[Bug target/80313] New: -march=znver1 produce worse code than -march=haswell

["vincenzo.innocente at cern dot ch" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80313

            Bug ID: 80313
           Summary: -march=znver1 produce worse code than -march=haswell
           Product: gcc
           Version: 7.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vincenzo.innocente at cern dot ch
  Target Milestone: ---

Created attachment 41125
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41125&action=edit
sef contained scimark2 MC benchmark

just got hold of a AMD Ryzen 7 1800X Eight-Core Processor and was surprised by
the results running with -march=native
the point is that the results can be reproduced on a haswell or broadwell as
well!

I used full scimark2,

just the MC benchmark shows at least one problem

this is on intel
[innocent@vinavx3 fullMC]$ gcc -march=znver1 -O3 fullMC.c -g ; time ./a.out
1.245u 0.000s 0:01.24 100.0%    0+0k 0+0io 0pf+0w
[innocent@vinavx3 fullMC]$ gcc -O3 fullMC.c -g ; time ./a.out
0.327u 0.000s 0:00.32 100.0%    0+0k 0+0io 0pf+0w
[innocent@vinavx3 fullMC]$ gcc -march=broadwell -O3 fullMC.c -g ; time ./a.out
0.308u 0.000s 0:00.30 100.0%    0+0k 0+0io 0pf+0w

this is on ryzen
[innocent@vinzen0 fullMC]$ gcc -march=znver1 -O3 fullMC.c -g ; time ./a.out
1.354u 0.001s 0:01.35 100.0%    0+0k 0+0io 0pf+0w
[innocent@vinzen0 fullMC]$ gcc -O3 fullMC.c -g ; time ./a.out
0.315u 0.000s 0:00.31 100.0%    0+0k 0+0io 0pf+0w
[innocent@vinzen0 fullMC]$ gcc -march=broadwell -O3 fullMC.c -g ; time ./a.out
0.313u 0.001s 0:00.31 100.0%    0+0k 0+0io 0pf+0w