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Subject: [Bug middle-end/51994] [4.6/4.7 Regression] git-1.7.8.3 miscompiled due to negative bitpos from get_inner_reference
Date: Wed, 25 Jan 2012 11:10:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51994

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-01-25
                 CC|                            |ebotcazou at gcc dot
                   |                            |gnu.org
          Component|tree-optimization           |middle-end
     Ever Confirmed|0                           |1

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-01-25 10:56:37 UTC ---
Negative bitpos is fine - Ada uses that quite extensively and with MEM_REFs
this just got more prominent.  get_inner_reference is declared to return
a _signed_ HOST_WIDE_INT bitpos for a reason.

What should happen instead is that store_field needs to adjust the address
to properly point before the bitfield for calling store_bit_field.  Or the
latter needs to take signed arguments for bitpos and do the adjustment
itself.

Does simply changing the store_bit_field[_1] prototype work for you?