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Re: [PATCH] x86/ioapic: Improve code generation for __io_apic_{read,write}()

To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
From: Jan Beulich <jbeulich@xxxxxxxx>
Date: Wed, 5 Aug 2020 17:10:28 +0200
Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
Delivery-date: Wed, 05 Aug 2020 15:10:36 +0000
List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 05.08.2020 15:54, Andrew Cooper wrote:
> The write into REGSEL prevents the optimiser from reusing the address
> calculation, forcing it to be calcualted twice.
> 
> The calculation itself is quite expensive.  Pull it out into a local varaible.
> 
> Bloat-o-meter reports:
>   add/remove: 0/0 grow/shrink: 0/26 up/down: 0/-1527 (-1527)
> 
> Also correct the register type, which is uint32_t, not int.
> 
> No functional change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

References:
- [PATCH] x86/ioapic: Improve code generation for __io_apic_{read, write}()
  - From: Andrew Cooper

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