Added two test cases for join

tests/regression/77-lin2vareq/14-join_after_guard.c

@@ -0,0 +1,17 @@
+//SKIP PARAM: --set ana.activated[+] lin2vareq --set ana.relation.privatization top --set sem.int.signed_overflow assume_none
+// from 63-affeq/04-join-after-guard
+int main(void) {
+   int zero = 0;
+   int x = 0;
+
+   int t, r, d;
+   if (t) {
+       r = 10;
+       d = 500;
+   } else {
+       r = 10;
+   }
+   __goblint_check(r == 10); //SUCCESS
+   __goblint_check(d == 500); //UNKNOWN!
+   return 0;
+}

tests/regression/77-lin2vareq/15-join-non-constant.c

@@ -0,0 +1,22 @@
+// SKIP PARAM: --set ana.activated[+] lin2vareq --set ana.relation.privatization top --set sem.int.signed_overflow assume_none
+
+int main(void) {
+  int a, b, c, d;
+
+  int t;
+  if (t) {
+    b = a + 2;
+    c = a + 7;
+    d = a + 1;
+  } else {
+    b = a + 30;
+    c = a + 35;
+    d = a + 10;
+  }
+  __goblint_check(c == b + 5); // SUCCESS
+  __goblint_check(c == b + 3); // FAILURE
+  __goblint_check(d == b + 3); // UNKNOWN!
+  __goblint_check(b == a + 2); // UNKNOWN!
+
+  return 0;
+}