[PATCH] D65259: fix typedef issue for offset relocation

[Yonghong Song via Phabricator via llvm-commits]

yonghong-song created this revision.
yonghong-song added a reviewer: ast.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Currently, the CO-RE offset relocation does not work
if any struct/union member or array element is a typedef.
For example,

  typedef const int arr_t[7];
  struct input {
      arr_t a;
  };
  func(...) {
       struct input *in = ...;
       ... __builtin_preserve_access_index(&in->a[1]) ...
  }

The BPF backend calculated default offset is 0 while
4 is the correct answer. Similar issues exist for struct/union
typedef's.

When getting struct/union member or array element type,
we should trace down to the type by skipping typedef
and qualifiers const/volatile as this is what clang did
 to generate getelementptr instructions.
(const/volatile member type qualifiers are already
ignored by clang.)

This patch fixed this issue, for each access index,
skipping typedef and const/volatile/restrict BTF types.


Repository:
  rL LLVM

https://reviews.llvm.org/D65259

Files:
  lib/Target/BPF/BTFDebug.cpp
  lib/Target/BPF/BTFDebug.h
  test/CodeGen/BPF/CORE/offset-reloc-typedef-array.ll
  test/CodeGen/BPF/CORE/offset-reloc-typedef-struct.ll
  test/CodeGen/BPF/CORE/offset-reloc-typedef-union.ll
  test/CodeGen/BPF/CORE/offset-reloc-typedef.ll

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