[Bug rtl-optimization/66248] subreg truncation not hoisted from loop

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66248

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Couldn't it be optimized as:
short func(short *a, int y)
{
 short ret = 0;
 unsigned int tmp = 0;
 int i;
 for(i = 0; i < y; i++) 
   tmp += (unsigned int)(int)a[i];

 return (short)tmp;
}

Such that the addition happens in unsigned (so there is only wrapping and is
well defined) and only one truncatation happens at the end of the loop.