Re: [C++ PATCH] Handle CASE_HIGH in constexpr evaluation (PR c++/72868)

[Jason Merrill <jason@redhat.com>]

OK for trunk and 6.

On Thu, Aug 11, 2016 at 10:55 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> As mentioned in the PR, constexpr.c has been handling cases with ranges
> just as the lowest value of the range.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?  What about 6.2 (not a regression, but low risk fix for wrong-code)?
>
> 2016-08-11  Jakub Jelinek  <jakub@redhat.com>
>
>         PR c++/72868
>         * constexpr.c (label_matches): Handle case range expressions.
>
>         * g++.dg/cpp1y/constexpr-switch4.C: New test.
>
> --- gcc/cp/constexpr.c.jj       2016-08-10 00:21:07.000000000 +0200
> +++ gcc/cp/constexpr.c  2016-08-10 22:17:16.577041975 +0200
> @@ -3448,6 +3448,12 @@ label_matches (tree *jump_target, tree_s
>         {
>           if (!CASE_LOW (stmt))
>             default_label = i;
> +         else if (CASE_HIGH (stmt))
> +           {
> +             if (tree_int_cst_le (CASE_LOW (stmt), *jump_target)
> +                 && tree_int_cst_le (*jump_target, CASE_HIGH (stmt)))
> +               return true;
> +           }
>           else if (tree_int_cst_equal (*jump_target, CASE_LOW (stmt)))
>             return true;
>         }
> --- gcc/testsuite/g++.dg/cpp1y/constexpr-switch4.C.jj   2016-08-10 22:22:29.567129868 +0200
> +++ gcc/testsuite/g++.dg/cpp1y/constexpr-switch4.C      2016-08-10 22:23:25.104435699 +0200
> @@ -0,0 +1,27 @@
> +// PR c++/72868
> +// { dg-do compile }
> +// { dg-options "-std=gnu++14" }
> +
> +constexpr int
> +foo (int i)
> +{
> +  switch (i)
> +    {
> +    case 11 ... 12:
> +      return 4;
> +    case 0 ... 9:
> +      return 3;
> +    default:
> +      return 7;
> +    }
> +}
> +
> +#define SA(X) static_assert((X),#X)
> +SA (foo (-1) == 7);
> +SA (foo (0) == 3);
> +SA (foo (3) == 3);
> +SA (foo (9) == 3);
> +SA (foo (10) == 7);
> +SA (foo (11) == 4);
> +SA (foo (12) == 4);
> +SA (foo (13) == 7);
>
>         Jakub