------- 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
