[-Wunreachable-code] Handle idiomatic do...while() with an uninteresting condition.

Sometimes do..while() is used to create a scope that can be left early.
In such cases, the unreachable 'while()' test is not usually interesting
unless it actually does something that is observable.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@203051 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 7 deletions

diff --git a/lib/Analysis/ReachableCode.cpp b/lib/Analysis/ReachableCode.cpp
index 9f6792e2cc..8b192d2d61 100644
--- a/lib/Analysis/ReachableCode.cpp
+++ b/lib/Analysis/ReachableCode.cpp
@@ -312,7 +312,8 @@ static bool isTrivialReturnOrDoWhile(const CFGBlock *B, const Stmt *S) {
         return true;
   }
 
-
+  if (B->pred_size() != 1)
+    return false;
 
   // Look to see if the block ends with a 'return', and see if 'S'
   // is a substatement.  The 'return' may not be the last element in
@@ -324,15 +325,11 @@ static bool isTrivialReturnOrDoWhile(const CFGBlock *B, const Stmt *S) {
       if (const ReturnStmt *RS = dyn_cast<ReturnStmt>(CS->getStmt())) {
         const Expr *RE = RS->getRetValue();
         if (RE && RE->IgnoreParenCasts() == Ex)
-          break;
+          return bodyEndsWithNoReturn(*B->pred_begin());
       }
-      return false;
+      break;
     }
   }
-
-  if (B->pred_size() == 1)
-    return bodyEndsWithNoReturn(*B->pred_begin());
-
   return false;
 }