std.math performance (SSE vs. real)

Iain Buclaw via Digitalmars-d digitalmars-d at puremagic.com
Thu Jul 3 07:26:36 PDT 2014


On 3 July 2014 14:51, Joseph Rushton Wakeling via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On Thursday, 3 July 2014 at 11:21:34 UTC, Iain Buclaw via Digitalmars-d
> wrote:
>>
>> The spec should be clearer on that.  The language should respect the long
>> double ABI of the platform it is targeting
>> - so if the compiler is targeting a real=96bit system, but
>> the max supported on the  chip is 128bit, the compiler should
>> *still* map real to the 96bit long doubles, unless explicitly
>> told otherwise on the command-line.
>
>
> This would be a change in the standard, no?  "The long double ABI of the
> target platform" is not necessarily the same as the current definition of
> real as the largest hardware-supported floating-point type.
>
> I can't help but feel that this is another case where the definition of real
> in the D spec, and its practical use in the implementation, have wound up in
> conflict because of assumptions made relative to x86, where it's simply a
> nice coincidence that the largets hardware-supported FP and the long double
> type happen to be the same.

It's also a handy coincidence that for many platforms the targets
largest supported FP and *double* type happen to be the same too.


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