On Tue, Jun 17, 2014 at 09:36:09PM +1000, Manu via Digitalmars-d wrote: > On 17 June 2014 18:18, Walter Bright via Digitalmars-d > <digitalmars-d@puremagic.com> wrote: > > On 6/16/2014 10:02 PM, Manu via Digitalmars-d wrote: > > > >> I can't imagine exceptions would appear in hot code very > >> often/ever? > > > > > > I've tried to explain this to you for months. You don't believe my > > explanations, we just go round in circles. I strongly suggest you > > write some code with shared_ptr<T> and try it out. Disassemble the > > result. Benchmark it. Use Microsoft C++, so I won't be sabotaging > > your results and it won't be because I write crappy compilers :-) > > ARC is useless without compiler support. If we can't experiment with > the compiler's ability to eliminate redundant RC related work, then we > aren't 'experimenting' with anything of interest. > We agree ARC isn't acceptable without compiler support. That's never > been on debate. > I have no way of testing whether the compiler is able to produce > acceptable results in C or D today. shared_ptr will demonstrate what > we already know is not acceptable, not whether the results of compiler > support for RC optimisation is satisfactory. > > I believe your explanations, but that's not where I'm hung up. In most > cases I can visualise, there is significant opportunity for the > compiler to eliminate redundant work, and in the remaining cases, I > can imagine numerous very simple approaches to remove the bumps from > hot code without interfering very much at all. [...]
Perhaps the way to convince Walter, is to fork dmd on github, check it out, and implement ARC in your fork (to whatever extent is necessary for a first, possibly very crude, demonstration)? It doesn't have to work 100%, it doesn't even have to pass the test suite or compile the full D language, it just has to do enough to prove that the compiler is capable of automatically making performance-critical ARC optimizations on whatever benchmark you choose to use. This would add a lot of substance to all the hot air we've been pumping at each other every time a GC/ARC-related thread comes up. T -- If it's green, it's biology, If it stinks, it's chemistry, If it has numbers it's math, If it doesn't work, it's technology.
