Sean Kelly wrote:
On Apr 16, 2011, at 1:02 PM, Robert Jacques wrote:
On Sat, 16 Apr 2011 15:32:12 -0400, Walter Bright <newshou...@digitalmars.com>
wrote:
The dmd startup code (actually the C startup code) does an fninit. I never
thought about new thread starts. So, yeah, druntime should do an fninit on
thread creation.
The documentation I've found on fninit seems to indicate it defaults to 64-bit
precision, which means that by default we aren't seeing the benefit of D's
reals. I'd much prefer 80-bit precision by default.
There is no option to set "80-bit precision" via the FPU control word.
??? Yes there is.
enum PrecisionControl : short {
PRECISION80 = 0x300,
PRECISION64 = 0x200,
PRECISION32 = 0x000
};
/** Set the number of bits of precision used by 'real'.
*
* Returns: the old precision.
* This is not supported on all platforms.
*/
PrecisionControl reduceRealPrecision(PrecisionControl prec) {
version(D_InlineAsm_X86) {
short cont;
asm {
fstcw cont;
mov CX, cont;
mov AX, cont;
and EAX, 0x0300; // Form the return value
and CX, 0xFCFF;
or CX, prec;
mov cont, CX;
fldcw cont;
}
} else {
assert(0, "Not yet supported");
}
}
