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[LangRef] Clarify interaction of noalias and synchronization #211507

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nikic merged 1 commit into from
Jul 24, 2026
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[LangRef] Clarify interaction of noalias and synchronization #211507

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6 changes: 6 additions & 0 deletions llvm/docs/LangRef.md
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Expand Up @@ -1522,6 +1522,12 @@ Currently, only the following parameter attributes are defined:
met. For further details, please see the discussion of the NoAlias response
in {ref}`alias analysis <Must, May, or No>`.

`noalias` also applies to accesses from other threads, unless they
happen-before function entry, or function exit happens-before them. This
means that conflicting concurrent accesses from other threads either need
to be based on the noalias pointer, or else be appropriately synchronized
*outside* the function.

Note that this definition of `noalias` is intentionally similar
to the definition of `restrict` in C99 for function arguments.

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