[Bug c++/110997] New: [13/14 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[Bug c++/110997] New: [13/14 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

            Bug ID: 110997
           Summary: [13/14 Regression] internal compiler error: in
                    cxx_eval_constant_expression, at cp/constexpr.cc:8005
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

While workin' on P2564 I found this ICE:

// P2564R3
// { dg-do compile { target c++20 } }
// From clang's cxx2b-consteval-propagate.cpp.  This test ICEd when I worked on
// P2564.

consteval int f (int);

struct S {
  int a = 0;
  int b = f (a);
};

constexpr bool
g (auto i)
{
  S s{i};
  return s.b == 2 *i;
}

consteval int
f (int i)
{
  return 2 * i;
}

void
test ()
{
  static_assert(g(42));
}


$ ./cc1plus -quiet -std=c++20 consteval-prop4.C
consteval-prop4.C: In instantiation of ‘constexpr bool g(auto:1) [with auto:1 =
int]’:
consteval-prop4.C:29:18:   required from here
consteval-prop4.C:16:5: internal compiler error: in
cxx_eval_constant_expression, at cp/constexpr.cc:8005
   16 |   S s{i};
      |     ^
0xdb5f20 cxx_eval_constant_expression
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:8005
0xdac220 cxx_eval_indirect_ref
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:5735
0xdb3a7a cxx_eval_constant_expression
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:7471
0xda66a6 cxx_eval_component_reference
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:4363
0xdb4109 cxx_eval_constant_expression
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:7644
0xd9bc4a cxx_bind_parameters_in_call
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:1830
0xda093c cxx_eval_call_expression
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:2926
0xdb2626 cxx_eval_constant_expression
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:7196
0xdb8143 cxx_eval_outermost_constant_expr
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:8438
0xdb8dc8 cxx_constant_value(tree_node*, tree_node*, int)
        /home/mpolacek/src/gcc/gcc/cp/constexpr.cc:8594
0x1133fda bot_replace
        /home/mpolacek/src/gcc/gcc/cp/tree.cc:3302
0x1df1281 walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*,
tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*))
        /home/mpolacek/src/gcc/gcc/tree.cc:11341
0x113410d break_out_target_exprs(tree_node*, bool)
        /home/mpolacek/src/gcc/gcc/cp/tree.cc:3337
0xeca1b1 get_nsdmi(tree_node*, bool, int)
        /home/mpolacek/src/gcc/gcc/cp/init.cc:693
0x1189148 process_init_constructor_record
        /home/mpolacek/src/gcc/gcc/cp/typeck2.cc:1827
0x118a406 process_init_constructor
        /home/mpolacek/src/gcc/gcc/cp/typeck2.cc:2094
0x11874da digest_init_r
        /home/mpolacek/src/gcc/gcc/cp/typeck2.cc:1358
0x11876e9 digest_init_flags(tree_node*, tree_node*, int, int)
        /home/mpolacek/src/gcc/gcc/cp/typeck2.cc:1404
0x11852ac store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        /home/mpolacek/src/gcc/gcc/cp/typeck2.cc:848
0xe4f3af check_initializer
        /home/mpolacek/src/gcc/gcc/cp/decl.cc:7595

[Bug c++/110997] [13/14 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code
   Target Milestone|---                         |13.3
                 CC|                            |jason at gcc dot gnu.org
           Priority|P3                          |P2
             Blocks|                            |107687

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started with r13-3256:

commit 9bf74082bc93226e1ceb66430706e957e460c841
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Oct 7 20:34:53 2022 -0400

    c++: defer all consteval in default args [DR2631]


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107687
[Bug 107687] [C++23] P2564 - consteval needs to propagate up

[Bug c++/110997] [13/14 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-08-11

[Bug c++/110997] [13/14 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

[Bug c++/110997] [13/14 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
The ICE was fixed by r14-4140-g6851e3423c2b5e.

[Bug c++/110997] [13/14 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:1f1c432226cf3db399b2a2a627e3c5720b02b1d6

commit r14-6129-g1f1c432226cf3db399b2a2a627e3c5720b02b1d6
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Sep 19 16:31:17 2023 -0400

    c++: implement P2564, consteval needs to propagate up [PR107687]

    This patch implements P2564, described at <wg21.link/p2564>, whereby
    certain functions are promoted to consteval.  For example:

      consteval int id(int i) { return i; }

      template <typename T>
      constexpr int f(T t)
      {
        return t + id(t); // id causes f<int> to be promoted to consteval
      }

      void g(int i)
      {
        f (3);
      }

    now compiles.  Previously the code was ill-formed: we would complain
    that 't' in 'f' is not a constant expression.  Since 'f' is now
    consteval, it means that the call to id(t) is in an immediate context,
    so doesn't have to produce a constant -- this is how we allow consteval
    functions composition.  But making 'f<int>' consteval also means that
    the call to 'f' in 'g' must yield a constant; failure to do so results
    in an error.  I made the effort to have cc1plus explain to us what's
    going on.  For example, calling f(i) produces this neat diagnostic:

    w.C:11:11: error: call to consteval function 'f<int>(i)' is not a constant
expression
       11 |         f (i);
          |         ~~^~~
    w.C:11:11: error: 'i' is not a constant expression
    w.C:6:22: note: 'constexpr int f(T) [with T = int]' was promoted to an
immediate function because its body contains an immediate-escalating expression
'id(t)'
        6 |         return t + id(t); // id causes f<int> to be promoted to
consteval
          |                    ~~^~~

    which hopefully makes it clear what's going on.

    Implementing this proposal has been tricky.  One problem was delayed
    instantiation: instantiating a function can set off a domino effect
    where one call promotes a function to consteval but that then means
    that another function should also be promoted, etc.

    In v1, I addressed the delayed instantiation problem by instantiating
    trees early, so that we can escalate functions right away.  That caused
    a number of problems, and in certain cases, like consteval-prop3.C, it
    can't work, because we need to wait till EOF to see the definition of
    the function anyway.  Overeager instantiation tends to cause diagnostic
    problems too.

    In v2, I attempted to move the escalation to the gimplifier, at which
    point all templates have been instantiated.  That attempt flopped,
    however, because once we've gimplified a function, its body is discarded
    and as a consequence, you can no longer evaluate a call to that function
    which is required for escalating, which needs to decide if a call is
    a constant expression or not.

    Therefore, we have to perform the escalation before gimplifying, but
    after instantiate_pending_templates.  That's not easy because we have
    no way to walk all the trees.  In the v2 patch, I use two vectors: one
    to store function decls that may become consteval, and another to
    remember references to immediate-escalating functions.  Unfortunately
    the latter must also stash functions that call immediate-escalating
    functions.  Consider:

      int g(int i)
      {
        f<int>(i); // f is immediate-escalating
      }

    where g itself is not immediate-escalating, but we have to make sure
    that if f gets promoted to consteval, we give an error.

    A new option, -fno-immediate-escalation, is provided to suppress
    escalating functions.

    v2 also adds a new flag, DECL_ESCALATION_CHECKED_P, so that we don't
    escalate a function multiple times, and so that we can distinguish between
    explicitly consteval functions and functions that have been promoted
    to consteval.

    In v3, I removed one of the new vectors and changed the other one
    to a hash set.  This version also contains numerous cleanups.

    v4 merges find_escalating_expr_r into cp_fold_immediate_r.  It also
    adds a new optimization in cp_fold_function.

    v5 greatly simplifies the code.

    v6 simplifies the code further and removes an ff_ flag.

    v7 removes maybe_promote_function_to_consteval and further simplifies
    cp_fold_immediate_r logic.

    v8 removes maybe_store_immediate_escalating_fn.

            PR c++/107687
            PR c++/110997

    gcc/c-family/ChangeLog:

            * c-cppbuiltin.cc (c_cpp_builtins): Update __cpp_consteval.
            * c-opts.cc (c_common_post_options): Pre-C++20, unset
            flag_immediate_escalation.
            * c.opt (fimmediate-escalation): New option.

    gcc/cp/ChangeLog:

            * call.cc (in_immediate_context): No longer static.
            * constexpr.cc (cxx_eval_call_expression): Adjust assert.
            * cp-gimplify.cc (deferred_escalating_exprs): New vec.
            (remember_escalating_expr): New.
            (enum fold_flags): Remove ff_fold_immediate.
            (immediate_escalating_function_p): New.
            (unchecked_immediate_escalating_function_p): New.
            (promote_function_to_consteval): New.
            (cp_fold_immediate): Move above.  Return non-null if any errors
were
            emitted.
            (maybe_explain_promoted_consteval): New.
            (cp_gimplify_expr) <case CALL_EXPR>: Assert we've handled all
            immediate invocations.
            (taking_address_of_imm_fn_error): New.
            (cp_fold_immediate_r): Merge ADDR_EXPR and PTRMEM_CST cases. 
Implement
            P2564 - promoting functions to consteval.
            <case CALL_EXPR>: Implement P2564 - promoting functions to
consteval.
            (cp_fold_r): If an expression turns into a CALL_EXPR after cp_fold,
            call cp_fold_immediate_r on the CALL_EXPR.
            (cp_fold_function): Set DECL_ESCALATION_CHECKED_P if
            deferred_escalating_exprs does not contain current_function_decl.
            (process_and_check_pending_immediate_escalating_fns): New.
            * cp-tree.h (struct lang_decl_fn): Add escalated_p bit-field.
            (DECL_ESCALATION_CHECKED_P): New.
            (immediate_invocation_p): Declare.
            (process_pending_immediate_escalating_fns): Likewise.
            * decl2.cc (c_parse_final_cleanups): Set at_eof to 2 after all
            templates have been instantiated; and to 3 at the end of the
function.
            Call process_pending_immediate_escalating_fns.
            * error.cc (dump_template_bindings): Check at_eof against an
updated
            value.
            * module.cc (trees_out::lang_decl_bools): Stream escalated_p.
            (trees_in::lang_decl_bools): Likewise.
            * pt.cc (push_tinst_level_loc): Set at_eof to 3, not 2.
            * typeck.cc (cp_build_addr_expr_1): Don't check
            DECL_IMMEDIATE_FUNCTION_P.

    gcc/ChangeLog:

            * doc/invoke.texi: Document -fno-immediate-escalation.

    libstdc++-v3/ChangeLog:

            * testsuite/18_support/comparisons/categories/zero_neg.cc: Add
            dg-prune-output.
            * testsuite/std/format/string_neg.cc: Add dg-error.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp23/consteval-if10.C: Remove dg-error.
            * g++.dg/cpp23/consteval-if2.C: Likewise.
            * g++.dg/cpp23/feat-cxx2b.C: Adjust expected value of
__cpp_consteval.
            * g++.dg/cpp26/feat-cxx26.C: Likewise.
            * g++.dg/cpp2a/consteval-memfn1.C: Add dg-error.
            * g++.dg/cpp2a/consteval11.C: Likewise.
            * g++.dg/cpp2a/consteval3.C: Adjust dg-error.
            * g++.dg/cpp2a/consteval34.C: Add dg-error.
            * g++.dg/cpp2a/consteval36.C: Likewise.
            * g++.dg/cpp2a/consteval9.C: Likewise.
            * g++.dg/cpp2a/feat-cxx2a.C: Adjust expected value of
__cpp_consteval.
            * g++.dg/cpp2a/spaceship-synth9.C: Adjust dg-error.
            * g++.dg/cpp2a/consteval-prop1.C: New test.
            * g++.dg/cpp2a/consteval-prop10.C: New test.
            * g++.dg/cpp2a/consteval-prop11.C: New test.
            * g++.dg/cpp2a/consteval-prop12.C: New test.
            * g++.dg/cpp2a/consteval-prop13.C: New test.
            * g++.dg/cpp2a/consteval-prop14.C: New test.
            * g++.dg/cpp2a/consteval-prop15.C: New test.
            * g++.dg/cpp2a/consteval-prop16.C: New test.
            * g++.dg/cpp2a/consteval-prop17.C: New test.
            * g++.dg/cpp2a/consteval-prop18.C: New test.
            * g++.dg/cpp2a/consteval-prop19.C: New test.
            * g++.dg/cpp2a/consteval-prop20.C: New test.
            * g++.dg/cpp2a/consteval-prop2.C: New test.
            * g++.dg/cpp2a/consteval-prop3.C: New test.
            * g++.dg/cpp2a/consteval-prop4.C: New test.
            * g++.dg/cpp2a/consteval-prop5.C: New test.
            * g++.dg/cpp2a/consteval-prop6.C: New test.
            * g++.dg/cpp2a/consteval-prop7.C: New test.
            * g++.dg/cpp2a/consteval-prop8.C: New test.
            * g++.dg/cpp2a/consteval-prop9.C: New test.

[Bug c++/110997] [13/14 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.

[Bug c++/110997] [13/14 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Hmm, the target milestone is set to 13.3.0 but only references patches which
have gone in for gcc 14 only ....

[Bug c++/110997] [13 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|FIXED                       |---
            Summary|[13/14 Regression] internal |[13 Regression] internal
                   |compiler error: in          |compiler error: in
                   |cxx_eval_constant_expressio |cxx_eval_constant_expressio
                   |n, at cp/constexpr.cc:8005  |n, at cp/constexpr.cc:8005
             Status|RESOLVED                    |ASSIGNED
      Known to work|                            |14.0

[Bug c++/110997] [13 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ephraim.feldblum at redis dot com

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 113368 has been marked as a duplicate of this bug. ***

[Bug c++/110997] [13 Regression] internal compiler error: in cxx_eval_constant_expression, at cp/constexpr.cc:8005

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110997

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |NEW
           Assignee|mpolacek at gcc dot gnu.org        |unassigned at gcc dot gnu.org

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I do not think that r14-4140-g6851e3423c2b5e is backportable to 13.