[Bug lto/45810] 40% slowdown when using LTO for a single-file program

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45810

--- Comment #17 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2011-01-23 19:38:30 UTC ---
With the patch in comment #15 and -finline-limit=300, I get

================================================================================
Date & Time     : 23 Jan 2011 20:18:02
Test Name       : pbharness
Compile Command : gfcp %n.f90 -Ofast -funroll-loops -ftree-loop-linear
-fomit-frame-pointer -finline-limit=300 -fwhole-program -flto -o %n
Benchmarks      : ac aermod air capacita channel doduc fatigue gas_dyn induct
linpk mdbx nf protein rnflow test_fpu tfft
Maximum Times   :      300.0
Target Error %  :      0.200
Minimum Repeats :     2
Maximum Repeats :     5

   Benchmark   Compile  Executable   Ave Run  Number   Estim
        Name    (secs)     (bytes)    (secs) Repeats   Err %
   ---------   -------  ----------   ------- -------  ------
          ac      3.55       54576      8.12       2  0.0062
      aermod    103.51     1595448     18.87       2  0.0079
         air      8.87       90048      6.89       2  0.0798
    capacita      5.84       89056     40.27       2  0.0199
     channel      1.62       34448      2.98       2  0.0168
       doduc     14.30      203936     27.79       2  0.0162
     fatigue      4.89       89264      4.74       2  0.0106
     gas_dyn     11.72      148176      4.64       5  0.0535
      induct     10.87      205976     14.00       2  0.0036
       linpk      1.58       21536     21.71       2  0.0415
        mdbx      5.60       84752     12.56       2  0.1871
          nf      7.24       83712     29.23       5  0.0744
     protein     11.81      163760     35.10       2  0.0342
      rnflow     14.86      171392     26.91       2  0.0223
    test_fpu     11.35      145848     11.03       2  0.0952
        tfft      1.10       22072      3.30       2  0.1817

Geometric Mean Execution Time =      12.36 seconds

to be compared to the lowest Geometric Mean I have got so far (most of the
difference is due to nf which depends a lot of the mood of my laptop)

================================================================================
Date & Time     : 22 Dec 2010 10:33:08
Test Name       : pbharness
Compile Command : gfc %n.f90 -Ofast -funroll-loops -ftree-loop-linear
-fomit-frame-pointer -finline-limit=600 --param hot-bb-frequency-fraction=2000
-fwhole-program -flto -o %n
Benchmarks      : ac aermod air capacita channel doduc fatigue gas_dyn induct
linpk mdbx nf protein rnflow test_fpu tfft
Maximum Times   :      300.0
Target Error %  :      0.200
Minimum Repeats :     2
Maximum Repeats :     5

   Benchmark   Compile  Executable   Ave Run  Number   Estim
        Name    (secs)     (bytes)    (secs) Repeats   Err %
   ---------   -------  ----------   ------- -------  ------
          ac     11.55       58672      8.11       2  0.0123
      aermod    164.78     1522240     19.11       2  0.1151
         air     20.73       85984      6.87       5  0.1914
    capacita     14.66      105472     40.22       2  0.0584
     channel      3.22       34448      2.92       4  0.1714
       doduc     24.70      212360     27.81       2  0.1025
     fatigue      9.81       85144      4.70       3  0.1862
     gas_dyn     24.13      144240      4.66       5  0.4507
      induct     22.50      214136     13.69       2  0.1096
       linpk      2.56       21536     21.68       2  0.0231
        mdbx      8.93       84744     12.52       2  0.0080
          nf     22.61      104136     27.63       2  0.0778
     protein     26.19      155768     35.51       2  0.0127
      rnflow     30.99      163200     26.15       2  0.0248
    test_fpu     18.79      145848     10.98       2  0.0182
        tfft      1.92       22072      3.29       2  0.0304

Geometric Mean Execution Time =      12.27 seconds