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From: Andreas Schwab <schwab@linux-m68k.org>
References: <20090909120628.J4195@stanley.csl.cornell.edu>
	<20090916195242.GE770@volta.aurel32.net>
	<20090916163826.M50839@stanley.csl.cornell.edu>
Date: Wed, 16 Sep 2009 23:14:17 +0200
In-Reply-To: <20090916163826.M50839@stanley.csl.cornell.edu> (Vince Weaver's
	message of "Wed, 16 Sep 2009 16:45:20 -0400 (EDT)")
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Subject: [Qemu-devel] Re: [PATCH] Fix extlh instruction on Alpha
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To: Vince Weaver <vince@csl.cornell.edu>
Cc: qemu-devel@nongnu.org, Aurelien Jarno <aurelien@aurel32.net>

Vince Weaver <vince@csl.cornell.edu> writes:

> The code is attempting the following:
>
>   tmp1=rb&0x7;
>   tmp1=temp1<<3;
>
>   if (tmp1!=0) {
>      tmp1=64-tmp1;
>      rc=ra<<tmp1;
>   }
>   else {
>      rc=ra;
>   }
>
> The problem with the original code is that in the case of tmp1 being 0,
> the shift left by 64 would result in 0, instead of the identity.
>
> I tried to avoid the jump but couldn't.  Am I missing something?

Instead of tmp1 = 64 - tmp1 use tmp1 = -tmp1 & 0x3f.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
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