[Bug rtl-optimization/17950] Over Aggressive Use of Data Cache Touch Instructions During FDO

[jgrimm2 at us dot ibm dot com]

------- Additional Comments From jgrimm2 at us dot ibm dot com  2004-11-23 01:43 -------
Finally got SPEC set up w/profiling to do a little comparison.  Its not done yet
(and only running c,c++ tests) but first glance through the initials results, it
appears that -fspeculative-prefetching is damaging to spec results at least on
ppc64 (-m32).  I wanted to do this to guage whether this bug entry was some
pathological testcase or this would also show up in regularly looked at tests.  

I'm currently comparing -O2 -funroll-loops -fno-speculative-prefetching vs -O2
-funroll-loops -fspeculative-prefetching and using profiling for both runs.   

I'll run again to see if I can get those results.   Additionally, I'd like to
see what the behavior is when I limit the prefetches (don't emit prefetch if
just prefetched from near address + crudely limit maximum number of prefetches),
I just uploaded a patch for that, but haven't tested how it affects spec yet.




-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17950