[fpc-devel] 64 Bit / 32 Bit

[Jonas Maebe]

On 04 Oct 2007, at 13:00, Daniël Mantione wrote:

>> I don't think it would be a good idea to map the extended type to  
>> 80 bit soft
>> float on platforms that don't support 80 bit fpu calculations in  
>> hardware.
>> Many programs use "extended" by default without actually requiring  
>> 80 bit
>> precision, and mapping those all to soft float would needlessly  
>> slow down such
>> programs.
>>
>> I think a separate type would be more appropriate.
>
> Hmmm... I prefer to keep correct code that writes say, an extended  
> type to
> a file working,

It won't keep it working but rather break it, since currently writing  
an extended to file on virtually all platforms writes a double to the  
file.

> over keeping code that falsely uses extended precision
> fast, especially as I expect people to correct such code anyway to  
> take
> advantage of SSE performance.

I don't expect that to happen in most situations.

> In such case "extended" would also be a misleading name, since it  
> would
> get "long double" semantics. Even worse, it would be a TP compatible
> extended on i386 and some x86_64 platforms and long double on other
> platforms.

It's probably better to directly introduce a longdouble type with  
longdouble (128 bit) semantics on all platforms. I don't think that  
emulating the almost nowhere supported 80 bit type does much good.


Jonas