Re: [pushed] c++: unroll pragma in templates [PR111529]

[Andrew Pinski <pinskia@gmail.com>]

On Fri, Sep 22, 2023 at 6:01 AM Jason Merrill <jason@redhat.com> wrote:
>
> Tested x86_64-pc-linux-gnu, applying to trunk.
>
> -- 8< --
>
> We were failing to handle ANNOTATE_EXPR in tsubst_copy_and_build, leading to
> problems with substitution of any wrapped expressions.
>
> Let's also not tell users that lambda templates are available in C++14.

This part of the patch fixes
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108026 .

>
>         PR c++/111529
>
> gcc/cp/ChangeLog:
>
>         * parser.cc (cp_parser_lambda_declarator_opt): Don't suggest
>         -std=c++14 for lambda templates.
>         * pt.cc (tsubst_expr): Move ANNOTATE_EXPR handling...
>         (tsubst_copy_and_build): ...here.
>
> gcc/testsuite/ChangeLog:
>
>         * g++.dg/ext/unroll-4.C: New test.
> ---
>  gcc/cp/parser.cc                    |  7 ++-----
>  gcc/cp/pt.cc                        | 14 +++++++-------
>  gcc/testsuite/g++.dg/ext/unroll-4.C | 16 ++++++++++++++++
>  3 files changed, 25 insertions(+), 12 deletions(-)
>  create mode 100644 gcc/testsuite/g++.dg/ext/unroll-4.C
>
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index 0e1cbbfe051..f3abae716fe 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -11695,11 +11695,8 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
>       an opening angle if present.  */
>    if (cp_lexer_next_token_is (parser->lexer, CPP_LESS))
>      {
> -      if (cxx_dialect < cxx14)
> -       pedwarn (parser->lexer->next_token->location, OPT_Wc__14_extensions,
> -                "lambda templates are only available with "
> -                "%<-std=c++14%> or %<-std=gnu++14%>");
> -      else if (pedantic && cxx_dialect < cxx20)
> +      if (cxx_dialect < cxx20
> +         && (pedantic || cxx_dialect < cxx14))
>         pedwarn (parser->lexer->next_token->location, OPT_Wc__20_extensions,
>                  "lambda templates are only available with "
>                  "%<-std=c++20%> or %<-std=gnu++20%>");
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 9b100e12a23..ea5379098a5 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -19913,13 +19913,6 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>                                     templated_operator_saved_lookups (t),
>                                     complain));
>
> -    case ANNOTATE_EXPR:
> -      tmp = RECUR (TREE_OPERAND (t, 0));
> -      RETURN (build3_loc (EXPR_LOCATION (t), ANNOTATE_EXPR,
> -                         TREE_TYPE (tmp), tmp,
> -                         RECUR (TREE_OPERAND (t, 1)),
> -                         RECUR (TREE_OPERAND (t, 2))));
> -
>      case PREDICT_EXPR:
>        RETURN (add_stmt (copy_node (t)));
>
> @@ -21868,6 +21861,13 @@ tsubst_copy_and_build (tree t,
>         RETURN (op);
>        }
>
> +    case ANNOTATE_EXPR:
> +      op1 = RECUR (TREE_OPERAND (t, 0));
> +      RETURN (build3_loc (EXPR_LOCATION (t), ANNOTATE_EXPR,
> +                         TREE_TYPE (op1), op1,
> +                         RECUR (TREE_OPERAND (t, 1)),
> +                         RECUR (TREE_OPERAND (t, 2))));
> +
>      default:
>        /* Handle Objective-C++ constructs, if appropriate.  */
>        {
> diff --git a/gcc/testsuite/g++.dg/ext/unroll-4.C b/gcc/testsuite/g++.dg/ext/unroll-4.C
> new file mode 100644
> index 00000000000..d488aca974e
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/unroll-4.C
> @@ -0,0 +1,16 @@
> +// PR c++/111529
> +// { dg-do compile { target c++11 } }
> +// { dg-additional-options -Wno-c++20-extensions }
> +
> +template <int>
> +void f() {
> +  []<int>() {
> +    #pragma GCC unroll 9
> +    for (int i = 1; i; --i) {
> +    }
> +  };
> +}
> +
> +int main() {
> +  f<0>();
> +}
>
> base-commit: 4c496020764057453415f1ae599950724ec0e871
> --
> 2.39.3
>