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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