[Bug tree-optimization/115157] New: incorrect TBAA for derived types involving enum types

[Bug tree-optimization/115157] New: incorrect TBAA for derived types involving enum types

[muecker at gwdg dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115157

            Bug ID: 115157
           Summary: incorrect TBAA for derived types involving enum types
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: muecker at gwdg dot de
  Target Milestone: ---

Another example where TBAA does not seem to work correctly similar to PR114959.
I guess here it should be easier to set TYPE_CANONICAL correctly in the FE, but
we have the same completion issues we also have in C23 with other tagged types.

https://godbolt.org/z/qcWxn9f6z

enum E { E1 = -1, E2 = 0, E3 = 1 };

typedef int A;
typedef enum E B;

_Static_assert(_Generic((A){ 0 }, B: 1), "");

void* foo(void* a, void *b, A *c, B *d)
{
        *(A**)a = c;
        *(B**)b = d;
        return *(A**)a;
}

int main()
{
        A *a, b, c;
        if (&c != (A*)foo(&a, &a, &b, &c))
                __builtin_abort();
}

[Bug tree-optimization/115157] incorrect TBAA for derived types involving enum types

[uecker at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115157

uecker at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |uecker at gcc dot gnu.org

--- Comment #1 from uecker at gcc dot gnu.org ---
Created attachment 58246
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58246&action=edit
patch


Candidate patch by setting TYPE_CANONICAL based on the underlying type.

[Bug tree-optimization/115157] incorrect TBAA for derived types involving enum types

[muecker at gwdg dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115157

--- Comment #2 from Martin Uecker <muecker at gwdg dot de> ---
PATCH: https://gcc.gnu.org/pipermail/gcc-patches/2024-May/652669.html

[Bug tree-optimization/115157] incorrect TBAA for derived types involving enum types

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115157

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Uecker <uecker@gcc.gnu.org>:

https://gcc.gnu.org/g:867d1264fe71d4291194373d1a1c409cac97a597

commit r15-933-g867d1264fe71d4291194373d1a1c409cac97a597
Author: Martin Uecker <uecker@tugraz.at>
Date:   Sun May 19 23:13:22 2024 +0200

    C: allow aliasing of compatible types derived from enumeral types
[PR115157]

    Aliasing of enumeral types with the underlying integer is now allowed
    by setting the aliasing set to zero.  But this does not allow aliasing
    of derived types which are compatible as required by ISO C.  Instead,
    initially set structural equality.  Then set TYPE_CANONICAL and update
    pointers and main variants when the type is completed (as done for
    structures and unions in C23).

            PR tree-optimization/115157
            PR tree-optimization/115177

    gcc/c/
            * c-decl.cc (shadow_tag-warned,parse_xref_tag,start_enum,
            finish_enum): Set SET_TYPE_STRUCTURAL_EQUALITY / TYPE_CANONICAL.
            * c-objc-common.cc (get_alias_set): Remove special case.
            (get_aka_type): Add special case.

    gcc/c-family/
            * c-attribs.cc (handle_hardbool_attribute): Set TYPE_CANONICAL
            for hardbools.

    gcc/
            * godump.cc (go_output_typedef): Use TYPE_MAIN_VARIANT instead
            of TYPE_CANONICAL.

    gcc/testsuite/
            * gcc.dg/enum-alias-1.c: New test.
            * gcc.dg/enum-alias-2.c: New test.
            * gcc.dg/enum-alias-3.c: New test.
            * gcc.dg/enum-alias-4.c: New test.

[Bug tree-optimization/115157] incorrect TBAA for derived types involving enum types

[rearnsha at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115157

--- Comment #4 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
The tests in the last patch fail on arm-eabi. The tests assume that
sizeof(enum) == sizeof(int), which is not true if -fshort-enum is the default.

++++++++++++++++++++++++++++++++++++++++++++++++
+ Changes for ./gcc/testsuite/gcc/gcc.sum.sent +
++++++++++++++++++++++++++++++++++++++++++++++++

New tests that FAIL (6 tests):

arm-qemu/-mthumb: gcc: gcc.dg/enum-alias-1.c (test for excess errors)
arm-qemu/-mthumb: gcc: gcc.dg/enum-alias-2.c execution test
arm-qemu/-mthumb: gcc: gcc.dg/enum-alias-3.c execution test