[Bug tree-optimization/37534] New: [4.4 Regression] IRA causes 17% degradation in 187.facerec benchmark

["luisgpm at linux dot vnet dot ibm dot com" <gcc-bugzilla at gcc dot gnu dot org>]

A degradation of ~17% occured in SPEC2000's ppc64 187.facerec benchmark right
after the IRA patch went in (revision 139590 -
http://gcc.gnu.org/viewcvs?view=rev&revision=139590).

The attached code is as far as i could go without removing all the bad
instruction sequences and yet making it smaller than the whole function.

While the code generated by r139589 has 174 load instructions and 59 store
instructions, the one generated by r139590 hs 215 loads and 103 stores. A
difference of about 40 instructions for each.

If we look into the complete function, the difference jumps to about 250 more
load/store instructions. The logs show that r139590 has more spills than
r139589.


-- 
           Summary: [4.4 Regression] IRA causes 17% degradation in
                    187.facerec benchmark
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: luisgpm at linux dot vnet dot ibm dot com
 GCC build triplet: powerpc64-linux
  GCC host triplet: powerpc64-linux
GCC target triplet: powerpc64-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37534