@begin: scope:[]  from
  [0] (byte*) screen#0 ← (byte*) 1024
  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 setscreen 
  to:main::@1
main::@1: scope:[main]  from main
  [6] *((byte*) screen#0) ← (byte) 'a'
  [7] call setscreen 
  to:main::@2
main::@2: scope:[main]  from main::@1
  [8] *((byte*) screen#0) ← (byte) 'a'
  to:main::@return
main::@return: scope:[main]  from main::@2
  [9] return 
  to:@return
setscreen: scope:[setscreen]  from main main::@1
  [10] (byte*) setscreen::val#2 ← phi( main/(const byte*) screen1#0 main::@1/(const byte*) screen2#0 )
  [11] *(&(byte*) screen#0) ← (byte*) setscreen::val#2
  to:setscreen::@return
setscreen::@return: scope:[setscreen]  from setscreen
  [12] return 
  to:@return
