Fix generated code for String.charCodeAt.

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 95aeba6817f789c6c56d3190508a4e0c415de6a6..c883a48f7bdf9b1e6284dd5ff0ed25bf2516d052 100644
--- a/src/ia32/codegen-ia32.cc
+++ b/src/ia32/codegen-ia32.cc
@@ -12638,7 +12638,6 @@ void StringCharCodeAtGenerator::GenerateSlow(
   call_helper.BeforeCall(masm);
   __ push(object_);
   __ push(index_);
-  __ push(result_);
   __ push(index_);  // Consumed by runtime conversion function.
   if (index_flags_ == STRING_INDEX_IS_NUMBER) {
     __ CallRuntime(Runtime::kNumberToIntegerMapMinusZero, 1);
@@ -12652,9 +12651,11 @@ void StringCharCodeAtGenerator::GenerateSlow(
     // have a chance to overwrite it.
     __ mov(scratch_, eax);
   }
-  __ pop(result_);
   __ pop(index_);
   __ pop(object_);
+  // Reload the instance type.
+  __ mov(result_, FieldOperand(object_, HeapObject::kMapOffset));
+  __ movzx_b(result_, FieldOperand(result_, Map::kInstanceTypeOffset));
   call_helper.AfterCall(masm);
   // If index is still not a smi, it must be out of range.
   ASSERT(kSmiTag == 0);