@begin: scope:[]  from
  [0] (byte) idx#0 ← (byte) 0
  to:@1
@1: scope:[]  from @begin
  [1] phi()
  [2] call main 
  to:@end
@end: scope:[]  from @1
  [3] phi()
main: scope:[main]  from @1
  [4] phi()
  [5] call fn1 
  [6] *((const byte*) SCREEN#0 + (byte) idx#0) ← (byte) 'a'
  [7] call fn1 
  [8] *((const byte*) SCREEN#0 + (byte) idx#0) ← (byte) 'a'
  to:main::@return
main::@return: scope:[main]  from main
  [9] return 
  to:@return
fn1: scope:[fn1]  from main
  [10] (byte) idx#1 ← ++ (byte) idx#0
  to:fn1::@return
fn1::@return: scope:[fn1]  from fn1
  [11] return 
  to:@return
