Date   : Mon, 15 Aug 1994 19:36:35 +0100 (BST)
From   : clr1@...
Subject: Re: Flags and BIT

On Mon, 15 Aug 1994, Stephen Quan wrote:
> Just wanted to clarify.  If you are implementing SBC using SBB and
> the IBM's processor flags, you can do
> 
>     XOR   AH,01
>     LAHF
>     SBB   ...
>     SAHF
>     XOR   AH,01
> 
> I am not sure the order of LAHF and SAHF, but you get the general
> idea!

Just in case someone's thinking of implementing this, lahf and sahf *are* 
in the wrong order. Also, do you have to restore C to what it was before? 
According to the AUG (as far as I can see) it is set to 0 if there was a 
SBC and 1 if there wasn't, meaning that the altered carry is okay to 
keep. Correct me if I'm wrong, though.

+-------------------+-------------------------------------------------+
| /-- |_| /-- | (~  | "And the driving is like the driving of Jehu,   |
| \-- | | |   | _)  | the son of Nimshi, for he drives furiously."    |
+-------------------+-------------------- Second Book of Kings 9 v20 -+