Improve smi shift operations and avoid repeated deoptimizations.

tests/language/arithmetic_test.dart

 // Copyright (c) 2012, 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.
 // Dart test program to test arithmetic operations.
 
 #library('arithmetic_test');
 #import('dart:math');
 
 class ArithmeticTest {
 
@@ skipping 37 matching lines @@
     Expect.equals(5.5, a / b);
     Expect.equals(2.0, 10 / 5);
     Expect.equals(2, a % b);
     Expect.equals(2, a.remainder(b));
     // Smi corner cases.
     for (int i = 0; i < 80; i++) {
       a = -(1 << i);
       b = -1;
       Expect.equals(1 << i, a ~/ b);
     }
+    for (int i = 0; i < 80; i++) {
+      a = -1 << i;
+      b = -1;
+      Expect.equals(1 << i, a ~/ b);
+    }
     a = 22;
     b = 4.0;
     // Smi & double.
     Expect.equals(26.0, a + b);
     Expect.equals(18.0, a - b);
     Expect.equals(88.0, a * b);
     Expect.equals(5.0, a ~/ b);
     Expect.equals(5.5, a / b);
     Expect.equals(2.0, a % b);
     Expect.equals(2.0, a.remainder(b));
@@ skipping 337 matching lines @@
     Expect.equals(false, 1.0 < min(1.0, 12.0));
     Expect.equals(true, 1.0 < max(1.0, 12.0));
 
     // Hashcode
     Expect.equals(false, (3.4).hashCode == (1.2).hashCode);
     Expect.equals(true, (1.2).hashCode == (1.2).hashCode);
     Expect.equals(false, (3).hashCode == (1).hashCode);
     Expect.equals(true, (10).hashCode == (10).hashCode);
   }
 
+  static int div(a, b) => a ~/ b;
+
+  static void testSmiDivDeopt() {
+    var a = -0x40000000;
+    var b = -1;
+    for (var i = 0; i < 10; i++) Expect.equals(0x40000000, div(a, b));
+  }
+
   static testMain() {
     for (int i = 0; i < 1500; i++) {
       runOne();
+      testSmiDivDeopt();
     }
   }
 }
 
 main() {
   ArithmeticTest.testMain();
 }