Re: RFA fix conversion of little-byte big-word floats to doublest

[Richard Earnshaw <Richard.Earnshaw@buzzard.freeserve.co.uk>]

On Sat, 04 Dec 2004 11:00:54 EST, Daniel Jacobowitz <drow@false.org>  
wrote:
> On Sat, Dec 04, 2004 at 03:46:24PM +0000, Richard Earnshaw wrote:
> > On Sat, 04 Dec 2004 10:44:30 EST, Daniel Jacobowitz <drow@false.org>  
> > wrote:
> > > Could you summarize for me how this is supposed to work?  This means
> > > that get_field treats littlebyte_bigword exactly the same as little.
> > > There's another copy of get_field in libiberty (I don't know why there
> > > are two) which treats it exactly the same as big, instead.  I don't
> > > know how that works either, but it seems the two ought to agree.
> > 
> > The caller has pre-converted the word order into a pure little-endian 
> > format.  See convert_format_to_doublest.
> > 
> > Similar tricks are played on the reverse conversion.
> 
> Huh; it looks like the copy in libiberty is just broken for this case.
> 
> Is the code which does the swapping correct for the 96-bit format?
> It converts ABCD EFGH IJKL to EFGH ABCD IJKL; I would have guessed that
> pure little-endian representation would have been IJKL EFGH ABCD.

I suspect it's completely broken.

> The swap-back code only swaps the first two words also.
> 

It wouldn't surprise me in the least.

> Meanwhile, patch is OK; I'd appreciate it if you could add a comment in
> get_field/put_field somewhere explaining what's going on.

Will do.

R.