On Wed, Jan 24, 2018 at 6:22 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> cxx_eval_outermost_constant_expr clears TREE_CONSTANT on ADDR_EXPRs that
> aren't considered by C++ constant expressions, but that breaks middle-end
> which relies on TREE_CONSTANT being set on ADDR_EXPR where the address
> is constant.
>
> The following patch just special cases ADDR_EXPR not to clear it.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> As I wrote in the PR, another option would be to restore TREE_CONSTANT
> during genericization if it was cleared earlier in the FE.
>
> 2018-01-24 Jakub Jelinek <ja...@redhat.com>
>
> PR c++/83993
> * constexpr.c (cxx_eval_outermost_constant_expr): Don't clear
> TREE_CONSTANT on ADDR_EXPRs.
>
> * g++.dg/init/pr83993-2.C: New test.
>
> --- gcc/cp/constexpr.c.jj 2018-01-24 13:38:40.572913190 +0100
> +++ gcc/cp/constexpr.c 2018-01-24 17:03:16.821440047 +0100
> @@ -4832,7 +4832,7 @@ cxx_eval_outermost_constant_expr (tree t
>
> if (non_constant_p && !allow_non_constant)
> return error_mark_node;
> - else if (non_constant_p && TREE_CONSTANT (r))
> + else if (non_constant_p && TREE_CONSTANT (r) && TREE_CODE (r) != ADDR_EXPR)
> {
> /* This isn't actually constant, so unset TREE_CONSTANT. */
> if (EXPR_P (r))
Hmm, what if we check for ADDR_EXPR in the EXPR_P test, so we build a
non-TREE_CONSTANT NOP_EXPR around the ADDR_EXPR instead?
Jason
