From: Andreas Schwab <schwab@linux-m68k.org>
To: Vince Weaver <vince@csl.cornell.edu>
Cc: qemu-devel@nongnu.org, Aurelien Jarno <aurelien@aurel32.net>
Subject: [Qemu-devel] Re: [PATCH] Fix extlh instruction on Alpha
Date: Wed, 16 Sep 2009 23:14:17 +0200 [thread overview]
Message-ID: <m2tyz2iod2.fsf@igel.home> (raw)
In-Reply-To: <20090916163826.M50839@stanley.csl.cornell.edu> (Vince Weaver's message of "Wed, 16 Sep 2009 16:45:20 -0400 (EDT)")
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
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
prev parent reply other threads:[~2009-09-16 21:14 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-09 16:08 [Qemu-devel] [PATCH] Fix extlh instruction on Alpha Vince Weaver
2009-09-16 19:52 ` Aurelien Jarno
2009-09-16 20:45 ` Vince Weaver
2009-09-16 20:56 ` Aurelien Jarno
2009-09-17 16:07 ` Vince Weaver
2009-09-17 16:25 ` Laurent Desnogues
2009-09-17 16:35 ` [Qemu-devel] " Andreas Schwab
2009-09-17 17:19 ` [Qemu-devel] " Aurelien Jarno
2009-09-16 21:14 ` Andreas Schwab [this message]
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