[hydrogen] optimize switch with string clauses

test/mjsunit/switch.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 108 matching lines @@
   }
   return x;
 }
 
 
 assertEquals(3, f4(0), "fallthrough-switch.0");
 assertEquals(3, f4(1), "fallthrough-switch.1");
 assertEquals(3, f4(2), "fallthrough-switch.2");
 assertEquals(5, f4(3), "fallthrough-switch.3");
 
+function f4_string(tag, x) {
+  switch(tag) {
+    case 'zero':
+      x++;
+    case 'two':
+      x++;
+  }
+  return x;
+}
+
+// Symbols
+assertEquals(2, f4_string('zero', 0), "fallthrough-string-switch.0");
+assertEquals(1, f4_string('one', 1), "fallthrough-string-switch.1");
+assertEquals(3, f4_string('two', 2), "fallthrough-string-switch.2");
+
+// Strings
+assertEquals(2, f4_string('_zero'.slice(1), 0), "fallthrough-string-switch.3");
+assertEquals(1, f4_string('_one'.slice(1), 1), "fallthrough-string-switch.4");
+assertEquals(3, f4_string('_two'.slice(1), 2), "fallthrough-string-switch.5");
+
+// Oddball
+assertEquals(3, f4_string(null, 3), "fallthrough-string-switch.6");
+
+// Test for regression
+function regress_string(value) {
+  var json = 1;
+  switch (typeof value) {
+    case 'object':
+      break;
+
+    default:
+
+  }
+  return json;
+};
+assertEquals(1, regress_string('object'), 'regression-string');
 
 function f5(x) {
   switch(x) {
      case -2: return true;
      case -1: return false;
      case 0: return true;
      case 2: return false;
      default: return 42;
   }
 }
@@ skipping 141 matching lines @@
          "    }\n" +
          "  }\n" +
          "  return res;\n" +
          "})";
   return eval(res);
 }
 var verylong_size = 1000;
 var verylong = makeVeryLong(verylong_size);
 
 assertEquals(verylong_size * 2 + 1, verylong());