[KeyedLoadIC] Support Smi "handlers" for simple field loads

src/field-index.h

Index: src/field-index.h
diff --git a/src/field-index.h b/src/field-index.h
index 2dace97ca582b0dd39844aec803390ada6f9aeaa..d0ae2f27f9c7ba4ea391f2d779181ebfc3577594 100644
--- a/src/field-index.h
+++ b/src/field-index.h
@@ -76,6 +76,13 @@ class FieldIndex final {
         (IsInObjectBits::kMask | IsDoubleBits::kMask | IndexBits::kMask);
   }
 
+  // For GetLoadByFieldOffset.
+  class FieldOffsetIsInobject : public BitField<bool, 1, 1> {};
+  class FieldOffsetIsDouble : public BitField<bool, 2, 1> {};
+  class FieldOffsetOffset : public BitField<int, 3, 27> {};
+  // Make sure we don't overflow into the sign bit.
+  STATIC_ASSERT(FieldOffsetOffset::kNext <= kSmiValueSize - 1);
+
  private:
   FieldIndex(bool is_inobject, int local_index, bool is_double,
              int inobject_properties, int first_inobject_property_offset,