[tree-ssa] tree-ssa vs. fold

[Zack Weinberg]

kenner@vlsi1.ultra.nyu.edu (Richard Kenner) writes:

>     Hum, perhaps.  However, it does seem like we ought be
>     be able to do *something* in the extremely common case of
>     a plain "int" variable.
>
> No, it's the "plain 'int' variable" that is the source of the problem!
>
> Consider:
>
> void
> sub1 (int n)
> {
>    int arr[n];
>
>    n = 10;
>
>      .... sizeof (arr) ...
>
> You want the sizeof to use the value of N on entry, so you need the
> SAVE_EXPR.

Wouldn't this get rewritten immediately as

  void
  sub1 (int n.1)
  {
    int arr[n.1];

    n.2 = 10;

    ... sizeof (arr) ...


as part of the conversion to SSA form?

zw