wish: optimize (x > 0.) floating point comparison.

Andreas Schwab schwab@issan.informatik.uni-dortmund.de
Mon Sep 28 03:19:00 GMT 1998


"Charles M. Hannum" <root@ihack.net> writes:

|> > On Sat, Sep 26, 1998 at 10:03:54AM -0400, Charles M. Hannum wrote:
|> > > Don't let the 96-bit length fool you.  It's really the same format,
|> > > but with 16 bits wasted (for alignment purposes, I assume).
|> > 
|> > No it isn't the same, as the representable precision is different.
|> > For example, LDBL_MIN:
|> > 
|> >         i386    3.36210314311209350626e-4932
|> >         m68k    1.68105157155604675313e-4932
|> 
|> I hate to drag this out, but unfortunately your include files are
|> wrong.

No, in this point he is right.

|> Unlike the single- and double-precision formats, the
|> extended-precision format includes the leading 1 digit explicitly in
|> the mantissa.  This is the same on both i386 and m68k.

But the Intel and Motorola formats differ in the interpretation of the
minimum exponent for denormalized numbers.  Other than that the formats
are identical apart from byte-order.

|> See section 1.5.2 of the `M68000 Family Programmer's Reference
|> Manual'.

Note that none of the m680x0 manuals get the value for LDBL_MIN right, the
68060 manual is closest, but still wrong.

Andreas.

-- 
Andreas Schwab                                      "And now for something
schwab@issan.informatik.uni-dortmund.de              completely different"
schwab@gnu.org



More information about the Gcc mailing list