confused by code in setup.S

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This is my first post to this list, so please be gentle. :-)

I'm studying the memory-sizing code (aka E820) in setup.S of 2.3.99-pre6,
because I think I may need to modify it for our purposes. I found something odd
on line 306:

movw %di, %ax
addw $20,%ax
movw %ax,%di

I don't understand why it isn't just:

addw $20,%di

%ax is always overwritten after these three instructions, so it's not like the
code needs to set both %ax and %di. And even if it were, this code:

addw $20,%di
movw %di, %ax

would be more efficient.

--
Timur Tabi - ttabi@interactivesi.com
Interactive Silicon - http://www.interactivesi.com
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