[PATCH] D109560: BPF: change BTF_KIND_TAG format

[Yonghong Song via Phabricator via llvm-commits]

yonghong-song created this revision.
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Previously we have the following binary representation:

  struct bpf_type { name, info, type }
  struct btf_tag { __u32 component_idx; }

If the tag points to a struct/union/var/func type, we will have

  kflag = 1, component_idx = 0 

if the tag points to struct/union member or func argument, we will have

  kflag = 0, component_idx = 0, ..., vlen - 1 

The above rather makes interface complex to have both kflag and 
component needed to determine its legality and index.

This patch simplifies the interface by removing kflag involvement.

  component_idx = (u32)-1 : tag pointing to a type
  component_idx = 0 ... vlen - 1 : tag pointing to a member or argument

and kflag is always 0 and there is no need to check.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D109560

Files:
  llvm/lib/Target/BPF/BTFDebug.cpp
  llvm/test/CodeGen/BPF/BTF/tag-1.ll
  llvm/test/CodeGen/BPF/BTF/tag-2.ll

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