[Bug c/93002] New: while(i--) optimization

[getchar_gnu at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93002

            Bug ID: 93002
           Summary: while(i--) optimization
           Product: gcc
           Version: 9.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: getchar_gnu at hotmail dot com
  Target Milestone: ---

while (i--) can be compiled into `sub ecx, 1 / jnc code` rather than `dec ecx /
cmp ecx, -1 / jne code`.

See https://stackoverflow.com/questions/54278070/ for discussion (I'm asker)