Question on cfg_remove_useless_stmts_bb

[Richard Kenner]

      if (TREE_CODE (stmt) == ASM_EXPR
          || (TREE_CODE (stmt) == MODIFY_EXPR
              && (TREE_OPERAND (stmt, 0) == var
                  || TREE_CODE (stmt, 0) == val)))

    Ought to do the trick.

In this case, yes, but I'm not convinced that it's complete.  Couldn't
VAL be a more complex expression here and we have to verify that none of
its operands were modified?  That issue is basically the other motivation
for my query (the primary one being, of course, "how did this ever work?"!).