Hi! Ping.
On Mon, 29 Apr 2013 10:16:52 +0200, I wrote:
> Ping.
>
> On Mon, 22 Apr 2013 11:52:23 +0200, I wrote:
> > On Fri, 5 Apr 2013 23:55:37 +0100, "Maciej W. Rozycki"
> > <ma...@codesourcery.com> wrote:
> > > On Fri, 5 Apr 2013, Thomas Schwinge wrote:
> > > > > Index: gcc/config/fp-bit.c
> > > > > ===================================================================
> > > > > RCS file: /cvs/uberbaum/gcc/config/fp-bit.c,v
> > > > > retrieving revision 1.39
> > > > > diff -u -p -r1.39 fp-bit.c
> > > > > --- gcc/config/fp-bit.c 26 Jan 2003 10:06:57 -0000 1.39
> > > > > +++ gcc/config/fp-bit.c 1 Apr 2003 21:35:00 -0000
> > > > > @@ -210,7 +210,11 @@ pack_d ( fp_number_type * src)
> > > > > exp = EXPMAX;
> > > > > if (src->class == CLASS_QNAN || 1)
> > > > > {
> > > > > +#ifdef QUIET_NAN_NEGATED
> > > > > + fraction |= QUIET_NAN - 1;
> > > > > +#else
> > > > > fraction |= QUIET_NAN;
> > > > > +#endif
> >
> > > I think the intent of this code is to preserve a NaN's payload (it
> > > certainly does for non-QUIET_NAN_NEGATED targets)
> >
> > I agree. For preserving the payload, both the unpack/pack code also has
> > to shift by NGARDS.
> >
> > > Complementing the change above I think it will also make
> > > sense to clear the qNaN bit when extracting a payload from fraction in
> > > unpack_d as the class of a NaN being handled is stored separately.
> >
> > I agree.
> >
> > > Also I find the "|| 1" clause in the condition immediately above the
> > > pack_d piece concerned suspicious -- why is a qNaN returned for sNaN
> > > input? Likewise why are __thenan_sf, etc. encoded as sNaNs rather than
> > > qNaNs? Does anybody know?
> >
> > I also stumbled over that, but for all these, I suppose the idea is that
> > when a sNaN is "arithmetically processed" (which includes datatype
> > conversion), an INVALID exception is to be raised (though, »[fp-bit]
> > implements IEEE 754 format arithmetic, but does not provide a mechanism
> > [...] for generating or handling exceptions«), and then converted into a
> > qNaN.
> >
> > Also, I found that the bit to look at for distinguishing qNaN/sNaN is
> > defined wrongly for float. Giving me some "interesting" test results...
> > ;-)
> >
> > Manual testing looks good. Automated testing is still running; in case
> > nothing turns up, is this OK to check in?
> >
> > libgcc/
> > * fp-bit.c (unpack_d, pack_d): Properly preserve and restore a
> > NaN's payload.
> > * fp-bit.h [FLOAT] (QUIET_NAN): Correct value.
> >
> > Index: libgcc/fp-bit.c
> > ===================================================================
> > --- libgcc/fp-bit.c (revision 402061)
> > +++ libgcc/fp-bit.c (working copy)
> > @@ -214,11 +214,18 @@ pack_d (const fp_number_type *src)
> > else if (isnan (src))
> > {
> > exp = EXPMAX;
> > + /* Restore the NaN's payload. */
> > + fraction >>= NGARDS;
> > + fraction &= QUIET_NAN - 1;
> > if (src->class == CLASS_QNAN || 1)
> > {
> > #ifdef QUIET_NAN_NEGATED
> > - fraction |= QUIET_NAN - 1;
> > + /* The quiet/signaling bit remains unset. */
> > + /* Make sure the fraction has a non-zero value. */
> > + if (fraction == 0)
> > + fraction |= QUIET_NAN - 1;
> > #else
> > + /* Set the quiet/signaling bit. */
> > fraction |= QUIET_NAN;
> > #endif
> > }
> > @@ -574,8 +581,10 @@ unpack_d (FLO_union_type * src, fp_number_type * d
> > {
> > dst->class = CLASS_SNAN;
> > }
> > - /* Keep the fraction part as the nan number */
> > - dst->fraction.ll = fraction;
> > + /* Now that we know which kind of NaN we got, discard the
> > + quiet/signaling bit, but do preserve the NaN payload. */
> > + fraction &= ~QUIET_NAN;
> > + dst->fraction.ll = fraction << NGARDS;
> > }
> > }
> > else
> > Index: libgcc/fp-bit.h
> > ===================================================================
> > --- libgcc/fp-bit.h (revision 402061)
> > +++ libgcc/fp-bit.h (working copy)
> > @@ -190,7 +190,7 @@ typedef unsigned int UTItype __attribute__ ((mode
> > # define EXPBIAS 127
> > # define FRACBITS 23
> > # define EXPMAX (0xff)
> > -# define QUIET_NAN 0x100000L
> > +# define QUIET_NAN 0x400000L
> > # define FRAC_NBITS 32
> > # define FRACHIGH 0x80000000L
> > # define FRACHIGH2 0xc0000000L
> > @@ -298,7 +298,7 @@ typedef unsigned int UTItype __attribute__ ((mode
> > /* numeric parameters */
> > /* F_D_BITOFF is the number of bits offset between the MSB of the mantissa
> > of a float and of a double. Assumes there are only two float types.
> > - (double::FRAC_BITS+double::NGARDS-(float::FRAC_BITS-float::NGARDS))
> > + (double::FRAC_BITS+double::NGARDS-(float::FRAC_BITS+float::NGARDS))
> > */
> > #define F_D_BITOFF (52+8-(23+7))
> >
Grüße,
Thomas
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