[LLVMdev] Aliasing of volatile and non-volatile

[Krzysztof Parzyszek]

On 9/4/2013 4:48 PM, Eli Friedman wrote:
>
> Accessing a variable declared as "volatile int" through a non-volatile
> pointer isn't allowed.  Accessing a variable declared as non-volatile
> "int" through a volatile pointer is allowed.

Ok, that's not a problem.  The problem here is the invariance of the 
non-volatile load.  In the alias set tracker, the alias set that 
contains a volatile load is marked as "mod/ref".  This then implies that 
any other load (volatile or not) from that set is not invariant in a 
given region.  For that "variance" to happen that load would have to be 
accessing volatile memory, which isn't legal for non-volatile loads.

-K


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