[PATCH] D67688: [BPF] Permit all user instructed offset relocatiions

[Yonghong Song via Phabricator via llvm-commits]

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

Currently, not all user specified relocations
(with clang intrinsic __builtin_preserve_access_index())
will turn into relocations.

In the current implementation, a __builtin_preserve_access_index()
chain is turned into relocation only if the result of the clang
intrinsic is used in a function call or a nonzero offset computation
of getelementptr. For all other cases, the relocatiion request
is ignored and the __builtin_preserve_access_index() is turned
into regular getelementptr instructions.
The main reason is to mimic bpf_probe_read() requirement.

But there are other use cases where relocatable offset is
generated but not used for bpf_probe_read(). This patch
relaxed previous constraints when to generate relocations.
Now, all user __builtin_preserve_access_index() will have
relocations generated.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D67688

Files:
  llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
  llvm/test/CodeGen/BPF/CORE/offset-reloc-end-load.ll
  llvm/test/CodeGen/BPF/CORE/offset-reloc-end-ret.ll

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