[Bug tree-optimization/45021] Redundant prefetches for some loops (vectorizer produced ones too)

["pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #2 from pinskia at gcc dot gnu dot org  2010-07-24 20:32 -------
(In reply to comment #1)
> The direct reason is that prefetching could not differentiate the base
> addresses
> of the vectorized load and store (of a[i]):
> *vect_pa.6_24
> *vect_pa.19_37

Here is a testcase which shows the same issue without the vectorizer (compile
-O2 -fprefetch-loop-arrays -march=amdfam10 -fno-tree-ccp -fno-tree-vrp
-fno-tree-dominator-opts):
float *f();
float aa[1024];
float bb[1024];
void foo(int beta)
{
  int i;
  float *a = aa, *a1 = aa, *b = bb;
  for(i=0; i<1024; i++)
{
     *a = *a1 + beta * *b;
a++; a1++; b++;
}
}


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2010-07-24 20:32:24
               date|                            |
            Summary|Redundant prefetches for the|Redundant prefetches for
                   |vectorized loop             |some loops (vectorizer
                   |                            |produced ones too)


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45021