LiveVariables analysis now uses intersect for the merge of block-level expression liveness information.

The rationale is that a block-level expression cannot be live in a parent block unless it is live in all of the successor blocks.

llvm-svn: 48618

clang/include/clang/Analysis/Support/ExprDeclBitVector.h

@@ -119,7 +119,7 @@ struct DeclBitVector_Types {
     const llvm::BitVector::reference getDeclBit(unsigned i) const {
       return const_cast<llvm::BitVector&>(DeclBV)[i];
     }
-    
+        
     ValTy& operator|=(const ValTy& RHS) {
       assert (sizesEqual(RHS));
       DeclBV |= RHS.DeclBV;
@@ -132,6 +132,14 @@ struct DeclBitVector_Types {
       return *this;
     }
     
+    ValTy& OrDeclBits(const ValTy& RHS) {
+      return operator|=(RHS);
+    }
+    
+    ValTy& AndDeclBits(const ValTy& RHS) {
+      return operator&=(RHS);
+    }
+        
     bool sizesEqual(const ValTy& RHS) const {
       return DeclBV.size() == RHS.DeclBV.size();
     }
@@ -225,6 +233,16 @@ struct ExprDeclBitVector_Types {
       return const_cast<llvm::BitVector&>(ExprBV)[i];
     }
     
+    ValTy& OrExprBits(const ValTy& RHS) {
+      ExprBV |= RHS.ExprBV;
+      return *this;
+    }
+    
+    ValTy& AndExprBits(const ValTy& RHS) {
+      ExprBV &= RHS.ExprBV;
+      return *this;
+    }
+    
     ValTy& operator|=(const ValTy& RHS) {
       assert (sizesEqual(RHS));
       ParentRef(*this) |= ParentRef(RHS);

clang/lib/Analysis/LiveVariables.cpp

@@ -168,8 +168,17 @@ void TransferFuncs::VisitDeclStmt(DeclStmt* DS) {
 //===----------------------------------------------------------------------===//      
 
 namespace {
-typedef ExprDeclBitVector_Types::Union Merge;
-typedef DataflowSolver<LiveVariables,TransferFuncs,Merge> Solver;
+
+struct Merge {
+  typedef ExprDeclBitVector_Types::ValTy ValTy; 
+    
+  void operator()(ValTy& Dst, const ValTy& Src) {
+    Dst.OrDeclBits(Src);
+    Dst.AndExprBits(Src);
+  }
+};
+  
+typedef DataflowSolver<LiveVariables, TransferFuncs, Merge> Solver;
 } // end anonymous namespace
 
 //===----------------------------------------------------------------------===//