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- Subject: Re: Lua number type and 64-bit machines
- From: Florian Weimer <fw@...>
- Date: Sun, 08 Mar 2009 11:38:59 +0100
* Thomas Harning, Jr.:
> On Fri, Mar 6, 2009 at 7:02 AM, Luiz Henrique de Figueiredo
> <lhf@tecgraf.puc-rio.br> wrote:
>>> Lua uses doubles on 32bit machines, shouldn't 64bit machines use long
>>> doubles or even quadruple precision floats ?
>>
>> Do 64-bit machines suppport long doubles in hardware?
>
> The x86_64 architecture does not support long doubles in hardware.
But not with SSE2, you have to fallback to x87 FP, which results in a
performance hit.
What's worse, sizeof(long double) is 16 for alignment reasons, which
pushes the conceptual word size to 32 bytes.
