[PATCH] D69761: [BPF] fix a bug in __builtin_preserve_field_info() with FIELD_BYTE_SIZE

[Yonghong Song via Phabricator via llvm-commits]

yonghong-song created this revision.
yonghong-song added reviewers: ast, anakryiko.
Herald added subscribers: llvm-commits, hiraditya, aprantl.
Herald added a project: LLVM.

During deriving proper bitfield access FIELD_BYTE_SIZE,
function Member->getStorageOffsetInBits() is used to
get llvm IR type storage offset in bits so that
the byte size can permit aligned loads/stores with previously
derived FIELD_BYTE_OFFSET.

The function should only be used with bitfield members and it will
assert if ASSERT is turned on during cmake build.

  Constant *getStorageOffsetInBits() const {
    assert(getTag() == dwarf::DW_TAG_member && isBitField());
    if (auto *C = cast_or_null<ConstantAsMetadata>(getExtraData()))
      return C->getValue();
    return nullptr;
  }

This patch fixed the issue by using Member->isBitField()
directly and a test case is added to cover this missing case.
This issue is discovered when running Andrii's linux kernel CO-RE
tests.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D69761

Files:
  llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
  llvm/test/CodeGen/BPF/CORE/intrinsic-fieldinfo-byte-size-4.ll

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