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Re: [PATCH] x86emul: replace further UB shifts


  • To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Tue, 4 Aug 2020 14:19:51 +0100
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  • Cc: Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Tue, 04 Aug 2020 13:20:05 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 04/08/2020 11:13, Jan Beulich wrote:
> I have no explanation how I managed to overlook these while putting
> together what is now b6a907f8c83d ("x86emul: replace UB shifts").
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

I've just checked, and GCC 9.3.0 does convert this pattern back to a
single shift instruction, so at least we're not left with real mul
instructions.

~Andrew



 


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