[Bug target/107481] New: bpf: add __builtin_preserve_enum_value

[Bug target/107481] New: bpf: add __builtin_preserve_enum_value

[david.faust at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107481

            Bug ID: 107481
           Summary: bpf: add __builtin_preserve_enum_value
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david.faust at oracle dot com
  Target Milestone: ---

LLVM supports a builtin:
  __builtin_preserve_enum_value (param, flag)

which is used to generate additional relocations for the
Compile Once - Run Everywhere (CO-RE) mechanism.

This builtin produces a CO-RE relocation recording information
about the enumerator value in 'param' according to 'flag', and
returns that information to the program. For example, the
integer value of the enumerator, or a boolean value representing
whether or not that enumerator exists on the host kernel. These
values are patched by the eBPF loader according to the CO-RE
relocation.

We should support the same functionality in GCC.

These are the relevant changes in LLVM:
  https://reviews.llvm.org/D83878
  https://reviews.llvm.org/D83242

[Bug target/107481] bpf: add __builtin_preserve_enum_value

[jemarch at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107481

Jose E. Marchesi <jemarch at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jemarch at gcc dot gnu.org
   Last reconfirmed|                            |2023-04-19
           Assignee|unassigned at gcc dot gnu.org      |cupertino.miranda at oracle dot co
                   |                            |m
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1

[Bug target/107481] bpf: add __builtin_preserve_enum_value

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107481

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Cupertino Miranda <cupermir@gcc.gnu.org>:

https://gcc.gnu.org/g:e0a81559c198153923f0a1a3be7c25df545f3964

commit r14-2962-ge0a81559c198153923f0a1a3be7c25df545f3964
Author: Cupertino Miranda <cupertino.miranda@oracle.com>
Date:   Thu Apr 6 15:22:48 2023 +0100

    bpf: Implementation of BPF CO-RE builtins

    This patch updates the support for the BPF CO-RE builtins
    __builtin_preserve_access_index and __builtin_preserve_field_info,
    and adds support for the CO-RE builtins __builtin_btf_type_id,
    __builtin_preserve_type_info and __builtin_preserve_enum_value.

    These CO-RE relocations are now converted to __builtin_core_reloc which
    abstracts all of the original builtins in a polymorphic relocation
    specific builtin.

    The builtin processing is now split in 2 stages, the first (pack) is
    executed right after the front-end and the second (process) right before
    the asm output.

    In expand pass the __builtin_core_reloc is converted to a
    unspec:UNSPEC_CORE_RELOC rtx entry.

    The data required to process the builtin is now collected in the packing
    stage (after front-end), not allowing the compiler to optimize any of
    the relevant information required to compose the relocation when
    necessary.
    At expansion, that information is recovered and CTF/BTF is queried to
    construct the information that will be used in the relocation.
    At this point the relocation is added to specific section and the
    builtin is expanded to the expected default value for the builtin.

    In order to process __builtin_preserve_enum_value, it was necessary to
    hook the front-end to collect the original enum value reference.
    This is needed since the parser folds all the enum values to its
    integer_cst representation.

    More details can be found within the core-builtins.cc.

    Regtested in host x86_64-linux-gnu and target bpf-unknown-none.

    gcc/ChangeLog:

            PR target/107844
            PR target/107479
            PR target/107480
            PR target/107481
            * config.gcc: Added core-builtins.cc and .o files.
            * config/bpf/bpf-passes.def: Removed file.
            * config/bpf/bpf-protos.h (bpf_add_core_reloc,
            bpf_replace_core_move_operands): New prototypes.
            * config/bpf/bpf.cc (enum bpf_builtins, is_attr_preserve_access,
            maybe_make_core_relo, bpf_core_field_info, bpf_core_compute,
            bpf_core_get_index, bpf_core_new_decl, bpf_core_walk,
            bpf_is_valid_preserve_field_info_arg, is_attr_preserve_access,
            handle_attr_preserve, pass_data_bpf_core_attr, pass_bpf_core_attr):
            Removed.
            (def_builtin, bpf_expand_builtin, bpf_resolve_overloaded_builtin):
Changed.
            * config/bpf/bpf.md (define_expand mov<MM:mode>): Changed.
            (mov_reloc_core<mode>): Added.
            * config/bpf/core-builtins.cc (struct cr_builtin, enum
            cr_decision struct cr_local, struct cr_final, struct
            core_builtin_helpers, enum bpf_plugin_states): Added types.
            (builtins_data, core_builtin_helpers, core_builtin_type_defs):
            Added variables.
            (allocate_builtin_data, get_builtin-data, search_builtin_data,
            remove_parser_plugin, compare_same_kind, compare_same_ptr_expr,
            compare_same_ptr_type, is_attr_preserve_access, core_field_info,
            bpf_core_get_index, compute_field_expr,
            pack_field_expr_for_access_index,
pack_field_expr_for_preserve_field,
            process_field_expr, pack_enum_value, process_enum_value, pack_type,
            process_type, bpf_require_core_support, make_core_relo, read_kind,
            kind_access_index, kind_preserve_field_info, kind_enum_value,
            kind_type_id, kind_preserve_type_info,
get_core_builtin_fndecl_for_type,
            bpf_handle_plugin_finish_type, bpf_init_core_builtins,
            construct_builtin_core_reloc, bpf_resolve_overloaded_core_builtin,
            bpf_expand_core_builtin, bpf_add_core_reloc,
            bpf_replace_core_move_operands): Added functions.
            * config/bpf/core-builtins.h (enum bpf_builtins): Added.
            (bpf_init_core_builtins, bpf_expand_core_builtin,
            bpf_resolve_overloaded_core_builtin): Added functions.
            * config/bpf/coreout.cc (struct bpf_core_extra): Added.
            (bpf_core_reloc_add, output_asm_btfext_core_reloc): Changed.
            * config/bpf/coreout.h (bpf_core_reloc_add) Changed prototype.
            * config/bpf/t-bpf: Added core-builtins.o.
            * doc/extend.texi: Added documentation for new BPF builtins.

[Bug target/107481] bpf: add __builtin_preserve_enum_value

[jemarch at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107481

Jose E. Marchesi <jemarch at gcc dot gnu.org> changed:

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

--- Comment #2 from Jose E. Marchesi <jemarch at gcc dot gnu.org> ---
fixed.