source: src/ControlStruct/MLEMutator.cc@ de31a1d

ADT ast-experimental enum forall-pointer-decay pthread-emulation qualifiedEnum
Last change on this file since de31a1d was 9d6317f, checked in by Andrew Beach <ajbeach@…>, 6 years ago

Added checks for returning from a finally clause. And breaking from a nested function.
  • 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// MLEMutator.cc --
8//
9// Author : Rodolfo G. Esteves
10// Created On : Mon May 18 07:44:20 2015
11// Last Modified By : Andrew Beach
12// Last Modified On : Wed Jan 22 11:50:00 2020
13// Update Count : 223
14//
15
16// NOTE: There are two known subtle differences from the code that uC++ generates for the same input
17// -CFA puts the break label inside at the end of a switch, uC++ puts it after
18// -CFA puts the break label after a block, uC++ puts it inside at the end
19// It is unclear if these differences are important, but if they are, then the fix would go in this file, since this is
20// where these labels are generated.
21
22#include <ext/alloc_traits.h> // for __alloc_traits<>::value_type
23#include <algorithm> // for find, find_if
24#include <cassert> // for assert, assertf
25#include <memory> // for allocator_traits<>::value_...
26
27#include "Common/utility.h" // for toString, operator+
28#include "ControlStruct/LabelGenerator.h" // for LabelGenerator
29#include "MLEMutator.h"
30#include "SynTree/Attribute.h" // for Attribute
31#include "SynTree/Expression.h" // for Expression
32#include "SynTree/Statement.h" // for BranchStmt, CompoundStmt
33
34namespace ControlStruct {
35 MultiLevelExitMutator::~MultiLevelExitMutator() {
36 delete targetTable;
37 targetTable = 0;
38 }
39 namespace {
40 bool isLoop( const MultiLevelExitMutator::Entry & e ) {
41 return dynamic_cast< WhileStmt * >( e.get_controlStructure() )
42 || dynamic_cast< ForStmt * >( e.get_controlStructure() );
43 }
44 bool isSwitch( const MultiLevelExitMutator::Entry & e ) {
45 return dynamic_cast< SwitchStmt *>( e.get_controlStructure() );
46 }
47
48 bool isBreakTarget( const MultiLevelExitMutator::Entry & e ) {
49 return isLoop( e ) || isSwitch( e )
50 || dynamic_cast< CompoundStmt *>( e.get_controlStructure() );
51 }
52 bool isContinueTarget( const MultiLevelExitMutator::Entry & e ) {
53 return isLoop( e );
54 }
55 bool isFallthroughTarget( const MultiLevelExitMutator::Entry & e ) {
56 return dynamic_cast< CaseStmt *>( e.get_controlStructure() );
57 }
58 bool isFallthroughDefaultTarget( const MultiLevelExitMutator::Entry & e ) {
59 return isSwitch( e );
60 }
61 } // namespace
62
63 void MultiLevelExitMutator::premutate( FunctionDecl * ) {
64 visit_children = false;
65 }
66
67 // break labels have to come after the statement they break out of, so mutate a statement, then if they inform us
68 // through the breakLabel field tha they need a place to jump to on a break statement, add the break label to the
69 // body of statements
70 void MultiLevelExitMutator::fixBlock( std::list< Statement * > &kids, bool caseClause ) {
71 SemanticErrorException errors;
72
73 for ( std::list< Statement * >::iterator k = kids.begin(); k != kids.end(); k++ ) {
74 if ( caseClause ) {
75 // once a label is seen, it's no longer a valid fallthrough target
76 for ( Label & l : (*k)->labels ) {
77 fallthroughLabels.erase( l );
78 }
79 }
80
81 // aggregate errors since the PassVisitor mutate loop was unrollled
82 try {
83 *k = (*k)->acceptMutator(*visitor);
84 } catch( SemanticErrorException &e ) {
85 errors.append( e );
86 }
87
88 if ( ! get_breakLabel().empty() ) {
89 std::list< Statement * >::iterator next = k+1;
90 std::list<Label> ls; ls.push_back( get_breakLabel() );
91 kids.insert( next, new NullStmt( ls ) );
92 set_breakLabel("");
93 } // if
94 } // for
95
96 if ( ! errors.isEmpty() ) {
97 throw errors;
98 }
99 }
100
101 void MultiLevelExitMutator::premutate( CompoundStmt *cmpndStmt ) {
102 visit_children = false;
103 bool labeledBlock = !(cmpndStmt->labels.empty());
104 if ( labeledBlock ) {
105 Label brkLabel = generator->newLabel("blockBreak", cmpndStmt);
106 enclosingControlStructures.push_back( Entry( cmpndStmt, brkLabel ) );
107 GuardAction( [this]() { enclosingControlStructures.pop_back(); } );
108 } // if
109
110 // a child statement may set the break label - if they do, attach it to the next statement
111 std::list< Statement * > &kids = cmpndStmt->kids;
112 fixBlock( kids );
113
114 if ( labeledBlock ) {
115 assert( ! enclosingControlStructures.empty() );
116 if ( ! enclosingControlStructures.back().useBreakExit().empty() ) {
117 set_breakLabel( enclosingControlStructures.back().useBreakExit() );
118 } // if
119 } // if
120 }
121
122
123 void addUnused( Statement * stmt, const Label & originalTarget ) {
124 // break/continue without a label doesn't need unused attribute
125 if ( originalTarget == "" ) return;
126 // add unused attribute to the originalTarget of a labelled break/continue
127 for ( Label & l : stmt->get_labels() ) {
128 // find the label to add unused attribute to
129 if ( l == originalTarget ) {
130 for ( Attribute * attr : l.get_attributes() ) {
131 // ensure attribute isn't added twice
132 if ( attr->get_name() == "unused" ) return;
133 }
134 l.get_attributes().push_back( new Attribute( "unused" ) );
135 return;
136 }
137 }
138 assertf( false, "Could not find label '%s' on statement %s",
139 originalTarget.get_name().c_str(), toString( stmt ).c_str() );
140 }
141
142
143 Statement *MultiLevelExitMutator::postmutate( BranchStmt *branchStmt )
144 throw ( SemanticErrorException ) {
145 std::string originalTarget = branchStmt->originalTarget;
146
147 std::list< Entry >::reverse_iterator targetEntry;
148 switch ( branchStmt->get_type() ) {
149 case BranchStmt::Goto:
150 return branchStmt;
151 case BranchStmt::Continue:
152 case BranchStmt::Break: {
153 bool isContinue = branchStmt->get_type() == BranchStmt::Continue;
154 // unlabeled break/continue
155 if ( branchStmt->get_target() == "" ) {
156 if ( isContinue ) {
157 // continue target is outermost loop
158 targetEntry = std::find_if( enclosingControlStructures.rbegin(), enclosingControlStructures.rend(), isContinueTarget );
159 } else {
160 // break target is outermost loop, switch, or block control structure
161 if ( enclosingControlStructures.empty() ) SemanticError( branchStmt->location, "'break' outside a loop, 'switch', or labelled block" );
162 targetEntry = std::find_if( enclosingControlStructures.rbegin(), enclosingControlStructures.rend(), isBreakTarget );
163 } // if
164 } else {
165 // labeled break/continue - lookup label in table to find attached control structure
166 targetEntry = std::find( enclosingControlStructures.rbegin(), enclosingControlStructures.rend(), (*targetTable)[branchStmt->get_target()] );
167 } // if
168 // ensure that selected target is valid
169 if ( targetEntry == enclosingControlStructures.rend() || (isContinue && ! isContinueTarget( *targetEntry ) ) ) {
170 SemanticError( branchStmt->location, toString( (isContinue ? "'continue'" : "'break'"), " target must be an enclosing ", (isContinue ? "loop: " : "control structure: "), originalTarget ) );
171 } // if
172 break;
173 }
174 case BranchStmt::FallThrough:
175 targetEntry = std::find_if( enclosingControlStructures.rbegin(), enclosingControlStructures.rend(), isFallthroughTarget );
176 // ensure that selected target is valid
177 if ( targetEntry == enclosingControlStructures.rend() ) {
178 SemanticError( branchStmt->location, "'fallthrough' must be enclosed in a 'switch' or 'choose'" );
179 } // if
180 if ( branchStmt->get_target() != "" ) {
181 // labelled fallthrough
182 // target must be in the set of valid fallthrough labels
183 if ( ! fallthroughLabels.count( branchStmt->get_target() ) ) {
184 SemanticError( branchStmt->location, toString( "'fallthrough' target must be a later case statement: ", originalTarget ) );
185 }
186 return new BranchStmt( originalTarget, BranchStmt::Goto );
187 }
188 break;
189 case BranchStmt::FallThroughDefault: {
190 // fallthrough default
191 targetEntry = std::find_if( enclosingControlStructures.rbegin(), enclosingControlStructures.rend(), isFallthroughDefaultTarget );
192
193 // ensure that fallthrough is within a switch or choose
194 if ( targetEntry == enclosingControlStructures.rend() ) {
195 SemanticError( branchStmt->location, "'fallthrough' must be enclosed in a 'switch' or 'choose'" );
196 } // if
197
198 // ensure that switch or choose has a default clause
199 SwitchStmt * switchStmt = strict_dynamic_cast< SwitchStmt * >( targetEntry->get_controlStructure() );
200 bool foundDefault = false;
201 for ( Statement * stmt : switchStmt->statements ) {
202 CaseStmt * caseStmt = strict_dynamic_cast< CaseStmt * >( stmt );
203 if ( caseStmt->isDefault() ) {
204 foundDefault = true;
205 } // if
206 } // for
207 if ( ! foundDefault ) {
208 SemanticError( branchStmt->location, "'fallthrough default' must be enclosed in a 'switch' or 'choose' control structure with a 'default' clause" );
209 }
210 break;
211 }
212
213 default:
214 assert( false );
215 } // switch
216
217 // branch error checks, get the appropriate label name and create a goto
218 Label exitLabel;
219 switch ( branchStmt->type ) {
220 case BranchStmt::Break:
221 assert( targetEntry->useBreakExit() != "");
222 exitLabel = targetEntry->useBreakExit();
223 break;
224 case BranchStmt::Continue:
225 assert( targetEntry->useContExit() != "");
226 exitLabel = targetEntry->useContExit();
227 break;
228 case BranchStmt::FallThrough:
229 assert( targetEntry->useFallExit() != "");
230 exitLabel = targetEntry->useFallExit();
231 break;
232 case BranchStmt::FallThroughDefault:
233 assert( targetEntry->useFallDefaultExit() != "");
234 exitLabel = targetEntry->useFallDefaultExit();
235 // check that fallthrough default comes before the default clause
236 if ( ! targetEntry->isFallDefaultValid() ) {
237 SemanticError( branchStmt->location, "'fallthrough default' must precede the 'default' clause" );
238 }
239 break;
240 default:
241 assert(0); // shouldn't be here
242 } // switch
243
244 // add unused attribute to label to silence warnings
245 addUnused( targetEntry->get_controlStructure(), branchStmt->originalTarget );
246
247 // transform break/continue statements into goto to simplify later handling of branches
248 delete branchStmt;
249 return new BranchStmt( exitLabel, BranchStmt::Goto );
250 }
251
252 Statement *MultiLevelExitMutator::mutateLoop( Statement *bodyLoop, Entry &e ) {
253 // only generate these when needed
254 if( !e.isContUsed() && !e.isBreakUsed() ) return bodyLoop;
255
256 // ensure loop body is a block
257 CompoundStmt * newBody = new CompoundStmt();
258 newBody->get_kids().push_back( bodyLoop );
259
260 if ( e.isContUsed() ) {
261 // continue label goes in the body as the last statement
262 std::list< Label > labels; labels.push_back( e.useContExit() );
263 newBody->get_kids().push_back( new NullStmt( labels ) );
264 } // if
265
266 if ( e.isBreakUsed() ) {
267 // break label goes after the loop -- it'll get set by the outer mutator if we do this
268 set_breakLabel( e.useBreakExit() );
269 } // if
270
271 return newBody;
272 }
273
274 template< typename LoopClass >
275 void MultiLevelExitMutator::prehandleLoopStmt( LoopClass * loopStmt ) {
276 // remember this as the most recent enclosing loop, then mutate the body of the loop -- this will determine
277 // whether brkLabel and contLabel are used with branch statements and will recursively do the same to nested
278 // loops
279 Label brkLabel = generator->newLabel("loopBreak", loopStmt);
280 Label contLabel = generator->newLabel("loopContinue", loopStmt);
281 enclosingControlStructures.push_back( Entry( loopStmt, brkLabel, contLabel ) );
282 GuardAction( [this]() { enclosingControlStructures.pop_back(); } );
283 }
284
285 template< typename LoopClass >
286 Statement * MultiLevelExitMutator::posthandleLoopStmt( LoopClass * loopStmt ) {
287 assert( ! enclosingControlStructures.empty() );
288 Entry &e = enclosingControlStructures.back();
289 // sanity check that the enclosing loops have been popped correctly
290 assert ( e == loopStmt );
291
292 // this will take the necessary steps to add definitions of the previous two labels, if they are used.
293 loopStmt->body = mutateLoop( loopStmt->get_body(), e );
294 return loopStmt;
295 }
296
297 void MultiLevelExitMutator::premutate( WhileStmt * whileStmt ) {
298 return prehandleLoopStmt( whileStmt );
299 }
300
301 void MultiLevelExitMutator::premutate( ForStmt * forStmt ) {
302 return prehandleLoopStmt( forStmt );
303 }
304
305 Statement * MultiLevelExitMutator::postmutate( WhileStmt * whileStmt ) {
306 return posthandleLoopStmt( whileStmt );
307 }
308
309 Statement * MultiLevelExitMutator::postmutate( ForStmt * forStmt ) {
310 return posthandleLoopStmt( forStmt );
311 }
312
313 void MultiLevelExitMutator::premutate( IfStmt * ifStmt ) {
314 // generate a label for breaking out of a labeled if
315 bool labeledBlock = !(ifStmt->get_labels().empty());
316 if ( labeledBlock ) {
317 Label brkLabel = generator->newLabel("blockBreak", ifStmt);
318 enclosingControlStructures.push_back( Entry( ifStmt, brkLabel ) );
319 GuardAction( [this]() { enclosingControlStructures.pop_back(); } );
320 } // if
321 }
322
323 Statement * MultiLevelExitMutator::postmutate( IfStmt * ifStmt ) {
324 bool labeledBlock = !(ifStmt->get_labels().empty());
325 if ( labeledBlock ) {
326 if ( ! enclosingControlStructures.back().useBreakExit().empty() ) {
327 set_breakLabel( enclosingControlStructures.back().useBreakExit() );
328 } // if
329 } // if
330 return ifStmt;
331 }
332
333 void MultiLevelExitMutator::premutate( TryStmt * tryStmt ) {
334 // generate a label for breaking out of a labeled if
335 bool labeledBlock = !(tryStmt->get_labels().empty());
336 if ( labeledBlock ) {
337 Label brkLabel = generator->newLabel("blockBreak", tryStmt);
338 enclosingControlStructures.push_back( Entry( tryStmt, brkLabel ) );
339 GuardAction( [this]() { enclosingControlStructures.pop_back(); } );
340 } // if
341 }
342
343 Statement * MultiLevelExitMutator::postmutate( TryStmt * tryStmt ) {
344 bool labeledBlock = !(tryStmt->get_labels().empty());
345 if ( labeledBlock ) {
346 if ( ! enclosingControlStructures.back().useBreakExit().empty() ) {
347 set_breakLabel( enclosingControlStructures.back().useBreakExit() );
348 } // if
349 } // if
350 return tryStmt;
351 }
352
353 void MultiLevelExitMutator::premutate( FinallyStmt * ) {
354 GuardAction([this, old = std::move(enclosingControlStructures)]() {
355 enclosingControlStructures = std::move(old);
356 });
357 enclosingControlStructures = std::list<Entry>();
358 GuardValue( inFinally );
359 inFinally = true;
360 }
361
362 void MultiLevelExitMutator::premutate( ReturnStmt *returnStmt ) {
363 if ( inFinally ) {
364 SemanticError( returnStmt->location, "'return' may not appear in a finally clause" );
365 }
366 }
367
368 void MultiLevelExitMutator::premutate( CaseStmt *caseStmt ) {
369 visit_children = false;
370
371 // mark default as seen before visiting its statements to catch default loops
372 if ( caseStmt->isDefault() ) {
373 enclosingControlStructures.back().seenDefault();
374 } // if
375
376 caseStmt->condition = maybeMutate( caseStmt->condition, *visitor );
377 Label fallLabel = generator->newLabel( "fallThrough", caseStmt );
378 {
379 // ensure that stack isn't corrupted by exceptions in fixBlock
380 auto guard = makeFuncGuard( [&]() { enclosingControlStructures.push_back( Entry( caseStmt, fallLabel ) ); }, [this]() { enclosingControlStructures.pop_back(); } );
381
382 // empty case statement
383 if( ! caseStmt->stmts.empty() ) {
384 // the parser ensures that all statements in a case are grouped into a block
385 CompoundStmt * block = strict_dynamic_cast< CompoundStmt * >( caseStmt->stmts.front() );
386 fixBlock( block->kids, true );
387
388 // add fallthrough label if necessary
389 assert( ! enclosingControlStructures.empty() );
390 if ( enclosingControlStructures.back().isFallUsed() ) {
391 std::list<Label> ls{ enclosingControlStructures.back().useFallExit() };
392 caseStmt->stmts.push_back( new NullStmt( ls ) );
393 } // if
394 } // if
395 }
396 assert( ! enclosingControlStructures.empty() );
397 assertf( dynamic_cast<SwitchStmt *>( enclosingControlStructures.back().get_controlStructure() ), "Control structure enclosing a case clause must be a switch, but is: %s", toCString( enclosingControlStructures.back().get_controlStructure() ) );
398 if ( caseStmt->isDefault() ) {
399 if ( enclosingControlStructures.back().isFallDefaultUsed() ) {
400 // add fallthrough default label if necessary
401 std::list<Label> ls{ enclosingControlStructures.back().useFallDefaultExit() };
402 caseStmt->stmts.push_front( new NullStmt( ls ) );
403 } // if
404 } // if
405 }
406
407 void MultiLevelExitMutator::premutate( SwitchStmt *switchStmt ) {
408 // generate a label for breaking out of a labeled switch
409 Label brkLabel = generator->newLabel("switchBreak", switchStmt);
410 auto it = std::find_if( switchStmt->statements.rbegin(), switchStmt->statements.rend(), [](Statement * stmt) {
411 CaseStmt * caseStmt = strict_dynamic_cast< CaseStmt * >( stmt );
412 return caseStmt->isDefault();
413 });
414 CaseStmt * defaultCase = it != switchStmt->statements.rend() ? strict_dynamic_cast<CaseStmt *>( *it ) : nullptr;
415 Label fallDefaultLabel = defaultCase ? generator->newLabel( "fallThroughDefault", defaultCase ) : "";
416 enclosingControlStructures.push_back( Entry(switchStmt, brkLabel, fallDefaultLabel) );
417 GuardAction( [this]() { enclosingControlStructures.pop_back(); } );
418
419 // Collect valid labels for fallthrough. This is initially all labels at the same level as a case statement.
420 // As labels are seen during traversal, they are removed, since fallthrough is not allowed to jump backwards.
421 for ( Statement * stmt : switchStmt->statements ) {
422 CaseStmt * caseStmt = strict_dynamic_cast< CaseStmt * >( stmt );
423 if ( caseStmt->stmts.empty() ) continue;
424 CompoundStmt * block = dynamic_cast< CompoundStmt * >( caseStmt->stmts.front() );
425 for ( Statement * stmt : block->kids ) {
426 for ( Label & l : stmt->labels ) {
427 fallthroughLabels.insert( l );
428 }
429 }
430 }
431 }
432
433 Statement * MultiLevelExitMutator::postmutate( SwitchStmt * switchStmt ) {
434 Entry &e = enclosingControlStructures.back();
435 assert ( e == switchStmt );
436
437 // only generate break label if labeled break is used
438 if ( e.isBreakUsed() ) {
439 // for the purposes of keeping switch statements uniform (i.e. all statements that are direct children of a
440 // switch should be CastStmts), append the exit label + break to the last case statement; create a default
441 // case if there are no cases
442 std::list< Statement * > &statements = switchStmt->statements;
443 if ( statements.empty() ) {
444 statements.push_back( CaseStmt::makeDefault() );
445 } // if
446
447 if ( CaseStmt * c = dynamic_cast< CaseStmt * >( statements.back() ) ) {
448 Statement * stmt = new BranchStmt( Label("brkLabel"), BranchStmt::Break );
449 stmt->labels.push_back( e.useBreakExit() );
450 c->stmts.push_back( stmt );
451 } else assert(0); // as of this point, all statements of a switch are still CaseStmts
452 } // if
453
454 assert ( enclosingControlStructures.back() == switchStmt );
455 return switchStmt;
456 }
457} // namespace ControlStruct
458
459// Local Variables: //
460// tab-width: 4 //
461// mode: c++ //
462// compile-command: "make install" //
463// End: //
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