DeadStoresChecker: Don't warn about dead stores into volatile variables

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@273689 91177308-0d34-0410-b5e6-96231b3b80d8

lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp

@@ -278,6 +278,8 @@ public:
           RHS = RHS->IgnoreParenCasts();
 
           QualType T = VD->getType();
+          if (T.isVolatileQualified())
+            return;
           if (T->isPointerType() || T->isObjCObjectPointerType()) {
             if (RHS->isNullPointerConstant(Ctx, Expr::NPC_ValueDependentIsNull))
               return;

test/Analysis/dead-stores.c

@@ -569,3 +569,7 @@ void testBOComma() {
 
 }
 
+void testVolatile() {
+    volatile int v;
+    v = 0; // no warning
+}