[Bug tree-optimization/54132] [4.8 Regression] Incorrect loop transformation with -ftree-loop-distribute-patterns

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54132

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2012-07-31
     Ever Confirmed|0                           |1
            Summary|Incorrect loop              |[4.8 Regression] Incorrect
                   |transformation with         |loop transformation with
                   |-ftree-loop-distribute-patt |-ftree-loop-distribute-patt
                   |erns                        |erns
   Target Milestone|---                         |4.8.0

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-31 
09:30:57 UTC ---
Mine.  It seems indeed wrong to ever generate memmove from a loop with
possibly aliasing source / destination and a data dependency between source
and destination.

void foo(char *p, int n)
{
    int i;
    for (i = 1; i < n; i++)
      p[i-1] = p[i];
}

would be a memmove (no data dependence).