret = new ApplicationExpr( deref, { arg } );
52 delete ret->result;
53 ret->result = base->clone();
54 ret->result->set_lvalue( true );
55 return ret;
56 } else {
57 return UntypedExpr::createDeref( arg );
58 }
59 }
60
61 struct ReferenceConversions final : public WithStmtsToAdd {
62 Expression * postmutate( CastExpr * castExpr );
63 Expression * postmutate( AddressExpr * addrExpr );
64 };
65
66 /// Intrinsic functions that take reference parameters don't REALLY take reference parameters -- their reference arguments must always be implicitly dereferenced.
67 struct FixIntrinsicArgs final {
68 Expression * postmutate( ApplicationExpr * appExpr );
69 };
70
71 struct FixIntrinsicResult final : public WithGuards {
72 Expression * postmutate( ApplicationExpr * appExpr );
73 void premutate( FunctionDecl * funcDecl );
74 bool inIntrinsic = false;
75 };
76
77 /// Replace reference types with pointer types
78 struct ReferenceTypeElimination final {
79 Type * postmutate( ReferenceType * refType );
80 };
81
82 /// GCC-like Generalized Lvalues (which have since been removed from GCC)
83 /// https://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Lvalues.html#Lvalues
84 /// Replaces &(a,b) with (a, &b), &(a ? b : c) with (a ? &b : &c)
85 struct GeneralizedLvalue final : public WithVisitorRef<GeneralizedLvalue> {
86 Expression * postmutate( AddressExpr * addressExpr );
87 Expression * postmutate( MemberExpr * memExpr );
88
89 template<typename Func>
90 Expression * applyTransformation( Expression * expr, Expression * arg, Func mkExpr );
91 };
92
93 /// Removes redundant &*/*& pattern that this pass can generate
94 struct CollapseAddrDeref final {
95 Expression * postmutate( AddressExpr * addressExpr );
96 Expression * postmutate( ApplicationExpr * appExpr );
97 };
98
99 struct AddrRef final : public WithGuards {
100 void premutate( AddressExpr * addrExpr );
101 Expression * postmutate( AddressExpr * addrExpr );
102 void premutate( Expression * expr );
103
104 bool first = true;
105 bool current = false;
106 int refDepth = 0;
107 };
108 } // namespace
109
110 static bool referencesEliminated = false;
111 // used by UntypedExpr::createDeref to determine whether result type of dereference should be ReferenceType or value type.
112 bool referencesPermissable() {
113 return ! referencesEliminated;
114 }
115
116 void convertLvalue( std::list< Declaration* > & translationUnit ) {
117 PassVisitor<ReferenceConversions> refCvt;
118 PassVisitor<ReferenceTypeElimination> elim;
119 PassVisitor<GeneralizedLvalue> genLval;
120 PassVisitor<FixIntrinsicArgs> fixer;
121 PassVisitor<CollapseAddrDeref> collapser;
122 PassVisitor<AddrRef> addrRef;
123 PassVisitor<FixIntrinsicResult> intrinsicResults;
124 mutateAll( translationUnit, intrinsicResults );
125 mutateAll( translationUnit, addrRef );
126 mutateAll( translationUnit, refCvt );
127 mutateAll( translationUnit, fixer );
128 mutateAll( translationUnit, collapser );
129 mutateAll( translationUnit, genLval );
130 mutateAll( translationUnit, elim ); // last because other passes need reference types to work
131
132 // from this point forward, no other pass should create reference types.
133 referencesEliminated = true;
134 }
135
136 Expression * generalizedLvalue( Expression * expr ) {
137 PassVisitor<GeneralizedLvalue> genLval;
138 return expr->acceptMutator( genLval );
139 }
140
141 namespace {
142 // true for intrinsic function calls that return a reference
143 bool isIntrinsicReference( Expression * expr ) {
144 if ( UntypedExpr * untyped = dynamic_cast< UntypedExpr * >( expr ) ) {
145 std::string fname = InitTweak::getFunctionName( untyped );
146 // known intrinsic-reference prelude functions
147 return fname == "*?" || fname == "?[?]";
148 } else if ( ApplicationExpr * appExpr = dynamic_cast< ApplicationExpr * > ( expr ) ) {
149 if ( DeclarationWithType * func = InitTweak::getFunction( appExpr ) ) {
150 // use type of return variable rather than expr result type, since it may have been changed to a pointer type
151 FunctionType * ftype = GenPoly::getFunctionType( func->get_type() );
152 Type * ret = ftype->returnVals.empty() ? nullptr : ftype->returnVals.front()->get_type();
153 return func->linkage == LinkageSpec::Intrinsic && dynamic_cast<ReferenceType *>( ret );
154 }
155 }
156 return false;
157 }
158
159 Expression * FixIntrinsicResult::postmutate( ApplicationExpr * appExpr ) {
160 if ( isIntrinsicReference( appExpr ) ) {
161 // eliminate reference types from intrinsic applications - now they return lvalues
162 Type * result = appExpr->result;
163 appExpr->result = result->stripReferences()->clone();
164 appExpr->result->set_lvalue( true );
165 if ( ! inIntrinsic ) {
166 // when not in an intrinsic function, add a cast to
167 // don't add cast when in an intrinsic function, since they already have the cast
168 Expression * ret = new CastExpr( appExpr, result );
169 std::swap( ret->env, appExpr->env );
170 return ret;
171 }
172 delete result;
173 }
174 return appExpr;
175 }
176
177 void FixIntrinsicResult::premutate( FunctionDecl * funcDecl ) {
178 GuardValue( inIntrinsic );
179 inIntrinsic = funcDecl->linkage == LinkageSpec::Intrinsic;
180 }
181
182 Expression * FixIntrinsicArgs::postmutate( ApplicationExpr * appExpr ) {
183 // intrinsic functions don't really take reference-typed parameters, so they require an implicit dereference on their arguments.
184 if ( DeclarationWithType * function = InitTweak::getFunction( appExpr ) ) {
185 FunctionType * ftype = GenPoly::getFunctionType( function->get_type() );
186 assertf( ftype, "Function declaration does not have function type." );
187 // can be of differing lengths only when function is variadic
188 assertf( ftype->parameters.size() == appExpr->args.size() || ftype->isVarArgs, "ApplicationExpr args do not match formal parameter type." );
189
190
191 unsigned int i = 0;
192 const unsigned int end = ftype->parameters.size();
193 for ( auto p : unsafe_group_iterate( appExpr->args, ftype->parameters ) ) {
194 if (i == end) break;
195 Expression *& arg = std::get<0>( p );
196 Type * formal = std::get<1>( p )->get_type();
197 PRINT(
198 std::cerr << "pair<0>: " << arg << std::endl;
199 std::cerr << "pair<1>: " << formal << std::endl;
200 )
201 if ( dynamic_cast<ReferenceType*>( formal ) ) {
202 if ( isIntrinsicReference( arg ) ) { // do not combine conditions, because that changes the meaning of the else if
203 if ( function->get_linkage() != LinkageSpec::Intrinsic ) { // intrinsic functions that turn pointers into references
204 // if argument is dereference or array subscript, the result isn't REALLY a reference, so it's not necessary to fix the argument
205 PRINT(
206 std::cerr << "===is intrinsic arg in non-intrinsic call - adding address" << std::endl;
207 )
208 arg = new AddressExpr( arg );
209 }
210 } else if ( function->get_linkage() == LinkageSpec::Intrinsic ) {
211 // std::cerr << "===adding deref to arg" << std::endl;
212 // if the parameter is a reference, add a dereference to the reference-typed argument.
213 Type * baseType = InitTweak::getPointerBase( arg->result );
214 assertf( baseType, "parameter is reference, arg must be pointer or reference: %s", toString( arg->result ).c_str() );
215 PointerType * ptrType = new PointerType( Type::Qualifiers(), baseType->clone() );
216 delete arg->result;
217 arg->set_result( ptrType );
218 arg = mkDeref( arg );
219 }
220 }
221 ++i;
222 }
223 }
224 return appExpr;
225 }
226
227 // idea: &&&E: get outer &, inner &
228 // at inner &, record depth D of reference type
229 // at outer &, add D derefs.
230 void AddrRef::premutate( Expression * ) {
231 GuardValue( current );
232 GuardValue( first );
233 current = false;
234 first = true;
235 }
236
237 void AddrRef::premutate( AddressExpr * ) {
238 GuardValue( current );
239 GuardValue( first );
240 current = first;
241 first = false;
242 if ( current ) {
243 GuardValue( refDepth );
244 refDepth = 0;
245 }
246 }
247
248 Expression * AddrRef::postmutate( AddressExpr * addrExpr ) {
249 if ( refDepth == 0 ) {
250 if ( ! isIntrinsicReference( addrExpr->arg ) ) {
251 // try to avoid ?[?]
252 refDepth = addrExpr->arg->result->referenceDepth();
253 }
254 }
255 if ( current ) {
256 Expression * ret = addrExpr;
257 while ( refDepth ) {
258 ret = mkDeref( ret );
259 refDepth--;
260 }
261 return ret;
262 }
263 return addrExpr;
264 }
265
266 Expression * ReferenceConversions::postmutate( AddressExpr * addrExpr ) {
267 // Inner expression may have been lvalue to reference conversion, which becomes an address expression.
268 // In this case, remove the outer address expression and return the argument.
269 // TODO: It's possible that this might catch too much and require a more sophisticated check.
270 return addrExpr;
271 }
272
273 Expression * ReferenceConversions::postmutate( CastExpr * castExpr ) {
274 // xxx - is it possible to convert directly between reference types with a different base? E.g.,
275 // int x;
276 // (double&)x;
277 // At the moment, I am working off of the assumption that this is illegal, thus the cast becomes redundant
278 // after this pass, so trash the cast altogether. If that changes, care must be taken to insert the correct
279 // pointer casts in the right places.
280
281 // Note: reference depth difference is the determining factor in what code is run, rather than whether something is
282 // reference type or not, since conversion still needs to occur when both types are references that differ in depth.
283
284 Type * destType = castExpr->result;
285 Type * srcType = castExpr->arg->result;
286 int depth1 = destType->referenceDepth();
287 int depth2 = srcType->referenceDepth();
288 int diff = depth1 - depth2;
289
290 if ( diff > 0 && ! srcType->get_lvalue() ) {
291 // rvalue to reference conversion -- introduce temporary
292 // know that reference depth of cast argument is 0, need to introduce n temporaries for reference depth of n, e.g.
293 // (int &&&)3;
294 // becomes
295 // int __ref_tmp_0 = 3;
296 // int & __ref_tmp_1 = _&_ref_tmp_0;
297 // int && __ref_tmp_2 = &__ref_tmp_1;
298 // &__ref_tmp_2;
299 // the last & comes from the remaining reference conversion code
300 SemanticWarning( castExpr->arg->location, Warning::RvalueToReferenceConversion, toCString( castExpr->arg ) );
301
302 static UniqueName tempNamer( "__ref_tmp_" );
303 ObjectDecl * temp = ObjectDecl::newObject( tempNamer.newName(), castExpr->arg->result->clone(), new SingleInit( castExpr->arg ) );
304 PRINT( std::cerr << "made temp: " << temp << std::endl; )
305 stmtsToAddBefore.push_back( new DeclStmt( temp ) );
306 for ( int i = 0; i < depth1-1; i++ ) { // xxx - maybe this should be diff-1? check how this works with reference type for srcType
307 ObjectDecl * newTemp = ObjectDecl::newObject( tempNamer.newName(), new ReferenceType( Type::Qualifiers(), temp->type->clone() ), new SingleInit( new AddressExpr( new VariableExpr( temp ) ) ) );
308 PRINT( std::cerr << "made temp" << i << ": " << newTemp << std::endl; )
309 stmtsToAddBefore.push_back( new DeclStmt( newTemp ) );
310 temp = newTemp;
311 }
312 // update diff so that remaining code works out correctly
313 castExpr->arg = new VariableExpr( temp );
314 PRINT( std::cerr << "update cast to: " << castExpr << std::endl; )
315 srcType = castExpr->arg->result;
316 depth2 = srcType->referenceDepth();
317 diff = depth1 - depth2;
318 assert( diff == 1 );
319 }
320
321 // handle conversion between different depths
322 PRINT (
323 if ( depth1 || depth2 ) {
324 std::cerr << "destType: " << destType << " / srcType: " << srcType << std::endl;
325 std::cerr << "depth: " << depth1 << " / " << depth2 << std::endl;
326 }
327 )
328 if ( diff > 0 ) {
329 // conversion to type with more depth (e.g. int & -> int &&): add address-of for each level of difference
330 Expression * ret = castExpr->arg;
331 for ( int i = 0; i < diff; ++i ) {
332 ret = new AddressExpr( ret );
333 }
334 if ( srcType->get_lvalue() && srcType->get_qualifiers() != strict_dynamic_cast<ReferenceType *>( destType )->base->get_qualifiers() ) {
335 // must keep cast if cast-to type is different from the actual type
336 castExpr->arg = ret;
337 return castExpr;
338 }
339 ret->env = castExpr->env;
340 delete ret->result;
341 ret->result = castExpr->result;
342 castExpr->env = nullptr;
343 castExpr->arg = nullptr;
344 castExpr->result = nullptr;
345 delete castExpr;
346 return ret;
347 } else if ( diff < 0 ) {
348 // conversion to type with less depth (e.g. int && -> int &): add dereferences for each level of difference
349 diff = -diff; // care only about magnitude now
350 Expression * ret = castExpr->arg;
351 for ( int i = 0; i < diff; ++i ) {
352 ret = mkDeref( ret );
353 }
354 if ( ! ResolvExpr::typesCompatibleIgnoreQualifiers( destType->stripReferences(), srcType->stripReferences(), SymTab::Indexer() ) ) {
355 // must keep cast if types are different
356 castExpr->arg = ret;
357 return castExpr;
358 }
359 ret->env = castExpr->env;
360 delete ret->result;
361 ret->result = castExpr->result;
362 ret->result->set_lvalue( true ); // ensure result is lvalue
363 castExpr->env = nullptr;
364 castExpr->arg = nullptr;
365 castExpr->result = nullptr;
366 delete castExpr;
367 return ret;
368 } else {
369 assert( diff == 0 );
370 // conversion between references of the same depth
371 return castExpr;
372 }
373 }
374
375 Type * ReferenceTypeElimination::postmutate( ReferenceType * refType ) {
376 Type * base = refType->base;
377 Type::Qualifiers qualifiers = refType->get_qualifiers();
378 refType->base = nullptr;
379 delete refType;
380 return new PointerType( qualifiers, base );
381 }
382
383 template<typename Func>
384 Expression * GeneralizedLvalue::applyTransformation( Expression * expr, Expression * arg, Func mkExpr ) {
385 if ( CommaExpr * commaExpr = dynamic_cast< CommaExpr * >( arg ) ) {
386 Expression * arg1 = commaExpr->arg1->clone();
387 Expression * arg2 = commaExpr->arg2->clone();
388 Expression * ret = new CommaExpr( arg1, mkExpr( arg2 )->acceptMutator( *visitor ) );
389 ret->env = expr->env;
390 expr->env = nullptr;
391 delete expr;
392 return ret;
393 } else if ( ConditionalExpr * condExpr = dynamic_cast< ConditionalExpr * >( arg ) ) {
394 Expression * arg1 = condExpr->arg1->clone();
395 Expression * arg2 = condExpr->arg2->clone();
396 Expression * arg3 = condExpr->arg3->clone();
397 ConditionalExpr * ret = new ConditionalExpr( arg1, mkExpr( arg2 )->acceptMutator( *visitor ), mkExpr( arg3 )->acceptMutator( *visitor ) );
398 ret->env = expr->env;
399 expr->env = nullptr;
400 delete expr;
401
402 // conditional expr type may not be either of the argument types, need to unify
403 using namespace ResolvExpr;
404 Type* commonType = nullptr;
405 TypeEnvironment newEnv;
406 AssertionSet needAssertions, haveAssertions;
407 OpenVarSet openVars;
408 unify( ret->arg2->result, ret->arg3->result, newEnv, needAssertions, haveAssertions, openVars, SymTab::Indexer(), commonType );
409 ret->result = commonType ? commonType : ret->arg2->result->clone();
410 return ret;
411 }
412 return expr;
413 }
414
415 Expression * GeneralizedLvalue::postmutate( MemberExpr * memExpr ) {
416 return applyTransformation( memExpr, memExpr->aggregate, [=]( Expression * aggr ) { return new MemberExpr( memExpr->member, aggr ); } );
417 }
418
419 Expression * GeneralizedLvalue::postmutate( AddressExpr * addrExpr ) {
420 return applyTransformation( addrExpr, addrExpr->arg, []( Expression * arg ) { return new AddressExpr( arg ); } );
421 }
422
423 Expression * CollapseAddrDeref::postmutate( AddressExpr * addrExpr ) {
424 Expression * arg = addrExpr->arg;
425 if ( isIntrinsicReference( arg ) ) {
426 std::string fname = InitTweak::getFunctionName( arg );
427 if ( fname == "*?" ) {
428 Expression *& arg0 = InitTweak::getCallArg( arg, 0 );
429 Expression * ret = arg0;
430 ret->set_env( addrExpr->env );
431 arg0 = nullptr;
432 addrExpr->env = nullptr;
433 delete addrExpr;
434 return ret;
435 }
436 } else if ( CastExpr * castExpr = dynamic_cast< CastExpr * > ( arg ) ) {
437 // need to move cast to pointer type out a level since address of pointer
438 // is not valid C code (can be introduced in prior passes, e.g., InstantiateGeneric)
439 if ( InitTweak::getPointerBase( castExpr->result ) ) {
440 addrExpr->arg = castExpr->arg;
441 castExpr->arg = addrExpr;
442 castExpr->result = new PointerType( Type::Qualifiers(), castExpr->result );
443 return castExpr;
444 }
445 }
446 return addrExpr;
447 }
448
449 Expression * CollapseAddrDeref::postmutate( ApplicationExpr * appExpr ) {
450 if ( isIntrinsicReference( appExpr ) ) {
451 std::string fname = InitTweak::getFunctionName( appExpr );
452 if ( fname == "*?" ) {
453 Expression * arg = InitTweak::getCallArg( appExpr, 0 );
454 // xxx - this isn't right, because it can remove casts that should be there...
455 // while ( CastExpr * castExpr = dynamic_cast< CastExpr * >( arg ) ) {
456 // arg = castExpr->get_arg();
457 // }
458 if ( AddressExpr * addrExpr = dynamic_cast< AddressExpr * >( arg ) ) {
459 Expression * ret = addrExpr->arg;
460 ret->env = appExpr->env;
461 addrExpr->arg = nullptr;
462 appExpr->env = nullptr;
463 delete appExpr;
464 return ret;
465 }
466 }
467 }
468 return appExpr;
469 }
470 } // namespace
471} // namespace GenPoly
472
473// Local Variables: //
474// tab-width: 4 //
475// mode: c++ //
476// compile-command: "make install" //
477// End: //
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