[ubsan] Disable bounds-check for flexible array ivars

This eliminates a class of false positives for -fsanitize=array-bounds
on instrumented ObjC projects.

Differential Revision: https://reviews.llvm.org/D22227

llvm-svn: 283249
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 7e12f5e..94823ae 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -708,6 +708,8 @@
           DeclContext::decl_iterator(const_cast<FieldDecl *>(FD)));
       return ++FI == FD->getParent()->field_end();
     }
+  } else if (const auto *IRE = dyn_cast<ObjCIvarRefExpr>(E)) {
+    return IRE->getDecl()->getNextIvar() == nullptr;
   }
 
   return false;