Adding assertions to fast elements conversion.

src/arm/codegen-arm.cc

Index: src/arm/codegen-arm.cc
diff --git a/src/arm/codegen-arm.cc b/src/arm/codegen-arm.cc
index 508d830bdfdca006e05ca8928d11ad551e1b5ea4..3570ebaac17bb1bd9ce7bb0499a6f552793ee0b1 100644
--- a/src/arm/codegen-arm.cc
+++ b/src/arm/codegen-arm.cc
@@ -180,6 +180,15 @@ void ElementsTransitionGenerator::GenerateSmiOnlyToDouble(
 
   // Hole found, store the-hole NaN.
   __ bind(&convert_hole);
+
+  if (FLAG_debug_code) {
+    Label is_really_the_hole;
+    __ CompareRoot(r9, Heap::kTheHoleValueRootIndex);
+    __ b(eq, &is_really_the_hole);
+    __ Abort("object found in smi-only array");
+    __ bind(&is_really_the_hole);
+  }
+
   __ Strd(r4, r5, MemOperand(r7, 8, PostIndex));
 
   __ bind(&entry);