Casting double to ulong weirdness

[rumbu via Digitalmars-d]

On Tuesday, 25 August 2015 at 21:30:03 UTC, Warwick wrote:

> The compilers that dont exhibit this problem might set the x87 
> to work at 64 bit at startup or more likely they are using 
> scalar SSE. You cant mix different depth operands in SSE. You 
> cant multiply a float by double for example, you have to 
> convert one of them so they have the same type. So in SSE the 
> bit depth of every op is always explicit.

True word:

This is msvc compiler generated code (default configuration, 
debug):

     double x = 1.2;
012F174E  movsd       xmm0,mmword ptr ds:[12F6B30h]
012F1756  movsd       mmword ptr [x],xmm0
     unsigned long long u = (unsigned long long)(x * 10);
012F175B  movsd       xmm0,mmword ptr [x]
012F1760  mulsd       xmm0,mmword ptr ds:[12F6B40h]
012F1768  call        __dtoul3 (012F102Dh)
012F176D  mov         dword ptr [u],eax
012F1770  mov         dword ptr [ebp-18h],edx