[PATCH] D63525: LangRef: Attempt to formulate some rules for addrspacecast

[Nuno Lopes via Phabricator via llvm-commits]

nlopes added inline comments.


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Comment at: llvm/docs/LangRef.rst:3047
+address spaces are target-specific. Memory access through an invalid,
+non-dereferenceable "null" pointer is undefined behavior in any address
+space. Pointers with the bit-value 0 are only assumed to be
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efriedma wrote:
> Given we don't define what it means for a pointer to be "null", or promise that such a pointer exists in every address-space, it isn't really meaningful to say that dereferencing null is undefined.  We can just drop that whole sentence, I think.
agreed


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Comment at: llvm/docs/LangRef.rst:3049
+space. Pointers with the bit-value 0 are only assumed to be
+non-dereferenceable in address space 0.
+
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unless the function is marked with the `null_pointer_is_valid` attribute


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Comment at: llvm/docs/LangRef.rst:3051
+
+If an object can be proven accessible through a pointer with a
+different address space, the access may be modified to use that
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uhm, do we want this?
This precludes using two address spaces with different memory protections. I understand why this assumption may be useful for optimization, but not sure we want it.


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