[patch] PR tree-optimization/96818 - cast label range to type of switch operand

[Richard Biener]

On Mon, Aug 31, 2020 at 10:39 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Mon, Aug 31, 2020 at 10:33:20AM +0200, Richard Biener wrote:
> > In any case type mismatches here are of course unfortunate
> > and both more verification and documentation would be
> > nice.  verify_gimple_switch only verifies all case labels
> > have the same type, the type of the switch argument is
> > not verified in any way against that type.
>
> When looking at the verification, I have noticed a bug in it.
>
> The verification that CASE_HIGH (if present) has the same type as CASE_LOW
> is only performed for the case label 2 and higher, case label 1 (the first
> one after the default label) isn't checked.
>
> The following patch fixes that, it will uselessly also compare
> TREE_TYPE (CASE_LOW (elt)) != elt_type for the case label 1, but I think
> that isn't that expensive and helps readability of the code.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

> 2020-08-31  Jakub Jelinek  <jakub@redhat.com>
>
>         * tree-cfg.c (verify_gimple_switch): If the first non-default case
>         label has CASE_HIGH, verify it has the same type as CASE_LOW.
>
> --- gcc/tree-cfg.c.jj   2020-08-27 18:42:35.660711349 +0200
> +++ gcc/tree-cfg.c      2020-08-27 22:46:34.574154370 +0200
> @@ -4809,17 +4809,7 @@ verify_gimple_switch (gswitch *stmt)
>           return true;
>         }
>
> -      if (elt_type)
> -       {
> -         if (TREE_TYPE (CASE_LOW (elt)) != elt_type
> -             || (CASE_HIGH (elt) && TREE_TYPE (CASE_HIGH (elt)) != elt_type))
> -           {
> -             error ("type mismatch for case label in switch statement");
> -             debug_generic_expr (elt);
> -             return true;
> -           }
> -       }
> -      else
> +      if (! elt_type)
>         {
>           elt_type = TREE_TYPE (CASE_LOW (elt));
>           if (TYPE_PRECISION (index_type) < TYPE_PRECISION (elt_type))
> @@ -4828,6 +4818,13 @@ verify_gimple_switch (gswitch *stmt)
>               return true;
>             }
>         }
> +      if (TREE_TYPE (CASE_LOW (elt)) != elt_type
> +          || (CASE_HIGH (elt) && TREE_TYPE (CASE_HIGH (elt)) != elt_type))
> +       {
> +         error ("type mismatch for case label in switch statement");
> +         debug_generic_expr (elt);
> +         return true;
> +       }
>
>        if (prev_upper_bound)
>         {
>
>
>         Jakub
>