Add test cases for fast smi loops.

test/mjsunit/compiler/loopcount.js

Index: test/mjsunit/compiler/loopcount.js
===================================================================
--- test/mjsunit/compiler/loopcount.js	(revision 4172)
+++ test/mjsunit/compiler/loopcount.js	(working copy)
@@ -54,5 +54,24 @@
 }
 assertEquals(-0x40000001, f5());
 
+
 function f6() { var x = 0x3fffffff; x++; return x+1; }
 assertEquals(0x40000001, f6());
+
+
+function f7() {
+  var i;
+  for (i = 0x3ffffffd; i <= 0x3ffffffe; i++) {}
+  i++; i = i + 1;
+  return i;
+}
+assertEquals(0x40000001, f7());
+
+
+function f8() {
+  var i;
+  for (i = 0x3ffffffd; i <= 0x3fffffff; i++) {}
+  i++; i++;
+  return i;
+}
+assertEquals(0x40000002, f8());