[PATCH] D154051: [LangRef] Always allow getelementptr inbounds with zero offset

[Ralf via Phabricator via llvm-commits]

RalfJung added a comment.

For Rust this would be a great change, since we'd like to  allow offset-by-0 for arbitrary pointers in the language and are currently blocked on how to best lower such an operation to LLVM. :)



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Comment at: llvm/docs/LangRef.rst:10931
 *  The base pointer has an *in bounds* address of an allocated object, which
-   means that it points into an allocated object, or to its end. The only
-   *in bounds* address for a null pointer in the default address-space is the
-   null pointer itself.
+   means that it points into an allocated object, or to its end.
 *  If the type of an index is larger than the pointer index type, the
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This might be a good opportunity to clarify that the allocated objects does not have to be live.


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Comment at: llvm/docs/LangRef.rst:10946
 
+Note that ``getelementptr`` with all-zero indices is always considered to be
+``inbounds``, even if the base pointer does not point to an allocated object.
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Are negative indices supported? If yes, is it possible that multiple indices "cancel" to leave the total effective offset as 0 despite there being non-0 indices?


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