[Bug tree-optimization/49365] 436.cactusADM performance regression

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49365

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.06.14 10:49:14
                 CC|                            |changpeng.fang at amd dot
                   |                            |com
     Ever Confirmed|0                           |1

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-06-14 10:49:14 UTC ---
Indeed, for the important loop in StaggeredLeapfrog2.F we now have

 Ahead 1, unroll factor 1, trip count -1
 insn count 919, mem ref count 100, prefetch count 100
 Not prefetching -- instruction to prefetch ratio (9) too small

while before the patch we had

 insn count 1019, mem ref count 100, prefetch count 100

as we now have half the cost for the vectorized mem-refs (100 instead of 200).

Building with --param min-insn-to-prefetch-ratio=9 fixes it.