[Bug tree-optimization/68021] [6 Regression] ice in rewrite_use_nonlinear_expr with -O3

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68021

--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #11)
> void bar (void);
> 
> void
> foo (int p2, int p3)
> {
>   unsigned long a = p2;
>   unsigned long b = (~(unsigned long) ((unsigned int) p3 + -1U)) + a;
>   unsigned long c = (a - (unsigned long) ((unsigned int) p3 + -1U)) + (-1UL);
>   if (b != c)
>     bar ();
> }
> 
> shows this folding inconsistency in the *.original dump:
>   long unsigned int a = (long unsigned int) p2;
>   long unsigned int b = (a - (long unsigned int) ((unsigned int) p3 +
> 4294967295)) - 1;
>   long unsigned int c = (a - (long unsigned int) ((unsigned int) p3 +
> 4294967295)) + 18446744073709551615;
> but *.gimple already canonicalizes it, so that it does +
> 18446744073709551615 at the end in both cases.

associate_trees doesn't re-fold the result (due to fear of recursion I guess)