[Bug c++/112795] [C++>=14] ICE pragma GCC unroll (n) cxx_eval_constant_expression

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112795

--- Comment #8 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:5b651cf6bf1903dd3a4a5ce8c2a95d0e76ee0089

commit r13-8124-g5b651cf6bf1903dd3a4a5ce8c2a95d0e76ee0089
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Mon Dec 4 08:59:15 2023 +0100

    c++: #pragma GCC unroll C++ fixes [PR112795]

    foo in the unroll-5.C testcase ICEs because cp_parser_pragma_unroll
    during parsing calls maybe_constant_value unconditionally, which is
    fine if !processing_template_decl, but can ICE otherwise.

    While just calling fold_non_dependent_expr there instead could be enough
    to fix the ICE (and I guess the right thing to do for backports if any),
    I don't see a reason why we couldn't handle a dependent #pragma GCC unroll
    argument as well, the unrolling isn't done in the FE and all the middle-end
    cares about is that ANNOTATE_EXPR has a 1..65534 last operand when it is
    annot_expr_unroll_kind.

    So, the following patch changes all the unsigned short unroll arguments
    to tree unroll (and thus avoids the tree -> unsigned short -> tree
    conversions), does the type and value checking during parsing only if
    the argument isn't dependent and repeats it during instantiation.

    2023-12-04  Jakub Jelinek  <jakub@redhat.com>

            PR c++/112795
    gcc/cp/
            * parser.cc (cp_parser_pragma_unroll): Use fold_non_dependent_expr
            instead of maybe_constant_value.
    gcc/testsuite/
            * g++.dg/ext/unroll-5.C: New test.

    (cherry picked from commit b6c78feea08c36e5754818c6a3d7536b3f8913dc)