1 //===- LiveVariables.h - Live Variable Analysis for Source CFGs -*- C++ --*-// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements Live Variables analysis for source-level CFGs. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #ifndef LLVM_CLANG_ANALYSIS_ANALYSES_LIVEVARIABLES_H 14 #define LLVM_CLANG_ANALYSIS_ANALYSES_LIVEVARIABLES_H 15 16 #include "clang/AST/Decl.h" 17 #include "clang/Analysis/AnalysisDeclContext.h" 18 #include "llvm/ADT/ImmutableSet.h" 19 20 namespace clang { 21 22 class CFG; 23 class CFGBlock; 24 class Stmt; 25 class DeclRefExpr; 26 class SourceManager; 27 28 class LiveVariables : public ManagedAnalysis { 29 public: 30 class LivenessValues { 31 public: 32 33 llvm::ImmutableSet<const Stmt *> liveStmts; 34 llvm::ImmutableSet<const VarDecl *> liveDecls; 35 llvm::ImmutableSet<const BindingDecl *> liveBindings; 36 37 bool equals(const LivenessValues &V) const; 38 39 LivenessValues() 40 : liveStmts(nullptr), liveDecls(nullptr), liveBindings(nullptr) {} 41 42 LivenessValues(llvm::ImmutableSet<const Stmt *> LiveStmts, 43 llvm::ImmutableSet<const VarDecl *> LiveDecls, 44 llvm::ImmutableSet<const BindingDecl *> LiveBindings) 45 : liveStmts(LiveStmts), liveDecls(LiveDecls), 46 liveBindings(LiveBindings) {} 47 48 bool isLive(const Stmt *S) const; 49 bool isLive(const VarDecl *D) const; 50 51 friend class LiveVariables; 52 }; 53 54 class Observer { 55 virtual void anchor(); 56 public: 57 virtual ~Observer() {} 58 59 /// A callback invoked right before invoking the 60 /// liveness transfer function on the given statement. 61 virtual void observeStmt(const Stmt *S, 62 const CFGBlock *currentBlock, 63 const LivenessValues& V) {} 64 65 /// Called when the live variables analysis registers 66 /// that a variable is killed. 67 virtual void observerKill(const DeclRefExpr *DR) {} 68 }; 69 70 ~LiveVariables() override; 71 72 /// Compute the liveness information for a given CFG. 73 static LiveVariables *computeLiveness(AnalysisDeclContext &analysisContext, 74 bool killAtAssign); 75 76 /// Return true if a variable is live at the end of a 77 /// specified block. 78 bool isLive(const CFGBlock *B, const VarDecl *D); 79 80 /// Returns true if a variable is live at the beginning of the 81 /// the statement. This query only works if liveness information 82 /// has been recorded at the statement level (see runOnAllBlocks), and 83 /// only returns liveness information for block-level expressions. 84 bool isLive(const Stmt *S, const VarDecl *D); 85 86 /// Returns true the block-level expression "value" is live 87 /// before the given block-level expression (see runOnAllBlocks). 88 bool isLive(const Stmt *Loc, const Stmt *StmtVal); 89 90 /// Print to stderr the variable liveness information associated with 91 /// each basic block. 92 void dumpBlockLiveness(const SourceManager &M); 93 94 /// Print to stderr the statement liveness information associated with 95 /// each basic block. 96 void dumpStmtLiveness(const SourceManager &M); 97 98 void runOnAllBlocks(Observer &obs); 99 100 static LiveVariables *create(AnalysisDeclContext &analysisContext) { 101 return computeLiveness(analysisContext, true); 102 } 103 104 static const void *getTag(); 105 106 private: 107 LiveVariables(void *impl); 108 void *impl; 109 }; 110 111 class RelaxedLiveVariables : public LiveVariables { 112 public: 113 static LiveVariables *create(AnalysisDeclContext &analysisContext) { 114 return computeLiveness(analysisContext, false); 115 } 116 117 static const void *getTag(); 118 }; 119 120 } // end namespace clang 121 122 #endif 123