[-Wunreachable-code] Tweak isTrivialDoWhile() to handle implicit casts.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204376 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/ReachableCode.cpp

@@ -51,7 +51,7 @@ static bool isTrivialDoWhile(const CFGBlock *B, const Stmt *S) {
   // condition.
   if (const Stmt *Term = B->getTerminator()) {
     if (const DoStmt *DS = dyn_cast<DoStmt>(Term)) {
-      const Expr *Cond = DS->getCond();
+      const Expr *Cond = DS->getCond()->IgnoreParenCasts();
       return Cond == S && isTrivialExpression(Cond);
     }
   }

test/SemaCXX/warn-unreachable.cpp

@@ -218,6 +218,14 @@ int test_treat_non_const_bool_local_as_non_config_value() {
   return 0;
 }
 
+void test_do_while(int x) {
+  // Handle trivial expressions with
+  // implicit casts to bool.
+  do {
+    break;
+  } while (0); // no-warning
+}
+
 class Frobozz {
 public:
   Frobozz(int x);