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From: "david.faust at oracle dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/107480] New: bpf: add __builtin_preserve_type_info
Date: Mon, 31 Oct 2022 20:27:24 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107480

            Bug ID: 107480
           Summary: bpf: add __builtin_preserve_type_info
           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 BPF builtin:
  __builtin_preserve_type_info (param, flag)

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

This builtin produces a relocation recording the information
about the type of 'param', such as it's size or whether or
not it exists on the host kernel, according to 'flag'. This
information is returned to the program and patched by the
eBPF loader during loading.

We should support this functionality in GCC.

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