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Subject: [Bug middle-end/55142] [4.8 Regression] internal compiler error: in plus_constant, at explow.c:88
Date: Thu, 01 Nov 2012 22:24:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55142

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |NEW
          Component|target                      |middle-end

--- Comment #14 from H.J. Lu <hjl.tools at gmail dot com> 2012-11-01 22:24:20 UTC ---
(In reply to comment #13)
> Created attachment 28591 [details]
> Tentative fix
> 
> This generates (essentially) the same RTL as in non-PIC mode, so the generated
> code should be correct if it is correct in non-PIC mode.
> 
> Tested only in LP64 mode though.

The patch compiles testcase, but totally miscompiles glibc.
I think the bug is in unsigned array index computation as
shown in Comment 7. dyn->d_tag is signed type and Pmode
!= ptr_mode here.