[regexp] Avoid unneeded accesses to lastIndex

test/mjsunit/regress/regress-2438.js

Index: test/mjsunit/regress/regress-2438.js
diff --git a/test/mjsunit/regress/regress-2438.js b/test/mjsunit/regress/regress-2438.js
index f694ff8e190765a9782770ef3c9b52c75cada0f0..51092788ac6f7fb8824f4df1e44f37f45cffd650 100644
--- a/test/mjsunit/regress/regress-2438.js
+++ b/test/mjsunit/regress/regress-2438.js
@@ -27,14 +27,20 @@
 
 function testSideEffects(subject, re) {
   var counter = 0;
+  var expected_counter = 0;
+  const accesses_lastindex = (re.global || re.sticky);
   var side_effect_object = { valueOf: function() { return counter++; } };
   re.lastIndex = side_effect_object;
   re.exec(subject);
-  assertEquals(1, counter);
+
+  if (accesses_lastindex) expected_counter++;
+  assertEquals(expected_counter, counter);
 
   re.lastIndex = side_effect_object;
   re.test(subject);
-  assertEquals(2, counter);
+
+  if (accesses_lastindex) expected_counter++;
+  assertEquals(expected_counter, counter);
 }
 
 testSideEffects("zzzz", /a/);