Re: PING fwprop and pr/19653

[Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>]

Bernd Schmidt wrote:
> Paolo Bonzini wrote:
> > fwprop merge, stage 2 project:
> > http://gcc.gnu.org/ml/gcc-patches/2006-02/msg01420.html
> > http://gcc.gnu.org/ml/gcc-patches/2006-02/msg01421.html
>
> I don't yet see a completely convincing argument that this really is a 
> full replacement of cse's path following.  I played with it a little 
> and got a few cases of missed optimizations, but I have no clear data 
> to indicate whether that's a problem.
If you can give them to me, I can play with them.

I must say I *don't* have a convincing argument.  There are clues, 
however, that most things that CSE path following does have already been 
moved to other passes.

1) In 4.2, GCSE was modified to assign value numbers to REG_EQUAL 
notes.  This, plus the change from 1 to 2 GCSE passes, allowed GCSE to 
eliminate redundant address computations.  The last time David Edelsohn 
SPEC-tested these changes on PowerPC, the only serious regression was in 
bzip2 and it's fixed by this change (see 
http://gcc.gnu.org/ml/gcc/2005-09/msg00821.html for a description of the 
problem).

2) Steven Bosscher ran nullstone, and the only problems he found were 
fixed at the tree level (PR23911) and caused by the elimination of the 
fold_rtx code, *not* by the elimination of path following.

3) Other problems revealed by SPEC testing were caused by optimizations 
that CSE should not have done, for example by non-canonical RTL produced 
by expand (http://gcc.gnu.org/ml/gcc-patches/2005-09/msg00863.html).  
These have been fixed as well, the patches are already on mainline.
> Benchmark results of baseline, (baseline + fwprop), and (baseline + 
> fwprop - expensive-parts-of-cse), across as many targets as possible, 
> would be welcome.
SPEC results are neutral on i686-pc-linux-gnu, but I cannot find them 
anymore.  Here are David's old results for PowerPC, before the change to 
fix bzip2.

SPECint, -O2:
164.gzip    1400    242    578    1400    242    579
175.vpr    1400    199    703    1400    197    712
176.gcc    1100    --    X    1100    --    X
181.mcf    1800    183    986    1800    182    990
186.crafty    1000    143    700    1000    144    697
197.parser    1800    326    552    1800    326    552
252.eon    1300    --    X    1300    --    X
253.perlbmk    1800    349    516    1800    347    518
254.gap    1100    178    617    1100    177    622
255.vortex    1900    0,022    X    1900    0,022    X
256.bzip2    1500    197    760    1500    205    732
300.twolf    3000    297    1011    3000    289    1038
           695            696

SPECfp, -O2:                      
168.wupwise    1600    232    691    1600    233    686
171.swim    3100    395    785    3100    385    806
172.mgrid    1800    439    410    1800    438    411
173.applu    2100    372    565    2100    374    562
177.mesa    1400    198    707    1400    198    708
178.galgel    2900    --    X    2900    --    X
179.art    2600    210    1235    2600    211    1230
183.equake    1300    160    810    1300    158    823
187.facerec    1900    247    770    1900    248    766
188.ammp    2200    422    521    2200    425    518
189.lucas    2000    222    901    2000    222    899
191.fma3d    2100    372    564    2100    369    570
200.sixtrack    1100    261    422    1100    260    424
301.apsi    2600    388    670    2600    387    671
           667            668

SPECint, -O3:
164.gzip    1400    248    565    1400    245    571
175.vpr    1400    198    706    1400    194    721
176.gcc    1100    --    X    1100    --    X
181.mcf    1800    174    1033    1800    174    1037
186.crafty    1000    140    712    1000    141    709
197.parser    1800    296    608    1800    296    608
252.eon    1300    --    X    1300    --    X
253.perlbmk    1800    345    522    1800    346    520
254.gap    1100    179    613    1100    181    607
255.vortex    1900    0,022    X    1900    0,022    X
256.bzip2    1500    196    767    1500    197    760
300.twolf    3000    285    1052    3000    296    1014
           710            708
                      
SPECfp, -O3:
168.wupwise    1600    223    717    1600    225    712
171.swim    3100    239    1296    3100    249    1244
172.mgrid    1800    321    561    1800    324    556
173.applu    2100    312    674    2100    312    673
177.mesa    1400    192    730    1400    193    727
178.galgel    2900    --    X    2900    --    X
179.art    2600    188    1383    2600    189    1376
183.equake    1300    142    913    1300    142    915
187.facerec    1900    182    1045    1900    183    1038
188.ammp    2200    403    546    2200    400    550
189.lucas    2000    219    913    2000    221    904
191.fma3d    2100    356    590    2100    351    598
200.sixtrack    1100    232    474    1100    229    481
301.apsi    2600    325    801    2600    331    785
           777            773

If you can run EEMBC on blackfin, that'd be great.
> You'll get bonus points if you can eliminate combine.c too :)
Only if you first eliminate reload.c :-)

Paolo