[PATCH] D82316: [LangRef] Add `frozen` attribute to documentation

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert added a comment.

Thanks for splitting this off!

I'm still in favor of `nopoison` as a name but so far no one else supports that name it seems. At least I would prefer that name if this means "not poison or instant UB".
Now, the documentation talks about undefined bits, which is something different. Maybe frozen makes sense after all.

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As mentioned by @nikic, we should not talk about ABI, frontends, backends, etc. in the lang ref if not strictly necessary. I think describing the attribute as the absence of undefined or poison bits in the value representation is what we want :)



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Comment at: llvm/docs/LangRef.rst:3666
+-  Arguments and return values of function calls, when those operands
+   are marked with the ``frozen`` attribute.
 
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Can we make this two bullet points. 
Return values are not really operands so maybe: "The operand of a return instruction if the function or invoking call site has a ``frozen`` attribute in the return value position".
I would also not talk about Arguments here as we describe instructions. So maybe say "The operand of a :ref:`call <i_call>` or :ref:`invoke <i_invoke>` instruction for which the call site has a ``frozen`` attribute at the respective position."


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