OK. I wonder why we're returning false for EMPTY_CLASS_EXPR?
On Tue, Nov 5, 2019 at 7:35 AM Jakub Jelinek <ja...@redhat.com> wrote:
>
> Hi!
>
> When Martin Liska added PREDICT_EXPR to potential_constant_expression_1,
> it was with goto in mind and in that case goto isn't a potential
> constant expression, but when the {,un}likely attributes are used on other
> statements, they are valid.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?
>
> 2019-11-05 Jakub Jelinek <ja...@redhat.com>
>
> PR c++/92343
> * constexpr.c (potential_constant_expression_1): Return true rather
> than false for PREDICT_EXPR.
>
> * g++.dg/cpp2a/attr-likely6.C: New test.
>
> --- gcc/cp/constexpr.c.jj 2019-11-02 00:26:48.965846855 +0100
> +++ gcc/cp/constexpr.c 2019-11-04 09:53:35.070621487 +0100
> @@ -6493,6 +6493,7 @@ potential_constant_expression_1 (tree t,
> case LABEL_DECL:
> case LABEL_EXPR:
> case CASE_LABEL_EXPR:
> + case PREDICT_EXPR:
> case CONST_DECL:
> case SIZEOF_EXPR:
> case ALIGNOF_EXPR:
> @@ -7354,7 +7355,6 @@ potential_constant_expression_1 (tree t,
> return true;
>
> case EMPTY_CLASS_EXPR:
> - case PREDICT_EXPR:
> return false;
>
> case GOTO_EXPR:
> --- gcc/testsuite/g++.dg/cpp2a/attr-likely6.C.jj 2019-11-04
> 09:54:50.126485303 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/attr-likely6.C 2019-11-04 09:55:21.001017926
> +0100
> @@ -0,0 +1,14 @@
> +// PR c++/92343
> +// { dg-do compile { target c++14 } }
> +
> +constexpr bool
> +foo (bool x)
> +{
> + if (x)
> + [[unlikely]] return true;
> + else
> + [[likely]] return false;
> +}
> +
> +static_assert (foo (true), "");
> +static_assert (!foo (false), "");
>
> Jakub
