RE: [sdcc-devel] commit: Z80 floats / questions on promotion

[Michael H. <mic...@ju...>]

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There are volatiles throughout the fp libraries, pretty much on all of the
args.  Funny thing is that on the z80 _fsadd performs _better_ with the
volatiles there than without.  It's probably something to do with only
having 4 bytes worth of registers available, and probably something to do
with my poor code :)

- -- Michael

On Wed, 7 Nov 2001, Sandeep Dutta wrote:

> These look incorrect to me.. Will take a look.. The first
> version had some problems with alias analysis & it took
> me a while to figure it out .. hence the volatiles...
>
> Sandeep
>
> > -----Original Message-----
> > From: sdc...@li...
> > [mailto:sdc...@li...]On Behalf Of
> > Michael Hope
> > Sent: Wednesday, November 07, 2001 1:25 PM
> > To: sdc...@li...
> > Subject: [sdcc-devel] commit: Z80 floats / questions on promotion
> >
> >
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> > I got bored and added basic support for floats to the z80
> > port.  It seems
> > that the floating pt library routines are quite broken currently.  I
> > mostly fixed fsadd.c, but got a bit confused if I was working
> > around a bug
> > or fixing the code.
> >
> > The interesting ones are:
> >
> > #define SIGNBIT         ((unsigned long)0x80000000)
> >   volatile long sign = 0;
> >
> >      sign = SIGNBIT;
> >
> > This turned into
> >    sign = 0x7FFFFFFF.
> >
> > Seems reasonable.
> >
> >   volatile long mant1;
> >   ...
> >  while (!(mant1 & (unsigned long) 0xE0000000))
> >
> > turns into
> >  while (!(mant1 & 0x7FFFFFFF)
> >
> > Don't know if this should promote or what.
> >
> > #define HIDDEN          (unsigned long)(1 << 23)
> >
> >  mant1 &= ~HIDDEN;
> >
> > turns into
> >  mant1 &= 0x7FFFFFFF;
> >
> > Seems wrong.
> >
> > Also, all the variables are volatile which is a performance hit.  Does
> > anyone know why?  Normally it's to work around a bug when I do it :)
> >
> > - -- Michael
> >
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