Revert "Revert "Revert "[optimizing] Improve x86 shifts"""

This reverts commit 9b95a057.

Reverting this CL as it breaks libcore tests:

  org.apache.harmony.tests.java.lang.DoubleTest#test_compare
      junit.framework.AssertionFailedError: compare() -0.0 should be less 0.0
      	at junit.framework.Assert.assertTrue(Assert.java:140)
      	at org.apache.harmony.tests.java.lang.DoubleTest.test_compare(DoubleTest.java:258)
    org.apache.harmony.tests.java.lang.DoubleTest#test_compare FAIL (EXEC_FAILED)
  
  org.apache.harmony.tests.java.lang.DoubleTest#test_compareToLjava_lang_Double
      junit.framework.AssertionFailedError: Assert 2: compare() -0.0 should be less 0.0
      	at junit.framework.Assert.assertTrue(Assert.java:140)
      	at org.apache.harmony.tests.java.lang.DoubleTest.test_compareToLjava_lang_Double(DoubleTest.java:1320)
    org.apache.harmony.tests.java.lang.DoubleTest#test_compareToLjava_lang_Double FAIL (EXEC_FAILED)

Change-Id: I10f0ec8cc9495cc225fef1940b3f1a9fe87d996f