[Bug target/81616] Update -mtune=generic for the current Intel and AMD processors

["hubicka at ucw dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81616

--- Comment #25 from Jan Hubicka <hubicka at ucw dot cz> ---
Hi,
I agree that the matric multiplication fma issue is important and hopefully it
will be fixed for GCC 8.  See
https://gcc.gnu.org/ml/gcc-patches/2017-11/msg00437.html

The irregularity of tune/arch is probably originating from enabling/disabling
fma
and avx256 preferrence.  I get
jh@d136:~> /home/jh/trunk-install-new3/bin/gcc -Ofast -march=native -mno-fma
mult.c
jh@d136:~> ./a.out
        mult took     193593 clocks
jh@d136:~> /home/jh/trunk-install-new3/bin/gcc -Ofast -march=native -mno-fma
-mprefer-vector-width=256 mult.c
jh@d136:~> ./a.out
        mult took     104745 clocks
jh@d136:~> /home/jh/trunk-install-new3/bin/gcc -Ofast -march=haswell
-mprefer-vector-width=256 mult.c
jh@d136:~> ./a.out
        mult took     160123 clocks
jh@d136:~> /home/jh/trunk-install-new3/bin/gcc -Ofast -march=haswell
-mprefer-vector-width=256 -mno-fma mult.c
jh@d136:~> ./a.out
        mult took     102048 clocks

90% difference on a common loop is quite noticeable.

Continuing my benchmarkings on spec2k.
This is -Ofast -march=native -mprefer-vector-width=none compared to 
-Ofast -march=native -mtune=haswell -mprefer-vector-width=128.
So neither of those are win compared to -mtune=native.

   164.gzip          1400    58.2    2407    *     1400    57.9    2419    *
   175.vpr           1400    37.5    3731    *     1400    37.8    3704    *
   176.gcc           1100    20.0    5494    *     1100    20.0    5497    *
   181.mcf           1800    21.6    8324    *     1800    20.8    8660    *
   186.crafty        1000    20.9    4790    *     1000    21.2    4722    *
   197.parser        1800    51.4    3499    *     1800    51.8    3472    *
   252.eon           1300    19.3    6749    *     1300    18.2    7143    *
   253.perlbmk                               X                             X
   254.gap                                   X                             X
   255.vortex                                X                             X
   256.bzip2         1500    43.1    3483    *     1500    43.5    3444    *
   300.twolf         3000    56.6    5302    *     3000    57.0    5267    *
   Est. SPECint_base2000             4563    
   Est. SPECint2000                                                4591

   168.wupwise       1600    30.9    5179    *     1600    29.7    5387    *
   171.swim          3100    27.4    11309    *     3100    26.4    11739    *
   172.mgrid         1800    31.0    5814    *     1800    26.1    6895    *
   173.applu         2100    25.7    8175    *     2100    25.9    8096    *
   177.mesa          1400    23.3    6006    *     1400    23.3    6001    *
   178.galgel                                X                             X
   179.art           2600    11.0    23702    *     2600    11.0    23718    *
   183.equake        1300    13.0    10033    *     1300    13.1    9944    *
   187.facerec       1900    24.0    7931    *     1900    17.2    11040    *
   188.ammp          2200    34.4    6394    *     2200    35.2    6249    *
   189.lucas         2000    20.3    9864    *     2000    20.8    9603    *
   191.fma3d         2100    31.4    6686    *     2100    30.0    7011    *
   200.sixtrack      1100    41.7    2641    *     1100    38.5    2856    *
   301.apsi          2600    34.1    7630    *     2600    34.2    7612    *
   Est. SPECfp_base2000              7570
   Est. SPECfp2000                                                 7947