On 13 November 2017 at 15:28, Christopher Li <sparse@xxxxxxxxxxx> wrote: > Currently value pseudo does not have size. > This create a problem pointed out by Dibyendu. > When using LLVM, calling varidic function with > constant value, there is no where to find the > size. > > Linus give out two suggestions. One is give pseudo > a size. The other one is the push instruction. > This is the implementation of the first suggestion. > > The model is actual very simple. The pseudo is > exactly as before if you are not looking at the size. > There is a size at create time, which tag alone with > it. > Chris, I think the discussion of this topic should be moved to this thread. I found a problem with this as I mentioned in the other thread. Last year a change was introduced to initialize aggregate structures in Sparse using a store instruction that uses a PSEUDO_VAL. However when this creates a pseudo the size is set to the size of the aggregate types - and this size (> 64 bits) is kind of nonsensical for a PSEUDO_VAL. I suggested that when creating a PSEUDO_VAL we should only create distinct values when size is register size - i.e. one of 8, 16, 32, or 64. Else we should set size to 0. Couple of more points: a) We should also set size to 0 when we create a PSEUDO_VAL in CSE for uninitialized vars. b) We should ideally avoid CSE on PSEUDO_VAL with size = 0 because I don't think it makes sense to do so - i.e. they either represent uninitialized vars or aggregates > 64 bits. The above aggregate initialization change is one of the changes I did not merge into my project as I wasn't happy with it. I still think this change is not correct and needs to be removed or redone. I am not 100% sure but presumably creating PSEUDO_VAL where the instruction size is > 64-bits means that these PSEUDO_VAL values might be considered 'same as' any other PSEUDO_VAL with value 0. Thanks and Regards Dibyendu -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
