[PATCH] D94002: [LangRef] Make lifetime intrinsic's semantics consistent with StackColoring's comment

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune updated this revision to Diff 325805.
aqjune added a comment.

I updated the text to reflect the consensus made in llvm-dev discussion so far.

If lifetime.start/end isn't used with a stack pointer with zero offset, it is equivalent to memset(poison).
Also, the paragraph that describes the disjointness of addresses is removed.

Calling lifetime.start twice on an alive alloca is also updated to memset(poison).
It isn't defined as UB because I couldn't find any LLVM code or comments saying that lifetime may raise UB.
Another choice is to define it as no-op, but https://godbolt.org/z/TqoeqG requires it.

Memory accesses on a dead object should be UB because the comment at StackColoring.cpp specifies that.

I did not mention anything about the size argument of lifetime.start/end because it wasn't clear to me how the argument was used.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D94002/new/

https://reviews.llvm.org/D94002

Files:
  llvm/docs/LangRef.rst

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