[Bug other/60486] [avr] missed optimization on detecting zero flag set

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60486

--- Comment #3 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
Here is a smaller test case with similar artifact (insn #7):

extern void foo (unsigned);
char v;

void pr_60486 (unsigned z)
{
  if (--z == 0)
     v = 0;
  foo (z);
}


pr_60486:
    sbiw r24,1     ;  6    addhi3_clobber/1    [length = 1]
    sbiw r24,0     ;  7    *cmphi/1    [length = 1]
    brne .L9     ;  8    branch    [length = 1]
    sts v,__zero_reg__     ;  10    movqi_insn/3    [length = 2]
.L9:
    rjmp foo     ;  14    call_insn/4    [length = 1]