Setting the FPU control word?

[Don Clugston]

Bill Baxter wrote:
> Jarrett Billingsley wrote:
>> "Bill Baxter" <dnewsgroup at billbaxter.com> wrote in message 
>> news:fr3k2f$30b5$1 at digitalmars.com...
>>> Anyone know how to translate these instructions to D? (specifically 
>>> DMD/Win flavor of D, but GDC/Win also appreciated if different):
>>>
>>>    http://www.cs.cmu.edu/~quake/robust.pc.html
>>>
>>> --bb
>>
>> Would std.c.fenv (or tango.stdc.fenv, same module) be of any use here? 
> 
> Ah, fsetprec(FE_DOUBLE) does indeed seem to be intended to be the thing.
> 
> Except, it doesn't work.  The asm fldcw thing does seem to work though.
> 
> 
> ----
> module fpctrl;
> import std.c.fenv;
> import std.stdio;
> 
> enum FPPrecision : short
> {
>     Single = 0x0000,
>     Double = 0x0200,
>     Real = 0x0300,
>     Mask = 0x0300,
> }
> 
> void setFPControlWord(FPPrecision precision)
> {
>     FPPrecision oldcw;
> 
>     asm
>     {
>         fstcw oldcw;
>         fwait;
>         fldcw precision;
>     }
>     writefln("oldcw was: 0x%x", oldcw);
> 
> 
> }
> 
> void main()
> {
>     fesetround(FE_FLTPREC); // should set ctrl word to 0x_2__
> 
>     setFPControlWord(FPPrecision.Double); // prints 0x_3__, the default
> }
> 
> 
> --bb

I've got something similar in tango.math.IEEE.

reduceRealPrecision()
setIeeeRounding()
ieeeFlags();

Mostly only works for x86 (no inline asm yet for other CPUs?)