This is the mail archive of the binutils@sourceware.org mailing list for the binutils project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [patch] ARM vclt broken


On Thu, Jan 04, 2007 at 04:05:36AM +0000, Nick Clifton wrote:
> Hi Paul,
> 
> >The ARM NEON vclt and vcle instructions are aliases for vcgt and vcge 
> >respectively.
> 
> Err, isn't that the other way around ?  Ie vclt is an alias for vcge and 
> vcle is an alias for vcgt ?

Nope - in fact that's how everyone seems to get these particular
instructions wrong.  "a < b" is "!(a >= b)", but there's an extra
negation, so you can't use the same instruction for both.  However
"a < b" is "b > a", so by swapping operands, you can use the same
instruction.

If I'm remembering Paul's explanation correctly, then binutils
currently has this reversed and tries to encode "a > b" as "b <= a".

-- 
Daniel Jacobowitz
CodeSourcery


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]