Do not generate at use site loop phis. It requires live analysis that we currently don't implement.

frog/tests/leg/src/SsaPhiEliminatorTest.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Test that parameters keep their names in the output.
 
 #import("compiler_helper.dart");
 
 final String TEST_ONE = @"""
 void foo(bar) {
   var a = 1;
@@ skipping 36 matching lines @@
     if (i == 9) cond1 = false;
     for (var j = 0; cond2; j = j + 1) {
       if (j == 9) cond2 = false;
     }
   }
   print(cond1);
   print(cond2);
 }
 """;
 
+String anyIdentifier = "[a-zA-Z][a-zA-Z0-9]*";
+
 main() {
   String generated = compile(TEST_ONE, 'foo');
   RegExp regexp = const RegExp("a = 2");
   Expect.isTrue(regexp.hasMatch(generated));
 
   regexp = const RegExp("a = 3");
   Expect.isTrue(regexp.hasMatch(generated));
 
   regexp = const RegExp("print\\(a\\)");
   Expect.isTrue(regexp.hasMatch(generated));
 
   generated = compile(TEST_TWO, 'main');
-  regexp = const RegExp("t = \\(t +");
+  regexp = new RegExp("t = \\($anyIdentifier +");
   Expect.isTrue(regexp.hasMatch(generated));
 
-  regexp = const RegExp("i = \\(i +");
-  Expect.isTrue(regexp.hasMatch(generated));
-
-  regexp = const RegExp("print\\(t\\)");
+  regexp = new RegExp("i = \\($anyIdentifier +");
   Expect.isTrue(regexp.hasMatch(generated));
 
   generated = compile(TEST_THREE, 'foo');
 
   // Check that we don't have 'val = val'.
   regexp = const RegExp("val = val;");
   Expect.isTrue(!regexp.hasMatch(generated));
 
   regexp = const RegExp("return val");
   Expect.isTrue(regexp.hasMatch(generated));
   // Check that a store just after the declaration of the local
   // only generates one instruction.
   regexp = const RegExp("var val = 42");
   Expect.isTrue(regexp.hasMatch(generated));
 
   generated = compile(TEST_FOUR, 'foo');
 
   regexp = const RegExp("cond1 = cond1;");
   Expect.isTrue(!regexp.hasMatch(generated));
 
   regexp = const RegExp("cond2 = cond2;");
   Expect.isTrue(!regexp.hasMatch(generated));
 }