Re: LuaJIT performance query

[Mike Pall <mikelu-0806@...>]

Stefan Sandberg wrote:
> Speaking of ver. 2, what's the status, if any, on 64 bit support?

I need to finish the x86 port first. I already have an x64-capable
CPU. But this doesn't mean it's the logical choice for the 2nd port.

First you need to realize that x64 code does not run faster than
x86 code in most cases: 64 bit integer ops are rare, a couple more
registers are nice, but the slight speed gain often doesn't
outweigh the additional memory bandwidth used for wider pointers.

The larger virtual memory space cannot be reasonably used by Lua
itself, since the current GC won't be able to handle several
gigabytes worth of small objects, anyway. Since all x64 OS can
easily run x86 binaries with no speed loss, the only valid reason
for wanting an x64 port of LuaJIT would be to link it to a pure
x64 binary.

I do not see this as a pressing use case right now. An ARM port
would be more important IMHO. But I suggest to postpone this
discussion after the release of the x86 port.

--Mike