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[Bug target/49799] gcc arm generates illegal sbfx instruction


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49799

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.07.21 14:27:59
                 CC|                            |ramana at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #3 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2011-07-21 14:27:59 UTC ---
Confirmed - and it appears as though combine is doing this transformation .
Based on a quick debug I couldn't spot any pattern in the backend that
encourages this other than the extv matcher. 


One could guard this by making sure that the backend doesn't recognize such
forms but combine really shouldn't be generating such a extv instruction
reading more bits than that are already available.  

Ramana


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