Possible bug in atomicOp

[Don]

Robert Jacques wrote:
> On Sat, 23 Oct 2010 15:50:30 -0400, Sean Kelly <sean at invisibleduck.org> 
> wrote:
>>>>
>>>> Basically, atomicLoad (which atomicOp uses) always returns in ALU
>>> > registers.
>>>> Floating point numbers need to be returned in floating point
>>> > registers.
>>>> Therefore, a NaN always gets returned from atomicLoad!double, and a
>>> > NaN isn't
>>>> equal to anything.
>>>
>>> So shouldn't there be a static assert to prevent one from using
>>> atomicOp with floats and doubles? Or should atomicLoad be implemented
>>> to support floats and doubles?
>>
>> The former in the short term and the latter in the long term.
> 
> Well, here's the assembler to load a value onto the FP stack:
> float  __int2float  (ref int  x) { asm { fld float  ptr [EAX]; } }
> double __long2double(ref long x) { asm { fld double ptr [EAX]; } }

That should be:
fild dword ptr [EAX];
fild qword ptr [EAX];

> Unfortunately, direct loading from a register doesn't seem to be 
> supported. So writing wrapper code which uses a union would be almost as 
> fast. I know there is an SSE instruction to load directly from 
> registers, but we can't assume SSE support.