fn: gcc.Function('helper_function')
fn.decl.name: 'helper_function'
CFG:
  BLOCK 0
  BLOCK 1
  BLOCK 2
  gimple[0]:
    str(stmt): 'if (a < b)'
    repr(stmt): 'gcc.GimpleCond()'
    stmt.lhs: gcc.ParmDecl('a')
    stmt.exprcode: <type 'gcc.LtExpr'>
    stmt.rhs: gcc.ParmDecl('b')
    stmt.true_label: None
    stmt.false_label: None
  BLOCK 3
  gimple[0]:
    str(stmt): 'D.nnnnn = 42;'
    repr(stmt): 'gcc.GimpleAssign()'
  BLOCK 4
  gimple[0]:
    str(stmt): 'D.nnnnn = a - b;'
    repr(stmt): 'gcc.GimpleAssign()'
  BLOCK 5
  gimple[0]:
    str(stmt): 'return D.nnnnn;'
    repr(stmt): 'gcc.GimpleReturn()'