On Sun, Aug 06, 2017 at 07:34:50PM -0400, Christopher Li wrote: > >> Yes, you keep on arguing this is the result of uninitialized variable. > >> Nothing to worry about. > > > > You asked a question about the *current* behaviour of sparse > > and I explained the reason of this behaviour. > > I ask the question weather this SSA form is legal (in the sense > that preserving SSA property if you want to be more specific.) > > You are saying you did not answer my question directly. You did not > pass judgement on weather this thing is legal or not. You just say why > it was done this way. Because answering this question with an 'yes' or a 'no' is pointless. Imagine that some authority on compiler would have answered to you 'yes' I consider that as legal because this or that. Would it have helped you? I don't think so. Same with 'no'. > > It's not because explain this that I'm also saying > > "that is the correct behaviour and nothing must be changed about". > > > > And you know that I don't think so because we already talked about it. > > And I already said you that I have code that redo the SSA construction > > and that this code doesn't have the issues with undef vars because > > I used a special value for them. > > That is what I want to find out, if your new SSA form have the similar > problem violating the SSA property or not. It would have been easier to simply ask it. > >> Then how to fix it is just technical details. > >> I care less about warning uninitialized variable warning, which > >> we can't do a perfect job any way. I am more worry about those > >> screw up SSA forms. > > > > It's where we disagree. > > You're talking about this SSA thing as if you're busy writing a > > compiler but currently and since its creation sparse is a > > *semantic checker* used in *complement* of a real compiler > > to give warnings that the compiler doesn't bother with. > > Please don't mix the raising warning thing as if do proper SSA > hinder you raise warning about uninitialized value. Have I said that or even suggest it? > It is actually > the reverse, do proper SSA will help you find out using uninitialized > value better. > > But as I said, we can't get the warning perfect right due to nature > of the problem. Yes, it's pretty well known about uninitialized vars. > > My opinion is that it is *very* valuable to given the best possible > > warnings and yes it sucks that so many things relative to > > compiler technology are undecidable or NP-hard & friends. > > But this only means that it is impossible to do a *perfect* job, > > not that it is impossible to do a *good* job. > > No disagreement here. Warning and proper SSA form is two different > thing. Good. > You told me about the placement of phi node. I look it up. Yes > it is a big problem. But that "usage before define" and violating the > SSA dominance property you never told me about. I certainly not said something like "usage before define" since it's just a symptom. I told you about solving problmes with the handling of undefined vars. > You does not seem to > understand what property SSA should have in the first few response > to my email, questioning how to define "illegal SSA". That is my > impression, I can be wrong. Your impression is very wrong. Otherwise I wouldn't have bothered to write code to redo the SSA construction thing and told you that there is a lot of problems with the current SSA. > >> Now that RC5 is almost out of the door. It is my intention to start this > >> discussion to clarify things and point out things I believe is wrong. > >> I know it is going to be a controversial topic :-) > > > > I have a feeling that the 150+ patches that are pending since > > January-March will have to wait even more. > > Same for a series that is waiting since more than 2 years now. > > Am I wrong? > > No, and sorry about that. I was too busy at that time. But now I have > allocate some time for sparse. Let's do the review process again > after the release. OK good to hear that. I insist very heavily that I would like those to be handled *before* moving further witht the SSA thing. Especially for Nicolai's series which is waiting since a scandalous amount of time. -- Luc -- 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
