Re: Re: [RFC] Union Types v2

> > I think this performance impact is a real concern; PHP is the only language > I know of which implements type checks entirely at run-time in production > code, and we should ask ourselves if that's definitely the right approach.. Would it be possible, at least in principle, to build a static analysis > tool which could prove that certain type checks would never fail, and prime > OpCache with code that leaves them out? As I understand it, this is how > Dart works: the compiler only emits run-time checks for assertions it can't > prove true by static analysis. I was wondering the same thing, especially in the light of preloading, where a lot of class/function definitions are known on startup. For example, doing: function x(): int {} function y(int $foo) {} y(x()); Should definitely not redundantly check the type of the y() parameter, if possible. Also, in the case of JIT, shouldn't type hints actually *improve* performance? — Benjamin On Thu, 24 Oct 2019 at 14:47, Rowan Tommins <rowan.collins@gmail.com> wrote: > Hi Dmitry, > > On Wed, 23 Oct 2019 at 16:43, Dmitry Stogov <dmitry@zend.com> wrote: > > > Actually, I think PHP already took wrong direction implementing "typed > > references" and "type variance". > > Introducing more "typing", we suggest using it, but this "typing" > > comes > > with a huge cost of run-time checks. > > From 10% (scalar type hint of argument) to 3 times (typed reference > > assignment) performance degradation. > > Anyone may rerun my benchmarks > > > > https://gist.github.com/dstogov/fb32023e8dd55e58312ae0e5029556a9 > > > > > I think this performance impact is a real concern; PHP is the only language > I know of which implements type checks entirely at run-time in production > code, and we should ask ourselves if that's definitely the right approach.. > > Would it be possible, at least in principle, to build a static analysis > tool which could prove that certain type checks would never fail, and prime > OpCache with code that leaves them out? As I understand it, this is how > Dart works: the compiler only emits run-time checks for assertions it can't > prove true by static analysis. > > The simpler idea I had in this area was caching what type checks a value > had passed, either on each zval or perhaps just at the class level, so that > checking the same type again would be much faster, even if it was a complex > union with multiple interfaces. > > Regards, > -- > Rowan Tommins > [IMSoP] >