2 files changed, 82 insertions, 19 deletions

diff --git a/lib/Analysis/PseudoConstantAnalysis.cpp b/lib/Analysis/PseudoConstantAnalysis.cpp
index 7a2fa8a8bd..5deabacea4 100644
--- a/lib/Analysis/PseudoConstantAnalysis.cpp
+++ b/lib/Analysis/PseudoConstantAnalysis.cpp
@@ -28,10 +28,12 @@ typedef llvm::SmallPtrSet<const VarDecl*, VARDECL_SET_SIZE> VarDeclSet;
 PseudoConstantAnalysis::PseudoConstantAnalysis(const Stmt *DeclBody) :
       DeclBody(DeclBody), Analyzed(false) {
   NonConstantsImpl = new VarDeclSet;
+  UsedVarsImpl = new VarDeclSet;
 }
 
 PseudoConstantAnalysis::~PseudoConstantAnalysis() {
   delete (VarDeclSet*)NonConstantsImpl;
+  delete (VarDeclSet*)UsedVarsImpl;
 }
 
 // Returns true if the given ValueDecl is never written to in the given DeclBody
@@ -50,9 +52,22 @@ bool PseudoConstantAnalysis::isPseudoConstant(const VarDecl *VD) {
   return !NonConstants->count(VD);
 }
 
+// Returns true if the variable was used (self assignments don't count)
+bool PseudoConstantAnalysis::wasReferenced(const VarDecl *VD) {
+  if (!Analyzed) {
+    RunAnalysis();
+    Analyzed = true;
+  }
+
+  VarDeclSet *UsedVars = (VarDeclSet*)UsedVarsImpl;
+
+  return UsedVars->count(VD);
+}
+
 void PseudoConstantAnalysis::RunAnalysis() {
   std::deque<const Stmt *> WorkList;
   VarDeclSet *NonConstants = (VarDeclSet*)NonConstantsImpl;
+  VarDeclSet *UsedVars = (VarDeclSet*)UsedVarsImpl;
 
   // Start with the top level statement of the function
   WorkList.push_back(DeclBody);
@@ -65,7 +80,7 @@ void PseudoConstantAnalysis::RunAnalysis() {
     // Case 1: Assignment operators modifying ValueDecl
     case Stmt::BinaryOperatorClass: {
       const BinaryOperator *BO = cast<BinaryOperator>(Head);
-      const Expr *LHS = BO->getLHS()->IgnoreParenImpCasts();
+      const Expr *LHS = BO->getLHS()->IgnoreParenCasts();
       const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(LHS);
 
       // We only care about DeclRefExprs on the LHS
@@ -76,7 +91,16 @@ void PseudoConstantAnalysis::RunAnalysis() {
       // for any of the assignment operators, implying that this Decl is being
       // written to.
       switch (BO->getOpcode()) {
-      case BinaryOperator::Assign:
+      case BinaryOperator::Assign: {
+        const Expr *RHS = BO->getRHS()->IgnoreParenCasts();
+        if (const DeclRefExpr *RHSDecl = dyn_cast<DeclRefExpr>(RHS)) {
+          // Self-assignments don't count as use of a variable
+          if (DR->getDecl() == RHSDecl->getDecl())
+            // Do not visit the children
+            continue;
+        }
+
+      }
       case BinaryOperator::AddAssign:
       case BinaryOperator::SubAssign:
       case BinaryOperator::MulAssign:
@@ -148,16 +172,37 @@ void PseudoConstantAnalysis::RunAnalysis() {
         if (!VD->getType().getTypePtr()->isReferenceType())
           continue;
 
-        // Ignore VarDecls without a body
-        if (!VD->getBody())
-          continue;
-
         // If the reference is to another var, add the var to the non-constant
         // list
-        if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(VD->getBody()))
-          if (const VarDecl *RefVD = dyn_cast<VarDecl>(DR->getDecl()))
+        if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(VD->getInit()))
+          if (const VarDecl *RefVD = dyn_cast<VarDecl>(DR->getDecl())) {
             NonConstants->insert(RefVD);
+            continue;
+          }
+      }
+      break;
+    }
+
+    // Case 4: Block variable references
+    case Stmt::BlockDeclRefExprClass: {
+      // Any block variables are assumed to be non-constant
+      const BlockDeclRefExpr *BDR = cast<BlockDeclRefExpr>(Head);
+      if (const VarDecl *VD = dyn_cast<VarDecl>(BDR->getDecl())) {
+        NonConstants->insert(VD);
+        UsedVars->insert(VD);
+        continue;
       }
+      break;
+    }
+
+    // Case 5: Variable references
+    case Stmt::DeclRefExprClass: {
+      const DeclRefExpr *DR = cast<DeclRefExpr>(Head);
+      if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
+        UsedVars->insert(VD);
+        continue;
+      }
+      break;
     }
 
       default:
diff --git a/lib/Checker/IdempotentOperationChecker.cpp b/lib/Checker/IdempotentOperationChecker.cpp
index 2cfcaa44d4..d8936203ea 100644
--- a/lib/Checker/IdempotentOperationChecker.cpp
+++ b/lib/Checker/IdempotentOperationChecker.cpp
@@ -74,7 +74,9 @@ class IdempotentOperationChecker
     void UpdateAssumption(Assumption &A, const Assumption &New);
 
     // False positive reduction methods
-    static bool isParameterSelfAssign(const Expr *LHS, const Expr *RHS);
+    static bool isUnusedSelfAssign(const Expr *LHS,
+                                      const Expr *RHS,
+                                      AnalysisContext *AC);
     static bool isTruncationExtensionAssignment(const Expr *LHS,
                                                 const Expr *RHS);
     static bool PathWasCompletelyAnalyzed(const CFG *C,
@@ -182,12 +184,19 @@ void IdempotentOperationChecker::PreVisitBinaryOperator(
 
   // Fall through intentional
   case BinaryOperator::Assign:
-    // x Assign x has a few more false positives we can check for
-    if (isParameterSelfAssign(RHS, LHS)
-        || isTruncationExtensionAssignment(RHS, LHS)) {
+    // x Assign x can be used to silence unused variable warnings intentionally,
+    // and has a slightly different definition for false positives.
+    if (isUnusedSelfAssign(RHS, LHS, AC)
+        || isTruncationExtensionAssignment(RHS, LHS)
+        || containsNonLocalVarDecl(RHS)
+        || containsNonLocalVarDecl(LHS)) {
       A = Impossible;
       return;
     }
+    if (LHSVal != RHSVal)
+      break;
+    UpdateAssumption(A, Equal);
+    return;
 
   case BinaryOperator::SubAssign:
   case BinaryOperator::DivAssign:
@@ -397,10 +406,12 @@ inline void IdempotentOperationChecker::UpdateAssumption(Assumption &A,
   }
 }
 
-// Check for a statement were a parameter is self assigned (to avoid an unused
-// variable warning)
-bool IdempotentOperationChecker::isParameterSelfAssign(const Expr *LHS,
-                                                       const Expr *RHS) {
+// Check for a statement where a variable is self assigned to avoid an unused
+// variable warning. We still report if the variable is used after the self
+// assignment.
+bool IdempotentOperationChecker::isUnusedSelfAssign(const Expr *LHS,
+                                                    const Expr *RHS,
+                                                    AnalysisContext *AC) {
   LHS = LHS->IgnoreParenCasts();
   RHS = RHS->IgnoreParenCasts();
 
@@ -408,15 +419,22 @@ bool IdempotentOperationChecker::isParameterSelfAssign(const Expr *LHS,
   if (!LHS_DR)
     return false;
 
-  const ParmVarDecl *PD = dyn_cast<ParmVarDecl>(LHS_DR->getDecl());
-  if (!PD)
+  const VarDecl *VD = dyn_cast<VarDecl>(LHS_DR->getDecl());
+  if (!VD)
     return false;
 
   const DeclRefExpr *RHS_DR = dyn_cast<DeclRefExpr>(RHS);
   if (!RHS_DR)
     return false;
 
-  return PD == RHS_DR->getDecl();
+  if (VD != RHS_DR->getDecl())
+    return false;
+
+  // If the var was used outside of a selfassign, then we should still report
+  if (AC->getPseudoConstantAnalysis()->wasReferenced(VD))
+    return false;
+
+  return true;
 }
 
 // Check for self casts truncating/extending a variable