Re: inliner in gcc-3.1

[Gerald Pfeifer <pfeifer@dbai.tuwien.ac.at>]

On Wed, 24 Apr 2002, Kurt Garloff wrote:
> I made another patch for 3.0.1 and adapted it to 3.1, which is probably much
> more interesting: The -O3 (-finline-functions) fix.
>
> In the code I use, I put the inline keyword at all places where it was
> obvious to my eyes that inlining was a good idea. When I compile that code
> with -O3 (aka -finline-functions), performance drops by 5--10%.
>
> The reason is that comparably large functions get automatically inlined, so
> the recursive inline limit is hit earlier, and the important leaf functions
> sometimes do not get inlined any more. The problem is that all functions
> are treated as if they were declared inline, so the keyword gets completely
> ignored. I changed this and allow automatically inlined functions only half
> the size of functions declared inline by the programmer.
> This reduced the performance drop incurred by -finline-functions to 0.5--1.5%.
>
> It would be nice if this patch
> http://www.garloff.de/kurt/freesoft/gcc/gcc310-inline-func-acct-v1.diff
> would be tested by more people and integrated into 3.1.

This second patch (partially) fixes a very bad regression we've been
having since GCC 3.0; build time and binary size seem to be fine, though
we seem to degrade slightly for some of the other benchmarks.

I'd really like to see what this does to SPEC -- Andreas, could you give
it a try?

(This is due to a C module in the C++ application, and your fix seems
to be critical for many C applications in general.)

                     build time   binary size
  2.95.3                   4:01   4430752
  3.0                     23:54   6295044
  3.0.3                    3:58   3948444
  3.1-20020422             4:38   3996096  <-- without patch
  3.1-20020424+kurt-v3     5:35   4102432
  3.1.20020425+kurt-finl.  4:32   3912640  <-- this is with the patch
  3.1-20020422+limit=800   6:37   4177344
  3.1-20020422+limit=1200 16:50   4597888
  3.2-20020422             5:15   4003276

Times in [s]        | 2.95.3|       3.1      | 3.1-with-patch|
--------------------+-------+ ---------------+---------------+
      STRATCOMP1-ALL|  3.57 |   96.26 (0.01) |  23.74 (0.01) | <-- REGRESS!
   STRATCOMP-770.2-Q|  0.73 |    0.93 (0.01) |   0.83 (0.00) |
               2QBF1| 19.08 |   22.25 (0.01) |  21.33 (0.00) |
          PRIMEIMPL2| 10.74 |   12.90 (0.02) |  12.85 (0.00) |
            ANCESTOR|  8.88 |    9.54 (0.01) |   9.61 (0.01) |
       3COL-SIMPLEX1|  6.30 |    7.16 (0.00) |   7.30 (0.01) |
        3COL-LADDER1| 36.24 |   42.28 (0.01) |  41.71 (0.03) |
      3COL-N-LADDER1| 19.81 |   22.57 (0.06) |  22.96 (0.00) |
        3COL-RANDOM1| 10.69 |   12.23 (0.01) |  12.87 (0.01) |
          HP-RANDOM1| 13.16 |   14.82 (0.02) |  14.85 (0.01) |
       HAMCYCLE-FREE|  1.18 |    1.71 (0.00) |   1.71 (0.00) |
             DECOMP2| 21.91 |   24.04 (0.02) |  25.75 (0.03) |
        BW-P4-Esra-a| 91.71 |   99.28 (0.03) | 100.19 (0.05) |
        BW-P5-nopush|  6.96 |    7.43 (0.01) |   7.48 (0.00) |
       BW-P5-pushbin|  6.20 |    6.49 (0.00) |   6.57 (0.00) |
     BW-P5-nopushbin|  1.94 |    2.08 (0.00) |   2.13 (0.00) |
              3SAT-1| 32.92 |   38.48 (0.04) |  39.84 (0.00) |
   3SAT-1-CONSTRAINT| 17.46 |   20.63 (0.00) |  21.37 (0.00) |
        HANOI-Towers|  4.73 |    4.94 (0.01) |   5.24 (0.00) |
              RAMSEY|  8.00 |    8.66 (0.00) |   9.01 (0.00) |
             CRISTAL| 11.07 |   13.39 (0.01) |  12.17 (0.02) |
             HANOI-K| 33.41 |   38.73 (0.02) |  38.84 (0.00) |
           21-QUEENS|  9.66 |   10.40 (0.00) |  11.06 (0.01) |
   MSTDir[V=13,A=40]| 25.71 |   21.08 (0.01) |  21.00 (0.01) |
   MSTDir[V=15,A=40]| 25.81 |   21.16 (0.00) |  21.06 (0.01) |
 MSTUndir[V=13,A=40]| 12.86 |   11.47 (0.00) |  11.31 (0.01) |
 MSTUndir[V=15,A=40]|214.87 |  188.61 (0.01) | 185.37 (0.01) |
         TIMETABLING|  9.63 |   10.63 (0.00) |  10.98 (0.01) |
--------------------+-------+ ---------------+---------------+

Gerald