Do not use StripCasts() in this context.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@120178 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Checker/ArrayBoundChecker.cpp b/lib/Checker/ArrayBoundChecker.cpp
index cf2a2fc..dccb9a2 100644
--- a/lib/Checker/ArrayBoundChecker.cpp
+++ b/lib/Checker/ArrayBoundChecker.cpp
@@ -44,8 +44,6 @@
   if (!R)
     return;
 
-  R = R->StripCasts();
-
   const ElementRegion *ER = dyn_cast<ElementRegion>(R);
   if (!ER)
     return;
@@ -53,6 +51,11 @@
   // Get the index of the accessed element.
   DefinedOrUnknownSVal Idx = cast<DefinedOrUnknownSVal>(ER->getIndex());
 
+  // Zero index is always in bound, this also passes ElementRegions created for
+  // pointer casts.
+  if (Idx.isZeroConstant())
+    return;
+
   const GRState *state = C.getState();
 
   // Get the size of the array.