Revert "[Clang] -Wunused-but-set-variable warning - handle also pre/post unary operators"

This reverts commit 460fc440ad.

clang/lib/Sema/SemaExprCXX.cpp

@@ -7921,7 +7921,6 @@ static void MaybeDecrementCount(
     Expr *E, llvm::DenseMap<const VarDecl *, int> &RefsMinusAssignments) {
   DeclRefExpr *LHS = nullptr;
   bool IsCompoundAssign = false;
-  bool isIncrementDecrementUnaryOp = false;
   if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
     if (BO->getLHS()->getType()->isDependentType() ||
         BO->getRHS()->getType()->isDependentType()) {
@@ -7936,11 +7935,6 @@ static void MaybeDecrementCount(
     if (COCE->getOperator() != OO_Equal)
       return;
     LHS = dyn_cast<DeclRefExpr>(COCE->getArg(0));
-  } else if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E)) {
-    if (!UO->isIncrementDecrementOp())
-      return;
-    isIncrementDecrementUnaryOp = true;
-    LHS = dyn_cast<DeclRefExpr>(UO->getSubExpr());
   }
   if (!LHS)
     return;
@@ -7948,10 +7942,8 @@ static void MaybeDecrementCount(
   if (!VD)
     return;
   // Don't decrement RefsMinusAssignments if volatile variable with compound
-  // assignment (+=, ...) or increment/decrement unary operator to avoid
-  // potential unused-but-set-variable warning.
-  if ((IsCompoundAssign || isIncrementDecrementUnaryOp) &&
-      VD->getType().isVolatileQualified())
+  // assignment (+=, ...) to avoid potential unused-but-set-variable warning.
+  if (IsCompoundAssign && VD->getType().isVolatileQualified())
     return;
   auto iter = RefsMinusAssignments.find(VD);
   if (iter == RefsMinusAssignments.end())

clang/test/Sema/warn-unused-but-set-parameters.c

@@ -25,10 +25,10 @@ void f3(struct S s) { // expected-warning{{parameter 's' set but not used}}
   s = t;
 }
 
-void f4(int j) { // expected-warning{{parameter 'j' set but not used}}
+void f4(int j) { //TODO: warn
     j++;
 }
 
-void f5(int k) { // expected-warning{{parameter 'k' set but not used}}
+void f5(int k) { //TODO: warn
     --k;
 }

clang/test/Sema/warn-unused-but-set-variables.c

@@ -73,20 +73,3 @@ void f3(void) {
   __attribute__((__cleanup__(for_cleanup))) int x;
   x = 5;
 }
-
-void f4(void) {
-  int x1 = 0; // expected-warning{{variable 'x1' set but not used}}
-  x1++;
-  int x2 = 0; // expected-warning{{variable 'x2' set but not used}}
-  x2--;
-  int x3 = 0; // expected-warning{{variable 'x3' set but not used}}
-  ++x3;
-  int x4 = 0; // expected-warning{{variable 'x4' set but not used}}
-  --x4;
-
-  volatile int v1 = 0;
-  ++v1;
-  typedef volatile int volint;
-  volint v2 = 0;
-  v2++;
-}

clang/test/SemaCXX/warn-unused-but-set-variables-cpp.cpp

@@ -7,7 +7,6 @@ struct S {
 struct __attribute__((warn_unused)) SWarnUnused {
   int j;
   void operator +=(int);
-  void operator ++();
 };
 
 int f0() {
@@ -63,9 +62,3 @@ template<typename T> void f4(T n) {
   SWarnUnused swu;
   swu += n;
 }
-
-template <typename T> void f5() {
-  // Don't warn for overloaded pre/post operators in template code.
-  SWarnUnused swu;
-  ++swu;
-}