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- Subject: Re: LuaJIT performance
- From: Mike Pall <mikelu-0908@...>
- Date: Mon, 10 Aug 2009 02:36:43 +0200
Alexander Gladysh wrote:
> I, personally, am interested in LJ2 for iPhone (which is ARM-based).
> As I intend to reuse existing (x86) game logic code on it, I would
> need floating point support.
Ok, but you may be in for a nasty surprise: the 3GS has an ARM
Cortex-A8 CPU which only has VFPlite. This is actually a step back
from the previous models which had an ARM 1176JZ(F)-S with a full
VFP unit. And since the vector mode of VFP is officially deprecated,
you're in for more surprises in the future.
Not to squash your hopes, but I suggest you try to measure whether
the iPhone FP performance can keep up with your requirements.
Maybe try some simple double-precision FP benchmarks in C (don't
compile as Thumb code or you get softfp).
Timm S. Mueller wrote:
> Just for the record: a port of LuaJIT to ARM would be very welcome, and
> I'd be perfectly happy with a 32 bit numerical datatype on this
Umm, so one probably needs at least two different VMs for ARM (FP
vs. int-only). Then combine this with the options for ARM vs.
Thumb vs. Thumb2 code and with ARMv4-ARMv7 support and soon we'll
have an exponential number of targets to support ... *sigh*
Thank you to both of you for the quick feedback!