Re: [PATCH] x86: always_inline wrapper for x86's test_bit

[Andi Kleen]

> I have googled, but the only problem I found was concerning dead code 

It might come as a surprise, but google is still not omniscient.

> elimination, and in particular references to unavailable object from
> code that was expected to be discarded. The worst that can happen in 
> this case is that gcc might produce a strange construction where a
> runtime check will choose between the two alternative implementations of
> test_bit. Another is that it will select the 'wrong' implementation. 
> Both will result is some code-bloat, but at least the code should work
> properly.

Yes, but extreme code bloat can be fatal.

> I have not checked with 3.2. The oldest compiler I have available here
> is 3.3. That version compiles the functions as expected: I have found
> instances of either type in the objdump and I have not found strange
> constructions with both types there.

It would be good to check on 3.2 too to avoid potential nasty surprises.

> If you were thinking of another/bigger problem with gcc-3.2, could you 
> please give me a pointer?

Not sure what you mean here.

-Andi
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/