dmd 1.053 and 2.037 release

[Don]

Walter Bright wrote:
> Don wrote:
>> I had a further look at this. The compiler *is* creating doubles and 
>> floats as signalling NaNs. Turns out, that there are slight 
>> differences between processors in the way they treat signalling NaNs, 
>> especially between Intel vs AMD. Intel Core2 triggers SNANs when 
>> loading floats & doubles, but *doesn't* trigger for 80-bit SNANs. The 
>> Pentium M that I did most of my testing on, didn't trigger for any of 
>> them. AMD's docs say that it triggers for all of them.
>> Won't be too hard to fix.
> 
> 
> How do we fix the CPU? ;-)

Yeah. Actually the CPU problem is an accepts-invalid bug. It worked on 
my Pentium M, but it shouldn't have.
The problem is what DMD does to the "uninitialized assignments".

float x;

gets changed into

float x = double.snan;

and is implemented with
fld float.snan; fstp x;

The FLD is triggering the snan. They should be changed into mov EAX, 
reinterpret_cast<int>(float.snan); mov x, EAX;

There's another reason for doing this. On Pentium 4, x87 NaNs are 
incredibly slow. More than 250 cycles!!! On AMD and on Pentium 4 SSE2, 
they are the same as any other value (about 0.5 cycles). Yet another 
reason to hate the P4. But still, this is such a horrific performance 
killer that we ought to avoid it.