[Bug rtl-optimization/20527] New: [4.1, 4.0 regression] Mishandling of postincrement causes bzip2 miscompilation.

["hp at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

Seen on 4.0 "Thu Mar 17 06:05:21 UTC 2005" and trunk of "Thu Mar 17 15:06:06 UTC
2005" at -O2.  The test-case in the first attachment has this code snippet:
    vec += (base[i+1] - base[i]);

The expression at the right hand of that line is compiled at -O2 into:
        move.d [$r11+],$r9
        sub.d [$r11-4],$r9
Tsk tsk.  Some part of GCC doesn't adjust expressions when postincrements are
involved.

I don't see this bug with 3.2.1, so I call it a regression, though local changes
might affect the actual regressionness.  It is unknown whether it's also a
regression for 3.4 and 3.3.

-- 
           Summary: [4.1, 4.0 regression] Mishandling of postincrement
                    causes bzip2 miscompilation.
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hp at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: cris-*-*


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20527