http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50088

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |hjl.tools at gmail dot com

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> 2011-08-15 14:47:51 
UTC ---
It is done on purpose:

  /* X86_TUNE_MOVX: Enable to zero extend integer registers to avoid
     partial dependencies.  */
  m_PPRO | m_P4_NOCONA | m_CORE2I7 | m_ATOM | m_GEODE | m_AMD_MULTIPLE  |
m_GENERIC,

You can remove m_ATOM to see its performance impact with -mtune=atom
on Atom.

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