Make physical comparison aware of promotion duplication.

Promoting an object duplicates the object in the major heap and uses
write barriers to ensure that the copies are in sync. However, physical
comparison breaks due to this. Physical comparison is essential for
pattern matching polymorphic and extensible variants. See ocaml#7 for
example. The fix ensures that the major heap object is always used when
comparing promoted objects.

byterun/interp.c

@@ -1061,8 +1061,20 @@ value caml_interprete(code_t prog, asize_t prog_size)
       accu = (value)((((intnat) accu - 1) >> Long_val(*sp++)) | 1); Next;
 
 #define Integer_comparison(typ,opname,tst) \
-    Instruct(opname): \
-      accu = Val_int((typ) accu tst (typ) *sp++); Next;
+    Instruct(opname): { \
+      if (Is_long (accu) || Is_long(*sp)) { \
+        accu = Val_int((typ) accu tst (typ) *sp++); \
+        Next; \
+      } \
+      if (Is_promoted_hd(Hd_val(accu)) && Is_young(accu)) \
+        accu = caml_addrmap_lookup(&caml_remembered_set.promotion, accu); \
+      value v2 = *(value*)sp; \
+      if (Is_promoted_hd(Hd_val(v2)) && Is_young(v2)) \
+        v2 = caml_addrmap_lookup(&caml_remembered_set.promotion, v2); \
+      accu = Val_int((typ) accu tst (typ) v2); \
+      sp++; \
+      Next; \
+    }
 
     Integer_comparison(intnat,EQ, ==)
     Integer_comparison(intnat,NEQ, !=)