[LLVMdev] Is shortening a load a bug?

[Quentin Colombet]

On Sep 11, 2014, at 9:10 PM, Reid Kleckner <rnk at google.com> wrote:

> On Thu, Sep 11, 2014 at 5:17 PM, bagel <bagel99 at gmail.com> wrote:
> The phrase "As long as loading an i8 is legal" is the whole point.  What if it isn't?  How do I specify that (should of specifying the load as volatile, which is overkill)?  As an author of a front end, I want to know what the contract is when I say load 32-bits?  When I say load 32-bits I mean load 32-bits.
> 
> I think it's a bug because there is no good way do avoid it and it breaks device drivers.
> 
> This sounds like the *exact* use case for volatile, where the load is observable in some way other than the result that it is used for. If i8 is a legal type for the rest of your ISA, then this should be a volatile load. 


I agree with Reid.
You should use volatile. Loading a i8 is legal in the ISA.

-Quentin
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