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Re: bitrotate

From: Paolo Bonzini
Subject: Re: bitrotate
Date: Mon, 01 Sep 2008 09:43:01 +0200
User-agent: Thunderbird (Macintosh/20080707)

> I suspect the rotation part is the sarl+sall and or.  Either we could
> experiment with changing the code, or we could try to make gcc detect
> that this code actually is a rotate...  Possibly gcc already does that
> right thing, with today's CPU architectures it can be difficult to know
> which ops are the most efficient choice.

I don't know, GCC already has plenty of rotate-detection code.  It might
be that for 16-bit it does not like to give a rotate to your machine.
Usually, trying with -mtune=i386 is a way to see if it has taken its
decision based on the hardware.


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