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Re: [Qemu-devel] [PATCH v2] exec: Fix non-power-of-2 sized accesses
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From: |
Richard Henderson |
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Subject: |
Re: [Qemu-devel] [PATCH v2] exec: Fix non-power-of-2 sized accesses |
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Date: |
Fri, 16 Aug 2013 12:46:03 -0700 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130805 Thunderbird/17.0.8 |
On 08/16/2013 08:37 AM, Alex Williamson wrote:
> On Fri, 2013-08-16 at 08:27 -0700, Richard Henderson wrote:
>> On 08/16/2013 05:50 AM, Alex Williamson wrote:
>>> + /* Size must be a power of 2 */
>>> + if (l & (l - 1)) {
>>> + while (l & (access_size_max - 1)) {
>>> + access_size_max >>= 1;
>>> + }
>>> + }
>>> +
>>
>> Why the loop at all? x & -x extracts the lsb of x.
>
> l = 5, we want 4, not 1. Thanks,
It still doesn't require a loop.
l = 1 << (31 - clz32(l));
r~