source: src/ControlStruct/MultiLevelExit.cpp@ d5efcb7

Last change on this file since d5efcb7 was 0a6d2045, checked in by Andrew Beach <ajbeach@…>, 21 months ago

You can how use local control flow out of 'catch' clauses. Added a test to show that it works.
  • Property mode set to 100644
File size: 23.4 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// MultiLevelExit.cpp -- Replaces CFA's local control flow with C's versions.
8//
9// Author : Andrew Beach
10// Created On : Mon Nov 1 13:48:00 2021
11// Last Modified By : Peter A. Buhr
12// Last Modified On : Thu Dec 14 17:34:12 2023
13// Update Count : 39
14//
15
16#include "MultiLevelExit.hpp"
17
18#include <set>
19
20#include "AST/Pass.hpp"
21#include "AST/Stmt.hpp"
22#include "LabelGenerator.hpp"
23
24using namespace std;
25using namespace ast;
26
27namespace ControlStruct {
28
29namespace {
30
31/// The return context is used to remember if returns are allowed and if
32/// not, why not. It is the nearest local control flow blocking construct.
33enum ReturnContext {
34 MayReturn,
35 InTryWithHandler,
36 InResumeHandler,
37 InFinally,
38};
39
40class Entry {
41 public:
42 const Stmt * stmt;
43 private:
44 // Organized like a manual ADT. Avoids creating a bunch of dead data.
45 struct Target {
46 Label label;
47 bool used = false;
48 Target( const Label & label ) : label( label ) {}
49 Target() : label( CodeLocation(), "" ) {}
50 };
51 Target firstTarget;
52 Target secondTarget;
53
54 enum Kind {
55 ForStmtK, WhileDoStmtK, CompoundStmtK, IfStmtK, CaseClauseK, SwitchStmtK, TryStmtK
56 } kind;
57
58 bool fallDefaultValid = true;
59
60 static Label & useTarget( Target & target ) {
61 target.used = true;
62 return target.label;
63 }
64 public:
65 Entry( const ForStmt * stmt, Label breakExit, Label contExit ) :
66 stmt( stmt ), firstTarget( breakExit ), secondTarget( contExit ), kind( ForStmtK ) {}
67 Entry( const WhileDoStmt * stmt, Label breakExit, Label contExit ) :
68 stmt( stmt ), firstTarget( breakExit ), secondTarget( contExit ), kind( WhileDoStmtK ) {}
69 Entry( const CompoundStmt *stmt, Label breakExit ) :
70 stmt( stmt ), firstTarget( breakExit ), secondTarget(), kind( CompoundStmtK ) {}
71 Entry( const IfStmt *stmt, Label breakExit ) :
72 stmt( stmt ), firstTarget( breakExit ), secondTarget(), kind( IfStmtK ) {}
73 Entry( const CaseClause *, const CompoundStmt *stmt, Label fallExit ) :
74 stmt( stmt ), firstTarget( fallExit ), secondTarget(), kind( CaseClauseK ) {}
75 Entry( const SwitchStmt *stmt, Label breakExit, Label fallDefaultExit ) :
76 stmt( stmt ), firstTarget( breakExit ), secondTarget( fallDefaultExit ), kind( SwitchStmtK ) {}
77 Entry( const TryStmt *stmt, Label breakExit ) :
78 stmt( stmt ), firstTarget( breakExit ), secondTarget(), kind( TryStmtK ) {}
79
80 bool isContTarget() const { return kind <= WhileDoStmtK; }
81 bool isBreakTarget() const { return kind != CaseClauseK; }
82 bool isFallTarget() const { return kind == CaseClauseK; }
83 bool isFallDefaultTarget() const { return kind == SwitchStmtK; }
84
85 // These routines set a target as being "used" by a BranchStmt
86 Label useContExit() { assert( kind <= WhileDoStmtK ); return useTarget(secondTarget); }
87 Label useBreakExit() { assert( kind != CaseClauseK ); return useTarget(firstTarget); }
88 Label useFallExit() { assert( kind == CaseClauseK ); return useTarget(firstTarget); }
89 Label useFallDefaultExit() { assert( kind == SwitchStmtK ); return useTarget(secondTarget); }
90
91 // These routines check if a specific label for a statement is used by a BranchStmt
92 bool isContUsed() const { assert( kind <= WhileDoStmtK ); return secondTarget.used; }
93 bool isBreakUsed() const { assert( kind != CaseClauseK ); return firstTarget.used; }
94 bool isFallUsed() const { assert( kind == CaseClauseK ); return firstTarget.used; }
95 bool isFallDefaultUsed() const { assert( kind == SwitchStmtK ); return secondTarget.used; }
96 void seenDefault() { fallDefaultValid = false; }
97 bool isFallDefaultValid() const { return fallDefaultValid; }
98};
99
100// Helper predicates used in find_if calls (it doesn't take methods):
101bool isBreakTarget( const Entry & entry ) {
102 return entry.isBreakTarget();
103}
104
105bool isContinueTarget( const Entry & entry ) {
106 return entry.isContTarget();
107}
108
109bool isFallthroughTarget( const Entry & entry ) {
110 return entry.isFallTarget();
111}
112
113bool isFallthroughDefaultTarget( const Entry & entry ) {
114 return entry.isFallDefaultTarget();
115}
116
117struct MultiLevelExitCore final :
118 public WithVisitorRef<MultiLevelExitCore>,
119 public WithShortCircuiting, public WithGuards {
120 MultiLevelExitCore( const LabelToStmt & lt );
121
122 void previsit( const FunctionDecl * );
123
124 const CompoundStmt * previsit( const CompoundStmt * );
125 const BranchStmt * postvisit( const BranchStmt * );
126 void previsit( const WhileDoStmt * );
127 const WhileDoStmt * postvisit( const WhileDoStmt * );
128 void previsit( const ForStmt * );
129 const ForStmt * postvisit( const ForStmt * );
130 const CaseClause * previsit( const CaseClause * );
131 void previsit( const IfStmt * );
132 const IfStmt * postvisit( const IfStmt * );
133 void previsit( const SwitchStmt * );
134 const SwitchStmt * postvisit( const SwitchStmt * );
135 void previsit( const ReturnStmt * );
136 void previsit( const TryStmt * );
137 void postvisit( const TryStmt * );
138 void previsit( const CatchClause * );
139 void previsit( const FinallyClause * );
140
141 const Stmt * mutateLoop( const Stmt * body, Entry& );
142
143 const LabelToStmt & target_table;
144 set<Label> fallthrough_labels;
145 vector<Entry> enclosing_control_structures;
146 Label break_label;
147 ReturnContext ret_context;
148
149 template<typename LoopNode>
150 void prehandleLoopStmt( const LoopNode * loopStmt );
151 template<typename LoopNode>
152 const LoopNode * posthandleLoopStmt( const LoopNode * loopStmt );
153
154 list<ptr<Stmt>> fixBlock(
155 const list<ptr<Stmt>> & kids, bool caseClause );
156
157 void enterSealedContext( ReturnContext );
158
159 template<typename UnaryPredicate>
160 auto findEnclosingControlStructure( UnaryPredicate pred ) {
161 return find_if( enclosing_control_structures.rbegin(),
162 enclosing_control_structures.rend(), pred );
163 }
164};
165
166NullStmt * labelledNullStmt( const CodeLocation & cl, const Label & label ) {
167 return new NullStmt( cl, vector<Label>{ label } );
168}
169
170MultiLevelExitCore::MultiLevelExitCore( const LabelToStmt & lt ) :
171 target_table( lt ), break_label( CodeLocation(), "" ),
172 ret_context( ReturnContext::MayReturn )
173{}
174
175void MultiLevelExitCore::previsit( const FunctionDecl * ) {
176 visit_children = false;
177}
178
179const CompoundStmt * MultiLevelExitCore::previsit(
180 const CompoundStmt * stmt ) {
181 visit_children = false;
182
183 // if the stmt is labelled then generate a label to check in postvisit if the label is used
184 bool isLabeled = ! stmt->labels.empty();
185 if ( isLabeled ) {
186 Label breakLabel = newLabel( "blockBreak", stmt );
187 enclosing_control_structures.emplace_back( stmt, breakLabel );
188 GuardAction( [this]() { enclosing_control_structures.pop_back(); } );
189 }
190
191 auto mutStmt = mutate( stmt );
192 // A child statement may set the break label.
193 mutStmt->kids = fixBlock( stmt->kids, false );
194
195 if ( isLabeled ) {
196 assert( ! enclosing_control_structures.empty() );
197 Entry & entry = enclosing_control_structures.back();
198 if ( ! entry.useBreakExit().empty() ) {
199 break_label = entry.useBreakExit();
200 }
201 }
202 return mutStmt;
203}
204
205size_t getUnusedIndex( const Stmt * stmt, const Label & originalTarget ) {
206 const size_t size = stmt->labels.size();
207
208 // If the label is empty, do not add unused attribute.
209 if ( originalTarget.empty() ) return size;
210
211 // Search for a label that matches the originalTarget.
212 for ( size_t i = 0 ; i < size ; ++i ) {
213 const Label & label = stmt->labels[i];
214 if ( label == originalTarget ) {
215 for ( const Attribute * attr : label.attributes ) {
216 if ( attr->name == "unused" ) return size;
217 }
218 return i;
219 }
220 }
221 assertf( false, "CFA internal error: could not find label '%s' on statement %s",
222 originalTarget.name.c_str(), toString( stmt ).c_str() );
223}
224
225const Stmt * addUnused( const Stmt * stmt, const Label & originalTarget ) {
226 size_t i = getUnusedIndex( stmt, originalTarget );
227 if ( i == stmt->labels.size() ) {
228 return stmt;
229 }
230 Stmt * mutStmt = mutate( stmt );
231 mutStmt->labels[i].attributes.push_back( new Attribute( "unused" ) );
232 return mutStmt;
233}
234
235// This routine updates targets on enclosing control structures to indicate which
236// label is used by the BranchStmt that is passed
237const BranchStmt * MultiLevelExitCore::postvisit( const BranchStmt * stmt ) {
238 vector<Entry>::reverse_iterator targetEntry =
239 enclosing_control_structures.rend();
240
241 // Labels on different stmts require different approaches to access
242 switch ( stmt->kind ) {
243 case BranchStmt::Goto:
244 return stmt;
245 case BranchStmt::Continue:
246 case BranchStmt::Break: {
247 bool isContinue = stmt->kind == BranchStmt::Continue;
248 // Handle unlabeled break and continue.
249 if ( stmt->target.empty() ) {
250 if ( isContinue ) {
251 targetEntry = findEnclosingControlStructure( isContinueTarget );
252 } else {
253 if ( enclosing_control_structures.empty() ) {
254 SemanticError( stmt->location,
255 "\"break\" outside a loop, \"switch\", or labelled block" );
256 }
257 targetEntry = findEnclosingControlStructure( isBreakTarget );
258 }
259 // Handle labeled break and continue.
260 } else {
261 // Lookup label in table to find attached control structure.
262 targetEntry = findEnclosingControlStructure(
263 [ targetStmt = target_table.at(stmt->target) ](auto entry){
264 return entry.stmt == targetStmt;
265 } );
266 }
267 // Ensure that selected target is valid.
268 if ( targetEntry == enclosing_control_structures.rend() || ( isContinue && ! isContinueTarget( *targetEntry ) ) ) {
269 SemanticError( stmt->location, toString( (isContinue ? "\"continue\"" : "\"break\""),
270 " target must be an enclosing ", (isContinue ? "loop: " : "control structure: "),
271 stmt->originalTarget ) );
272 }
273 break;
274 }
275 // handle fallthrough in case/switch stmts
276 case BranchStmt::FallThrough: {
277 targetEntry = findEnclosingControlStructure( isFallthroughTarget );
278 // Check that target is valid.
279 if ( targetEntry == enclosing_control_structures.rend() ) {
280 SemanticError( stmt->location, "\"fallthrough\" must be enclosed in a \"switch\" or \"choose\"" );
281 }
282 if ( ! stmt->target.empty() ) {
283 // Labelled fallthrough: target must be a valid fallthough label.
284 if ( ! fallthrough_labels.count( stmt->target ) ) {
285 SemanticError( stmt->location, toString( "\"fallthrough\" target must be a later case statement: ",
286 stmt->originalTarget ) );
287 }
288 return new BranchStmt( stmt->location, BranchStmt::Goto, stmt->originalTarget );
289 }
290 break;
291 }
292 case BranchStmt::FallThroughDefault: {
293 targetEntry = findEnclosingControlStructure( isFallthroughDefaultTarget );
294
295 // Check if in switch or choose statement.
296 if ( targetEntry == enclosing_control_structures.rend() ) {
297 SemanticError( stmt->location, "\"fallthrough\" must be enclosed in a \"switch\" or \"choose\"" );
298 }
299
300 // Check if switch or choose has default clause.
301 auto switchStmt = strict_dynamic_cast< const SwitchStmt * >( targetEntry->stmt );
302 bool foundDefault = false;
303 for ( auto caseStmt : switchStmt->cases ) {
304 if ( caseStmt->isDefault() ) {
305 foundDefault = true;
306 break;
307 }
308 }
309 if ( ! foundDefault ) {
310 SemanticError( stmt->location, "\"fallthrough default\" must be enclosed in a \"switch\" or \"choose\""
311 "control structure with a \"default\" clause" );
312 }
313 break;
314 }
315 default:
316 assert( false );
317 }
318
319 // Branch error checks: get the appropriate label name, which is always replaced.
320 Label exitLabel( CodeLocation(), "" );
321 switch ( stmt->kind ) {
322 case BranchStmt::Break:
323 assert( ! targetEntry->useBreakExit().empty() );
324 exitLabel = targetEntry->useBreakExit();
325 break;
326 case BranchStmt::Continue:
327 assert( ! targetEntry->useContExit().empty() );
328 exitLabel = targetEntry->useContExit();
329 break;
330 case BranchStmt::FallThrough:
331 assert( ! targetEntry->useFallExit().empty() );
332 exitLabel = targetEntry->useFallExit();
333 break;
334 case BranchStmt::FallThroughDefault:
335 assert( ! targetEntry->useFallDefaultExit().empty() );
336 exitLabel = targetEntry->useFallDefaultExit();
337 // Check that fallthrough default comes before the default clause.
338 if ( ! targetEntry->isFallDefaultValid() ) {
339 SemanticError( stmt->location, "\"fallthrough default\" must precede the \"default\" clause" );
340 }
341 break;
342 default:
343 assert(0);
344 }
345
346 // Add unused attribute to silence warnings.
347 targetEntry->stmt = addUnused( targetEntry->stmt, stmt->originalTarget );
348
349 // Replace with goto to make later passes more uniform.
350 return new BranchStmt( stmt->location, BranchStmt::Goto, exitLabel );
351}
352
353void MultiLevelExitCore::previsit( const WhileDoStmt * stmt ) {
354 return prehandleLoopStmt( stmt );
355}
356
357const WhileDoStmt * MultiLevelExitCore::postvisit( const WhileDoStmt * stmt ) {
358 return posthandleLoopStmt( stmt );
359}
360
361void MultiLevelExitCore::previsit( const ForStmt * stmt ) {
362 return prehandleLoopStmt( stmt );
363}
364
365const ForStmt * MultiLevelExitCore::postvisit( const ForStmt * stmt ) {
366 return posthandleLoopStmt( stmt );
367}
368
369// Mimic what the built-in push_front would do anyways. It is O(n).
370void push_front( vector<ptr<Stmt>> & vec, const Stmt * element ) {
371 vec.emplace_back( nullptr );
372 for ( size_t i = vec.size() - 1 ; 0 < i ; --i ) {
373 vec[ i ] = std::move( vec[ i - 1 ] );
374 }
375 vec[ 0 ] = element;
376}
377
378const CaseClause * MultiLevelExitCore::previsit( const CaseClause * stmt ) {
379 visit_children = false;
380
381 // If default, mark seen.
382 if ( stmt->isDefault() ) {
383 assert( ! enclosing_control_structures.empty() );
384 enclosing_control_structures.back().seenDefault();
385 }
386
387 // The cond may not exist, but if it does update it now.
388 visitor->maybe_accept( stmt, &CaseClause::cond );
389
390 // Just save the mutated node for simplicity.
391 CaseClause * mutStmt = mutate( stmt );
392
393 Label fallLabel = newLabel( "fallThrough", stmt->location );
394 if ( ! mutStmt->stmts.empty() ) {
395 // These should already be in a block.
396 auto first = mutStmt->stmts.front().get_and_mutate();
397 auto block = strict_dynamic_cast<CompoundStmt *>( first );
398
399 // Ensure that the stack isn't corrupted by exceptions in fixBlock.
400 auto guard = makeFuncGuard(
401 [&](){ enclosing_control_structures.emplace_back( mutStmt, block, fallLabel ); },
402 [this](){ enclosing_control_structures.pop_back(); }
403 );
404
405 block->kids = fixBlock( block->kids, true );
406
407 // Add fallthrough label if necessary.
408 assert( ! enclosing_control_structures.empty() );
409 Entry & entry = enclosing_control_structures.back();
410 if ( entry.isFallUsed() ) {
411 mutStmt->stmts.push_back( labelledNullStmt( block->location, entry.useFallExit() ) );
412 }
413 }
414 assert( ! enclosing_control_structures.empty() );
415 Entry & entry = enclosing_control_structures.back();
416 assertf( dynamic_cast< const SwitchStmt * >( entry.stmt ),
417 "CFA internal error: control structure enclosing a case clause must be a switch, but is: %s",
418 toString( entry.stmt ).c_str() );
419 if ( mutStmt->isDefault() ) {
420 if ( entry.isFallDefaultUsed() ) {
421 // Add fallthrough default label if necessary.
422 push_front( mutStmt->stmts, labelledNullStmt( stmt->location, entry.useFallDefaultExit() ) );
423 }
424 }
425 return mutStmt;
426}
427
428void MultiLevelExitCore::previsit( const IfStmt * stmt ) {
429 bool labeledBlock = ! stmt->labels.empty();
430 if ( labeledBlock ) {
431 Label breakLabel = newLabel( "blockBreak", stmt );
432 enclosing_control_structures.emplace_back( stmt, breakLabel );
433 GuardAction( [this](){ enclosing_control_structures.pop_back(); } );
434 }
435}
436
437const IfStmt * MultiLevelExitCore::postvisit( const IfStmt * stmt ) {
438 bool labeledBlock = ! stmt->labels.empty();
439 if ( labeledBlock ) {
440 auto this_label = enclosing_control_structures.back().useBreakExit();
441 if ( ! this_label.empty() ) {
442 break_label = this_label;
443 }
444 }
445 return stmt;
446}
447
448static bool isDefaultCase( const ptr<CaseClause> & caseClause ) {
449 return caseClause->isDefault();
450}
451
452void MultiLevelExitCore::previsit( const SwitchStmt * stmt ) {
453 Label label = newLabel( "switchBreak", stmt );
454 auto it = find_if( stmt->cases.rbegin(), stmt->cases.rend(), isDefaultCase );
455
456 const CaseClause * defaultCase = it != stmt->cases.rend() ? (*it) : nullptr;
457 Label defaultLabel = defaultCase ? newLabel( "fallThroughDefault", defaultCase->location ) : Label( stmt->location, "" );
458 enclosing_control_structures.emplace_back( stmt, label, defaultLabel );
459 GuardAction( [this]() { enclosing_control_structures.pop_back(); } );
460
461 // Collect valid labels for fallthrough. It starts with all labels at this level, then remove as each is seen during
462 // traversal.
463 for ( const CaseClause * caseStmt : stmt->cases ) {
464 if ( caseStmt->stmts.empty() ) continue;
465 auto block = caseStmt->stmts.front().strict_as<CompoundStmt>();
466 for ( const Stmt * stmt : block->kids ) {
467 for ( const Label & l : stmt->labels ) {
468 fallthrough_labels.insert( l );
469 }
470 }
471 }
472}
473
474const SwitchStmt * MultiLevelExitCore::postvisit( const SwitchStmt * stmt ) {
475 assert( ! enclosing_control_structures.empty() );
476 Entry & entry = enclosing_control_structures.back();
477 assert( entry.stmt == stmt );
478
479 // Only run to generate the break label.
480 if ( entry.isBreakUsed() ) {
481 // To keep the switch statements uniform (all direct children of a SwitchStmt should be CastStmts), append the
482 // exit label and break to the last case, create a default case if no cases.
483 SwitchStmt * mutStmt = mutate( stmt );
484 if ( mutStmt->cases.empty() ) {
485 mutStmt->cases.push_back( new CaseClause( mutStmt->location, nullptr, {} ) );
486 }
487
488 auto caseStmt = mutStmt->cases.back().get();
489 auto mutCase = mutate( caseStmt );
490 mutStmt->cases.back() = mutCase;
491
492 Label label( mutCase->location, "breakLabel" );
493 auto branch = new BranchStmt( mutCase->location, BranchStmt::Break, label );
494 branch->labels.push_back( entry.useBreakExit() );
495 mutCase->stmts.push_back( branch );
496
497 return mutStmt;
498 }
499 return stmt;
500}
501
502void MultiLevelExitCore::previsit( const ReturnStmt * stmt ) {
503 char const * context;
504 switch ( ret_context ) {
505 case ReturnContext::MayReturn:
506 return;
507 case ReturnContext::InTryWithHandler:
508 context = "try statement with a catch clause";
509 break;
510 case ReturnContext::InResumeHandler:
511 context = "catchResume clause";
512 break;
513 case ReturnContext::InFinally:
514 context = "finally clause";
515 break;
516 default:
517 assert(0);
518 }
519 SemanticError( stmt->location, "\"return\" may not appear in a %s", context );
520}
521
522bool hasTerminate( const TryStmt * stmt ) {
523 for ( auto clause : stmt->handlers ) {
524 if ( ast::Terminate == clause->kind ) return true;
525 }
526 return false;
527}
528
529void MultiLevelExitCore::previsit( const TryStmt * stmt ) {
530 visit_children = false;
531
532 bool isLabeled = ! stmt->labels.empty();
533 if ( isLabeled ) {
534 Label breakLabel = newLabel( "blockBreak", stmt );
535 enclosing_control_structures.emplace_back( stmt, breakLabel );
536 GuardAction([this](){ enclosing_control_structures.pop_back(); } );
537 }
538
539 // Try statements/try blocks are only sealed with a termination handler.
540 if ( hasTerminate( stmt ) ) {
541 // This is just enterSealedContext except scoped to the block.
542 // And that is because the state must change for a single field.
543 ValueGuard< ReturnContext > guard0( ret_context );
544 ret_context = ReturnContext::InTryWithHandler;
545 auto guard = makeFuncGuard( [](){}, [this, old = std::move(enclosing_control_structures)](){ enclosing_control_structures = std::move(old); });
546 enclosing_control_structures = vector<Entry>();
547 visitor->maybe_accept( stmt, &TryStmt::body );
548 } else {
549 visitor->maybe_accept( stmt, &TryStmt::body );
550 }
551
552 visitor->maybe_accept( stmt, &TryStmt::handlers );
553 visitor->maybe_accept( stmt, &TryStmt::finally );
554}
555
556void MultiLevelExitCore::postvisit( const TryStmt * stmt ) {
557 bool isLabeled = ! stmt->labels.empty();
558 if ( isLabeled ) {
559 auto this_label = enclosing_control_structures.back().useBreakExit();
560 if ( ! this_label.empty() ) {
561 break_label = this_label;
562 }
563 }
564}
565
566void MultiLevelExitCore::previsit( const CatchClause * clause ) {
567 if ( ast::Resume == clause->kind ) {
568 enterSealedContext( ReturnContext::InResumeHandler );
569 }
570}
571
572void MultiLevelExitCore::previsit( const FinallyClause * ) {
573 enterSealedContext( ReturnContext::InFinally );
574}
575
576const Stmt * MultiLevelExitCore::mutateLoop(
577 const Stmt * body, Entry & entry ) {
578 if ( entry.isBreakUsed() ) {
579 break_label = entry.useBreakExit();
580 }
581
582 // if continue is used insert a continue label into the back of the body of the loop
583 if ( entry.isContUsed() ) {
584 // {
585 // body
586 // ContinueLabel: ;
587 // }
588 return new CompoundStmt( body->location, {
589 body,
590 labelledNullStmt( body->location, entry.useContExit() ),
591 } );
592 }
593
594 return body;
595}
596
597template<typename LoopNode>
598void MultiLevelExitCore::prehandleLoopStmt( const LoopNode * loopStmt ) {
599 // Remember is loop before going onto mutate the body.
600 // The labels will be folded in if they are used.
601 Label breakLabel = newLabel( "loopBreak", loopStmt );
602 Label contLabel = newLabel( "loopContinue", loopStmt );
603 enclosing_control_structures.emplace_back( loopStmt, breakLabel, contLabel );
604 // labels are added temporarily to see if they are used and then added permanently in postvisit if ther are used
605 // children will tag labels as being used during their traversal which occurs before postvisit
606
607 // GuardAction calls the lambda after the node is done being visited
608 GuardAction( [this](){ enclosing_control_structures.pop_back(); } );
609}
610
611template<typename LoopNode>
612const LoopNode * MultiLevelExitCore::posthandleLoopStmt( const LoopNode * loopStmt ) {
613 assert( ! enclosing_control_structures.empty() );
614 Entry & entry = enclosing_control_structures.back();
615 assert( entry.stmt == loopStmt );
616
617 // Now check if the labels are used and add them if so.
618 return mutate_field( loopStmt, &LoopNode::body, mutateLoop( loopStmt->body, entry ) );
619 // this call to mutate_field compares loopStmt->body and the result of mutateLoop
620 // if they are the same the node isn't mutated, if they differ then the new mutated node is returned
621 // the stmts will only differ if a label is used
622}
623
624list<ptr<Stmt>> MultiLevelExitCore::fixBlock(
625 const list<ptr<Stmt>> & kids, bool is_case_clause ) {
626 // Unfortunately cannot use automatic error collection.
627 SemanticErrorException errors;
628
629 list<ptr<Stmt>> ret;
630
631 // Manually visit each child.
632 for ( const ptr<Stmt> & kid : kids ) {
633 if ( is_case_clause ) {
634 // Once a label is seen, it's no longer a valid for fallthrough.
635 for ( const Label & l : kid->labels ) {
636 fallthrough_labels.erase( l );
637 }
638 }
639
640 ptr<Stmt> else_stmt = nullptr;
641 const Stmt * loop_kid = nullptr;
642 // check if loop node and if so add else clause if it exists
643 const WhileDoStmt * whilePtr = kid.as<WhileDoStmt>();
644 if ( whilePtr && whilePtr->else_ ) {
645 else_stmt = whilePtr->else_;
646 loop_kid = mutate_field( whilePtr, &WhileDoStmt::else_, nullptr );
647 }
648 const ForStmt * forPtr = kid.as<ForStmt>();
649 if ( forPtr && forPtr->else_ ) {
650 else_stmt = forPtr->else_;
651 loop_kid = mutate_field( forPtr, &ForStmt::else_, nullptr );
652 }
653
654 try {
655 if (else_stmt) ret.push_back( loop_kid->accept( *visitor ) );
656 else ret.push_back( kid->accept( *visitor ) );
657 } catch ( SemanticErrorException & e ) {
658 errors.append( e );
659 }
660
661 if (else_stmt) ret.push_back(else_stmt);
662
663 if ( ! break_label.empty() ) {
664 ret.push_back( labelledNullStmt( ret.back()->location, break_label ) );
665 break_label = Label( CodeLocation(), "" );
666 }
667 }
668
669 if ( ! errors.isEmpty() ) {
670 throw errors;
671 }
672 return ret;
673}
674
675void MultiLevelExitCore::enterSealedContext( ReturnContext enter_context ) {
676 GuardAction([this, old = std::move(enclosing_control_structures)](){ enclosing_control_structures = std::move(old); });
677 enclosing_control_structures = vector<Entry>();
678 GuardValue( ret_context ) = enter_context;
679}
680
681} // namespace
682
683const CompoundStmt * multiLevelExitUpdate(
684 const CompoundStmt * stmt, const LabelToStmt & labelTable ) {
685 // Must start in the body, so FunctionDecls can be a stopping point.
686 Pass<MultiLevelExitCore> visitor( labelTable );
687 return stmt->accept( visitor );
688}
689
690} // namespace ControlStruct
691
692// Local Variables: //
693// tab-width: 4 //
694// mode: c++ //
695// compile-command: "make install" //
696// End: //
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