source: src/InitTweak/FixInit.cc@ dd51906

ADT aaron-thesis arm-eh ast-experimental cleanup-dtors ctor deferred_resn demangler enum forall-pointer-decay gc_noraii jacob/cs343-translation jenkins-sandbox memory 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 dd51906 was 9554d9b, checked in by Rob Schluntz <rschlunt@…>, 9 years ago

elide copy constructor calls in polymorphic code
  • Property mode set to 100644
File size: 19.5 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// FixInit.h --
8//
9// Author : Rob Schluntz
10// Created On : Wed Jan 13 16:29:30 2016
11// Last Modified By : Rob Schluntz
12// Last Modified On : Fri May 13 11:44:26 2016
13// Update Count : 30
14//
15
16#include <stack>
17#include <list>
18#include "FixInit.h"
19#include "InitTweak.h"
20#include "ResolvExpr/Resolver.h"
21#include "ResolvExpr/typeops.h"
22#include "SynTree/Declaration.h"
23#include "SynTree/Type.h"
24#include "SynTree/Expression.h"
25#include "SynTree/Statement.h"
26#include "SynTree/Initializer.h"
27#include "SynTree/Mutator.h"
28#include "SymTab/Indexer.h"
29#include "GenPoly/PolyMutator.h"
30
31bool ctordtorp = false;
32#define PRINT( text ) if ( ctordtorp ) { text }
33
34namespace InitTweak {
35 namespace {
36 const std::list<Label> noLabels;
37 const std::list<Expression*> noDesignators;
38 }
39
40 class InsertImplicitCalls : public GenPoly::PolyMutator {
41 public:
42 /// wrap function application expressions as ImplicitCopyCtorExpr nodes
43 /// so that it is easy to identify which function calls need their parameters
44 /// to be copy constructed
45 static void insert( std::list< Declaration * > & translationUnit );
46
47 virtual Expression * mutate( ApplicationExpr * appExpr );
48 };
49
50 class ResolveCopyCtors : public SymTab::Indexer {
51 public:
52 /// generate temporary ObjectDecls for each argument and return value of each
53 /// ImplicitCopyCtorExpr, generate/resolve copy construction expressions for each,
54 /// and generate/resolve destructors for both arguments and return value temporaries
55 static void resolveImplicitCalls( std::list< Declaration * > & translationUnit );
56
57 virtual void visit( ImplicitCopyCtorExpr * impCpCtorExpr );
58
59 /// create and resolve ctor/dtor expression: fname(var, [cpArg])
60 ApplicationExpr * makeCtorDtor( const std::string & fname, ObjectDecl * var, Expression * cpArg = NULL );
61 /// true if type does not need to be copy constructed to ensure correctness
62 bool skipCopyConstruct( Type * );
63 private:
64 TypeSubstitution * env;
65 };
66
67 class FixInit : public GenPoly::PolyMutator {
68 public:
69 /// expand each object declaration to use its constructor after it is declared.
70 /// insert destructor calls at the appropriate places
71 static void fixInitializers( std::list< Declaration * > &translationUnit );
72
73 virtual DeclarationWithType * mutate( ObjectDecl *objDecl );
74
75 virtual CompoundStmt * mutate( CompoundStmt * compoundStmt );
76 virtual Statement * mutate( ReturnStmt * returnStmt );
77 virtual Statement * mutate( BranchStmt * branchStmt );
78
79 private:
80 // stack of list of statements - used to differentiate scopes
81 std::list< std::list< Statement * > > dtorStmts;
82 };
83
84 class FixCopyCtors : public GenPoly::PolyMutator {
85 public:
86 /// expand ImplicitCopyCtorExpr nodes into the temporary declarations, copy constructors,
87 /// call expression, and destructors
88 static void fixCopyCtors( std::list< Declaration * > &translationUnit );
89
90 virtual Expression * mutate( ImplicitCopyCtorExpr * impCpCtorExpr );
91
92 private:
93 // stack of list of statements - used to differentiate scopes
94 std::list< std::list< Statement * > > dtorStmts;
95 };
96
97 void fix( std::list< Declaration * > & translationUnit ) {
98 InsertImplicitCalls::insert( translationUnit );
99 ResolveCopyCtors::resolveImplicitCalls( translationUnit );
100 FixInit::fixInitializers( translationUnit );
101 // FixCopyCtors must happen after FixInit, so that destructors are placed correctly
102 FixCopyCtors::fixCopyCtors( translationUnit );
103 }
104
105 void InsertImplicitCalls::insert( std::list< Declaration * > & translationUnit ) {
106 InsertImplicitCalls inserter;
107 mutateAll( translationUnit, inserter );
108 }
109
110 void ResolveCopyCtors::resolveImplicitCalls( std::list< Declaration * > & translationUnit ) {
111 ResolveCopyCtors resolver;
112 acceptAll( translationUnit, resolver );
113 }
114
115 void FixInit::fixInitializers( std::list< Declaration * > & translationUnit ) {
116 FixInit fixer;
117 mutateAll( translationUnit, fixer );
118 }
119
120 void FixCopyCtors::fixCopyCtors( std::list< Declaration * > & translationUnit ) {
121 FixCopyCtors fixer;
122 mutateAll( translationUnit, fixer );
123 }
124
125 Expression * InsertImplicitCalls::mutate( ApplicationExpr * appExpr ) {
126 appExpr = dynamic_cast< ApplicationExpr * >( Mutator::mutate( appExpr ) );
127 assert( appExpr );
128
129 if ( VariableExpr * function = dynamic_cast< VariableExpr * > ( appExpr->get_function() ) ) {
130 if ( function->get_var()->get_linkage() == LinkageSpec::Intrinsic ) {
131 // optimization: don't need to copy construct in order to call intrinsic functions
132 return appExpr;
133 } else if ( DeclarationWithType * funcDecl = dynamic_cast< DeclarationWithType * > ( function->get_var() ) ) {
134 // FunctionType * ftype = funcDecl->get_functionType();
135 FunctionType * ftype = dynamic_cast< FunctionType * >( GenPoly::getFunctionType( funcDecl->get_type() ) );
136 assert( ftype );
137 if ( (funcDecl->get_name() == "?{}" || funcDecl->get_name() == "?=?") && ftype->get_parameters().size() == 2 ) {
138 Type * t1 = ftype->get_parameters().front()->get_type();
139 Type * t2 = ftype->get_parameters().back()->get_type();
140 PointerType * ptrType = dynamic_cast< PointerType * > ( t1 );
141 assert( ptrType );
142
143 if ( ResolvExpr::typesCompatible( ptrType->get_base(), t2, SymTab::Indexer() ) ) {
144 // optimization: don't need to copy construct in order to call a copy constructor or
145 // assignment operator
146 return appExpr;
147 }
148 } else if ( funcDecl->get_name() == "^?{}" ) {
149 // correctness: never copy construct arguments to a destructor
150 return appExpr;
151 }
152 }
153 }
154 PRINT( std::cerr << "InsertImplicitCalls: adding a wrapper " << appExpr << std::endl; )
155
156 // wrap each function call so that it is easy to identify nodes that have to be copy constructed
157 ImplicitCopyCtorExpr * expr = new ImplicitCopyCtorExpr( appExpr );
158 // save the type substitution onto the new node so that it is easy to find.
159 // Ensure it is not deleted with the ImplicitCopyCtorExpr by removing it before deletion.
160 // The substitution is needed to obtain the type of temporary variables so that copy constructor
161 // calls can be resolved. Normally this is what PolyMutator is for, but the pass that resolves
162 // copy constructor calls must be an Indexer. We could alternatively make a PolyIndexer which
163 // saves the environment, or compute the types of temporaries here, but it's much simpler to
164 // save the environment here, and more cohesive to compute temporary variables and resolve copy
165 // constructor calls together.
166 assert( env );
167 expr->set_env( env );
168 return expr;
169 }
170
171 bool ResolveCopyCtors::skipCopyConstruct( Type * type ) {
172 return dynamic_cast< VarArgsType * >( type ) || GenPoly::getFunctionType( type );
173 }
174
175 ApplicationExpr * ResolveCopyCtors::makeCtorDtor( const std::string & fname, ObjectDecl * var, Expression * cpArg ) {
176 assert( var );
177 UntypedExpr * untyped = new UntypedExpr( new NameExpr( fname ) );
178 untyped->get_args().push_back( new AddressExpr( new VariableExpr( var ) ) );
179 if (cpArg) untyped->get_args().push_back( cpArg );
180
181 // resolve copy constructor
182 // should only be one alternative for copy ctor and dtor expressions, since
183 // all arguments are fixed (VariableExpr and already resolved expression)
184 PRINT( std::cerr << "ResolvingCtorDtor " << untyped << std::endl; )
185 ApplicationExpr * resolved = dynamic_cast< ApplicationExpr * >( ResolvExpr::findVoidExpression( untyped, *this ) );
186 if ( resolved->get_env() ) {
187 env->add( *resolved->get_env() );
188 }
189
190 assert( resolved );
191 delete untyped;
192 return resolved;
193 }
194
195 void ResolveCopyCtors::visit( ImplicitCopyCtorExpr *impCpCtorExpr ) {
196 static UniqueName tempNamer("_tmp_cp");
197 static UniqueName retNamer("_tmp_cp_ret");
198
199 PRINT( std::cerr << "ResolveCopyCtors: " << impCpCtorExpr << std::endl; )
200 Visitor::visit( impCpCtorExpr );
201 env = impCpCtorExpr->get_env(); // xxx - maybe we really should just have a PolyIndexer...
202
203 ApplicationExpr * appExpr = impCpCtorExpr->get_callExpr();
204
205 // take each argument and attempt to copy construct it.
206 for ( Expression * & arg : appExpr->get_args() ) {
207 PRINT( std::cerr << "Type Substitution: " << *impCpCtorExpr->get_env() << std::endl; )
208 // xxx - need to handle tuple arguments
209 assert( ! arg->get_results().empty() );
210 Type * result = arg->get_results().front();
211 if ( skipCopyConstruct( result ) ) continue; // skip certain non-copyable types
212 // type may involve type variables, so apply type substitution to get temporary variable's actual type
213 result = result->clone();
214 impCpCtorExpr->get_env()->apply( result );
215 ObjectDecl * tmp = new ObjectDecl( tempNamer.newName(), DeclarationNode::NoStorageClass, LinkageSpec::C, 0, result, 0 );
216 tmp->get_type()->set_isConst( false );
217
218 // create and resolve copy constructor
219 PRINT( std::cerr << "makeCtorDtor for an argument" << std::endl; )
220 ApplicationExpr * cpCtor = makeCtorDtor( "?{}", tmp, arg );
221
222 // if the chosen constructor is intrinsic, the copy is unnecessary, so
223 // don't create the temporary and don't call the copy constructor
224 VariableExpr * function = dynamic_cast< VariableExpr * >( cpCtor->get_function() );
225 assert( function );
226 if ( function->get_var()->get_linkage() != LinkageSpec::Intrinsic ) {
227 // replace argument to function call with temporary
228 arg = new CommaExpr( cpCtor, new VariableExpr( tmp ) );
229 impCpCtorExpr->get_tempDecls().push_back( tmp );
230 impCpCtorExpr->get_dtors().push_front( makeCtorDtor( "^?{}", tmp ) );
231 }
232 }
233
234 // each return value from the call needs to be connected with an ObjectDecl
235 // at the call site, which is initialized with the return value and is destructed
236 // later
237 // xxx - handle multiple return values
238 ApplicationExpr * callExpr = impCpCtorExpr->get_callExpr();
239 // xxx - is this right? callExpr may not have the right environment, because it was attached
240 // at a higher level. Trying to pass that environment along.
241 callExpr->set_env( impCpCtorExpr->get_env()->clone() );
242 for ( Type * result : appExpr->get_results() ) {
243 result = result->clone();
244 impCpCtorExpr->get_env()->apply( result );
245 ObjectDecl * ret = new ObjectDecl( retNamer.newName(), DeclarationNode::NoStorageClass, LinkageSpec::C, 0, result, 0 );
246 ret->get_type()->set_isConst( false );
247 impCpCtorExpr->get_returnDecls().push_back( ret );
248 PRINT( std::cerr << "makeCtorDtor for a return" << std::endl; )
249 impCpCtorExpr->get_dtors().push_front( makeCtorDtor( "^?{}", ret ) );
250 }
251 PRINT( std::cerr << "after Resolving: " << impCpCtorExpr << std::endl; )
252 }
253
254
255 Expression * FixCopyCtors::mutate( ImplicitCopyCtorExpr * impCpCtorExpr ) {
256 PRINT( std::cerr << "FixCopyCtors: " << impCpCtorExpr << std::endl; )
257
258 impCpCtorExpr = dynamic_cast< ImplicitCopyCtorExpr * >( Mutator::mutate( impCpCtorExpr ) );
259 assert( impCpCtorExpr );
260
261 std::list< ObjectDecl * > & tempDecls = impCpCtorExpr->get_tempDecls();
262 std::list< ObjectDecl * > & returnDecls = impCpCtorExpr->get_returnDecls();
263 std::list< Expression * > & dtors = impCpCtorExpr->get_dtors();
264
265 // add all temporary declarations and their constructors
266 for ( ObjectDecl * obj : tempDecls ) {
267 stmtsToAdd.push_back( new DeclStmt( noLabels, obj ) );
268 }
269 for ( ObjectDecl * obj : returnDecls ) {
270 stmtsToAdd.push_back( new DeclStmt( noLabels, obj ) );
271 }
272
273 // add destructors after current statement
274 for ( Expression * dtor : dtors ) {
275 stmtsToAddAfter.push_back( new ExprStmt( noLabels, dtor ) );
276 }
277
278 // xxx - update to work with multiple return values
279 ObjectDecl * returnDecl = returnDecls.empty() ? NULL : returnDecls.front();
280 Expression * callExpr = impCpCtorExpr->get_callExpr();
281
282 PRINT( std::cerr << "Coming out the back..." << impCpCtorExpr << std::endl; )
283
284 // xxx - some of these aren't necessary, and can be removed once this is stable
285 dtors.clear();
286 tempDecls.clear();
287 returnDecls.clear();
288 impCpCtorExpr->set_callExpr( NULL );
289 impCpCtorExpr->set_env( NULL );
290 delete impCpCtorExpr;
291
292 if ( returnDecl ) {
293 UntypedExpr * assign = new UntypedExpr( new NameExpr( "?=?" ) );
294 assign->get_args().push_back( new VariableExpr( returnDecl ) );
295 assign->get_args().push_back( callExpr );
296 // know the result type of the assignment is the type of the LHS (minus the pointer), so
297 // add that onto the assignment expression so that later steps have the necessary information
298 assign->add_result( returnDecl->get_type()->clone() );
299
300 Expression * retExpr = new CommaExpr( assign, new VariableExpr( returnDecl ) );
301 if ( callExpr->get_results().front()->get_isLvalue() ) {
302 // lvalue returning functions are funny. Lvalue.cc inserts a *? in front of any
303 // lvalue returning non-intrinsic function. Add an AddressExpr to the call to negate
304 // the derefence and change the type of the return temporary from T to T* to properly
305 // capture the return value. Then dereference the result of the comma expression, since
306 // the lvalue returning call was originally wrapped with an AddressExpr.
307 // Effectively, this turns
308 // lvalue T f();
309 // &*f()
310 // into
311 // T * tmp_cp_retN;
312 // tmp_cp_ret_N = &*(tmp_cp_ret_N = &*f(), tmp_cp_ret);
313 // which work out in terms of types, but is pretty messy. It would be nice to find a better way.
314 assign->get_args().back() = new AddressExpr( assign->get_args().back() );
315
316 Type * resultType = returnDecl->get_type()->clone();
317 returnDecl->set_type( new PointerType( Type::Qualifiers(), returnDecl->get_type() ) );
318 UntypedExpr * deref = new UntypedExpr( new NameExpr( "*?" ) );
319 deref->get_args().push_back( retExpr );
320 deref->add_result( resultType );
321 retExpr = deref;
322 }
323 // xxx - might need to set env on retExpr...
324 // retExpr->set_env( env->clone() );
325 return retExpr;
326 } else {
327 return callExpr;
328 }
329 }
330
331 DeclarationWithType *FixInit::mutate( ObjectDecl *objDecl ) {
332 // first recursively handle pieces of ObjectDecl so that they aren't missed by other visitors
333 // when the init is removed from the ObjectDecl
334 objDecl = dynamic_cast< ObjectDecl * >( Mutator::mutate( objDecl ) );
335
336 if ( ConstructorInit * ctorInit = dynamic_cast< ConstructorInit * >( objDecl->get_init() ) ) {
337 // a decision should have been made by the resolver, so ctor and init are not both non-NULL
338 assert( ! ctorInit->get_ctor() || ! ctorInit->get_init() );
339 if ( Statement * ctor = ctorInit->get_ctor() ) {
340 if ( objDecl->get_storageClass() == DeclarationNode::Static ) {
341 // generate:
342 // static bool __objName_uninitialized = true;
343 // if (__objName_uninitialized) {
344 // __ctor(__objName);
345 // void dtor_atexit() {
346 // __dtor(__objName);
347 // }
348 // on_exit(dtorOnExit, &__objName);
349 // __objName_uninitialized = false;
350 // }
351
352 // generate first line
353 BasicType * boolType = new BasicType( Type::Qualifiers(), BasicType::Bool );
354 SingleInit * boolInitExpr = new SingleInit( new ConstantExpr( Constant( boolType->clone(), "1" ) ), noDesignators );
355 ObjectDecl * isUninitializedVar = new ObjectDecl( objDecl->get_mangleName() + "_uninitialized", DeclarationNode::Static, LinkageSpec::Cforall, 0, boolType, boolInitExpr );
356 isUninitializedVar->fixUniqueId();
357
358 // void dtor_atexit(...) {...}
359 FunctionDecl * dtorCaller = new FunctionDecl( objDecl->get_mangleName() + "_dtor_atexit", DeclarationNode::NoStorageClass, LinkageSpec::C, new FunctionType( Type::Qualifiers(), false ), new CompoundStmt( noLabels ), false, false );
360 dtorCaller->fixUniqueId();
361 dtorCaller->get_statements()->get_kids().push_back( ctorInit->get_dtor() );
362
363 // on_exit(dtor_atexit);
364 UntypedExpr * callAtexit = new UntypedExpr( new NameExpr( "atexit" ) );
365 callAtexit->get_args().push_back( new VariableExpr( dtorCaller ) );
366
367 // __objName_uninitialized = false;
368 UntypedExpr * setTrue = new UntypedExpr( new NameExpr( "?=?" ) );
369 setTrue->get_args().push_back( new VariableExpr( isUninitializedVar ) );
370 setTrue->get_args().push_back( new ConstantExpr( Constant( boolType->clone(), "0" ) ) );
371
372 // generate body of if
373 CompoundStmt * initStmts = new CompoundStmt( noLabels );
374 std::list< Statement * > & body = initStmts->get_kids();
375 body.push_back( ctor );
376 body.push_back( new DeclStmt( noLabels, dtorCaller ) );
377 body.push_back( new ExprStmt( noLabels, callAtexit ) );
378 body.push_back( new ExprStmt( noLabels, setTrue ) );
379
380 // put it all together
381 IfStmt * ifStmt = new IfStmt( noLabels, new VariableExpr( isUninitializedVar ), initStmts, 0 );
382 stmtsToAddAfter.push_back( new DeclStmt( noLabels, isUninitializedVar ) );
383 stmtsToAddAfter.push_back( ifStmt );
384 } else {
385 stmtsToAddAfter.push_back( ctor );
386 dtorStmts.back().push_front( ctorInit->get_dtor() );
387 }
388 objDecl->set_init( NULL );
389 ctorInit->set_ctor( NULL );
390 ctorInit->set_dtor( NULL ); // xxx - only destruct when constructing? Probably not?
391 } else if ( Initializer * init = ctorInit->get_init() ) {
392 objDecl->set_init( init );
393 ctorInit->set_init( NULL );
394 } else {
395 // no constructor and no initializer, which is okay
396 objDecl->set_init( NULL );
397 }
398 delete ctorInit;
399 }
400 return objDecl;
401 }
402
403 namespace {
404 template<typename Iterator, typename OutputIterator>
405 void insertDtors( Iterator begin, Iterator end, OutputIterator out ) {
406 for ( Iterator it = begin ; it != end ; ++it ) {
407 // remove if instrinsic destructor statement. Note that this is only called
408 // on lists of implicit dtors, so if the user manually calls an intrinsic
409 // dtor then the call must (and will) still be generated since the argument
410 // may contain side effects.
411 if ( ! isInstrinsicSingleArgCallStmt( *it ) ) {
412 // don't need to call intrinsic dtor, because it does nothing, but
413 // non-intrinsic dtors must be called
414 *out++ = (*it)->clone();
415 }
416 }
417 }
418 }
419
420 CompoundStmt * FixInit::mutate( CompoundStmt * compoundStmt ) {
421 // mutate statements - this will also populate dtorStmts list.
422 // don't want to dump all destructors when block is left,
423 // just the destructors associated with variables defined in this block,
424 // so push a new list to the top of the stack so that we can differentiate scopes
425 dtorStmts.push_back( std::list<Statement *>() );
426
427 compoundStmt = PolyMutator::mutate( compoundStmt );
428 std::list< Statement * > & statements = compoundStmt->get_kids();
429
430 insertDtors( dtorStmts.back().begin(), dtorStmts.back().end(), back_inserter( statements ) );
431
432 deleteAll( dtorStmts.back() );
433 dtorStmts.pop_back();
434 return compoundStmt;
435 }
436
437 Statement * FixInit::mutate( ReturnStmt * returnStmt ) {
438 for ( std::list< std::list< Statement * > >::reverse_iterator list = dtorStmts.rbegin(); list != dtorStmts.rend(); ++list ) {
439 insertDtors( list->begin(), list->end(), back_inserter( stmtsToAdd ) );
440 }
441 return Mutator::mutate( returnStmt );
442 }
443
444 Statement * FixInit::mutate( BranchStmt * branchStmt ) {
445 // TODO: adding to the end of a block isn't sufficient, since
446 // return/break/goto should trigger destructor when block is left.
447 switch( branchStmt->get_type() ) {
448 case BranchStmt::Continue:
449 case BranchStmt::Break:
450 insertDtors( dtorStmts.back().begin(), dtorStmts.back().end(), back_inserter( stmtsToAdd ) );
451 break;
452 case BranchStmt::Goto:
453 // xxx
454 // if goto leaves a block, generate dtors for every block it leaves
455 // if goto is in same block but earlier statement, destruct every object that was defined after the statement
456 break;
457 default:
458 assert( false );
459 }
460 return Mutator::mutate( branchStmt );
461 }
462
463
464} // namespace InitTweak
465
466// Local Variables: //
467// tab-width: 4 //
468// mode: c++ //
469// compile-command: "make install" //
470// End: //
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