[PATCH] D56534: [Verifier] Add verification of unaligned atomic load/store

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

> The contract for the atomic library is that it _MUST_ do a lock-free operation on an object on which _any_ compiler in use on the system may have emitted a lock-free operation for.

That's not really relevant.  The question is what happens if, one on thread, I perform a 4-byte operation at address p, and then on another thread, I perform a 4-byte atomic operation on address p+2.

> Can you cite this please?

The C standard bit follows from the strict aliasing rule (6.5p7).  (Yes, it would be nice if it were stated a bit more explicitly in the actual description of atomics, but it's pretty clearly the intent; the description of modification orders for atomic objects doesn't make sense if they could overlap.)


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  https://reviews.llvm.org/D56534/new/

https://reviews.llvm.org/D56534