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
