Adding assertions to fast elements conversion.

src/ia32/codegen-ia32.cc

Index: src/ia32/codegen-ia32.cc
diff --git a/src/ia32/codegen-ia32.cc b/src/ia32/codegen-ia32.cc
index 391272760a5343ff7736b3cf8bb68d77157c721a..79fd3ccface4f321e6c3c198d5d750329e1a3776 100644
--- a/src/ia32/codegen-ia32.cc
+++ b/src/ia32/codegen-ia32.cc
@@ -378,6 +378,15 @@ void ElementsTransitionGenerator::GenerateSmiOnlyToDouble(
 
   // Found hole, store hole_nan_as_double instead.
   __ bind(&convert_hole);
+
+  if (FLAG_debug_code) {
+    Label is_really_the_hole;
+    __ cmp(ebx, masm->isolate()->factory()->the_hole_value());
+    __ j(equal, &is_really_the_hole);
+    __ Abort("object found in smi-only array");
+    __ bind(&is_really_the_hole);
+  }
+
   if (CpuFeatures::IsSupported(SSE2)) {
     CpuFeatures::Scope use_sse2(SSE2);
     __ movdbl(FieldOperand(eax, edi, times_4, FixedDoubleArray::kHeaderSize),