[b8ab91a] | 1 | // |
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| 2 | // Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo |
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| 3 | // |
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| 4 | // The contents of this file are covered under the licence agreement in the |
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| 5 | // file "LICENCE" distributed with Cforall. |
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| 6 | // |
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[817bb3c] | 7 | // MultiLevelExit.cpp -- Replaces CFA's local control flow with C's versions. |
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[b8ab91a] | 8 | // |
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| 9 | // Author : Andrew Beach |
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| 10 | // Created On : Mon Nov 1 13:48:00 2021 |
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[400b8be] | 11 | // Last Modified By : Andrew Beach |
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[553f032f] | 12 | // Last Modified On : Fri Sep 8 17:04:00 2023 |
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| 13 | // Update Count : 36 |
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[b8ab91a] | 14 | // |
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| 15 | |
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| 16 | #include "MultiLevelExit.hpp" |
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| 17 | |
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[83fd57d] | 18 | #include <set> |
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| 19 | |
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[b8ab91a] | 20 | #include "AST/Pass.hpp" |
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| 21 | #include "AST/Stmt.hpp" |
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[83fd57d] | 22 | #include "LabelGenerator.hpp" |
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[b8ab91a] | 23 | |
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[66daee4] | 24 | using namespace std; |
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| 25 | using namespace ast; |
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[b8ab91a] | 26 | |
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| 27 | namespace ControlStruct { |
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[4a40fca7] | 28 | |
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| 29 | namespace { |
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| 30 | |
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[553f032f] | 31 | /// The return context is used to remember if returns are allowed and if |
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| 32 | /// not, why not. It is the nearest local control flow blocking construct. |
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| 33 | enum ReturnContext { |
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| 34 | MayReturn, |
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| 35 | InTryWithHandler, |
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| 36 | InResumeHandler, |
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| 37 | InTerminateHandler, |
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| 38 | InFinally, |
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| 39 | }; |
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| 40 | |
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[b8ab91a] | 41 | class Entry { |
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[66daee4] | 42 | public: |
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| 43 | const Stmt * stmt; |
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| 44 | private: |
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[b8ab91a] | 45 | // Organized like a manual ADT. Avoids creating a bunch of dead data. |
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| 46 | struct Target { |
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[66daee4] | 47 | Label label; |
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[b8ab91a] | 48 | bool used = false; |
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[66daee4] | 49 | Target( const Label & label ) : label( label ) {} |
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[4a40fca7] | 50 | Target() : label( CodeLocation(), "" ) {} |
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[b8ab91a] | 51 | }; |
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| 52 | Target firstTarget; |
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| 53 | Target secondTarget; |
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| 54 | |
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| 55 | enum Kind { |
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[400b8be] | 56 | ForStmtK, WhileDoStmtK, CompoundStmtK, IfStmtK, CaseClauseK, SwitchStmtK, TryStmtK |
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[b8ab91a] | 57 | } kind; |
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| 58 | |
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| 59 | bool fallDefaultValid = true; |
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| 60 | |
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[66daee4] | 61 | static Label & useTarget( Target & target ) { |
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[b8ab91a] | 62 | target.used = true; |
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| 63 | return target.label; |
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| 64 | } |
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[66daee4] | 65 | public: |
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| 66 | Entry( const ForStmt * stmt, Label breakExit, Label contExit ) : |
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| 67 | stmt( stmt ), firstTarget( breakExit ), secondTarget( contExit ), kind( ForStmtK ) {} |
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[3b0bc16] | 68 | Entry( const WhileDoStmt * stmt, Label breakExit, Label contExit ) : |
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| 69 | stmt( stmt ), firstTarget( breakExit ), secondTarget( contExit ), kind( WhileDoStmtK ) {} |
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[66daee4] | 70 | Entry( const CompoundStmt *stmt, Label breakExit ) : |
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| 71 | stmt( stmt ), firstTarget( breakExit ), secondTarget(), kind( CompoundStmtK ) {} |
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| 72 | Entry( const IfStmt *stmt, Label breakExit ) : |
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| 73 | stmt( stmt ), firstTarget( breakExit ), secondTarget(), kind( IfStmtK ) {} |
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[400b8be] | 74 | Entry( const CaseClause *, const CompoundStmt *stmt, Label fallExit ) : |
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| 75 | stmt( stmt ), firstTarget( fallExit ), secondTarget(), kind( CaseClauseK ) {} |
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[66daee4] | 76 | Entry( const SwitchStmt *stmt, Label breakExit, Label fallDefaultExit ) : |
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| 77 | stmt( stmt ), firstTarget( breakExit ), secondTarget( fallDefaultExit ), kind( SwitchStmtK ) {} |
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| 78 | Entry( const TryStmt *stmt, Label breakExit ) : |
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| 79 | stmt( stmt ), firstTarget( breakExit ), secondTarget(), kind( TryStmtK ) {} |
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| 80 | |
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[3b0bc16] | 81 | bool isContTarget() const { return kind <= WhileDoStmtK; } |
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[400b8be] | 82 | bool isBreakTarget() const { return kind != CaseClauseK; } |
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| 83 | bool isFallTarget() const { return kind == CaseClauseK; } |
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[66daee4] | 84 | bool isFallDefaultTarget() const { return kind == SwitchStmtK; } |
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[b8ab91a] | 85 | |
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[3e5db5b4] | 86 | // These routines set a target as being "used" by a BranchStmt |
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[3b0bc16] | 87 | Label useContExit() { assert( kind <= WhileDoStmtK ); return useTarget(secondTarget); } |
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[400b8be] | 88 | Label useBreakExit() { assert( kind != CaseClauseK ); return useTarget(firstTarget); } |
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| 89 | Label useFallExit() { assert( kind == CaseClauseK ); return useTarget(firstTarget); } |
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[66daee4] | 90 | Label useFallDefaultExit() { assert( kind == SwitchStmtK ); return useTarget(secondTarget); } |
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[b8ab91a] | 91 | |
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[3e5db5b4] | 92 | // These routines check if a specific label for a statement is used by a BranchStmt |
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[3b0bc16] | 93 | bool isContUsed() const { assert( kind <= WhileDoStmtK ); return secondTarget.used; } |
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[400b8be] | 94 | bool isBreakUsed() const { assert( kind != CaseClauseK ); return firstTarget.used; } |
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| 95 | bool isFallUsed() const { assert( kind == CaseClauseK ); return firstTarget.used; } |
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[66daee4] | 96 | bool isFallDefaultUsed() const { assert( kind == SwitchStmtK ); return secondTarget.used; } |
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[b8ab91a] | 97 | void seenDefault() { fallDefaultValid = false; } |
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| 98 | bool isFallDefaultValid() const { return fallDefaultValid; } |
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| 99 | }; |
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| 100 | |
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[66daee4] | 101 | // Helper predicates used in find_if calls (it doesn't take methods): |
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[b8ab91a] | 102 | bool isBreakTarget( const Entry & entry ) { |
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| 103 | return entry.isBreakTarget(); |
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| 104 | } |
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| 105 | |
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| 106 | bool isContinueTarget( const Entry & entry ) { |
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| 107 | return entry.isContTarget(); |
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| 108 | } |
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| 109 | |
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| 110 | bool isFallthroughTarget( const Entry & entry ) { |
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| 111 | return entry.isFallTarget(); |
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| 112 | } |
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| 113 | |
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| 114 | bool isFallthroughDefaultTarget( const Entry & entry ) { |
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| 115 | return entry.isFallDefaultTarget(); |
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| 116 | } |
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| 117 | |
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[817bb3c] | 118 | struct MultiLevelExitCore final : |
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[66daee4] | 119 | public WithVisitorRef<MultiLevelExitCore>, |
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| 120 | public WithShortCircuiting, public WithGuards { |
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[cb921d4] | 121 | MultiLevelExitCore( const LabelToStmt & lt ); |
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[b8ab91a] | 122 | |
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[66daee4] | 123 | void previsit( const FunctionDecl * ); |
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| 124 | |
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| 125 | const CompoundStmt * previsit( const CompoundStmt * ); |
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| 126 | const BranchStmt * postvisit( const BranchStmt * ); |
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[3b0bc16] | 127 | void previsit( const WhileDoStmt * ); |
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| 128 | const WhileDoStmt * postvisit( const WhileDoStmt * ); |
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[66daee4] | 129 | void previsit( const ForStmt * ); |
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| 130 | const ForStmt * postvisit( const ForStmt * ); |
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[400b8be] | 131 | const CaseClause * previsit( const CaseClause * ); |
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[66daee4] | 132 | void previsit( const IfStmt * ); |
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| 133 | const IfStmt * postvisit( const IfStmt * ); |
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| 134 | void previsit( const SwitchStmt * ); |
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| 135 | const SwitchStmt * postvisit( const SwitchStmt * ); |
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| 136 | void previsit( const ReturnStmt * ); |
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| 137 | void previsit( const TryStmt * ); |
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| 138 | void postvisit( const TryStmt * ); |
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[553f032f] | 139 | void previsit( const CatchClause * ); |
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[400b8be] | 140 | void previsit( const FinallyClause * ); |
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[66daee4] | 141 | |
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| 142 | const Stmt * mutateLoop( const Stmt * body, Entry& ); |
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[b8ab91a] | 143 | |
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[817bb3c] | 144 | const LabelToStmt & target_table; |
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[66daee4] | 145 | set<Label> fallthrough_labels; |
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| 146 | vector<Entry> enclosing_control_structures; |
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| 147 | Label break_label; |
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[553f032f] | 148 | ReturnContext ret_context; |
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[b8ab91a] | 149 | |
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| 150 | template<typename LoopNode> |
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| 151 | void prehandleLoopStmt( const LoopNode * loopStmt ); |
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| 152 | template<typename LoopNode> |
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| 153 | const LoopNode * posthandleLoopStmt( const LoopNode * loopStmt ); |
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| 154 | |
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[66daee4] | 155 | list<ptr<Stmt>> fixBlock( |
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| 156 | const list<ptr<Stmt>> & kids, bool caseClause ); |
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[b8ab91a] | 157 | |
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[553f032f] | 158 | void enterSealedContext( ReturnContext ); |
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| 159 | |
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[817bb3c] | 160 | template<typename UnaryPredicate> |
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| 161 | auto findEnclosingControlStructure( UnaryPredicate pred ) { |
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[66daee4] | 162 | return find_if( enclosing_control_structures.rbegin(), |
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| 163 | enclosing_control_structures.rend(), pred ); |
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[817bb3c] | 164 | } |
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| 165 | }; |
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[b8ab91a] | 166 | |
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[0577df2] | 167 | NullStmt * labelledNullStmt( const CodeLocation & cl, const Label & label ) { |
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[66daee4] | 168 | return new NullStmt( cl, vector<Label>{ label } ); |
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[b8ab91a] | 169 | } |
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| 170 | |
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[cb921d4] | 171 | MultiLevelExitCore::MultiLevelExitCore( const LabelToStmt & lt ) : |
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| 172 | target_table( lt ), break_label( CodeLocation(), "" ), |
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[553f032f] | 173 | ret_context( ReturnContext::MayReturn ) |
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[b8ab91a] | 174 | {} |
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| 175 | |
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[66daee4] | 176 | void MultiLevelExitCore::previsit( const FunctionDecl * ) { |
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[b8ab91a] | 177 | visit_children = false; |
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| 178 | } |
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| 179 | |
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[66daee4] | 180 | const CompoundStmt * MultiLevelExitCore::previsit( |
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[0577df2] | 181 | const CompoundStmt * stmt ) { |
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[b8ab91a] | 182 | visit_children = false; |
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[3e5db5b4] | 183 | |
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| 184 | // if the stmt is labelled then generate a label to check in postvisit if the label is used |
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[2f52b18] | 185 | bool isLabeled = ! stmt->labels.empty(); |
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[b8ab91a] | 186 | if ( isLabeled ) { |
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[66daee4] | 187 | Label breakLabel = newLabel( "blockBreak", stmt ); |
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[b8ab91a] | 188 | enclosing_control_structures.emplace_back( stmt, breakLabel ); |
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| 189 | GuardAction( [this]() { enclosing_control_structures.pop_back(); } ); |
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| 190 | } |
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| 191 | |
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[66daee4] | 192 | auto mutStmt = mutate( stmt ); |
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[b8ab91a] | 193 | // A child statement may set the break label. |
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[891f707] | 194 | mutStmt->kids = fixBlock( stmt->kids, false ); |
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[b8ab91a] | 195 | |
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| 196 | if ( isLabeled ) { |
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[2f52b18] | 197 | assert( ! enclosing_control_structures.empty() ); |
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[b8ab91a] | 198 | Entry & entry = enclosing_control_structures.back(); |
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[2f52b18] | 199 | if ( ! entry.useBreakExit().empty() ) { |
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[b8ab91a] | 200 | break_label = entry.useBreakExit(); |
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| 201 | } |
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| 202 | } |
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| 203 | return mutStmt; |
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| 204 | } |
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| 205 | |
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[0577df2] | 206 | size_t getUnusedIndex( const Stmt * stmt, const Label & originalTarget ) { |
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[b8ab91a] | 207 | const size_t size = stmt->labels.size(); |
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| 208 | |
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[66daee4] | 209 | // If the label is empty, do not add unused attribute. |
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| 210 | if ( originalTarget.empty() ) return size; |
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[b8ab91a] | 211 | |
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| 212 | // Search for a label that matches the originalTarget. |
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| 213 | for ( size_t i = 0 ; i < size ; ++i ) { |
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[66daee4] | 214 | const Label & label = stmt->labels[i]; |
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[b8ab91a] | 215 | if ( label == originalTarget ) { |
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[66daee4] | 216 | for ( const Attribute * attr : label.attributes ) { |
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[b8ab91a] | 217 | if ( attr->name == "unused" ) return size; |
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| 218 | } |
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| 219 | return i; |
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| 220 | } |
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| 221 | } |
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[6180274] | 222 | assertf( false, "CFA internal error: could not find label '%s' on statement %s", |
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[66daee4] | 223 | originalTarget.name.c_str(), toString( stmt ).c_str() ); |
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[b8ab91a] | 224 | } |
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| 225 | |
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[0577df2] | 226 | const Stmt * addUnused( const Stmt * stmt, const Label & originalTarget ) { |
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[b8ab91a] | 227 | size_t i = getUnusedIndex( stmt, originalTarget ); |
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| 228 | if ( i == stmt->labels.size() ) { |
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| 229 | return stmt; |
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| 230 | } |
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[66daee4] | 231 | Stmt * mutStmt = mutate( stmt ); |
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| 232 | mutStmt->labels[i].attributes.push_back( new Attribute( "unused" ) ); |
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[b8ab91a] | 233 | return mutStmt; |
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| 234 | } |
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| 235 | |
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[3e5db5b4] | 236 | // This routine updates targets on enclosing control structures to indicate which |
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| 237 | // label is used by the BranchStmt that is passed |
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[66daee4] | 238 | const BranchStmt * MultiLevelExitCore::postvisit( const BranchStmt * stmt ) { |
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| 239 | vector<Entry>::reverse_iterator targetEntry = |
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[b8ab91a] | 240 | enclosing_control_structures.rend(); |
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[3e5db5b4] | 241 | |
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| 242 | // Labels on different stmts require different approaches to access |
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[b8ab91a] | 243 | switch ( stmt->kind ) { |
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[491bb81] | 244 | case BranchStmt::Goto: |
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[b8ab91a] | 245 | return stmt; |
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[491bb81] | 246 | case BranchStmt::Continue: |
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| 247 | case BranchStmt::Break: { |
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| 248 | bool isContinue = stmt->kind == BranchStmt::Continue; |
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| 249 | // Handle unlabeled break and continue. |
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| 250 | if ( stmt->target.empty() ) { |
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| 251 | if ( isContinue ) { |
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| 252 | targetEntry = findEnclosingControlStructure( isContinueTarget ); |
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| 253 | } else { |
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| 254 | if ( enclosing_control_structures.empty() ) { |
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[66daee4] | 255 | SemanticError( stmt->location, |
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| 256 | "'break' outside a loop, 'switch', or labelled block" ); |
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[491bb81] | 257 | } |
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| 258 | targetEntry = findEnclosingControlStructure( isBreakTarget ); |
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| 259 | } |
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| 260 | // Handle labeled break and continue. |
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| 261 | } else { |
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| 262 | // Lookup label in table to find attached control structure. |
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| 263 | targetEntry = findEnclosingControlStructure( |
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| 264 | [ targetStmt = target_table.at(stmt->target) ](auto entry){ |
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[66daee4] | 265 | return entry.stmt == targetStmt; |
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[491bb81] | 266 | } ); |
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| 267 | } |
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| 268 | // Ensure that selected target is valid. |
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| 269 | if ( targetEntry == enclosing_control_structures.rend() || ( isContinue && ! isContinueTarget( *targetEntry ) ) ) { |
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| 270 | SemanticError( stmt->location, toString( (isContinue ? "'continue'" : "'break'"), |
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[66daee4] | 271 | " target must be an enclosing ", (isContinue ? "loop: " : "control structure: "), |
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| 272 | stmt->originalTarget ) ); |
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[491bb81] | 273 | } |
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| 274 | break; |
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| 275 | } |
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| 276 | // handle fallthrough in case/switch stmts |
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| 277 | case BranchStmt::FallThrough: { |
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| 278 | targetEntry = findEnclosingControlStructure( isFallthroughTarget ); |
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| 279 | // Check that target is valid. |
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| 280 | if ( targetEntry == enclosing_control_structures.rend() ) { |
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| 281 | SemanticError( stmt->location, "'fallthrough' must be enclosed in a 'switch' or 'choose'" ); |
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| 282 | } |
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| 283 | if ( ! stmt->target.empty() ) { |
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| 284 | // Labelled fallthrough: target must be a valid fallthough label. |
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| 285 | if ( ! fallthrough_labels.count( stmt->target ) ) { |
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| 286 | SemanticError( stmt->location, toString( "'fallthrough' target must be a later case statement: ", |
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[66daee4] | 287 | stmt->originalTarget ) ); |
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[491bb81] | 288 | } |
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| 289 | return new BranchStmt( stmt->location, BranchStmt::Goto, stmt->originalTarget ); |
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| 290 | } |
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| 291 | break; |
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| 292 | } |
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| 293 | case BranchStmt::FallThroughDefault: { |
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| 294 | targetEntry = findEnclosingControlStructure( isFallthroughDefaultTarget ); |
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| 295 | |
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| 296 | // Check if in switch or choose statement. |
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| 297 | if ( targetEntry == enclosing_control_structures.rend() ) { |
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| 298 | SemanticError( stmt->location, "'fallthrough' must be enclosed in a 'switch' or 'choose'" ); |
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| 299 | } |
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| 300 | |
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| 301 | // Check if switch or choose has default clause. |
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| 302 | auto switchStmt = strict_dynamic_cast< const SwitchStmt * >( targetEntry->stmt ); |
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| 303 | bool foundDefault = false; |
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| 304 | for ( auto caseStmt : switchStmt->cases ) { |
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| 305 | if ( caseStmt->isDefault() ) { |
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| 306 | foundDefault = true; |
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| 307 | break; |
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| 308 | } |
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| 309 | } |
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| 310 | if ( ! foundDefault ) { |
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| 311 | SemanticError( stmt->location, "'fallthrough default' must be enclosed in a 'switch' or 'choose'" |
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| 312 | "control structure with a 'default' clause" ); |
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| 313 | } |
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| 314 | break; |
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| 315 | } |
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| 316 | default: |
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[b8ab91a] | 317 | assert( false ); |
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| 318 | } |
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| 319 | |
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[2f52b18] | 320 | // Branch error checks: get the appropriate label name, which is always replaced. |
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[66daee4] | 321 | Label exitLabel( CodeLocation(), "" ); |
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[b8ab91a] | 322 | switch ( stmt->kind ) { |
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[491bb81] | 323 | case BranchStmt::Break: |
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[2f52b18] | 324 | assert( ! targetEntry->useBreakExit().empty() ); |
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[b8ab91a] | 325 | exitLabel = targetEntry->useBreakExit(); |
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| 326 | break; |
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[491bb81] | 327 | case BranchStmt::Continue: |
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[2f52b18] | 328 | assert( ! targetEntry->useContExit().empty() ); |
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[b8ab91a] | 329 | exitLabel = targetEntry->useContExit(); |
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| 330 | break; |
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[491bb81] | 331 | case BranchStmt::FallThrough: |
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[2f52b18] | 332 | assert( ! targetEntry->useFallExit().empty() ); |
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[b8ab91a] | 333 | exitLabel = targetEntry->useFallExit(); |
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| 334 | break; |
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[491bb81] | 335 | case BranchStmt::FallThroughDefault: |
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[2f52b18] | 336 | assert( ! targetEntry->useFallDefaultExit().empty() ); |
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[b8ab91a] | 337 | exitLabel = targetEntry->useFallDefaultExit(); |
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| 338 | // Check that fallthrough default comes before the default clause. |
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[2f52b18] | 339 | if ( ! targetEntry->isFallDefaultValid() ) { |
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[66daee4] | 340 | SemanticError( stmt->location, "'fallthrough default' must precede the 'default' clause" ); |
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[b8ab91a] | 341 | } |
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| 342 | break; |
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[491bb81] | 343 | default: |
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[b8ab91a] | 344 | assert(0); |
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| 345 | } |
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| 346 | |
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| 347 | // Add unused attribute to silence warnings. |
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| 348 | targetEntry->stmt = addUnused( targetEntry->stmt, stmt->originalTarget ); |
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| 349 | |
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[66daee4] | 350 | // Replace with goto to make later passes more uniform. |
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| 351 | return new BranchStmt( stmt->location, BranchStmt::Goto, exitLabel ); |
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[b8ab91a] | 352 | } |
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| 353 | |
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[3b0bc16] | 354 | void MultiLevelExitCore::previsit( const WhileDoStmt * stmt ) { |
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[b8ab91a] | 355 | return prehandleLoopStmt( stmt ); |
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| 356 | } |
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| 357 | |
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[3b0bc16] | 358 | const WhileDoStmt * MultiLevelExitCore::postvisit( const WhileDoStmt * stmt ) { |
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[b8ab91a] | 359 | return posthandleLoopStmt( stmt ); |
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| 360 | } |
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| 361 | |
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[66daee4] | 362 | void MultiLevelExitCore::previsit( const ForStmt * stmt ) { |
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[b8ab91a] | 363 | return prehandleLoopStmt( stmt ); |
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| 364 | } |
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| 365 | |
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[66daee4] | 366 | const ForStmt * MultiLevelExitCore::postvisit( const ForStmt * stmt ) { |
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[b8ab91a] | 367 | return posthandleLoopStmt( stmt ); |
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| 368 | } |
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| 369 | |
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| 370 | // Mimic what the built-in push_front would do anyways. It is O(n). |
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[0577df2] | 371 | void push_front( vector<ptr<Stmt>> & vec, const Stmt * element ) { |
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[b8ab91a] | 372 | vec.emplace_back( nullptr ); |
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| 373 | for ( size_t i = vec.size() - 1 ; 0 < i ; --i ) { |
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[0bd46fd] | 374 | vec[ i ] = std::move( vec[ i - 1 ] ); |
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[b8ab91a] | 375 | } |
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| 376 | vec[ 0 ] = element; |
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| 377 | } |
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| 378 | |
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[400b8be] | 379 | const CaseClause * MultiLevelExitCore::previsit( const CaseClause * stmt ) { |
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[b8ab91a] | 380 | visit_children = false; |
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| 381 | |
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[66daee4] | 382 | // If default, mark seen. |
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[b8ab91a] | 383 | if ( stmt->isDefault() ) { |
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[2f52b18] | 384 | assert( ! enclosing_control_structures.empty() ); |
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[b8ab91a] | 385 | enclosing_control_structures.back().seenDefault(); |
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| 386 | } |
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| 387 | |
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| 388 | // The cond may not exist, but if it does update it now. |
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[400b8be] | 389 | visitor->maybe_accept( stmt, &CaseClause::cond ); |
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[b8ab91a] | 390 | |
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| 391 | // Just save the mutated node for simplicity. |
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[400b8be] | 392 | CaseClause * mutStmt = mutate( stmt ); |
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[b8ab91a] | 393 | |
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[400b8be] | 394 | Label fallLabel = newLabel( "fallThrough", stmt->location ); |
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[66daee4] | 395 | if ( ! mutStmt->stmts.empty() ) { |
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[400b8be] | 396 | // These should already be in a block. |
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| 397 | auto first = mutStmt->stmts.front().get_and_mutate(); |
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| 398 | auto block = strict_dynamic_cast<CompoundStmt *>( first ); |
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| 399 | |
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[b8ab91a] | 400 | // Ensure that the stack isn't corrupted by exceptions in fixBlock. |
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| 401 | auto guard = makeFuncGuard( |
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[400b8be] | 402 | [&](){ enclosing_control_structures.emplace_back( mutStmt, block, fallLabel ); }, |
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[b8ab91a] | 403 | [this](){ enclosing_control_structures.pop_back(); } |
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[66daee4] | 404 | ); |
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[b8ab91a] | 405 | |
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| 406 | block->kids = fixBlock( block->kids, true ); |
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| 407 | |
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| 408 | // Add fallthrough label if necessary. |
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[66daee4] | 409 | assert( ! enclosing_control_structures.empty() ); |
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[b8ab91a] | 410 | Entry & entry = enclosing_control_structures.back(); |
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| 411 | if ( entry.isFallUsed() ) { |
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[400b8be] | 412 | mutStmt->stmts.push_back( labelledNullStmt( block->location, entry.useFallExit() ) ); |
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[b8ab91a] | 413 | } |
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| 414 | } |
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[66daee4] | 415 | assert( ! enclosing_control_structures.empty() ); |
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[b8ab91a] | 416 | Entry & entry = enclosing_control_structures.back(); |
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[66daee4] | 417 | assertf( dynamic_cast< const SwitchStmt * >( entry.stmt ), |
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[6180274] | 418 | "CFA internal error: control structure enclosing a case clause must be a switch, but is: %s", |
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[66daee4] | 419 | toString( entry.stmt ).c_str() ); |
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[b8ab91a] | 420 | if ( mutStmt->isDefault() ) { |
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| 421 | if ( entry.isFallDefaultUsed() ) { |
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| 422 | // Add fallthrough default label if necessary. |
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[2f52b18] | 423 | push_front( mutStmt->stmts, labelledNullStmt( stmt->location, entry.useFallDefaultExit() ) ); |
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[b8ab91a] | 424 | } |
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| 425 | } |
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| 426 | return mutStmt; |
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| 427 | } |
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| 428 | |
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[66daee4] | 429 | void MultiLevelExitCore::previsit( const IfStmt * stmt ) { |
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[2f52b18] | 430 | bool labeledBlock = ! stmt->labels.empty(); |
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[b8ab91a] | 431 | if ( labeledBlock ) { |
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[66daee4] | 432 | Label breakLabel = newLabel( "blockBreak", stmt ); |
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[b8ab91a] | 433 | enclosing_control_structures.emplace_back( stmt, breakLabel ); |
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| 434 | GuardAction( [this](){ enclosing_control_structures.pop_back(); } ); |
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| 435 | } |
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| 436 | } |
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| 437 | |
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[66daee4] | 438 | const IfStmt * MultiLevelExitCore::postvisit( const IfStmt * stmt ) { |
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[2f52b18] | 439 | bool labeledBlock = ! stmt->labels.empty(); |
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[b8ab91a] | 440 | if ( labeledBlock ) { |
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| 441 | auto this_label = enclosing_control_structures.back().useBreakExit(); |
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[2f52b18] | 442 | if ( ! this_label.empty() ) { |
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[b8ab91a] | 443 | break_label = this_label; |
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| 444 | } |
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| 445 | } |
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| 446 | return stmt; |
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| 447 | } |
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| 448 | |
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[400b8be] | 449 | static bool isDefaultCase( const ptr<CaseClause> & caseClause ) { |
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| 450 | return caseClause->isDefault(); |
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[b8ab91a] | 451 | } |
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| 452 | |
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[66daee4] | 453 | void MultiLevelExitCore::previsit( const SwitchStmt * stmt ) { |
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| 454 | Label label = newLabel( "switchBreak", stmt ); |
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[400b8be] | 455 | auto it = find_if( stmt->cases.rbegin(), stmt->cases.rend(), isDefaultCase ); |
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[b8ab91a] | 456 | |
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[400b8be] | 457 | const CaseClause * defaultCase = it != stmt->cases.rend() ? (*it) : nullptr; |
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| 458 | Label defaultLabel = defaultCase ? newLabel( "fallThroughDefault", defaultCase->location ) : Label( stmt->location, "" ); |
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[b8ab91a] | 459 | enclosing_control_structures.emplace_back( stmt, label, defaultLabel ); |
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| 460 | GuardAction( [this]() { enclosing_control_structures.pop_back(); } ); |
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| 461 | |
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[2f52b18] | 462 | // Collect valid labels for fallthrough. It starts with all labels at this level, then remove as each is seen during |
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| 463 | // traversal. |
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[400b8be] | 464 | for ( const CaseClause * caseStmt : stmt->cases ) { |
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[b8ab91a] | 465 | if ( caseStmt->stmts.empty() ) continue; |
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[66daee4] | 466 | auto block = caseStmt->stmts.front().strict_as<CompoundStmt>(); |
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| 467 | for ( const Stmt * stmt : block->kids ) { |
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| 468 | for ( const Label & l : stmt->labels ) { |
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[b8ab91a] | 469 | fallthrough_labels.insert( l ); |
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| 470 | } |
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| 471 | } |
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| 472 | } |
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| 473 | } |
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| 474 | |
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[66daee4] | 475 | const SwitchStmt * MultiLevelExitCore::postvisit( const SwitchStmt * stmt ) { |
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[2f52b18] | 476 | assert( ! enclosing_control_structures.empty() ); |
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[b8ab91a] | 477 | Entry & entry = enclosing_control_structures.back(); |
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| 478 | assert( entry.stmt == stmt ); |
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| 479 | |
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[66daee4] | 480 | // Only run to generate the break label. |
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[b8ab91a] | 481 | if ( entry.isBreakUsed() ) { |
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[2f52b18] | 482 | // To keep the switch statements uniform (all direct children of a SwitchStmt should be CastStmts), append the |
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| 483 | // exit label and break to the last case, create a default case if no cases. |
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[66daee4] | 484 | SwitchStmt * mutStmt = mutate( stmt ); |
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[400b8be] | 485 | if ( mutStmt->cases.empty() ) { |
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| 486 | mutStmt->cases.push_back( new CaseClause( mutStmt->location, nullptr, {} ) ); |
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[b8ab91a] | 487 | } |
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| 488 | |
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[400b8be] | 489 | auto caseStmt = mutStmt->cases.back().get(); |
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[66daee4] | 490 | auto mutCase = mutate( caseStmt ); |
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[400b8be] | 491 | mutStmt->cases.back() = mutCase; |
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[b8ab91a] | 492 | |
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[66daee4] | 493 | Label label( mutCase->location, "breakLabel" ); |
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| 494 | auto branch = new BranchStmt( mutCase->location, BranchStmt::Break, label ); |
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[b8ab91a] | 495 | branch->labels.push_back( entry.useBreakExit() ); |
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| 496 | mutCase->stmts.push_back( branch ); |
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| 497 | |
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| 498 | return mutStmt; |
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| 499 | } |
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| 500 | return stmt; |
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| 501 | } |
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| 502 | |
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[66daee4] | 503 | void MultiLevelExitCore::previsit( const ReturnStmt * stmt ) { |
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[553f032f] | 504 | char const * context; |
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| 505 | switch ( ret_context ) { |
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| 506 | case ReturnContext::MayReturn: |
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| 507 | return; |
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| 508 | case ReturnContext::InTryWithHandler: |
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| 509 | context = "try statement with a catch clause"; |
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| 510 | break; |
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| 511 | case ReturnContext::InResumeHandler: |
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| 512 | context = "catchResume clause"; |
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| 513 | break; |
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| 514 | case ReturnContext::InTerminateHandler: |
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| 515 | context = "catch clause"; |
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| 516 | break; |
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| 517 | case ReturnContext::InFinally: |
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| 518 | context = "finally clause"; |
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| 519 | break; |
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| 520 | default: |
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| 521 | assert(0); |
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[b8ab91a] | 522 | } |
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[553f032f] | 523 | SemanticError( stmt->location, toString( "'return' may not appear in a ", context ) ); |
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[b8ab91a] | 524 | } |
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| 525 | |
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[66daee4] | 526 | void MultiLevelExitCore::previsit( const TryStmt * stmt ) { |
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[2f52b18] | 527 | bool isLabeled = ! stmt->labels.empty(); |
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[b8ab91a] | 528 | if ( isLabeled ) { |
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[66daee4] | 529 | Label breakLabel = newLabel( "blockBreak", stmt ); |
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[b8ab91a] | 530 | enclosing_control_structures.emplace_back( stmt, breakLabel ); |
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| 531 | GuardAction([this](){ enclosing_control_structures.pop_back(); } ); |
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| 532 | } |
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[553f032f] | 533 | |
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| 534 | // Try statements/try blocks are only sealed with a termination handler. |
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| 535 | for ( auto clause : stmt->handlers ) { |
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| 536 | if ( ast::Terminate == clause->kind ) { |
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| 537 | return enterSealedContext( ReturnContext::InTryWithHandler ); |
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| 538 | } |
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| 539 | } |
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[b8ab91a] | 540 | } |
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| 541 | |
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[66daee4] | 542 | void MultiLevelExitCore::postvisit( const TryStmt * stmt ) { |
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[2f52b18] | 543 | bool isLabeled = ! stmt->labels.empty(); |
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[b8ab91a] | 544 | if ( isLabeled ) { |
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| 545 | auto this_label = enclosing_control_structures.back().useBreakExit(); |
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[2f52b18] | 546 | if ( ! this_label.empty() ) { |
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[b8ab91a] | 547 | break_label = this_label; |
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| 548 | } |
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| 549 | } |
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| 550 | } |
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| 551 | |
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[553f032f] | 552 | void MultiLevelExitCore::previsit( const CatchClause * clause ) { |
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| 553 | ReturnContext context = ( ast::Terminate == clause->kind ) |
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| 554 | ? ReturnContext::InTerminateHandler : ReturnContext::InResumeHandler; |
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| 555 | enterSealedContext( context ); |
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| 556 | } |
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| 557 | |
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[400b8be] | 558 | void MultiLevelExitCore::previsit( const FinallyClause * ) { |
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[553f032f] | 559 | enterSealedContext( ReturnContext::InFinally ); |
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[b8ab91a] | 560 | } |
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| 561 | |
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[66daee4] | 562 | const Stmt * MultiLevelExitCore::mutateLoop( |
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| 563 | const Stmt * body, Entry & entry ) { |
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[b8ab91a] | 564 | if ( entry.isBreakUsed() ) { |
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| 565 | break_label = entry.useBreakExit(); |
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| 566 | } |
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| 567 | |
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[3e5db5b4] | 568 | // if continue is used insert a continue label into the back of the body of the loop |
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[b8ab91a] | 569 | if ( entry.isContUsed() ) { |
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[3e5db5b4] | 570 | // { |
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| 571 | // body |
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[4a40fca7] | 572 | // ContinueLabel: ; |
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[3e5db5b4] | 573 | // } |
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[4a40fca7] | 574 | return new CompoundStmt( body->location, { |
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| 575 | body, |
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| 576 | labelledNullStmt( body->location, entry.useContExit() ), |
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| 577 | } ); |
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[b8ab91a] | 578 | } |
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| 579 | |
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| 580 | return body; |
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| 581 | } |
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| 582 | |
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| 583 | template<typename LoopNode> |
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| 584 | void MultiLevelExitCore::prehandleLoopStmt( const LoopNode * loopStmt ) { |
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| 585 | // Remember is loop before going onto mutate the body. |
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| 586 | // The labels will be folded in if they are used. |
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[66daee4] | 587 | Label breakLabel = newLabel( "loopBreak", loopStmt ); |
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| 588 | Label contLabel = newLabel( "loopContinue", loopStmt ); |
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[b8ab91a] | 589 | enclosing_control_structures.emplace_back( loopStmt, breakLabel, contLabel ); |
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[3e5db5b4] | 590 | // labels are added temporarily to see if they are used and then added permanently in postvisit if ther are used |
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| 591 | // children will tag labels as being used during their traversal which occurs before postvisit |
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| 592 | |
---|
| 593 | // GuardAction calls the lambda after the node is done being visited |
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[b8ab91a] | 594 | GuardAction( [this](){ enclosing_control_structures.pop_back(); } ); |
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| 595 | } |
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| 596 | |
---|
| 597 | template<typename LoopNode> |
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| 598 | const LoopNode * MultiLevelExitCore::posthandleLoopStmt( const LoopNode * loopStmt ) { |
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[2f52b18] | 599 | assert( ! enclosing_control_structures.empty() ); |
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[b8ab91a] | 600 | Entry & entry = enclosing_control_structures.back(); |
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| 601 | assert( entry.stmt == loopStmt ); |
---|
| 602 | |
---|
[66daee4] | 603 | // Now check if the labels are used and add them if so. |
---|
[2f52b18] | 604 | return mutate_field( loopStmt, &LoopNode::body, mutateLoop( loopStmt->body, entry ) ); |
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[3e5db5b4] | 605 | // this call to mutate_field compares loopStmt->body and the result of mutateLoop |
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| 606 | // if they are the same the node isn't mutated, if they differ then the new mutated node is returned |
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| 607 | // the stmts will only differ if a label is used |
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[b8ab91a] | 608 | } |
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| 609 | |
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[66daee4] | 610 | list<ptr<Stmt>> MultiLevelExitCore::fixBlock( |
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| 611 | const list<ptr<Stmt>> & kids, bool is_case_clause ) { |
---|
| 612 | // Unfortunately cannot use automatic error collection. |
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[b8ab91a] | 613 | SemanticErrorException errors; |
---|
| 614 | |
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[66daee4] | 615 | list<ptr<Stmt>> ret; |
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[b8ab91a] | 616 | |
---|
| 617 | // Manually visit each child. |
---|
[66daee4] | 618 | for ( const ptr<Stmt> & kid : kids ) { |
---|
[b8ab91a] | 619 | if ( is_case_clause ) { |
---|
| 620 | // Once a label is seen, it's no longer a valid for fallthrough. |
---|
[66daee4] | 621 | for ( const Label & l : kid->labels ) { |
---|
[b8ab91a] | 622 | fallthrough_labels.erase( l ); |
---|
| 623 | } |
---|
| 624 | } |
---|
| 625 | |
---|
[f75e25b] | 626 | ptr<Stmt> else_stmt = nullptr; |
---|
[0577df2] | 627 | const Stmt * loop_kid = nullptr; |
---|
[f75e25b] | 628 | // check if loop node and if so add else clause if it exists |
---|
[0577df2] | 629 | const WhileDoStmt * whilePtr = kid.as<WhileDoStmt>(); |
---|
| 630 | if ( whilePtr && whilePtr->else_ ) { |
---|
[f75e25b] | 631 | else_stmt = whilePtr->else_; |
---|
[0577df2] | 632 | loop_kid = mutate_field( whilePtr, &WhileDoStmt::else_, nullptr ); |
---|
[f75e25b] | 633 | } |
---|
[0577df2] | 634 | const ForStmt * forPtr = kid.as<ForStmt>(); |
---|
| 635 | if ( forPtr && forPtr->else_ ) { |
---|
[f75e25b] | 636 | else_stmt = forPtr->else_; |
---|
[0577df2] | 637 | loop_kid = mutate_field( forPtr, &ForStmt::else_, nullptr ); |
---|
[f75e25b] | 638 | } |
---|
| 639 | |
---|
[b8ab91a] | 640 | try { |
---|
[f75e25b] | 641 | if (else_stmt) ret.push_back( loop_kid->accept( *visitor ) ); |
---|
| 642 | else ret.push_back( kid->accept( *visitor ) ); |
---|
[b8ab91a] | 643 | } catch ( SemanticErrorException & e ) { |
---|
| 644 | errors.append( e ); |
---|
| 645 | } |
---|
| 646 | |
---|
[f75e25b] | 647 | if (else_stmt) ret.push_back(else_stmt); |
---|
[7ad47df] | 648 | |
---|
[2f52b18] | 649 | if ( ! break_label.empty() ) { |
---|
| 650 | ret.push_back( labelledNullStmt( ret.back()->location, break_label ) ); |
---|
[66daee4] | 651 | break_label = Label( CodeLocation(), "" ); |
---|
[b8ab91a] | 652 | } |
---|
| 653 | } |
---|
| 654 | |
---|
[2f52b18] | 655 | if ( ! errors.isEmpty() ) { |
---|
[b8ab91a] | 656 | throw errors; |
---|
| 657 | } |
---|
| 658 | return ret; |
---|
| 659 | } |
---|
| 660 | |
---|
[553f032f] | 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 | |
---|
[4a40fca7] | 667 | } // namespace |
---|
| 668 | |
---|
[66daee4] | 669 | const CompoundStmt * multiLevelExitUpdate( |
---|
[4a40fca7] | 670 | const CompoundStmt * stmt, const LabelToStmt & labelTable ) { |
---|
[b8ab91a] | 671 | // Must start in the body, so FunctionDecls can be a stopping point. |
---|
[66daee4] | 672 | Pass<MultiLevelExitCore> visitor( labelTable ); |
---|
[4a40fca7] | 673 | return stmt->accept( visitor ); |
---|
[b8ab91a] | 674 | } |
---|
[4a40fca7] | 675 | |
---|
[b8ab91a] | 676 | } // namespace ControlStruct |
---|
| 677 | |
---|
| 678 | // Local Variables: // |
---|
| 679 | // tab-width: 4 // |
---|
| 680 | // mode: c++ // |
---|
| 681 | // compile-command: "make install" // |
---|
| 682 | // End: // |
---|