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Date: Wed, 04 Jul 2012 10:04:59 +0300
From: Orit Wasserman <owasserm@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v14 04/13] Add cache handling functions
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To: Eric Blake <eblake@redhat.com>
Cc: peter.maydell@linaro.org, aliguori@us.ibm.com, quintela@redhat.com, stefanha@gmail.com, qemu-devel@nongnu.org, mdroth@linux.vnet.ibm.com, Blue Swirl <blauwirbel@gmail.com>, Petter Svard <petters@cs.umu.se>, Benoit Hudzia <benoit.hudzia@sap.com>, avi@redhat.com, Aidan Shribman <aidan.shribman@sap.com>, pbonzini@redhat.com, chegu_vinod@hp.com

On 07/03/2012 10:49 PM, Eric Blake wrote:
> On 07/03/2012 01:23 PM, Blue Swirl wrote:
> 
>>> +
>>> +static inline int64_t round2pow2(int64_t value)
> 
> round up or down?
> 
>>> +{
>>> +    while (!is_power_of_2(value)) {
>>> +        value &=  ~(1 << (ffs(value) - 1));
>>
>> ffs() only uses 'int', not int64_t.  ffsl() is not universally available.
>>
>>> +    }
>>> +    return value;
>>> +}
> 
> Not to mention that iterating one bit at a time is inefficient.  We
> already gave you several more efficient solutions; my favorite being:
> 
> static inline int64_t pow2floor(int64_t value)
> {
>     if (!is_power_of_2(value)) {
>         value = 0x8000000000000000ULL >> clz64(value);
>     }
>     return value;
> }
> 
> since clz64() is already part of qemu sources.
> 
I will fix it