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