[Bug target/111332] New: Using GCC7.3.0 and GCC10.3.0 to compile the same test case, assembler file instructions are different and performance fallback is obvious.

["d_vampile at 163 dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111332

            Bug ID: 111332
           Summary: Using GCC7.3.0 and GCC10.3.0 to compile the same test
                    case, assembler file instructions are different and
                    performance fallback is obvious.
           Product: gcc
           Version: 10.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: d_vampile at 163 dot com
  Target Milestone: ---

Created attachment 55850
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55850&action=edit
test case

Created Attachment

Test platform: x86_64

Compiler Options:  
gcc main.c -g -o main -O2 -msse4.2 -mavx2 -fno-inline

Runtime with gcc7.3.0:
$ time ./main_gcc7.3 2000
start to run 2000.
end to run 2000.

real    6m30.461s
user    6m26.587s
sys     0m0.814s


Runtime with gcc10.3.0:
$ time ./main_gcc10.3 2000
start to run 2000.
end to run 2000.

real    7m18.696s
user    7m13.912s
sys     0m1.098s

Programs compiled with gcc10.3.0 run significantly longer than gcc7.3.0