On Sun, Aug 6, 2017 at 8:31 PM, Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx> wrote: >> 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 is not pointless if sparse don't produce the "usage before define" code. > >> > 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. I did in another email. >> 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. OK. I don't know what is the detail of handle undefined vars from you description. > >> 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. All good then. >> >> 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. No problem. One at a time. Chris -- 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
