On Fri, Jul 13, 2018 at 11:40 AM, Steve Fink <sf...@mozilla.com> wrote:
> On 07/12/2018 04:27 PM, Cameron McCormack wrote: > >> On Fri, Jul 13, 2018, at 6:51 AM, Kris Maglione wrote: >> >>> I actually have a patch sitting around with helpers to make it super >>> easy to >>> use smart pointers as tagged pointers :) I never wound up putting it up >>> for >>> review, since my original use case went away, but it you can think of any >>> specific cases where it would be useful, I'd be happy to try and get it >>> landed. >>> >> Speaking of tagged pointers, I've used lower one or two bits for tagging >> a number of times, but I've never tried packing things into the high bits >> of a 64 bit pointer. Is that inadvisable for any reason? How many bits >> can I use, given the 64 bit platforms we need to support? >> > > JS::Value makes use of this. We preserve the bottom 47 bits, but that's > starting to be problematic as some systems want 48. So, stashing stuff into > the high 16 bits is pretty safe! > 57-bit address space support is coming for x86-64. Rob -- Su ot deraeppa sah dna Rehtaf eht htiw saw hcihw, efil lanrete eht uoy ot mialcorp ew dna, ti ot yfitset dna ti nees evah ew; deraeppa efil eht. Efil fo Drow eht gninrecnoc mialcorp ew siht - dehcuot evah sdnah ruo dna ta dekool evah ew hcihw, seye ruo htiw nees evah ew hcihw, draeh evah ew hcihw, gninnigeb eht morf saw hcihw taht. _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
